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Materials, Volume 11, Issue 4 (April 2018)

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Cover Story (view full-size image) The combination of the characteristic luminescence properties of lanthanide ions with the [...] Read more.
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Open AccessArticle Electric and Hydraulic Properties of Carbon Felt Immersed in Different Dielectric Liquids
Materials 2018, 11(4), 650; https://doi.org/10.3390/ma11040650
Received: 21 February 2018 / Revised: 12 April 2018 / Accepted: 20 April 2018 / Published: 23 April 2018
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Abstract
Electroconductive carbon felt (CF) material, having a permeable structure and significant electroconductive surface, is widely used for electrodes in numerous electrochemical applications such as redox flow batteries, fuel cells, electrochemical desalination apparatus, etc. The internal structure of CF is composed of different lengths
[...] Read more.
Electroconductive carbon felt (CF) material, having a permeable structure and significant electroconductive surface, is widely used for electrodes in numerous electrochemical applications such as redox flow batteries, fuel cells, electrochemical desalination apparatus, etc. The internal structure of CF is composed of different lengths of carbon filaments bonded together. This structure creates a large number of stochastically oriented and stochastically linked channels that have different lengths and cross sections. Therefore, the CF hydraulic permeability is similar to that of porous media and is determined by the internal empty volume and arrangement of carbon fibers. Its electroconductivity is ensured by the conductivity of the carbon filaments and by the electrical interconnections between fibers. Both of these properties (permeability and electrical conductivity) are extremely important for the efficient functioning of electrochemical devices. However, their influences counter each other during CF compressing. Increasing the stress on a felt element provides supplementary electrical contacts of carbon filaments, which lead to improved electrical conductivity. Thus, the active surface of the felt electrode is increased, which also boosts redox chemical reactions. On the other hand, compressed felt possesses reduced hydrodynamic permeability as a result of a diminished free volume of porous media and intrinsic channels. This causes increasing hydrodynamic expenditures of electrolyte pumping through electrodes and lessened cell (battery) efficiency. The designer of specific electrochemical systems has to take into account both of these properties when selecting the optimal construction for a cell. This article presents the results of measurements and novel approximating expressions of electrical and hydraulic characteristics of a CF during its compression. Since electrical conductivity plays a determining role in providing electrochemical reactions, it was measured in dry conditions and when the CF was immersed in several non-conductive liquids. The choice of such liquids prevented side effects of electrolyte ionic conductivity impact on electrical resistivity of the CF. This gave an opportunity to determine the influences of dielectric parameters of electrolytes to increase or decrease the density of interconnectivity of carbon fibers either between themselves or between them and electrodes. The experiments showed the influence of liquid permittivity on the conductivity of CF, probably by changing the density of fiber interconnections inside the felt. Full article
(This article belongs to the Section Carbon Materials)
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Open AccessFeature PaperArticle On the Phase Separation in n-Type Thermoelectric Half-Heusler Materials
Materials 2018, 11(4), 649; https://doi.org/10.3390/ma11040649
Received: 29 March 2018 / Revised: 18 April 2018 / Accepted: 19 April 2018 / Published: 23 April 2018
Cited by 3 | Viewed by 1295 | PDF Full-text (3425 KB) | HTML Full-text | XML Full-text
Abstract
Half-Heusler compounds have been in focus as potential materials for thermoelectric energy conversion in the mid-temperature range, e.g., as in automotive or industrial waste heat recovery, for more than ten years now. Because of their mechanical and thermal stability, these compounds are advantageous
[...] Read more.
Half-Heusler compounds have been in focus as potential materials for thermoelectric energy conversion in the mid-temperature range, e.g., as in automotive or industrial waste heat recovery, for more than ten years now. Because of their mechanical and thermal stability, these compounds are advantageous for common thermoelectric materials such as Bi 2 Te 3 , SiGe, clathrates or filled skutterudites. A further advantage lies in the tunability of Heusler compounds, allowing one to avoid expensive and toxic elements. Half-Heusler compounds usually exhibit a high electrical conductivity σ , resulting in high power factors. The main drawback of half-Heusler compounds is their high lattice thermal conductivity. Here, we present a detailed study of the phase separation in an n-type Heusler materials system, showing that the Ti x Zr y Hf z NiSn system is not a solid solution. We also show that this phase separation is key to the thermoelectric high efficiency of n-type Heusler materials. These results strongly underline the importance of phase separation as a powerful tool for designing highly efficient materials for thermoelectric applications that fulfill the industrial demands of a thermoelectric converter. Full article
(This article belongs to the Special Issue Half-Heusler, Silicide and Zintl-type Thermoelectric Materials)
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Open AccessArticle Microstructure and Solidification Crack Susceptibility of Al 6014 Molten Alloy Subjected to a Spatially Oscillated Laser Beam
Materials 2018, 11(4), 648; https://doi.org/10.3390/ma11040648
Received: 29 March 2018 / Revised: 19 April 2018 / Accepted: 19 April 2018 / Published: 23 April 2018
Cited by 1 | Viewed by 1205 | PDF Full-text (6629 KB) | HTML Full-text | XML Full-text
Abstract
Oscillating laser beam welding for Al 6014 alloy was performed using a single mode fiber laser and two-axis scanner system. Its effect on the microstructural evolution of the fusion zone was investigated. To evaluate the influence of oscillation parameters, self-restraint test specimens were
[...] Read more.
Oscillating laser beam welding for Al 6014 alloy was performed using a single mode fiber laser and two-axis scanner system. Its effect on the microstructural evolution of the fusion zone was investigated. To evaluate the influence of oscillation parameters, self-restraint test specimens were fabricated with different beam patterns, widths, and frequencies. The behavior of hot cracking propagation was analyzed by high-speed camera and electron backscatter diffraction. The behavior of crack propagation was observed to be highly correlated with the microstructural evolution of the fusion zone. For most oscillation conditions, the microstructure resembled that of linear welds. A columnar structure was formed near the fusion line and an equiaxed structure was generated at its center. The wide equiaxed zone of oscillation welding increased solidification crack susceptibility. For an oscillation with an infinite-shaped scanning pattern at 100 Hz and 3.5 m/min welding speed, the bead width, solidification microstructure, and the width of the equiaxed zone at the center of fusion fluctuated. Furthermore, the equiaxed and columnar regions alternated periodically, which could reduce solidification cracking susceptibility. Full article
(This article belongs to the Special Issue Laser Materials Processing)
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Open AccessArticle Effect of Reaction Temperature on Structure, Appearance and Bonding Type of Functionalized Graphene Oxide Modified P-Phenylene Diamine
Materials 2018, 11(4), 647; https://doi.org/10.3390/ma11040647
Received: 23 March 2018 / Revised: 14 April 2018 / Accepted: 19 April 2018 / Published: 23 April 2018
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Abstract
In this study, graphene oxides with different functionalization degrees were prepared by a facile one-step hydrothermal reflux method at various reaction temperatures using graphene oxide (GO) as starting material and p-phenylenediamine (PPD) as the modifier. The effects of reaction temperature on structure,
[...] Read more.
In this study, graphene oxides with different functionalization degrees were prepared by a facile one-step hydrothermal reflux method at various reaction temperatures using graphene oxide (GO) as starting material and p-phenylenediamine (PPD) as the modifier. The effects of reaction temperature on structure, appearance and bonding type of the obtained materials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results showed that when the reaction temperature was 10–70 °C, the GO reacted with PPD through non-covalent ionic bonds (–COOH3+N–R) and hydrogen bonds (C–OH…H2N–X). When the reaction temperature reached 90 °C, the GO was functionalized with PPD through covalent bonds of C–N. The crystal structure of products became more ordered and regular, and the interlayer spacing (d value) and surface roughness increased as the temperature increased. Furthermore, the results suggested that PPD was grafted on the surface of GO through covalent bonding by first attacking the carboxyl groups and then the epoxy groups of GO. Full article
(This article belongs to the Special Issue Element-Doped Functional Carbon-based Materials)
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Open AccessArticle New Insights into Sensitization Mechanism of the Doped Ce (IV) into Strontium Titanate
Materials 2018, 11(4), 646; https://doi.org/10.3390/ma11040646
Received: 17 March 2018 / Revised: 17 April 2018 / Accepted: 18 April 2018 / Published: 23 April 2018
Cited by 2 | Viewed by 994 | PDF Full-text (4978 KB) | HTML Full-text | XML Full-text
Abstract
SrTiO3 and Ce4+ doped SrTiO3 were synthesized by a modified sol–gel process. The optimization synthesis parameters were obtained by a series of single factor experiments. Interesting phenomena are observable in Ce4+ doped SrTiO3 systems. Sr2+ in SrTiO
[...] Read more.
SrTiO3 and Ce4+ doped SrTiO3 were synthesized by a modified sol–gel process. The optimization synthesis parameters were obtained by a series of single factor experiments. Interesting phenomena are observable in Ce4+ doped SrTiO3 systems. Sr2+ in SrTiO3 system was replaced by Ce4+, which reduced the surface segregation of Ti4+, ameliorated agglomeration, increased specific surface area more than four times compared with pure SrTiO3, and enhanced quantum efficiency for SrTiO3. Results showed that Ce4+ doping increased the physical adsorption of H2O and adsorbed oxygen on the surface of SrTiO3, which produced additional catalytic active centers. Electrons on the 4f energy level for Ce4+ produced new energy states in the band gap of SrTiO3, which not only realized the use of visible light but also led to an easier separation between the photogenerated electrons and holes. Ce4+ repeatedly captured photoelectrons to produce Ce3+, which inhibited the recombination between photogenerated electrons and holes as well as prolonged their lifetime; it also enhanced quantum efficiency for SrTiO3. The methylene blue (MB) degradation efficiency reached 98.7% using 3 mol % Ce4+ doped SrTiO3 as a photocatalyst, indicating highly photocatalytic activity. Full article
(This article belongs to the Special Issue Photocatalysis for Wastewater Treatment)
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Open AccessArticle Microstructure and Tensile Properties of Friction Stir Processed Mg–Sn–Zn Alloy
Materials 2018, 11(4), 645; https://doi.org/10.3390/ma11040645
Received: 21 March 2018 / Revised: 18 April 2018 / Accepted: 19 April 2018 / Published: 23 April 2018
Cited by 2 | Viewed by 976 | PDF Full-text (6895 KB) | HTML Full-text | XML Full-text
Abstract
In this study, as-cast Mg–6Sn–2Zn (wt.%) alloy was subjected to friction stir processing (FSP) and the microstructure and tensile properties of FSP Mg–6Sn–2Zn samples were investigated. It was found that, in the stir zone (SZ) of FSP Mg–6Sn–2Zn samples, α-Mg grains were significantly
[...] Read more.
In this study, as-cast Mg–6Sn–2Zn (wt.%) alloy was subjected to friction stir processing (FSP) and the microstructure and tensile properties of FSP Mg–6Sn–2Zn samples were investigated. It was found that, in the stir zone (SZ) of FSP Mg–6Sn–2Zn samples, α-Mg grains were significantly refined via dynamic recrystallization (DRX) and the Mg2Sn phase was broken and partially dissolved. The microstructure in SZ was nonuniform and DRXed grains in the SZ-up regions were coarser than those in the SZ-down regions. Coarse broken Mg2Sn particles were observed in the SZ-up regions, while only fine Mg2Sn particles were observed in the SZ-down regions. Strong {0001} basal texture developed in the SZ regions of Mg–6Sn–2Zn samples after FSP. The increase of travel speed had little effect on the texture of different SZ regions. The ductility of FSP Mg–6Sn–2Zn samples was obviously improved, while the improvement in strength was negligible when compared to the as-cast sample. The tensile properties of FSP Mg–6Sn–2Zn samples were influenced by grain refinement, texture modification, and the breaking up and dissolution of the Mg2Sn phase. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Generation Mechanism of Nonlinear Rayleigh Surface Waves for Randomly Distributed Surface Micro-Cracks
Materials 2018, 11(4), 644; https://doi.org/10.3390/ma11040644
Received: 11 April 2018 / Revised: 19 April 2018 / Accepted: 19 April 2018 / Published: 23 April 2018
Cited by 2 | Viewed by 874 | PDF Full-text (3980 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates the propagation of Rayleigh surface waves in structures with randomly distributed surface micro-cracks using numerical simulations. The results revealed a significant ultrasonic nonlinear effect caused by the surface micro-cracks, which is mainly represented by a second harmonic with even more
[...] Read more.
This paper investigates the propagation of Rayleigh surface waves in structures with randomly distributed surface micro-cracks using numerical simulations. The results revealed a significant ultrasonic nonlinear effect caused by the surface micro-cracks, which is mainly represented by a second harmonic with even more distinct third/quadruple harmonics. Based on statistical analysis from the numerous results of random micro-crack models, it is clearly found that the acoustic nonlinear parameter increases linearly with micro-crack density, the proportion of surface cracks, the size of micro-crack zone, and the excitation frequency. This study theoretically reveals that nonlinear Rayleigh surface waves are feasible for use in quantitatively identifying the physical characteristics of surface micro-cracks in structures. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Effect of Resin Type on the Tribological Properties of a Three-Dimensional Self-Lubricating Composite Surface
Materials 2018, 11(4), 643; https://doi.org/10.3390/ma11040643
Received: 7 March 2018 / Revised: 14 April 2018 / Accepted: 18 April 2018 / Published: 22 April 2018
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Abstract
In this paper, three kinds of polymer, of epoxy resin (EP), phenolic resin (PF), and unsaturated polyester (UP), were used as fillers to prepare the laminated composite surface, and the tribological properties of a composite surface were studied under dry sliding condition. The
[...] Read more.
In this paper, three kinds of polymer, of epoxy resin (EP), phenolic resin (PF), and unsaturated polyester (UP), were used as fillers to prepare the laminated composite surface, and the tribological properties of a composite surface were studied under dry sliding condition. The results showed that: (i) the composites surface without MoS2 exhibited high friction coefficient and high wear rate at 25 °C, while the friction coefficients were reduced when the temperature increases to 100 °C; (ii) with the addition of MoS2, the friction coefficient of the epoxy resin composite containing MoS2 (E1) was below 0.22 under a temperature of 25–150 °C, and the friction coefficient was increased to 0.32 as temperature increased to 150 °C, while the average friction coefficient of the unsaturated polyester composite containing MoS2 (U1) was very low and below 0.20 under a temperature of 25–150 °C. Analysis of the wear scars indicated that, for the MoS2-containing composite, the transfer films of the E1 and U1 were smooth and continuous under low temperature, while the transfer film of U1 was comparatively complete than that of E1 under 150 °C. The composites with solid lubrication had excellent high-temperature self-lubricating properties, which was attributed to the synergistic effect of the laminated structure, and the thermal expansion of the polymer, and finally a transfer film was formed on the sliding path. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Synergistic Effect of Nitrogen Doping and MWCNT Intercalation for the Graphene Hybrid Support for Pt Nanoparticles with Exemplary Oxygen Reduction Reaction Performance
Materials 2018, 11(4), 642; https://doi.org/10.3390/ma11040642
Received: 30 March 2018 / Revised: 18 April 2018 / Accepted: 20 April 2018 / Published: 22 April 2018
Cited by 2 | Viewed by 1154 | PDF Full-text (3848 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The potential of graphene–multi-walled-carbon nanotube (G-M) hybrids prepared by the one-pot modified Hummers method followed by thermal annealing has been demonstrated by employing one as an electrocatalyst support for oxygen reduction reaction (ORR). N doping effectively modified the electronic structure of the G-M
[...] Read more.
The potential of graphene–multi-walled-carbon nanotube (G-M) hybrids prepared by the one-pot modified Hummers method followed by thermal annealing has been demonstrated by employing one as an electrocatalyst support for oxygen reduction reaction (ORR). N doping effectively modified the electronic structure of the G-M hybrid support, which was beneficial for the uniform distribution of Pt nanoparticles, and ORR activities were further improved. The newly prepared Pt/N-G-M catalyst demonstrated higher electrochemical activity than Pt/G-M and Pt/G catalysts. Even compared with commercial 20 wt % Pt/C (JM20), Pt/N-G-M delivered a better half-wave potential and mass activity. In terms of the durability test, Pt/N-G-M maintained 72.7% of its initial electrochemical active surface area (ECSA) after 2000 repeated potential cycles between 0 and 1.2 V in acidic media in relation to the 44.4% retention for JM20. Moreover, the half-wave potential for Pt/N-G-M showed only a minimal change, significantly superior to the 139 mV of loss for JM20. It is expected that Pt/N-G-M can be the potential candidate as a highly efficient and durable catalyst if utilized in proton exchange membrane fuel cells (PEMFCs). Full article
(This article belongs to the Section Catalytic Materials)
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Open AccessArticle Ultralight Graphene/Carbon Nanotubes Aerogels with Compressibility and Oil Absorption Properties
Materials 2018, 11(4), 641; https://doi.org/10.3390/ma11040641
Received: 8 April 2018 / Revised: 19 April 2018 / Accepted: 20 April 2018 / Published: 22 April 2018
Cited by 1 | Viewed by 1403 | PDF Full-text (21159 KB) | HTML Full-text | XML Full-text
Abstract
Graphene aerogels have many advantages, such as low density, high elasticity and strong adsorption. They are considered to be widely applicable in many fields. At present, the most valuable research area aims to find a convenient and effective way to prepare graphene aerogels
[...] Read more.
Graphene aerogels have many advantages, such as low density, high elasticity and strong adsorption. They are considered to be widely applicable in many fields. At present, the most valuable research area aims to find a convenient and effective way to prepare graphene aerogels with excellent properties. In this work graphene/carbon nanotube aerogels are prepared through hydrothermal reduction, freeze-drying and high temperature heat treatment with the blending of graphene oxide and carbon nanotubes. A new reducing agent-ascorbic acid is selected to explore the best preparation process. The prepared aerogels have compression and resilience and oil absorption properties due to the addition of carbon nanotubes as designed. Full article
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Open AccessArticle Polyvinyl Alcohol Microspheres Reinforced Thermoplastic Starch Composites
Materials 2018, 11(4), 640; https://doi.org/10.3390/ma11040640
Received: 18 March 2018 / Revised: 18 April 2018 / Accepted: 19 April 2018 / Published: 21 April 2018
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Abstract
We reported a new method to prepare polyvinyl alcohol (PVA)/thermoplastic starch (TPS) composites by using polyvinyl alcohol microspheres (PVAMS). The PVAMS/TPS composites were characterized using tensile test, scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The results exhibited
[...] Read more.
We reported a new method to prepare polyvinyl alcohol (PVA)/thermoplastic starch (TPS) composites by using polyvinyl alcohol microspheres (PVAMS). The PVAMS/TPS composites were characterized using tensile test, scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The results exhibited that adding small amounts of PVAMSs can effectively improve the mechanical strength and toughness of the composites, especially for the 1 wt %PVAMS in TPS matrix, with a tensile strength of 3.5 MPa, an elongation at break at 71.73% and an impact strength of 33.4 kJ/m2. Furthermore, the SEM and shift in the tan δ peak (Tα and Tβ) at the maximum value of 69.87 and −36.52 °C indicates that the PVAMS decreased the mobility of the amorphous starch molecules due to the strong intermolecular hydrogen bonds between PVAMS and TPS. The peak temperature of maximum decomposition rate (Tp) of 1 wt % PVAMS/TPS composites increased about 5 °C compared with TPS in TGA curves. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Efficiency Improvement Using Molybdenum Disulphide Interlayers in Single-Wall Carbon Nanotube/Silicon Solar Cells
Materials 2018, 11(4), 639; https://doi.org/10.3390/ma11040639
Received: 27 March 2018 / Revised: 12 April 2018 / Accepted: 12 April 2018 / Published: 21 April 2018
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Abstract
Molybdenum disulphide (MoS2) is one of the most studied and widely applied nanomaterials from the layered transition-metal dichalcogenides (TMDs) semiconductor family. MoS2 has a large carrier diffusion length and a high carrier mobility. Combining a layered structure of single-wall carbon
[...] Read more.
Molybdenum disulphide (MoS2) is one of the most studied and widely applied nanomaterials from the layered transition-metal dichalcogenides (TMDs) semiconductor family. MoS2 has a large carrier diffusion length and a high carrier mobility. Combining a layered structure of single-wall carbon nanotube (SWCNT) and MoS2 with n-type silicon (n-Si) provided novel SWCNT/n-Si photovoltaic devices. The solar cell has a layered structure with Si covered first by a thin layer of MoS2 flakes and then a SWCNT film. The films were examined using scanning electron microscopy, atomic force microscopy and Raman spectroscopy. The MoS2 flake thickness ranged from 5 to 90 nm while the nanosheet’s lateral dimensions size ranged up to 1 μm2. This insertion of MoS2 improved the photoconversion efficiency (PCE) of the SWCNT/n-Si solar cells by approximately a factor of 2. Full article
(This article belongs to the Special Issue Graphene/Carbon Nanotubes Application in Solar Cells)
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Open AccessArticle Piezoelectric Response of Multi-Walled Carbon Nanotubes
Materials 2018, 11(4), 638; https://doi.org/10.3390/ma11040638
Received: 30 March 2018 / Revised: 17 April 2018 / Accepted: 17 April 2018 / Published: 21 April 2018
Cited by 2 | Viewed by 1263 | PDF Full-text (2000 KB) | HTML Full-text | XML Full-text
Abstract
Recent studies in nanopiezotronics have indicated that strained graphene may exhibit abnormal flexoelectric and piezoelectric properties. Similar assumptions have been made with regard to the properties of carbon nanotubes (CNTs), however, this has not so far been confirmed. This paper presents the results
[...] Read more.
Recent studies in nanopiezotronics have indicated that strained graphene may exhibit abnormal flexoelectric and piezoelectric properties. Similar assumptions have been made with regard to the properties of carbon nanotubes (CNTs), however, this has not so far been confirmed. This paper presents the results of our experimental studies confirming the occurrence of a surface piezoelectric effect in multi-walled CNTs under a non-uniform strain. Using atomic force microscopy, we demonstrated the piezoelectric response of multi-walled CNTs under compression and bending. The current generated by deforming an individual CNT was shown to be −24 nA. The value of the surface potential at the top of the bundle of strained CNTs varied from 268 mV to −110 mV, depending on strain type and magnitude. We showed that the maximum values of the current and the surface potential can be achieved when longitudinal strain predominates in a CNT. However, increasing the bending strain of CNTs does not lead to a significant increase in current and surface potential, due to the mutual compensation of piezoelectric charges concentrated on the CNT side walls. The results of the study offer a number of opportunities and challenges for further fundamental research on the piezoelectric properties of carbon nanotubes as well as for the development of advanced CNT-based nanopiezotronic devices. Full article
(This article belongs to the Special Issue Carbon Nanotubes 2018)
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Open AccessArticle Microstructure Images Restoration of Metallic Materials Based upon KSVD and Smoothing Penalty Sparse Representation Approach
Materials 2018, 11(4), 637; https://doi.org/10.3390/ma11040637
Received: 27 March 2018 / Revised: 11 April 2018 / Accepted: 17 April 2018 / Published: 20 April 2018
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Abstract
Microstructure images of metallic materials play a significant role in industrial applications. To address image degradation problem of metallic materials, a novel image restoration technique based on K-means singular value decomposition (KSVD) and smoothing penalty sparse representation (SPSR) algorithm is proposed in this
[...] Read more.
Microstructure images of metallic materials play a significant role in industrial applications. To address image degradation problem of metallic materials, a novel image restoration technique based on K-means singular value decomposition (KSVD) and smoothing penalty sparse representation (SPSR) algorithm is proposed in this work, the microstructure images of aluminum alloy 7075 (AA7075) material are used as examples. To begin with, to reflect the detail structure characteristics of the damaged image, the KSVD dictionary is introduced to substitute the traditional sparse transform basis (TSTB) for sparse representation. Then, due to the image restoration, modeling belongs to a highly underdetermined equation, and traditional sparse reconstruction methods may cause instability and obvious artifacts in the reconstructed images, especially reconstructed image with many smooth regions and the noise level is strong, thus the SPSR (here, q = 0.5) algorithm is designed to reconstruct the damaged image. The results of simulation and two practical cases demonstrate that the proposed method has superior performance compared with some state-of-the-art methods in terms of restoration performance factors and visual quality. Meanwhile, the grain size parameters and grain boundaries of microstructure image are discussed before and after they are restored by proposed method. Full article
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Open AccessArticle Intermetallic Growth and Interfacial Properties of the Grain Refiners in Al Alloys
Materials 2018, 11(4), 636; https://doi.org/10.3390/ma11040636
Received: 13 February 2018 / Revised: 15 April 2018 / Accepted: 17 April 2018 / Published: 20 April 2018
Cited by 2 | Viewed by 751 | PDF Full-text (4593 KB) | HTML Full-text | XML Full-text
Abstract
Al3TM(TM = Ti, Zr, Hf, Sc) particles acting as effective grain refiners for Al alloys have been receiving extensive attention these days. In order to judge their nucleation behaviors, first-principles calculations are used to investigate their intermetallic and interfacial properties. Based
[...] Read more.
Al3TM(TM = Ti, Zr, Hf, Sc) particles acting as effective grain refiners for Al alloys have been receiving extensive attention these days. In order to judge their nucleation behaviors, first-principles calculations are used to investigate their intermetallic and interfacial properties. Based on energy analysis, Al3Zr and Al3Sc are more suitable for use as grain refiners than the other two intermetallic compounds. Interfacial properties show that Al/Al3TM(TM = Ti, Zr, Hf, Sc) interfaces in I-ter interfacial mode exhibit better interface wetting effects due to larger Griffith rupture work and a smaller interface energy. Among these, Al/Al3Sc achieves the lowest interfacial energy, which shows that Sc atoms should get priority for occupying interfacial sites. Additionally, Sc-doped Al/Al3(Zr, Sc) interfacial properties show that Sc can effectively improve the Al/Al3(Zr, Sc) binding strength with the Al matrix. By combining the characteristics of interfaces with the properties of intermetallics, the core-shell structure with Al3Zr-core or Al3Zr(Sc1-1)-core encircled with an Sc-rich shell forms. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Optimization of the Critical Parameters of the Spherical Agglomeration Crystallization Method by the Application of the Quality by Design Approach
Materials 2018, 11(4), 635; https://doi.org/10.3390/ma11040635
Received: 26 March 2018 / Revised: 12 April 2018 / Accepted: 18 April 2018 / Published: 20 April 2018
Cited by 1 | Viewed by 956 | PDF Full-text (2663 KB) | HTML Full-text | XML Full-text
Abstract
This research work presents the use of the Quality by Design (QbD) concept for optimization of the spherical agglomeration crystallization method in the case of the active agent, ambroxol hydrochloride (AMB HCl). AMB HCl spherical crystals were formulated by the spherical agglomeration method,
[...] Read more.
This research work presents the use of the Quality by Design (QbD) concept for optimization of the spherical agglomeration crystallization method in the case of the active agent, ambroxol hydrochloride (AMB HCl). AMB HCl spherical crystals were formulated by the spherical agglomeration method, which was applied as an antisolvent technique. Spherical crystals have good flowing properties, which makes the direct compression tableting method applicable. This means that the amount of additives used can be reduced and smaller tablets can be formed. For the risk assessment, LeanQbD Software was used. According to its results, four independent variables (mixing type and time, dT (temperature difference between solvent and antisolvent), and composition (solvent/antisolvent volume ratio)) and three dependent variables (mean particle size, aspect ratio, and roundness) were selected. Based on these, a 2–3 mixed-level factorial design was constructed, crystallization was accomplished, and the results were evaluated using Statistica for Windows 13 program. Product assay was performed and it was revealed that improvements in the mean particle size (from ~13 to ~200 µm), roundness (from ~2.4 to ~1.5), aspect ratio (from ~1.7 to ~1.4), and flow properties were observed while polymorphic transitions were avoided. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Mapping the Galvanic Corrosion of Three Coupled Metal Alloys Using Coupled Multielectrode Array: Influence of Chloride Ion Concentration
Materials 2018, 11(4), 634; https://doi.org/10.3390/ma11040634
Received: 22 March 2018 / Revised: 12 April 2018 / Accepted: 12 April 2018 / Published: 20 April 2018
Cited by 1 | Viewed by 933 | PDF Full-text (11060 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The galvanic corrosion behavior of three metal alloys commonly used in water desalination plants was investigated using coupled multielectrode arrays consisting of aluminum-brass (HAl77-2), titanium alloy (TA2), and 316L stainless steel (316L SS). The three electrode types were coupled galvanically and arranged in
[...] Read more.
The galvanic corrosion behavior of three metal alloys commonly used in water desalination plants was investigated using coupled multielectrode arrays consisting of aluminum-brass (HAl77-2), titanium alloy (TA2), and 316L stainless steel (316L SS). The three electrode types were coupled galvanically and arranged in different geometric configurations. Their corrosion behavior was characterized as a function of the chloride concentration. The potential and current distributions of the three-electrode coupling systems display electrochemical inhomogeneity. Generally, the aluminum-brass wires are anodic versus the titanium alloy and stainless steel. The titanium alloy acts as a primary cathode, and the 316L SS acts as a secondary cathode. The corrosion rate of aluminum-brass depends on the concentration of chloride ion, with a maximum corrosion rate at a chloride concentration of 2.3 wt %. In terms of geometrical arrangements, when the anodic HAl77-2 wires are located on the edge and are connected to the 316L SS wires in the coupling system, the main anodic area enlarges, especially in the area adjacent to the 316L SS wires. When the HAl77-2 wires are located between (in the middle of) the two other types of wires, the corrosion rates are higher than the corrosion rates observed from the other two geometrical arrangements. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Experimental Investigation on the Residual Stresses in a Thick Joint with a Partial Repair Weld Using Multiple-Cut Contour Method
Materials 2018, 11(4), 633; https://doi.org/10.3390/ma11040633
Received: 7 April 2018 / Revised: 18 April 2018 / Accepted: 19 April 2018 / Published: 20 April 2018
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Abstract
The stress distributions in a thick welded specimen with a partial repair weld were measured with the three-cut contour method. The longitudinal stress maps in the original weld and the repair weld were obtained and the transverse stress map at the weld centerline
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The stress distributions in a thick welded specimen with a partial repair weld were measured with the three-cut contour method. The longitudinal stress maps in the original weld and the repair weld were obtained and the transverse stress map at the weld centerline in the original weld was acquired. The difference between the longitudinal stress in the partial repair weld and that in the original weld was investigated. Results show that the longitudinal stress increases significantly within the entire repair region with a peak tensile longitudinal stress close to the yield strength of weld material; and the longitudinal stress in the region above the repair weld decreases distinctly after repair; the introduction of the partial repair weld does not affect the stress distribution trend in the original weld (whether it is beyond or above the repair weld), and it has a slight effect on the tensile stress distribution width in the repair region. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Investigation of Laser Welding of Ti Alloys for Cognitive Process Parameters Selection
Materials 2018, 11(4), 632; https://doi.org/10.3390/ma11040632
Received: 23 March 2018 / Revised: 13 April 2018 / Accepted: 17 April 2018 / Published: 20 April 2018
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Abstract
Laser welding of titanium alloys is attracting increasing interest as an alternative to traditional joining techniques for industrial applications, with particular reference to the aerospace sector, where welded assemblies allow for the reduction of the buy-to-fly ratio, compared to other traditional mechanical joining
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Laser welding of titanium alloys is attracting increasing interest as an alternative to traditional joining techniques for industrial applications, with particular reference to the aerospace sector, where welded assemblies allow for the reduction of the buy-to-fly ratio, compared to other traditional mechanical joining techniques. In this research work, an investigation on laser welding of Ti–6Al–4V alloy plates is carried out through an experimental testing campaign, under different process conditions, in order to perform a characterization of the produced weld bead geometry, with the final aim of developing a cognitive methodology able to support decision-making about the selection of the suitable laser welding process parameters. The methodology is based on the employment of artificial neural networks able to identify correlations between the laser welding process parameters, with particular reference to the laser power, welding speed and defocusing distance, and the weld bead geometric features, on the basis of the collected experimental data. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Morphological Evolution of Vertically Standing Molybdenum Disulfide Nanosheets by Chemical Vapor Deposition
Materials 2018, 11(4), 631; https://doi.org/10.3390/ma11040631
Received: 6 March 2018 / Revised: 9 April 2018 / Accepted: 17 April 2018 / Published: 20 April 2018
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Abstract
In this study, we demonstrated the chemical vapor deposition (CVD) of vertically standing molybdenum disulfide (MoS2) nanosheets, with an unconventional combination of molybdenum hexacarbonyl (Mo(CO)6) and 1,2-ethanedithiol (C2H6S2) as the novel kind of
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In this study, we demonstrated the chemical vapor deposition (CVD) of vertically standing molybdenum disulfide (MoS2) nanosheets, with an unconventional combination of molybdenum hexacarbonyl (Mo(CO)6) and 1,2-ethanedithiol (C2H6S2) as the novel kind of Mo and S precursors respectively. The effect of the distance between the precursor’s outlet and substrates (denoted as d) on the growth characteristics of MoS2, including surface morphology and nanosheet structure, was investigated. Meanwhile, the relationship between the structure characteristics of MoS2 nanosheets and their catalytic performance for hydrogen evolution reaction (HER) was elucidated. The formation of vertically standing nanosheets was analyzed and verified by means of an extrusion growth model. The crystallinity, average length, and average depth between peak and valley (Rz) of MoS2 nanosheets differed depending on the spatial location of the substrate. Good crystalized MoS2 nanosheets grown at d = 5.5 cm with the largest average length of 440 nm, and the highest Rz of 162 nm contributed to a better HER performance, with a respective Tafel slope and exchange current density of 138.9 mV/decade, and 22.6 μA/cm2 for raw data (127.8 mV/decade and 19.3 μA/cm2 for iR-corrected data). Full article
(This article belongs to the Special Issue Recent Advances in 2D Nanomaterials)
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Open AccessArticle Microfluidic Synthesis of Ca-Alginate Microcapsules for Self-Healing of Bituminous Binder
Materials 2018, 11(4), 630; https://doi.org/10.3390/ma11040630
Received: 11 April 2018 / Revised: 16 April 2018 / Accepted: 17 April 2018 / Published: 19 April 2018
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Abstract
This work aims to develop an original alginate micro-emulsion combining with droplets microfluidic method to produce multinuclear Ca-alginate microcapsules containing rejuvenator for the self-healing of bituminous binder. The sizes of the Ca-alginate microcapsules could be easily controlled by tuning flow rates of the
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This work aims to develop an original alginate micro-emulsion combining with droplets microfluidic method to produce multinuclear Ca-alginate microcapsules containing rejuvenator for the self-healing of bituminous binder. The sizes of the Ca-alginate microcapsules could be easily controlled by tuning flow rates of the continuous and dispersed phases. The addition of a surfactant Tween80 not only improved the stability of the emulsion, but it also effectively reduced the size of the microcapsules. Size predictive mathematical model of the microcapsules was proposed through the analysis of fluid force. Optical microscope and remote Fourier infrared test confirmed the multinuclear structure of Ca-alginate microcapsules. Thermogravimetric analysis showed that the microcapsules coated with nearly 40% rejuvenator and they remained intact during the preparation of bitumen specimen at 135 °C. Micro self-healing process of bituminous binder with multinuclear Ca-alginate microcapsules containing rejuvenator was monitored and showed enhanced self-healing performance. Tensile stress-recovery test revealed that the recovery rate increased by 32.08% (in the case of 5% microcapsules), which meant that the Ca-alginate microcapsules containing rejuvenator could effectively enhance the self-healing property of bituminous binder. Full article
(This article belongs to the Special Issue Environment-Friendly Construction Materials)
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Open AccessArticle Directed Thermal Diffusions through Metamaterial Source Illusion with Homogeneous Natural Media
Materials 2018, 11(4), 629; https://doi.org/10.3390/ma11040629
Received: 3 March 2018 / Revised: 26 March 2018 / Accepted: 18 April 2018 / Published: 19 April 2018
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Abstract
Owing to the utilization of transformation optics, many significant research and development achievements have expanded the applications of illusion devices into thermal fields. However, most of the current studies on relevant thermal illusions used to reshape the thermal fields are dependent of certain
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Owing to the utilization of transformation optics, many significant research and development achievements have expanded the applications of illusion devices into thermal fields. However, most of the current studies on relevant thermal illusions used to reshape the thermal fields are dependent of certain pre-designed geometric profiles with complicated conductivity configurations. In this paper, we propose a methodology for designing a new class of thermal source illusion devices for achieving directed thermal diffusions with natural homogeneous media. The employments of the space rotations in the linear transformation processes allow the directed thermal diffusions to be independent of the geometric profiles, and the utilization of natural homogeneous media improve the feasibility. Four schemes, with fewer types of homogeneous media filling the functional regions, are demonstrated in transient states. The expected performances are observed in each scheme. The related performance are analyzed by comparing the thermal distribution characteristics and the illusion effectiveness on the measured lines. The findings obtained in this paper see applications in the development of directed diffusions with minimal thermal loss, used in novel “multi-beam” thermal generation, thermal lenses, solar receivers, and waveguide. Full article
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Open AccessArticle T6 Treatment and Its Effects on Corrosion Properties of an Mg–4Sn–4Zn–2Al Alloy
Materials 2018, 11(4), 628; https://doi.org/10.3390/ma11040628
Received: 18 March 2018 / Revised: 11 April 2018 / Accepted: 17 April 2018 / Published: 19 April 2018
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Abstract
The effects of T6 treatment (solid-solution and artificially aging at 200 °C) on the microstructure and corrosion properties of an Mg–4Sn–4Zn–2Al (TZA442) alloy were systematically investigated. The alloy exhibits a double-peak age-hardening behavior, i.e., one is 78 HV after 10 h of aging,
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The effects of T6 treatment (solid-solution and artificially aging at 200 °C) on the microstructure and corrosion properties of an Mg–4Sn–4Zn–2Al (TZA442) alloy were systematically investigated. The alloy exhibits a double-peak age-hardening behavior, i.e., one is 78 HV after 10 h of aging, and the other is 83 HV after 50 h of aging. The strengthening effect is mainly attributed to the simultaneously and mutually independent precipitation of the dispersively distributed MgZn2 and Mg2Sn precipitates. Solid-solution treatment can significantly decrease the corrosion rate of the TZA442 alloy. The following aging treatment can initially further decrease the corrosion rate in the under-aged state, but can afterward slightly increase it after 50 h of aging. The relationship between the microstructure and corrosion properties is also discussed. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Effects of the Tempering and High-Pressure Torsion Temperatures on Microstructure of Ferritic/Martensitic Steel Grade 91
Materials 2018, 11(4), 627; https://doi.org/10.3390/ma11040627
Received: 22 March 2018 / Revised: 16 April 2018 / Accepted: 16 April 2018 / Published: 19 April 2018
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Abstract
Grade 91 (9Cr-1Mo) steel was subjected to various heat treatments and then to high-pressure torsion (HPT) at different temperatures. Its microstructure was studied using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Effects of the tempering temperature and the HPT temperature on the
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Grade 91 (9Cr-1Mo) steel was subjected to various heat treatments and then to high-pressure torsion (HPT) at different temperatures. Its microstructure was studied using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Effects of the tempering temperature and the HPT temperature on the microstructural features and microhardness in the ultrafine-grained (UFG) Grade 91 steel were researched. The study of the UFG structure formation takes into account two different microstructures observed: before HPT in both samples containing martensite and in fully ferritic samples. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle Broadband Polarization Conversion Metasurface Based on Metal Cut-Wire Structure for Radar Cross Section Reduction
Materials 2018, 11(4), 626; https://doi.org/10.3390/ma11040626
Received: 13 March 2018 / Revised: 12 April 2018 / Accepted: 17 April 2018 / Published: 19 April 2018
Cited by 3 | Viewed by 1005 | PDF Full-text (16985 KB) | HTML Full-text | XML Full-text
Abstract
A class of linear polarization conversion coding metasurfaces (MSs) based on a metal cut-wire structure is proposed, which can be applied to the reduction properties of radar cross section (RCS). We firstly present a hypothesis based on the principle of planar array theory,
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A class of linear polarization conversion coding metasurfaces (MSs) based on a metal cut-wire structure is proposed, which can be applied to the reduction properties of radar cross section (RCS). We firstly present a hypothesis based on the principle of planar array theory, and then verify the RCS reduction characteristics using linear polarization conversion coding MSs by simulations and experiments. The simulated results show that in the frequency range of 6–14 GHz, the linear polarization conversion ratio reaches a maximum value of 90%, which is in good agreement with the theoretical predictions. For normal incident x- and y-polarized waves, RCS reduction of designed coding MSs 01/01 and 01/10 is essentially more than 10 dB in the above-mentioned frequency range. We prepare and measure the 01/10 coding MS sample, and find that the experimental results in terms of reflectance and RCS reduction are in good agreement with the simulated ones under normal incidence. In addition, under oblique incidence, RCS reduction is suppressed as the angle of incidence increases, but still exhibits RCS reduction effects in a certain frequency range. The designed MS is expected to have valuable potential in applications for stealth field technology. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Sustainable Blended Cements—Influences of Packing Density on Cement Paste Chemical Efficiency
Materials 2018, 11(4), 625; https://doi.org/10.3390/ma11040625
Received: 12 March 2018 / Revised: 24 March 2018 / Accepted: 3 April 2018 / Published: 18 April 2018
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Abstract
This paper addresses the development of blended cements with reduced clinker amount by partial replacement of the clinker with more environmentally-friendly material (e.g., limestone powders). This development can lead to more sustainable cements with reduced greenhouse gas emission and energy consumption during their
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This paper addresses the development of blended cements with reduced clinker amount by partial replacement of the clinker with more environmentally-friendly material (e.g., limestone powders). This development can lead to more sustainable cements with reduced greenhouse gas emission and energy consumption during their production. The reduced clicker content was based on improved particle packing density and surface area of the cement powder by using three different limestone particle diameters: smaller (7 µm, 3 µm) or larger (70 µm, 53 µm) than the clinker particles, or having a similar size (23 µm). The effects of the different limestone particle sizes on the chemical reactivity of the blended cement were studied by X-ray diffraction (XRD), thermogravimetry and differential thermogravimetry (TG/DTG), loss on ignition (LOI), isothermal calorimetry, and the water demand for reaching normal consistency. It was found that by blending the original cement with limestone, the hydration process and the reactivity of the limestone itself were increased by the increased surface area of the limestone particles. However, the carbonation reaction was decreased with the increased packing density of the blended cement with limestone, having various sizes. Full article
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Open AccessArticle Standard Reference Materials for Cement Paste, Part I: Suggestion of Constituent Materials Based on Rheological Analysis
Materials 2018, 11(4), 624; https://doi.org/10.3390/ma11040624
Received: 21 March 2018 / Revised: 13 April 2018 / Accepted: 16 April 2018 / Published: 18 April 2018
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Abstract
The purpose of this study was to develop a standard reference material that can simulate the flow characteristics of cement paste. For this purpose, it is important to determine the constituent materials of the standard material for cement paste. Generally, cement paste is
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The purpose of this study was to develop a standard reference material that can simulate the flow characteristics of cement paste. For this purpose, it is important to determine the constituent materials of the standard material for cement paste. Generally, cement paste is a mixture of cement and water. To determine the constituent material of cement paste, it was divided into powder that can replace cement and matrix fluid. With the concept of rheology, which can evaluate the flow properties of selected materials quantitatively under certain mixing conditions, experiments were carried out step-by-step according to material composition combination, stage of aging, and material types. As a result, limestone powder was determined to be a cement substitute, and glycerol and water were determined to be a matrix fluid substitute. After an analysis of the compatibility with the required properties of the particulate standard materials, the finally selected standard reference material was found to satisfy the required performance. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessReview Generation of Well-Defined Micro/Nanoparticles via Advanced Manufacturing Techniques for Therapeutic Delivery
Materials 2018, 11(4), 623; https://doi.org/10.3390/ma11040623
Received: 5 March 2018 / Revised: 8 April 2018 / Accepted: 11 April 2018 / Published: 18 April 2018
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Abstract
Micro/nanoparticles have great potentials in biomedical applications, especially for drug delivery. Existing studies identified that major micro/nanoparticle features including size, shape, surface property and component materials play vital roles in their in vitro and in vivo applications. However, a demanding challenge is that
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Micro/nanoparticles have great potentials in biomedical applications, especially for drug delivery. Existing studies identified that major micro/nanoparticle features including size, shape, surface property and component materials play vital roles in their in vitro and in vivo applications. However, a demanding challenge is that most conventional particle synthesis techniques such as emulsion can only generate micro/nanoparticles with a very limited number of shapes (i.e., spherical or rod shapes) and have very loose control in terms of particle sizes. We reviewed the advanced manufacturing techniques for producing micro/nanoparticles with precisely defined characteristics, emphasizing the use of these well-controlled micro/nanoparticles for drug delivery applications. Additionally, to illustrate the vital roles of particle features in therapeutic delivery, we also discussed how the above-mentioned micro/nanoparticle features impact in vitro and in vivo applications. Through this review, we highlighted the unique opportunities in generating controllable particles via advanced manufacturing techniques and the great potential of using these micro/nanoparticles for therapeutic delivery. Full article
(This article belongs to the Special Issue Nanomaterials for Biomedical Applications)
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Open AccessArticle Factors Influencing NO2 Adsorption/Reduction on Microporous Activated Carbon: Porosity vs. Surface Chemistry
Materials 2018, 11(4), 622; https://doi.org/10.3390/ma11040622
Received: 14 March 2018 / Revised: 12 April 2018 / Accepted: 16 April 2018 / Published: 18 April 2018
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Abstract
The textural properties and surface chemistry of different activated carbons, prepared by the chemical activation of olive stones, have been investigated in order to gain insight on the NO2 adsorption mechanism. The parent chemical activated carbon was prepared by the impregnation of
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The textural properties and surface chemistry of different activated carbons, prepared by the chemical activation of olive stones, have been investigated in order to gain insight on the NO2 adsorption mechanism. The parent chemical activated carbon was prepared by the impregnation of olive stones in phosphoric acid followed by thermal carbonization. Then, the textural properties and surface chemistry were modified by chemical treatments including nitric acid, sodium hydroxide and/or a thermal treatment at 900 °C. The main properties of the parent and modified activated carbons were analyzed by N2-adsorption, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques, in order to enlighten the modifications issued from the chemical and thermal treatments. The NO2 adsorption capacities of the different activated carbons were measured in fixed bed experiments under 500 ppmv NO2 concentrations at room temperature. Temperature programmed desorption (TPD) was applied after adsorption tests in order to quantify the amount of the physisorbed and chemisorbed NO2. The obtained results showed that the development of microporosity, the presence of oxygen-free sites, and the presence of basic surface groups are key factors for the efficient adsorption of NO2. Full article
(This article belongs to the Special Issue Green Activated Carbons)
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Open AccessArticle Fabrication of FeAl Intermetallic Foams by Tartaric Acid-Assisted Self-Propagating High-Temperature Synthesis
Materials 2018, 11(4), 621; https://doi.org/10.3390/ma11040621
Received: 23 March 2018 / Revised: 12 April 2018 / Accepted: 13 April 2018 / Published: 18 April 2018
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Abstract
Iron aluminides are intermetallics with interesting applications in porous form thanks to their mechanical and corrosion resistance properties. However, making porous forms of these materials is not easy due to their high melting points. We formed FeAl foams by elemental iron and aluminum
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Iron aluminides are intermetallics with interesting applications in porous form thanks to their mechanical and corrosion resistance properties. However, making porous forms of these materials is not easy due to their high melting points. We formed FeAl foams by elemental iron and aluminum powders sintering with tartaric acid additive. Tartaric acid worked as an in situ gas-releasing agent during the self-propagating high-temperature synthesis of FeAl intermetallic alloy, which was confirmed by X-ray diffraction measurements. The porosity of the formed foams was up to 36 ± 4%. In the core of the sample, the average equivalent circle diameter was found to be 47 ± 20 µm, while on the surface, it was 35 ± 16 µm; thus, the spread of the pore size was smaller than reported previously. To investigate functional applications of the formed FeAl foam, the pressure drop of air during penetration of the foam was examined. It was found that increased porosity of the material increased the flow of the air through the metallic foam. Full article
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