Materials

Editorial

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4 pages, 183 KiB

Open AccessEditorial

Special Issue: Zinc Oxide Nanostructures: Synthesis and Characterization

by Sotirios Baskoutas

Department of Materials Science, University of Patras, 26500 Patras, Greece

Materials 2018, 11(6), 873; https://doi.org/10.3390/ma11060873 - 23 May 2018

Cited by 24 | Viewed by 4815

Abstract

Zinc oxide (ZnO) is a wide band gap semiconductor with an energy gap of 3.37 eV at room temperature. It has been used considerably for its catalytic, electrical, optoelectronic, and photochemical properties. ZnO nanomaterials, such as quantum dots, nanorods, and nanowires, have been [...] Read more.

Zinc oxide (ZnO) is a wide band gap semiconductor with an energy gap of 3.37 eV at room temperature. It has been used considerably for its catalytic, electrical, optoelectronic, and photochemical properties. ZnO nanomaterials, such as quantum dots, nanorods, and nanowires, have been intensively investigated for their important properties. Many methods have been described in the literature for the production of ZnO nanostructures, such as laser ablation, hydrothermal methods, electrochemical deposition, sol–gel methods, Chemical Vapour Deposition, molecular beam epitaxy, the common thermal evaporation method, and the soft chemical solution method. The present Special Issue is devoted to the Synthesis and Characterization of ZnO nanostructures with novel technological applications. Full article

(This article belongs to the Special Issue Zinc Oxide Nanostructures: Synthesis and Characterization)

Research

Jump to: Editorial, Review

13 pages, 8525 KiB

Open AccessFeature PaperArticle

Fully Ab-Initio Determination of the Thermoelectric Properties of Half-Heusler NiTiSn: Crucial Role of Interstitial Ni Defects

by Alexandre Berche

and Philippe Jund^*

Institut Charles Gerhardt Montpellier (ICGM), Centre National de la Recherche Scientifique (CNRS), Université de Montpellier, Ecole Nationale Supérieure de Chimie de Montpellier, UMR 5253, Montpellier, France

Materials 2018, 11(6), 868; https://doi.org/10.3390/ma11060868 - 23 May 2018

Cited by 32 | Viewed by 4483

Abstract

For thermoelectric applications, ab initio methods generally fail to predict the transport properties of the materials because of their inability to predict properly the carrier concentrations that control the electronic properties. In this work, a methodology to fill in this gap is applied [...] Read more.

For thermoelectric applications, ab initio methods generally fail to predict the transport properties of the materials because of their inability to predict properly the carrier concentrations that control the electronic properties. In this work, a methodology to fill in this gap is applied on the NiTiSn half Heusler phase. For that, we show that the main defects act as donor of electrons and are responsible of the electronic properties of the material. Indeed, the presence of Ni_i interstitial defects explains the experimental valence band spectrum and its associated band gap reported in the literature. Moreover, combining the DOS of the solid solutions with the determination of the energy of formation of charged defects, we show that Ni_i defects are also responsible of the measured carrier concentration in experimentally supposed “pure” NiTiSn compounds. Subsequently the thermoelectric properties of NiTiSn can be calculated using a fully ab initio description and an overall correct agreement with experiments is obtained. This methodology can be extended to predict the result of extrinsic doping and thus to select the most efficient dopant for specific thermoelectric applications. Full article

(This article belongs to the Special Issue Half-Heusler, Silicide and Zintl-type Thermoelectric Materials)

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17 pages, 925 KiB

Open AccessArticle

Extreme Ultraviolet to Visible Dispersed Single Photon Detection for Highly Sensitive Sensing of Fundamental Processes in Diverse Samples

by Andreas Hans^*, Philipp Schmidt, Christian Ozga, Gregor Hartmann, Xaver Holzapfel, Arno Ehresmann

and André Knie^*

Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Straße 40, 34305 Kassel, Germany

Materials 2018, 11(6), 869; https://doi.org/10.3390/ma11060869 - 23 May 2018

Cited by 24 | Viewed by 4540

Abstract

The detection of a single photon is the most sensitive method for sensing of photon emission. A common technique for single photon detection uses microchannel plate arrays combined with photocathodes and position sensitive anodes. Here, we report on the combination of such detectors [...] Read more.

The detection of a single photon is the most sensitive method for sensing of photon emission. A common technique for single photon detection uses microchannel plate arrays combined with photocathodes and position sensitive anodes. Here, we report on the combination of such detectors with grating diffraction spectrometers, constituting a low-noise wavelength resolving photon spectroscopy apparatus with versatile applicability. We recapitulate the operation principle of such detectors and present the details of the experimental set-up, which we use to investigate fundamental mechanisms in atomic and molecular systems after excitation with tuneable synchrotron radiation. Extensions for time and polarization resolved measurements are described and examples of recent applications in current research are given. Full article

(This article belongs to the Special Issue Fluorescent Sensors for Selective Detection)

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9 pages, 1712 KiB

Open AccessArticle

Control of the Nucleation Density of Molybdenum Disulfide in Large-Scale Synthesis Using Chemical Vapor Deposition

by Haitao Xu¹, Weipeng Zhou¹, Xiaowu Zheng¹, Jiayao Huang¹, Xiliang Feng¹, Li Ye¹, Guanjin Xu¹ and Fang Lin^1,2,*

¹ College of Electronic Engineering, South China Agricultural University, Guangzhou 510642, China

² State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China

Materials 2018, 11(6), 870; https://doi.org/10.3390/ma11060870 - 23 May 2018

Cited by 20 | Viewed by 5229

Abstract

Atmospheric pressure chemical vapor deposition (CVD) is presently a promising approach for preparing two-dimensional (2D) MoS₂ crystals at high temperatures on SiO₂/Si substrates. In this work, we propose an improved CVD method without hydrogen, which can increase formula flexibility by [...] Read more.

Atmospheric pressure chemical vapor deposition (CVD) is presently a promising approach for preparing two-dimensional (2D) MoS₂ crystals at high temperatures on SiO₂/Si substrates. In this work, we propose an improved CVD method without hydrogen, which can increase formula flexibility by controlling the heating temperature of MoO₃ powder and sulfur powder. The results show that the size and coverage of MoS₂ domains vary largely, from discrete triangles to continuous film, on substrate. We find that the formation of MoS₂ domains is dependent on the nucleation density of MoS₂. Laminar flow theory is employed to elucidate the cause of the different shapes of MoS₂ domains. The distribution of carrier gas speeds at the substrate surface leads to a change of nucleation density and a variation of domain morphology. Thus, nucleation density and domain morphology can be actively controlled by adjusting the carrier gas flow rate in the experimental system. These results are of significance for understanding the growth regulation of 2D MoS₂ crystals. Full article

(This article belongs to the Special Issue Recent Advances in 2D Nanomaterials)

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17 pages, 17327 KiB

Open AccessArticle

Effect of PCM on the Hydration Process of Cement-Based Mixtures: A Novel Thermo-Mechanical Investigation

by Claudia Fabiani¹, Anna Laura Pisello^1,2,*

, Antonella D’Alessandro³

, Filippo Ubertini³

, Luisa F. Cabeza⁴

and Franco Cotana^1,2

¹ CIRIAF—Interuniversity Research Center, University of Perugia, Via G. Duranti 63, 06125 Perugia, Italy

² Department of Engineering, University of Perugia, Via G. Duranti 93, 06125 Perugia, Italy

³ Department of Civil and Environmental Engineering, University of Perugia, Via G. Duranti 93, 06125 Perugia, Italy

⁴ GREiA Research Group, INSPIRES Research Centre, Universitat de Lleida, Pere de Cabrera s/n, 25001 Lleida, Spain

Materials 2018, 11(6), 871; https://doi.org/10.3390/ma11060871 - 23 May 2018

Cited by 23 | Viewed by 4492

Abstract

The use of Phase Change Material (PCM) for improving building indoor thermal comfort and energy saving has been largely investigated in the literature in recent years, thus confirming PCM’s capability to reduce indoor thermal fluctuation in both summer and winter conditions, according to [...] Read more.

The use of Phase Change Material (PCM) for improving building indoor thermal comfort and energy saving has been largely investigated in the literature in recent years, thus confirming PCM’s capability to reduce indoor thermal fluctuation in both summer and winter conditions, according to their melting temperature and operation boundaries. Further to that, the present paper aims at investigating an innovative use of PCM for absorbing heat released by cement during its curing process, which typically contributes to micro-cracking of massive concrete elements, therefore compromising their mechanical performance during their service life. The experiments carried out in this work showed how PCM, even in small quantities (i.e., up to 1% in weight of cement) plays a non-negligible benefit in reducing differential thermal increases between core and surface and therefore mechanical stresses originating from differential thermal expansion, as demonstrated by thermal monitoring of cement-based cubes. Both PCM types analyzed in the study (with melting temperatures at 18 and 25

^{\circ}

C) were properly dispersed in the mix and were shown to be able to reduce the internal temperature of the cement paste by several degrees, i.e., around 5

^{\circ}

C. Additionally, such small amount of PCM produced a reduction of the final density of the composite and an increase of the characteristic compressive strength with respect to the plain recipe. Full article

(This article belongs to the Special Issue Recent Advances in Smart Materials for the Built Environment)

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13 pages, 5497 KiB

Open AccessArticle

Hot Deformation Behavior of a Ti-40Al-10V Alloy with Quenching-Tempering Microstructure

by Liang Cheng^1,*

, Yi Chen^1,2, Guang Yang³, Li Xie¹, Jiangtao Wang¹, Yalin Lu¹ and Hongchao Kou⁴

¹ School of Materials and Engineering, Jiangsu University of Technology, Changzhou 213001, China

² Sunnywell (China) New Material Technology Co., Ltd., Changzhou 213000, China

³ College of Mechanical and Electrical Engineering, Shaanxi University of Science and Technology, Xi’an 710021, China

⁴ State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China

Materials 2018, 11(6), 872; https://doi.org/10.3390/ma11060872 - 23 May 2018

Viewed by 2884

Abstract

In this study, a Ti-40Al-10V alloy with quenching-tempering microstructure was prepared and was characterized by ultra-large β/B2 grains and submicrocrystalline γ laths within it. A definite Kurdjumov-Sachs orientation was identified between the β/B2 and γ phase. Isothermal compression tests were performed to examine [...] Read more.

In this study, a Ti-40Al-10V alloy with quenching-tempering microstructure was prepared and was characterized by ultra-large β/B2 grains and submicrocrystalline γ laths within it. A definite Kurdjumov-Sachs orientation was identified between the β/B2 and γ phase. Isothermal compression tests were performed to examine the hot deformation behavior at various temperatures and strain rates. Based on the hyperbolic-sine equation, the deformation kinetics of the alloy were characterized by unexpectedly high activation energy (384 kJ/mol) and low stress exponent (2.25). For all the deformed samples, continuous dynamic recrystallization intensively occurred in the β matrix, accompanied by the simultaneous rotation of the γ laths. Moreover, a preferential orientation of <100>_β and <111>_γ parallel to the compression axis was observed for β and γ phase, respectively. With the decreasing strain rates, the grain boundary/interface sliding gradually became prominent, which resulted in some superplastic deformation features, e.g., intensive strain-induced grain growth and interface migration, enhancing “wetting” of the γ grain boundaries, continuous weakening/vanishing of the local texture, etc. Meanwhile, the temperature played an insignificant role in the hot deformation behavior. The deformation mechanism was discussed in detail based on the microstructural observations and deformation kinetics. Full article

(This article belongs to the Section Advanced Materials Characterization)

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18 pages, 6048 KiB

Open AccessArticle

The Effect of Dynamic Recrystallization on Monotonic and Cyclic Behaviour of Al-Cu-Mg Alloy

by Adam Tomczyk^*, Andrzej Seweryn and Małgorzata Grądzka-Dahlke

Faculty of Mechanical Engineering, Białystok University of Technology, Wiejska 45C Str., 15-351 Białystok, Poland

Materials 2018, 11(6), 874; https://doi.org/10.3390/ma11060874 - 23 May 2018

Cited by 17 | Viewed by 4320

Abstract

The paper presents an investigation that was conducted to determine the possibility of the occurrence of the process of dynamic recrystallization in 2024 alloy during monotonic tensile and creep tests at the elevated temperatures of 100 °C, 200 °C, and 300 °C. As-extruded [...] Read more.

The paper presents an investigation that was conducted to determine the possibility of the occurrence of the process of dynamic recrystallization in 2024 alloy during monotonic tensile and creep tests at the elevated temperatures of 100 °C, 200 °C, and 300 °C. As-extruded material was subjected to creep process with constant force at elevated temperatures, until two varying degrees of deformation were reached. After cooling at ambient temperature, the pre-deformed material was subjected to monotonic and fatigue tests as well as metallographic analysis. The process of dynamic recrystallization was determined in monotonic tests to occur at low strain rate (0.0015/s) only at the temperature of 300 °C. However, in the creep tests, this process occurred with varying efficiency, both during creep at 200 °C and 300 °C. Dynamic recrystallization was indicated to have a significant influence on the monotonic and cyclic properties of the material. Full article

(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)

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18 pages, 8684 KiB

Open AccessArticle

Microstructures Evolution and Micromechanics Features of Ni-Cr-Si Coatings Deposited on Copper by Laser Cladding

by Peilei Zhang^1,2,*

, Mingchuan Li^1,2 and Zhishui Yu^1,2

¹ School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620, China

² Shanghai Collaborative Innovation Center of Laser Advanced Manufacturing, Shanghai University of Engineering Science, Shanghai 201620, China

Materials 2018, 11(6), 875; https://doi.org/10.3390/ma11060875 - 23 May 2018

Cited by 20 | Viewed by 4516

Abstract

Three Ni-Cr-Si coatings were synthesized on the surface of copper by laser cladding. The microstructures of the coatings were characterized by optical microscopy (OM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS). According to the analysis results [...] Read more.

Three Ni-Cr-Si coatings were synthesized on the surface of copper by laser cladding. The microstructures of the coatings were characterized by optical microscopy (OM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS). According to the analysis results of phase compositions, Gibbs free energy change and microstructures, the phases of three coatings appeared were Cr₃Si+γ-Ni+Cu_ss (Coating 1, Ni-26Cr-29Si), Cr₆Ni₁₆Si₇+Ni₂Si+Cu_ss (Coating 2, Ni-10Cr-30Si) and Cr₃Ni₅Si₂+Cr₂Ni₃+Cu_ss (Coating 3, Ni-29Cr-16Si). The crystal growth in the solidification process was analyzed with a modified model, which is a combination of Kurz-Giovanola-Trivedi (KGT) and Lipton-Kurz-Trivedi (LKT) models. The dendrite tip undercooling in Coating 2 was higher than those of Coating 1 and Coating 3. Well-developed dendrites were found in Coating 2. A modification of Hunt’s model was adopted to describe the morphological differences in the three coatings. The results show that Coating 1 was in the equiaxed dendrite region, while Coatings 2 and 3 were in the columnar dendrite region. The average friction coefficients of the three coatings were 0.45, 0.5 and 0.4, respectively. Obvious plastic deformation could be found in the subsurface zone of Coatings 2 and 3. Full article

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8 pages, 3930 KiB

Open AccessArticle

Porous Structure Properties of Andropogon gerardi Derived Carbon Materials

by Natalia Howaniec^1,*

and Adam Smoliński²

¹ Department of Energy Saving and Air Protection, Central Mining Institute, Pl. Gwarków 1, 40-166 Katowice, Poland

² Central Mining Institute, Pl. Gwarków 1, 40-166 Katowice, Poland

Materials 2018, 11(6), 876; https://doi.org/10.3390/ma11060876 - 24 May 2018

Cited by 9 | Viewed by 3334

Abstract

Various carbonaceous materials are valuable resources for thermochemical conversion processes and for production of materials of proven sorption properties, useful in environmental applications for gaseous and liquid media treatment. In both cases, the parameters of the porous structure of carbon materials are decisive [...] Read more.

Various carbonaceous materials are valuable resources for thermochemical conversion processes and for production of materials of proven sorption properties, useful in environmental applications for gaseous and liquid media treatment. In both cases, the parameters of the porous structure of carbon materials are decisive in terms of their physical and mechanical properties, having direct effects on heat and mass transport as well as on sorption capacity and selectivity. The physical activation of carbon materials produced from various precursors is widely discussed in literature. In this respect, the effects of temperature and partial oxidation of carbonaceous materials with steam or carbon dioxide are mostly considered. The reports on the effects of pressure on the development of porous structures of carbon materials are, however, extremely limited, especially when biomass as a precursor is concerned. In this paper, the results of an experimental study on the effects of pressure in the range of 1–4 MPa on the specific surface area, the total pore volume, average pore diameter, and microporosity of carbon materials prepared with the use of Andropogon gerardi biomass as a precursor are presented. The tested samples were prepared at the temperature of 1000 °C under an inert gas atmosphere in the high-pressure thermogravimetric analyzer. The most developed porous structure was reported for carbon materials produced under 3 MPa. The highest volume of narrow micropores was characteristic for materials carbonized under 2 MPa. Full article

(This article belongs to the Collection Advanced Biomass-Derived Carbon Materials)

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16 pages, 11634 KiB

Open AccessArticle

Nitrogen Oxides Mitigation Efficiency of Cementitious Materials Incorporated with TiO₂

by Inkyu Rhee^1,*, Jun-Seok Lee², Jong Beom Kim³ and Jong-Ho Kim³

¹ Department of Civil Engineering, Chonnam National University, Gwangju 61186, Korea

² Bio-Housing Institute, Chonnam National University, Gwangju 61186, Korea

³ School of Chemical Engineering, Chonnam National University, Gwangju 61186, Korea

Materials 2018, 11(6), 877; https://doi.org/10.3390/ma11060877 - 24 May 2018

Cited by 26 | Viewed by 4043

Abstract

We explored the photocatalytic capacities of cementitious materials (cement paste and mortar) incorporating titanium dioxide (TiO₂). P-25 is a commercial TiO₂ preparation which, if incorporated into large civil buildings, is extremely expensive. It is essential to produce low-cost TiO₂ [...] Read more.

We explored the photocatalytic capacities of cementitious materials (cement paste and mortar) incorporating titanium dioxide (TiO₂). P-25 is a commercial TiO₂ preparation which, if incorporated into large civil buildings, is extremely expensive. It is essential to produce low-cost TiO₂. A cheap anatase form of TiO₂ powder, NP-400, manufactured under relatively low burning temperature, was considered in this paper. Addition of NP-400 to 0, 5, 10, and 20 wt % did not significantly affect the compressive strengths of mortar or cement paste. However, the compressive strengths of P-25-containing specimens were more consistent than those of NP-400-containing materials. The nitrogen oxide (NO) removal efficiencies by mortar with 5 and 10 wt % TiO₂ were similar at ca. 14–16%; the removal efficiency by mortar with 20 wt % NP-400 was ca. 70%. Although the NP-400 cluster size was almost halved by ultrasonication, NO removal efficiency was not enhanced. Removal was enhanced by the presence of accessible surface area: NP-400 dispersed in these surfaces readily adsorbed NO, aided by the large surface areas of the top and bottom faces. Scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM–EDX) confirmed that NP-400 tended to sink when added to cement, fine aggregates, and water because the true densities of P-25, NP-400, and cement powder differed (3.41, 3.70, and 3.15 g/mL). The true density of NP-400 was thus the highest of all ingredients. The relatively low apparent density of P-25 compared to that of NP-400 was associated with a more bulky distribution of P-25 within cementitious materials. Nevertheless, NP-400 could be a viable alternative to the definitive product, P-25. Full article

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10 pages, 4463 KiB

Open AccessArticle

Fabrication of α-Fe/Fe₃C/Woodceramic Nanocomposite with Its Improved Microwave Absorption and Mechanical Properties

by Weihong Zhou^1,*, Yunshui Yu¹, Xueliang Xiong² and Sicong Zhou¹

¹ College of Material Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, China

² Changsha Research Institute of Mining and Metallurgy Limited Company, Changsha 410004, China

Materials 2018, 11(6), 878; https://doi.org/10.3390/ma11060878 - 24 May 2018

Cited by 24 | Viewed by 4450

Abstract

Furan resin and fir powder pretreated by FeCl₃ and aqueous ammonia solution were used to fabricate α-Fe/Fe₃C/woodceramic nanocomposite. The bands of the pretreated wood powder were characterized by Fourier transform infrared spectroscopy (FTIR). The structural characterization of the nanocomposites was [...] Read more.

Furan resin and fir powder pretreated by FeCl₃ and aqueous ammonia solution were used to fabricate α-Fe/Fe₃C/woodceramic nanocomposite. The bands of the pretreated wood powder were characterized by Fourier transform infrared spectroscopy (FTIR). The structural characterization of the nanocomposites was performed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The microwave absorption of the nanocomposites was measured by a vector network analyzer in the range of 2–18 GHz. The mechanical properties of the composites were also investigated. XRD and SEM results show that the α-Fe and Fe₃C nanoparticles are in-situ generated and disperse in the matrix of the woodceramic. The diameters of these nanoparticles increase with the increasing of concentration of FeCl₃ solution. The experimental results show that both the complex permittivity and the complex permeability of α-Fe/Fe₃C/woodceramic nanocomposites increase as the concentration of FeCl₃ solution increases. The composites pretreated with 0.60 mol·L⁻¹ FeCl₃ have the best absorption properties. The maximum value of reflection loss (RL) at 3 mm thickness reaches −25.60 dB at 10.16 GHz and the bandwidth below −10 dB is about 2.5 GHz. Compared to woodceramic, the bending strength and compressive strength of α-Fe/Fe₃C/woodceramic nanocomposites increase by 22.5% and 18.7% at most, respectively. Full article

(This article belongs to the Collection Advanced Biomass-Derived Carbon Materials)

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15 pages, 4277 KiB

Open AccessArticle

Experimental Investigation of Principal Residual Stress and Fatigue Performance for Turned Nickel-Based Superalloy Inconel 718

by Yang Hua^1,2 and Zhanqiang Liu^1,2,*

¹ Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE, School of Mechanical Engineering, Shandong University, Jinan 250061, China

² Key National Demonstration Center for Experimental Mechanical Engineering Education, Shandong University, Jinan 250061, China

Materials 2018, 11(6), 879; https://doi.org/10.3390/ma11060879 - 24 May 2018

Cited by 51 | Viewed by 4266

Abstract

Residual stresses of turned Inconel 718 surface along its axial and circumferential directions affect the fatigue performance of machined components. However, it has not been clear that the axial and circumferential directions are the principle residual stress direction. The direction of the maximum [...] Read more.

Residual stresses of turned Inconel 718 surface along its axial and circumferential directions affect the fatigue performance of machined components. However, it has not been clear that the axial and circumferential directions are the principle residual stress direction. The direction of the maximum principal residual stress is crucial for the machined component service life. The present work aims to focuses on determining the direction and magnitude of principal residual stress and investigating its influence on fatigue performance of turned Inconel 718. The turning experimental results show that the principal residual stress magnitude is much higher than surface residual stress. In addition, both the principal residual stress and surface residual stress increase significantly as the feed rate increases. The fatigue test results show that the direction of the maximum principal residual stress increased by 7.4%, while the fatigue life decreased by 39.4%. The maximum principal residual stress magnitude diminished by 17.9%, whereas the fatigue life increased by 83.6%. The maximum principal residual stress has a preponderant influence on fatigue performance as compared to the surface residual stress. The maximum principal residual stress can be considered as a prime indicator for evaluation of the residual stress influence on fatigue performance of turned Inconel 718. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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12 pages, 6043 KiB

Open AccessArticle

Polymerizable Microsphere-Induced High Mechanical Strength of Hydrogel Composed of Acrylamide

by Zhiyong Wang, Meiqin Lin^*

, Menghan Wang, Xia Song, Chuqiao Zhang, Zhaoxia Dong, Juan Zhang and Zihao Yang

Research Institute of Enhanced Oil Recovery, China University of Petroleum, Beijing 102249, China

Materials 2018, 11(6), 880; https://doi.org/10.3390/ma11060880 - 24 May 2018

Cited by 13 | Viewed by 3796

Abstract

Polymerizable microspheres are introduced into acrylamide to prepare the high mechanical strength hydrogels with a novel three-dimensional pore structure. Rheological properties, compressive stress–strain, tensile property, and compression strength of three different types of hydrogels were investigated. Moreover, a scanning electron microscope (SEM) was [...] Read more.

Polymerizable microspheres are introduced into acrylamide to prepare the high mechanical strength hydrogels with a novel three-dimensional pore structure. Rheological properties, compressive stress–strain, tensile property, and compression strength of three different types of hydrogels were investigated. Moreover, a scanning electron microscope (SEM) was adopted to observe the three-dimension network structure of three different types of hydrogels. The test results illustrated that viscous moduli (G″) and elastic moduli (G′) of a hydrogel containing polymerizable microspheres (P) reached maximum values, compared to the normal hydrogel (N) and the composite hydrogel containing ordinary microspheres (O). When the hydrogels were squeezed, the N was easily fractured under high strain (99%), whereas the P was not broken, and quickly recovered its initial morphology after the release of load. The P showed excellent tensile properties, with an elongation at break up to 90% and a tensile strength greater than 220 g. The compression strength of the N was 100.44 kPa·m⁻¹, while the resulting strength of P was enhanced to be 248.00 kPa·m⁻¹. Therefore, the various performances of N were improved by adding polymerizable microspheres. In addition, the SEM images indicated that N has a general three-dimensional network structure; the conventional network structure did not exist in the P, which has a novel three-dimensional pore structure in the spherical projection and very dense channels, which led to the compaction of the space between the three-dimensional pore network layers and reduced the flowing of free water wrapped in the network. Therefore, the mechanical strength of hydrogel was enhanced. Full article

(This article belongs to the Section Advanced Composites)

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13 pages, 2714 KiB

Open AccessArticle

Rapid Production of Mn₃O₄/rGO as an Efficient Electrode Material for Supercapacitor by Flame Plasma

by Yang Zhou¹, Lei Guo^2,*

, Wei Shi², Xuefeng Zou¹, Bin Xiang^1,3,* and Shaohua Xing^4,*

¹ School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China

² School of Material and Chemical Engineering, Tongren University, Tongren 554300, China

³ National-municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing 400044, China

⁴ State Key Laboratory for Marine Corrosion and Protection, Luoyang Ship Material Research Institute (LSMRI), Qingdao 26623, China

Materials 2018, 11(6), 881; https://doi.org/10.3390/ma11060881 - 24 May 2018

Cited by 55 | Viewed by 5297

Abstract

Benefiting from good ion accessibility and high electrical conductivity, graphene-based material as electrodes show promising electrochemical performance in energy storage systems. In this study, a novel strategy is devised to prepare binder-free Mn₃O₄-reduced graphene oxide (Mn₃O₄ [...] Read more.

Benefiting from good ion accessibility and high electrical conductivity, graphene-based material as electrodes show promising electrochemical performance in energy storage systems. In this study, a novel strategy is devised to prepare binder-free Mn₃O₄-reduced graphene oxide (Mn₃O₄/rGO) electrodes. Well-dispersed and homogeneous Mn₃O₄ nanosheets are grown on graphene layers through a facile chemical co-precipitation process and subsequent flame procedure. This obtained Mn₃O₄/rGO nanostructures exhibit excellent gravimetric specific capacitance of 342.5 F g⁻¹ at current density of 1 A g⁻¹ and remarkable cycling stability of 85.47% capacitance retention under 10,000 extreme charge/discharge cycles at large current density. Furthermore, an asymmetric supercapacitor assembled using Mn₃O₄/rGO and activated graphene (AG) delivers a high energy density of 27.41 Wh kg⁻¹ and a maximum power density of 8 kW kg⁻¹. The material synthesis strategy presented in this study is facile, rapid and simple, which would give an insight into potential strategies for large-scale applications of metal oxide/graphene and hold tremendous promise for power storage applications. Full article

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11 pages, 3787 KiB

Open AccessArticle

Oxidation Resistance and Wetting Behavior of MgO-C Refractories: Effect of Carbon Content

by Zhaoyang Liu

, Jingkun Yu^*, Xin Yang, Endong Jin and Lei Yuan

School of Metallurgy, Northeastern University, Shenyang 110819, China

Materials 2018, 11(6), 883; https://doi.org/10.3390/ma11060883 - 24 May 2018

Cited by 47 | Viewed by 5357

Abstract

Various carbon contents in the MgO-C refractory were studied with respect to the oxidation resistance and the wetting behavior with slag. The bulk density, apparent porosity, cold crushing strength, oxidation rate, and mass loss rate of the fired MgO-C refractories with various carbon [...] Read more.

Various carbon contents in the MgO-C refractory were studied with respect to the oxidation resistance and the wetting behavior with slag. The bulk density, apparent porosity, cold crushing strength, oxidation rate, and mass loss rate of the fired MgO-C refractories with various carbon contents were measured and compared. The wetting and penetration behavior of the cured MgO-C refractory with the molten slag were observed in-situ. The contact angle and the shape parameters of molten slag, including the apparent radius, height, and volume were compared. The results showed that the regenerated MgO effectively restrained the carbon oxidation in the MgO-C refractory, which was more evident at the low carbon content refractory. The contact angle between the MgO-C refractory and the molten slag increased as the carbon content increased. The increased contact angle decreased the penetration of the molten slag. Full article

(This article belongs to the Special Issue High Temperature Ceramic Materials)

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10 pages, 3441 KiB

Open AccessArticle

Large Area Synthesis of Vertical Aligned Metal Oxide Nanosheets by Thermal Oxidation of Stainless Steel Mesh and Foil

by Fan Wu¹, Chen Wang¹, Marvin H. Wu², Kizhanipuram Vinodgopal^3,* and Gui-Ping Dai^1,3,4,5,*

¹ School of Resources Environmental & Chemical Engineering, Nanchang University, Nanchang 330031, China

² Department of Physics, North Carolina Central University, Durham, NC 27707, USA

³ Department of Chemistry and Biochemistry, North Carolina Central University, Durham, NC 27707, USA

⁴ Institute for Advanced Study, Nanchang University, Nanchang 330031, China

⁵ Key Laboratory of Poyang Lake Environment and Resource Utilization, Nanchang University, Ministry of Education, Nanchang 330031, China

Materials 2018, 11(6), 884; https://doi.org/10.3390/ma11060884 - 25 May 2018

Cited by 12 | Viewed by 4554

Abstract

We report here the synthesis of metal oxide nanosheets (MONs) directly grown on stainless steel substrates by thermal oxidation in the presence of trace amounts of water. The morphology and microstructure of MONs were characterized by scanning electron microscopy (SEM), transmission electron microscopy [...] Read more.

We report here the synthesis of metal oxide nanosheets (MONs) directly grown on stainless steel substrates by thermal oxidation in the presence of trace amounts of water. The morphology and microstructure of MONs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and atomic force microscopy (AFM). The composition of MONs was determined by the energy dispersive system and X-ray diffraction patterns. The results showed that the as-synthesized MONs were ultrathin, vertically aligned, and mostly transparent. They were polycrystalline and were composed primarily of Cr₂O₃ and (Fe, Mn)₃O₄. The optimal condition to synthesize the MONs with an optimal ultra-high surface atom ratio were determined by varying the temperature and time required for the growth of the MONs. It was found that the lateral size of MONs gradually increases as the temperature rises from 1000 to 1100 °C. An optimal temperature of 1100 °C is obtained in terms of the growth density, size and transparency degree growth morphology, and quality. The structure of MONs changes from two-dimensional to three-dimensional networks when the synthesis time is prolonged to more than 1 h. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

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13 pages, 2541 KiB

Open AccessArticle

Surface Functionalization of Polyethylene Granules by Treatment with Low-Pressure Air Plasma

by Hana Šourková^1,2

, Gregor Primc^1,3

and Petr Špatenka^1,*

¹ Faculty of Mechanical Engineering, Department of Materials Engineering, Center of Advanced Aerospace Technology, Czech Technical University in Prague, Karlovo náměstí 13, 121 35 Praha 2, Czech Republic

² Faculty of Mechatronics, Informatics and Interdisciplinary Studies, Technical University of Liberec, Studentská 1402/2, 461 17 Liberec 1, Czech Republic

³ Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia

Materials 2018, 11(6), 885; https://doi.org/10.3390/ma11060885 - 25 May 2018

Cited by 22 | Viewed by 4373

Abstract

Polyethylene granules of diameter 2 mm were treated with a low-pressure weakly ionized air plasma created in a metallic chamber by a pulsed microwave discharge of pulse duration 180 μs and duty cycle 70%. Optical emission spectroscopy showed rich bands of neutral nitrogen [...] Read more.

Polyethylene granules of diameter 2 mm were treated with a low-pressure weakly ionized air plasma created in a metallic chamber by a pulsed microwave discharge of pulse duration 180 μs and duty cycle 70%. Optical emission spectroscopy showed rich bands of neutral nitrogen molecules and weak O-atom transitions, but the emission from N atoms was below the detection limit. The density of O atoms in the plasma above the samples was measured with a cobalt catalytic probe and exhibited a broad peak at the pressure of 80 Pa, where it was about 2.3 × 10²¹ m⁻³. The samples were characterized by X-ray photoelectron spectroscopy. Survey spectra showed oxygen on the surface, while the nitrogen concentration remained below the detection limit for all conditions. The high-resolution C1s peaks revealed formation of various functional groups rather independently from treatment parameters. The results were explained by extensive dissociation of oxygen molecules in the gaseous plasma and negligible flux of N atoms on the polymer surface. Full article

(This article belongs to the Special Issue Surface Modification to Improve Properties of Materials)

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10 pages, 629 KiB

Open AccessArticle

Influence of the Regime of Electropulsing-Assisted Machining on the Plastic Deformation of the Layer Being Cut

by Saqib Hameed¹, Hernán A. González Rojas¹

, José I. Perat Benavides²

, Amelia Nápoles Alberro¹

and Antonio J. Sánchez Egea^3,4,*

¹ Department of Mechanical Engineering (EPSEVG), Universitat Politécnica de Catalunya, Av. de Víctor Balaguer Vilanova i la Geltrú, 08800 Barcelona, Spain

² Department of Electrical Engineering (EPSEVG), GAECE group, Universitat Politécnica de Catalunya, Av. de Víctor Balaguer Vilanova i la Geltrú, 08800 Barcelona, Spain

³ Department of Mechanical and Metallurgical Engineering, Pontificia Universidad Catolica de Chile, Av. Vicuña Mackenna 4860, Region Metropolitana 7820436, Chile

⁴ Department of Mechanical Engineering, Aeronautics Advanced Manufacturing Center (CFAA), Faculty of Engineering of Bilbao, Alameda de Urquijo s/n, 48013 Bilbao, Spain

Materials 2018, 11(6), 886; https://doi.org/10.3390/ma11060886 - 25 May 2018

Cited by 30 | Viewed by 4456

Abstract

In this article, the influence of electropulsing on the machinability of steel S235 and aluminium 6060 has been studied during conventional and electropulsing-assisted turning processes. The machinability indices such as chip compression ratio

ξ

, shear plane angle

ϕ

and specific cutting energy [...] Read more.

In this article, the influence of electropulsing on the machinability of steel S235 and aluminium 6060 has been studied during conventional and electropulsing-assisted turning processes. The machinability indices such as chip compression ratio

ξ

, shear plane angle

ϕ

and specific cutting energy (SCE) are investigated by using different cutting parameters such as cutting speed, cutting feed and depth of cut during electrically-assisted turning process. The results and analysis of this work indicated that the electrically-assisted turning process improves the machinability of steel S235, whereas the machinability of aluminium 6060 gets worse. Finally, due to electropluses (EPs), the chip compression ratio

ξ

increases with the increase in cutting speed during turning of aluminium 6060 and the SCE decreases during turning of steel S235. Full article

(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)

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19 pages, 3690 KiB

Open AccessFeature PaperArticle

CO₂ Capture with Mesoporous Silicas Modified with Amines by Double Functionalization: Assessment of Adsorption/Desorption Cycles

by Kléver Santiago Sánchez-Zambrano¹, Lairana Lima Duarte¹, Débora Aline Soares Maia¹, Enrique Vilarrasa-García¹

, Moisés Bastos-Neto¹, Enrique Rodríguez-Castellón²

and Diana Cristina Silva de Azevedo^1,*

¹ Grupo de Pesquisa em Separações por Adsorção, Department of Chemical Engineering, Universidade Federal do Ceará, Campus do Pici, Fortaleza 60455760, CE, Brazil

² Department of Inorganic Chemistry, Crystallography and Mineralogy, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain

Materials 2018, 11(6), 887; https://doi.org/10.3390/ma11060887 - 25 May 2018

Cited by 46 | Viewed by 5944

Abstract

CO₂ adsorption on mesoporous silica modified with amine by double functionalization was studied. Adsorption microcalorimetry was used in order to investigate the influence of increasing the nitrogen surface density on double functionalized materials with respect to the only grafted materials. The distribution [...] Read more.

CO₂ adsorption on mesoporous silica modified with amine by double functionalization was studied. Adsorption microcalorimetry was used in order to investigate the influence of increasing the nitrogen surface density on double functionalized materials with respect to the only grafted materials. The distribution of sites and the rate-controlling mechanism of adsorption were evaluated. A Tian Calvet microcalorimeter coupled to a manometric setup was used to evaluate the energy distribution of adsorption sites and to calculate the thermokinetic parameters from the differential enthalpy curves. CO₂ and N₂ adsorption equilibrium isotherms at 50 and 75 °C were measured with a magnetic suspension balance, allowing for the computation of working capacity and selectivity at two temperatures. With these data, an Adsorbent Performance Indicator (API) was calculated and contrasted with other studied materials under the same conditions. The high values of API and selectivity confirmed that double functionalized mesoporous silica is a promising adsorbent for the post combustion process. The adsorption microcalorimetric study suggests a change in active sites distribution as the amine density increases. Maximum thermokinetic parameter suggests that physisorption on pores is the rate-controlling binding mechanism for the double-functionalized material. Full article

(This article belongs to the Special Issue Mesoporous Silica Catalysts)

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21 pages, 2719 KiB

Open AccessFeature PaperArticle

Effect of Graphene Flakes Modified by Dispersion in Surfactant Solutions on the Fluorescence Behaviour of Pyridoxine

by Rocío Mateos¹, Alba García-Zafra¹, Soledad Vera-López¹

, María Paz San Andrés¹

and Ana María Díez-Pascual^1,2,*

¹ Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Faculty of Sciences, Alcalá University, 28871 Alcalá de Henares, Madrid, Spain

² Institute of Chemistry Research, “Andrés M. del Río” (IQAR), University of Alcalá, Ctra. Madrid Barcelona, Km. 33.6, 28871 Alcalá de Henares, Madrid, Spain

Materials 2018, 11(6), 888; https://doi.org/10.3390/ma11060888 - 25 May 2018

Cited by 7 | Viewed by 4607

Abstract

The influence of graphene (G) dispersions in different types of surfactants (anionic, non-ionic, and cationic) on the fluorescence of vitamin B₆ (pyridoxine) was studied. Scanning electron microscopy (SEM) was used to evaluate the quality of the G dispersions via measuring their flake [...] Read more.

The influence of graphene (G) dispersions in different types of surfactants (anionic, non-ionic, and cationic) on the fluorescence of vitamin B₆ (pyridoxine) was studied. Scanning electron microscopy (SEM) was used to evaluate the quality of the G dispersions via measuring their flake thickness. The effect of surfactant type and concentration on the fluorescence intensity was analyzed, and fluorescence quenching effects were found for all of the systems. These turn out to be more intense with increasing both surfactant and G concentrations, albeit they do not depend on the G/surfactant weight ratio. For the same G concentration, the magnitude of the quenching follows the order: cationic > non-ionic ≥ anionic. The cationic surfactants, which strongly adsorb onto G via electrostatic attraction, are the most effective dispersing agents and they enable a stronger interaction with the zwitterionic form of the vitamin; the dispersing power improves with increasing the surfactant chain length. The fit of the experimental data to the Stern-Volmer equation suggests either a static or dynamic quenching mechanism for the dispersions in non-ionic surfactants, while those in ionic surfactants show a combined mechanism. The results that were obtained herein have been compared to those that were reported earlier for the quenching of another vitamin, riboflavin, to elucidate how the change in the vitamin structure influences the interactions with G in the surfactant dispersions. Full article

(This article belongs to the Special Issue Recent Advances in 2D Nanomaterials)

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15 pages, 3107 KiB

Open AccessArticle

Antibacterial, Hydrophilic Effect and Mechanical Properties of Orthodontic Resin Coated with UV-Responsive Photocatalyst

by Akira Kuroiwa¹

, Yoshiaki Nomura^2,*

, Tsuyoshi Ochiai^3,4,5

, Tomomi Sudo¹, Rie Nomoto⁶, Tohru Hayakawa⁶, Hiroyuki Kanzaki¹

, Yoshiki Nakamura¹ and Nobuhiro Hanada²

¹ Department of Orthodontics, Tsurumi University School of Dental Medicine, Yokohama 230-8501, Japan

² Department of Translational Research, Tsurumi University School of Dental Medicine, Yokohama 230-8501, Japan

³ Photocatalyst Group, Research and Development Department, Local Independent Administrative Agency Kanagawa Institute of industrial Science and TEChnology (KISTEC), 407 East Wing, Innovation Center Building, KSP, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan

⁴ Materials Analysis Group, Kawasaki Technical Support Department, KISTEC, Ground Floor East Wing, Innovation Center Building, KSP, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan

⁵ Photocatalysis International Research Center, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan

⁶ Department of Dental Engineering, Tsurumi University School of Dental Medicine, Yokohama 230-8501, Japan

Materials 2018, 11(6), 889; https://doi.org/10.3390/ma11060889 - 25 May 2018

Cited by 18 | Viewed by 5119

Abstract

Photocatalysts have multiple applications in air purifiers, paints, and self-cleaning coatings for medical devices such as catheters, as well as in the elimination of xenobiotics. In this study, a coating of a UV-responsive photocatalyst, titanium dioxide (TiO₂), was applied to an [...] Read more.

Photocatalysts have multiple applications in air purifiers, paints, and self-cleaning coatings for medical devices such as catheters, as well as in the elimination of xenobiotics. In this study, a coating of a UV-responsive photocatalyst, titanium dioxide (TiO₂), was applied to an orthodontic resin. The antibacterial activity on oral bacteria as well as hydrophilic properties and mechanical properties of the TiO₂-coated resin were investigated. ultraviolet A (UVA) (352 nm) light was used as the light source. Antibacterial activity was examined with or without irradiation. Measurements of early colonizers and cariogenic bacterial count, i.e., colony forming units (CFU), were performed after irradiation for different time durations. Hydrophilic properties were evaluated by water contact angle measurements. While, for the assessment of mechanical properties, flexural strength was measured by the three-point bending test. In the coat(+)light(+) samples the CFU were markedly decreased compared to the control samples. Water contact angle of the coat(+)light(+) samples was decreased after irradiation. The flexural strength of the specimen irradiated for long time showed a higher value than the required standard value, indicating that the effect of irradiation was weak. We suggest that coating with the ultraviolet responsive photocatalyst TiO₂ is useful for the development of orthodontic resin with antimicrobial properties. Full article

(This article belongs to the Special Issue Bioactive and Therapeutic Dental Materials)

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17 pages, 5607 KiB

Open AccessFeature PaperArticle

Au and AuCu Nanoparticles Supported on SBA-15 Ordered Mesoporous Titania-Silica as Catalysts for Methylene Blue Photodegradation

by Isabel Barroso-Martín¹

, Elisa Moretti^2,*

, Aldo Talon², Loretta Storaro², Enrique Rodríguez-Castellón¹

and Antonia Infantes-Molina^1,*

¹ Departamento de Química Inorgánica, Cristalografía y Mineralogía (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain

² Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, National Interuniversity Consortium of Materials Science and Technology (INSTM) Venice Research Unit, Via Torino 155/B, 30172 Mestre Venezia, Italy

Materials 2018, 11(6), 890; https://doi.org/10.3390/ma11060890 - 25 May 2018

Cited by 28 | Viewed by 5536

Abstract

The photocatalytic degradation of methylene blue (MB) dye has been performed under UV irradiation in aqueous suspension, employing photocatalysts based on Au (1.5 wt %) and AuCu (Au/Cu = 1, 2.0 wt %), and supported on SBA-15-ordered mesoporous silica, with and without titania [...] Read more.

The photocatalytic degradation of methylene blue (MB) dye has been performed under UV irradiation in aqueous suspension, employing photocatalysts based on Au (1.5 wt %) and AuCu (Au/Cu = 1, 2.0 wt %), and supported on SBA-15-ordered mesoporous silica, with and without titania (Si/Ti = 3), in order to evaluate the versatility of this mesoporous support in this type of reaction of great impact from the environmental point of view. Samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption-desorption at −196 °C, and X-ray photoelectron spectroscopy (XPS), so as to study their structural, optical, and chemical properties. All the prepared catalysts were found to be active in the test reaction. The bimetallic AuCu-based catalysts attained very high MB degradation values, in particular AuCu/SBA-15 titania-silica sample reached 100% of dye oxidation after the monitored reaction period (120 min). Full article

(This article belongs to the Special Issue Mesoporous Silica Catalysts)

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15 pages, 4188 KiB

Open AccessArticle

In-Liquid Plasma Process for Size- and Shape-Controlled Synthesis of Silver Nanoparticles by Controlling Gas Bubbles in Water

by Hyun-Jin Kim^1,2,†, Jun-Goo Shin^1,†, Choon-Sang Park¹, Dae Sub Kum¹, Bhum Jae Shin³, Jae Young Kim⁴, Hyung-Dal Park⁵, Muhan Choi¹ and Heung-Sik Tae^1,*

¹ School of Electronics Engineering, College of IT Engineering, Kyungpook National University, Daegu 41566, Korea

² SEMES Co. Ltd., Cheonan 31040, Korea

³ Department of Electronics Engineering, Sejong University, Seoul 05006, Korea

⁴ Department of New Biology, Daegu Gyeongbuk Institute of Science & Technology, Daegu 42988, Korea

⁵ Department of Mechanical Equipment Development, Radiation Technology eXcellence, Daejeon 34025, Korea

^† Hyun-Jin Kim and Jun-Goo Shin contributed equally to this work.

Materials 2018, 11(6), 891; https://doi.org/10.3390/ma11060891 - 25 May 2018

Cited by 24 | Viewed by 5123

Abstract

Most methods controlling size and shape of metal nanoparticles are chemical methods, and little work has been done using only plasma methods. Size- and shape-controlled synthesis of silver nanoparticles (Ag NPs) is proposed based on adjusting the gas bubble formation produced between two [...] Read more.

Most methods controlling size and shape of metal nanoparticles are chemical methods, and little work has been done using only plasma methods. Size- and shape-controlled synthesis of silver nanoparticles (Ag NPs) is proposed based on adjusting the gas bubble formation produced between two silver electrodes. The application of a voltage waveform with three different pulse widths during a plasma process in water can generate different gas bubble formations. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images of Ag NPs synthesized using three different bubble formations reveal that spherical Ag NPs are synthesized when very tiny bubbles are generated between two electrodes or when only the grounded electrode is enveloped with large gas bubbles, but Ag nanoplates are synthesized when both electrodes are completely enveloped with large gas bubbles. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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13 pages, 3613 KiB

Open AccessArticle

Residual Fatigue Properties of Asphalt Pavement after Long-Term Field Service

by Peide Cui¹

, Yue Xiao^1,*

, Mingjing Fang², Zongwu Chen^3,*, Mingwei Yi^4,5 and Mingliang Li⁴

¹ State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China

² School of Transportation, Wuhan University of Technology, Wuhan 430070, China

³ Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China

⁴ Research Institute of Highway Ministry of Transport, Beijing 100088, China

⁵ National Engineering Research Center of Road Maintenance Technologies, Beijing 100095, China

Materials 2018, 11(6), 892; https://doi.org/10.3390/ma11060892 - 25 May 2018

Cited by 40 | Viewed by 5535

Abstract

Asphalt pavement is widely used for expressways due to its advantages of flexibility, low cost, and easy maintenance. However, pavement failures, including cracking, raveling, and potholes, will appear after long-term service. This research evaluated the residual fatigue properties of asphalt pavement after long-term [...] Read more.

Asphalt pavement is widely used for expressways due to its advantages of flexibility, low cost, and easy maintenance. However, pavement failures, including cracking, raveling, and potholes, will appear after long-term service. This research evaluated the residual fatigue properties of asphalt pavement after long-term field service. Fatigue behavior of specimens with different pavement failure types, traffic load, service time, and layers were collected and characterized. Results indicate that after long-term field service, surface layer has a longer fatigue life under small stress levels, but shorter fatigue life under large stress levels. Longer service time results in greater sensitivity to loading stress, while heavier traffic results in shorter fatigue life. Surface and underneath layers present very close fatigue trend lines in some areas, indicating that the fatigue behavior of asphalt mixture in surface and underneath layers are aged to the same extent after eight to ten years of field service. Full article

(This article belongs to the Special Issue Environment-Friendly Construction Materials)

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13 pages, 6873 KiB

Open AccessArticle

Experimental and Theoretical Studies on Corrosion Inhibition of Niobium and Tantalum Surfaces by Carboxylated Graphene Oxide

by Valbonë Mehmeti and Fetah I. Podvorica^*

FNMS, Department of Chemistry, University of Prishtina, Prishtina 10000, Kosovo

Materials 2018, 11(6), 893; https://doi.org/10.3390/ma11060893 - 26 May 2018

Cited by 71 | Viewed by 4677

Abstract

The corrosion of two different metals, niobium and tantalum, in aqueous sulfuric acid solution has been studied in the presence and absence of carboxylated graphene oxide. Potentiodynamic measurements indicate that this nanomaterial inhibits corrosion due to its adsorption on the metal surfaces. The [...] Read more.

The corrosion of two different metals, niobium and tantalum, in aqueous sulfuric acid solution has been studied in the presence and absence of carboxylated graphene oxide. Potentiodynamic measurements indicate that this nanomaterial inhibits corrosion due to its adsorption on the metal surfaces. The adsorbed layer of carboxylated graphene hinders two electrochemical reactions: the oxidation of the metal and the transport of metal ions from the metal to the solution but also hydrogen evolution reaction by acting as a protective barrier. The adsorption behavior at the molecular level of the carboxylated graphene oxide with respect to Nb, NbO, Ta, and TaO (111) surfaces is also investigated using Molecular Dynamic and Monte Carlo calculations. Full article

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11 pages, 2222 KiB

Open AccessArticle

Time-Resolved Spectroscopy of Ethanol Evaporation on Free-Standing Porous Silicon Photonic Microcavities

by María Del Rayo Jiménez Vivanco¹, Godofredo García¹, Rafael Doti², Jocelyn Faubert² and Jesus Eduardo Lugo Arce^2,*

¹ Centro de Investigación en Dispositivos Semiconductores, Instituto de Ciencias (ICUAP), Benemerita Universidad Autonoma de Puebla (BUAP), Ciudad Universitaria, Puebla, Pue. C.P. 72570, Mexico

² Faubert Lab, School of Optometry, University of Montreal, Montreal H3T 1P1, QC, Canada

Materials 2018, 11(6), 894; https://doi.org/10.3390/ma11060894 - 26 May 2018

Cited by 4 | Viewed by 4038

Abstract

In this work, we have followed ethanol evaporation at two different concentrations using a fiber optic spectrometer and a screen capture application with a resolving capacity of 10 ms. The transmission spectra are measured in the visible-near-infrared range with a resolution of 0.5 [...] Read more.

In this work, we have followed ethanol evaporation at two different concentrations using a fiber optic spectrometer and a screen capture application with a resolving capacity of 10 ms. The transmission spectra are measured in the visible-near-infrared range with a resolution of 0.5 nm. Porous Silicon microcavities were fabricated by electrochemistry etching of crystalline silicon. The microcavities were designed to have a localized mode at 472 nm (blue band). Ethanol infiltration produces a redshift of approximately 17 nm. After a few minutes, a phase change from liquid to vapor occurs and the localized wavelength shifts back to the blue band. This process happens in a time window of only 60 ms. Our results indicate a difference between two distinct ethanol concentrations (70% and 35%). For the lower ethanol concentration, the blue shift rate process is slower in the first 30 ms and then it equals the high ethanol concentration blue shift rate. We have repeated the same process, but in an extended mode (750 nm), and have obtained similar results. Our results show that these photonic structures and with the spectroscopic technique used here can be implemented as a sensor with sufficient sensitivity and selectivity. Finally, since the photonic structure is a membrane, it can also be used as a transducer. For instance, by placing this photonic structure on top of a fast photodetector whose photo-response lies within the same bandwidth, the optical response can be transferred to an electrical signal. Full article

(This article belongs to the Special Issue Photonic Crystals for Chemical Sensing and Biosensing)

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11 pages, 2652 KiB

Open AccessArticle

Microstructure and Tensile Properties of AZ61 Alloy Sheets Processed by High-Ratio Extrusion with Subsequent Direct Aging Treatment

by Cheng-Cheng Zhang¹, Hui-Yuan Wang^1,2, Min Zha^1,2, Cheng Wang^1,*, Jie-Hua Li^1,3, Zhi-Zheng Yang¹ and Qi-Chuan Jiang¹

¹ Key Laboratory of Automobile Materials of Ministry of Education & School of Materials Science and Engineering, Nanling Campus, Jilin University, No. 5988 Renmin Street, Changchun 130025, China

² International Center of Future Science, Jilin University, Changchun 130012, China

³ Institute of Casting Research, University of Leoben, 8700 Leoben, Austria

Materials 2018, 11(6), 895; https://doi.org/10.3390/ma11060895 - 26 May 2018

Cited by 10 | Viewed by 3848

Abstract

A high extrusion ratio of 166:1 was applied to commercial AZ61 alloy in one step with an extrusion speed of 2.1 m·min⁻¹. The effects of DA (direct aging) treatment on the microstructure and tensile properties of extruded alloy were investigated. The [...] Read more.

A high extrusion ratio of 166:1 was applied to commercial AZ61 alloy in one step with an extrusion speed of 2.1 m·min⁻¹. The effects of DA (direct aging) treatment on the microstructure and tensile properties of extruded alloy were investigated. The extruded alloy exhibits fine DRXed grains and the average grain size is ~11 μm. After DA treatment at 170 °C, the tensile strength and 0.2% offset yield strength is enhanced from 314 to 336 MPa and from 169 to 191 MPa respectively, sacrificing elongation from 26.5% to 23.3%. The grain size and texture distribution of extruded AZ61 scarcely evolve during the post aging treatment. However, the enhanced strength in peak-aged alloy is mainly caused by the high-density elliptical Mg₁₇Al₁₂ precipitates distributing uniformly along the grain boundaries or within the grains, by precipitation and dispersion hardening. Furthermore, the nano-sized precipitates effectively inhibit grains from coarsening by triggering pinning effects along the grain boundaries at elevated temperature. As a result, the peak-aged alloy exhibits a better superplasticity of 306.5% compared with that of 231.8% of extruded sample. This work provides a practical one-step method for mass-producing Mg alloy sheets with excellent tensile strength and ductility compared with those fabricated by conventional extrusion methods. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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11 pages, 8171 KiB

Open AccessArticle

Alternative Carrier Solvents for Pigments Extracted from Spalting Fungi

by Lauren Pittis¹, Diego Rodrigues de Oliveira², Sarath M. Vega Gutierrez²

and Seri C. Robinson^2,*

¹ Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA

² Wood Science & Engineering, Oregon State University, Corvallis, OR 97331, USA

Materials 2018, 11(6), 897; https://doi.org/10.3390/ma11060897 - 27 May 2018

Cited by 9 | Viewed by 4061

Abstract

The use of both naturally occurring and synthetic pigmented wood has been prevalent in woodcraft for centuries. Modern manifestations generally involve either woodworkers’ aniline dyes, or pigments derived from a special class of fungi known as spalting fungi. While fungal pigments are more [...] Read more.

The use of both naturally occurring and synthetic pigmented wood has been prevalent in woodcraft for centuries. Modern manifestations generally involve either woodworkers’ aniline dyes, or pigments derived from a special class of fungi known as spalting fungi. While fungal pigments are more renewable than anilines and pose less of an environmental risk, the carrier required for these pigments—dichloromethane (DCM)—is both problematic for humans and tends to only deposit the pigments on the surface of wood instead of evenly within the material. Internal coloration of wood is key to adoption of a pigmenting system by woodworkers. To address this issue, five solvents that had moderate solubility with the pigments extracted from Chlorociboria aeruginosa and Scytalidium cuboideum were identified, in the hopes that a reduction in solubility would result in a greater amount of the pigment deposited inside the wood. Of the tested solvents, acetonitrile was found to produce the highest internal color in ash, Douglas-fir, madrone, mountain hemlock, Port-Orford cedar, Pacific silver fir, red alder and sugar maple. While these carrier solvents are not ideal for extracting the pigments from the fungi, acetonitrile in particular does appear to allow for more pigment to be deposited within wood. The use of acetonitrile over DCM offers new opportunities for possible industrial spalting applications, in which larger pieces of wood could be uniformly pigmented and sold to the end user in larger quantities than are currently available with spalted wood. Full article

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13 pages, 6039 KiB

Open AccessArticle

SEM/TEM Investigation of Aluminide Coating Co-Doped with Pt and Hf Deposited on Inconel 625

by Jerzy Morgiel¹, Maryana Zagula-Yavorska^2,*, Maciej Zubko³

and Jolanta Romanowska²

¹ Institute of Metallurgy and Materials Sciences, PAS, Reymonta 25 st., 30-059 Kraków, Poland

² Faculty of Mechanical Engineering and Aeronautics, Rzeszow University of Technology, al. Powstańców Warszawy 12, 35-959 Rzeszów, Poland

³ Institute of Materials Science, University of Silesia, Pułku Piechoty 1a st., 41-500 Chorzów, Poland

Materials 2018, 11(6), 898; https://doi.org/10.3390/ma11060898 - 27 May 2018

Cited by 6 | Viewed by 3767

Abstract

The effect of simultaneous introduction of Hf and Pt into aluminide coating deposited on Inconel 625 alloy was investigated using scanning and transmission electron microscopy (SEM/TEM) methods. The coating consisted of two layers: the additive and the interdiffusion. The additive layer and part [...] Read more.

The effect of simultaneous introduction of Hf and Pt into aluminide coating deposited on Inconel 625 alloy was investigated using scanning and transmission electron microscopy (SEM/TEM) methods. The coating consisted of two layers: the additive and the interdiffusion. The additive layer and part of the interdiffusion layer consist of the β-NiAl type phase. The middle part of the interdiffusion layer comprised an interpenetrating finger-like structure formed by the β-NiAl and TCP—σ type phases with numerous fine Cr precipitates in the former and occasional larger precipitates of NbC carbides interspersed in between them. The σ type phase inclusions are situated at the border between the substrate and the interdiffusion layer. The experiment showed that platinum fully dissolves in the β-NiAl-type matrix, while most of the introduced hafnium accumulates in HfO₂ dioxide precipitates located close to the additive/interdifusion interface. Full article

(This article belongs to the Section Advanced Materials Characterization)

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13 pages, 9163 KiB

Open AccessArticle

Effects of Three Calcium Silicate Cements on Inflammatory Response and Mineralization-Inducing Potentials in a Dog Pulpotomy Model

by Chung-Min Kang^1,2,†

, Jiwon Hwang^1,†, Je Seon Song^1,3, Jae-Ho Lee^1,3, Hyung-Jun Choi^1,3 and Yooseok Shin^3,4,*

¹ Department of Pediatric Dentistry, College of Dentistry, Yonsei University, Seoul, 03722, Korea

² Department of Pharmacology, College of Medicine, Yonsei University, Seoul 03722, Korea

³ Oral Science Research Center, College of Dentistry, Yonsei University, Seoul 03722, Korea

⁴ Department of Conservative Dentistry, College of Dentistry, Yonsei University, 50-1 Yonseiro, Seodaemun-Gu, Seoul 03722, Korea

^† These authors contributed equally to this work.

Materials 2018, 11(6), 899; https://doi.org/10.3390/ma11060899 - 27 May 2018

Cited by 15 | Viewed by 5717

Abstract

This beagle pulpotomy study compared the inflammatory response and mineralization-inducing potential of three calcium silicate cements: ProRoot mineral trioxide aggregate (MTA) (Dentsply, Tulsa, OK, USA), OrthoMTA (BioMTA, Seoul, Korea), and Endocem MTA (Maruchi, Wonju, Korea). Exposed pulp tissues were capped with ProRoot MTA, [...] Read more.

This beagle pulpotomy study compared the inflammatory response and mineralization-inducing potential of three calcium silicate cements: ProRoot mineral trioxide aggregate (MTA) (Dentsply, Tulsa, OK, USA), OrthoMTA (BioMTA, Seoul, Korea), and Endocem MTA (Maruchi, Wonju, Korea). Exposed pulp tissues were capped with ProRoot MTA, OrthoMTA, or Endocem MTA. After 8 weeks, we extracted the teeth, then performed hematoxylin-eosin and immunohistochemical staining with osteocalcin and dentin sialoprotein. Histological evaluation comprised a scoring system with eight broad categories and analysis of calcific barrier areas. We evaluated 44 teeth capped with ProRoot MTA (n = 15), OrthoMTA (n = 18), or Endocem MTA (n = 11). Most ProRoot MTA specimens formed continuous calcific barriers; these pulps contained inflammation-free palisading patterns in the odontoblastic layer. Areas of the newly formed calcific barrier were greater with ProRoot MTA than with Endocem MTA (p = 0.006). Although dentin sialoprotein was highly expressed in all three groups, the osteocalcin expression was reduced in the OrthoMTA and Endocem MTA groups. ProRoot MTA was superior to OrthoMTA and Endocem MTA in all histological analyses. ProRoot MTA and OrthoMTA resulted in reduced pulpal inflammation and more complete calcific barrier formation, whereas Endocem MTA caused a lower level of calcific barrier continuity with tunnel defects. Full article

(This article belongs to the Special Issue Bioactive and Therapeutic Dental Materials)

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17 pages, 4612 KiB

Open AccessArticle

Waste-Based Pervious Concrete for Climate-Resilient Pavements

by Hsin-Lung Ho¹, Ran Huang², Lih-Chuan Hwang³, Wei-Ting Lin^4,*

and Hui-Mi Hsu⁴

¹ Institute of Materials Engineering, National Taiwan Ocean University, No. 2, Peining Rd., Keelung 202, Taiwan

² Department of Harbor and River Engineering, National Taiwan Ocean University, No. 2, Peining Rd., Keelung 202, Taiwan

³ Department of Health and Leisure Management, LanYang Institute of Technology, No. 79, Fuxing Rd., Toucheng Township, Yilan 261, Taiwan

⁴ Department of Civil Engineering, National Ilan University, No. 1, Sec. 1, Shennong Rd., Yilan 260, Taiwan

Materials 2018, 11(6), 900; https://doi.org/10.3390/ma11060900 - 27 May 2018

Cited by 34 | Viewed by 4130

Abstract

For the sake of environmental protection and circular economy, cement reduction and cement substitutes have become popular research topics, and the application of green materials has become an important issue in the development of building materials. This study developed green pervious concrete using [...] Read more.

For the sake of environmental protection and circular economy, cement reduction and cement substitutes have become popular research topics, and the application of green materials has become an important issue in the development of building materials. This study developed green pervious concrete using water-quenched blast-furnace slag (BFS) and co-fired fly ash (CFFA) to replace cement. The objectives of this study were to gauge the feasibility of using a non-cement binder in pervious concrete and identify the optimal binder mix design in terms of compressive strength, permeability, and durability. For filled percentage of voids by cement paste (FPVs) of 70%, 80%, and 90%, which mixed with CFFA and BFS as the binder (40 + 60%, 50 + 50%, and 60 + 40%) to create pervious concrete with no cement. The results indicate that the complete (100%) replacement of cement with CFFA and BFS with no alkaline activator could induce hydration, setting, and hardening. After a curing period of 28 days, the compressive strength with different FPVs could reach approximately 90% that of the control cement specimens. The cementless pervious concrete specimens with BFS:CFFA = 7:3 and FPV = 90% presented better engineering properties and permeability. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2018)

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14 pages, 6477 KiB

Open AccessArticle

The Evaluation of Physio-Mechanical and Tribological Characterization of Friction Composites Reinforced by Waste Corn Stalk

by Yunhai Ma^1,2,3,4, Siyang Wu^1,2,3

, Jian Zhuang^1,2,3,*, Jin Tong^1,2,3, Yang Xiao^1,2,3 and Hongyan Qi^1,2,3

¹ State key laboratory of automotive simulation and control, Jilin University, Changchun 130022, China

² Key Laboratory of Bionic Engineering, Ministry of Education, Jilin University, Changchun 130022, China

³ College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China

⁴ State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China

Materials 2018, 11(6), 901; https://doi.org/10.3390/ma11060901 - 27 May 2018

Cited by 30 | Viewed by 4607

Abstract

This paper addressed the potential use of fibers from waste corn stalk as reinforcing materials in friction composites. The friction composites with different contents of corn stalk fibers were prepared, and their tribological and physio-mechanical behaviors were characterized. It was found that the [...] Read more.

This paper addressed the potential use of fibers from waste corn stalk as reinforcing materials in friction composites. The friction composites with different contents of corn stalk fibers were prepared, and their tribological and physio-mechanical behaviors were characterized. It was found that the incorporation of corn stalk fibers had a positive effect on the friction coefficients and wear rates of friction composites. Based on comparisons of the overall performance, FC-6 (containing 6 wt % corn stalk fibers) was selected as the best performing specimen. The fade ratio of specimen FC-6 was 7.8% and its recovery ratio was 106.5%, indicating excellent fade resistance and recovery behaviors. The wear rate of specimen FC-6 was the lowest (0.427 × 10⁻⁷ mm³ (N·mm)⁻¹ at 350 °C) among all tested composites. Furthermore, worn surface morphology was characterized by scanning electron microscopy and confocal laser scanning microscopy. The results revealed that the satisfactory wear resistance performances were associated with the secondary plateaus formed on the worn surfaces. This research was contributive to the environmentally-friendly application of waste corn stalk. Full article

(This article belongs to the Special Issue Polymeric Materials: Surfaces, Interfaces and Bioapplications)

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12 pages, 2665 KiB

Open AccessArticle

Effect of CNT/PDMS Nanocomposites on the Dynamics of Pioneer Bacterial Communities in the Natural Biofilms of Seawater

by Yubin Ji^1,†, Yuan Sun^1,†, Yanhe Lang², Lei Wang^3,*

, Bing Liu¹ and Zhizhou Zhang^3,4,*

¹ School of Science, Harbin University of Commerce, Harbin 150076, China

² Key Laboratory of Saline-alkali Vegetation Ecology Restoration in Oil Field (SAVER), Ministry of Education, Alkali Soil Natural Environmental Science Center (ASNESC), Northeast Forestry University, Harbin 150040, China

³ School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China

⁴ School of Marine Science and Technology, Harbin Institute of Technology at Weihai, Weihai 264209, China

^† These authors contributed equally to this work.

Materials 2018, 11(6), 902; https://doi.org/10.3390/ma11060902 - 28 May 2018

Cited by 17 | Viewed by 3714

Abstract

In this study, the antifouling (AF) performance of different carbon nanotubes (CNTs)-modified polydimethylsiloxane (PDMS) nanocomposites (PCs) was examined directly in the natural seawater, and further analyzed using the Multidimensional Scale Analyses (MDS) method. The early-adherent bacterial communities in the natural biofilms adhering to [...] Read more.

In this study, the antifouling (AF) performance of different carbon nanotubes (CNTs)-modified polydimethylsiloxane (PDMS) nanocomposites (PCs) was examined directly in the natural seawater, and further analyzed using the Multidimensional Scale Analyses (MDS) method. The early-adherent bacterial communities in the natural biofilms adhering to different PC surfaces were investigated using the single-stranded conformation polymorphism (SSCP) technique. The PCs demonstrated differences and reinforced AF properties in the field, and they were prone to clustering according to the discrepancies within different CNT fillers. Furthermore, most PC surfaces only demonstrated weak modulating effects on the biological colonization and successional process of the early bacterial communities in natural biofilms, indicating that the presence of the early colonized prokaryotic microbes would be one of the primary causes of colonization and deterioration of the PCs. C6 coating seems to be promising for marine AF applications, since it has a strong perturbation effect on pioneer prokaryotic colonization. Full article

(This article belongs to the Special Issue Polymeric Materials: Surfaces, Interfaces and Bioapplications)

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12 pages, 7272 KiB

Open AccessArticle

Enhancing Thermoelectric Properties through Control of Nickel Interstitials and Phase Separation in Heusler/Half-Heusler TiNi_1.1Sn Composites

by Emily E. Levin^1,2

, Francesca Long^1,2,†, Jason E. Douglas^1,2,‡, Malinda L. C. Buffon^1,2,§, Leo K. Lamontagne^1,2, Tresa M. Pollock^1,2 and Ram Seshadri^1,2,*

¹ Materials Department, University of California, Santa Barbara, CA 93106, USA

² Materials Research Laboratory, University of California, Santa Barbara, CA 93106, USA

^† Current address: Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA.

^‡ Current address: Materials Science and Engineering Division, NIST, Gaithersburg, MD 20899, USA.

^§ Current address: Intel Corporation, Hillsboro, OR 97124, USA.

Materials 2018, 11(6), 903; https://doi.org/10.3390/ma11060903 - 28 May 2018

Cited by 5 | Viewed by 5748

Abstract

Thermoelectric devices, which allow direct conversion of heat into electrical energy, require materials with improved figures of merit (

z T

) in order to ensure widespread adoption. Several techniques have been proposed to increase the

z T

of known thermoelectric materials through [...] Read more.

Thermoelectric devices, which allow direct conversion of heat into electrical energy, require materials with improved figures of merit (

z T

) in order to ensure widespread adoption. Several techniques have been proposed to increase the

z T

of known thermoelectric materials through the reduction of thermal conductivity, including heavy atom substitution, grain size reduction and inclusion of a semicoherent second phase. The goal in these approaches is to reduce thermal conductivity through phonon scattering without modifying the electronic properties. In this work, we demonstrate that Ni interstitials in the half-Heusler thermoelectric TiNiSn can be created and controlled in order to improve physical properties. Ni interstitials in TiNi

_{1.1}

Sn are not thermodynamically stable and, instead, are kinetically trapped using appropriate heat treatments. The Ni interstitials, which act as point defect phonon scattering centers and modify the electronic states near the Fermi level, result in reduced thermal conductivity and enhance the Seebeck coefficient. The best materials tested here, created from controlled heat treatments of TiNi

_{1.1}

Sn samples, display

z T

= 0.26 at 300 K, the largest value reported for compounds in the Ti–Ni–Sn family. Full article

(This article belongs to the Special Issue Half-Heusler, Silicide and Zintl-type Thermoelectric Materials)

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12 pages, 3190 KiB

Open AccessArticle

Influence of Surface Defects and Size on Photochemical Properties of SnO₂ Nanoparticles

by Mahdi Ilka¹, Susanta Bera^1,2,3 and Se-Hun Kwon^1,2,3,*

¹ School of Materials Science and Engineering, Pusan National University, Busan 46241, Korea

² Global Frontier R&D Center for Hybrid Interface Materials, Pusan National University, Busan 46241, Korea

³ Institute of Materials Technology, Pusan National University, Busan 46241, Korea

Materials 2018, 11(6), 904; https://doi.org/10.3390/ma11060904 - 28 May 2018

Cited by 35 | Viewed by 4941

Abstract

We report the successful synthesis of surface defective small size (SS) SnO₂ nanoparticles (NPs) by adopting a low temperature surfactant free solution method. The structural properties of the NPs were analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and [...] Read more.

We report the successful synthesis of surface defective small size (SS) SnO₂ nanoparticles (NPs) by adopting a low temperature surfactant free solution method. The structural properties of the NPs were analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The presence of surface defects, especially oxygen vacancies, in the sample were characterized using micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence emission. The Brunauer–Emmet–Teller (BET) nitrogen adsorption–desorption isotherms demonstrated the superior textural properties (high surface area and uniform pore size) of SS SnO₂ compared to large size (LS) SnO₂. A comparable study was drawn between SS SnO₂ and LS SnO₂ NPs and a significant decrease in the concentration of surface defects was observed for the LS sample. The results showed that surface defects significantly depend upon the size of the NPs. The surface defects formed within the band gap energy level of SnO₂ significantly participated in the recombination process of photogenerated charge carriers, improving photochemical properties. Moreover, the SS SnO₂ showed superior photoelectrochemical (PEC) and photocatalytic activities compared to the LS SnO₂. The presence of a comparatively large number of surface defects due to its high surface area may enhance the photochemical activity by reducing the recombination rate of the photogenerated charges. Full article

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17 pages, 6199 KiB

Open AccessArticle

Tensile, Quasistatic and Dynamic Fracture Properties of Nano-Al₂O₃-Modified Epoxy Resin

by Zhiwei Duan¹, Hailing He¹, Wenyan Liang^1,*, Zhenqing Wang¹, Liang He¹ and Xiaohong Zhang²

¹ Smart Structrues and Advanced Composite Materials Lab, Harbin Engineering University, Harbin, 150001, China

² School of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China

Materials 2018, 11(6), 905; https://doi.org/10.3390/ma11060905 - 28 May 2018

Cited by 33 | Viewed by 4314

Abstract

Epoxy resin, modified with different particle sizes (50 nm, 100 nm, 200 nm) and contents (1 wt %, 3 wt %, 5 wt %, 7 wt %) was manufactured. The mechanical behaviors of tensile, quasistatic fracture and dynamic fracture under SHPB (split Hopkinson [...] Read more.

Epoxy resin, modified with different particle sizes (50 nm, 100 nm, 200 nm) and contents (1 wt %, 3 wt %, 5 wt %, 7 wt %) was manufactured. The mechanical behaviors of tensile, quasistatic fracture and dynamic fracture under SHPB (split Hopkinson pressure bar) loading were investigated. The dynamic fracture behaviors of the composites were evaluated by 2D-DIC (digital image correlation) and the strain gauge technique, and the fracture surface was examined by SEM (scanning electron microscope). According to the results, the tensile modulus and strength significantly increased for epoxy resin modified with 5 wt % Al₂O₃ of 50 nm. The quasistatic fracture toughness of modified epoxy resin increased with the particle content. However, the fracture toughness of epoxy resin modified with high content fillers decreased for particle agglomeration that existed in epoxy resin. The crack propagation velocity can be decreased for epoxy resin modified with particles under dynamic loading. The dynamic initiation fracture toughness of modified epoxy resin increases with both particle size and content, but when the fillers have a high content, the particle size effects are weak. For the composite under dynamic loading conditions, the toughening mechanism is also affected by particle size. Full article

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14 pages, 2904 KiB

Open AccessArticle

One-Step Hydrothermal Synthesis of Zeolite X Powder from Natural Low-Grade Diatomite

by Guangyuan Yao, Jingjing Lei, Xiaoyu Zhang, Zhiming Sun^*

and Shuilin Zheng^*

School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China

Materials 2018, 11(6), 906; https://doi.org/10.3390/ma11060906 - 28 May 2018

Cited by 61 | Viewed by 7648

Abstract

Zeolite X powder was synthesized using natural low-grade diatomite as the main source of Si but only as a partial source of Al via a simple and green hydrothermal method. The microstructure and surface properties of the obtained samples were characterized by powder [...] Read more.

Zeolite X powder was synthesized using natural low-grade diatomite as the main source of Si but only as a partial source of Al via a simple and green hydrothermal method. The microstructure and surface properties of the obtained samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), wavelength dispersive X-ray fluorescence (XRF), calcium ion exchange capacity (CEC), thermogravimetric-differential thermal (TG-DTA) analysis, and N₂ adsorption-desorption technique. The influence of various synthesis factors, including aging time and temperature, crystallization time and temperature, Na₂O/SiO₂ and H₂O/Na₂O ratio on the CEC of zeolite, were systematically investigated. The as-synthesized zeolite X with binary meso-microporous structure possessed remarkable thermal stability, high calcium ion exchange capacity of 248 mg/g and large surface area of 453 m²/g. In addition, the calcium ion exchange capacity of zeolite X was found to be mainly determined by the crystallization degree. In conclusion, the synthesized zeolite X using diatomite as a cost-effective raw material in this study has great potential for industrial application such as catalyst support and adsorbent. Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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10 pages, 3907 KiB

Open AccessArticle

Graphitized Carbon: A Promising Stable Cathode Catalyst Support Material for Long Term PEMFC Applications

by Paritosh Kumar Mohanta^*, Fabian Regnet and Ludwig Jörissen

Zentrum für Sonnenenergie-und Wasserstoff-Forschung Baden-Württemberg, Helmholtzstrsse 8, 89081 Ulm, Germany

Materials 2018, 11(6), 907; https://doi.org/10.3390/ma11060907 - 28 May 2018

Cited by 29 | Viewed by 6165

Abstract

Stability of cathode catalyst support material is one of the big challenges of polymer electrolyte membrane fuel cells (PEMFC) for long term applications. Traditional carbon black (CB) supports are not stable enough to prevent oxidation to CO₂ under fuel cell operating conditions. [...] Read more.

Stability of cathode catalyst support material is one of the big challenges of polymer electrolyte membrane fuel cells (PEMFC) for long term applications. Traditional carbon black (CB) supports are not stable enough to prevent oxidation to CO₂ under fuel cell operating conditions. The feasibility of a graphitized carbon (GC) as a cathode catalyst support for low temperature PEMFC is investigated herein. GC and CB supported Pt electrocatalysts were prepared via an already developed polyol process. The physical characterization of the prepared catalysts was performed using transmission electron microscope (TEM), X-ray Powder Diffraction (XRD) and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis, and their electrochemical characterizations were conducted via cyclic voltammetry(CV), rotating disk electrode (RDE) and potential cycling, and eventually, the catalysts were processed using membrane electrode assemblies (MEA) for single cell performance tests. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SEM) have been used as MEA diagonostic tools. GC showed superior stability over CB in acid electrolyte under potential conditions. Single cell MEA performance of the GC-supported catalyst is comparable with the CB-supported catalyst. A correlation of MEA performance of the supported catalysts of different Brunauer–Emmett–Teller (BET) surface areas with the ionomer content was also established. GC was identified as a promising candidate for catalyst support in terms of both of the stability and the performance of fuel cell. Full article

(This article belongs to the Special Issue Hydrogen and Fuel Cells: From Materials to Systems)

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15 pages, 4676 KiB

Open AccessArticle

The Preparation, Characterization and Formation Mechanism of a Calcium Phosphate Conversion Coating on Magnesium Alloy AZ91D

by Dong Liu^1,2,3, Yanyan Li¹, Yong Zhou² and Yigang Ding^2,*

¹ School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, Wuhan 430205, China

² Key Lab for Green Chemical Process of Ministry of Education, Wuhan Institute of Technology, Wuhan 430205, China

³ State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China

Materials 2018, 11(6), 908; https://doi.org/10.3390/ma11060908 - 28 May 2018

Cited by 29 | Viewed by 5783

Abstract

The poor corrosion resistance of magnesium alloys is one of the main obstacles preventing their widespread usage. Due to the advantages of lower cost and simplicity in operation, chemical conversion coating has drawn considerable attention for its improvement of the corrosion resistance of [...] Read more.

The poor corrosion resistance of magnesium alloys is one of the main obstacles preventing their widespread usage. Due to the advantages of lower cost and simplicity in operation, chemical conversion coating has drawn considerable attention for its improvement of the corrosion resistance of magnesium alloys. In this study, a calcium phosphate coating was prepared on magnesium alloy AZ91D by chemical conversion. For the calcium phosphate coating, the effect of processing parameters on the microstructure and corrosion resistance was studied by scanning electron microscope (SEM) and electrochemical methods, and the coating composition was characterized by X-ray diffraction (XRD). The calcium phosphate coating was mainly composed of CaHPO₄·2H₂O (DCPD), with fewer cracks and pores. The coating with the leaf-like microstructure provided great corrosion resistance to the AZ91D substrate, and was obtained under the following conditions: 20 min, ambient temperature, and no stirring. At the same time, the role of NH₄H₂PO₄ as the coating-forming agent and the acidifying agent in the conversion process was realized, and the formation mechanism of DCPD was discussed in detail in this work. Full article

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15 pages, 17640 KiB

Open AccessArticle

Characterization of Magnesium Silicate Hydrate (MSH) Gel Formed by Reacting MgO and Silica Fume

by Tingting Zhang¹

, Jing Zou¹, Baomin Wang¹, Zhenlin Wu², Yuan Jia^3,* and Christopher R. Cheeseman⁴

¹ Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116023, China

² School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116023, China

³ Hebei Provincial Key Laboratory of Inorganic Nonmetallic, College of Materials Science and Engineering, North China University of Science and Technology, Tangshan 063210, China

⁴ Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK

Materials 2018, 11(6), 909; https://doi.org/10.3390/ma11060909 - 28 May 2018

Cited by 87 | Viewed by 8173

Abstract

Magnesium silicate hydrate (MSH) gel was formed by reacting magnesium oxide (MgO) with silica fume (SF) in distilled water. The MSH was prepared using a MgO/SF molar ratio of 1.0 (40:60 weight ratio). Samples were analyzed during hydration process up to 300 days [...] Read more.

Magnesium silicate hydrate (MSH) gel was formed by reacting magnesium oxide (MgO) with silica fume (SF) in distilled water. The MSH was prepared using a MgO/SF molar ratio of 1.0 (40:60 weight ratio). Samples were analyzed during hydration process up to 300 days at room temperature. The MSH characterization has been carried out using a range of analytical techniques. Quantitative analysis was achieved using thermogravimetric analysis (TG/DTG) with a de-convolution technology. The structure of MSH gel was characterized using solid state nuclear magnetic resonance (²⁹Si NMR) and Fourier transform infrared (FT-IR) spectroscopy. Transmission electron microscopy (TEM) was used to investigate MSH microstructure. Compared with natural magnesium silicate hydrate minerals, the structure of MSH gel is highly disordered and generates on the surface of particles, producing a shell structure with cavity. The molecular structure of MSH phase is layered. The results also show that the extent of polymerization of MSH gel is related to the solution pH during hydration. Full article

(This article belongs to the Section Advanced Materials Characterization)

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15 pages, 4418 KiB

Open AccessArticle

Nonlinear Buckling Analysis of Functionally Graded Graphene Reinforced Composite Shallow Arches with Elastic Rotational Constraints under Uniform Radial Load

by Yonghui Huang

, Zhicheng Yang

, Airong Liu^* and Jiyang Fu

Guangzhou University-Tamkang University Joint Research Center for Engineering Structure Disaster Prevention and Control, Guangzhou University, Guangzhou 510006, China

Materials 2018, 11(6), 910; https://doi.org/10.3390/ma11060910 - 28 May 2018

Cited by 63 | Viewed by 4363

Abstract

The buckling behavior of functionally graded graphene platelet-reinforced composite (FG-GPLRC) shallow arches with elastic rotational constraints under uniform radial load is investigated in this paper. The nonlinear equilibrium equation of the FG-GPLRC shallow arch with elastic rotational constraints under uniform radial load is [...] Read more.

The buckling behavior of functionally graded graphene platelet-reinforced composite (FG-GPLRC) shallow arches with elastic rotational constraints under uniform radial load is investigated in this paper. The nonlinear equilibrium equation of the FG-GPLRC shallow arch with elastic rotational constraints under uniform radial load is established using the Halpin-Tsai micromechanics model and the principle of virtual work, from which the critical buckling load of FG-GPLRC shallow arches with elastic rotational constraints can be obtained. This paper gives special attention to the effect of the GPL distribution pattern, weight fraction, geometric parameters, and the constraint stiffness on the buckling load. The numerical results show that all of the FG-GPLRC shallow arches with elastic rotational constraints have a higher buckling load-carrying capacity compared to the pure epoxy arch, and arches of the distribution pattern X have the highest buckling load among four distribution patterns. When the GPL weight fraction is constant, the thinner and larger GPL can provide the better reinforcing effect to the FG-GPLRC shallow arch. However, when the value of the aspect ratio is greater than 4, the flakiness ratio is greater than 103, and the effect of GPL’s dimensions on the buckling load of the FG-GPLRC shallow arch is less significant. In addition, the buckling model of FG-GPLRC shallow arch with elastic rotational constraints is changed as the GPL distribution patterns or the constraint stiffness changes. It is expected that the method and the results that are presented in this paper will be useful as a reference for the stability design of this type of arch in the future. Full article

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16 pages, 3562 KiB

Open AccessArticle

Coextrusion-Based 3D Plotting of Ceramic Pastes for Porous Calcium Phosphate Scaffolds Comprised of Hollow Filaments

by In-Hwan Jo¹, Young-Hag Koh^1,* and Hyoun-Ee Kim²

¹ School of Biomedical Engineering, Korea University, Seoul 02841, Korea

² Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea

Materials 2018, 11(6), 911; https://doi.org/10.3390/ma11060911 - 29 May 2018

Cited by 17 | Viewed by 4577

Abstract

This paper demonstrates the utility of coextrusion-based 3D plotting of ceramic pastes (CoEx-3DP) as a new type of additive manufacturing (AM) technique, which can produce porous calcium phosphate (CaP) ceramic scaffolds comprised of hollow CaP filaments. In this technique, green filaments with a [...] Read more.

This paper demonstrates the utility of coextrusion-based 3D plotting of ceramic pastes (CoEx-3DP) as a new type of additive manufacturing (AM) technique, which can produce porous calcium phosphate (CaP) ceramic scaffolds comprised of hollow CaP filaments. In this technique, green filaments with a controlled core/shell structure can be produced by coextruding an initial feedrod, comprised of the carbon black (CB) core and CaP shell, through a fine nozzle in an acetone bath and then deposited in a controlled manner according to predetermined paths. In addition, channels in CaP filaments can be created through the removal of the CB cores during heat-treatment. Produced CaP scaffolds had two different types of pores with well-defined geometries: three-dimensionally interconnected pores (~360 × 230 μm² in sizes) and channels (>100 μm in diameter) in hollow CaP filaments. The porous scaffolds showed high compressive strengths of ~12.3 ± 2.2 MPa at a high porosity of ~73 vol % when compressed parallel to the direction of the hollow CaP filaments. In addition, the mechanical properties of porous CaP scaffolds could be tailored by adjusting their porosity, for example, compressive strengths of 4.8 ± 1.1 MPa at a porosity of ~82 vol %. The porous CaP scaffold showed good biocompatibility, which was assessed by in vitro cell tests, where several the cells adhered to and spread actively with the outer and inner surfaces of the hollow CaP filaments. Full article

(This article belongs to the Section Biomaterials)

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12 pages, 2044 KiB

Open AccessFeature PaperArticle

Surface Characterization of Mesoporous CoO_x/SBA-15 Catalyst upon 1,2-Dichloropropane Oxidation

by Elisabetta Finocchio^1,*, Jonatan Gonzalez-Prior², Jose Ignacio Gutierrez-Ortiz²

, Ruben Lopez-Fonseca², Guido Busca¹ and Beatriz De Rivas^2,*

¹ Dipartimento di Ingegneria Civile, Chimica e Ambientale (DICCA), Università degli Studi di Genova, Via all’Opera Pia 15, I-16145 Genova, Italy

² Departamento de Ingeniería Química, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, P.O. Box 644, E-48080 Bilbao, Spain

Materials 2018, 11(6), 912; https://doi.org/10.3390/ma11060912 - 29 May 2018

Cited by 7 | Viewed by 3750

Abstract

The active combustion catalyst that is based on 30 wt % cobalt oxide on mesoporous SBA-15 has been tested in 1,2-dichloropropane oxidation and is characterized by means of FT-IR (Fourier transform infrared spectroscopy) and ammonia-TPD (temperature-programmed desorption). In this work, we report the [...] Read more.

The active combustion catalyst that is based on 30 wt % cobalt oxide on mesoporous SBA-15 has been tested in 1,2-dichloropropane oxidation and is characterized by means of FT-IR (Fourier transform infrared spectroscopy) and ammonia-TPD (temperature-programmed desorption). In this work, we report the spectroscopic evidence for the role of surface acidity in chloroalkane conversion. Both Lewis acidity and weakly acidic silanol groups from SBA support are involved in the adsorption and initial conversion steps. Moreover, total oxidation reaction results in the formation of new Bronsted acidic sites, which are likely associated with the generation of HCl at high temperature and its adsorption at the catalyst surface. Highly dispersed Co oxide on the mesoporous support and Co-chloride or oxychloride particles, together with the presence of several families of acidic sites originated from the conditioning effect of reaction products may explain the good activity of this catalyst in the oxidation of Chlorinated Volatile Organic Compounds. Full article

(This article belongs to the Special Issue Mesoporous Silica Catalysts)

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13 pages, 5712 KiB

Open AccessArticle

Heating Characteristics and Induced Healing Efficiencies of Asphalt Mixture via Induction and Microwave Heating

by Quantao Liu^1,2, Cheng Chen¹, Bin Li¹, Yihan Sun³ and Hechuan Li^1,*

¹ State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Luoshi Road 122, Wuhan 430070, China

² National & Local Joint Engineering Laboratory for Transportation and Civil Engineering Materials, Chongqing Jiaotong University, Chongqing 400074, China

³ Zhejiang Provincial Institute of Communications Planning, Design & Research, Hangzhou 310015, China

Materials 2018, 11(6), 913; https://doi.org/10.3390/ma11060913 - 29 May 2018

Cited by 48 | Viewed by 4700

Abstract

This paper investigates the heating characteristics and induced healing efficiencies of asphalt mixture containing steel fiber under induction heating and microwave heating. The heating characteristics of an asphalt mixture with different heating methods were studied with an infrared camera. The healing performance of [...] Read more.

This paper investigates the heating characteristics and induced healing efficiencies of asphalt mixture containing steel fiber under induction heating and microwave heating. The heating characteristics of an asphalt mixture with different heating methods were studied with an infrared camera. The healing performance of the asphalt mixture specimens in different healing conditions were investigated by observing the crack closure and testing the fracture resistance recovery after healing. The results showed that the heating speed at the surface of asphalt mixture with induction heating was much higher than that with microwave machine heating, under a similar output power and the same method of radiation. While the temperature distribution within the asphalt mixture under induction heating was quite uneven, microwave heating resulted in a more uniform temperature distribution. The effective heating depth of microwave heating is much higher than that of induction heating. Gradient healing occurred within the sample heated with induction healing, while a uniform healing effect can be achieved with microwave heating. Full article

(This article belongs to the Special Issue Environment-Friendly Construction Materials)

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17 pages, 13975 KiB

Open AccessArticle

Influence of Homogenization on Microstructural Response and Mechanical Property of Al-Cu-Mn Alloy

by Jian Wang¹, Yalin Lu^1,2,*

, Dongshuai Zhou^1,2, Lingyan Sun¹, Renxing Li¹ and Wenting Xu¹

¹ School of Materials Engineering, Jiangsu University of Technology, Changzhou 213001, China

² Key Construction Laboratory of Green Forming and Equipment from Jiangsu Province, Changzhou 213001, China

Materials 2018, 11(6), 914; https://doi.org/10.3390/ma11060914 - 29 May 2018

Cited by 10 | Viewed by 4131

Abstract

The evolution of the microstructures and properties of large direct chill (DC)-cast Al-Cu-Mn alloy ingots during homogenization was investigated. The results revealed that the Al-Cu-Mn alloy ingots had severe microsegregation and the main secondary phase was Al₂Cu, with minimal Al₇ [...] Read more.

The evolution of the microstructures and properties of large direct chill (DC)-cast Al-Cu-Mn alloy ingots during homogenization was investigated. The results revealed that the Al-Cu-Mn alloy ingots had severe microsegregation and the main secondary phase was Al₂Cu, with minimal Al₇Cu₂Fe phase. Numerous primary eutectic phases existed in the grain boundary and the main elements were segregated at the interfaces along the interdendritic region. The grain boundaries became discontinuous, residual phases were effectively dissolved into the matrix, and the segregation degree of all elements was reduced dramatically during homogenization. In addition, the homogenized alloys exhibited improved microstructures with finer grain size, higher number density of dislocation networks, higher density of uniformly distributed θ′ or θ phase (Al₂Cu), and higher volume fraction of high-angle grain boundaries compared to the nonhomogenized samples. After the optimal homogenization scheme treated at 535 °C for 10 h, the tensile strength and elongation% were about 24 MPa, 20.5 MPa, and 1.3% higher than those of the specimen without homogenization treatment. Full article

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14 pages, 3859 KiB

Open AccessArticle

Effects of Build Orientation on Surface Morphology and Bone Cell Activity of Additively Manufactured Ti6Al4V Specimens

by Volker Weißmann^1,2,*, Philipp Drescher³

, Hermann Seitz³

, Harald Hansmann⁴, Rainer Bader², Anika Seyfarth², Annett Klinder² and Anika Jonitz-Heincke²

¹ Faculty of Engineering, University of Applied Science, Technology, Business and Design, Philipp-Müller-Str. 14, 23966 Wismar, Germany

² Biomechanics and Implant Technology Research Laboratory, Department of Orthopedics, Rostock University Medical Centre, Doberaner Strasse 142, Rostock 18057, Germany

³ Fluid Technology and Microfluidics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock, Germany

⁴ Institute for Polymer Technologies e.V., Alter Holzhafen 19, 23966 Wismar, Germany

Materials 2018, 11(6), 915; https://doi.org/10.3390/ma11060915 - 29 May 2018

Cited by 38 | Viewed by 4440

Abstract

Additive manufacturing of lightweight or functional structures by selective laser beam (SLM) or electron beam melting (EBM) is widespread, especially in the field of medical applications. SLM and EBM processes were applied to prepare Ti6Al4V test specimens with different surface orientations (0°, 45° [...] Read more.

Additive manufacturing of lightweight or functional structures by selective laser beam (SLM) or electron beam melting (EBM) is widespread, especially in the field of medical applications. SLM and EBM processes were applied to prepare Ti6Al4V test specimens with different surface orientations (0°, 45° and 90°). Roughness measurements of the surfaces were conducted and cell behavior on these surfaces was analyzed. Hence, human osteoblasts were seeded on test specimens to determine cell viability (metabolic activity, live-dead staining) and gene expression of collagen type 1 (Col1A1), matrix metalloprotease (MMP) 1 and its natural inhibitor, TIMP1, after 3 and 7 days. The surface orientation of specimens during the manufacturing process significantly influenced the roughness. Surface roughness showed significant impact on cellular viability, whereas differences between the time points day 3 and 7 were not found. Collagen type 1 mRNA synthesis rates in human osteoblasts were enhanced with increasing roughness. Both manufacturing techniques further influenced the induction of bone formation process in the cell culture. Moreover, the relationship between osteoblastic collagen type 1 mRNA synthesis rates and specimen orientation during the building process could be characterized by functional formulas. These findings are useful in the designing of biomedical applications and medical devices. Full article

(This article belongs to the Section Biomaterials)

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14 pages, 2326 KiB

Open AccessArticle

Comparison of the Microtensile Bond Strength of a Polyetherketoneketone (PEKK) Tooth Post Cemented with Various Surface Treatments and Various Resin Cements

by Chan-Hong Song¹, Jae-Won Choi¹

, Young-Chan Jeon¹, Chang-Mo Jeong¹, So-Hyoun Lee¹, Eun-Sook Kang², Mi-Jung Yun^1,* and Jung-Bo Huh^1,*

¹ Department of Prosthodontics, Dental Research Institute, Institute of Translational Dental Sciences, School of Dentistry, Pusan National University, Yangsan 50612, Korea

² Department of Prosthodontics, In-Je University Haeundae Paik Hospital, Busan 48108, Korea

Materials 2018, 11(6), 916; https://doi.org/10.3390/ma11060916 - 29 May 2018

Cited by 41 | Viewed by 5007

Abstract

The aim of this in-vitro research was to evaluate the microtensile bond strength in the newly introduced PEKK tooth post with various surface treatments and resin cements. A fiberglass tooth post was included in order to compare it with PEKK as a possible [...] Read more.

The aim of this in-vitro research was to evaluate the microtensile bond strength in the newly introduced PEKK tooth post with various surface treatments and resin cements. A fiberglass tooth post was included in order to compare it with PEKK as a possible post material. The microtensile bond strengths of the fiberglass post (FRC Postec Plus) and the PEKK post (Pekkton^®) were tested using three kinds of self-adhesive resin cements (G-CEM LinkAce, Multilink Speed, and RelyX U200) and one self-etching resin cement (PANAVIA F2.0). The surface treatments of the fiberglass posts were processed according to the manufacturer’s recommendations (F1, application of 37% phosphoric acid etching gel and silanization). For the PEKK post groups, various surface treatments were performed like no surface treatment (P1), sandblasting (P2), silica-coating and silanization (P3), and sandblasting with a composite primer (P4). In the surface treatment, PEKK posts with silica coating and silane treatment (P3) showed a significantly higher microtensile bond strength (mean MPa: 18.09, p < 0.05). The highest microtensile bond strength was shown when the PEKK posts were treated with a silica coating and silane treatment and cemented with RelyX U200 (mean MPa: 22.22). The PEKK posts with surface treatments of silica-coating and silanization or sandblasting displayed superior microtensile bond strengths (mean MPa: 18.09 and 16.25, respectively) compared to the conventional fiberglass posts (mean MPa: 14.93, p < 0.05). Full article

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15 pages, 16304 KiB

Open AccessArticle

Initial Self-Healing Temperatures of Asphalt Mastics Based on Flow Behavior Index

by Chao Li, Shaopeng Wu^*, Guanyu Tao and Yue Xiao

State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China

Materials 2018, 11(6), 917; https://doi.org/10.3390/ma11060917 - 29 May 2018

Cited by 13 | Viewed by 3806

Abstract

Increasing temperature is a simple and convenient method to accelerate the self-healing process of bitumen. However, bitumen may not achieve the healing capability at lower temperature, and may be aged if temperature is too high. In addition, the bitumen is mixed with mineral [...] Read more.

Increasing temperature is a simple and convenient method to accelerate the self-healing process of bitumen. However, bitumen may not achieve the healing capability at lower temperature, and may be aged if temperature is too high. In addition, the bitumen is mixed with mineral filler and formed as asphalt mastic in asphalt concrete, so it is more accurate to study the initial self-healing from the perspective of asphalt mastic. The primary purpose of this research was to examine the initial self-healing temperature of asphalt mastic, which was determined by the flow behavior index obtained from the flow characteristics. Firstly, the texture and geometry characteristics of two fillers were analyzed, and then the initial self-healing temperature of nine types of asphalt mastic, pure bitumen (PB) and styrene-butadiene-styrene (SBS) modified bitumen were determined by the flow behavior index. Results demonstrate that the average standard deviation of gray-scale texture value of limestone filler (LF) is 21.24% lower than that of steel slag filler (SSF), showing that the steel slag filler has a better particle distribution and geometry characteristics. Also the initial self-healing temperatures of asphalt mastics with 0.2, 0.4 and 0.6 LF-PB volume ratio are 46.5 °C, 47.2 °C and 49.4 °C, which are 1.4 °C, 0.8 °C and 0.4 °C higher than that of asphalt mastics with SSF-PB, but not suitable for the evaluation of asphalt mastic contained SBS modified bitumen because of unique structure and performance of SBS. Full article

(This article belongs to the Special Issue Environment-Friendly Construction Materials)

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11 pages, 3623 KiB

Open AccessArticle

A Friction-Inertial-Based Rotary Motor: Design, Modelling and Experiments

by Bo Zhang, Fangxin Chen, Haiyang Li, Zhijiang Du, Lining Sun and Wei Dong^*

State Key Laboratory of Robotics and System, Harbin Institute of Technology, 2 Yikuang Street, Harbin 150080, China

Materials 2018, 11(6), 918; https://doi.org/10.3390/ma11060918 - 29 May 2018

Cited by 23 | Viewed by 3518

Abstract

A friction–inertial-based rotary motor driven by shear piezoelectric actuators (SPAs) is proposed in this paper, which possesses many superior features, including high resolution, compact size, large load-capacity, and low cost. In order to eliminate the step loss and increase the step size when [...] Read more.

A friction–inertial-based rotary motor driven by shear piezoelectric actuators (SPAs) is proposed in this paper, which possesses many superior features, including high resolution, compact size, large load-capacity, and low cost. In order to eliminate the step loss and increase the step size when an external load is applied, the power-function-shape driving signal was used to actuate the rotary motor. According to the step characteristics under this driving signal, two motion modes were observed and defined, namely the stick-shoot motion mode and the stick-slip-shoot motion mode. The former motion mode can realize a large step size while the later one cannot due to the slipping during the rising phase. After analyzing the results from the numerical simulation and the experiment study, it was found that the motion performance of the motor is closely related to the preload and the base number of the driving signal rather than the size of SPAs, which means the motor can be further downsized according to its actual requirements. Full article

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24 pages, 18268 KiB

Open AccessArticle

A Study of the Particle-Level Fabric and Morphology of Granular Soils under One-Dimensional Compression Using Insitu X-ray CT Imaging

by Md Ferdous Alam, Asadul Haque^*

and Pathegama Gamage Ranjith

Department of Civil Engineering, Monash University, Melbourne, Victoria 3800, Australia

Materials 2018, 11(6), 919; https://doi.org/10.3390/ma11060919 - 29 May 2018

Cited by 33 | Viewed by 6903

Abstract

The particle morphology and fabric of a granular soil influence its mechanical behavior. This study focuses on the evolution of the particle-level fabric and morphology of a uniformly graded sand sample subjected to one-dimensional compression up to 64 MPa. The microstructural changes with [...] Read more.

The particle morphology and fabric of a granular soil influence its mechanical behavior. This study focuses on the evolution of the particle-level fabric and morphology of a uniformly graded sand sample subjected to one-dimensional compression up to 64 MPa. The microstructural changes with increased stresses were captured using in situ high-resolution X-ray computed tomography (X-ray CT) imaging. The processed images of particles were separated using the Monash Particle Separation Method (MPSM) for subsequent fabric and morphological analyses. The variations of various fabric parameters were studied using the separated particle volumes. New methods of assessing the morphology and crushability of particles were introduced including a comprehensive algorithm for determining coordination number, branch and contact normal vectors. Results of all fabric parameters were analyzed and discussed with reference to observed changes. Potential mechanisms were identified and relevant correlations were developed where warranted. Full article

(This article belongs to the Section Advanced Materials Characterization)

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14 pages, 4345 KiB

Open AccessArticle

Evaluation of Fine Aggregate Morphology by Image Method and Its Effect on Skid-Resistance of Micro-Surfacing

by Yue Xiao^1,†

, Feng Wang¹, Peide Cui^1,*

, Lei Lei^2,†

, Juntao Lin³ and Mingwei Yi^4,5

¹ State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China

² Shenzhen MacRitchie Technology Co., Ltd., Shen Zhen 518101, China

³ Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China

⁴ National Engineering Research Center of Road Maintenance Technologies, Beijing 100095, China

⁵ Research Institute of Highway Ministry of Transport, Beijing 100088, China

^† These authors contributed equally to this work.

Materials 2018, 11(6), 920; https://doi.org/10.3390/ma11060920 - 29 May 2018

Cited by 69 | Viewed by 5899

Abstract

Micro-surfacing is a widely used pavement preventive maintenance technology used all over the world, due to its advantages of fast construction, low maintenance cost, good waterproofness, and skid-resistance performance. This study evaluated the fine aggregate morphology and surface texture of micro-surfacing by AIMS [...] Read more.

Micro-surfacing is a widely used pavement preventive maintenance technology used all over the world, due to its advantages of fast construction, low maintenance cost, good waterproofness, and skid-resistance performance. This study evaluated the fine aggregate morphology and surface texture of micro-surfacing by AIMS (aggregate image measurement system), and explored the effect of aggregate morphology on skid-resistance of single-grade micro-surfacing. Sand patch test and British pendulum test were also used to detect skid-resistance for comparison with the image-based method. Wet abrasion test was used to measure skid-resistance durability for feasibility verification of single-grade micro-surfacing. The results show that the effect of Form2D on the skid-resistance of micro-surfacing is much stronger than that of angularity. Combining the feasibility analysis of durability and skid-resistance, 1.18–2.36 grade micro-surfacing meets the requirements of durability and skid-resistance at the same time. This study also determined that, compared with British pendulum test, the texture result obtained by sand patch test fits better with results of image method. Full article

(This article belongs to the Special Issue Environment-Friendly Construction Materials)

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15 pages, 5243 KiB

Open AccessArticle

Improving Thermo-Oxidative Stability of Nitrile Rubber Composites by Functional Graphene Oxide

by Rui Zhong¹, Zhao Zhang¹, Hongguo Zhao², Xianru He^1,*, Xin Wang^1,*

and Rui Zhang³

¹ State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation & School of Materials Science and Engineering, Southwest Petroleum University, Chengdu 610500, China

² Petrochemical Research Institute, PetroChina, Lanzhou 730060, China

³ Institut für Physik, Universität Rostock, Albert-Einstein-Str. 23-24, 18051 Rostock, Germany

Materials 2018, 11(6), 921; https://doi.org/10.3390/ma11060921 - 30 May 2018

Cited by 30 | Viewed by 5741

Abstract

Graphene oxide (GO), modified with anti-aging agent p-phenylenediamine (PPD), was added into nitrile rubber (NBR) in order to improve the thermo-oxidative stability of NBR. The modification of GO and the transformation of functional groups were characterized by Fourier transform infrared spectroscopy (FTIR), [...] Read more.

Graphene oxide (GO), modified with anti-aging agent p-phenylenediamine (PPD), was added into nitrile rubber (NBR) in order to improve the thermo-oxidative stability of NBR. The modification of GO and the transformation of functional groups were characterized by Fourier transform infrared spectroscopy (FTIR), Raman, and X-ray diffraction (XRD). Mechanical performances of NBR composites before and after the thermo-oxidative aging were recorded. The results of dynamic mechanical analysis (DMA) show an increased storage modulus (G’) and a decreased value of area of tan δ peak after introducing modified GO into NBR. It indicates that filler particles show positive interaction with molecular chains. The thermo-oxidative stability of composites was investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Then, the thermo-oxidative aging kinetic parameters were obtained by the Flynn–Wall–Ozawa (FWO) equation. The results of aging tests show that the thermo-oxidative stability of rubber matrix increases obviously after introducing GO–PPD. In addition, mechanical properties (tensile strength and elongation at break) of both before and after aged NBR/GO–PPD composites were superior to that of NBR. This work provides meaningful guidance for achieving multifunction thermo-oxidative aging resistance rubber composites. Full article

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10 pages, 3475 KiB

Open AccessArticle

Seebeck Coefficient of Thermocouples from Nickel-Coated Carbon Fibers: Theory and Experiment

by Hardianto Hardianto^1,2,*

, Gilbert De Mey³, Izabela Ciesielska-Wrόbel¹, Carla Hertleer¹ and Lieva Van Langenhove¹

¹ Department of Materials, Textiles and Chemical Engineering, Ghent University, Technologiepark 907, 9052 Zwijnaarde, Belgium

² Department of Textile Chemistry, Politeknik STTT Bandung, Jalan Jakarta 31, Bandung 40272, Indonesia

³ Department of Electronics and Information Systems, Ghent University, Technologiepark 15, 9052 Zwijnaarde, Belgium

Materials 2018, 11(6), 922; https://doi.org/10.3390/ma11060922 - 30 May 2018

Cited by 7 | Viewed by 5508

Abstract

Thermocouples made of etched and non-etched nickel-coated carbon yarn (NiCCY) were investigated. Theoretic Seebeck coefficients were compared to experimental results from measurements of generated electric voltage by these thermocouples. The etching process for making thermocouples was performed by immersion of NiCCY in the [...] Read more.

Thermocouples made of etched and non-etched nickel-coated carbon yarn (NiCCY) were investigated. Theoretic Seebeck coefficients were compared to experimental results from measurements of generated electric voltage by these thermocouples. The etching process for making thermocouples was performed by immersion of NiCCY in the solution containing a mixture of hydrochloric acid (HCl) (37% of concentration), and hydrogen peroxide (H₂O₂) in three different concentrations—3%, 6%, and 10%. Thirty minutes of etching to remove Ni from NiCCY was followed by washing and drying. Next, the ability to generate electrical voltage by the thermocouples (being a junction of the etched and the non-etched NiCCY) was measured in different ranges of temperatures, both a cold junction (291.15–293.15 K) and a hot junction (293.15–325.15 K). A formula predicting the Seebeck coefficient of this thermocouple was elaborated, taking into consideration resistance values of the tested samples. It was proven that there is a good agreement between the theoretical and experimental data, especially for the yarns etched with 6% and 10% peroxide (both were mixed with HCl). The electrical resistance of non-fully etched nickel remaining on the carbon fiber surface (

R_{1}

) can have a significant effect on the thermocouples’ characteristics. Full article

(This article belongs to the Special Issue Carbon Fibers and Their Composite Materials)

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11 pages, 3594 KiB

Open AccessArticle

Effect of Antibacterial Plant Extracts on the Morphology of Electrospun Poly(Lactic Acid) Fibres

by Peiwen Wang

and Elisa Mele^*

Department of Materials, Loughborough University, Loughborough LE11 3TU, UK

Materials 2018, 11(6), 923; https://doi.org/10.3390/ma11060923 - 30 May 2018

Cited by 30 | Viewed by 5782

Abstract

Essential oils (EOs) of clary sage and black pepper induce changes in the morphology of poly(lactic acid) (PLA) electrospun fibres. The chemical composition of the oils is analysed by gas chromatography-mass spectrometry and Fourier-transform infrared spectroscopy; while the evaporation rate of the EOs [...] Read more.

Essential oils (EOs) of clary sage and black pepper induce changes in the morphology of poly(lactic acid) (PLA) electrospun fibres. The chemical composition of the oils is analysed by gas chromatography-mass spectrometry and Fourier-transform infrared spectroscopy; while the evaporation rate of the EOs and their main chemical components is characterised by Thermogravimetric Analysis. The addition of EOs generate thermodynamic instabilities during the electrospinning process, leading to the formation of fibres with either wrinkled (for clary sage oil) or nano-textured surfaces (for black pepper oil). The morphology of the PLA-EOs fibres is investigated by Scanning Electron Microscopy. Together with a well-defined structure, the fibres produced also possess antibacterial activity, as demonstrated by viability loss tests conducted on E. coli and S. epidermidis. Bacteria inactivation efficiency of 76 and 100% is reported for the composite PLA/essential oils electrospun mats. The composite mats produced are promising in the biomedical field, where nanotopography offers physical cues to regulate cell behaviour, and the delivery of therapeutic compounds (essential oils) limits microbial growth. Full article

(This article belongs to the Special Issue Biodegradable Polymeric Composites: Development and Industrial Applications)

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14 pages, 5161 KiB

Open AccessArticle

Degradation of Glaukonite Sandstone as a Result of Alkali-Silica Reactions in Cement Mortar

by Przemysław Czapik

Department of Building Engineering Technologies and Organization, Kielce University of Technology, Al. Tysiąclecia Państwa Polskiego 7, 25-314 Kielce, Poland

Materials 2018, 11(6), 924; https://doi.org/10.3390/ma11060924 - 30 May 2018

Cited by 6 | Viewed by 4038

Abstract

The mechanism of concrete degradation as a result of an alkali-silica reaction (ASR) largely depends on the mineral composition and microstructure of the reactive aggregate. This paper shows the reactivity results of quartz-glaukonitic sandstone, which is mainly responsible for the reactivity of some [...] Read more.

The mechanism of concrete degradation as a result of an alkali-silica reaction (ASR) largely depends on the mineral composition and microstructure of the reactive aggregate. This paper shows the reactivity results of quartz-glaukonitic sandstone, which is mainly responsible for the reactivity of some post-glacial gravels, available in Poland. After initial petrographic observations under a light microscope, the mode of sandstone degradation triggered by the reaction with sodium and potassium hydroxides was identified using scanning electron microscopy (SEM). It has been found that chalcedony agglomerates present in sandstone are separated from the rock matrix and subsequently cause the cracks formation in this matrix. Additionally, microcrystalline and potentially reactive silica is also dispersed in sandstone cement. Full article

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15 pages, 1538 KiB

Open AccessArticle

Mechanical and Morphological Effect of Plant Based Antimicrobial Solutions on Maxillofacial Silicone Elastomer

by Sophia Tetteh^1,*

, Richard J. Bibb¹

and Simon J. Martin²

¹ Loughborough Design School, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK

² Materials, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK

Materials 2018, 11(6), 925; https://doi.org/10.3390/ma11060925 - 30 May 2018

Cited by 12 | Viewed by 5107

Abstract

The objective of this study was to determine the effect of plant based antimicrobial solutions specifically tea tree and Manuka oil on facial silicone elastomers. The purpose of this in vitro study was to evaluate the effect of disinfection with plant extract solution [...] Read more.

The objective of this study was to determine the effect of plant based antimicrobial solutions specifically tea tree and Manuka oil on facial silicone elastomers. The purpose of this in vitro study was to evaluate the effect of disinfection with plant extract solution on mechanical properties and morphology on the silicone elastomer. Test specimens were subjected to disinfection using tea tree oil, Manuka oil and the staphylococcus epidermidis bacteria. Furthermore, a procedure duration was used in the disinfection process to simulate up to one year of usage. Over 500 test specimens were fabricated for all tests performed namely hardness, elongation, tensile, tear strength tests, visual inspection and lastly surface characterization using SEM. A repeated measures ANOVA revealed that hardness and elongation at break varied significantly over the time period, whereas this was not observed in the tear and tensile strength parameters of the test samples. Full article

(This article belongs to the Collection Dental Biomaterials)

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11 pages, 4764 KiB

Open AccessFeature PaperArticle

Crystal Structure and Thermoelectric Properties of Lightly Substituted Higher Manganese Silicides

by Yuzuru Miyazaki^*

, Haruki Hamada, Hiroki Nagai and Kei Hayashi

Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan

Materials 2018, 11(6), 926; https://doi.org/10.3390/ma11060926 - 30 May 2018

Cited by 32 | Viewed by 4124

Abstract

The dissipation of MnSi layered precipitates during solidification is critical for further enhancement of the thermoelectric properties of the higher manganese silicides. We have investigated the effects of partial substitution of V in Mn sites and of Ge in Si sites on the [...] Read more.

The dissipation of MnSi layered precipitates during solidification is critical for further enhancement of the thermoelectric properties of the higher manganese silicides. We have investigated the effects of partial substitution of V in Mn sites and of Ge in Si sites on the crystal structures and thermoelectric properties of these silicides in detail. As previously reported, a small amount of V-substitution is quite effective in completely dissipating the MnSi striations; in contrast, a small proportion of these MnSi striations always remains present in the Ge-substitution case, even in the vicinity of the Ge solubility limits. For completely MnSi-dissipated samples, domain separation of the regular and highly strained arrangements of the Si atoms is realized. This domain separation suppresses the deterioration of the carrier mobility of the partially V-substituted samples and maintains even higher electrical conductivity to yield a high thermoelectric power factor of ∼2.3 mW/K

^{2}

m at higher temperatures. Full article

(This article belongs to the Special Issue Half-Heusler, Silicide and Zintl-type Thermoelectric Materials)

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13 pages, 3933 KiB

Open AccessArticle

A Single-Step Surface Modification of Electrospun Silica Nanofibers Using a Silica Binding Protein Fused with an RGD Motif for Enhanced PC12 Cell Growth and Differentiation

by Wen Shuo Chen¹, Ling Yu Guo¹, Amien Mohamed Masroujeh², Anna Morgan Augustine², Cheng Kang Tsai¹, Ting Yu Chin³, Yui Whei Chen-Yang^1,* and Mong-Lin Yang^2,*

¹ Department of Chemistry, Center for Nanotechnology, Center for Biomedical Technology, Chung Yuan Christian University, Chung Li 32023, Taiwan

² Department of Science, Concordia University Saint Paul, Saint Paul, MN 55104, USA

³ Department of Bioscience Technology, Chung Yuan Christian University, Chung Li, 32023, Taiwan

Materials 2018, 11(6), 927; https://doi.org/10.3390/ma11060927 - 30 May 2018

Cited by 6 | Viewed by 5878

Abstract

In this study, a previously known high-affinity silica binding protein (SB) was genetically engineered to fuse with an integrin-binding peptide (RGD) to create a recombinant protein (SB-RGD). SB-RGD was successfully expressed in Escherichia coli and purified using silica beads through a simple and [...] Read more.

In this study, a previously known high-affinity silica binding protein (SB) was genetically engineered to fuse with an integrin-binding peptide (RGD) to create a recombinant protein (SB-RGD). SB-RGD was successfully expressed in Escherichia coli and purified using silica beads through a simple and fast centrifugation method. A further functionality assay showed that SB-RGD bound to the silica surface with an extremely high affinity that required 2 M MgCl₂ for elution. Through a single-step incubation, the purified SB-RGD proteins were noncovalently coated onto an electrospun silica nanofiber (SNF) substrate to fabricate the SNF-SB-RGD substrate. SNF-SB-RGD was characterized by a combination of scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and immunostaining fluorescence microscopy. As PC12 cells were seeded onto the SNF-SB-RGD surface, significantly higher cell viability and longer neurite extensions were observed when compared to those on the control surfaces. These results indicated that SB-RGD could serve as a noncovalent coating biologic to support and promote neuron growth and differentiation on silica-based substrates for neuronal tissue engineering. It also provides proof of concept for the possibility to genetically engineer protein-based signaling molecules to noncovalently modify silica-based substrates as bioinspired material. Full article

(This article belongs to the Special Issue Electrospun Materials 2018)

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14 pages, 5967 KiB

Open AccessArticle

Applying Low-Frequency Vibration for the Experimental Investigation of Clutch Hub Forming

by De’an Meng^1,2,*, Chengcheng Zhu^1,3,*, Xuzhe Zhao⁴ and Shengdun Zhao¹

¹ School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049, China

² School of Mechanical Engineering, Northwest Polytechnical University, Xi’an 710072, China

³ Department of Mechanical Engineering, National University of Singapore, Singapore 119260, Singapore

⁴ School of Engineering Technology, Purdue University, 401 N. Grant Street, West Lafayette, IN 47906, USA

Materials 2018, 11(6), 928; https://doi.org/10.3390/ma11060928 - 30 May 2018

Cited by 14 | Viewed by 4516

Abstract

A vibration-assisted plastic-forming method was proposed, and its influence on clutch hub forming process was investigated. The experiments were conducted on a vibration-assisted hydraulic extrusion press with adjustable frequency and amplitude. Vibration frequency and amplitude were considered in investigating the effect of vibration [...] Read more.

A vibration-assisted plastic-forming method was proposed, and its influence on clutch hub forming process was investigated. The experiments were conducted on a vibration-assisted hydraulic extrusion press with adjustable frequency and amplitude. Vibration frequency and amplitude were considered in investigating the effect of vibration on forming load and surface quality. Results showed that applying vibration can effectively reduce forming force and improve surface quality. The drop in forming load was proportional to the vibration frequency and amplitude, and the load decreased by up to 25%. Such reduction in forming load raised with amplitude increase because the increase in amplitude would accelerate punch relative speed, which then weakened the adhesion between workpiece and dies. By increasing the vibration frequency, the punch movement was enhanced, and the number of attempts to drag the lubricant out of the pits was increased. In this manner, the lubrication condition was improved greatly. The 3D surface topography testing confirmed the assumption. Moreover, vibration frequency exerted a more significant effect on the forming load reduction than vibration amplitude. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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14 pages, 6194 KiB

Open AccessArticle

Molecular Dynamics Study of an Amorphous Polyethylene/Silica Interface with Shear Tests

by Xiaoying Zhuang^1,2,3

and Shuai Zhou^1,*

¹ Institute of Continuum Mechanics, Leibniz University Hannover, 30167 Hannover, Germany

² Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China

³ Institute of Structural Mechanics, Bauhaus Universitat-Weimar, D-99423 Weimar, Germany

Materials 2018, 11(6), 929; https://doi.org/10.3390/ma11060929 - 31 May 2018

Cited by 30 | Viewed by 5030

Abstract

An amorphous polyethylene/silica (PE/S) interface exists in many materials. However, the research of the interfacial properties at microscale is lacking. Shear failure and adhesion properties of an amorphous PE/S interface are studied by molecular dynamics. The effects of PE chain length, the number [...] Read more.

An amorphous polyethylene/silica (PE/S) interface exists in many materials. However, the research of the interfacial properties at microscale is lacking. Shear failure and adhesion properties of an amorphous PE/S interface are studied by molecular dynamics. The effects of PE chain length, the number of chains, and coupling agents on the shear behavior and interfacial adhesion are investigated. It is found that the modified silica (mS) surface induces an increase in the adhesion strength compared to unmodified S. The damage process and failure mode of the PE/S and PE/mS interface are analyzed at microscale. The contribution of bond length, bond angle, torsional potentials, and nonbonded energy is estimated as a function of the shear deformation to clarify the deformation mechanisms. The energy partitioning results indicate that the elastic, yield, and postyielding regions are mostly controlled by the nonbonded interactions. The dihedral motions of the chains also have an influence. Furthermore, the simulation results exhibit how the internal mechanism evolves with the shear deformation. Full article

(This article belongs to the Special Issue Damage and Failure of Polymers, Polymer-Like Materials, Adhesives and Polymer Nanocomposites)

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11 pages, 2398 KiB

Open AccessArticle

Exploring the Potential of Electrical Impedance Tomography for Tissue Engineering Applications

by Hancong Wu¹

, Wenli Zhou², Yunjie Yang¹

, Jiabin Jia¹ and Pierre Bagnaninchi^3,*

¹ Agile Tomography Group, School of Engineering, The University of Edinburgh, Edinburgh EH9 3JL, UK;hason.wu@ed.ac.uk (H.W.)

² Department of Medical Oncology, Changzheng Hospital, Navy Medical University, Shanghai 200070, China

³ MRC Centre for Regenerative Medicine, The University of Edinburgh, Edinburgh EH16 4UU, UK

Materials 2018, 11(6), 930; https://doi.org/10.3390/ma11060930 - 31 May 2018

Cited by 35 | Viewed by 7224

Abstract

In tissue engineering, cells are generally cultured in biomaterials to generate three-dimensional artificial tissues to repair or replace damaged parts and re-establish normal functions of the body. Characterizing cell growth and viability in these bioscaffolds is challenging, and is currently achieved by destructive [...] Read more.

In tissue engineering, cells are generally cultured in biomaterials to generate three-dimensional artificial tissues to repair or replace damaged parts and re-establish normal functions of the body. Characterizing cell growth and viability in these bioscaffolds is challenging, and is currently achieved by destructive end-point biological assays. In this study, we explore the potential to use electrical impedance tomography (EIT) as a label-free and non-destructive technology to assess cell growth and viability. The key challenge in the tissue engineering application is to detect the small change of conductivity associated with sparse cell distributions in regards to the size of the hosting scaffold, i.e., low volume fraction, until they assemble into a larger tissue-like structure. We show proof-of-principle data, measure cells within both a hydrogel and a microporous scaffold with an ad-hoc EIT equipment, and introduce the frequency difference technique to improve the reconstruction. Full article

(This article belongs to the Special Issue Materials: 10th Anniversary)

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15 pages, 4176 KiB

Open AccessArticle

Experimental Analysis of MOC Composite with a Waste-Expanded Polypropylene-Based Aggregate

by Martina Záleská¹

, Milena Pavlíková¹

, Ondřej Jankovský²

, Michal Lojka², Adam Pivák¹

and Zbyšek Pavlík^1,*

¹ Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague 6, Czech Republic

² Department of Inorganic Chemistry, Faculty of Chemical Technology, University of Chemistry and Technology, Technická 5, 166 28 Prague 6, Czech Republic

Materials 2018, 11(6), 931; https://doi.org/10.3390/ma11060931 - 31 May 2018

Cited by 41 | Viewed by 5960

Abstract

Polypropylene (PP) is one of the most widely produced types of plastic worldwide, but its recycling is limited. This work presents a study of the utilization of expanded polypropylene (EPP) waste in a magnesium oxychloride cement (MOC) composite usable in the building industry. [...] Read more.

Polypropylene (PP) is one of the most widely produced types of plastic worldwide, but its recycling is limited. This work presents a study of the utilization of expanded polypropylene (EPP) waste in a magnesium oxychloride cement (MOC) composite usable in the building industry. MOC is formed by mixing magnesium oxide powder and a concentrated solution of magnesium chloride and is characterized by excellent bonding ability to large quantities of different types of aggregates. A developed air-cured MOC composite, where an EPP-based aggregate was used for the full replacement of natural aggregate, was investigated in terms of its basic physical, mechanical, thermal and water resistance properties. The results demonstrate that incorporation of EPP waste greatly improved the thermal insulation properties, while the mechanical resistance was reduced to an acceptable level. The developed MOC composite containing EPP waste can be considered as an alternative thermal insulation material applicable for the construction of floor or envelope construction systems. Full article

(This article belongs to the Section Advanced Composites)

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16 pages, 3330 KiB

Open AccessArticle

Study on Epoxy Resin Toughened by Epoxidized Hydroxy-Terminated Polybutadiene

by Zhen Ge^*, Wenguo Zhang

, Chao Huang and Yunjun Luo^*

School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China

Materials 2018, 11(6), 932; https://doi.org/10.3390/ma11060932 - 31 May 2018

Cited by 35 | Viewed by 5645

Abstract

Epoxy resin (EP) was toughened by epoxidized hydroxy-terminated polybutadiene (EHTPB), with the corresponding modified epoxy resin being prepared. In this paper, the microstructure of EHTPB-modified epoxy resin was characterized, while the influence of different contents of EHTPB on curing kinetics, mechanical properties, morphology, [...] Read more.

Epoxy resin (EP) was toughened by epoxidized hydroxy-terminated polybutadiene (EHTPB), with the corresponding modified epoxy resin being prepared. In this paper, the microstructure of EHTPB-modified epoxy resin was characterized, while the influence of different contents of EHTPB on curing kinetics, mechanical properties, morphology, thermal properties, dynamic thermomechanical (DMA) properties and crosslink density of the modified epoxy resin were also discussed. The results showed that the EHTPB-modified epoxy resin was successfully prepared and cured completely. The activation energy (E_a) of the modified epoxy resin decreased after the addition of EHTPB. With an increase in the EHTPB content, the tensile strength (σ_m) of the modified epoxy resin decreased and the breaking elongation (ε_b) increased gradually. The initial decomposition temperature (T_5%) and glass transition temperature (T_g) of the modified epoxy resin decreased with an increase in the EHTPB content. The modified epoxy resin had a rough fractured surface and the interface was blurred, presenting a ductile fracture. Full article

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20 pages, 12494 KiB

Open AccessArticle

Effect of Sigma Phase Morphology on the Degradation of Properties in a Super Duplex Stainless Steel

by Vahid A. Hosseini^1,2,*

, Leif Karlsson¹

, Sten Wessman^1,3 and Nuria Fuertes³

¹ Department of Engineering Science, University West, SE-461 86 Trollhättan, Sweden

² Innovatum AB., Trollhättan, SE-461 29 Trollhättan, Sweden

³ Swerea KIMAB AB, P.O. Box 7047, SE-164 40 Kista, Sweden

Materials 2018, 11(6), 933; https://doi.org/10.3390/ma11060933 - 1 Jun 2018

Cited by 75 | Viewed by 9964

Abstract

Sigma phase is commonly considered to be the most deleterious secondary phase precipitating in duplex stainless steels, as it results in an extreme reduction of corrosion resistance and toughness. Previous studies have mainly focused on the kinetics of sigma phase precipitation and influences [...] Read more.

Sigma phase is commonly considered to be the most deleterious secondary phase precipitating in duplex stainless steels, as it results in an extreme reduction of corrosion resistance and toughness. Previous studies have mainly focused on the kinetics of sigma phase precipitation and influences on properties and only a few works have studied the morphology of sigma phase and its influences on material properties. Therefore, the influence of sigma phase morphology on the degradation of corrosion resistance and mechanical properties of 2507 super duplex stainless steel (SDSS) was studied after 10 h of arc heat treatment using optical and scanning electron microscopy, electron backscattered diffraction analysis, corrosion testing, and thermodynamic calculations. A stationary arc was applied on the 2507 SDSS disc mounted on a water-cooled chamber, producing a steady-state temperature gradient covering the entire temperature range from room temperature to the melting point. Sigma phase was the major intermetallic precipitating between 630 °C and 1010 °C and its morphology changed from blocky to fine coral-shaped with decreasing aging temperature. At the same time, the average thickness of the precipitates decreased from 2.9 µm to 0.5 µm. The chemical composition of sigma was similar to that predicted by thermodynamic calculations when formed at 800–900 °C, but deviated at higher and lower temperatures. The formation of blocky sigma phase introduced local strain in the bulk of the primary austenite grains. However, the local strain was most pronounced in the secondary austenite grains next to the coral-shaped sigma phase precipitating at lower temperatures. Microstructures with blocky and coral-shaped sigma phase particles were prone to develop microscale cracks and local corrosion, respectively. Local corrosion occurred primarily in ferrite and in secondary austenite, which was predicted by thermodynamic calculations to have a low pitting resistance equivalent. To conclude, the influence of sigma phase morphology on the degradation of properties was summarized in two diagrams as functions of the level of static load and the severity of the corrosive environment. Full article

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18 pages, 3845 KiB

Open AccessArticle

Corrosion Performance of Nano-ZrO₂ Modified Coatings in Hot Mixed Acid Solutions

by Wenhua Xu^1,2

, Zhenyu Wang^1,*, En-Hou Han¹, Shuai Wang¹ and Qian Liu^1,3

¹ Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

² University of Chinese Academy of Sciences, Beijing 100049, China

³ School of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China

Materials 2018, 11(6), 934; https://doi.org/10.3390/ma11060934 - 1 Jun 2018

Cited by 29 | Viewed by 3544

Abstract

A nano-ZrO₂ modified coating system was prepared by incorporation of nano-ZrO₂ concentrates into phenolic-epoxy resin. The corrosion performance of the coatings was evaluated in hot mixed acid solution, using electrochemical methods combined with surface characterization, and the effects of nano-ZrO₂ [...] Read more.

A nano-ZrO₂ modified coating system was prepared by incorporation of nano-ZrO₂ concentrates into phenolic-epoxy resin. The corrosion performance of the coatings was evaluated in hot mixed acid solution, using electrochemical methods combined with surface characterization, and the effects of nano-ZrO₂ content were specially focused on. The results showed that 1% and 3% nano-ZrO₂ addition enhanced the corrosion resistance of the coatings, while 5% nano-ZrO₂ addition declined it. The coating with 3% nano-ZrO₂ presented the minimum amount of species diffusion, the lowest average roughness (5.94 nm), and the highest C/O ratio (4.55) and coating resistance, and it demonstrated the best corrosion performance among the coating specimens. Full article

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8 pages, 966 KiB

Open AccessArticle

Influence of Absorbable Calcium Sulfate-Based Bone Substitute Materials on Human Haemostasis—In Vitro Biological Behavior of Antibiotic Loaded Implants

by Dominik Pförringer^1,*,†, Norbert Harrasser^2,†, Marc Beirer¹, Moritz Crönlein¹, Axel Stemberger², Martijn Van Griensven¹

, Martin Lucke³, Rainer Burgkart^2,‡ and Andreas Obermeier^2,‡

¹ Klinikum rechts der Isar der Technischen Universität München, Klinik und Poliklinik für Unfallchirurgie, Ismaninger Str. 22, 81675 München, Germany

² Klinikum rechts der Isar der Technischen Universität München, Klinik für Orthopädie und Sportorthopädie, Ismaninger Str. 22, 81675 München, Germany

³ Chirurgisches Klinikum München Süd, Am Isarkanal 30, 81379 München, Germany

^† These authors contributed equally to this work.

^‡ These authors also contributed equally to this work.

Materials 2018, 11(6), 935; https://doi.org/10.3390/ma11060935 - 1 Jun 2018

Cited by 10 | Viewed by 4055

Abstract

Calcium sulfate (CS) formulations are frequently implanted as antibiotically impregnated bone substitutes in orthopedic and trauma surgery to prevent or treat bone infections. Calcium ions have been discussed as candidates to accelerate blood coagulation. The goal of this study is to evaluate substance-specific [...] Read more.

Calcium sulfate (CS) formulations are frequently implanted as antibiotically impregnated bone substitutes in orthopedic and trauma surgery to prevent or treat bone infections. Calcium ions have been discussed as candidates to accelerate blood coagulation. The goal of this study is to evaluate substance-specific influences of CS formulations on blood coagulation. Specific ELISAs were conducted to determine markers of activated blood coagulation after incubation of human blood with CS beads. Additionally, wettability with freshly drawn human blood was measured. Three different types of CS bone substitute beads were compared (CS dihydrate with tripalmitin, containing Gentamicin (Herafill^®-G: Group A) or Vancomycin (CaSO₄-V: Group B); and a CS hemihydrate with Tobramycin (Osteoset^®: Group C)). Examinations were performed by ELISA assays for F₁₊₂, FXIIa and C3a. Our results prove that none of the CS preparations accelerated single specific assays for activated coagulation markers. This allows the conclusion that neither Herafill^®-G (CaSO₄-G) nor CaSO₄-V alter haemostasis negatively. Blood samples incubated with Osteoset^® display an elevated F₁₊₂-activity. The addition of tripalmitin in Herafill^®-G shifts the original into a significantly hydrophobic formulation. This was additionally proven by contact angle examination of the three substances with freshly drawn human blood, showing that acceleration of plasmatic coagulation is hindered by lipids and induced by surface effects caused by presence of rapidly soluble calcium ions in the Osteoset^® preparation. Full article

(This article belongs to the Special Issue Bone Substitute Materials)

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24 pages, 1513 KiB

Open AccessArticle

Environmental Screening of Electrode Materials for a Rechargeable Aluminum Battery with an AlCl₃/EMIMCl Electrolyte

by Linda Ager-Wick Ellingsen^1,*, Alex Holland², Jean-Francois Drillet³, Willi Peters³, Martin Eckert³, Carlos Concepcion⁴, Oscar Ruiz⁴, Jean-François Colin⁵, Etienne Knipping⁶

, Qiaoyan Pan⁷, Richard G. A. Wills² and Guillaume Majeau-Bettez^1,8

¹ Industrial Ecology Programme and Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), Sem Sælandsvei 7, 7491 Trondheim, Norway

² Energy Technology Group, Faculty of Engineering and the Environment, University of Southampton, University Road, Southampton SO15 1BJ, UK

³ DECHEMA-Forschungsinstitut, Theodor-Heuss-Allee 25, 60486 Frankfurt am Main, Germany

⁴ Torrecid SA, Partida Torreta s/n, 12110 Alcora, Spain

⁵ Laboratoire des Matériaux, DEHT, LITEN, CEA, Université Grenoble Alpes, F-38000 Grenoble, France

⁶ Leitat Technological Center, Carrer de la Innovació, 2 08225 Terrassa, Spain

⁷ ACCUREC Recycling GmbH, Bataverstraße 21, DE-47809 Krefeld, Germany

⁸ CIRAIG, École Polytechnique de Montréal, dép. Génie Chimique 3333 Chemin Queen-Mary, Bureau 310 C.P. 6079 succ. Centre-ville, Montréal, QC H3C 3A7, Canada

Materials 2018, 11(6), 936; https://doi.org/10.3390/ma11060936 - 1 Jun 2018

Cited by 25 | Viewed by 8348

Abstract

Recently, rechargeable aluminum batteries have received much attention due to their low cost, easy operation, and high safety. As the research into rechargeable aluminum batteries with a room-temperature ionic liquid electrolyte is relatively new, research efforts have focused on finding suitable electrode materials. [...] Read more.

Recently, rechargeable aluminum batteries have received much attention due to their low cost, easy operation, and high safety. As the research into rechargeable aluminum batteries with a room-temperature ionic liquid electrolyte is relatively new, research efforts have focused on finding suitable electrode materials. An understanding of the environmental aspects of electrode materials is essential to make informed and conscious decisions in aluminum battery development. The purpose of this study was to evaluate and compare the relative environmental performance of electrode material candidates for rechargeable aluminum batteries with an AlCl₃/EMIMCl (1-ethyl-3-methylimidazolium chloride) room-temperature ionic liquid electrolyte. To this end, we used a lifecycle environmental screening framework to evaluate 12 candidate electrode materials. We found that all of the studied materials are associated with one or more drawbacks and therefore do not represent a “silver bullet” for the aluminum battery. Even so, some materials appeared more promising than others did. We also found that aluminum battery technology is likely to face some of the same environmental challenges as Li-ion technology but also offers an opportunity to avoid others. The insights provided here can aid aluminum battery development in an environmentally sustainable direction. Full article

(This article belongs to the Special Issue Advanced Materials for Aluminium-ion Battery)

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11 pages, 1742 KiB

Open AccessArticle

Rational Design of Porous Covalent Triazine-Based Framework Composites as Advanced Organic Lithium-Ion Battery Cathodes

by Ruoxin Yuan^†, Wenbin Kang^† and Chuhong Zhang^*

¹ State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu 610065, China

^† These authors contribute equally to this work.

Materials 2018, 11(6), 937; https://doi.org/10.3390/ma11060937 - 2 Jun 2018

Cited by 26 | Viewed by 5365

Abstract

In an effort to explore the use of organic high-performance lithium ion battery cathodes as an alternative to resolve the current bottleneck hampering the development of their inorganic counterparts, a rational strategy focusing on the optimal composition of covalent triazine-based frameworks (CTFs) with [...] Read more.

In an effort to explore the use of organic high-performance lithium ion battery cathodes as an alternative to resolve the current bottleneck hampering the development of their inorganic counterparts, a rational strategy focusing on the optimal composition of covalent triazine-based frameworks (CTFs) with carbon-based materials of varied dimensionalities is delineated. Two-dimensional reduced graphene oxide (rGO) with a compatible structural conformation with the layered CTF is the most suitable scaffold for the tailored mesopores in the polymeric framework, providing outstanding energy storage ability. Through facile ionothermal synthesis and structure engineering, the obtained CTF-rGO composite possesses a high specific surface area of 1357.27 m²/g, and when used as a lithium ion battery cathode it delivers a large capacity of 235 mAh/g in 80 cycles at 0.1 A/g along with a stable capacity of 127 mAh/g over 2500 cycles at 5 A/g. The composite with modified pore structure shows drastically improved performance compared to a pristine CTF, especially at large discharge currents. The CTF-rGO composite with excellent capacity, stability, and rate performance shows great promise as an emerging high-performance cathode that could revolutionize the conventional lithium-ion battery industry. Full article

(This article belongs to the Special Issue Hybrid Materials: New Synthetic Methods)

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13 pages, 4373 KiB

Open AccessArticle

Stress-Strain Curves and Modified Material Constitutive Model for Ti-6Al-4V over the Wide Ranges of Strain Rate and Temperature

by Xin Hou^1,2, Zhanqiang Liu^1,2,*

, Bing Wang^1,2, Woyun Lv^1,2, Xiaoliang Liang^1,2 and Yang Hua^1,2

¹ School of Mechanical Engineering, Shandong University, Jinan 250061, China

² Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE/Key National Demonstration Center for Experimental Mechanical Engineering Education, Jinan 250061, China

Materials 2018, 11(6), 938; https://doi.org/10.3390/ma11060938 - 2 Jun 2018

Cited by 68 | Viewed by 13593

Abstract

The mechanical properties of Ti-6Al-4V alloy are sensitive to strain rate and temperature load. The finite element simulation results of high-speed machining Ti-6Al-4V alloy depend on the accurate description of dynamic deformation. However, it is hard to describe the flow stress behavior in [...] Read more.

The mechanical properties of Ti-6Al-4V alloy are sensitive to strain rate and temperature load. The finite element simulation results of high-speed machining Ti-6Al-4V alloy depend on the accurate description of dynamic deformation. However, it is hard to describe the flow stress behavior in current constitutive models in a complex high-speed machining process for Ti-6Al-4V alloy. In this paper, the stress-strain curves of Ti-6Al-4V alloy under the wide ranges of strain rate and temperature are obtained by high-velocity uniaxial impact tests. The apparent coupling between temperature and strain is observed, which proves that the temperature is dependent on a hardening effect for Ti-6Al-4V alloy. A function describing the coupling between temperature and strain is then introduced into the modification for the original Johnson-Cook (JC) constitutive model. The maximum deviation between the predicted data from using the proposed modified JC constitutive model and experimental data is reduced from 10.43% to 4.19%. It can be concluded that the modified JC constitutive model is more suitable to describe the temperature-dependent hardening effect, which provides strong support for accurate finite element simulation of high-speed machining Ti-6Al-4V alloy. Full article

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9 pages, 2618 KiB

Open AccessArticle

Sol-Gel Hydrothermal Synthesis and Visible Light Photocatalytic Degradation Performance of Fe/N Codoped TiO₂ Catalysts

by Hsu-Hui Cheng^1,2,*

, Shiao-Shing Chen³, Sih-Yin Yang³, Hui-Ming Liu¹ and Kuang-Shan Lin³

¹ Department of Safety, Health and Environmental Engineering, Hungkuang University, Taichung 43302, Taiwan

² Hsuteng Consulting International Co., Ltd. Taichung 40764, Taiwan

³ Institute of Environment Engineering and Management, National Taipei University of Technology, Taipei 10643, Taiwan

Materials 2018, 11(6), 939; https://doi.org/10.3390/ma11060939 - 3 Jun 2018

Cited by 32 | Viewed by 4669

Abstract

Using Ti(OC₄H₉)₄ as a precursor, Fe(NO₃)₃⋅9H₂O as the source of iron, and NH₄NO₃ as the source of nitrogen, an Fe/N codoped TiO₂ catalyst was prepared using a sol-gel [...] Read more.

Using Ti(OC₄H₉)₄ as a precursor, Fe(NO₃)₃⋅9H₂O as the source of iron, and NH₄NO₃ as the source of nitrogen, an Fe/N codoped TiO₂ catalyst was prepared using a sol-gel hydrothermal method. The as-prepared powders were characterized using X-ray powder diffraction, electron spectroscopy for chemical analysis, Fourier-transform infrared spectroscopy, and ultraviolet-visible spectrophotometry. Fe and N codoping resulted in decreased crystallite size and increased specific surface area. Results of the photocatalytic degradation of acid orange 7 (AO7) in a continuous-flow fluidized-bed reactor indicated that the maximum decolorization (more than 90%) of AO7 occurred with the Fe/N-TiO₂ catalyst (dosage of 20 g/L) when a combination of visible light irradiation for 10 h HRT (hydraulic retention time), and a heterogeneous system was used. The AO7 degradation efficiency was considerably improved by increasing the hydraulic retention time from 2.5 to 10 h or by reducing the initial AO7 concentration from 300 to 100 mg/L. The reaction rate increased with the light intensity and the maximum value occurred at 35 mW/cm²; moreover, the efficiency of the AO7 degradation increased when the pH decreased with maximum efficiency at pH 3. Full article

(This article belongs to the Special Issue Novel Photoactive Materials)

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12 pages, 2975 KiB

Open AccessArticle

Active Enhancement of Slow Light Based on Plasmon-Induced Transparency with Gain Materials

by Zhaojian Zhang¹, Junbo Yang^2,*, Xin He², Yunxin Han², Jingjing Zhang¹, Jie Huang¹, Dingbo Chen¹ and Siyu Xu¹

¹ College of Liberal Arts and Sciences, National University of Defense Technology, Changsha 410073, China

² Center of Material Science, National University of Defense Technology, Changsha 410073, China

Materials 2018, 11(6), 941; https://doi.org/10.3390/ma11060941 - 3 Jun 2018

Cited by 18 | Viewed by 4186

Abstract

As a plasmonic analogue of electromagnetically induced transparency (EIT), plasmon-induced transparency (PIT) has drawn more attention due to its potential of realizing on-chip sensing, slow light and nonlinear effect enhancement. However, the performance of a plasmonic system is always limited by the metal [...] Read more.

As a plasmonic analogue of electromagnetically induced transparency (EIT), plasmon-induced transparency (PIT) has drawn more attention due to its potential of realizing on-chip sensing, slow light and nonlinear effect enhancement. However, the performance of a plasmonic system is always limited by the metal ohmic loss. Here, we numerically report a PIT system with gain materials based on plasmonic metal-insulator-metal waveguide. The corresponding phenomenon can be theoretically analyzed by coupled mode theory (CMT). After filling gain material into a disk cavity, the system intrinsic loss can be compensated by external pump beam, and the PIT can be greatly fueled to achieve a dramatic enhancement of slow light performance. Finally, a double-channel enhanced slow light is introduced by adding a second gain disk cavity. This work paves way for a potential new high-performance slow light device, which can have significant applications for high-compact plasmonic circuits and optical communication. Full article

(This article belongs to the Special Issue New Horizon of Plasmonics and Metamaterials)

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11 pages, 1211 KiB

Open AccessArticle

Plasmonic Au Array SERS Substrate with Optimized Thin Film Oxide Substrate Layer

by Zachary T. Brawley^1,2, Stephen J. Bauman¹, Ahmad A. Darweesh¹, Desalegn T. Debu², Faezeh Tork Ladani² and Joseph B. Herzog^1,2,*

¹ Microelectronics-Photonics Graduate Program, University of Arkansas, 731 W. Dickson St., Fayetteville, Arkansas, AR 72701, USA

² Department of Physics, University of Arkansas, 825 W. Dickson St., Fayetteville, Arkansas, AR 72701, USA

Materials 2018, 11(6), 942; https://doi.org/10.3390/ma11060942 - 4 Jun 2018

Cited by 6 | Viewed by 4464

Abstract

This work studies the effect of a plasmonic array structure coupled with thin film oxide substrate layers on optical surface enhancement using a finite element method. Previous results have shown that as the nanowire spacing increases in the sub-100 nm range, enhancement decreases; [...] Read more.

This work studies the effect of a plasmonic array structure coupled with thin film oxide substrate layers on optical surface enhancement using a finite element method. Previous results have shown that as the nanowire spacing increases in the sub-100 nm range, enhancement decreases; however, this work improves upon previous results by extending the range above 100 nm. It also averages optical enhancement across the entire device surface rather than localized regions, which gives a more practical estimate of the sensor response. A significant finding is that in higher ranges, optical enhancement does not always decrease but instead has additional plasmonic modes at greater nanowire and spacing dimensions resonant with the period of the structure and the incident light wavelength, making it possible to optimize enhancement in more accessibly fabricated nanowire array structures. This work also studies surface enhancement to optimize the geometries of plasmonic wires and oxide substrate thickness. Periodic oscillations of surface enhancement are observed at specific oxide thicknesses. These results will help improve future research by providing optimized geometries for SERS molecular sensors. Full article

(This article belongs to the Special Issue SERS-Active Substrates)

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7 pages, 2823 KiB

Open AccessArticle

Study of the Microstructure, Mechanical, and Magnetic Properties of LaFe_11.6Si_1.4H_y/Bi Magnetocaloric Composites

by Zhengang Liu^1,2

, Qiming Wu¹, Naikun Sun³, Zan Ding¹ and Lingwei Li^1,2,*

¹ Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China

² Institute of Materials Physics and Chemistry, School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China

³ School of Science, Shenyang Ligong University, Shenyang 110159, China

Materials 2018, 11(6), 943; https://doi.org/10.3390/ma11060943 - 4 Jun 2018

Cited by 24 | Viewed by 3060

Abstract

We have successfully synthesized LaFe_11.6Si_1.4H_y/Bi composites by cold pressing together with vacuum annealing technology, and systematically investigated the microstructure, magnetism, mechanical performance, and magnetocaloric properties. LaFe_11.6Si_1.4H_y particles are well surrounded by metallic [...] Read more.

We have successfully synthesized LaFe_11.6Si_1.4H_y/Bi composites by cold pressing together with vacuum annealing technology, and systematically investigated the microstructure, magnetism, mechanical performance, and magnetocaloric properties. LaFe_11.6Si_1.4H_y particles are well surrounded by metallic Bi, without the formation of new phase. The maximum values of the volumetric magnetic entropy change -ΔS_M are as high as 51, 49, and 35 mJ/cm³K around 263 K, for the composites with 5, 10 and 15 wt % Bi contents, respectively. The maximum value of the compressive strength for LaFe_11.6Si_1.4H_y/Bi composites increased continuously from 155 to 358 MPa with increasing Bi content, from 0 to 15 wt %. Full article

(This article belongs to the Section Advanced Composites)

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9 pages, 1553 KiB

Open AccessArticle

Effect of Alpha-Particle Irradiation on InGaP/GaAs/Ge Triple-Junction Solar Cells

by Jing Xu¹, Min Guo¹, Ming Lu^1,*

, Hu He², Guang Yang² and Jianwen Xu²

¹ Department of Physics, Yantai University, 30 Qingquan Road, Laishan District, Yantai 264005, China

² Shanghai Institute of Space Power-Sources, 2965 Dongchuan Road, Minhang District, Shanghai 200233, China

Materials 2018, 11(6), 944; https://doi.org/10.3390/ma11060944 - 4 Jun 2018

Cited by 14 | Viewed by 3814

Abstract

InGaP/GaAs/Ge triple-junction solar cells were irradiated with 5.1 MeV alpha particles with different fluences. The degradations of the optical and electrical properties of InGaP/GaAs/Ge solar cells were described in terms of the variation in the short-circuit current (I_sc), the open-circuit voltage [...] Read more.

InGaP/GaAs/Ge triple-junction solar cells were irradiated with 5.1 MeV alpha particles with different fluences. The degradations of the optical and electrical properties of InGaP/GaAs/Ge solar cells were described in terms of the variation in the short-circuit current (I_sc), the open-circuit voltage (V_oc), the maximum power (P_max), the spectral response (SR), and the photoluminescence (PL) versus the 5.1 MeV alpha-particle fluences. The degradation modeling of the I_sc and V_oc under 1 MeV, 3 MeV, and 5.1 MeV alpha-particle irradiation was performed by calculating the introduction rate of non-radiative recombination centers, and the minority-carrier capture cross section, and the results were in good agreement with experimental data. For comparison, the degradations of the I_sc and V_oc were presented under 1 MeV and 3 MeV proton irradiation. Full article

(This article belongs to the Section Energy Materials)

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14 pages, 20839 KiB

Open AccessArticle

Nanoscale Zero-Valent Iron Decorated on Bentonite/Graphene Oxide for Removal of Copper Ions from Aqueous Solution

by Jicheng Shao^1,†, Xiaoniu Yu^1,†

, Min Zhou¹, Xiaoqing Cai^2,* and Chuang Yu¹

¹ College of Civil Engineering and Architecture, Wenzhou University, Wenzhou 325035, China

² College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China

^† These authors contributed equally to this work.

Materials 2018, 11(6), 945; https://doi.org/10.3390/ma11060945 - 4 Jun 2018

Cited by 35 | Viewed by 4139

Abstract

The removal efficiency of Cu(II) in aqueous solution by bentonite, graphene oxide (GO), and nanoscale iron decorated on bentonite (B-nZVI) and nanoscale iron decorated on bentonite/graphene oxide (GO-B-nZVI) was investigated. The results indicated that GO-B-nZVI had the best removal efficiency in different experimental [...] Read more.

The removal efficiency of Cu(II) in aqueous solution by bentonite, graphene oxide (GO), and nanoscale iron decorated on bentonite (B-nZVI) and nanoscale iron decorated on bentonite/graphene oxide (GO-B-nZVI) was investigated. The results indicated that GO-B-nZVI had the best removal efficiency in different experimental environments (with time, pH, concentration of copper ions, and temperature). For 16 hours, the removal efficiency of copper ions was 82% in GO-B-nZVI, however, it was 71% in B-nZVI, 26% in bentonite, and 18% in GO. Bentonite, GO, B-nZVI, and GO-B-nZVI showed an increased removal efficiency of copper ions with the increase of pH under a certain pH range. The removal efficiency of copper ions by GO-B-nZVI first increased and then fluctuated slightly with the increase of temperature, while B-nZVI and bentonite increased and GO decreased slightly with the increase of temperature. Lorentz-Transmission Electron Microscope (TEM) images showed the nZVI particles of GO-B-nZVI dispersed evenly with diameters ranging from 10 to 86.93 nm. Scanning electron microscope (SEM) images indicated that the nanoscale iron particles were dispersed evenly on bentonite and GO with no obvious agglomeration. The q_e,cal (73.37 mg·g⁻¹ and 83.89 mg·g⁻¹) was closer to the experimental value q_e,exp according to the pseudo-second-order kinetic model. The q_m of B-nZVI and GO-B-nZVI were 130.7 mg·g⁻¹ and 184.5 mg·g⁻¹ according to the Langmuir model. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

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11 pages, 4547 KiB

Open AccessArticle

Crystal Chemistry and Thermoelectric Properties of Type-I Clathrate Ba₈Ni_∼3.8Si_xGe_42.2−x (x = 0, 10, 20, 42.2)

by Yue Dong¹

, Xueyong Ding^1,*, Xinlin Yan^2,*, Long Zhang³, Zhaohui Tang¹, Weiliang Chen¹, Peter Rogl⁴ and Silke Paschen²

¹ School of Metallurgy, Northeastern University, Shenyang 110819, China

² Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstr. 8–10, 1040 Vienna, Austria

³ State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China

⁴ Institute of Materials Chemistry and Research, University of Vienna, Währingerstr. 42, 1090 Vienna, Austria

Materials 2018, 11(6), 946; https://doi.org/10.3390/ma11060946 - 4 Jun 2018

Cited by 3 | Viewed by 4066

Abstract

Thermoelectric materials are actively considered for waste heat recovery applications. To improve the heat to electricity conversion efficiency, fundamental understanding on composition, crystal structure, and interrelation with the thermoelectric properties is necessary. Here, we report the chemical and thermoelectric properties of type-I clathrates [...] Read more.

Thermoelectric materials are actively considered for waste heat recovery applications. To improve the heat to electricity conversion efficiency, fundamental understanding on composition, crystal structure, and interrelation with the thermoelectric properties is necessary. Here, we report the chemical and thermoelectric properties of type-I clathrates Ba

_{8}

Ni

_{3.8}

Si

_{x}

Ge

_{42.2 - x}

(x = 0, 10, 20, 42.2), to show that the Si substitution can retain the low lattice thermal conductivity as in pure Ge-based clathrates by adding defects (cage distortion) scattering and/or alloying effect, and the charge carrier concentration can be optimized and thus the electronic properties can be improved by tailoring the vacancy content. We demonstrate the vacancies in the pure Ge-based compound by Rietveld refinement, and possible vacancies in the quaternary compound by transport property measurements. We also show that, for intrinsic property studies in these compounds with such a complex crystal structure, a heat treatment for as cast alloys is necessary for phase purity and composition homogeneity. The highest

Z T

value of 0.19 at 550

^{°} C

is reached in the compound with

x = 10

. Full article

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10 pages, 3359 KiB

Open AccessArticle

Tunable Mechanical Properties of Ti-Zr-Ni-Cr-V Amorphous Ribbons via Different Melt Spinning Speeds during Rapid Solidification Process

by Bing Jiang^1,2, Jianxin Wang^1,2, Lingfeng Xu^1,2, Chengyuan Qian^1,2, Tiexin Liu³, Jiayu Dai³ and Xueling Hou^1,2,*

¹ Laboratory for Microstructures of Shanghai University, Shanghai 200444, China

² School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China

³ Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China

Materials 2018, 11(6), 947; https://doi.org/10.3390/ma11060947 - 4 Jun 2018

Cited by 12 | Viewed by 3744

Abstract

In this paper, the effects of different melt spinning speeds on the mechanical properties of (TiZr)_0.5(Ni_0.6Cr_0.1V_0.1)_2.1 amorphous ribbons were studied. Tensile tests of the specimens were used to investigate mechanical behavior and mechanical properties [...] Read more.

In this paper, the effects of different melt spinning speeds on the mechanical properties of (TiZr)_0.5(Ni_0.6Cr_0.1V_0.1)_2.1 amorphous ribbons were studied. Tensile tests of the specimens were used to investigate mechanical behavior and mechanical properties of amorphous ribbons. The effects of cooling rate on the glass transition temperature of amorphous ribbons was discussed. The correlation between the microstructure of serrated flow behavior in stress-strain curves and melt spinning speeds of ribbons was also evaluated. In addition, when the spinning speed was 45 m/s, a large number of dense and uniform dimples appeared on the fractured surface of the specimens. Furthermore, characteristics of serrated flow behavior were obvious, which meant that Ti-Zr-Ni-Cr-V amorphous ribbons showed minor plastic behavior. It is assumed that the influence of free volume led to a serrated flow behavior of the amorphous materials, and made the amorphous material exhibit partially plastic properties. Increasing the strain rate sensitivity meant the free volume increased with the increasing spinning speed. Tensile strength (σ_b) and elongation (δ) of samples exhibited a dramatic increasing trend with an increase in the spinning speed. In particular, Ti-Zr-Ni-Cr-V amorphous ribbons showed better mechanical properties, namely the tensile strength of the amorphous ribbon samples significantly increased from 321 MPa at a spinning speed of 30 m/s to 675 MPa at a speed of 45 m/s. The elongation increased from 0.53% at a speed of 30 m/s to 1.29% at a speed of 45 m/s. Full article

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25 pages, 6848 KiB

Open AccessFeature PaperArticle

CO Oxidation at 20 °C on Au Catalysts Supported on Mesoporous Silica: Effects of Support Structural Properties and Modifiers

by Abigail Moreno-Martell¹, Barbara Pawelec^2,*

, Rufino Nava^1,*, Noelia Mota², Luis Escamilla-Perea¹, Rufino M. Navarro² and Jose L.G. Fierro²

¹ Division of Research and Postgraduate Studies, Faculty of Engineering, Universidad Autónoma de Querétaro (UAQ), Cerro de las Campanas s/n, Querétaro 76010, Mexico

² Instituto de Catálisis y Petroleoquímica, CSIC, Marie Curie 2, Cantoblanco, 28049 Madrid, Spain

Materials 2018, 11(6), 948; https://doi.org/10.3390/ma11060948 - 4 Jun 2018

Cited by 8 | Viewed by 5299

Abstract

In this work we report the effects of support structural properties and its modification with some metal oxides modifiers on the catalytic behavior of Au catalysts in the total CO oxidation at 20 °C. Au catalysts were supported on mesoporous silica materials (MSM) [...] Read more.

In this work we report the effects of support structural properties and its modification with some metal oxides modifiers on the catalytic behavior of Au catalysts in the total CO oxidation at 20 °C. Au catalysts were supported on mesoporous silica materials (MSM) having different structural properties: Channel-like (SBA-15), cage-like (SBA-16), hexagonal (HMS), and disordered (DMS-1) structures. The effect of the modifier was evaluated by comparison of the catalytic response of the SBA-15-based catalysts modified with MgO, Fe₂O₃, TiO₂, and CeO₂. The chemical, structural, and electronic properties of the catalysts were investigated by a variety of techniques (metal content analysis by ICP-OES, N₂ physisorption, XRD, UV-vis DRS, DRIFTS of adsorbed CO and OH regions, oxygen storage capacity (OSC), HR-TEM, and XPS). The activity of calcined catalysts in the CO oxidation reaction were evaluated at steady state conditions, at 20 °C, atmospheric pressure, and when using, as feed, a 1%CO/1%O₂/98% gas mixture. The work clearly demonstrated that all Au catalysts supported on the mesoporous silicas modified with metal oxides were more active than the Au/SBA-15 and Au/MgO reference ones. The support structural properties and type of dopant were important factors influencing on the catalyst behavior. Concerning the support textural properties, it was found that the HMS substrate with the wormhole-structure offers better porosity and specific surface area than their silica counterparts having channel-like (SBA-15), cage-like (SBA-16), and disordered (DMS-1) mesoporous structures. Concerning the effect of modifier, the best catalytic response was achieved with the catalysts modified with MgO. After activation by calcination at 200 °C for 4 h, the Au/MgO/HMS catalyst exhibited the best catalytic performance, which was ascribed to the combined effects of the best structural properties, a large support oxygen storage capacity and homogeneous distribution of gold particles on the support (external and inner). Implications of the type of active sites (Au¹⁺ or Au⁰), support structural properties and role of modifier on the catalytic activity are discussed. Full article

(This article belongs to the Special Issue Mesoporous Silica Catalysts)

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10 pages, 2538 KiB

Open AccessFeature PaperArticle

A Study of Quantum Confinement Effects in Ultrathin NiO Films Performed by Experiment and Theory

by Christos S. Garoufalis¹, Alexandros Barnasas¹, Alkeos Stamatelatos¹

, Vagelis Karoutsos¹, Spyridon Grammatikopoulos²

, Panagiotis Poulopoulos¹ and Sotirios Baskoutas^1,*

¹ Department of Materials Science, University of Patras, 26504 Patras, Greece

² Department of Mechanical Engineering, Technological Educational Institute (T.E.I.) of Western Greece, M. Alexandrou 1, 26504 Patras, Greece

Materials 2018, 11(6), 949; https://doi.org/10.3390/ma11060949 - 4 Jun 2018

Cited by 28 | Viewed by 5018

Abstract

Ultrathin NiO films in the thickness range between 1 and 27 nm have been deposited on high-quality quartz substrates by direct magnetron sputtering under a rough vacuum with a base pressure of 2 × 10⁻² mbar. The sputtering target was metallic Ni; [...] Read more.

Ultrathin NiO films in the thickness range between 1 and 27 nm have been deposited on high-quality quartz substrates by direct magnetron sputtering under a rough vacuum with a base pressure of 2 × 10⁻² mbar. The sputtering target was metallic Ni; however, due to the rough vacuum a precursor material was grown in which most of Ni was already oxidized. Subsequent short annealing at temperatures of about 600 °C in a furnace in air resulted in NiO with high crystallinity quality, as atomic force microscopy revealed. The images of surface morphology showed that the NiO films were continuous and follow a normal grain growth mode. UV-Vis light absorption spectroscopy experiments have revealed a blue shift of the direct band gap of NiO. The band gap was determined either by Tauc plots (onset) or by the derivative method (highest rate of absorbance increase just after the onset). The experimental results are interpreted as evidences of quantum confinement effects. Theoretical calculations based on Hartree Fock approximation as applied for an electron-hole system, in the framework of effective mass approximation were carried out. The agreement between theory and experiment supports the quantum confinement interpretation. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials and Their Applications)

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8 pages, 2530 KiB

Open AccessArticle

Experimental Study on Characteristics of Grinded Graphene Nanofluids with Surfactants

by HeonJin Seong¹

, GwiNam Kim²

, JongHoon Jeon¹

, HyoMin Jeong¹

, JungPil Noh¹

, YoungJu Kim³, HyunJi Kim³

and SunChul Huh^1,*

¹ Department of Energy and Mechanical Engineering, Gyeongsang National University, 38, Cheondaegukchi-gil 53064, Tongyeong-si, Korea

² Department of Mechanical & Automotive Engineering, Suncheon Jeil College, 17 Jeildaehak-gil 57997, Suncheon-si, Korea

³ Department of Exploration System Research, KIGAM Pohang Branch, 905, Yeongilman-daero 37559, Pohang-si, Korea

Materials 2018, 11(6), 950; https://doi.org/10.3390/ma11060950 - 4 Jun 2018

Cited by 27 | Viewed by 4123

Abstract

In earlier studies, much research has focused on increasing the efficiency of heat exchanger fields. Therefore, in this study, graphene nanofluid was fabricated for use as a heat transfer medium for a heat exchanger. Graphene has excellent electrical conductivity, mechanical properties, and heat [...] Read more.

In earlier studies, much research has focused on increasing the efficiency of heat exchanger fields. Therefore, in this study, graphene nanofluid was fabricated for use as a heat transfer medium for a heat exchanger. Graphene has excellent electrical conductivity, mechanical properties, and heat transfer properties. It is expected that the heat transfer efficiency will be improved by fabricating the nanofluid. However, graphene is prone to sedimentation, because of its cohesion due to van der Waals binding force. In this experiment, a nanofluid was fabricated with enhanced dispersibility by surfactant and the ball-milling process. The zeta potential, absorbance, and thermal conductivity of the nanofluid were measured. As a result, when using the ratio of 2:1 (graphene:sodium dodecyl sulfate (SDS)), a higher thermal conductivity was obtained than in other conditions. Full article

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8 pages, 897 KiB

Open AccessArticle

Analysis of Indium Oxidation State on the Electronic Structure and Optical Properties of TiO₂

by Matiullah Khan^1,2,3

, Zhenghua Lan² and Yi Zeng^1,*

¹ State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

² Shanghai Career Metallurgy Furnace Material Co., Ltd., Shanghai 201908, China

³ Department of Physics, Kohat University of Science and Technology (KUST), Kohat 26000, Pakistan

Materials 2018, 11(6), 952; https://doi.org/10.3390/ma11060952 - 5 Jun 2018

Cited by 11 | Viewed by 3887

Abstract

Due to the high formation energy of Indium interstitial defect in the TiO₂ lattice, the most probable location for Indium dopant is substitutional sites. Replacing Ti by In atom in the anatase TiO₂ shifted the absorption edge of TiO₂ towards [...] Read more.

Due to the high formation energy of Indium interstitial defect in the TiO₂ lattice, the most probable location for Indium dopant is substitutional sites. Replacing Ti by In atom in the anatase TiO₂ shifted the absorption edge of TiO₂ towards visible regime. Indium doping tuned the band structure of TiO₂ via creating In 5p states. The In 5p states are successfully coupled with the O 2p states reducing the band gap. Increasing In doping level in TiO₂ improved the visible light absorption. Compensating the charge imbalance by oxygen vacancy provided compensated Indium doped TiO₂ model. The creation of oxygen vacancy widened the band gap, blue shifted the absorption edge of TiO₂ and declined the UV light absorption. The 2.08% In in TiO₂ is the optimal Indium doping concentration, providing suitable band structure for the photoelectrochemical applications and stable geometrical configuration among the simulated models. Our results provide a reasonable explanation for the improved photoactivity of Indium doped TiO₂. Full article

(This article belongs to the Section Energy Materials)

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9 pages, 5287 KiB

Open AccessArticle

Formation of Cl-Doped ZnO Thin Films by a Cathodic Electrodeposition for Use as a Window Layer in CIGS Solar Cells

by Jianping Ao¹, Rui Fu¹, Ming-Jer Jeng^2,3,*, Jinlian Bi¹, Liyong Yao¹, Shoushuai Gao¹, Guozhong Sun¹, Qing He¹, Zhiqiang Zhou¹, Yun Sun¹ and Liann-Be Chang^2,3

¹ Institute of Photoelectronic Thin Film Devices and Technology and Tianjin Key Laboratory of Thin film Devices and Technology, Nankai University, Tianjin 300071, China

² Department of Electronic Engineering, Chang Gung University, Kweishan, Taoyuan 333, Taiwan

³ Department of Otolaryngology-Head and Neck Surgery, Chang Gung Memorial Hospital, Kweishan, Taoyuan 333, Taiwan

Materials 2018, 11(6), 953; https://doi.org/10.3390/ma11060953 - 5 Jun 2018

Cited by 10 | Viewed by 4002

Abstract

Zinc oxide films that are prepared by radio frequency (RF) sputtering are widely used as window layers in copper indium gallium diselenide (CIGS) solar cells. To reduce their production cost, the electrodeposition method for preparing Cl-doped zinc oxide (ZnO:Cl), rather than sputtering, was [...] Read more.

Zinc oxide films that are prepared by radio frequency (RF) sputtering are widely used as window layers in copper indium gallium diselenide (CIGS) solar cells. To reduce their production cost, the electrodeposition method for preparing Cl-doped zinc oxide (ZnO:Cl), rather than sputtering, was studied. The electrodeposition parameters of injected current density and the pH of the electrolyte solution were studied. A moderate current density was used to yield high quality zinc oxides. The pH of the electrolyte greatly affected the formation of ZnO films. The pH value of the electrolyte that ensured that zinc oxides of high quality are obtained was close to seven. Electrodeposited ZnO:Cl films had higher transmittance than ZnO:Al films in the near-infrared region and so they can be used to improve the performance of solar cells. Our experiments revealed that the CIGS solar cells with electrodeposited ZnO:Cl films as a window layer were slightly more efficient than those with sputtered ZnO:Al films. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2018)

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10 pages, 5244 KiB

Open AccessArticle

Applying of Pulsed Electromagnetic Processing of Melts in Laboratory and Industrial Conditions

by Valeriy Krymsky^* and Nataliya Shaburova^*

Polytechnical Institute, South Ural State University, Lenin Avenue, 76, Chelyabinsk 454080, Russia

Materials 2018, 11(6), 954; https://doi.org/10.3390/ma11060954 - 5 Jun 2018

Cited by 13 | Viewed by 2800

Abstract

The use of various external influences to influence metal melts (vibration, ultrasound, etc.) is a known method of changing the structure and properties of metals and alloys. In the overwhelming majority, all methods of external action on melts cause grinding of the metal [...] Read more.

The use of various external influences to influence metal melts (vibration, ultrasound, etc.) is a known method of changing the structure and properties of metals and alloys. In the overwhelming majority, all methods of external action on melts cause grinding of the metal structure, which leads to an increase in strength characteristics. The paper considers a new method of external physical action on molten metal, namely, electromagnetic pulses. Work on the investigation of the impulse effect on metal melts is conducted in two laboratories: in Chelyabinsk (the laboratory of Professor Krymsky V.V.) and in Khabarovsk (in the laboratory of Ri Josen). If at the beginning only small masses of metal were processed in the laboratory, now the work is at the industrial level. Masses of processed metal reach 2 tons. The article summarizes and structures the results of the conducted studies on the effect on nonferrous metal melts with powerful electromagnetic pulses. General regularities of such influence on the structure and properties of the metal are established. The results of such effects on pure metals (aluminum, zinc) and on aluminum alloys are provided. It is established that impulse processing contributes to a decrease in the porosity of castings, an increase in metal density, and a decrease in electrical resistivity. Also, in pulsed processing, a grinding of the metal grains occurs, an increase in the solubility of the main components in the alpha phase, and changes for the eutectic in the structure. An interesting fact is the simultaneous increase in the properties of the strength and plasticity of the metal. Full article

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8 pages, 1886 KiB

Open AccessArticle

E-Textile Embroidered Metamaterial Transmission Line for Signal Propagation Control

by Bahareh Moradi^*, Raul Fernández-García

and Ignacio Gil^*

Department of Electronic Engineering, Universitat Politècnica de Catalunya, Terrassa 08222, Barcelona, Spain

Materials 2018, 11(6), 955; https://doi.org/10.3390/ma11060955 - 5 Jun 2018

Cited by 29 | Viewed by 5907

Abstract

In this paper, the utilization of common fabrics for the manufacturing of e-textile metamaterial transmission lines is investigated. In order to filter and control the signal propagation in the ultra-high frequency (UHF) range along the e-textile, a conventional metamaterial transmission line was compared [...] Read more.

In this paper, the utilization of common fabrics for the manufacturing of e-textile metamaterial transmission lines is investigated. In order to filter and control the signal propagation in the ultra-high frequency (UHF) range along the e-textile, a conventional metamaterial transmission line was compared with embroidered metamaterial particles. The proposed design was based on a transmission line loaded with one or several split-ring resonators (SRR) on a felt substrate. To explore the relations between physical parameters and filter performance characteristics, theoretical models based on transmission matrices’ description of the filter constituent components were proposed. Excellent agreement between theoretical prediction, electromagnetic simulations, and measurement were found. Experimental results showed stop-band levels higher than −30 dB for compact embroidered metamaterial e-textiles. The validated results confirmed embroidery as a useful technique to obtain customized electromagnetic properties, such as filtering, on wearable applications. Full article

(This article belongs to the Special Issue Novel Smart Textiles)

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13 pages, 3815 KiB

Open AccessArticle

Wide-Band Circularly Polarized ReflectarrayUsing Graphene-Based Pancharatnam-Berry Phase Unit-Cells for Terahertz Communication

by Li Deng^*

, Yuanyuan Zhang, Jianfeng Zhu and Chen Zhang

Beijing Key Laboratory of Network System Architecture and Convergence, School of Information and Communication Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China

Materials 2018, 11(6), 956; https://doi.org/10.3390/ma11060956 - 5 Jun 2018

Cited by 19 | Viewed by 4564

Abstract

A wide-band and high gain circularly polarized (CP) graphene-based reflectarray operating in the THz regime is proposed and theoretically investigated in this paper. The proposed reflectarray consists of a THz CP source and several graphene-based unit-cells. Taking advantages of the Pancharatnam Berry (PB) [...] Read more.

A wide-band and high gain circularly polarized (CP) graphene-based reflectarray operating in the THz regime is proposed and theoretically investigated in this paper. The proposed reflectarray consists of a THz CP source and several graphene-based unit-cells. Taking advantages of the Pancharatnam Berry (PB) phase principle, the graphene-based unit-cell is capable of realizing a tunable phase range of 360° in a wide-band (1.4–1.7 THz) by unit-cell rotating, overcoming the restriction of intrinsic narrow-band resonance in graphene. Therefore, this graphene-based unit-cell exhibits superior bandwidth and phase tunability to its previous counterparts. To demonstrate this, a wide-band (1.4–1.7 THz) focusing metasurface based on the proposed unit-cell that exhibits excellent focusing effect was designed. Then, according to the reversibility of the optical path, a CP reflectarray was realized by placing a wide-band CP THz source at the focal point of the metasurface. Numerical simulation demonstrates that this reflectarray can achieve a stable high gain up to 15 dBic and an axial ratio around 2.1 dB over the 1.4–1.7 THz band. The good radiation performance of the proposed CP reflectarray, as demonstrated, underlines its suitability for the THz communication applications. Moreover, the design principle of this graphene-based reflectarray with a full 360° phase range tunable unit-cells provides a new pathway to design high-performance CP reflectarray in the THz regime. Full article

(This article belongs to the Section Carbon Materials)

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14 pages, 5254 KiB

Open AccessArticle

Conjectured the Behaviour of a Recycled Metal Matrix Composite (MMC–Al_R) Developed through Hot Press Forging by Means of 3D FEM Simulation

by Azlan Ahmad¹

, Mohd Amri Lajis^2,*, Shazarel Shamsudin² and Nur Kamilah Yusuf²

¹ Department of Mechanical Engineering, Universiti Teknologi PETRONAS, Seri Iskandar 32610, Perak Darul Ridzuan, Malaysia

² Sustainable Manufacturing and Recycling Technology, Advanced Manufacturing, and Materials Center (SMART-AMMC), Universiti Tun Hussein Onn Malaysia, Parit Raja 86400, Batu Pahat, Johor, Malaysia

Materials 2018, 11(6), 958; https://doi.org/10.3390/ma11060958 - 6 Jun 2018

Cited by 11 | Viewed by 3542

Abstract

Melting aluminium waste to produce a secondary bulk material is such an energy-intensive recycling technique that it also indirectly threatens the environment. Hot press forging is introduced as an alternative. Mixing the waste with another substance is a proven practice that enhances the [...] Read more.

Melting aluminium waste to produce a secondary bulk material is such an energy-intensive recycling technique that it also indirectly threatens the environment. Hot press forging is introduced as an alternative. Mixing the waste with another substance is a proven practice that enhances the material integrity. To cope with the technology revolution, a finite element is utilised to predict the behaviour without a practical trial. Utilising commercial software, DEFORM 3D, the conjectures were demonstrated scientifically. The flow stress of the material was modified to suit the material used in the actual experiment. It is acknowledged that the stress–strain had gradually increased in each step. Due to the confined forming space, the temperature decreased by ~0.5% because the heat could not simply vacate the area. A reduction of ~10% of the flesh observed in the simulation is roughly the same as in the actual experiment. Above all, the simulation abides by the standards and follows what has been done previously. Through the finite element utilisation, this study forecasted the performance of the recycled composite. The results presented may facilitate improvement of the recycling issue and conserve the environment for a better future. Full article

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11 pages, 4361 KiB

Open AccessArticle

Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel

by Zhenshun Li^1,*, Xuemin Zhao¹ and Dongri Shan²

¹ Engineering Training Center, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China

² School of Mechanical and Automotive Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China

Materials 2018, 11(6), 959; https://doi.org/10.3390/ma11060959 - 6 Jun 2018

Cited by 11 | Viewed by 4356

Abstract

The subzones of the intercritical heat-affected zone (IC HAZ) of low-carbon bainitic steel were simulated by using a Gleeble-3500 simulator to study the impact toughness. The results showed that the IC HAZ is not entirely brittle and can be further divided into three [...] Read more.

The subzones of the intercritical heat-affected zone (IC HAZ) of low-carbon bainitic steel were simulated by using a Gleeble-3500 simulator to study the impact toughness. The results showed that the IC HAZ is not entirely brittle and can be further divided into three subzones according to the impact toughness or peak welding temperature; the invariant subzone heated between the critical transformation start temperature (A_c1) and 770 °C exhibited unchanged high impact toughness. Furthermore, an extremely low impact toughness was found in the embrittlement subzone, heated between 770 and 830 °C, and the reduction subzone heated between 830 °C and the critical transformation finish temperature (A_c3) exhibited toughness below that of the original metal. The size of the blocky martensite-austenite (M-A) constituents was found to have a remarkable level of influence on the impact toughness when heated below 830 °C. Additionally, it was found that, once the constituent size exceeds a critical value of 3.0 µm at a peak temperature of 770 °C, the IC HAZ becomes brittle regardless of lath or twinned martensite constitution in the M-A constituent. Essentially, embrittlement was observed to occur when the resolved length of initial cracks (in the direction of the overall fracture) formed as a result of the debonding of M-A constituents exceeding the critical Griffith size. Furthermore, when the heating temperature exceeded 830 °C, the M-A constituents formed a slender shape, and the impact toughness increased as the area fraction of the slender M-A constituents decreased. Full article

(This article belongs to the Section Advanced Materials Characterization)

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14 pages, 7450 KiB

Open AccessArticle

Investigation of Groove Shape Variation during Steel Sheave Spinning

by Chengcheng Zhu^1,2,*

, Dean Meng^1,3,4,*, Shengdun Zhao¹

and Shuaipeng Li¹

¹ School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049, China

² Department of Mechanical Engineering, National University of Singapore, Singapore 119260, Singapore

³ School of Mechanical Engineering, Northwest Polytechnical University, Xi’an 710072, China

⁴ School of Engineering Technology, Purdue University, 401 N. Grant Street, West Lafayette, IN 47906, USA

Materials 2018, 11(6), 960; https://doi.org/10.3390/ma11060960 - 6 Jun 2018

Cited by 5 | Viewed by 3334

Abstract

Large sheaves, such as crosshead sheaves, are foundation parts in the heavy industry. Counter-roller spinning steel sheaves are utilized to replace traditional casting iron parts. Few studies exist on the groove shape of these spinning sheaves. Consequently, it is significant to explore the [...] Read more.

Large sheaves, such as crosshead sheaves, are foundation parts in the heavy industry. Counter-roller spinning steel sheaves are utilized to replace traditional casting iron parts. Few studies exist on the groove shape of these spinning sheaves. Consequently, it is significant to explore the spinning groove shape variation rule and confirm the appropriate spinning parameters. Both experimental and numerical methods were utilized to study the groove shape variation of Q235 steel sheaves and their results were well matched. Spring-back phenomena were considered in this study. The groove depth was lower than the spinning depth and the last formed groove was the deepest. The former groove depth would be affected by the adjacent following spinning process. The single groove spinning result was linearly dependent on the multiple spinning groove depth. Certain equations were used to calculate the groove depth. The bottom–middle–top spinning sequence, which was better than other spinning sequences, should be used in the sheave spinning method. A sheave spinning process could be designed based on the study to obtain a fine groove shape. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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13 pages, 9235 KiB

Open AccessArticle

Copper-Doped Bioactive Glass as Filler for PMMA-Based Bone Cements: Morphological, Mechanical, Reactivity, and Preliminary Antibacterial Characterization

by Marta Miola¹, Andrea Cochis^2,3

, Ajay Kumar², Carla Renata Arciola^4,5

, Lia Rimondini^2,†

and Enrica Verné^1,*,†

¹ Department of Applied Science and Technology, Politecnico di Torino, 10129 Torino, Italy

² Department of Health Sciences, Università del Piemonte Orientale UPO, 28100 Novara, Italy

³ Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), 28100 Novara, Italy

⁴ Research Unit on Implant Infections, Rizzoli Orthopaedic Institute, 40136 Bologna, Italy

⁵ Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, 40126 Bologna, Italy

^† Co-shared authorship.

Materials 2018, 11(6), 961; https://doi.org/10.3390/ma11060961 - 6 Jun 2018

Cited by 45 | Viewed by 6314

Abstract

To promote osteointegration and simultaneously limit bacterial contamination without using antibiotics, we designed innovative composite cements containing copper (Cu)-doped bioactive glass powders. Cu-doped glass powders were produced by a melt and quenching process, followed by an ion-exchange process in a Cu salt aqueous [...] Read more.

To promote osteointegration and simultaneously limit bacterial contamination without using antibiotics, we designed innovative composite cements containing copper (Cu)-doped bioactive glass powders. Cu-doped glass powders were produced by a melt and quenching process, followed by an ion-exchange process in a Cu salt aqueous solution. Cu-doped glass was incorporated into commercial polymethyl methacrylate (PMMA)-based cements with different viscosities. The realized composites were characterized in terms of morphology, composition, leaching ability, bioactivity, mechanical, and antibacterial properties. Glass powders appeared well distributed and exposed on the PMMA surface. Composite cements showed good bioactivity, evidencing hydroxyapatite precipitation on the sample surfaces after seven days of immersion in simulated body fluid. The leaching test demonstrated that composite cements released a significant amount of copper, with a noticeable antibacterial effect toward Staphylococcus epidermidis strain. Thus, the proposed materials represent an innovative and multifunctional tool for orthopedic prostheses fixation, temporary prostheses, and spinal surgery. Full article

(This article belongs to the Special Issue State-of-the-Art Materials Science in Italy 2017)

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17 pages, 4056 KiB

Open AccessArticle

Fast-Response and Reusable Oxytetracycline Colorimetric Strips Based on Nickel (II) Ions Immobilized Carboxymethylcellulose/Polyacrylonitrile Nanofibrous Membranes

by Mohammed Awad Abedalwafa^1,2

, Yan Li^1,*

, De Li¹, Xiaojun Lv¹ and Lu Wang^1,*

¹ Key Laboratory of Textile Science and Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai 200336, China

² Department of Technical Textile, Faculty of Industries Engineering and Technology, University of Gezira, Wad Madani 21111, Sudan

Materials 2018, 11(6), 962; https://doi.org/10.3390/ma11060962 - 6 Jun 2018

Cited by 6 | Viewed by 4244

Abstract

Driven by economic interests, the abuse of antibiotics has become a significant concern for humans worldwide. As one of the most commonly used antibiotics, oxytetracycline (OTC) residue in animal-derived foods occurs occasionally, which has caused danger to humanity. However, there is still no [...] Read more.

Driven by economic interests, the abuse of antibiotics has become a significant concern for humans worldwide. As one of the most commonly used antibiotics, oxytetracycline (OTC) residue in animal-derived foods occurs occasionally, which has caused danger to humanity. However, there is still no simple and efficient solution to detect OTC residue. Here, an easily-operated colorimetric strategy for OTC detection was developed based on nickel ions (Ni²⁺) immobilized carboxymethylcellulose/polyacrylonitrile nanofibrous membranes (Ni@CMC/PAN NFMs). Owing to numerous O- and N-containing groups OTC has a strong tendency to complex with Ni²⁺ on the strips, inducing a color change from light green to yellow visible to the naked eye. The NFMs structural features, CMC functionalization process, and Ni²⁺ immobilization amount was carefully regulated to assure OTC detection whilst maintaining the inherent characteristics of NFMs. With the benefits of the large specific surface area (SSA) and small pore size of NFMs, the strips not only exhibited a rapid response (2 min), and low detection limit (5 nM) but also performed with good reversibility and selectivity concerning OTC detection over other antibiotics. The successful development of such enchanting nanofibrous materials may provide a new comprehension into the design and improvement of colorimetric strips. Full article

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9 pages, 8644 KiB

Open AccessArticle

Effect of Acetic Acid Concentration on Pore Structure for Mesoporous Bioactive Glass during Spray Pyrolysis

by Bo-Jiang Hong, Chih-Wei Hsiao, Fufa Fetene Bakare, Jung-Ting Sun and Shao-Ju Shih^*

Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan

Materials 2018, 11(6), 963; https://doi.org/10.3390/ma11060963 - 6 Jun 2018

Cited by 18 | Viewed by 3512

Abstract

Mesoporous bioactive glass (MBG) is considered as one of the most important materials in the field of bone implants and drug carriers, owing to its superior bioactivity. In previous studies, tri-block surfactants (e.g., F127 and P123) were commonly used as pore-forming agents. However, [...] Read more.

Mesoporous bioactive glass (MBG) is considered as one of the most important materials in the field of bone implants and drug carriers, owing to its superior bioactivity. In previous studies, tri-block surfactants (e.g., F127 and P123) were commonly used as pore-forming agents. However, the use of surfactants may cause serious problems such as micelle aggregation and carbon contamination and thus decrease bioactivity. Therefore, in this study, we demonstrated the synthesis of MBG using acetic acid (HAc) as a pore-forming agent to overcome the disadvantages caused by surfactants. Both untreated and HAc-treated BG powders were synthesized using spray pyrolysis and various characterizations were carried out. The results show that a mesoporous structure was successfully formed and the highest specific surface area of ~230 m²/g with improved bioactivity was reported. Full article

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9 pages, 3102 KiB

Open AccessArticle

Plasmon-Induced Transparency Based on Triple Arc-Ring Resonators

by Guang-Xi Dong¹, Qin Xie¹, Qi Zhang¹, Ben-Xin Wang^1,*

and Wei-Qing Huang^2,*

¹ School of Science, Jiangnan University, Wuxi 214122, China

² School of Physics and Electronics, Hunan University, Changsha 410082, China

Materials 2018, 11(6), 964; https://doi.org/10.3390/ma11060964 - 6 Jun 2018

Cited by 8 | Viewed by 3296

Abstract

This paper presents a plasmon-induced transparency (PIT) using an easy-fabricating metamaterial composed of three pieces of metallic arc-rings on top of a dielectric substrate. The transmission of the transparent peak of 1.32 THz reaches approximately 93%. The utilization of the coupled Lorentzian oscillator [...] Read more.

This paper presents a plasmon-induced transparency (PIT) using an easy-fabricating metamaterial composed of three pieces of metallic arc-rings on top of a dielectric substrate. The transmission of the transparent peak of 1.32 THz reaches approximately 93%. The utilization of the coupled Lorentzian oscillator model and the distribution of electromagnetic fields together explain the cause of the transparent peak. The simulation results further demonstrate that the bandwidth of the transmission peak can be narrowed by changing the sizes of the arc-rings. Moreover, an on/off effect based on the transparent peak is discussed by introducing photosensitive silicon into the air gaps of the suggested metamaterial structure. Full article

(This article belongs to the Section Advanced Materials Characterization)

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18 pages, 5871 KiB

Open AccessArticle

Long-Term Atmospheric Corrosion Behavior of Epoxy Prime Coated Aluminum Alloy 7075-T6 in Coastal Environment

by Sheng Zhang¹, Yuting He^1,*

, Teng Zhang¹, Guirong Wang² and Xu Du¹

¹ Aeronautics Engineering College, Air Force Engineering University, Xi’an 710038, China

² College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China

Materials 2018, 11(6), 965; https://doi.org/10.3390/ma11060965 - 7 Jun 2018

Cited by 28 | Viewed by 4049

Abstract

The atmospheric corrosion of epoxy prime coated aluminum alloy 7075-T6 exposed for 7, 12 and 20 years was investigated. The remaining thicknesses of epoxy prime coatings for macroscopically intact coating areas followed a normal distribution and decreased linearly. EIS results demonstrated that the [...] Read more.

The atmospheric corrosion of epoxy prime coated aluminum alloy 7075-T6 exposed for 7, 12 and 20 years was investigated. The remaining thicknesses of epoxy prime coatings for macroscopically intact coating areas followed a normal distribution and decreased linearly. EIS results demonstrated that the corrosion resistance of the coating decreased with exposure time. After 20 years of exposure, the epoxy coating had lost its protection as cracks existed within the coating and exfoliation corrosion had occurred on the substrate. The substrate was sensitive to exfoliation corrosion through metallographic and TEM analysis. The corrosion products were mainly hydroxides of aluminum. The morphology and chemical compositions of the coating bubbling area and propagation characterizations of exfoliation corrosion were analyzed by SEM, EPMA and EDS. Cracks between the lumps of corrosion products provided the channels for the transmission of corrosion mediums. Furthermore, the mechanical model was proposed to analyze the propagation characterization of exfoliation corrosion. Full article

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17 pages, 3648 KiB

Open AccessArticle

Testing and Optimizing a Stove-Powered Thermoelectric Generator with Fan Cooling

by Youqu Zheng¹, Jiangen Hu², Guoneng Li^1,*, Lingyun Zhu¹ and Wenwen Guo¹

¹ Department of Energy and Environment System Engineering, Zhejiang University of Science and Technology, Hangzhou 310023, China

² Hangzhou YiNeng Power Technology Corporation Limited, Hangzhou 310014, China

Materials 2018, 11(6), 966; https://doi.org/10.3390/ma11060966 - 7 Jun 2018

Cited by 6 | Viewed by 5332

Abstract

In order to provide heat and electricity under emergency conditions in off-grid areas, a stove-powered thermoelectric generator (STEG) was designed and optimized. No battery was incorporated, ensuring it would work anytime, anywhere, as long as combustible materials were provided. The startup performance, power [...] Read more.

In order to provide heat and electricity under emergency conditions in off-grid areas, a stove-powered thermoelectric generator (STEG) was designed and optimized. No battery was incorporated, ensuring it would work anytime, anywhere, as long as combustible materials were provided. The startup performance, power load feature and thermoelectric (TE) efficiency were investigated in detail. Furthermore, the heat-conducting plate thickness, cooling fan selection, heat sink dimension and TE module configuration were optimized. The heat flow method was employed to determine the TE efficiency, which was compared to the predicted data. Results showed that the STEG can supply clean-and-warm air (625 W) and electricity (8.25 W at 5 V) continuously at a temperature difference of 148 °C, and the corresponding TE efficiency was measured to be 2.31%. Optimization showed that the choice of heat-conducting plate thickness, heat sink dimensions and cooling fan were inter-dependent, and the TE module configuration affected both the startup process and the power output. Full article

(This article belongs to the Special Issue Recent Advances in Thermoelectric Materials)

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25 pages, 4970 KiB

Open AccessArticle

Type of Primary Nb₅Si₃ and Precipitation of Nb_ss in αNb₅Si₃ in a Nb-8.3Ti-21.1Si-5.4Mo-4W-0.7Hf (at.%) Near Eutectic Nb-Silicide-Based Alloy

by Conor McCaughey and Panos Tsakiropoulos^*

Department of Materials Science and Engineering, The University of Sheffield, Hadfield Building, Mappin Street, Sheffield S1 3JD, UK

Materials 2018, 11(6), 967; https://doi.org/10.3390/ma11060967 - 7 Jun 2018

Cited by 24 | Viewed by 3843

Abstract

The Nb-silicide-based alloy of near eutectic composition (at.%) Nb-21.1Si-8.3Ti-5.4Mo-4W-0.7Hf (alloy CM1) was studied in the cast and heat-treated (1500 °C/100 h) conditions. The alloy was produced in the form of buttons and bars using three different methods, namely arc-melting, arc-melting and suction casting, [...] Read more.

The Nb-silicide-based alloy of near eutectic composition (at.%) Nb-21.1Si-8.3Ti-5.4Mo-4W-0.7Hf (alloy CM1) was studied in the cast and heat-treated (1500 °C/100 h) conditions. The alloy was produced in the form of buttons and bars using three different methods, namely arc-melting, arc-melting and suction casting, and optical floating zone (OFZ) melting. In the former two cases the alloy solidified in water-cooled copper crucibles. Buttons and suction-cast bars of different size, respectively of 10 g and 600 g weight and 6 mm and 8 mm diameter, were produced. The OFZ bars were grown at three different growth rates of 12, 60 and 150 mm/h. It was confirmed that the type of Nb₅Si₃ formed in the cast microstructures depended on the solidification conditions. The primary phase in the alloy CM1 was the βNb₅Si₃. The transformation of βNb₅Si₃ to αNb₅Si₃ had occurred in the as cast large size button and the OFZ bars grown at the three different growth rates, and after the heat treatment of the small size button and the suction-cast bars of the alloy. This transformation was accompanied by subgrain formation in Nb₅Si₃ and the precipitation of Nb_ss in the large size as cast button and only by the precipitation of Nb_ss in the cast OFZ bars. Subgrains and precipitation of Nb_ss in αNb₅Si₃ was observed in the small size button and suction-cast bars after the heat treatment. Subgrains formed in αNb₅Si₃ after the heat treatment of the OFZ bars. The partitioning of solutes and in particular of Mo and Ti was key to this phase transformation. Subgrain formation was not necessary for precipitation of Nb_ss in αNb₅Si₃, but the partitioning of solutes was essential for this precipitation. Full article

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9 pages, 1608 KiB

Open AccessArticle

Microstructure and Mechanical Properties of TiC_0.7N_0.3-HfC-WC-Ni-Mo Cermet Tool Materials

by Jiaojiao Gao^1,2, Jinpeng Song^1,2,* and Ming Lv^1,2,*

¹ School of Mechanical Engineering, Taiyuan University of Technology, Taiyuan 030024, China

² Shanxi Key Laboratory of Precision Machining, The Shanxi Science and Technology Department, Taiyuan University of Technology, Taiyuan 030024, China

Materials 2018, 11(6), 968; https://doi.org/10.3390/ma11060968 - 8 Jun 2018

Cited by 13 | Viewed by 3557

Abstract

TiC_0.7N_0.3-HfC-WC-Ni-Mo cermet tool materials were fabricated by hot pressing technology at 1450 °C. The effects of WC (tungsten carbide) content on the microstructure and mechanical properties of TiC_0.7N_0.3-HfC-WC-Ni-Mo cermet tool materials were investigated. The results [...] Read more.

TiC_0.7N_0.3-HfC-WC-Ni-Mo cermet tool materials were fabricated by hot pressing technology at 1450 °C. The effects of WC (tungsten carbide) content on the microstructure and mechanical properties of TiC_0.7N_0.3-HfC-WC-Ni-Mo cermet tool materials were investigated. The results showed that the TiC_0.7N_0.3-HfC-WC-Ni-Mo cermets were mainly composed of TiC_0.7N_0.3, Ni, and (Ti, Hf, W, Mo)(C, N); there were three phases: a dark phase, a gray phase, and a light gray phase. The dark phase was the undissolved TiC_0.7N_0.3, the gray phase was the solid solution (Ti, Hf, W, Mo)(C, N) poor in Hf, W, and Mo, and the light gray phase was the solid solution (Ti, Hf, W, Mo)(C, N) rich in Hf, W, and Mo. The increase of WC content could promote the process of HfC to form a solid solution and the HfC formed a solid solution more easily with WC than with TiCN. The increase of the solid solution made the microstructure more uniform and the mechanical properties better. In addition, the Vickers hardness, flexural strength, and fracture toughness of the TiC_0.7N_0.3-HfC-WC-Ni-Mo cermet increased with the increase of WC content. When the content of WC was 32 wt %, the cermet obtained the optimal comprehensive mechanical properties in this investigation. The toughening mechanism of TiC_0.7N_0.3-HfC-WC-Ni-Mo cermet tool materials included solid solution toughening, particle dispersion toughening, crack bridging, and crack deflection. Full article

(This article belongs to the Section Advanced Composites)

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10 pages, 3379 KiB

Open AccessArticle

Thermal Conductivity and High-Frequency Dielectric Properties of Pressureless Sintered SiC-AlN Multiphase Ceramics

by Jialin Gu

, Lingling Sang, Bo Pan, Yongbao Feng, Jian Yang and Xiaoyun Li^*

State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China

Materials 2018, 11(6), 969; https://doi.org/10.3390/ma11060969 - 8 Jun 2018

Cited by 22 | Viewed by 5188

Abstract

SiC-AlN multiphase ceramics with 10 wt. %Y₂O₃-BaO-SiO₂ additives were fabricated by pressureless sintering in a nitrogen atmosphere. The effects of SiC contents and sintering temperatures on the sinterability, microstructure, thermal conductivity and high-frequency dielectric properties were characterized. In [...] Read more.

SiC-AlN multiphase ceramics with 10 wt. %Y₂O₃-BaO-SiO₂ additives were fabricated by pressureless sintering in a nitrogen atmosphere. The effects of SiC contents and sintering temperatures on the sinterability, microstructure, thermal conductivity and high-frequency dielectric properties were characterized. In addition to 6H-SiC and AlN, the samples also contained Y₃Al₅O₁₂ and Y₄Al₂O₉. SiC-AlN ceramics sintered with 50 wt. % SiC at 2173 K exhibited the best thermal diffusivity and thermal conductivity (26.21 mm²·s⁻¹ and 61.02 W·m⁻¹·K⁻¹, respectively). The dielectric constant and dielectric loss of the sample sintered with 50 wt. % SiC and 2123 K were 33–37 and 0.4–0.5 at 12.4–18 GHz. The dielectric constant and dielectric loss of the samples decreased as the frequency of electromagnetic waves increased from 12.4–18 GHz. The dielectric thermal conductivity properties of the SiC-AlN samples are discussed. Full article

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18 pages, 7847 KiB

Open AccessArticle

The Corrosion Behavior of AZ91D Magnesium Alloy in Simulated Haze Aqueous Solution

by Liying Cui^1,2, Zhiyong Liu^1,2,*, Peng Hu³, Jiamin Shao^1,2, Xiaogang Li^1,2,4, Cuiwei Du^1,2,4 and Bin Jiang⁵

¹ Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083, China

² Key Laboratory for Corrosion and Protection (MOE), University of Science and Technology Beijing, Beijing 100083, China

³ Key Laboratory of Environment Fracture Ministry of Education, University of Science and Technology Beijing, Beijing 100083, China

⁴ State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China

⁵ College of Materials Science and Engineering, Chongqing University, Chongqing 400030, China

Materials 2018, 11(6), 970; https://doi.org/10.3390/ma11060970 - 8 Jun 2018

Cited by 26 | Viewed by 4075

Abstract

The corrosion process of AZ91D magnesium alloy in simulated haze aqueous solution has been studied by electrochemical measurements, immersion tests and morphology characterization. Results show that AZ91D was corroded heavily in simulated haze aqueous solution due to the loose and breakable product film [...] Read more.

The corrosion process of AZ91D magnesium alloy in simulated haze aqueous solution has been studied by electrochemical measurements, immersion tests and morphology characterization. Results show that AZ91D was corroded heavily in simulated haze aqueous solution due to the loose and breakable product film on the surface providing little corrosion barrier. The effect of different ions was investigated. It was found that both

{N O}_{3}^{-}

and

{N H}_{4}^{+}

played an important role in the corrosion process.

{N O}_{3}^{-}

helped to form passive film to protect the matrix, yet

{N H}_{4}^{+}

consumed OH⁻, resulting in the absence of Mg(OH)₂ and serious corrosion. Meanwhile,

{S O}_{4}^{2 -}

and Cl⁻ had influence on pitting corrosion. Magnesium aluminum oxide and MgAl₂(SO₄)₄·22H₂O instead of Mg(OH)₂ were the dominate products, which is different from the former study. Corrosion rate changed with time, especially in the first 3 h. A two-stage corrosion mechanism is proposed after considering both the corrosion process and the influence of ions. Full article

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16 pages, 8524 KiB

Open AccessArticle

Application of Ti6Al7Nb Alloy for the Manufacture of Biomechanical Functional Structures (BFS) for Custom-Made Bone Implants

by Patrycja Szymczyk^1,*, Grzegorz Ziółkowski¹, Adam Junka²

and Edward Chlebus¹

¹ Center for Advanced Manufacturing Technologies (CAMT/FPC), Faculty of Mechanical Engineering, Wroclaw University of Science and Technology, Łukasiewicza 5, 50-371 Wrocław, Poland

² Department of Pharmaceutical Microbiology and Parasitology, Wrocław Medical University, Borowska 211A, 50-556 Wrocław, Poland

Materials 2018, 11(6), 971; https://doi.org/10.3390/ma11060971 - 8 Jun 2018

Cited by 24 | Viewed by 4867

Abstract

Unlike conventional manufacturing techniques, additive manufacturing (AM) can form objects of complex shape and geometry in an almost unrestricted manner. AM’s advantages include higher control of local process parameters and a possibility to use two or more various materials during manufacture. In this [...] Read more.

Unlike conventional manufacturing techniques, additive manufacturing (AM) can form objects of complex shape and geometry in an almost unrestricted manner. AM’s advantages include higher control of local process parameters and a possibility to use two or more various materials during manufacture. In this work, we applied one of AM technologies, selective laser melting, using Ti6Al7Nb alloy to produce biomedical functional structures (BFS) in the form of bone implants. Five types of BFS structures (A1, A2, A3, B, C) were manufactured for the research. The aim of this study was to investigate such technological aspects as architecture, manufacturing methods, process parameters, surface modification, and to compare them with such functional properties such as accuracy, mechanical, and biological in manufactured implants. Initial in vitro studies were performed using osteoblast cell line hFOB 1.19 (ATCC CRL-11372) (American Type Culture Collection). The results of the presented study confirm high applicative potential of AM to produce bone implants of high accuracy and geometric complexity, displaying desired mechanical properties. The experimental tests, as well as geometrical accuracy analysis, showed that the square shaped (A3) BFS structures were characterized by the lowest deviation range and smallestanisotropy of mechanical properties. Moreover, cell culture experiments performed in this study proved that the designed and obtained implant’s internal porosity (A3) enhances the growth of bone cells (osteoblasts) and can obtain predesigned biomechanical characteristics comparable to those of the bone tissue. Full article

(This article belongs to the Section Biomaterials)

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11 pages, 16607 KiB

Open AccessArticle

Dislocation Based Flow Stress Model of 300M Steel in Isothermal Compression Process

by Rongchuang Chen

, Peng Guo, Zhizhen Zheng^*, Jianjun Li and Fei Feng

State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, China

Materials 2018, 11(6), 972; https://doi.org/10.3390/ma11060972 - 8 Jun 2018

Cited by 17 | Viewed by 4633

Abstract

The relationship between microstructure and flow behaviour has attracted attention from many researchers for the past decades, whilst the influences of dislocation and recrystallization on flow stress have not been well understood, which led to failure in flow stress prediction at high temperature [...] Read more.

The relationship between microstructure and flow behaviour has attracted attention from many researchers for the past decades, whilst the influences of dislocation and recrystallization on flow stress have not been well understood, which led to failure in flow stress prediction at high temperature compressions. In this work, we tried to provide a novel explanation of the relationship between microstructure evolutions and flow behaviour, and the influence of dislocation and recrystallization on flow stress was investigated. A dislocation based flow stress model was proposed and applied for 300M steel at the strain rate of 0.01–10 s⁻¹ and the temperature of 950–1150 °C. Results showed the established model could predict the flow stress both at constant strain rate conditions and at variable strain rate conditions. The present investigation is helpful to a better understanding of hardening and softening mechanisms in hot compression of 300M steel. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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15 pages, 4062 KiB

Open AccessArticle

Dental Resin Cements—The Influence of Water Sorption on Contraction Stress Changes and Hydroscopic Expansion

by Grzegorz Sokolowski¹, Agata Szczesio²

, Kinga Bociong², Karolina Kaluzinska², Barbara Lapinska³

, Jerzy Sokolowski³, Monika Domarecka³ and Monika Lukomska-Szymanska^3,*

¹ Department of Prosthetic Dentistry, Medical University of Lodz, 251 Pomorska St., 92-213 Lodz, Poland

² University Laboratory of Materials Research, Medical University of Lodz, 251 Pomorska St., 92-213 Lodz, Poland

³ Department of General Dentistry, Medical University of Lodz, 251 Pomorska St., 92-213 Lodz, Poland

Materials 2018, 11(6), 973; https://doi.org/10.3390/ma11060973 - 8 Jun 2018

Cited by 53 | Viewed by 7475

Abstract

Resin matrix dental materials undergo contraction and expansion changes due to polymerization and water absorption. Both phenomena deform resin-dentin bonding and influence the stress state in restored tooth structure in two opposite directions. The study tested three composite resin cements (Cement-It, NX3, Variolink [...] Read more.

Resin matrix dental materials undergo contraction and expansion changes due to polymerization and water absorption. Both phenomena deform resin-dentin bonding and influence the stress state in restored tooth structure in two opposite directions. The study tested three composite resin cements (Cement-It, NX3, Variolink Esthetic DC), three adhesive resin cements (Estecem, Multilink Automix, Panavia 2.0), and seven self-adhesive resin cements (Breeze, Calibra Universal, MaxCem Elite Chroma, Panavia SA Cement Plus, RelyX U200, SmartCem 2, and SpeedCEM Plus). The stress generated at the restoration-tooth interface during water immersion was evaluated. The shrinkage stress was measured immediately after curing and after 0.5 h, 24 h, 72 h, 96 h, 168 h, 240 h, 336 h, 504 h, 672 h, and 1344 h by means of photoelastic study. Water sorption and solubility were also studied. All tested materials during polymerization generated shrinkage stress ranging from 4.8 MPa up to 15.1 MPa. The decrease in shrinkage strain (not less than 57%) was observed after water storage (56 days). Self-adhesive cements, i.e., MaxCem Elite Chroma, SpeedCem Plus, Panavia SA Plus, and Breeze exhibited high values of water expansion stress (from 0 up to almost 7 MPa). Among other tested materials only composite resin cement Cement It and adhesive resin cement Panavia 2.0 showed water expansion stress (1.6 and 4.8, respectively). The changes in stress value (decrease in contraction stress or built up of hydroscopic expansion) in time were material-dependent. Full article

(This article belongs to the Special Issue Bioactive and Therapeutic Dental Materials)

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10 pages, 1432 KiB

Open AccessArticle

On the Shaping of a Short Signal at the Output of the Receiving Piezoelectric Transducer in the Radiation-Reception System

by Boris Ee, Roman Konovalov

, Sergey Konovalov^*

, Andrey Kuz’menko and Valery Tsaplev

Department of Electroacoustics and Ultrasonic Engineering, Saint Petersburg Electrotechnical University “LETI”, Prof. Popov, 5, Saint Petersburg 197376, Russia

Materials 2018, 11(6), 974; https://doi.org/10.3390/ma11060974 - 8 Jun 2018

Cited by 3 | Viewed by 3993

Abstract

This paper theoretically and experimentally considers the pulsed mode of operation of the radiation-receiving system. The system contains two identical piezoceramic plates separated by a layer of immersion liquid (glycerin). The emitter was excited by the complex electrical signal of the special shape, [...] Read more.

This paper theoretically and experimentally considers the pulsed mode of operation of the radiation-receiving system. The system contains two identical piezoceramic plates separated by a layer of immersion liquid (glycerin). The emitter was excited by the complex electrical signal of the special shape, which consisted of two half-cycles of the sine wave (exciting and compensating) on the natural frequency of the piezoplates. The forms of these signals were calculated by the authors and described in their previous papers using the d’Alembert method. The length of the electrical signal was estimated at the output of the piezoelectric receiver. The problem was solved theoretically using the finite element method. The acoustical system was simulated with the help of the COMSOL Multiphysics modeling environment. A comparative study of the theoretical and experimental results is carried out. The form of the signal at the output of the system was calculated by the d’Alembert method, and the simulated form by the finite element method was in good coincidence with the results of experimental and full-scale modeling. It is shown that the usage of complex waveforms allows achieving a significant pulse duration reduction of the electrical voltage at the output of the receiver. Full article

(This article belongs to the Special Issue Smart Materials in 2018: Overview and Applications)

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11 pages, 2623 KiB

Open AccessArticle

The Effect of Buffer Types on the In_0.82Ga_0.18As Epitaxial Layer Grown on an InP (100) Substrate

by Min Zhang^1,2, Zuoxing Guo^1,2, Liang Zhao², Shen Yang² and Lei Zhao^1,*

¹ Key Laboratory of Automobile Materials (Ministry of Education), Jilin University, Changchun 130025, China

² College of Materials Science and Engineering, Jilin University, Nanling Campus, Changchun 130025, China

Materials 2018, 11(6), 975; https://doi.org/10.3390/ma11060975 - 8 Jun 2018

Cited by 5 | Viewed by 3337

Abstract

In_0.82Ga_0.18As epitaxial layers were grown on InP (100) substrates at 530 °C by a low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique. The effects of different buffer structures, such as a single buffer layer, compositionally graded buffer layers, and superlattice [...] Read more.

In_0.82Ga_0.18As epitaxial layers were grown on InP (100) substrates at 530 °C by a low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique. The effects of different buffer structures, such as a single buffer layer, compositionally graded buffer layers, and superlattice buffer layers, on the crystalline quality and property were investigated. Double-crystal X-ray diffraction (DC-XRD) measurement, Raman scattering spectrum, and Hall measurements were used to evaluate the crystalline quality and electrical property. Scanning electron microscope (SEM), atomic force microscope (AFM), and transmission electron microscope (TEM) were used to characterize the surface morphology and microstructure, respectively. Compared with the In_0.82Ga_0.18As epitaxial layer directly grown on an InP substrate, the quality of the sample is not obviously improved by using a single In_0.82Ga_0.18As buffer layer. By introducing the graded In_xGa_1−xAs buffer layers, it was found that the dislocation density in the epitaxial layer significantly decreased and the surface quality improved remarkably. In addition, the number of dislocations in the epitaxial layer greatly decreased under the combined action of multi-potential wells and potential barriers by the introduction of a In_0.82Ga_0.18As/In_0.82Al_0.18As superlattice buffer. However, the surface subsequently roughened, which may be explained by surface undulation. Full article

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9 pages, 2197 KiB

Open AccessArticle

Magnesium Potassium Phosphate Compound for Immobilization of Radioactive Waste Containing Actinide and Rare Earth Elements

by Sergey E. Vinokurov^*, Svetlana A. Kulikova and Boris F. Myasoedov

Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19 Kosygin st., Moscow 119991, Russia

Materials 2018, 11(6), 976; https://doi.org/10.3390/ma11060976 - 8 Jun 2018

Cited by 25 | Viewed by 4724

Abstract

The problem of effective immobilization of liquid radioactive waste (LRW) is key to the successful development of nuclear energy. The possibility of using the magnesium potassium phosphate (MKP) compound for LRW immobilization on the example of nitric acid solutions containing actinides and rare [...] Read more.

The problem of effective immobilization of liquid radioactive waste (LRW) is key to the successful development of nuclear energy. The possibility of using the magnesium potassium phosphate (MKP) compound for LRW immobilization on the example of nitric acid solutions containing actinides and rare earth elements (REE), including high level waste (HLW) surrogate solution, is considered in the research work. Under the study of phase composition and structure of the MKP compounds that is obtained by the XRD and SEM methods, it was established that the compounds are composed of crystalline phases—analogues of natural phosphate minerals (struvite, metaankoleite). The hydrolytic stability of the compounds was determined according to the semi-dynamic test GOST R 52126-2003. Low leaching rates of radionuclides from the compound are established, including a differential leaching rate of ²³⁹Pu and ²⁴¹Am—3.5 × 10⁻⁷ and 5.3 × 10⁻⁷ g/(cm²∙day). As a result of the research work, it was concluded that the MKP compound is promising for LRW immobilization and can become an alternative material combining the advantages of easy implementation of the technology, like cementation and the high physical and chemical stability corresponding to a glass-like compound. Full article

(This article belongs to the Special Issue Materials for Nuclear Waste Immobilization)

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18 pages, 7815 KiB

Open AccessArticle

Ballistic Performance of Nanostructured Metals Toughened by Elliptical Coarse-Grained Inclusions: A Finite Element Study with Failure Analysis

by Xiang Guo^1,2,3,*

, Qidong Ouyang⁴, Yubo Sun¹ and George J. Weng⁵

¹ School of Mechanical Engineering, Tianjin University, Tianjin 300072, China

² Tianjin Key Laboratory of Nonlinear Dynamics and Control, Tianjin 300072, China

³ State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an 710049, China

⁴ Jiangsu Testing Center for Quality of Construction Engineering Co., Ltd., Nanjing 210028, China

⁵ Department of Mechanical and Aerospace Engineering, Rutgers University, New Brunswick, NJ 08903, USA

Materials 2018, 11(6), 977; https://doi.org/10.3390/ma11060977 - 8 Jun 2018

Cited by 2 | Viewed by 3980

Abstract

Bimodal nanostructured (NS) metals, in which the nano-grains or ultrafine grains serve as matrix phase while the coarse grains serve as toughening phase, can synergize the overall strength and ductility to achieve excellent bullet-proof performance. Because of the extrusion process in the fabrication, [...] Read more.

Bimodal nanostructured (NS) metals, in which the nano-grains or ultrafine grains serve as matrix phase while the coarse grains serve as toughening phase, can synergize the overall strength and ductility to achieve excellent bullet-proof performance. Because of the extrusion process in the fabrication, the coarse-grained (CG) inclusions are elongated in the extrusion direction and elliptical CG inclusions with different aspect ratios form. The shape, distribution, and volume fraction of these elliptical CG inclusions can all have significant influence on the overall ballistic performance. In this study, the strain gradient plasticity model together with the Johnson–Cook failure criterion is employed to investigate the ballistic performance of the bimodal NS Cu with elliptical CG inclusions. Our results show that the ballistic performance can be improved by increasing the aspect ratio of the elliptical CG inclusions. Furthermore, the staggered distribution of the elliptical CG inclusions will decrease the overall ability of the material to resist failure, but it will improve its overall ability to resist deformation. The larger stagger degree of elliptical CG inclusions can weaken their shape effects on the limit displacement. Full article

(This article belongs to the Special Issue Deformation, Fatigue and Fracture of Materials)

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25 pages, 5233 KiB

Open AccessArticle

Nanoscale Electrical Potential and Roughness of a Calcium Phosphate Surface Promotes the Osteogenic Phenotype of Stromal Cells

by Igor A. Khlusov^1,2,*

, Yuri Dekhtyar³, Yurii P. Sharkeev^4,5, Vladimir F. Pichugin⁴, Marina Y. Khlusova⁶, Nataliya Polyaka³, Fedor Tyulkin³, Viktorija Vendinya³, Elena V. Legostaeva⁵, Larisa S. Litvinova²

, Valeria V. Shupletsova², Olga G. Khaziakhmatova², Kristina A. Yurova² and Konstantin A. Prosolov^4,5

¹ Research School of Chemistry & Applied Biomedical Sciences, National Research Tomsk Polytechnic University, Tomsk 634050, Russia

² Basic Laboratory of Immunology and Cell Biotechnology, Immanuel Kant Baltic Federal University, Kaliningrad 236041, Russia

³ Institute of Biomedical Engineering and Nanotechnologies, Riga Technical University, Riga LV-1658, Latvia

⁴ Research School of High-Energy Physics, National Research Tomsk Polytechnic University, Tomsk 634050, Russia

⁵ Institute of Strength Physics and Materials Science of SB RAS, Tomsk 634055, Russia

⁶ Department of Pathophysiology, Siberian State Medical University, Tomsk 634050, Russia

Materials 2018, 11(6), 978; https://doi.org/10.3390/ma11060978 - 9 Jun 2018

Cited by 34 | Viewed by 4754

Abstract

Mesenchymal stem cells (MSCs) and osteoblasts respond to the surface electrical charge and topography of biomaterials. This work focuses on the connection between the roughness of calcium phosphate (CP) surfaces and their electrical potential (EP) at the micro- and nanoscales and the possible [...] Read more.

Mesenchymal stem cells (MSCs) and osteoblasts respond to the surface electrical charge and topography of biomaterials. This work focuses on the connection between the roughness of calcium phosphate (CP) surfaces and their electrical potential (EP) at the micro- and nanoscales and the possible role of these parameters in jointly affecting human MSC osteogenic differentiation and maturation in vitro. A microarc CP coating was deposited on titanium substrates and characterized at the micro- and nanoscale. Human adult adipose-derived MSCs (hAMSCs) or prenatal stromal cells from the human lung (HLPSCs) were cultured on the CP surface to estimate MSC behavior. The roughness, nonuniform charge polarity, and EP of CP microarc coatings on a titanium substrate were shown to affect the osteogenic differentiation and maturation of hAMSCs and HLPSCs in vitro. The surface EP induced by the negative charge increased with increasing surface roughness at the microscale. The surface relief at the nanoscale had an impact on the sign of the EP. Negative electrical charges were mainly located within the micro- and nanosockets of the coating surface, whereas positive charges were detected predominantly at the nanorelief peaks. HLPSCs located in the sockets of the CP surface expressed the osteoblastic markers osteocalcin and alkaline phosphatase. The CP multilevel topography induced charge polarity and an EP and overall promoted the osteoblast phenotype of HLPSCs. The negative sign of the EP and its magnitude at the micro- and nanosockets might be sensitive factors that can trigger osteoblastic differentiation and maturation of human stromal cells. Full article

(This article belongs to the Special Issue Novel Advances and Approaches in Biomedical Materials Based on Calcium Phosphates)

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8 pages, 2012 KiB

Open AccessArticle

An Approach for Measuring the Dielectric Strength of OLED Materials

by Sujith Sudheendran Swayamprabha, Deepak Kumar Dubey, Wei-Chi Song, You-Ting Lin, Rohit Ashok Kumar Yadav, Meenu Singh and Jwo-Huei Jou^*

Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan

Materials 2018, 11(6), 979; https://doi.org/10.3390/ma11060979 - 9 Jun 2018

Cited by 5 | Viewed by 4459

Abstract

Surface roughness of electrodes plays a key role in the dielectric breakdown of thin-film organic devices. The rate of breakdown will increase when there are stochastic sharp spikes on the surface of electrodes. Additionally, surface having spiking morphology makes the determination of dielectric [...] Read more.

Surface roughness of electrodes plays a key role in the dielectric breakdown of thin-film organic devices. The rate of breakdown will increase when there are stochastic sharp spikes on the surface of electrodes. Additionally, surface having spiking morphology makes the determination of dielectric strength very challenging, specifically when the layer is relatively thin. We demonstrate here a new approach to investigate the dielectric strength of organic thin films for organic light-emitting diodes (OLEDs). The thin films were deposited on a substrate using physical vapor deposition (PVD) under high vacuum. The device architectures used were glass substrate/indium tin oxide (ITO)/organic material/aluminum (Al) and glass substrate/Al/organic material/Al. The dielectric strength of the OLED materials was evaluated from the measured breakdown voltage and layer thickness. Full article

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14 pages, 1326 KiB

Open AccessArticle

Protective Carbon Overlayers from 2,3-Naphthalenediol Pyrolysis on Mesoporous SiO₂ and Al₂O₃ Analyzed by Solid-State NMR

by Pu Duan¹

, Xiaoyan Cao¹, Hien Pham², Abhaya Datye²

and Klaus Schmidt-Rohr^1,*

¹ Department of Chemistry, Brandeis University, Waltham, MA 02453, USA

² Department of Chemical & Biological Engineering and Center for Microengineered Materials, University of New Mexico, Albuquerque, NM 87131, USA

Materials 2018, 11(6), 980; https://doi.org/10.3390/ma11060980 - 9 Jun 2018

Cited by 4 | Viewed by 4558

Abstract

Hydrothermally stable carbon overlayers can protect mesoporous oxides (SiO₂ and Al₂O₃) from hydrolysis during aqueous-phase catalysis. Overlayers made at 800 °C by pyrolysis of 2,3-naphthalenediol deposited out of acetone solution were analyzed by solid-state ¹³C nuclear magnetic [...] Read more.

Hydrothermally stable carbon overlayers can protect mesoporous oxides (SiO₂ and Al₂O₃) from hydrolysis during aqueous-phase catalysis. Overlayers made at 800 °C by pyrolysis of 2,3-naphthalenediol deposited out of acetone solution were analyzed by solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy. Power absorption due to sample conductivity was prevented by diluting the sample in nonconductive and background-free tricalcium phosphate. While pyrolysis on SiO₂ produced a predominantly aromatic carbon film, at least 15% of nonaromatic carbon (sp³-hybridized C as well as C=O) was observed on γ-Al₂O₃. These species were not derived from residual solvent, according to spectra of the same material treated at 400 °C. The sp³-hybridized C exhibited weak couplings to hydrogen, short spin-lattice relaxation times, and unusually large shift anisotropies, which are characteristics of tetrahedral carbon with high concentrations of unpaired electrons. Moderate heat treatment at 400 °C on SiO₂ and Al₂O₃ resulted in yellow-brown and nearly black samples, respectively, but the darker color on Al₂O₃ did not correspond to more extensive carbonization. Aromatic carbon bonded to hydrogen remained predominant and the peaks of naphthalenediol were still recognizable; however, some of the chemical shifts differed by up to 5 ppm, indicating significant differences in local structure. On SiO₂, additional sharp peaks were detected and attributed to 1/3 of the 2,3-naphthalene molecules undergoing fast, nearly isotropic motions. Full article

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8 pages, 2912 KiB

Open AccessArticle

Trial of an All-Ceramic SnO₂ Gas Sensor Equipped with CaCu₃Ru₄O₁₂ Heater and Electrode

by Akihiro Tsuruta^1,*

, Toshio Itoh¹, Masashi Mikami¹

, Yoshiaki Kinemuchi¹, Ichiro Terasaki^1,2

, Norimitsu Murayama³ and Woosuck Shin¹

¹ National Institute of Advanced Industrial Science and Technology (AIST), Shimo-Shidami, Moriyama-ku, Nagoya 463-8560, Japan

² Department of Physics, Nagoya University, Furo-cho, Chuikusa-ku, Nagoya 464-8602, Japan

³ National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8565, Japan

Materials 2018, 11(6), 981; https://doi.org/10.3390/ma11060981 - 11 Jun 2018

Cited by 10 | Viewed by 3550

Abstract

We have constructed a gas sensor of SnO₂ equipped with ceramic electrodes and a heater made of CaCu₃Ru₄O₁₂, which demonstrated good device performance at high temperature. The CaCu₃Ru₄O₁₂-based electrodes and [...] Read more.

We have constructed a gas sensor of SnO₂ equipped with ceramic electrodes and a heater made of CaCu₃Ru₄O₁₂, which demonstrated good device performance at high temperature. The CaCu₃Ru₄O₁₂-based electrodes and heater were formed on Al₂O₃ substrates using a screen-printing process, which is cost-effective and suitable for mass-production. This all-ceramic device reached 600 °C at the lowest, and remained intact after one week of operation at 500 °C and rapid thermal cycling of 500 °C temperature changes within 10 s. We propose CaCu₃Ru₄O₁₂ as a robust and reliable conducting material that can be a substitute for Pt in various devices. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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19 pages, 6449 KiB

Open AccessArticle

Investigation of the Microstructure and Mechanical Properties of Copper-Graphite Composites Reinforced with Single-Crystal α-Al₂O₃ Fibres by Hot Isostatic Pressing

by Guihang Zhang¹, Xiaosong Jiang^1,*

, ChangJun Qiao², Zhenyi Shao¹, Degui Zhu¹, Minhao Zhu¹ and Victor Valcarcel²

¹ School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan, China

² Tsinghua Innovation Center in Dongguan, Advanced Composite Materials Research Department, Dongguan 523808, Guangdong, China

Materials 2018, 11(6), 982; https://doi.org/10.3390/ma11060982 - 11 Jun 2018

Cited by 26 | Viewed by 4757

Abstract

Single-crystal α-Al₂O₃ fibres can be utilized as a novel reinforcement in high-temperature composites owing to their high elastic modulus, chemical and thermal stability. Unlike non-oxide fibres and polycrystalline alumina fibres, high-temperature oxidation and polycrystalline particles boundary growth will not occur [...] Read more.

Single-crystal α-Al₂O₃ fibres can be utilized as a novel reinforcement in high-temperature composites owing to their high elastic modulus, chemical and thermal stability. Unlike non-oxide fibres and polycrystalline alumina fibres, high-temperature oxidation and polycrystalline particles boundary growth will not occur for single-crystal α-Al₂O₃ fibres. In this work, single-crystal α-Al₂O₃ whiskers and Al₂O₃ particles synergistic reinforced copper-graphite composites were fabricated by mechanical alloying and hot isostatic pressing techniques. The phase compositions, microstructures, and fracture morphologies of the composites were investigated using X-ray diffraction, a scanning electron microscope equipped with an X-ray energy-dispersive spectrometer (EDS), an electron probe microscopic analysis equipped with wavelength-dispersive spectrometer, and a transmission electron microscope equipped with EDS. The mechanical properties have been measured by a micro-hardness tester and electronic universal testing machine. The results show that the reinforcements were unevenly distributed in the matrix with the increase of their content and there were some micro-cracks located at the interface between the reinforcement and the matrix. With the increase of the Al₂O₃ whisker content, the compressive strength of the composites first increased and then decreased, while the hardness decreased. The fracture and strengthening mechanisms of the composite materials were explored on the basis of the structure and composition of the composites through the formation and function of the interface. The main strengthening mechanism in the composites was fine grain strengthening and solid solution strengthening. The fracture type of the composites was brittle fracture. Full article

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17 pages, 7726 KiB

Open AccessArticle

Influence of Water Solute Exposure on the Chemical Evolution and Rheological Properties of Asphalt

by Ling Pang, Xuemei Zhang, Shaopeng Wu, Yong Ye^* and Yuanyuan Li

State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China

Materials 2018, 11(6), 983; https://doi.org/10.3390/ma11060983 - 11 Jun 2018

Cited by 78 | Viewed by 4977

Abstract

The properties of asphalt pavement are damaged under the effects of moisture. The pH value and salt concentration of water are the key factors that affect the chemical and rheological properties of asphalt during moisture damage. Four kinds of water solutions, including distilled [...] Read more.

The properties of asphalt pavement are damaged under the effects of moisture. The pH value and salt concentration of water are the key factors that affect the chemical and rheological properties of asphalt during moisture damage. Four kinds of water solutions, including distilled water, an acidic solution, alkaline solution and saline solution were used to investigate the effects of aqueous solute compositions on the chemical and rheological properties of asphalt. Thin-layer chromatography with flame ionization detection (TLC-FID), Fourier transform infrared (FTIR) spectroscopy and dynamic shear rheometer (DSR) were applied to investigate the components, chemistry and rheology characteristics of asphalt specimens before and after water solute exposure. The experimental results show that moisture damage of asphalt is not only associated with an oxidation process between asphalt with oxygen, but it is also highly dependent on some compounds of asphalt dissolving and being removed in the water solutions. In detail, after immersion in water solute, the fraction of saturates, aromatics and resins in asphalt binders decreased, while asphaltenes increased; an increase in the carbonyl and sulphoxide indices, and a decrease in the butadiene index were also found from the FTIR analyzer test. The rheological properties of asphalt are sensitive to water solute immersing. The addition of aqueous solutes causes more serious moisture damage on asphalt binders, with the pH11 solution presenting as the most destructive during water solute exposure. Full article

(This article belongs to the Special Issue Environment-Friendly Construction Materials)

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10 pages, 44684 KiB

Open AccessArticle

The Particle Shape of WC Governing the Fracture Mechanism of Particle Reinforced Iron Matrix Composites

by Zulai Li¹, Pengfei Wang¹, Quan Shan^1,*, Yehua Jiang¹, He Wei¹ and Jun Tan^1,2,*

¹ School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China

² College of Materials Science and Engineering, Chongqing University, Chongqing 400030, China

Materials 2018, 11(6), 984; https://doi.org/10.3390/ma11060984 - 11 Jun 2018

Cited by 20 | Viewed by 4056

Abstract

In this work, tungsten carbide particles (WC_p, spherical and irregular particles)-reinforced iron matrix composites were manufactured utilizing a liquid sintering technique. The mechanical properties and the fracture mechanism of WC_p/iron matrix composites were investigated theoretically and experimentally. The crack [...] Read more.

In this work, tungsten carbide particles (WC_p, spherical and irregular particles)-reinforced iron matrix composites were manufactured utilizing a liquid sintering technique. The mechanical properties and the fracture mechanism of WC_p/iron matrix composites were investigated theoretically and experimentally. The crack schematic diagram and fracture simulation diagram of WC_p/iron matrix composites were summarized, indicating that the micro-crack was initiated both from the interface for spherical and irregular WC_p/iron matrix composites. However, irregular WC_p had a tendency to form spherical WC_p. The micro-cracks then expanded to a wide macro-crack at the interface, leading to a final failure of the composites. In comparison with the spherical WC_p, the irregular WC_p were prone to break due to the stress concentration resulting in being prone to generating brittle cracking. The study on the fracture mechanisms of WC_p/iron matrix composites might provide a theoretical guidance for the design and engineering application of particle reinforced composites. Full article

(This article belongs to the Special Issue Damage Detection and Characterization of High Performance Composites)

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11 pages, 4430 KiB

Open AccessArticle

Magnetic Properties and Spontaneous Polarization of La-, Mn- and N-Doped Tetragonal BiFeO₃: A First-Principles Study

by Qiuhong Tan^1,2, Qianjin Wang^1,2,* and Yingkai Liu^1,2

¹ College of Physics and Electronic Information, Yunnan Normal University, Kunming 650500, China

² Yunnan Provincial Key Laboratory for Photoelectric Information Technology, Yunnan Normal University, Kunming 650500, China

Materials 2018, 11(6), 985; https://doi.org/10.3390/ma11060985 - 11 Jun 2018

Cited by 12 | Viewed by 4825

Abstract

Multiferroic materials have been receiving attention for their potential applications in multifunctional devices. Chemical substitution is an effective method for improving the physical properties of BiFeO₃ (BFO). However, different experimental results have been reported for Lanthanum- (La-) and Manganese (Mn) -doped BFO [...] Read more.

Multiferroic materials have been receiving attention for their potential applications in multifunctional devices. Chemical substitution is an effective method for improving the physical properties of BiFeO₃ (BFO). However, different experimental results have been reported for Lanthanum- (La-) and Manganese (Mn) -doped BFO ceramics. Here, we systematically studied the magnetic properties and spontaneous polarization of La-, Mn-, and Nitrogen (N) -doped tetragonal BiFeO₃ using density functional theory with the generalized gradient approximation and U-value method. The calculated results demonstrated that the systems show ferromagnetism with Mn and N doping, whereas no magnetization was found with La doping in G- and C-type antiferromagnetic orderings. Our research further revealed that the ferromagnetism is attributed to the p-d orbital hybridization. Berry-phase polarization calculations predicted a large polarization of 149.2 µC/cm² along the [001] direction of pure tetragonal BFO. We found that La and N substitution had little influence on the spontaneous polarization, whereas Mn substitution reduced the spontaneous polarization. The reduced energy barrier heights of the doped systems indicate the reduced stability of the off-centering ferroelectricity against the thermal agitation. These findings provide greater understanding for controlling and tuning the multiferroic properties of BFO. Full article

(This article belongs to the Special Issue New Developments in Ferromagnetic Materials)

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9 pages, 4273 KiB

Open AccessArticle

Microstructure and Properties of Thermal Electrode Material Si₃N₄–MoSi₂ Composite Ceramics

by Lichao Feng^1,2,*, Pengfei Guan¹, Xuemei Yu^1,2 and Yiqiang He¹

¹ School of Mechanical and Ocean Engineering, Huaihai Institute of Technology, Lianyungang 222005, China

² Marine Resources Development Institute of Jiangsu, Lianyungang 222001, China

Materials 2018, 11(6), 986; https://doi.org/10.3390/ma11060986 - 11 Jun 2018

Cited by 3 | Viewed by 3344

Abstract

With good high temperature and corrosive resistance performance, ceramic based composites can be used as promising materials to replace metal thermocouple materials. In this study, Si₃N₄–MoSi₂ composites were prepared via hot pressing technology. X-ray diffraction (XRD), optical microscopy [...] Read more.

With good high temperature and corrosive resistance performance, ceramic based composites can be used as promising materials to replace metal thermocouple materials. In this study, Si₃N₄–MoSi₂ composites were prepared via hot pressing technology. X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM) were used to analyze the microstructure of the composites. The mechanical properties and electrical conductivity were tested. The results showed that the composites were composed of β-Si₃N₄, MoSi₂, a small amount of Mo₅Si₃, and an amorphous glassy phase. The MoSi₂ phase was evenly distributed in the matrix. The percolation network was formed with increasing MoSi₂ content. The strength of the composites reached its maximum value when the MoSi₂ content reached a critical point. The electrical conductivity behaved like a typical percolation phenomenon. The percolation threshold was about 30% to 45%. Full article

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11 pages, 6167 KiB

Open AccessArticle

Rapid Sintering of Li₂O-Nb₂O₅-TiO₂ Solid Solution by Air Pressure Control and Clarification of Its Mechanism

by Hiromi Nakano^1,2,*, Konatsu Kamimoto², Takahisa Yamamoto³ and Yoshio Furuta⁴

¹ Cooperative Research Facility Center, Toyohashi University of Technology, Toyohashi 441-8580, Aichi, Japan

² Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi 441-8580, Aichi, Japan

³ Department of Materials Design Innovation Engineering, Nagoya University, Nagoya 464-8603, Aichi, Japan

⁴ FULL-TECH FURNACE Co., Ltd., Yao 581-0037, Osaka, Japan

Materials 2018, 11(6), 987; https://doi.org/10.3390/ma11060987 - 11 Jun 2018

Cited by 6 | Viewed by 4081

Abstract

We first successfully synthesized Li_1+x−yNb_1−x−3yTi_x_+4yO₃ (LNT) solid solutions (0.13 ≤ x ≤ 0.18, 0 ≤ y ≤ 0.06) rapidly at 1373 K for one hour under 0.35 MPa [...] Read more.

We first successfully synthesized Li_1+x−yNb_1−x−3yTi_x_+4yO₃ (LNT) solid solutions (0.13 ≤ x ≤ 0.18, 0 ≤ y ≤ 0.06) rapidly at 1373 K for one hour under 0.35 MPa by the controlling of air pressure using an air-pressure control atmosphere furnace. The composition is a formation area of a superstructure for LNT, in which the periodical intergrowth layer was formed in the matrix, and where it can be controlled by Ti content. Therefore, the sintering time depended on Ti content, and annealing was repeated for over 24 h until a homogeneous structure was formed using a conventional electric furnace. We clarified the mechanism of the rapid sintering using various microscale to nanoscale characterization techniques: X-ray diffraction, a scanning electron microscope, a transmission electron microscope (TEM), a Cs-corrected scanning TEM equipped with electron energy-loss spectroscopy, and X-ray absorption fine structure spectroscopy. Full article

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15 pages, 30722 KiB

Open AccessArticle

Wheat Straw-Derived N-, O-, and S-Tri-doped Porous Carbon with Ultrahigh Specific Surface Area for Lithium-Sulfur Batteries

by Feng Chen¹, Lulu Ma¹, Jiangang Ren¹, Mou Zhang¹, Xinyu Luo², Bing Li¹, Zhiming Song^1,* and Xiangyang Zhou^2,*

¹ School of Resource and Environment, Henan University of Engineering, No. 1, Xianghe Road, Zhengzhou 451191, China

² School of Metallurgy and Environment, Central South University, Lushan South Street 932, Yuelu District, Changsha 410083, China

Materials 2018, 11(6), 989; https://doi.org/10.3390/ma11060989 - 11 Jun 2018

Cited by 32 | Viewed by 5054

Abstract

Recently, lithium-sulfur (Li-S) batteries have been greeted by a huge ovation owing to their very high theoretical specific capacity (1675 mAh·g⁻¹) and theoretical energy density (2600 Wh·kg⁻¹). However, the full commercialization of Li-S batteries is still hindered by dramatic [...] Read more.

Recently, lithium-sulfur (Li-S) batteries have been greeted by a huge ovation owing to their very high theoretical specific capacity (1675 mAh·g⁻¹) and theoretical energy density (2600 Wh·kg⁻¹). However, the full commercialization of Li-S batteries is still hindered by dramatic capacity fading resulting from the notorious “shuttle effect” of polysulfides. Herein, we first describe the development of a facile, inexpensive, and high-producing strategy for the fabrication of N-, O-, and S-tri-doped porous carbon (NOSPC) via pyrolysis of natural wheat straw, followed by KOH activation. The as-obtained NOSPC shows characteristic features of a highly porous carbon frame, ultrahigh specific surface area (3101.8 m²·g⁻¹), large pore volume (1.92 cm³·g⁻¹), good electrical conductivity, and in situ nitrogen (1.36 at %), oxygen (7.43 at %), and sulfur (0.7 at %) tri-doping. The NOSPC is afterwards selected to fabricate the NOSPC-sulfur (NOSPC/S) composite for the Li-S batteries cathode material. The as-prepared NOSPC/S cathode delivers a large initial discharge capacity (1049.2 mAh·g⁻¹ at 0.2 C), good cycling stability (retains a reversible capacity of 454.7 mAh·g⁻¹ over 500 cycles at 1 C with a low capacity decay of 0.088% per cycle), and superior rate performance (619.2 mAh·g⁻¹ at 2 C). The excellent electrochemical performance is mainly attributed to the synergistic effects of structural restriction and multidimensional chemical adsorptions for cooperatively repressing the polysulfides shuttle. Full article

(This article belongs to the Collection Advanced Biomass-Derived Carbon Materials)

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15 pages, 4607 KiB

Open AccessArticle

Preparation of a Porous, Sintered and Reaction-Bonded Si₃N₄ (SRBSN) Planar Membrane for Filtration of an Oil-in-Water Emulsion with High Flux Performance

by Lin Li¹, Er-Ze Gao¹, Hamidreza Abadikhah¹, Jun-Wei Wang¹, Lu-Yuan Hao¹, Xin Xu^1,* and Simeon Agathopoulos²

¹ Chinese Academy of Sciences Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China

² Materials Science and Engineering Department, University of Ioannina, GR-451 10 Ioannina, Greece

Materials 2018, 11(6), 990; https://doi.org/10.3390/ma11060990 - 11 Jun 2018

Cited by 17 | Viewed by 3787

Abstract

A porous, sintered, and reaction-bonded Si₃N₄ (SRBSN) planar membrane was prepared by phase-inversion tape-casting, nitridation (at 1350 °C), and sintering (at 1650 °C) of silicon slurry. The membrane was comprised of uniform rod-like β-Si₃N₄ crystals with a [...] Read more.

A porous, sintered, and reaction-bonded Si₃N₄ (SRBSN) planar membrane was prepared by phase-inversion tape-casting, nitridation (at 1350 °C), and sintering (at 1650 °C) of silicon slurry. The membrane was comprised of uniform rod-like β-Si₃N₄ crystals with a large length/diameter ratio and had high porosity and bending strength. The prepared membrane features a typical asymmetric structure with a skin layer, a sponge layer, and finger-like voids and an average pore size of 0.61 μm. A high permeation flux of 367 L m⁻² h⁻¹ and an oil rejection of 88.6% were recorded in oil-in-water emulsion separation experiments. These results suggest that SRBSN membranes have excellent potential for the treatment of oily wastewater. Full article

(This article belongs to the Section Porous Materials)

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11 pages, 1806 KiB

Open AccessFeature PaperCommunication

Cononsolvency Transition of Polymer Brushes: A Combined Experimental and Theoretical Study

by Huaisong Yong^1,2, Sebastian Rauch¹, Klaus-Jochen Eichhorn¹, Petra Uhlmann¹

, Andreas Fery^1,2,* and Jens-Uwe Sommer^1,3,*

¹ Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany

² Institute of Physical Chemistry of Polymeric Materials, Technische Universität Dresden, 01062 Dresden, Germany

³ Institute for Theoretical Physics, Technische Universität Dresden, 01062 Dresden, Germany

Materials 2018, 11(6), 991; https://doi.org/10.3390/ma11060991 - 11 Jun 2018

Cited by 20 | Viewed by 5390

Abstract

In this study, the cononsolvency transition of poly(N-isopropylacrylamide) (PNiPAAm) brushes in aqueous ethanol mixtures was studied by using Vis-spectroscopic ellipsometry (SE) discussed in conjunction with the adsorption-attraction model. We proved that the cononsolvency transition of PNiPAAm brushes showed features of a [...] Read more.

In this study, the cononsolvency transition of poly(N-isopropylacrylamide) (PNiPAAm) brushes in aqueous ethanol mixtures was studied by using Vis-spectroscopic ellipsometry (SE) discussed in conjunction with the adsorption-attraction model. We proved that the cononsolvency transition of PNiPAAm brushes showed features of a volume phase transition, such as a sharp collapse, reaching a maximum decrease in thickness for a very narrow ethanol volume composition range of 15% to 17%. These observations are in agreement with the recently published preferential adsorption model of the cononsolvency effect. Full article

(This article belongs to the Special Issue Temperature-Responsive Polymers)

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12 pages, 29231 KiB

Open AccessArticle

Damping Analysis of Some Inorganic Particles on Poly(butyl-methacrylate)

by Saisai Zhou¹, Chunhua Yang¹, Jia Hu¹, Xianru He^1,* and Rui Zhang^2,*

¹ School of Materials Science and Engineering, Southwest Petroleum University, Chengdu 610500, China

² Institute für Physik, Universitӓt Rostock, Albert-Einstein-Str. 23-24, 18051 Rostock, Germany

Materials 2018, 11(6), 992; https://doi.org/10.3390/ma11060992 - 12 Jun 2018

Cited by 12 | Viewed by 3511

Abstract

Viscoelastic polymers can be used as damping materials to control unexpected vibration and noise through energy dissipation. To investigate the effect of an inorganic filler on damping property, a series of inorganic particles, Ferriferous oxide(Fe₃O₄), Graphene/Fe₃O₄ [...] Read more.

Viscoelastic polymers can be used as damping materials to control unexpected vibration and noise through energy dissipation. To investigate the effect of an inorganic filler on damping property, a series of inorganic particles, Ferriferous oxide(Fe₃O₄), Graphene/Fe₃O₄(GF), and Fe₃O₄ of demagnetization(α-Fe₂O₃) were incorporated into poly(butyl-methacrylate) (PBMA). The effects of the dispersion of particles, as well as the interaction between particles and the PBMA matrix on the damping property of composites, were systematically studied. Results revealed that the addition of three types of particles can effectively improve the damping properties and broaden the effective damping temperature range. Dispersion of α-Fe₂O₃ in the PBMA matrix is better than that of Fe₃O₄. As a result, the damping peak can be increased more. The interaction between GF and the PBMA matrix is stronger than that between Fe₃O₄ and the PBMA. The damping peak of the composites can be suppressed by GF, which is opposite to Fe₃O₄ and α-Fe₂O₃. In addition, glass transition temperature (T_g) of all composites in the study shifted to low temperatures. Full article

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17 pages, 5784 KiB

Open AccessArticle

Investigation of Tensile Creep of a Normal Strength Overlay Concrete

by Martin Drexel^*

, Yvonne Theiner and Günter Hofstetter

Unit for Strength of Materials and Structural Analysis, Institute of Basic Sciences in Engineering Sciences, Innsbruck University, Technikerstr. 13, A-6020 Innsbruck, Austria

Materials 2018, 11(6), 993; https://doi.org/10.3390/ma11060993 - 12 Jun 2018

Cited by 9 | Viewed by 4307

Abstract

The present contribution deals with the experimental investigation of the time-dependent behavior of a typical overlay concrete subjected to tensile stresses. The latter develop in concrete overlays, which are placed on existing concrete structures as a strengthening measure, due to the shrinkage of [...] Read more.

The present contribution deals with the experimental investigation of the time-dependent behavior of a typical overlay concrete subjected to tensile stresses. The latter develop in concrete overlays, which are placed on existing concrete structures as a strengthening measure, due to the shrinkage of the young overlay concrete, which is restrained by the substrate concrete. Since the tensile stresses are reduced by creep, creep in tension is investigated on sealed and unsealed specimens, loaded at different concrete ages. The creep tests as well as the companion shrinkage tests are performed in a climatic chamber at constant temperature and constant relative humidity. Since shrinkage depends on the change of moisture content, the evolution of the mass water content is determined at the center of each specimen by means of an electrolytic resistivity-based system. Together with the experimental results for compressive creep from a previous study, a consistent set of time-dependent material data, determined for the same composition of the concrete mixture and on identical specimens, is now available. It consists of the hygral and mechanical properties, creep and shrinkage strains for both sealed and drying conditions, the respective compliance functions, and the mass water contents in sealed and unsealed, loaded and load-free specimens. Full article

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18 pages, 12693 KiB

Open AccessArticle

Closed Die Upsetting of Aluminum Matrix Composites Reinforced with Molybdenum Disulfide Nanocrystals and Multilayer Graphene, Implemented using the SPS Process—Microstructure Evolution

by Marek Kostecki^*, Mateusz Petrus, Jarosław Woźniak, Tomasz Cygan and Andrzej Olszyna

Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska St. 141, 02-507 Warsaw, Poland

Materials 2018, 11(6), 994; https://doi.org/10.3390/ma11060994 - 12 Jun 2018

Cited by 6 | Viewed by 4830

Abstract

New methods for producing composite materials such as SPS (Spark Plasma Sintering) are becoming more and more popular due to the ease of implementation in industrial conditions and the versatility of the materials used for processing. In order to fully exploit the potential [...] Read more.

New methods for producing composite materials such as SPS (Spark Plasma Sintering) are becoming more and more popular due to the ease of implementation in industrial conditions and the versatility of the materials used for processing. In order to fully exploit the potential of this method, modifications were proposed which consisted in the deliberate induction of deformation during the sintering process. The influence of the manufacturing method on the microstructure of aluminum alloy matrix composites reinforced with layered crystals in the form of nanoflakes was investigated. Composites with the addition of 10 vol % of multilayer graphene and molybdenum disulfide were prepared and their density, hardness, and the influence of the deformation ratio on the changes occurring in the microstructure were examined. The potential of the method to shape the properties of the tested composites and the strong dependence of the obtained results on the morphology of the reinforcing phase was indicated. An interesting phenomenon observed for composites with the addition of MoS₂ during the process was the reaction of the components leading to in situ formation of the Al₁₂Mo intermetallic phase. Full article

(This article belongs to the Collection Spark-Plasma Sintering and Related Field-Assisted Powder Consolidation Technologies)

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11 pages, 2773 KiB

Open AccessArticle

Synthesis of Various TiO₂ Micro-/Nano-Structures and Their Photocatalytic Performance

by Anquan Deng^1,2

, Yufu Zhu^1,*, Xin Guo¹, Lei Zhou³ and Qingsong Jiang⁴

¹ Faculty of Mechanical & Material Engineering, Huaiyin Institute of Technology, Huaian 223003, China

² College of Material Science and Engineering, Nanjing Tech University, Nanjing 21009, China

³ Faculty of Mathematics and Physics, Huaiyin Institute of Technology, Huaian 223003, China

⁴ Jiangsu Engineering Laboratory for Lake Environment Remote Sensing Technologies, Faculty of Electronic Information Engineering, Huaiyin Institute of Technology, Huaian 223003, China

Materials 2018, 11(6), 995; https://doi.org/10.3390/ma11060995 - 12 Jun 2018

Cited by 17 | Viewed by 5574

Abstract

TiO₂ micro-/nano-structures with different morphologies have been successfully synthesized via a hydrothermal method. The effects of the solvents on the morphology and structure of the obtained products have been studied. The objective of the present paper is to compare the photocatalytic properties [...] Read more.

TiO₂ micro-/nano-structures with different morphologies have been successfully synthesized via a hydrothermal method. The effects of the solvents on the morphology and structure of the obtained products have been studied. The objective of the present paper is to compare the photocatalytic properties of the obtained TiO₂ products. During the synthesis process, the tetrabutyl titanate and titanium (IV) fluoride were used as the titanium source. The obtained micro-/nano-structures were characterized by field-emission scanning electron microscopy, X-ray diffraction analysis, and nitrogen adsorption-desorption isotherms. The photocatalytic activity of the samples was evaluated by the degradation of Rhodamine B solution under simulated solar irradiation. It is found that the morphologies and structures of TiO₂ have a great influence on its photocatalytic activity. Compared with other samples, TiO₂ flower clusters assembled with nanorods exhibited a superior photocatalytic activity in the degradation of Rhodamine B. Full article

(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)

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13 pages, 11288 KiB

Open AccessArticle

The Effect of Post-Processes on the Microstructure and Creep Properties of Alloy718 Built Up by Selective Laser Melting

by Yen-Ling Kuo^*, Toshiki Nagahari and Koji Kakehi

Department of Mechanical Systems Engineering, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji-shi, Tokyo 192-0397, Japan

Materials 2018, 11(6), 996; https://doi.org/10.3390/ma11060996 - 12 Jun 2018

Cited by 87 | Viewed by 6158

Abstract

The selective laser melting (SLM) process was used to fabricate an Alloy718 specimen. The microstructure and creep properties were characterized in both the as-built and post-processed SLM materials. Post-processing involved several heat treatments and a combination of hot isostatic pressing (HIP) and solution [...] Read more.

The selective laser melting (SLM) process was used to fabricate an Alloy718 specimen. The microstructure and creep properties were characterized in both the as-built and post-processed SLM materials. Post-processing involved several heat treatments and a combination of hot isostatic pressing (HIP) and solution treatment and aging (STA) to homogenize the microstructure. The experimental results showed that the originally recommended heat treatment process, STA-980 °C, for cast and wrought materials was not effective for SLM-processed specimens. Obvious grain growth structures were obtained in the STA-1180 °C/1 h and STA-1180 °C/4 h specimens. However, the grain size was uneven since heavy distortion or high-density dislocation formed during the SLM process, which would be harmful for the mechanical properties of SLM-fabricated materials. The HIP+ direct aging process was the most effective method among the post-processes to improve the creep behavior at 650 °C. The creep rupture life of the HIP+ direct aging condition approached 800 h since the HIP process had the benefit of being free of pores, thus preventing microcrack nucleation and the formation of a serrated grain boundary. Full article

(This article belongs to the Special Issue Selective Laser Sintering (SLS) of Materials)

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13 pages, 24612 KiB

Open AccessArticle

Preparation and Properties of C/C Hollow Spheres and the Energy Absorption Capacity of the Corresponding Aluminum Syntactic Foams

by Qiyong Yu, Yan Zhao^*, Anqi Dong and Ye Li

School of Materials Science and Engineering, Beihang University, Beijing 100191, China

Materials 2018, 11(6), 997; https://doi.org/10.3390/ma11060997 - 12 Jun 2018

Cited by 11 | Viewed by 4951

Abstract

The present study focuses on the preparation and characterization of lab-scale aluminum syntactic foams (ASFs) filled with hollow carbon spheres (HCSs). A new and original process for the fabrication of HCSs was explored. Firstly, expanded polystyrene beads with an average diameter of 6 [...] Read more.

The present study focuses on the preparation and characterization of lab-scale aluminum syntactic foams (ASFs) filled with hollow carbon spheres (HCSs). A new and original process for the fabrication of HCSs was explored. Firstly, expanded polystyrene beads with an average diameter of 6 mm and coated with carbon fibers/thermoset phenolic resin were produced by the “rolling ball” method. In the next step, the spheres were cured and post-cured, and then carbonized at 1050 °C under vacuum to form the HCSs. The porosity in the shell of the HCSs was decreased by increasing the number of impregnation–carbonization cycles. The aluminum syntactic foams were fabricated by casting the molten aluminum into a crucible filled with HCSs. The morphology of the hollow spheres before and after carbonization was investigated by scanning electron microscope (SEM). The compressive properties of the ASF were tested and the energy absorption capacities were calculated according to stress–strain curves. The results showed that the ASF filled with HCSs which had been treated by more cycles of impregnation–carbonization had higher energy absorption capacity. The aluminum syntactic foam absorbed 34.9 MJ/m³ (28.8 KJ/Kg) at 60% strain, which was much higher than traditional closed cell aluminum foams without particles. The HCSs have a promising future in producing a novel family of metal matrix syntactic foams. Full article

(This article belongs to the Section Porous Materials)

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10 pages, 3023 KiB

Open AccessArticle

Versatile Poly(Diallyl Dimethyl Ammonium Chloride)-Layered Nanocomposites for Removal of Cesium in Water Purification

by Sung-Chan Jang^1,2,†, Sung-Min Kang^2,†, Gi Yong Kim^1,3,†

, Muruganantham Rethinasabapathy², Yuvaraj Haldorai⁴, Ilsong Lee^1,2, Young-Kyu Han⁴, Joanna C. Renshaw^5,*, Changhyun Roh^1,6,*

and Yun Suk Huh^2,*

¹ Biotechnology Research Division, Advanced Radiation Technology Institute (ARTI), Korea Atomic Energy Research Institute (KAERI), 29, Geumgu-gil, Jeongeup-si, Jeonbuk 56212, Korea

² Department of Biological Engineering, Biohybrid Systems Research Center (BSRC), Inha University, 100, Inha-ro, Incheon 22212, Korea

³ Radwaste Management Center, Korea Atomic Energy Research Institute (KAERI), 989, Daedeok-daero, Daejeon 34057, Korea

⁴ Department of Energy and Materials Engineering, Dongguk University-Seoul, 30, Pildong-ro 1-gil, Seoul 04620, Korea

⁵ Department of Civil and Environmental Engineering, University of Strathclyde, James Weir Building, 75 Montrose St, Glasgow G1 1XJ, UK

⁶ Radiation Biotechnology and Applied Radioisotope Science, University of Science and Technology (UST), 217, Gajeong-ro, Daejeon 34113, Korea

^† These authors contributed equally to this work.

Materials 2018, 11(6), 998; https://doi.org/10.3390/ma11060998 - 12 Jun 2018

Cited by 10 | Viewed by 4456

Abstract

In this work, we elucidate polymer-layered hollow Prussian blue-coated magnetic nanocomposites as an adsorbent to remove radioactive cesium from environmentally contaminated water. To do this, Fe₃O₄ nanoparticles prepared using a coprecipitation method were thickly covered with a layer of cationic [...] Read more.

In this work, we elucidate polymer-layered hollow Prussian blue-coated magnetic nanocomposites as an adsorbent to remove radioactive cesium from environmentally contaminated water. To do this, Fe₃O₄ nanoparticles prepared using a coprecipitation method were thickly covered with a layer of cationic polymer to attach hollow Prussian blue through a self-assembly process. The as-synthesized adsorbent was confirmed through various analytical techniques. The adsorbent showed a high surface area (166.16 m²/g) with an excellent cesium adsorbent capacity and removal efficiency of 32.8 mg/g and 99.69%, respectively. Moreover, the superparamagnetism allows effective recovery of the adsorbent using an external magnetic field after the adsorption process. Therefore, the magnetic adsorbent with a high adsorption efficiency and convenient recovery is expected to be effectively used for rapid remediation of radioactive contamination. Full article

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11 pages, 3747 KiB

Open AccessArticle

Acoustic Anomalies and Phase Transition Behaviors of Lead-Free Piezoelectric (Na_1/2Bi_1/2)TiO₃-xBaTiO₃ Single Crystals as Revealed by Brillouin Light Scattering

by Byoung Wan Lee¹, Soo Han Oh¹, Jae-Hyeon Ko^1,*

, Xiaobing Li² and Haosu Luo²

¹ Department of Physics, Hallym University, Chuncheon, Gangwon-do 24252, Korea

² Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800, China

Materials 2018, 11(6), 1000; https://doi.org/10.3390/ma11061000 - 12 Jun 2018

Cited by 5 | Viewed by 3657

Abstract

The elastic properties of unpoled and prepoled (Na_1/2Bi_1/2)TiO₃-xBaTiO₃ (NBT-xBT) single crystals near the morphotropic phase boundary were investigated as a function of temperature using Brillouin light scattering. The acoustic mode frequency and [...] Read more.

The elastic properties of unpoled and prepoled (Na_1/2Bi_1/2)TiO₃-xBaTiO₃ (NBT-xBT) single crystals near the morphotropic phase boundary were investigated as a function of temperature using Brillouin light scattering. The acoustic mode frequency and the related acoustic damping of unpoled NBT-xBT showed very broad minimum and maximum, respectively, consistent with typical relaxor behaviors. The frequency softening of the longitudinal acoustic mode together with the increase in acoustic damping was largest along the <100> direction, indicating that polarization fluctuations were most substantial along this crystallographic direction. The difference in acoustic behaviors between the unpoled NBT-xBTs with x = 0.05 and 0.08 were negligible, which means that the NBT-xBT system exhibits typical relaxor properties over a certain composition range of at least 5~8%. The obtained relaxation time of polar nanoregions in the paraelectric phase showed a gradual slowing-down character without any critical divergent behavior. The prepoling of NBT-xBT along the <100> direction induced drastic changes in both mode frequency and damping at ~110 °C when the poling field was larger than 1.4 kV/mm, corresponding to the depoling process from macroscopic/mesoscopic ferroelectric order to ergodic relaxor state upon heating. Phase coexistence of ferroelectric and relaxor states was observed at the intermediate poling field of 1.4 kV/mm. Full article

(This article belongs to the Special Issue Piezoelectric Materials and Devices)

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18 pages, 10923 KiB

Open AccessArticle

Ultra-Precision Machining of a Compound Sinusoidal Grid Surface Based on Slow Tool Servo

by Shijun Ji, Jianfeng Li, Ji Zhao, Mei Feng^*, Changrui Sun and Handa Dai

School of Mechanical Science and Engineering, Jilin University, Changchun 130025, China

Materials 2018, 11(6), 1001; https://doi.org/10.3390/ma11061001 - 13 Jun 2018

Cited by 15 | Viewed by 4451

Abstract

Compound sinusoidal grid surface with nanometric finish plays a significant role in modern systems and precision calibrator, which can make the systems smaller, the system structure more simple, reduce the cost, and promote the performance of the systems, but it is difficult to [...] Read more.

Compound sinusoidal grid surface with nanometric finish plays a significant role in modern systems and precision calibrator, which can make the systems smaller, the system structure more simple, reduce the cost, and promote the performance of the systems, but it is difficult to design and fabricate by traditional methods. In this paper, a compound freeform surface constructed by a paraboloidal base surface and sinusoidal grid feature surface is designed and machined by slow tool servo (STS) assisted with single point diamond turning (SPDT). A novel combination of the constant angle and constant arc-length method is presented to optimize the cutting tool path. The machining error prediction model is analyzed for fabricating the compound sinusoidal grid surface. A compound sinusoidal grid surface with 0.03 mm amplitude and period of 4 is designed and cutting process is simulated by use of MATLAB software, machining experiment is done on ultra-precision machine tool, the surface profile and topography are measured by Taylor Hobson and Keyence VR-3200, respectively. After dealing with the measurement data of compound freeform surface, form accuracy 4.25 μm in Peak Village value (PV), and surface roughness 89 nm in Ra are obtained for the machined surface. From the theoretical analysis and experimental results, it can be seen that the proposed method is a reasonable choice for fabricating the compound sinusoidal grid surface. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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12 pages, 11240 KiB

Open AccessFeature PaperArticle

Functionalized Electrospun Poly(Vinyl Alcohol) Nanofibrous Membranes with Poly(Methyl Vinyl Ether-Alt-Maleic Anhydride) for Protein Adsorption

by Mesbah Najafi^*, Joronia Chery and Margaret M. Frey

Department of Fiber Science & Apparel Design, Cornell University, Ithaca, NY 14853, USA

Materials 2018, 11(6), 1002; https://doi.org/10.3390/ma11061002 - 13 Jun 2018

Cited by 19 | Viewed by 5234

Abstract

In this work, electrospun poly(vinyl alcohol) (PVA) nanofiber membranes were functionalized by incorporating poly(methyl vinyl ether-alt-maleic anhydride) (poly(MVE/MA), PMA) for the selective adsorption of proteins. The capture performance was regulated by an optimizing buffer pH, PMA content, and protein concentration. Lysozyme was used [...] Read more.

In this work, electrospun poly(vinyl alcohol) (PVA) nanofiber membranes were functionalized by incorporating poly(methyl vinyl ether-alt-maleic anhydride) (poly(MVE/MA), PMA) for the selective adsorption of proteins. The capture performance was regulated by an optimizing buffer pH, PMA content, and protein concentration. Lysozyme was used as the model protein and a high adsorption capacity of 476.53 ± 19.48 was obtained at pH 6, owing to the electrostatic attraction between the negatively charged nanofibers and positively charged proteins. The large specific surface area, highly open porous structure, and abundant available carboxyl groups contributed to such high adsorption performance. Moreover, the nanofiber membranes exhibited good reusability and good selectivity for positively charged proteins. The obtained results can provide a promising method for the purification of proteins in small analytic devices. Full article

(This article belongs to the Special Issue Electrospun Materials 2018)

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16 pages, 4479 KiB

Open AccessArticle

Self-Cleaning Ceramic Tiles Produced via Stable Coating of TiO₂ Nanoparticles

by Amid Shakeri¹, Darren Yip¹, Maryam Badv², Sara M. Imani², Mehdi Sanjari³ and Tohid F. Didar^1,2,4,*

¹ Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L7, Canada

² School of Biomedical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L8, Canada

³ Nanophyll Inc., 175 Longwood Rd South, Hamilton, ON L8P 0A1, Canada

⁴ Institute for Infectious Disease Research (IIDR), McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L8, Canada

Materials 2018, 11(6), 1003; https://doi.org/10.3390/ma11061003 - 13 Jun 2018

Cited by 44 | Viewed by 8577

Abstract

The high photocatalytic power of TiO₂ nanoparticles has drawn great attention in environmental and medical applications. Coating surfaces with these particles enables us to benefit from self-cleaning properties and decomposition of pollutants. In this paper, two strategies have been introduced to coat [...] Read more.

The high photocatalytic power of TiO₂ nanoparticles has drawn great attention in environmental and medical applications. Coating surfaces with these particles enables us to benefit from self-cleaning properties and decomposition of pollutants. In this paper, two strategies have been introduced to coat ceramic tiles with TiO₂ nanoparticles, and the self-cleaning effect of the surfaces on degradation of an organic dye under ultraviolent (UV) exposure is investigated. In the first approach, a simple one-step heat treatment method is introduced for coating, and different parameters of the heat treatment process are examined. In the second method, TiO₂ nanoparticles are first aminosilanized using (3-Aminopropyl)triethoxysilane (APTES) treatment followed by their covalently attachment onto CO₂ plasma treated ceramic tiles via N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and N-Hydroxysuccinimide (NHS) chemistry. We monitor TiO₂ nanoparticle sizes throughout the coating process using dynamic light scattering (DLS) and characterize developed surfaces using X-ray photoelectron spectroscopy (XPS). Moreover, hydrophilicity of the coated surfaces is quantified using a contact angle measurement. It is shown that applying a one-step heat treatment process with the optimum temperature of 200 °C for 5 h results in successful coating of nanoparticles and rapid degradation of dye in a short time. In the second strategy, the APTES treatment creates a stable covalent coating, while the photocatalytic capability of the particles is preserved. The results show that coated ceramic tiles are capable of fully degrading the added dyes under UV exposure in less than 24 h. Full article

(This article belongs to the Special Issue Materials: 10th Anniversary)

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12 pages, 1567 KiB

Open AccessFeature PaperArticle

Efficient Photocatalytic Degradation of Malachite Green in Seawater by the Hybrid of Zinc-Oxide Nanorods Grown on Three-Dimensional (3D) Reduced Graphene Oxide(RGO)/Ni Foam

by Qing Wang¹, Chaoyue Cai¹, Mingyan Wang^1,*

, Qian Guo¹, Biao Wang¹, Weina Luo¹, Yujuan Wang¹, Chenyan Zhang¹, Lihua Zhou¹, Dongen Zhang¹, Zhiwei Tong¹, Yuqing Liu² and Jun Chen^2,*

¹ Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005, China

² Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, Australian Institute of Innovative Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia

Materials 2018, 11(6), 1004; https://doi.org/10.3390/ma11061004 - 13 Jun 2018

Cited by 41 | Viewed by 6868

Abstract

A hybrid of ZnO nanorods grown onto three-dimensional (3D) reduced graphene oxide (RGO)@Ni foam (ZnO/RGO@NF) is synthesized by a facile hydrothermal method. The as-prepared hybrid material is physically characterized by SEM, XRD, Raman, and X-ray photoelectron spectroscopy (XPS). When the as-prepared 3D hybrid [...] Read more.

A hybrid of ZnO nanorods grown onto three-dimensional (3D) reduced graphene oxide (RGO)@Ni foam (ZnO/RGO@NF) is synthesized by a facile hydrothermal method. The as-prepared hybrid material is physically characterized by SEM, XRD, Raman, and X-ray photoelectron spectroscopy (XPS). When the as-prepared 3D hybrid is investigated as a photocatalyst, it demonstrates significant high photocatalytic activity for the degradation of methylene blue (MB), rhodamine (RhB), and mixed MB/RhB as organic dye pollutants. In addition, the practical application and the durability of the as-prepared catalyst to degradation of malachite green (MG) in seawater are firstly assessed in a continuous flow system. The catalyst shows a high degradation efficiency and stable photocatalytic activity for 5 h continuous operation, which should be a promising catalyst for the degradation of organic dyes in seawater. Full article

(This article belongs to the Special Issue Nano-based Catalysts for Renewable Energy)

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13 pages, 2477 KiB

Open AccessArticle

Synergistic Effect of Graphene Oxide and Mesoporous Structure on Flame Retardancy of Nature Rubber/IFR Composites

by Na Wang^1,2,*, Miao Zhang^1,2, Ping Kang², Jing Zhang², Qinghong Fang² and Wenda Li³

¹ Sino-Spanish Advanced Materials Institute, Shenyang University of Chemical Technology, Shenyang 110142, China

² Liaoning Provincial Key Laboratory of Rubber & Elastomer, Shenyang 110142, China

³ IMDEA Materials Institute, C/Eric Kandel 2, Getafe, 28906 Madrid, Spain

Materials 2018, 11(6), 1005; https://doi.org/10.3390/ma11061005 - 13 Jun 2018

Cited by 30 | Viewed by 4274

Abstract

Aiming to improve the flame retardancy performance of natural rubber (NR), we developed a novel flame retardant synergistic agent through grafting of MCM-41 to graphene oxide (GO), named as GO-NH-MCM-41, as an assistant to intumescent flame retardants (IFR). The flame retardancy of NR/IFR/GO-NH-MCM-41 [...] Read more.

Aiming to improve the flame retardancy performance of natural rubber (NR), we developed a novel flame retardant synergistic agent through grafting of MCM-41 to graphene oxide (GO), named as GO-NH-MCM-41, as an assistant to intumescent flame retardants (IFR). The flame retardancy of NR/IFR/GO-NH-MCM-41 composites was evaluated by limited oxygen index (LOI), UL-94, and cone calorimeter test. The LOI value of NR/IFR/GO-NH-MCM-41 reached 26.3%; the UL-94 ratings improved to a V-0 rating. Moreover, the addition of GO-NH-MCM-41 decreased the peak heat release rate (PHRR) and the total heat release (THR) of the natural rubber composites. Furthermore, the addition of GO-NH-MCM-41 increased the thickness of char residue. The images of SEM indicated the char residue was more compact and continuous. The degradation of GO-NH-MCM-41-based NR composites was completed with a mass loss of 35.57% at 600 °C. The tensile strength and the elongation at break of the NR/IFR/GO-NH-MCM-41 composites were 13.9 MPa and 496.7%, respectively. The results of the rubber process analyzer (RPA) reached the maximum value, probably due to a better network of fillers in the matrix. Full article

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16 pages, 2348 KiB

Open AccessArticle

3D Printed, PVA–PAA Hydrogel Loaded-Polycaprolactone Scaffold for the Delivery of Hydrophilic In-Situ Formed Sodium Indomethacin

by Mershen Govender

, Sunaina Indermun, Pradeep Kumar

, Yahya E. Choonara

and Viness Pillay^*

Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg 2193, South Africa

Materials 2018, 11(6), 1006; https://doi.org/10.3390/ma11061006 - 13 Jun 2018

Cited by 19 | Viewed by 6133

Abstract

3D printed polycaprolactone (PCL)-blended scaffolds have been designed, prepared, and evaluated in vitro in this study prior to the incorporation of a polyvinyl alcohol–polyacrylic acid (PVA–PAA) hydrogel for the delivery of in situ-formed sodium indomethacin. The prepared PCL–PVA–PAA scaffold is proposed as a [...] Read more.

3D printed polycaprolactone (PCL)-blended scaffolds have been designed, prepared, and evaluated in vitro in this study prior to the incorporation of a polyvinyl alcohol–polyacrylic acid (PVA–PAA) hydrogel for the delivery of in situ-formed sodium indomethacin. The prepared PCL–PVA–PAA scaffold is proposed as a potential structural support system for load-bearing tissue damage where inflammation is prevalent. Uniaxial strain testing of the PCL-blended scaffolds were undertaken to determine the scaffold’s resistance to strain in addition to its thermal, structural, and porosimetric properties. The viscoelastic properties of the incorporated PVA–PAA hydrogel has also been determined, as well as the drug release profile of the PCL–PVA–PAA scaffold. Results of these analyses noted the structural strength, thermal stability, and porosimetric properties of the scaffold, as well as the ability of the PCL–PVA–PAA scaffold to deliver sodium indomethacin in simulated physiological conditions of pH and temperature. The results of this study therefore highlight the successful design, fabrication, and in vitro evaluation of a 3D printed polymeric strain-resistant supportive platform for the delivery of sodium indomethacin. Full article

(This article belongs to the Special Issue Materials for Photolithography and 3D Printing)

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12 pages, 25911 KiB

Open AccessFeature PaperArticle

Three Dimensional Methodology to Characterize Large Dendritic Equiaxed Grains in Industrial Steel Ingots

by Marvin Gennesson^1,2,3,*, Julien Zollinger^1,2

, Dominique Daloz^1,2

, Bernard Rouat^1,2, Joëlle Demurger³ and Hervé Combeau^1,2

¹ Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine, 57073 Metz, France

² Department of Metallurgy & Materials Science and Engineering, Institut Jean Lamour, 2 allée André Guinier Campus Artem, 54000 Nancy, France

³ Ascométal CREAS, Avenue de France, BP 70045, 57301 Hagondange, France

Materials 2018, 11(6), 1007; https://doi.org/10.3390/ma11061007 - 13 Jun 2018

Cited by 10 | Viewed by 4922

Abstract

The primary phase grain size is a key parameter to understand the formation of the macrosegregation pattern in large steel ingots. Most of the characterization techniques use two-dimensional measurements. In this paper, a characterization method has been developed for equiaxed dendritic grains in [...] Read more.

The primary phase grain size is a key parameter to understand the formation of the macrosegregation pattern in large steel ingots. Most of the characterization techniques use two-dimensional measurements. In this paper, a characterization method has been developed for equiaxed dendritic grains in industrial steel castings. A total of 383 contours were drawn two-dimensionally on twelve

6.6

cm²slices. A three-dimensional reconstruction method is performed to obtain 171 three-dimensional grains. Data regarding the size, shape and orientation of equiaxed grains is presented and thereby shows that equiaxed grains are centimeter-scale complex objects. They appear to be a poly-dispersed collection of non-isotropic objects possessing preferential orientations. In addition, the volumetric grain number density is

2.2 \times 10^{7}

grains/

m^{3}

, which compares to the

0.5 \times 10^{7}

grains/

m^{3}

that can be obtained with estimation from 2D measurements. The

2.2 \times 10^{7}

grains/

m^{3}

value is ten-times smaller than that previously used in the literature to simulate the macrosegregation profile in the same

6.2

ton ingot. Full article

(This article belongs to the Special Issue Design of Alloy Metals for Low-Mass Structures)

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22 pages, 4302 KiB

Open AccessArticle

Health Degradation Monitoring and Early Fault Diagnosis of a Rolling Bearing Based on CEEMDAN and Improved MMSE

by Yong Lv^1,2, Rui Yuan^1,2,*

, Tao Wang^1,2, Hewenxuan Li³ and Gangbing Song⁴

¹ Key Laboratory of Metallurgical Equipment and Control Technology, Wuhan University of Science and Technology, Ministry of Education, Wuhan 430081, China

² Hubei Key Laboratory of Mechanical Transmission and Manufacturing Engineering, Wuhan University of Science and Technology, Wuhan 430081, China

³ Department of Mechanical, Industrial and Systems Engineering, University of Rhode Island, Kingston, RI 02881, USA

⁴ Smart Material and Structure Laboratory, Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA

Materials 2018, 11(6), 1009; https://doi.org/10.3390/ma11061009 - 14 Jun 2018

Cited by 87 | Viewed by 5707

Abstract

Rolling bearings play a crucial role in rotary machinery systems, and their operating state affects the entire mechanical system. In most cases, the fault of a rolling bearing can only be identified when it has developed to a certain degree. At that moment, [...] Read more.

Rolling bearings play a crucial role in rotary machinery systems, and their operating state affects the entire mechanical system. In most cases, the fault of a rolling bearing can only be identified when it has developed to a certain degree. At that moment, there is already not much time for maintenance, and could cause serious damage to the entire mechanical system. This paper proposes a novel approach to health degradation monitoring and early fault diagnosis of rolling bearings based on a complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and improved multivariate multiscale sample entropy (MMSE). The smoothed coarse graining process was proposed to improve the conventional MMSE. Numerical simulation results indicate that CEEMDAN can alleviate the mode mixing problem and enable accurate intrinsic mode functions (IMFs), and improved MMSE can reflect intrinsic dynamic characteristics of the rolling bearing more accurately. During application studies, rolling bearing signals are decomposed by CEEMDAN to obtain IMFs. Then improved MMSE values of effective IMFs are computed to accomplish health degradation monitoring of rolling bearings, aiming at identifying the early weak fault phase. Afterwards, CEEMDAN is performed to extract the fault characteristic frequency during the early weak fault phase. The experimental results indicate the proposed method can obtain a better performance than other techniques in objective analysis, which demonstrates the effectiveness of the proposed method in practical application. The theoretical derivations, numerical simulations, and application studies all confirmed that the proposed health degradation monitoring and early fault diagnosis approach is promising in the field of prognostic and fault diagnosis of rolling bearings. Full article

(This article belongs to the Special Issue Deformation, Fatigue and Fracture of Materials)

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13 pages, 2855 KiB

Open AccessArticle

Effect of Temperature Distribution in Ultrasonically Welded Joints of Copper Wire and Sheet Used for Electrical Contacts

by Jeyaraj Pradeep Kumar

Department of Production Engineering, PSG College of Technology, Coimbatore 641 004, Tamil Nadu, India

Materials 2018, 11(6), 1010; https://doi.org/10.3390/ma11061010 - 14 Jun 2018

Cited by 20 | Viewed by 4806

Abstract

The temperature distribution occurring at the interface while joining a simple electrical contact comprising of a copper wire and a copper sheet using ultrasonic metal welding was analyzed using finite element method. Heat flux due to plastic deformation and friction was calculated and [...] Read more.

The temperature distribution occurring at the interface while joining a simple electrical contact comprising of a copper wire and a copper sheet using ultrasonic metal welding was analyzed using finite element method. Heat flux due to plastic deformation and friction was calculated and provided as input load for simulation of temperature distribution. The results of temperature obtained from simulation are found to be in good agreement with the results of temperature from experiments measured using thermocouple. Special focus was given to how the heat generated at the wire–sheet interface affect the strength of the joint in tension. With the knowledge of heat generated at the interface while welding, it is possible to control the strength of the joint and produce defect free joints. Based on the results from finite element analysis and experiments, it is observed that the influence of heat developed due to friction and plastic deformation of metallic specimens has a significant effect on the progress of welding and strength of the joint. Full article

(This article belongs to the Special Issue Special Issue of the Manufacturing Engineering Society (MES))

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11 pages, 1532 KiB

Open AccessArticle

Structural Coloration of Polyester Fabrics Coated with Al/TiO₂ Composite Films and Their Anti-Ultraviolet Properties

by Xiaohong Yuan^1,*

, Yuanjing Ye², Min Lian¹ and Qufu Wei³

¹ Fujian Key Laboratory of Novel Functional Textile Fibers and Materials, Faculty of Clothing and Design, Minjiang University, Fuzhou 350108, China

² Fujian Fibers Inspection Bureau, Fuzhou 350026, China

³ Key Laboratory of Eco-Textiles, Ministry of Education, Jiangnan University, Wuxi 214122, China

Materials 2018, 11(6), 1011; https://doi.org/10.3390/ma11061011 - 14 Jun 2018

Cited by 16 | Viewed by 5039

Abstract

Al/TiO₂ composite film was successfully deposited on polyester fabrics by using magnetron sputtering techniques. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to examine the deposited films on the fabrics, and the structural colors and anti-ultraviolet property of fabrics were [...] Read more.

Al/TiO₂ composite film was successfully deposited on polyester fabrics by using magnetron sputtering techniques. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to examine the deposited films on the fabrics, and the structural colors and anti-ultraviolet property of fabrics were also analyzed. The results indicated that polyester fabrics coated with Al/TiO₂ composite films achieved structural colors. The reactive sputtering times of TiO₂ films in Al/TiO₂ composite films were 10 min, 12 min, 18 min, 20 min, 26 min, 27 min, 30 min and 45 min, respectively, the colors of corresponding fabrics were bluish violet, blue, cyan, green, yellow, yellowish red, orange and blue-green, which was consistent with the principle of the thin film interference. The structure of the TiO₂ film in Al/TiO₂ composite films was non-crystalline, though the fabrics were heated and maintained at the temperature of 200 °C. The anti-ultraviolet property of the fabrics deposited with Al/TiO₂ composite films were excellent because of the effect of Al/TiO₂ composite films. Full article

(This article belongs to the Special Issue Thin Film Fabrication and Surface Techniques)

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12 pages, 2635 KiB

Open AccessFeature PaperArticle

An Electrochemical Study on the Copolymer Formed from Piperazine and Aniline Monomers

by Samiha Dkhili^1,2, Sara López-Bernabeu², Chahineze Nawel Kedir², Francisco Huerta³

, Francisco Montilla², Salma Besbes-Hentati¹ and Emilia Morallon^2,*

¹ Laboratoire de Chimie des Matériaux, Faculté des Sciences de Bizerte, Zarzouna Université de Carthage, Jarzouna, Bizerte 7021, Tunisia

² Departamento de Química Física e Instituto Universitario de Materiales, Universidad de Alicante, Ap. 99, E-03080 Alicante, Spain

³ Departamento de Ingenieria Textil y Papelera, Universitat Politecnica de Valencia, Plaza Ferrandiz y Carbonell, 1, E-03801 Alcoy, Spain

Materials 2018, 11(6), 1012; https://doi.org/10.3390/ma11061012 - 14 Jun 2018

Cited by 10 | Viewed by 4347

Abstract

A study on the electrochemical oxidation of piperazine and its electrochemical copolymerization with aniline in acidic medium is presented. It was found that the homopolymerization of piperazine cannot be achieved under electrochemical conditions. A combination of electrochemistry, in situ Fourier transform infrared (FTIR), [...] Read more.

A study on the electrochemical oxidation of piperazine and its electrochemical copolymerization with aniline in acidic medium is presented. It was found that the homopolymerization of piperazine cannot be achieved under electrochemical conditions. A combination of electrochemistry, in situ Fourier transform infrared (FTIR), and ex situ X-ray photoelectron spectroscopy (XPS) spectroscopies was used to characterize both the chemical structure and the redox behavior of an electrochemically synthesized piperazine–aniline copolymer. The electrochemical sensing properties of the deposited material were also tested against ascorbic acid and dopamine as redox probes. Full article

(This article belongs to the Special Issue Conductive Polymers: Materials and Applications)

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12 pages, 2973 KiB

Open AccessFeature PaperArticle

Modified Polymeric Nanoparticles Exert In Vitro Antimicrobial Activity Against Oral Bacteria

by Manuel Toledano-Osorio¹, Jegdish P. Babu², Raquel Osorio^1,*, Antonio L. Medina-Castillo³, Franklin García-Godoy² and Manuel Toledano¹

¹ Dental School, University of Granada, Campus de Cartuja s/n, 18071 Granada, Spain

² College of Dentistry, University of Tennessee Health Science Center, 875 Union Avenue, Memphis, TN 381632110, USA

³ NanoMyP, Spin-Off Enterprise from University of Granada, Edificio BIC-Granada, Av. Innovación 1, Armilla, 18016 Granada, Spain

Materials 2018, 11(6), 1013; https://doi.org/10.3390/ma11061013 - 14 Jun 2018

Cited by 30 | Viewed by 4547

Abstract

Polymeric nanoparticles were modified to exert antimicrobial activity against oral bacteria. Nanoparticles were loaded with calcium, zinc and doxycycline. Ions and doxycycline release were measured by inductively coupled plasma optical emission spectrometer and high performance liquid chromatography. Porphyromonas gingivalis, Lactobacillus lactis, [...] Read more.

Polymeric nanoparticles were modified to exert antimicrobial activity against oral bacteria. Nanoparticles were loaded with calcium, zinc and doxycycline. Ions and doxycycline release were measured by inductively coupled plasma optical emission spectrometer and high performance liquid chromatography. Porphyromonas gingivalis, Lactobacillus lactis, Streptoccocus mutans, gordonii and sobrinus were grown and the number of bacteria was determined by optical density. Nanoparticles were suspended in phosphate-buffered saline (PBS) at 10, 1 and 0.1 mg/mL and incubated with 1.0 mL of each bacterial suspension for 3, 12, and 24 h. The bacterial viability was assessed by determining their ability to cleave the tetrazolium salt to a formazan dye. Data were analyzed by ANOVA and Scheffe’s F (p < 0.05). Doxycycline doping efficacy was 70%. A burst liberation effect was produced during the first 7 days. After 21 days, a sustained release above 6 µg/mL, was observed. Calcium and zinc liberation were about 1 and 0.02 µg/mL respectively. The most effective antibacterial material was found to be the Dox-Nanoparticles (60% to 99% reduction) followed by Ca-Nanoparticles or Zn-Nanoparticles (30% to 70% reduction) and finally the non-doped nanoparticles (7% to 35% reduction). P. gingivalis, S. mutans and L. lactis were the most susceptible bacteria, being S. gordonii and S. sobrinus the most resistant to the tested nanoparticles. Full article

(This article belongs to the Special Issue Bioactive and Therapeutic Dental Materials)

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14 pages, 8250 KiB

Open AccessArticle

Stabilization of Loess Using Nano-SiO₂

by Ran Kong¹, Fanyu Zhang^1,*

, Gonghui Wang² and Jianbing Peng^3,*

¹ MOE Key Laboratory of Mechanics on Disaster and Environment in Western China, Department of Geological Engineering, Lanzhou University, Lanzhou 730000, China

² Research Center on Landslides, Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan

³ Department of Geological Engineering, Chang’an University, Xi’an 710054, China

Materials 2018, 11(6), 1014; https://doi.org/10.3390/ma11061014 - 14 Jun 2018

Cited by 69 | Viewed by 4893

Abstract

Improving the performance of loess is of significant importance for lowering its collapsibility and water sensitivity to construction requirements and for geohazard mitigation. The present paper studies the changes in mechanical, structural, and mineralogical properties of nano-SiO₂-treated loess with different contents [...] Read more.

Improving the performance of loess is of significant importance for lowering its collapsibility and water sensitivity to construction requirements and for geohazard mitigation. The present paper studies the changes in mechanical, structural, and mineralogical properties of nano-SiO₂-treated loess with different contents and curing days. The mechanical behavior was examined by unconfined compressive strength (UCS) of untreated and treated loess. To better understand the mechanisms of stabilization, particle size distributions, scanning electron microscope (SEM) images, and X-ray diffraction (XRD) analyses were carried out. The results show that the UCS increase with increasing contents and curing days due to nano-SiO₂ addition produced coarser particles, denser packing, and smaller pores in treated loess. The changes in the properties can be attributed to the formation of aggregation and agglomeration, with greater particle sizes and more interparticle contact. In addition, the results from mineralogical component analysis further confirm that physical structure modification controls the changes in mechanical and fabric properties, rather than chemical component alteration. Even small nano-SiO₂ additions can also provide great improvement when curing days are enough for the treated loess. These findings reveal that nano-SiO₂ has the potential to serve as a cost-effective stabilized additive that treats the universal loess. Full article

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16 pages, 7417 KiB

Open AccessArticle

Effects of Cutting Edge Microgeometry on Residual Stress in Orthogonal Cutting of Inconel 718 by FEM

by Qi Shen^1,2, Zhanqiang Liu^1,2,*

, Yang Hua^1,2, Jinfu Zhao^1,2, Woyun Lv^1,2 and Aziz Ul Hassan Mohsan^1,2

¹ School of Mechanical Engineering, Shandong University, Jinan 250061, China

² Key Laboratory of High Efficiency and Clean Mechanical Manufacture of MOE/Key National Demonstration Center for Experimental Mechanical Engineering Education, Jinan 250061, China

Materials 2018, 11(6), 1015; https://doi.org/10.3390/ma11061015 - 14 Jun 2018

Cited by 41 | Viewed by 6045

Abstract

Service performance of components such as fatigue life are dramatically influenced by the machined surface and subsurface residual stresses. This paper aims at achieving a better understanding of the influence of cutting edge microgeometry on machined surface residual stresses during orthogonal dry cutting [...] Read more.

Service performance of components such as fatigue life are dramatically influenced by the machined surface and subsurface residual stresses. This paper aims at achieving a better understanding of the influence of cutting edge microgeometry on machined surface residual stresses during orthogonal dry cutting of Inconel 718. Numerical and experimental investigations have been conducted in this research. The cutting edge microgeometry factors of average cutting edge radius

\bar{S}

, form-factor K, and chamfer were investigated. An increasing trend for the magnitudes of both tensile and compressive residual stresses was observed by using larger

\bar{S}

or introducing a chamfer on the cutting edges. The ploughing depth has been predicted based on the stagnation zone. The increase of ploughing depth means that more material was ironed on the workpiece subsurface, which resulted in an increase in the compressive residual stress. The thermal loads were leading factors that affected the surface tensile residual stress. For the unsymmetrical honed cutting edge with K = 2, the friction between tool and workpiece and tensile residual stress tended to be high, while for the unsymmetrical honed cutting edge with K = 0.5, the high ploughing depth led to a higher compressive residual stress. This paper provides guidance for regulating machine-induced residual stress by edge preparation. Full article

(This article belongs to the Special Issue Machining—Recent Advances, Applications and Challenges)

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12 pages, 4687 KiB

Open AccessArticle

Preparation and Performance Analysis of Modified Sodium Acetate Trihydrate

by Weisan Hua, Xuelai Zhang^*, Munyalo Jotham Muthoka and Xingchao Han

Institute of Thermal Storage Technology, Merchant Marine College, Shanghai Maritime University, Shanghai 201306, China

Materials 2018, 11(6), 1016; https://doi.org/10.3390/ma11061016 - 15 Jun 2018

Cited by 23 | Viewed by 5465

Abstract

In order to solve undercooling and phase separation of sodium acetate trihydrate (SAT), experimental screening method was used to select nucleating agents and thickeners that are suitable for SAT, and the optimal ratio was identified. Through screening experiments of nucleating agents, it is [...] Read more.

In order to solve undercooling and phase separation of sodium acetate trihydrate (SAT), experimental screening method was used to select nucleating agents and thickeners that are suitable for SAT, and the optimal ratio was identified. Through screening experiments of nucleating agents, it is found that disodium hydrogen phosphate can be used as an effective nucleating agent for SAT. When the weight content of disodium hydrogen phosphate in SAT is 2%, the degree of undercooling was reduced to approximately 2 K. The addition of 1–1.5% (weight) of xanthan gum (XG) to SAT can effectively inhibit the phase separation. Since the properties of SAT changes after the modification, the corresponding comparison analysis was performed. The results showed that XG has a significant influence on the SAT performance of SAT. With the addition of 1.5 wt % of XG in pure SAT, the latent heat of fusion and solid/liquid volume expansion reduce by 5.2% and 5.4% respectively, and the thermal conductivity and solid/liquid density also decreases accordingly. Full article

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9 pages, 2716 KiB

Open AccessArticle

Properties and Structure of In Situ Transformed PAN-Based Carbon Fibers

by Jingjing Cao^*, Wenwu Zhao and Shuzhen Gao

College of Mechanical and Equipment Engineering, Hebei University of Engineering, Handan 056038, China

Materials 2018, 11(6), 1017; https://doi.org/10.3390/ma11061017 - 15 Jun 2018

Cited by 19 | Viewed by 4916

Abstract

Carbon fibers in situ prepared during the hot-pressed sintering in a vacuum is termed in situ transformed polyacrylonitrile-based (PAN-based) carbon fibers, and the fibrous precursors are the pre-oxidized PAN fibers. The properties and structure of in situ transformed PAN-based carbon fibers are investigated [...] Read more.

Carbon fibers in situ prepared during the hot-pressed sintering in a vacuum is termed in situ transformed polyacrylonitrile-based (PAN-based) carbon fibers, and the fibrous precursors are the pre-oxidized PAN fibers. The properties and structure of in situ transformed PAN-based carbon fibers are investigated by Nano indenter, SEM, TEM, XRD, and Raman. The results showed that the microstructure of the fiber surface layer was compact, while the core was loose, with evenly-appearing microvoids. The elastic modulus and nanohardness of the fiber surface layer (303.87 GPa and 14.82 GPa) were much higher than that of the core (16.57 GPa and 1.54 GPa), and its interlayer spacing d002 and crystallinity were about 0.347 nm and 0.97 respectively. It was found that the preferred orientation of the surface carbon layers with ordered carbon atomic arrangement tended to be parallel to the fiber axis, whereas the fiber core in the amorphous region exhibited a random texture and the carbon atomic arrangement was in a disordered state. It indicates that the in situ transformed PAN-based carbon fibers possess significantly turbostratic structure and anisotropy. Full article

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10 pages, 4655 KiB

Open AccessArticle

Hierarchically Nanostructured CuO–Cu Current Collector Fabricated by Hybrid Methods for Developed Li-Ion Batteries

by Jin-Young So, Chan-Ho Lee

, Ji-Eun Kim, Hyun-Jee Kim, Joonha Jun and Won-Gyu Bae^*

Department of Electrical Engineering, Soongsil University, Seoul 156-743, Korea

Materials 2018, 11(6), 1018; https://doi.org/10.3390/ma11061018 - 15 Jun 2018

Cited by 12 | Viewed by 4254

Abstract

We present a simple method of fabricating a hierarchically nanostructured CuO–Cu current collector by using laser ablation and metal mold imprinting to maximize the surface area. The laser ablation of the Cu current collector created the CuO nanostructure on the Cu-collector surface. The [...] Read more.

We present a simple method of fabricating a hierarchically nanostructured CuO–Cu current collector by using laser ablation and metal mold imprinting to maximize the surface area. The laser ablation of the Cu current collector created the CuO nanostructure on the Cu-collector surface. The microstructure was transferred by subsequent imprinting of the microstructure metal mold on the Cu collector. Then, the laser-ablation nanostructure was formed. Consequently, a hierarchical structure is generated. The laser-ablated hierarchical CuO–Cu current collector exhibited an improved capacity while maintaining a cyclability that is similar to those of conventional graphite batteries. Full article

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16 pages, 4756 KiB

Open AccessArticle

Peculiarities in the Material Design of Buckling Resistance for Tensioned Laminated Composite Panels with Elliptical Cut-Outs

by Aleksander Muc

Institute of Machine Design, Cracow University of Technology, ul. Warszawska 24, 31-155 Kraków, Poland

Materials 2018, 11(6), 1019; https://doi.org/10.3390/ma11061019 - 15 Jun 2018

Cited by 18 | Viewed by 3677

Abstract

The results of analytical and numerical studies of the buckling behavior of laminated multilayered tensioned sheets with circular and elliptical openings are presented. The analysis shows the significant influence of stress concentration effects on buckling modes and loads, particularly taking into consideration variations [...] Read more.

The results of analytical and numerical studies of the buckling behavior of laminated multilayered tensioned sheets with circular and elliptical openings are presented. The analysis shows the significant influence of stress concentration effects on buckling modes and loads, particularly taking into consideration variations in the E₁/E₂ and E₁/G₁₂ ratios. The results of finite element (FE) computations prove that the buckling mode cannot be described by a single buckle localized at the apex of the hole. The optimal design of such structures seems to be much more complicated than classical buckling problems of compressed laminated panels without holes. However, the obtained results indicate that the optimal laminate configurations occur at the boundaries of the feasible regions of the introduced design space. Both continuous and discrete fibre orientations are considered. For continuous fibre orientations, the optimal stacking sequence corresponds to angle-ply symmetric laminates. Full article

(This article belongs to the Section Advanced Composites)

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11 pages, 6657 KiB

Open AccessArticle

Using Spin-Coated Silver Nanoparticles/Zinc Oxide Thin Films to Improve the Efficiency of GaInP/(In)GaAs/Ge Solar Cells

by Po-Hsun Lei^*, I-Jen Chen, Jia-Jan Chen, Po-Chun Yang and Yan-Hua Gong

Institute of Electro-Optical and Materials Science, National Formosa University, 64 Wen-Hwa Rd, Hu-Wei, Yun-Lin 623, Taiwan

Materials 2018, 11(6), 1020; https://doi.org/10.3390/ma11061020 - 15 Jun 2018

Cited by 3 | Viewed by 5178

Abstract

We synthesized a silver nanoparticle/zinc oxide (Ag NP/ZnO) thin film by using spin-coating technology. The treatment solution for Ag NP/ZnO thin film deposition contained zinc acetate (Zn(CH₃COO)₂), sodium hydroxide (NaOH), and silver nitrate (AgNO₃) aqueous solutions. The [...] Read more.

We synthesized a silver nanoparticle/zinc oxide (Ag NP/ZnO) thin film by using spin-coating technology. The treatment solution for Ag NP/ZnO thin film deposition contained zinc acetate (Zn(CH₃COO)₂), sodium hydroxide (NaOH), and silver nitrate (AgNO₃) aqueous solutions. The crystalline characteristics, surface morphology, content of elements, and reflectivity of the Ag NPs/ZnO thin film at various concentrations of the AgNO₃ aqueous solution were investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and ultraviolet–visible–near infrared spectrophotometry. The results indicated that the crystalline structure, Ag content, and reflectance of Ag NP/ZnO thin films depended on the AgNO₃ concentration. Hybrid antireflection coatings (ARCs) composed of SiN_x and Ag NPs/ZnO thin films with various AgNO₃ concentrations were deposited on GaInP/(In)GaAs/Ge solar cells. We propose that the optimal ARC consists of SiN_x and Ag NP/ZnO thin films prepared using a treatment solution of 0.0008 M AgNO₃, 0.007 M Zn(CH₃COO)₂, and 1 M NaOH, followed by post-annealing at 200 °C. GaInP/(Al)GaAs/Ge solar cells with the optimal hybrid ARC and SiN_x ARC exhibit a conversion efficiency of 34.1% and 30.2% with V_oc = 2.39 and 2.4 V, J_sc = 16.63 and 15.37 mA/cm², and fill factor = 86.1% and 78.8%. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2018)

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8 pages, 2506 KiB

Open AccessFeature PaperCommunication

Redox Activity of Sodium Vanadium Oxides towards Oxidation in Na Ion Batteries

by Evan Adamczyk

, Muthaiyan Gnanavel and Valerie Pralong^*

Normandie Univ, ENSICAEN, UNICAEN, CNRS, CRISMAT, 14000 Caen, France

Materials 2018, 11(6), 1021; https://doi.org/10.3390/ma11061021 - 15 Jun 2018

Cited by 10 | Viewed by 4314

Abstract

The search for new materials that could be used as electrode material for Na-ion batteries is one of the most challenging issues of today. Many transition metal oxide families as well as transition metal polyanionic frameworks have been proposed over the last five [...] Read more.

The search for new materials that could be used as electrode material for Na-ion batteries is one of the most challenging issues of today. Many transition metal oxide families as well as transition metal polyanionic frameworks have been proposed over the last five years. In this work, we report the sodium extraction from Na₂V₃O₇, which is a tunnel type structure built of [V₃O₇]²⁻_∞ nanotubes held by sodium ions. We report a reversible charge capacity of 80 mAh/g at 2.8 V vs. Na⁺/Na due to the V⁵⁺/V⁴⁺ redox activity. No oxygen redox activity has been observed for this material nor for the vanadium (5+) oxide Na₄V₂O₇. Full article

(This article belongs to the Special Issue Electrode Materials for High Performance Sodium-ion Batteries)

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13 pages, 3684 KiB

Open AccessArticle

Synthesis of TiO_2NWS@Au_NPS Composite Catalyst for Methylene Blue Removal

by Fan Fu¹, Feifei Wang¹, Ting Li¹, Chenlu Jiao¹, Yan Zhang^1,2,* and Yuyue Chen^1,*

¹ National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, China

² Nantong Textile & Silk Industrial Technology Research Institute, Nantong 226314, China

Materials 2018, 11(6), 1022; https://doi.org/10.3390/ma11061022 - 15 Jun 2018

Cited by 13 | Viewed by 3956

Abstract

In this article, HBP-NH₂-modified titania nanowire (TiO_2NWS)-decorated Au nanoparticles (TiO_2NWS@Au_NPS) were synthesized by one-step method. The role of HBP-NH₂ concentration in the formation of TiO_2NWS was investigated. The fineness and uniformity of pure [...] Read more.

In this article, HBP-NH₂-modified titania nanowire (TiO_2NWS)-decorated Au nanoparticles (TiO_2NWS@Au_NPS) were synthesized by one-step method. The role of HBP-NH₂ concentration in the formation of TiO_2NWS was investigated. The fineness and uniformity of pure TiO_2NWS were enhanced by absorbed amino groups from amino-terminated hyperbranched polymer (HBP-NH₂). The morphology and crystal structure of TiO_2NWS and TiO_2NWS@Au_NPS were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fournier transform infrared (FTIR) spectroscopy. The chemical states of gold, titanium and oxygen were analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that at the concentration of HBP-NH₂ 100 g/L, the mean diameter of TiO_2NWS was nearly 72 nm and Au nanoparticles were uniformly distributed on the surface of TiO_2NWS. The presence of Au_NPS improved the photocatalytic properties of TiO_2NWS under UV light irradiation. The Au load was believed to improve the utilization rate of the photoelectron and activated the adsorbed oxygen. The obtained TiO_2NWS@Au_NPS decomposed 99.6% methylene blue (MB) after 300 min when subjected to UV light irradiation. After five cycles of the catalyzing process, the TiO_2NWS@Au_NPS still retained over 90% of its catalytic ability for MB. The Au deposition was found responsible for the high catalytic activity of TiO_2NWS@Au_NPS. Full article

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11 pages, 2600 KiB

Open AccessArticle

Compressive Behavior and Constitutive Model of Austenitic Stainless Steel S30403 in High Strain Range

by Yang Peng, Jiang Chu and Jun Dong^*

College of Civil Engineering, Nanjing Tech University, Nanjing 211816, China

Materials 2018, 11(6), 1023; https://doi.org/10.3390/ma11061023 - 15 Jun 2018

Cited by 9 | Viewed by 4274

Abstract

Material anisotropy for tension and compression is a significant characteristic of austenitic stainless steel compared to carbon steel. Due to limitations during the testing of the restrained jig, the maximum strain value of compressive experiments of austenitic stainless steel is around 2%. This [...] Read more.

Material anisotropy for tension and compression is a significant characteristic of austenitic stainless steel compared to carbon steel. Due to limitations during the testing of the restrained jig, the maximum strain value of compressive experiments of austenitic stainless steel is around 2%. This value cannot satisfy the requirements of accurate finite simulation on austenitic stainless steel columns and beams in the high compressive strain range. In this study, a new type of compressive specimen that satisfies the high compressive strain test was designed. The stress-strain response of austenitic stainless steel S30403 (JISCO, Gansu, China) was investigated in the high compressive strain range up to 10%, and constitutive models were compared with the experimental data. It was found that the new type specimen with length-to-diameter ratio of 1:1 can reliably obtain the stress-strain response of austenitic stainless steel S30403 in the high compressive strain range. It was found that the material anisotropy of austenitic stainless steel S30403 is remarkable in the high compressive strain range up to 10%. The strain-hardening curve of the austenitic stainless steel S30403 can be represented by a straight line in the high compressive strain range. Our study also found that the Quach constitutive model accurately describes the two-stage strain-hardening phenomenon in the high compressive strain range up to 10%. Full article

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10 pages, 5486 KiB

Open AccessArticle

Effects of Different Hot Working Techniques on Inclusions in GH4738 Superalloy Produced by VIM and VAR

by Zhengyang Chen^1,2, Shufeng Yang^1,2,*, Jingshe Li^1,2, Hao Guo^1,2 and Hongbo Zheng^1,2

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China

² Beijing Key Laboratory of Special Melting and Preparation of High-End Metal Materials, Beijing 100083, China

Materials 2018, 11(6), 1024; https://doi.org/10.3390/ma11061024 - 15 Jun 2018

Cited by 14 | Viewed by 3852

Abstract

Hot working is a key process in the production of superalloys; however, it may result in the formation of inclusions that affect the superalloy performance. Therefore, the effects of hot working on inclusions in a superalloy must be studied. GH4738 superalloy was manufactured, [...] Read more.

Hot working is a key process in the production of superalloys; however, it may result in the formation of inclusions that affect the superalloy performance. Therefore, the effects of hot working on inclusions in a superalloy must be studied. GH4738 superalloy was manufactured, herein, by vacuum induction melting and vacuum arc remelting. Hot working was performed by unidirectional drawing, upsetting and drawing, and upsetting/drawing with radial forging. The types and distributions of inclusions after these three hot working processes and those in an original ingot were analyzed using scanning electron microscopy, energy dispersive spectroscopy, and Image-Pro Plus software. The results showed that the melting technology essentially determined the inclusion types in GH4738. Four types of inclusions were found in the experiments: TiC–TiN–Mo–S composite, TiC–TiN composite, Ce–Mo–S composite, and SiC inclusions. In the case of hot working by unidirectional drawing, the average inclusion size first decreased, and then increased from the center to the edge. In the case of upsetting and drawing, and upsetting/drawing with radial forging, the average inclusion size decreased from the center to the edge. Full article

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12 pages, 4151 KiB

Open AccessArticle

Effects of Annealing on the Residual Stress in γ-TiAl Alloy by Molecular Dynamics Simulation

by Ruicheng Feng^1,2

, Wenyuan Song¹, Haiyan Li^1,2,*, Yongnian Qi¹, Haiyang Qiao¹ and Longlong Li¹

¹ School of Mechanical and Electronical Engineering, Lanzhou University of Technology, Lanzhou 730050, China

² Key Laboratory of Digital Manufacturing Technology and Application, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China

Materials 2018, 11(6), 1025; https://doi.org/10.3390/ma11061025 - 15 Jun 2018

Cited by 24 | Viewed by 4722

Abstract

In this paper, molecular dynamics simulations are performed to study the annealing process of γ-TiAl alloy with different parameters after introducing residual stress into prepressing. By mainly focusing on the dynamic evolution process of microdefects during annealing and the distribution of residual stress, [...] Read more.

In this paper, molecular dynamics simulations are performed to study the annealing process of γ-TiAl alloy with different parameters after introducing residual stress into prepressing. By mainly focusing on the dynamic evolution process of microdefects during annealing and the distribution of residual stress, the relationship between microstructure and residual stress is investigated. The results show that there is no phase transition during annealing, but atom distortion occurs with the change of temperature, and the average grain size slightly increases after annealing. There are some atom clusters in the grains, with a few point defects, and the point defect concentration increases with the rise in temperature, and vice versa; the higher the annealing temperature, the fewer the point defects in the grain after annealing. Due to the grain boundary volume shrinkage and and an increase in the plastic deformation of the grain boundaries during cooling, stress is released, and the average residual stress along Y and Z directions after annealing is less than the average residual stress after prepressing. Full article

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8 pages, 3691 KiB

Open AccessArticle

Grain Size Effect on the Hot Ductility of High-Nitrogen Austenitic Stainless Steel in the Presence of Precipitates

by Zhenhua Wang^1,2,3,*

, Yong Wang¹ and Chengming Wang³

¹ School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China

² State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China

³ HBIS Group Technology Research Institute, Shijiazhuang 050023, China

Materials 2018, 11(6), 1026; https://doi.org/10.3390/ma11061026 - 15 Jun 2018

Cited by 11 | Viewed by 3748

Abstract

Precipitation occurs easily during the hot forming of high-nitrogen austenitic stainless steels, which reduces their hot ductility significantly. The effect of grain size on the hot ductility of high-nitrogen austenitic stainless steel in the presence of precipitates was investigated. Different grain sizes of [...] Read more.

Precipitation occurs easily during the hot forming of high-nitrogen austenitic stainless steels, which reduces their hot ductility significantly. The effect of grain size on the hot ductility of high-nitrogen austenitic stainless steel in the presence of precipitates was investigated. Different grain sizes of 18Mn18Cr0.5N steel specimens, with and without precipitates, were hot-tension tested. The precipitate morphology, fracture surface, and cracks were studied by scanning electron microscopy, transmission electron microscopy, and electron backscatter diffraction analysis. For the 18Mn18Cr0.5N steel, damage-formation strains of all grain-size specimens were reduced by the precipitates during the hot-tension test. Crack-formation sites were located at grain boundaries and were independent of the Taylor factor. A larger grain size resulted in an increased sensitivity of the fracture strain to precipitates. When the grain size was smaller than 51 μm, the fracture strain became insensitive to the precipitates. A method was suggested to mitigate surface cracking for metal materials with a high precipitation tendency. Full article

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10 pages, 2988 KiB

Open AccessArticle

An Investigation of the Wear on Silicon Surface at High Humidity

by Xiaodong Wang^1,2, Jian Guo^2,3, Lin Xu¹, Guanggui Cheng¹ and Linmao Qian^2,*

¹ Center of Micro/Nano Science and Technology, Jiangsu University, Zhenjiang 212013, China

² Tribology Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China

³ School of Mechanical Engineering, University of South China, Hengyang 421000, China

Materials 2018, 11(6), 1027; https://doi.org/10.3390/ma11061027 - 16 Jun 2018

Cited by 3 | Viewed by 3872

Abstract

Using an atomic force microscope (AFM), the wear of monocrystalline silicon (covered by a native oxide layer) at high humidity was investigated. The experimental results indicated that tribochemistry played an important role in the wear of the silicon at different relative humidity levels [...] Read more.

Using an atomic force microscope (AFM), the wear of monocrystalline silicon (covered by a native oxide layer) at high humidity was investigated. The experimental results indicated that tribochemistry played an important role in the wear of the silicon at different relative humidity levels (RH = 60%, 90%). Since the tribochemical reactions were facilitated at 60% RH, the wear of silicon was serious and the friction force was around 1.58 μN under the given conditions. However, the tribochemical reactions were restrained when the wear pair was conducted at high humidity. As a result, the wear of silicon was very slight and the friction force decreased to 0.85 μN at 90% RH. The slight wear of silicon at high humidity was characterized by etching tests. It was demonstrated that the silicon sample surface was partly damaged and the native oxide layer on silicon sample surface had not been totally removed during the wear process. These results may help us optimize the tribological design of dynamic microelectromechanical systems working in humid conditions. Full article

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16 pages, 4173 KiB

Open AccessArticle

Fatigue Behavior of Glass Fiber-Reinforced Polymer Bars after Elevated Temperatures Exposure

by Guanghui Li¹, Jun Zhao^2,*

and Zike Wang²

¹ School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China

² School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou 450001, China

Materials 2018, 11(6), 1028; https://doi.org/10.3390/ma11061028 - 16 Jun 2018

Cited by 25 | Viewed by 5367

Abstract

Fiber-reinforced polymer (FRP) bars have been widely applied in civil engineering. This paper presents the results of an experimental study to investigate the tensile fatigue mechanical properties of glass fiber-reinforced polymer (GFRP) bars after elevated temperatures exposure. For this purpose, a total of [...] Read more.

Fiber-reinforced polymer (FRP) bars have been widely applied in civil engineering. This paper presents the results of an experimental study to investigate the tensile fatigue mechanical properties of glass fiber-reinforced polymer (GFRP) bars after elevated temperatures exposure. For this purpose, a total of 105 GFRP bars were conducted for testing. The specimens were exposed to heating regimes of 100, 150, 200, 250, 300 and 350 °C for a period of 0, 1 or 2 h. The GFRP bars were tested with different times of cyclic load after elevated temperatures exposure. The results show that the tensile strength and elastic modulus of GFRP bars decrease with the increase of elevated temperature and holding time, and the tensile strength of GFRP bars decreases obviously by 19.5% when the temperature reaches 250 °C. Within the test temperature range, the tensile strength of GFRP bars decreases at most by 28.0%. The cyclic load accelerates the degradation of GFRP bars after elevated temperature exposure. The coupling of elevated temperature and holding time enhance the degradation effect of cyclic load on GFRP bars. The tensile strength of GFRP bars after elevated temperatures exposure at 350 °C under cyclic load is reduced by 50.5% compared with that at room temperature and by 36.3% compared with that after exposing at 350 °C without cyclic load. In addition, the elastic modulus of GFRP bars after elevated temperatures exposure at 350 °C under cyclic load is reduced by 17.6% compared with that at room temperature and by 6.0% compared with that after exposing at 350 °C without cyclic load. Full article

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13 pages, 2750 KiB

Open AccessArticle

Concrete Properties Comparison When Substituting a 25% Cement with Slag from Different Provenances

by María Eugenia Parron-Rubio¹

, Francisca Perez-García^2,*, Antonio Gonzalez-Herrera² and María Dolores Rubio-Cintas¹

¹ Departamento de Ingeniería Industrial y Civil, Universidad de Cádiz, 11205 Algeciras, Spain

² Departamento de Ingeniería Civil, Materiales y Fabricación, Universidad de Málaga, 29071 Málaga, Spain

Materials 2018, 11(6), 1029; https://doi.org/10.3390/ma11061029 - 17 Jun 2018

Cited by 45 | Viewed by 5728

Abstract

Concrete consumption greatly exceeds the use of any other material in engineering. This is due to its good properties as a construction material and the availability of its components. Nevertheless, the present worldwide construction increases and the high-energy consumption for cement production means [...] Read more.

Concrete consumption greatly exceeds the use of any other material in engineering. This is due to its good properties as a construction material and the availability of its components. Nevertheless, the present worldwide construction increases and the high-energy consumption for cement production means a high environmental impact. On the other hand, one of the main problems in the iron and steel industry is waste generation and byproducts that must be properly processed or reused to promote environmental sustainability. One of these byproducts is steel slag. The cement substitution with slag strategy achieves two goals: raw materials consumption reduction and waste management. In the present work, four different concrete mixtures are evaluated. The 25% cement substitution is carried out with different types of slag. Tests were made to evaluate the advantages and drawbacks of each mixture. Depending on the origin, characteristics, and treatment of the slag, the concrete properties changed. Certain mixtures provided proper concrete properties. Stainless steel slag produced a fluent mortar that reduced water consumption with a slight mechanical strength loss. Mixtures with ground granulated blast furnace slag properties are better than the reference concrete (without slag). Full article

(This article belongs to the Collection Additive Manufacturing: Alloy Design and Process Innovations)

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17 pages, 5788 KiB

Open AccessArticle

Degradation of Methylene Blue Dye in the Presence of Visible Light Using SiO₂@α-Fe₂O₃ Nanocomposites Deposited on SnS₂ Flowers

by Sridharan Balu¹

, Kasimayan Uma^2,*, Guan-Ting Pan¹

, Thomas C.-K. Yang^1,2,*

and Sayee Kannan Ramaraj³

¹ Department of Chemical Engineering and biotechnology, National Taipei University of Technology, Taipei 106, Taiwan, bsridharanbsc.12@gmail.com (S.B.)

² Precision Analysis and Research Center, National Taipei University of Technology, Taipei 106, Taiwan

³ PG & Research Department of Chemistry, Thiagarajar College, Madurai 625009, Tamilnadu, India

Materials 2018, 11(6), 1030; https://doi.org/10.3390/ma11061030 - 17 Jun 2018

Cited by 135 | Viewed by 7423

Abstract

Semiconductor materials have been shown to have good photocatalytic behavior and can be utilized for the photodegradation of organic pollutants. In this work, three-dimensional flower-like SnS₂ (tin sulfide) was synthesized by a facile hydrothermal method. Core-shell structured SiO₂@α-Fe₂O [...] Read more.

Semiconductor materials have been shown to have good photocatalytic behavior and can be utilized for the photodegradation of organic pollutants. In this work, three-dimensional flower-like SnS₂ (tin sulfide) was synthesized by a facile hydrothermal method. Core-shell structured SiO₂@α-Fe₂O₃ nanocomposites were then deposited on the top of the SnS₂ flowers. The as-synthesized nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis Spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, and photoluminescence (PL) spectroscopy. The photocatalytic behavior of the SnS₂-SiO₂@α-Fe₂O₃ nanocomposites was investigated by observing the degradation of methylene blue (MB). The results show an effective enhancement of photocatalytic activity for the degradation of MB especially for the 15 wt % SiO₂@α-Fe₂O₃ nanocomposites on SnS₂ flowers. Full article

(This article belongs to the Section Catalytic Materials)

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27 pages, 4460 KiB

Open AccessArticle

Properties of Experimental Dental Composites Containing Antibacterial Silver-Releasing Filler

by Robert Stencel¹, Jacek Kasperski², Wojciech Pakieła³, Anna Mertas⁴

, Elżbieta Bobela⁴, Izabela Barszczewska-Rybarek⁵

and Grzegorz Chladek^3,*

¹ Private Practice, Center of Dentistry and Implantology, ul. Karpińskiego 3, 41-500 Chorzów, Poland

² Department of Prosthetic Dentistry, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia, pl. Akademicki 17, 41-902 Bytom, Poland

³ Faculty of Mechanical Engineering, Institute of Engineering Materials and Biomaterials, Silesian University of Technology, ul. Konarskiego 18a, 44-100 Gliwice, Poland

⁴ Chair and Department of Microbiology and Immunology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia in Katowice, ul. Jordana 19, 41-808 Zabrze, Poland

⁵ Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, 44-100 Gliwice, Poland

Materials 2018, 11(6), 1031; https://doi.org/10.3390/ma11061031 - 18 Jun 2018

Cited by 52 | Viewed by 7121 | Correction

Abstract

Secondary caries is one of the important issues related to using dental composite restorations. Effective prevention of cariogenic bacteria survival may reduce this problem. The aim of this study was to evaluate the antibacterial activity and physical properties of composite materials with silver [...] Read more.

Secondary caries is one of the important issues related to using dental composite restorations. Effective prevention of cariogenic bacteria survival may reduce this problem. The aim of this study was to evaluate the antibacterial activity and physical properties of composite materials with silver sodium hydrogen zirconium phosphate (SSHZP). The antibacterial filler was introduced at concentrations of 1%, 4%, 7%, 10%, 13%, and 16% (w/w) into model composite material consisting of methacrylate monomers and silanized glass and silica fillers. The in vitro reduction in the number of viable cariogenic bacteria Streptococcus mutans ATCC 33535 colonies, Vickers microhardness, compressive strength, diametral tensile strength, flexural strength, flexural modulus, sorption, solubility, degree of conversion, and color stability were investigated. An increase in antimicrobial filler concentration resulted in a statistically significant reduction in bacteria. There were no statistically significant differences caused by the introduction of the filler in compressive strength, diametral tensile strength, flexural modulus, and solubility. Statistically significant changes in degree of conversion, flexural strength, hardness (decrease), solubility (increase), and in color were registered. A favorable combination of antibacterial properties and other properties was achieved at SSHZP concentrations from 4% to 13%. These composites exhibited properties similar to the control material and enhanced in vitro antimicrobial efficiency. Full article

(This article belongs to the Special Issue Bioactive and Therapeutic Dental Materials)

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11 pages, 1087 KiB

Open AccessFeature PaperArticle

Copolymerization of UF Resins with Dimethylurea for Improving Storage Stability without Impairing Adhesive Performance

by Pedro Pereira¹, João Pereira², Nádia. T. Paiva¹, João. M. Ferra¹, Jorge M. Martins^3,4, Luísa. H. Carvalho^3,4

and Fernão. D. Magalhães^4,*

¹ EuroResinas-Indústrias Químicas, 7520 Sines, Portugal

² ARCP—Associação Rede de Competência em Polímeros, 4200 Porto, Portugal

³ DEMad—Instituto Politécnico de Viseu, 3504 Viseu, Portugal

⁴ LEPABE—Faculdade de Engenharia da Universidade do Porto, 4200 Porto, Portugal

Materials 2018, 11(6), 1032; https://doi.org/10.3390/ma11061032 - 19 Jun 2018

Cited by 7 | Viewed by 4224

Abstract

Urea-formaldehyde (UF) resins are the most used resins in the wood industry due to high reactivity and low price. However, their reduced stability during storage is a drawback, imposing strict limits in terms of allowable shipping distances and storage times. This instability, manifested [...] Read more.

Urea-formaldehyde (UF) resins are the most used resins in the wood industry due to high reactivity and low price. However, their reduced stability during storage is a drawback, imposing strict limits in terms of allowable shipping distances and storage times. This instability, manifested by viscosity increase that renders the resin unusable, occurs due to the progress of condensation reactions between the polymeric species present in the liquid medium. In order to achieve a stable resin formulation, dimethylurea (DMeU) was selected for being less reactive than urea. Dimethylurea is shown to co-polymerize with the UF polymer during the acidic synthesis condensation step. However, during storage it behaves like an end group blocker, due to its lower reactivity at basic pH. By adding 1.25% DMeU, it was possible to obtain a formulation that remained with stable viscosity during two-month storage at 40 °C. The reference UF resin remained stable only for eight days in these conditions. Wood particleboards produced with modified resins showed internal bond strengths of about 0.5 N·mm⁻², similar to the fresh reference UF resin, even when the resins were used after the two-month storage period. Formaldehyde content values were below the limit for E1 class, ≤8 mg/100 g oven dry board (EN 13986). Full article

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12 pages, 3383 KiB

Open AccessArticle

Characterization and Microstructure of Linear Electrode-Electrospun Graphene-Filled Polyvinyl Alcohol Nanofiber Films

by Ting-Ting Li^1,2, Mengxue Yan¹, Qian Jiang¹, Hao-Kai Peng¹, Jia-Horng Lin^1,3,4,5,6,7 and Ching-Wen Lou^2,4,7,8,*

¹ Innovation Platform of Intelligent and Energy-Saving Textiles, Tianjin Polytechnic University, Tianjin 300387, China

² Fujian Key Laboratory of Novel Functional Fibers and Materials, Minjiang University, Fuzhou 350108, China

³ Laboratory of Fiber Application and Manufacturing, Department of Fiber and Composite Materials, Feng Chia University, Taichung 40724, Taiwan

⁴ Department of Chemical Engineering and Materials, Ocean College, Minjiang University, Fuzhou 350108, China

⁵ Department of Fashion Design, Asia University, Taichung 41354, Taiwan

⁶ School of Chinese Medicine, China Medical University, Taichung 40402, Taiwan

⁷ College of Textile and Clothing, Qingdao University, Shandong 266071, China

⁸ Department of Bioinformatics and Medical Engineering, Asia University, Taichung 41354, Taiwan

Materials 2018, 11(6), 1033; https://doi.org/10.3390/ma11061033 - 19 Jun 2018

Cited by 10 | Viewed by 3629

Abstract

With the aim of achieving controllable mass production of electrospun nanofiber films, this study proposes and investigates the feasibility of using a custom-made linear electrode- electrospun device to produce conductive graphene (GR)-filled polyvinyl alcohol (PVA) nanofibers. The film morphology and diameter of nanofibers [...] Read more.

With the aim of achieving controllable mass production of electrospun nanofiber films, this study proposes and investigates the feasibility of using a custom-made linear electrode- electrospun device to produce conductive graphene (GR)-filled polyvinyl alcohol (PVA) nanofibers. The film morphology and diameter of nanofibers are observed and measured to examine the effects of viscosity and conductivity of the PVA/GR mixtures. Likewise, the influence of the content of graphene on the hydrophilicity, electrical conductivity, electromagnetic interference shielding effectiveness (EMSE), and thermal stability of the PVA/GR nanofiber films is investigated. The test results show that the PVA/GR mixture has greater viscosity and electric conductivity than pure PVA solution and can be electrospun into PVA/GR nanofiber films that have good morphology and diameter distribution. The diameter of the nanofibers is 100 nm and the yield is 2.24 g/h, suggesting that the process qualifies for use in large-scale production. Increasing the content of graphene yields finer nanofibers, a smaller surface contact angle, and higher hydrophilicity of the nanofiber films. The presence of graphene is proven to improve the thermal stability and strengthens the EMSE by 20 dB at 150–1500 MHz. Mass production is proven to be feasible by the test results showing that PVA/GR nanofiber films can be used in the medical hygiene field. Full article

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9 pages, 4064 KiB

Open AccessArticle

Noninvasive Mechanochemical Imaging in Unconstrained Caenorhabditis elegans

by Takuma Sugi^1,2,*, Ryuji Igarashi^2,3,4,* and Masaki Nishimura¹

¹ Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan

² PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan

³ QST Future Laboratory, National Institute for Quantum and Radiological Science and Technology, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan

⁴ Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan

Materials 2018, 11(6), 1034; https://doi.org/10.3390/ma11061034 - 19 Jun 2018

Cited by 6 | Viewed by 4033

Abstract

Physical forces are transduced into chemical reactions, thereby ultimately making a large impact on the whole-animal level phenotypes such as homeostasis, development and behavior. To understand mechano-chemical transduction, mechanical input should be quantitatively delivered with controllable vibration properties–frequency, amplitude and duration, and its [...] Read more.

Physical forces are transduced into chemical reactions, thereby ultimately making a large impact on the whole-animal level phenotypes such as homeostasis, development and behavior. To understand mechano-chemical transduction, mechanical input should be quantitatively delivered with controllable vibration properties–frequency, amplitude and duration, and its chemical output should be noninvasively quantified in an unconstrained animal. However, such an experimental system has not been established so far. Here, we develop a noninvasive and unconstrained mechanochemical imaging microscopy. This microscopy enables us to evoke nano-scale nonlocalized vibrations with controllable vibration properties using a piezoelectric acoustic transducer system and quantify calcium response of a freely moving C. elegans at a single cell resolution. Using this microscopy, we clearly detected the calcium response of a single interneuron during C. elegans escape response to nano-scale vibration. Thus, this microscopy will facilitate understanding of in vivo mechanochemical physiology in the future. Full article

(This article belongs to the Special Issue Smart Materials for Soft Sensors and Actuators)

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23 pages, 5691 KiB

Open AccessArticle

Pore Structure Characterization of Sodium Hydroxide Activated Slag Using Mercury Intrusion Porosimetry, Nitrogen Adsorption, and Image Analysis

by Yibing Zuo^*

and Guang Ye

Microlab, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, The Netherlands

Materials 2018, 11(6), 1035; https://doi.org/10.3390/ma11061035 - 19 Jun 2018

Cited by 37 | Viewed by 6890

Abstract

The pore structure of alkali-activated slag has a significant influence on its performance. However, the literature shows insufficient studies regarding the suitability of different techniques for characterizing the pore structure and the influences of Na₂O and curing age on pore structure [...] Read more.

The pore structure of alkali-activated slag has a significant influence on its performance. However, the literature shows insufficient studies regarding the suitability of different techniques for characterizing the pore structure and the influences of Na₂O and curing age on pore structure development. In pursuit of a better understanding, the pore structure of sodium hydroxide activated slag paste was characterized by multiple techniques, e.g., mercury intrusion porosimetry (MIP), nitrogen (N₂) adsorption, and scanning electron microscopy (SEM) image analysis. The sodium hydroxide activated slag pastes were prepared with three different contents of Na₂O (Na₂O/slag = 4, 6, and 8%) and cured for different times up to 360 days. The microstructure observation reveals that outer C–(N–)A–S–H and inner C–(N–)A–S–H grow successively around the reacting slag grains, along with crystalline reaction products which are formed in the empty coarse pore space. The increase of Na₂O content and curing age lead to a finer pore structure. The MIP measurements show that the total porosity drops about 70% within the first day, and that one peak at most, corresponding to gel pores, was identified in the differential curves of all the investigated samples from 1 to 360 days. On the contrary, only one peak, corresponding to capillary pores, was identified by SEM-image analysis. The differential curves derived from N₂ adsorption generally reveal two peaks, and the trend that the pore diameters of those two peaks vary with curing age depends on the content of Na₂O. Compared to Portland cement, sodium hydroxide activated slag has a higher pore space filling capacity (χ, V_products/V_slag-reacted), while the capacity decreases with increasing Na₂O content and curing age. Full article

(This article belongs to the Section Porous Materials)

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16 pages, 4921 KiB

Open AccessFeature PaperArticle

Single Step Laser Transfer and Laser Curing of Ag NanoWires: A Digital Process for the Fabrication of Flexible and Transparent Microelectrodes

by Filimon Zacharatos^1,*

, Panagiotis Karvounis², Ioannis Theodorakos¹

, Antonios Hatziapostolou² and Ioanna Zergioti¹

¹ Physics Department, Zografou Campus, National Technical University of Athens, Athens 15780, Greece

² Campus 1, School of Engineering, University of West Attica, Aigaleo 12243, Greece

Materials 2018, 11(6), 1036; https://doi.org/10.3390/ma11061036 - 19 Jun 2018

Cited by 18 | Viewed by 4278

Abstract

Ag nanowire (NW) networks have exquisite optical and electrical properties which make them ideal candidate materials for flexible transparent conductive electrodes. Despite the compatibility of Ag NW networks with laser processing, few demonstrations of laser fabricated Ag NW based components currently exist. In [...] Read more.

Ag nanowire (NW) networks have exquisite optical and electrical properties which make them ideal candidate materials for flexible transparent conductive electrodes. Despite the compatibility of Ag NW networks with laser processing, few demonstrations of laser fabricated Ag NW based components currently exist. In this work, we report on a novel single step laser transferring and laser curing process of micrometer sized pixels of Ag NW networks on flexible substrates. This process relies on the selective laser heating of the Ag NWs induced by the laser pulse energy and the subsequent localized melting of the polymeric substrate. We demonstrate that a single laser pulse can induce both transfer and curing of the Ag NW network. The feasibility of the process is confirmed experimentally and validated by Finite Element Analysis simulations, which indicate that selective heating is carried out within a submicron-sized heat affected zone. The resulting structures can be utilized as fully functional flexible transparent electrodes with figures of merit even higher than 100. Low sheet resistance (<50 Ohm/sq) and high visible light transparency (>90%) make the reported process highly desirable for a variety of applications, including selective heating or annealing of nanocomposite materials and laser processing of nanostructured materials on a large variety of optically transparent substrates, such as Polydimethylsiloxane (PDMS). Full article

(This article belongs to the Special Issue Selective Laser Sintering (SLS) of Materials)

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10 pages, 3274 KiB

Open AccessArticle

High-Temperature Tolerance in Multi-Scale Cermet Solar-Selective Absorbing Coatings Prepared by Laser Cladding

by Xuming Pang^*

, Qian Wei, Jianxin Zhou and Huiyang Ma

School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China

Materials 2018, 11(6), 1037; https://doi.org/10.3390/ma11061037 - 19 Jun 2018

Cited by 11 | Viewed by 4022

Abstract

In order to achieve cermet-based solar absorber coatings with long-term thermal stability at high temperatures, a novel single-layer, multi-scale TiC-Ni/Mo cermet coating was first prepared using laser cladding technology in atmosphere. The results show that the optical properties of the cermet coatings using [...] Read more.

In order to achieve cermet-based solar absorber coatings with long-term thermal stability at high temperatures, a novel single-layer, multi-scale TiC-Ni/Mo cermet coating was first prepared using laser cladding technology in atmosphere. The results show that the optical properties of the cermet coatings using laser cladding were much better than the preplaced coating. In addition, the thermal stability of the optical properties for the laser cladding coating were excellent after annealing at 650 °C for 200 h. The solar absorptance and thermal emittance of multi-scale cermet coating were 85% and 4.7% at 650 °C. The results show that multi-scale cermet materials are more suitable for solar-selective absorbing coating. In addition, laser cladding is a new technology that can be used for the preparation of spectrally-selective coatings. Full article

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21 pages, 3458 KiB

Open AccessArticle

Influence of Microstructure and Shot Peening Treatment on Corrosion Resistance of AISI F55-UNS S32760 Super Duplex Stainless Steel

by Andrea Francesco Ciuffini^1,*

, Silvia Barella¹

, Luis Borja Peral Martínez², Carlo Mapelli¹ and Inés Fernández Pariente²

¹ Dipartimento di Meccanica, Politecnico di Milano, via La Masa 34, 20156 Milano, Italy

² Escuela Politécnica de Ingeniería de Gijón, Universidad de Oviedo, Campus de Viesques, Gijón 33203, Spain

Materials 2018, 11(6), 1038; https://doi.org/10.3390/ma11061038 - 19 Jun 2018

Cited by 14 | Viewed by 5163

Abstract

Shot peening is a surface process commonly used in the aeronautic and automotive industries to improve fatigue resistance. Shot peening is proven to be beneficial in the fatigue behavior of components, but rarely has its influence on wear and pitting corrosion resistance been [...] Read more.

Shot peening is a surface process commonly used in the aeronautic and automotive industries to improve fatigue resistance. Shot peening is proven to be beneficial in the fatigue behavior of components, but rarely has its influence on wear and pitting corrosion resistance been evaluated. In this work, shot peening was performed on AISI F55-UNS S32760 super-duplex stainless steel samples previously submitted to various thermal treatments, to obtain different initial microstructures and properties. Samples have been characterized in terms of microstructure morphology, local chemical composition, microhardness of each constituent phase, and energy dissipation modes. The enhanced properties provided by shot peening has been evaluated through residual stress depth profiles and Full Width at Half Maximum (FWHM) using X-ray diffraction (XRD), surface hardness, surface roughness, and corrosion resistance through salt spray fog tests. The 1400 °C solution thermal treatment was identified as the optimum initial condition, which maximizes the advantages of the shot peening treatment, even pitting corrosion resistance. These results are related to the uniformity of austenite and ferrite in terms of microstructure morphology, micromechanical properties, and alloying elements distribution. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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11 pages, 4546 KiB

Open AccessArticle

Giant Enhancement of Magnetostrictive Response in Directionally-Solidified Fe₈₃Ga₁₇Er_x Compounds

by Radhika Barua^1,*, Parisa Taheri¹, Yajie Chen¹, Anjela Koblischka-Veneva²

, Michael R. Koblischka²

, Liping Jiang³ and Vincent G. Harris^1,*

¹ College of Engineering, Northeastern University, Boston, MA 02115, USA

² Institute of Experimental Physics, Saarland University, 66123 Saarbrucken, Germany

³ Baotou Research Institute of Rare Earths, Baotou 014010 China

Materials 2018, 11(6), 1039; https://doi.org/10.3390/ma11061039 - 19 Jun 2018

Cited by 29 | Viewed by 4596

Abstract

We report, for the first time, correlations between crystal structure, microstructure and magnetofunctional response in directionally solidified [110]-textured Fe₈₃Ga₁₇Er_x (0 < x < 1.2) alloys. The morphology of the doped samples consists of columnar grains, mainly composed of [...] Read more.

We report, for the first time, correlations between crystal structure, microstructure and magnetofunctional response in directionally solidified [110]-textured Fe₈₃Ga₁₇Er_x (0 < x < 1.2) alloys. The morphology of the doped samples consists of columnar grains, mainly composed of a matrix phase and precipitates of a secondary phase deposited along the grain boundary region. An enhancement of more than ~275% from ~45 to 170 ppm is observed in the saturation magnetostriction value (λ_s) of Fe₈₃Ga₁₇Er_x alloys with the introduction of small amounts of Er. Moreover, it was noted that the low field derivative of magnetostriction with respect to an applied magnetic field (

i . e ., d λ_{s} / d H_{a p p}

for H_app up to 1000 Oe) increases by ~230% with Er doping (

d λ_{s} / d H_{a p p, FeGa} =

0.045 ppm/Oe;

d λ_{s} / d H_{a p p, FeGaEr} =

0.15 ppm/Oe). The enhanced magnetostrictive response of the Fe₈₃Ga₁₇Er_x alloys is ascribed to an amalgamation of microstructural and electronic factors, namely: (i) improved grain orientation and local strain effects due to deposition of Er in the intergranular region; and (ii) strong local magnetocrystalline anisotropy, due to the highly anisotropic localized nature of the 4f electronic charge distribution of the Er atom. Overall, this work provides guidelines for further improving galfenol-based materials systems for diverse applications in the power and energy sector. Full article

(This article belongs to the Special Issue Magnetostrictive Composite Materials)

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19 pages, 6501 KiB

Open AccessArticle

Elucidating the Photocatalytic Behavior of TiO₂-SnS₂ Composites Based on Their Energy Band Structure

by Marin Kovacic

, Jozefina Katic

, Hrvoje Kusic^*, Ana Loncaric Bozic and Mirjana Metikos Hukovic^*

Faculty of Chemical Engineering and Technology, University of Zagreb, Marulicev trg 19, Zagreb 10000, Croatia

Materials 2018, 11(6), 1041; https://doi.org/10.3390/ma11061041 - 19 Jun 2018

Cited by 22 | Viewed by 5765

Abstract

TiO₂-SnS₂ composite semiconducting photocatalysts with different building component ratios were prepared by hydrothermal synthesis (TiO₂-SnS₂-HT) and by immobilization of commercial TiO₂ and SnS₂ particles (TiO₂-SnS₂-COMM). The band gap values, which [...] Read more.

TiO₂-SnS₂ composite semiconducting photocatalysts with different building component ratios were prepared by hydrothermal synthesis (TiO₂-SnS₂-HT) and by immobilization of commercial TiO₂ and SnS₂ particles (TiO₂-SnS₂-COMM). The band gap values, which determine the catalysts’ photoactivity, were examined by diffuse reflectance spectroscopy and Kubelka–Munk transformations. The catalysts’ surface properties: specific surface area, charge and adsorption capacitance at the solid–solution interface were characterized using BET analysis, potentiometric titration and electrochemical impedance spectroscopy, respectively. The electronic band structure of TiO₂-SnS₂ photocatalyst, as the key property for the solar-driven photocatalysis, was deduced from the thermodynamic data and the semiconducting parameters (type of semiconductivity, concentration of the charge carriers, flat band potential) obtained by Mott–Schottky analysis. The photoactivity of both composites was studied in photocatalytic treatment of diclofenac (DCF) under simulated solar irradiation and was compared to the benchmark photocatalyst (TiO₂ P25) activity. The influence of process parameters, such as pH, H₂O₂, and composite formulation on the effectiveness of DCF removal and conversion was investigated and discussed by employing response surface modeling (RSM) approach. The photocatalytic efficiency of both composite materials was discussed on the basis of the hetereojunction formation that facilitated the photoelectron transfer, promoting more efficient photocatalytic degradation of DCF. Full article

(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)

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17 pages, 7653 KiB

Open AccessArticle

Experimental and Theoretical Investigation of Thiazolyl Blue as a Corrosion Inhibitor for Copper in Neutral Sodium Chloride Solution

by Li Feng¹, Shengtao Zhang^1,2,*, Yujie Qiang¹, Yue Xu¹, Lei Guo^3,*

, Loutfy H. Madkour⁴

and Shijin Chen⁵

¹ School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China

² Material Corrosion and Protection Key Laboratory of Sichuan province, Zigong 643000, China

³ School of Material and Chemical Engineering, Tongren University, Tongren 554300, China

⁴ Chemistry Department, Faculty of Science and Arts, Al Baha University, Baljarashi 65635, Saudi Arabia

⁵ Bomin Electronics Ltd., Meizhou 514021, China

Materials 2018, 11(6), 1042; https://doi.org/10.3390/ma11061042 - 19 Jun 2018

Cited by 60 | Viewed by 7568

Abstract

The anticorrosion effect of thiazolyl blue (MTT) for copper in 3% NaCl at 298 K was researched by electrochemical methods, scanning electron-microscopy (SEM), and atomic force microscopy (AFM). The results reveal that MTT can protect copper efficiently, with a maximum efficiency of 95.7%. [...] Read more.

The anticorrosion effect of thiazolyl blue (MTT) for copper in 3% NaCl at 298 K was researched by electrochemical methods, scanning electron-microscopy (SEM), and atomic force microscopy (AFM). The results reveal that MTT can protect copper efficiently, with a maximum efficiency of 95.7%. The corrosion inhibition mechanism was investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectral (FT-IR), and theoretical calculation. The results suggest that the MTT molecules are adsorbed on metal surface forming a hydrophobic protective film to prevent copper corrosion. It also indicates that the MTT and copper form covalent bonds. The molecular dynamic simulation further gives the evidence for adsorption. The adsorption isotherm studies demonstrate that a spontaneous, mixed physical and chemical adsorption occurs, which obeys Langmuir adsorption isotherm. The present research can help us better understand the corrosion inhibition process and improve it. Full article

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10 pages, 2735 KiB

Open AccessArticle

Wear Resistance of 3D Printing Resin Material Opposing Zirconia and Metal Antagonists

by Ji-Man Park¹

, Jin-Soo Ahn², Hyun-Suk Cha³ and Joo-Hee Lee^3,*

¹ Department of Prosthodontics, College of Dentistry, Yonsei University, 250 Seongsanno, Seodaemun-gu, Seoul 03722, Korea

² Department of Dental Biomaterials Science and Dental Research Institute, School of Dentistry, Seoul National University, 101 Daehak-ro, Jongno-gu, Seoul 03080, Korea

³ Division of Prosthodontics, Department of Dentistry, Asan Medical Center, College of Medicine, University of Ulsan, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea

Materials 2018, 11(6), 1043; https://doi.org/10.3390/ma11061043 - 20 Jun 2018

Cited by 56 | Viewed by 8061

Abstract

3D printing offers many advantages in dental prosthesis manufacturing. This study evaluated the wear resistance of 3D printing resin material compared with milling and conventional resin materials. Sixty substrate specimens were prepared with three types of resin materials: 3D printed resin, milled resin, [...] Read more.

3D printing offers many advantages in dental prosthesis manufacturing. This study evaluated the wear resistance of 3D printing resin material compared with milling and conventional resin materials. Sixty substrate specimens were prepared with three types of resin materials: 3D printed resin, milled resin, and self-cured resin. The 3D printed specimens were printed at a build angle of 0° and 100 μm layer thickness by digital light processing 3D printing. Two kinds of abraders were made of zirconia and CoCr alloy. The specimens were loaded at 5 kg for 30,000 chewing cycles with vertical and horizontal movements under thermocycling condition. The 3D printed resin did not show significant difference in the maximal depth loss or the volume loss of wear compared to the milled and the self-cured resins. No significant difference was revealed depending on the abraders in the maximal depth loss or the volume loss of wear. In SEM views, the 3D printed resin showed cracks and separation of inter-layer bonds when opposing the metal abrader. The results suggest that the 3D printing using resin materials provides adequate wear resistance for dental use. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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18 pages, 42031 KiB

Open AccessArticle

Hot Deformation Behavior and Microstructure Evolution of 14Cr ODS Steel

by Qian Zhao, Liming Yu, Zongqing Ma, Huijun Li, Zumin Wang and Yongchang Liu^*

State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science & Engineering, Tianjin University, Tianjin 300354, China

Materials 2018, 11(6), 1044; https://doi.org/10.3390/ma11061044 - 20 Jun 2018

Cited by 17 | Viewed by 4850

Abstract

Hot deformation tests of 14Cr oxide dispersion strengthened (ODS) steel fabricated by mechanical alloying and hot isostatic pressing (HIP) were performed on a Gleeble-1500D simulator at temperatures ranging from 1050 to 1200 °C with the strain rate range of 0.001⁻¹ s⁻¹ [...] Read more.

Hot deformation tests of 14Cr oxide dispersion strengthened (ODS) steel fabricated by mechanical alloying and hot isostatic pressing (HIP) were performed on a Gleeble-1500D simulator at temperatures ranging from 1050 to 1200 °C with the strain rate range of 0.001⁻¹ s⁻¹. The relationship between the rheological stress and the deformation condition was studied, and a processing map at the true strain of 0.5 was proposed. Microstructure evolution during the deformation process and the effects of deformation conditions on microstructures were also investigated, as well as the stability of nanoparticles. Results show that the 14Cr ODS steel possesses positive strain rate sensitivity. The flow stress increases with the decrease of deformation temperature and the increase of strain rate. The recrystallization process is promoted by the increase of deformation temperature and the reduction of strain rate. Nanoparticles possess excellent stability during the deformation process and are coherent with the matrix. Full article

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16 pages, 4770 KiB

Open AccessArticle

A Novel Multiscale Mathematical Model for Building Bone Substitute Materials for Children

by Abdennasser Chekroun^1,†, Laurent Pujo-Menjouet^2,†

and Jean-Philippe Berteau^3,4,5,*

¹ Laboratoire d’Analyse Non Linéaire et Mathématiques Appliquées, University of Tlemcen, Chetouane 13000, Algeria

² Université de Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5208, Institut Camille Jordan, F-69622 Villeurbanne CEDEX, France; Inria Team Dracula, Inria Grenoble Rhône-Alpes Center, 69100 Villeurbanne CEDEX, France

³ Department of Physical Therapy, College of Staten Island, City University of New York, New York, NY 10314, USA

⁴ New York Center for Biomedical Engineering, City College of New York, City University of New York, New York, NY 10031, USA

⁵ Nanoscience Initiative, Advance Science Research Center, City University of New York, New York, NY 10031, USA

^† These authors contributed equally to this work.

Materials 2018, 11(6), 1045; https://doi.org/10.3390/ma11061045 - 20 Jun 2018

Cited by 2 | Viewed by 4063

Abstract

Bone is an engineering marvel that achieves a unique combination of stiffness and toughness exceeding that of synthesized materials. In orthopedics, we are currently challenged for the child population that needs a less stiff but a tougher bone substitute than adults. Recent evidence [...] Read more.

Bone is an engineering marvel that achieves a unique combination of stiffness and toughness exceeding that of synthesized materials. In orthopedics, we are currently challenged for the child population that needs a less stiff but a tougher bone substitute than adults. Recent evidence suggests that the relationship between inter-molecular connections that involve the two main bone building blocks, TropoCollagen molecules (TC) and carbonated Hydroxyapatite (cAp), and bone macroscopic mechanical properties, stiffness and toughness, are key to building bone substitute materials for children. The goal of our study is to establish how inter-molecular connections that occur during bone mineralization are related to macroscopic mechanical properties in child bones. Our aim is to link the biological alterations of the TC-cAp self assembly process happening during bone mineralization to the bone macroscopic mechanical properties’ alterations during aging. To do so, we have developed a multiscale mathematical model that includes collagen cross links (TC–TC interface) from experimental studies of bone samples to forecast bone macroscopic mechanical properties. Our results support that the Young’s modulus cannot be a linear parameter if we want to solve our system. In relation to bone substitute material with innovative properties for children, our results propose values of several biological parameters, such as the number of crystals and their size, and collagen crosslink maturity for the desired bone mechanical competence. Our novel mathematical model combines mineralization and macroscopic mechanical behavior of bone and is a step forward in building mechanically customized biomimetic bone grafts that would fit children’s orthopedic needs. Full article

(This article belongs to the Special Issue Bone Substitute Materials)

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15 pages, 5295 KiB

Open AccessArticle

Quadratic Solid–Shell Finite Elements for Geometrically Nonlinear Analysis of Functionally Graded Material Plates

by Hocine Chalal and Farid Abed-Meraim^*

Laboratory LEM3, Université de Lorraine, CNRS, Arts et Métiers ParisTech, F-57000 Metz, France

Materials 2018, 11(6), 1046; https://doi.org/10.3390/ma11061046 - 20 Jun 2018

Cited by 9 | Viewed by 5102

Abstract

In the current contribution, prismatic and hexahedral quadratic solid–shell (SHB) finite elements are proposed for the geometrically nonlinear analysis of thin structures made of functionally graded material (FGM). The proposed SHB finite elements are developed within a purely 3D framework, with displacements as [...] Read more.

In the current contribution, prismatic and hexahedral quadratic solid–shell (SHB) finite elements are proposed for the geometrically nonlinear analysis of thin structures made of functionally graded material (FGM). The proposed SHB finite elements are developed within a purely 3D framework, with displacements as the only degrees of freedom. Also, the in-plane reduced-integration technique is combined with the assumed-strain method to alleviate various locking phenomena. Furthermore, an arbitrary number of integration points are placed along a special direction, which represents the thickness. The developed elements are coupled with functionally graded behavior for the modeling of thin FGM plates. To this end, the Young modulus of the FGM plate is assumed to vary gradually in the thickness direction, according to a volume fraction distribution. The resulting formulations are implemented into the quasi-static ABAQUS/Standard finite element software in the framework of large displacements and rotations. Popular nonlinear benchmark problems are considered to assess the performance and accuracy of the proposed SHB elements. Comparisons with reference solutions from the literature demonstrate the good capabilities of the developed SHB elements for the 3D simulation of thin FGM plates. Full article

(This article belongs to the Special Issue Advances in Mechanical Problems of Functionally Graded Materials and Structures)

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10 pages, 1829 KiB

Open AccessArticle

Study on the Preparation of Plasma-Modified Fly Ash Catalyst and Its De–NO_X Mechanism

by Lei Zhang^1,*, Xin Wen¹, Lei Zhang², Xiangling Sha³, Yusu Wang¹, Jihao Chen¹, Min Luo¹ and Yonghui Li²

¹ School of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, China

² China National Heavy Machinery Research Institute Co., Ltd., Xi’an 710032, China

³ Shandong Baichuan Tongchuang Energy Co., Ltd., Jinan 250101, China

Materials 2018, 11(6), 1047; https://doi.org/10.3390/ma11061047 - 20 Jun 2018

Cited by 12 | Viewed by 3859

Abstract

Fly ash and bentonite were mixed in a certain proportion as raw materials to prepare a denitration catalyst. In previous studies, it has been concluded that fly ash-type catalysts can provide significant catalytic activity for denitrification after being modified with oxygen. In this [...] Read more.

Fly ash and bentonite were mixed in a certain proportion as raw materials to prepare a denitration catalyst. In previous studies, it has been concluded that fly ash-type catalysts can provide significant catalytic activity for denitrification after being modified with oxygen. In this study, the effect of plasma conditions on the denitration performance of the catalyst was investigated from the aspects of plasma modification power, modification time, and the flow rate of the gas. Boehm titration and infrared analysis systems were used to characterize the performance of the catalyst. The experimental results show that the optimal modification power is 60 W, the optimal modification time is 20 min, and the optimal gas flow rate is 40 mL/min. Full article

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13 pages, 10550 KiB

Open AccessArticle

Percent Reduction in Transverse Rupture Strength of Metal Matrix Diamond Segments Analysed via Discrete-Element Simulations

by Xiuyu Chen^1,2, Guoqin Huang^1,2,3,*

, Yuanqiang Tan^1,2,3, Yiqing Yu^1,2, Hua Guo^1,2,3 and Xipeng Xu^1,2,3

¹ Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021, China

² MOE Engineering Research Center for Machining of Brittle Materials, Huaqiao University, Xiamen 361021, China

³ Fujian Engineering Research Center of Intelligent Manufacturing for Brittle Materials, Fujian 361021, China

Materials 2018, 11(6), 1048; https://doi.org/10.3390/ma11061048 - 20 Jun 2018

Cited by 3 | Viewed by 3847

Abstract

The percent TRS reduction, D_TRS, which is the percent reduction of the transverse rupture strength of metal matrix diamond segments with or without diamonds, is a key metric for evaluating the bonding condition of diamonds in a matrix. In this work, [...] Read more.

The percent TRS reduction, D_TRS, which is the percent reduction of the transverse rupture strength of metal matrix diamond segments with or without diamonds, is a key metric for evaluating the bonding condition of diamonds in a matrix. In this work, we build, calibrate, and verify a discrete-element simulation of a metal matrix diamond segment to obtain D_TRS for diamond segments with various diamond-grain sizes, concentrations, and distributions. The results indicate that D_TRS increases with increasing diamond-grain concentration and decreases with increasing diamond-grain size. Both factors can be explained by the total diamond contact length, the increase of which causes the increase in D_TRS. The distribution of diamond grains in segments also strongly influences the increase of D_TRS. The use of D_TRS as a metric to assess the bonding condition of diamonds in matrixes is not valid unless the diamond-grain size, concentration, and distribution and total diamond contact length are the same for all diamond segments under consideration. Full article

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11 pages, 2964 KiB

Open AccessArticle

Microscopic View of Defect Evolution in Thermal Treated AlGaInAs Quantum Well Revealed by Spatially Resolved Cathodoluminescence

by Yue Song^1,2

, Ligong Zhang^1,*, Yugang Zeng^1,*, Li Qin¹, Yinli Zhou¹, Yongqiang Ning¹ and Lijun Wang¹

¹ State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China

² Daheng College, University of Chinese Academy of Sciences, Beijing 100049, China

Materials 2018, 11(6), 1049; https://doi.org/10.3390/ma11061049 - 20 Jun 2018

Cited by 6 | Viewed by 4581

Abstract

An aluminum gallium indium arsenic (AlGaInAs) material system is indispensable as the active layer of diode lasers emitting at 1310 or 1550 nm, which are used in optical fiber communications. However, the course of the high-temperature instability of a quantum well structure, which [...] Read more.

An aluminum gallium indium arsenic (AlGaInAs) material system is indispensable as the active layer of diode lasers emitting at 1310 or 1550 nm, which are used in optical fiber communications. However, the course of the high-temperature instability of a quantum well structure, which is closely related to the diffusion of indium atoms, is still not clear due to the system’s complexity. The diffusion process of indium atoms was simulated by thermal treatment, and the changes in the optical and structural properties of an AlGaInAs quantum well are investigated in this paper. Compressive strained Al_0.07Ga_0.22In_0.71As quantum wells were treated at 170 °C with different heat durations. A significant decrement of photoluminescence decay time was observed on the quantum well of a sample that was annealed after 4 h. The microscopic cathodoluminescent (CL) spectra of these quantum wells were measured by scanning electron microscope-cathodoluminescence (SEM-CL). The thermal treatment effect on quantum wells was characterized via CL emission peak wavelength and energy density distribution, which were obtained by spatially resolved cathodoluminescence. The defect area was clearly observed in the Al_0.07Ga_0.22In_0.71As quantum wells layer after thermal treatment. CL emissions from the defect core have higher emission energy than those from the defect-free regions. The defect core distribution, which was associated with indium segregation gradient distribution, showed asymmetric character. Full article

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Review

Jump to: Editorial, Research

14 pages, 2018 KiB

Open AccessReview

Detection of Intracellular Gold Nanoparticles: An Overview

by Mario D’Acunto

Consiglio Nazionale delle Ricerche, Istituto di Biofisica, CNR-IBF, via Moruzzi 1, 56124 Pisa, Italy

Materials 2018, 11(6), 882; https://doi.org/10.3390/ma11060882 - 24 May 2018

Cited by 27 | Viewed by 5327

Abstract

Photothermal therapy (PTT) takes advantage of unique properties of gold nanoparticles (AuNPs) (nanospheres, nanoshells (AuNSs), nanorods (AuNRs)) to destroy cancer cells or tumor tissues. This is made possible thanks principally to both to the so-called near-infrared biological transparency window, characterized by wavelengths falling [...] Read more.

Photothermal therapy (PTT) takes advantage of unique properties of gold nanoparticles (AuNPs) (nanospheres, nanoshells (AuNSs), nanorods (AuNRs)) to destroy cancer cells or tumor tissues. This is made possible thanks principally to both to the so-called near-infrared biological transparency window, characterized by wavelengths falling in the range 700–1100 nm, where light has its maximum depth of penetration in tissue, and to the efficiency of cellular uptake mechanisms of AuNPs. Consequently, the possible identification of intracellular AuNPs plays a key role for estimating the effectiveness of PTT treatments. Here, we review the recognized detection techniques of such intracellular probes with a special emphasis to the exploitation of near-infrared biological transparency window. Full article

(This article belongs to the Special Issue Photothermal Therapy of Nanomaterials)

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10 pages, 3275 KiB

Open AccessFeature PaperReview

In Situ Room Temperature Electron-Beam Driven Graphene Growth from Hydrocarbon Contamination in a Transmission Electron Microscope

by Mark H Rummeli^1,2,3,*, Yumo Pan¹, Liang Zhao¹, Jing Gao¹, Huy Q Ta¹, Ignacio G. Martinez³, Rafael G. Mendes^1,3, Thomas Gemming³

, Lei Fu⁴

, Alicja Bachmatiuk^1,2,3 and Zhongfan Liu⁵

¹ Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow Institute for Energy and Materials InnovationS, College of Physics, Optoelectronics and Energy, Soochow University, Suzhou 215006, China

² Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Sklodowskiej 34, Zabrze 41-819, Poland

³ IFW Dresden, D-01171 Dresden, Germany

⁴ College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072, China

⁵ Beijing National Laboratory for Molecular Sciences, Center for Nanochemistry, Beijing Science and Engineering Centre for Nanocarbons, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China

Materials 2018, 11(6), 896; https://doi.org/10.3390/ma11060896 - 26 May 2018

Cited by 13 | Viewed by 6420

Abstract

The excitement of graphene (as well as 2D materials in general) has generated numerous procedures for the fabrication of graphene. Here we present a mini-review on a rather less known, but attractive, in situ means to fabricate graphene inside a transmission electron microscope [...] Read more.

The excitement of graphene (as well as 2D materials in general) has generated numerous procedures for the fabrication of graphene. Here we present a mini-review on a rather less known, but attractive, in situ means to fabricate graphene inside a transmission electron microscope (TEM). This is achieved in a conventional TEM (viz. no sophisticated specimen holders or microscopes are required) and takes advantage of inherent hydrocarbon contamination as a carbon source. Both catalyst free and single atom catalyst approaches are reviewed. An advantage of this technique is that not only can the growth process be imaged in situ, but this can also be achieved with atomic resolution. Moreover, in the future, one can anticipate such approaches enabling the growth of nano-materials with atomic precision. Full article

(This article belongs to the Special Issue Carbon Nanomaterials: Graphene, Nanoribbons and Quantum dots)

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25 pages, 2583 KiB

Open AccessReview

Secondary Metabolites in the Green Synthesis of Metallic Nanoparticles

by Gregory Marslin^1,†

, Karthik Siram^2,†, Qaisar Maqbool³

, Rajendran Kamalabai Selvakesavan³, Dariusz Kruszka³, Piotr Kachlicki³

and Gregory Franklin^3,*

¹ Ratnam Institute of Pharmacy and Research, Nellore 524346, India

² Department of Pharmaceutics, PSG College of Pharmacy, Coimbatore 641004, India

³ Institute of Plant Genetics of the Polish Academy of Sciences, Poznan 60479, Poland

^† Equal contribution.

Materials 2018, 11(6), 940; https://doi.org/10.3390/ma11060940 - 3 Jun 2018

Cited by 424 | Viewed by 19340 | Correction

Abstract

The ability of organisms and organic compounds to reduce metal ions and stabilize them into nanoparticles (NPs) forms the basis of green synthesis. To date, synthesis of NPs from various metal ions using a diverse array of plant extracts has been reported. However, [...] Read more.

The ability of organisms and organic compounds to reduce metal ions and stabilize them into nanoparticles (NPs) forms the basis of green synthesis. To date, synthesis of NPs from various metal ions using a diverse array of plant extracts has been reported. However, a clear understanding of the mechanism of green synthesis of NPs is lacking. Although most studies have neglected to analyze the green-synthesized NPs (GNPs) for the presence of compounds derived from the extract, several studies have demonstrated the conjugation of sugars, secondary metabolites, and proteins in these biogenic NPs. Despite several reports on the bioactivities (antimicrobial, antioxidant, cytotoxic, catalytic, etc.) of GNPs, only a handful of studies have compared these activities with their chemically synthesized counterparts. These comparisons have demonstrated that GNPs possess better bioactivities than NPs synthesized by other methods, which might be attributed to the presence of plant-derived compounds in these NPs. The ability of NPs to bind with organic compounds to form a stable complex has huge potential in the harvesting of precious molecules and for drug discovery, if harnessed meticulously. A thorough understanding of the mechanisms of green synthesis and high-throughput screening of stabilizing/capping agents on the physico-chemical properties of GNPs is warranted to realize the full potential of green nanotechnology. Full article

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17 pages, 2532 KiB

Open AccessReview

Scanning Kelvin Probe Microscopy: Challenges and Perspectives towards Increased Application on Biomaterials and Biological Samples

by Marco Salerno¹

and Silvia Dante^2,*

¹ Materials Characterization Facility, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy

² Department of Nanoscopy & NIC, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy

Materials 2018, 11(6), 951; https://doi.org/10.3390/ma11060951 - 5 Jun 2018

Cited by 49 | Viewed by 8589

Abstract

We report and comment on the possible increase of application of scanning Kelvin probe microscopy (SKPM) for biomaterials, biological substrates, and biological samples. First, the fundamental concepts and the practical limitations of SKPM are presented, pointing out the difficulties in proper probe calibration. [...] Read more.

We report and comment on the possible increase of application of scanning Kelvin probe microscopy (SKPM) for biomaterials, biological substrates, and biological samples. First, the fundamental concepts and the practical limitations of SKPM are presented, pointing out the difficulties in proper probe calibration. Then, the most relevant literature on the use of SKPM on biological substrates and samples is briefly reviewed. We report first about biocompatible surfaces used as substrates for subsequent biological applications, such as cultures of living cells. Then, we briefly review the SKPM measurements made on proteins, DNA, and similar biomolecular systems. Finally, some considerations about the perspectives for the use of SKPM in the field of life sciences are made. This work does not pretend to provide a comprehensive view of this emerging scenario, yet we believe that it is time to put these types of application of SKPM under focus, and to face the related challenges, such as measuring in liquid and quantitative comparison with other techniques for the electrical potential readout. Full article

(This article belongs to the Special Issue State-of-the-Art Materials Science in Italy 2017)

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12 pages, 1036 KiB

Open AccessReview

The Biological Fate of Silver Nanoparticles from a Methodological Perspective

by Damjana Drobne¹

, Sara Novak¹, Iva Talaber^1,*, Iseult Lynch²

and Anita Jemec Kokalj¹

¹ Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana 1000, Slovenia

² School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK

Materials 2018, 11(6), 957; https://doi.org/10.3390/ma11060957 - 5 Jun 2018

Cited by 14 | Viewed by 4649

Abstract

We analyzed the performance and throughput of currently available analytical techniques for quantifying body burden and cell internalization/distribution of silver nanoparticles (Ag NPs). Our review of Ag NP biological fate data shows that most of the evidence gathered for Ag NPs body burden [...] Read more.

We analyzed the performance and throughput of currently available analytical techniques for quantifying body burden and cell internalization/distribution of silver nanoparticles (Ag NPs). Our review of Ag NP biological fate data shows that most of the evidence gathered for Ag NPs body burden actually points to total Ag and not only Ag NPs. On the other hand, Ag NPs were found inside the cells and tissues of some organisms, but comprehensive explanation of the mechanism(s) of NP entry and/or in situ formation is usually lacking. In many cases, the methods used to detect NPs inside the cells could not discriminate between ions and particles. There is currently no single technique that would discriminate between the metals species, and at the same time enable localization and quantification of NPs down to the cellular level. This paper serves as an orientation towards selection of the appropriate method for studying the fate of Ag NPs in line with their properties and the specific question to be addressed in the study. Guidance is given for method selection for quantification of NP uptake, biodistribution, precise tissue and cell localization, bioaccumulation, food chain transfer and modeling studies regarding the optimum combination of methods and key factors to consider. Full article

(This article belongs to the Special Issue Environmental Impact of Nanomaterials)

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34 pages, 8696 KiB

Open AccessReview

Ferromagnetic Shape Memory Heusler Materials: Synthesis, Microstructure Characterization and Magnetostructural Properties

by Riaz Ahamed Ahamed Khan^1,*, Reza Ghomashchi^1,*, Zonghan Xie^1,2 and Lei Chen¹

¹ School of Mechanical Engineering, University of Adelaide, Adelaide 5005, Australia

² School of Engineering, Edith Cowan University, Joondalup WA 6027, Australia

Materials 2018, 11(6), 988; https://doi.org/10.3390/ma11060988 - 11 Jun 2018

Cited by 27 | Viewed by 6432

Abstract

An overview of the processing, characterization and magnetostructural properties of ferromagnetic NiMnX (X = group IIIA–VA elements) Heusler alloys is presented. This type of alloy is multiferroic—exhibits more than one ferroic property—and is hence multifunctional. Examples of how different synthesis procedures influence the [...] Read more.

An overview of the processing, characterization and magnetostructural properties of ferromagnetic NiMnX (X = group IIIA–VA elements) Heusler alloys is presented. This type of alloy is multiferroic—exhibits more than one ferroic property—and is hence multifunctional. Examples of how different synthesis procedures influence the magnetostructural characteristics of these alloys are shown. Significant microstructural factors, such as the crystal structure, atomic ordering, volume of unit cell, grain size and others, which have a bearing on the properties, have been reviewed. An overriding factor is the composition which, through its tuning, affects the martensitic and magnetic transitions, the transformation temperatures, microstructures and, consequently, the magnetostructural effects. Full article

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32 pages, 7629 KiB

Open AccessReview

Development of Perovskite-Type Materials for Thermoelectric Application

by Tingjun Wu^1,2 and Peng Gao^1,2,*

¹ CAS Key Laboratory of Design and Assembly of Functional Nanostructures, and Fujian Key Laboratory of Nanomaterials, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China

² Laboratory of Advanced Functional Materials, Xiamen Institute of Rare Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen 361021, China

Materials 2018, 11(6), 999; https://doi.org/10.3390/ma11060999 - 12 Jun 2018

Cited by 149 | Viewed by 11693

Abstract

Oxide perovskite materials have a long history of being investigated for thermoelectric applications. Compared to the state-of-the-art tin and lead chalcogenides, these perovskite compounds have advantages of low toxicity, eco-friendliness, and high elemental abundance. However, because of low electrical conductivity and high thermal [...] Read more.

Oxide perovskite materials have a long history of being investigated for thermoelectric applications. Compared to the state-of-the-art tin and lead chalcogenides, these perovskite compounds have advantages of low toxicity, eco-friendliness, and high elemental abundance. However, because of low electrical conductivity and high thermal conductivity, the total thermoelectric performance of oxide perovskites is relatively poor. Variety of methods were used to enhance the TE properties of oxide perovskite materials, such as doping, inducing oxygen vacancy, embedding crystal imperfection, and so on. Recently, hybrid perovskite materials started to draw attention for thermoelectric application. Due to the low thermal conductivity and high Seebeck coefficient feature of hybrid perovskites materials, they can be promising thermoelectric materials and hold the potential for the application of wearable energy generators and cooling devices. This mini-review will build a bridge between oxide perovskites and burgeoning hybrid halide perovskites in the research of thermoelectric properties with an aim to further enhance the relevant performance of perovskite-type materials. Full article

(This article belongs to the Section Energy Materials)

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17 pages, 2924 KiB

Open AccessReview

Advancement on Lead-Free Organic-Inorganic Halide Perovskite Solar Cells: A Review

by Faruk Sani^1,*

, Suhaidi Shafie^2,3, Hong Ngee Lim^4,5

and Abubakar Ohinoyi Musa⁶

¹ Department of Physics, Usmanu Danfodiyo University, P.M.B. 2346, Sokoto, Nigeria

² Functional Devices Laboratories, Institute of Advanced Technology, Universiti Putra Malaysia, Serdang 43400, Malaysia

³ Faculty of Engineering, Universiti Putra Malaysia, Serdang 43400, Malaysia

⁴ Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang 43400, Malaysia

⁵ Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, Serdang 43400, Malaysia

⁶ Department of Physics, Bayero University, Gwarzo Road, 700241 Kano, Nigeria

Materials 2018, 11(6), 1008; https://doi.org/10.3390/ma11061008 - 14 Jun 2018

Cited by 113 | Viewed by 14128

Abstract

Remarkable attention has been committed to the recently discovered cost effective and solution processable lead-free organic-inorganic halide perovskite solar cells. Recent studies have reported that, within five years, the reported efficiency has reached 9.0%, which makes them an extremely promising and fast developing [...] Read more.

Remarkable attention has been committed to the recently discovered cost effective and solution processable lead-free organic-inorganic halide perovskite solar cells. Recent studies have reported that, within five years, the reported efficiency has reached 9.0%, which makes them an extremely promising and fast developing candidate to compete with conventional lead-based perovskite solar cells. The major challenge associated with the conventional perovskite solar cells is the toxic nature of lead (Pb) used in the active layer of perovskite material. If lead continues to be used in fabricating solar cells, negative health impacts will result in the environment due to the toxicity of lead. Alternatively, lead free perovskite solar cells could give a safe way by substituting low-cost, abundant and non toxic material. This review focuses on formability of lead-free organic-inorganic halide perovskite, alternative metal cations candidates to replace lead (Pb), and possible substitutions of organic cations, as well as halide anions in the lead-free organic-inorganic halide perovskite architecture. Furthermore, the review gives highlights on the impact of organic cations, metal cations and inorganic anions on stability and the overall performance of lead free perovskite solar cells. Full article

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22 pages, 5859 KiB

Open AccessReview

Magnetic Particle Filled Elastomeric Hybrid Composites and Their Magnetorheological Response

by Seung Hyuk Kwon¹, Jin Hyun Lee^2,*

and Hyoung Jin Choi^1,*

¹ Department of Polymer Science and Engineering, Inha University, Incheon 22212, Korea

² Polymer Technology Institute, Sungkyunkwan University, Suwon 16419, Korea

Materials 2018, 11(6), 1040; https://doi.org/10.3390/ma11061040 - 19 Jun 2018

Cited by 49 | Viewed by 8536

Abstract

The magnetorheological (MR) elastomer as a hard and soft hybrid functional material, a composite material consisting of magnetic hard particles embedded in elastomeric soft matrix, is a branch of MR materials that are functional smart materials rapidly responding to external magnetic fields. These [...] Read more.

The magnetorheological (MR) elastomer as a hard and soft hybrid functional material, a composite material consisting of magnetic hard particles embedded in elastomeric soft matrix, is a branch of MR materials that are functional smart materials rapidly responding to external magnetic fields. These tunable properties of MR elastomers facilitate a variety of applications. In this brief review paper, in addition to general information on the MR elastomers, recent research not only on a wide variety of MR elastomeric systems focusing on various magnetic particles, elastomeric matrices, additives and particle modification methods, but also on their characteristics including MR properties from dynamic oscillation tests is covered along with their mechanical properties such as the Payne effect, tensile strength and engineering applications. Full article

(This article belongs to the Special Issue Hard and Soft Hybrid Functional Materials)

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