Materials

10 pages, 1895 KiB

Open AccessFeature PaperArticle

Time-Dependent Density Functional Computations of the Spectrochemical Properties of Dithiolodithiole and Thiophene Electrochromic Systems

by Bruna Clara De Simone, Gloria Mazzone^*, Tiziana Marino

, Nino Russo^* and Marirosa Toscano

Dipartimento di Chimica e Tecnologie Chimiche, Università della Calabria, I-87036 Arcavacata di Rende, Italy

Materials 2017, 10(9), 981; https://doi.org/10.3390/ma10090981 - 23 Aug 2017

Cited by 7 | Viewed by 3712

Abstract

The importance of organic electrochromic materials has grown considerably in recent decades due to their application in smart window, automotive, and aircraft technologies. Theoretical prediction of the optical properties should contribute to their better characterization and help the explanation of the experimental data. [...] Read more.

The importance of organic electrochromic materials has grown considerably in recent decades due to their application in smart window, automotive, and aircraft technologies. Theoretical prediction of the optical properties should contribute to their better characterization and help the explanation of the experimental data. By using various exchange–correlation functionals, we show how density functional theory (DFT) and the related time-dependent formulation (TDDFT) are able to correctly reproduce the spectrochemical properties of dithiolodithiole and thiophene organic electrochromic systems. Full article

(This article belongs to the Special Issue Organic Electrochromic Materials)

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20 pages, 5241 KiB

Open AccessArticle

Identification of Upper and Lower Level Yield Strength in Materials

by Jan Valíček^1,2,3,*, Marta Harničárová^1,2, Ivan Kopal^1,4, Zuzana Palková³

, Milena Kušnerová^1,2, Anton Panda⁵ and Vladimír Šepelák^1,6

¹ Institute of Physics, Faculty of Mining and Geology, Vysoká škola báňská—Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava, Czech Republic

² Regional Materials Science and Technology Centre, Vysoká škola báňská—Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava, Czech Republic

³ Technical Faculty, Slovak University of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76 Nitra, Slovakia

⁴ Department of Numerical Methods and Computing Modelling, Faculty of Industrial Technologies in Púchov, Alexander Dubček University of Trenčín, Ivana Krasku 491/30, 020 01 Púchov, Slovakia

⁵ Faculty of Manufacturing Technologies with a Seat in Prešov, Technical University of Kosice, Bayerova Street 1, 080 01 Prešov, Slovakia

⁶ Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

Materials 2017, 10(9), 982; https://doi.org/10.3390/ma10090982 - 23 Aug 2017

Cited by 37 | Viewed by 5597

Abstract

This work evaluates the possibility of identifying mechanical parameters, especially upper and lower yield points, by the analytical processing of specific elements of the topography of surfaces generated with abrasive waterjet technology. We developed a new system of equations, which are connected with [...] Read more.

This work evaluates the possibility of identifying mechanical parameters, especially upper and lower yield points, by the analytical processing of specific elements of the topography of surfaces generated with abrasive waterjet technology. We developed a new system of equations, which are connected with each other in such a way that the result of a calculation is a comprehensive mathematical–physical model, which describes numerically as well as graphically the deformation process of material cutting using an abrasive waterjet. The results of our model have been successfully checked against those obtained by means of a tensile test. The main prospect for future applications of the method presented in this article concerns the identification of mechanical parameters associated with the prediction of material behavior. The findings of this study can contribute to a more detailed understanding of the relationships: material properties—tool properties—deformation properties. Full article

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17 pages, 4905 KiB

Open AccessArticle

In Vitro Effectiveness of Microspheres Based on Silk Sericin and Chlorella vulgaris or Arthrospira platensis for Wound Healing Applications

by Elia Bari¹

, Carla Renata Arciola^2,3

, Barbara Vigani¹, Barbara Crivelli¹, Paola Moro¹, Giorgio Marrubini¹, Milena Sorrenti¹

, Laura Catenacci¹, Giovanna Bruni⁴, Theodora Chlapanidas¹, Enrico Lucarelli⁵, Sara Perteghella^1,*

and Maria Luisa Torre¹

¹ Department of Drug Sciences, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy

² Research Unit on Implant Infections, Rizzoli Orthopaedic Institute of Bologna, Via di Barbiano 1/10, 40136 Bologna, Italy

³ Department of Experimental, University of Bologna, Diagnostic and Specialty Medicine (DIMES), Via San Giacomo 14, 40126 Bologna, Italy

⁴ Department of Chemistry, University of Pavia, Viale Taramelli 16, 27100 Pavia, Italy

⁵ Osteoarticular Regeneration Laboratory, Rizzoli Orthopaedic Institute of Bologna, Via Giulio Cesare Pupilli 1, 40136 Bologna, Italy

Materials 2017, 10(9), 983; https://doi.org/10.3390/ma10090983 - 23 Aug 2017

Cited by 45 | Viewed by 6933

Abstract

Some natural compounds have recently been widely employed in wound healing applications due to their biological properties. One such compound is sericin, which is produced by Bombix mori, while active polyphenols, polysaccharides and proteins are synthetized by Chlorella vulgaris and Arthrospira platensis [...] Read more.

Some natural compounds have recently been widely employed in wound healing applications due to their biological properties. One such compound is sericin, which is produced by Bombix mori, while active polyphenols, polysaccharides and proteins are synthetized by Chlorella vulgaris and Arthrospira platensis microalgae. Our hypothesis was that sericin, as an optimal bioactive polymeric carrier for microencapsulation process, could also improve the regenerative effect of the microalgae. A solvent-free extraction method and spray drying technique were combined to obtain five formulations, based on algal extracts (C. vulgaris and A. platensis, Chl and Art, respectively) or silk sericin (Ser) or their mixtures (Chl-Ser and Art-Ser). The spray drying was a suitable method to produce microspheres with similar dimensions, characterized by collapsed morphology with a rough surface. Art and Art-Ser showed higher antioxidant properties than other formulations. All microspheres resulted in cytocompatibility on fibroblasts until 1.25 mg/mL and promoted cell migration and the complete wound closure; this positive effect was further highlighted after treatment with Art and Art-Ser. To our surprize the combination of sericin to Art did not improve the microalgae extract efficacy, at least in our experimental conditions. Full article

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

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16 pages, 12633 KiB

Open AccessArticle

Numerical and Experimental Studies on the Explosive Welding of Tungsten Foil to Copper

by Qiang Zhou, Jianrui Feng and Pengwan Chen^*

State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China

Materials 2017, 10(9), 984; https://doi.org/10.3390/ma10090984 - 23 Aug 2017

Cited by 59 | Viewed by 6701

Abstract

This work verifies that the W foil could be successfully welded on Cu through conventional explosive welding, without any cracks. The microstructure was observed through scanning electron microscopy (SEM), optical microscopy and energy-dispersive X-ray spectrometry (EDS). The W/Cu interface exhibited a wavy morphology, [...] Read more.

This work verifies that the W foil could be successfully welded on Cu through conventional explosive welding, without any cracks. The microstructure was observed through scanning electron microscopy (SEM), optical microscopy and energy-dispersive X-ray spectrometry (EDS). The W/Cu interface exhibited a wavy morphology, and no intermetallic or transition layer was observed. The wavy interface formation, as well as the distributions of temperature, pressure and plastic strain at the interface were studied through numerical simulation with Smoothed Particle Hydrodynamics (SPH). The welding mechanism of W/Cu was analyzed according to the numerical results and experimental observation, which was in accordance with the indentation mechanism proposed by Bahrani. Full article

(This article belongs to the Special Issue Welding, Joining and Casting of Advanced Materials)

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12 pages, 6262 KiB

Open AccessArticle

Optical CAD Utilization for the Design and Testing of a LED Streetlamp

by David Jafrancesco, Luca Mercatelli, Daniela Fontani and Paola Sansoni^*

CNR-INO National Institute of Optics, Largo E. Fermi, 6-50125 Firenze, Italy

Materials 2017, 10(9), 985; https://doi.org/10.3390/ma10090985 - 24 Aug 2017

Cited by 1 | Viewed by 3876

Abstract

The design and testing of LED lamps are vital steps toward broader use of LED lighting for outdoor illumination and traffic signalling. The characteristics of LED sources, in combination with the need to limit light pollution and power consumption, require a precise optical [...] Read more.

The design and testing of LED lamps are vital steps toward broader use of LED lighting for outdoor illumination and traffic signalling. The characteristics of LED sources, in combination with the need to limit light pollution and power consumption, require a precise optical design. In particular, in every step of the process, it is important to closely compare theoretical or simulated results with measured data (obtained from a prototype). This work examines the various possibilities for using an optical CAD (Lambda Research TracePro) to design and check a LED lamp for outdoor use. This analysis includes the simulations and testing on a prototype as an example; data acquired by measurement are inserted into the same simulation software, making it easy to compare theoretical and actual results. Full article

(This article belongs to the Special Issue Light Emitting Diodes and Laser Diodes: Materials and Devices)

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8 pages, 2116 KiB

Open AccessArticle

Exploring the Effects of Argon Plasma Treatment on Plasmon Frequency and the Chemiresistive Properties of Polymer-Carbon Nanotube Metacomposite

by Manuel Rivera¹, Mostafizur Rahaman²

, Ali Aldalbahi^2,*

, Rafael Velázquez¹, Andrew F. Zhou³ and Peter X. Feng^1,*

¹ Department of Physics, University of Puerto Rico, San Juan, PR 00936-8377, USA

² Department of Chemistry, College of Science, King Saud University, Riyadh 11451, Saudi Arabia

³ Department of Physics, Indiana University of Pennsylvania, 975 Oakland Ave, Indiana, PA 15705, USA

Materials 2017, 10(9), 986; https://doi.org/10.3390/ma10090986 - 24 Aug 2017

Cited by 3 | Viewed by 4299

Abstract

Metacomposites, composite materials exhibiting negative permittivity, represent an opportunity to create materials with depressed plasmon frequency without the need to create complex structural geometries. Although many reports exist on the synthesis and characterizations of metacomposites, very few have ventured into exploring possible applications [...] Read more.

Metacomposites, composite materials exhibiting negative permittivity, represent an opportunity to create materials with depressed plasmon frequency without the need to create complex structural geometries. Although many reports exist on the synthesis and characterizations of metacomposites, very few have ventured into exploring possible applications that could take advantage of the unique electrical properties of these materials. In this article, we report on the chemiresistive properties of a polymer-CNT metacomposite and explore how these are affected by Argon plasma treatment. Full article

(This article belongs to the Section Advanced Composites)

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Graphical abstract

14 pages, 16924 KiB

Open AccessArticle

Novel Approach in the Use of Plasma Spray: Preparation of Bulk Titanium for Bone Augmentations

by Michaela Fousova^1,*, Dalibor Vojtech¹, Eva Jablonska², Jaroslav Fojt¹ and Jan Lipov²

¹ Department of Metals and Corrosion Engineering, University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic

² Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic

Materials 2017, 10(9), 987; https://doi.org/10.3390/ma10090987 - 24 Aug 2017

Cited by 22 | Viewed by 4589

Abstract

Thermal plasma spray is a common, well-established technology used in various application fields. Nevertheless, in our work, this technology was employed in a completely new way; for the preparation of bulk titanium. The aim was to produce titanium with properties similar to human [...] Read more.

Thermal plasma spray is a common, well-established technology used in various application fields. Nevertheless, in our work, this technology was employed in a completely new way; for the preparation of bulk titanium. The aim was to produce titanium with properties similar to human bone to be used for bone augmentations. Titanium rods sprayed on a thin substrate wire exerted a porosity of about 15%, which yielded a significant decrease of Young′s modulus to the bone range and provided rugged topography for enhanced biological fixation. For the first verification of the suitability of the selected approach, tests of the mechanical properties in terms of compression, bending, and impact were carried out, the surface was characterized, and its compatibility with bone cells was studied. While preserving a high enough compressive strength of 628 MPa, the elastic modulus reached 11.6 GPa, thus preventing a stress-shielding effect, a generally known problem of implantable metals. U-2 OS and Saos-2 cells derived from bone osteosarcoma grown on the plasma-sprayed surface showed good viability. Full article

(This article belongs to the Section Biomaterials)

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10 pages, 4447 KiB

Open AccessArticle

Enhanced Cycleability of Amorphous MnO₂ by Covering on α-MnO₂ Needles in an Electrochemical Capacitor

by Quanbing Liu¹, Shan Ji^2,*, Juan Yang³, Hui Wang³, Bruno G. Pollet⁴

and Rongfang Wang^3,*

¹ School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China

² College of Biological, Chemical Science and Chemical Engineering, Jiaxing University, Jiaxing 314001, China

³ Institute of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042, China

⁴ Renewable Energy Group, Department of Energy and Process Engineering, Faculty of Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway

Materials 2017, 10(9), 988; https://doi.org/10.3390/ma10090988 - 24 Aug 2017

Cited by 29 | Viewed by 6100

Abstract

An allomorph MnO₂@MnO₂ core-shell nanostructure was developed via a two-step aqueous reaction method. The data analysis of Scanning Electron Microscopy, Transmission Electron Microscopy, X-Ray Diffraction and N₂ adsorption-desorption isotherms experiments indicated that this unique architecture consisted of a porous [...] Read more.

An allomorph MnO₂@MnO₂ core-shell nanostructure was developed via a two-step aqueous reaction method. The data analysis of Scanning Electron Microscopy, Transmission Electron Microscopy, X-Ray Diffraction and N₂ adsorption-desorption isotherms experiments indicated that this unique architecture consisted of a porous layer of amorphous-MnO₂ nano-sheets which were well grown onto the surface of α-MnO₂ nano-needles. Cyclic voltammetry experiments revealed that the double-layer charging and Faradaic pseudo-capacity of the MnO₂@MnO₂ capacitor electrode contributed to a specific capacitance of 150.3 F·g⁻¹ at a current density of 0.1 A·g⁻¹. Long cycle life experiments on the as-prepared MnO₂@MnO₂ sample showed nearly a 99.3% retention after 5000 cycles at a current density of 2 A·g⁻¹. This retention value was found to be significantly higher than those reported for amorphous MnO₂-based capacitor electrodes. It was also found that the remarkable cycleability of the MnO₂@MnO₂ was due to the supporting role of α-MnO₂ nano-needle core and the outer amorphous MnO₂ layer. Full article

(This article belongs to the Special Issue Energetic Materials and Processes)

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15 pages, 12159 KiB

Open AccessArticle

Experimental Investigation on Surface Quality Processed by Self-Excited Oscillation Pulsed Waterjet Peening

by Xiaolong Ding^1,2,3, Yong Kang^1,2,3,4,*, Deng Li^1,2,3

, Xiaochuan Wang^1,2,3

and Dongping Zeng^1,2,3

¹ Key Laboratory of Hydraulic Machinery Transients, Ministry of Education, Wuhan University, Wuhan 430072, China

² Hubei Key Laboratory of Waterjet Theory and New Technology, Wuhan University, Wuhan 430072, China

³ School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China

⁴ Collaborative Innovation Center of Geospatial Technology, 129 Luoyu Road, Wuhan 430072, China

Materials 2017, 10(9), 989; https://doi.org/10.3390/ma10090989 - 25 Aug 2017

Cited by 24 | Viewed by 4406

Abstract

High-speed waterjet peening technology has attracted a lot of interest and is now being widely studied due to its great ability to strengthen metal surfaces. In order to further improve the mechanical properties of metals, self-excited oscillation pulsed waterjets (SOPWs) were used for [...] Read more.

High-speed waterjet peening technology has attracted a lot of interest and is now being widely studied due to its great ability to strengthen metal surfaces. In order to further improve the mechanical properties of metals, self-excited oscillation pulsed waterjets (SOPWs) were used for surface peening with an experimental investigation focused on the surface topography and properties. By impinging the aluminum alloy (5052) specimens with SOPWs issuing from an organ-pipe oscillation nozzle, the hardness and roughness at various inlet pressures and stand-off distances were measured and analyzed, as well as the residual stress. Under the condition of optimum stand-off distances, the microscopic appearances of peened specimens obtained by SEM were displayed and analyzed. Results show that self-excited oscillation pulsed waterjet peening (SOPWP) is capable of improving the surface quality. More specifically, compared with an untreated surface, the hardness and residual stress of the peened surfaces were increased by 61.69% and 148%, respectively. There exists an optimal stand-off distance and operating pressure for creating the highest surface quality. SOPWP can produce almost the same enhancement effect as shot peening and lead to a lower surface roughness. Although such an approach is empirical and qualitative in nature, this procedure also generated information of value in guiding future theoretical and experimental work on the application of SOPWP in the industry practice. Full article

(This article belongs to the Special Issue Wear-Corrosion Synergy, Nanocoating and Control of Materials)

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15 pages, 10724 KiB

Open AccessArticle

Improvement of Interaction in a Composite Structure by Using a Sol-Gel Functional Coating on Carbon Fibers

by Anna Szczurek¹

, Michał Barcikowski¹, Karol Leluk², Bartosz Babiarczuk¹, Jerzy Kaleta¹ and Justyna Krzak^1,*

¹ Department of Mechanics, Materials Science and Engineering, Faculty of Mechanical Engineering, Wroclaw University of Science and Technology, 25 Smoluchowskiego, 50-370 Wroclaw, Poland

² Department of Environmental Engineering, Wroclaw University of Science and Technology, 9 Grunwaldzki Square, 50-377 Wroclaw, Poland

Materials 2017, 10(9), 990; https://doi.org/10.3390/ma10090990 - 25 Aug 2017

Cited by 19 | Viewed by 5919

Abstract

The modification of carbon fibers for improving adhesion between fibers and an epoxy resin in composite materials has become the focus of attention. In this work the carbon fiber coating process has been devised in a way preventing the stiffening and clumping of [...] Read more.

The modification of carbon fibers for improving adhesion between fibers and an epoxy resin in composite materials has become the focus of attention. In this work the carbon fiber coating process has been devised in a way preventing the stiffening and clumping of fibers. To improve interactions between coated fibers and a resin in composites, four types of silica coatings with different organic functional groups (3-aminopropyl–coating 1, 3-mercaptopropyl–coating 2, 2-(3,4-epoxycyclohexyl) ethyl–coating 3, methyl–coating 4) were obtained. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to distinguish the changes of a carbon fibers surface after coating deposition. The thickness of the obtained coatings, including the diversity of thickness, was determined by transmission electron microscopy (TEM). The increase in surface free energy (SFE) of modified fibers, including the distinction between the polar and dispersive parts, was examined by wettability measurements using a tensometric test. The developed coating preparation process allowed to cover fibers separately with nanoscale silica layers, which changed their morphology. The introduction of organic functional groups resulted in surface free energy changes, especially an increase in specific polar surface energy components. Full article

(This article belongs to the Section Advanced Composites)

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10 pages, 3523 KiB

Open AccessFeature PaperArticle

Heat-Assisted Multiferroic Solid-State Memory

by Serban Lepadatu^1,*

and Melvin M. Vopson²

¹ Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston PR1 2HE, UK

² SEES, Faculty of Science, University of Portsmouth, Portsmouth PO1 3QL, UK

Materials 2017, 10(9), 991; https://doi.org/10.3390/ma10090991 - 25 Aug 2017

Cited by 5 | Viewed by 4141

Abstract

A heat-assisted multiferroic solid-state memory design is proposed and analysed, based on a PbNbZrSnTiO₃ antiferroelectric layer and Ni₈₁Fe₁₉ magnetic free layer. Information is stored as magnetisation direction in the free layer of a magnetic tunnel junction element. The bit [...] Read more.

A heat-assisted multiferroic solid-state memory design is proposed and analysed, based on a PbNbZrSnTiO₃ antiferroelectric layer and Ni₈₁Fe₁₉ magnetic free layer. Information is stored as magnetisation direction in the free layer of a magnetic tunnel junction element. The bit writing process is contactless and relies on triggering thermally activated magnetisation switching of the free layer towards a strain-induced anisotropy easy axis. A stress is generated using the antiferroelectric layer by voltage-induced antiferroelectric to ferroelectric phase change, and this is transmitted to the magnetic free layer by strain-mediated coupling. The thermally activated strain-induced magnetisation switching is analysed here using a three-dimensional, temperature-dependent magnetisation dynamics model, based on simultaneous evaluation of the stochastic Landau-Lifshitz-Bloch equation and heat flow equation, together with stochastic thermal fields and magnetoelastic contributions. The magnetisation switching probability is calculated as a function of stress magnitude and maximum heat pulse temperature. An operating region is identified, where magnetisation switching always occurs, with stress values ranging from 80 to 180 MPa, and maximum temperatures normalised to the Curie temperature ranging from 0.65 to 0.99. Full article

(This article belongs to the Special Issue Physics, Measurements and Applications of Multiferroic and Magnetoelectric Materials)

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12 pages, 5045 KiB

Open AccessArticle

Preparation of Luminescent Metal-Organic Framework Films by Soft-Imprinting for 2,4-Dinitrotoluene Sensing

by Javier Roales^1,*

, Francisco G. Moscoso¹, Francisco Gámez¹

, Tânia Lopes-Costa¹, Ahmad Sousaraei², Santiago Casado², Jose R. Castro-Smirnov², Juan Cabanillas-Gonzalez²

, José Almeida³

, Carla Queirós³, Luís Cunha-Silva³, Ana M. G. Silva³

and José M. Pedrosa^1,*

¹ Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Ctra. Utrera Km. 1, 41013 Sevilla, Spain

² Madrid Institute for Advanced Studies in Nanoscience, IMDEA Nanociencia, Calle Faraday 9, Ciudad Universitaria de Cantoblanco, 28049 Madrid, Spain

³ REQUIMTE-LAQV & Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal

Materials 2017, 10(9), 992; https://doi.org/10.3390/ma10090992 - 25 Aug 2017

Cited by 29 | Viewed by 6493

Abstract

A novel technique for the creation of metal-organic framework (MOF) films based on soft-imprinting and their use as gas sensors was developed. The microporous MOF material [Zn₂(bpdc)₂(bpee)] (bpdc = 4,4′-biphenyldicarboxylate; bpee = 1,2-bipyridylethene) was synthesized solvothermally and activated by [...] Read more.

A novel technique for the creation of metal-organic framework (MOF) films based on soft-imprinting and their use as gas sensors was developed. The microporous MOF material [Zn₂(bpdc)₂(bpee)] (bpdc = 4,4′-biphenyldicarboxylate; bpee = 1,2-bipyridylethene) was synthesized solvothermally and activated by removing the occluded solvent molecules from its inner channels. MOF particles were characterized by powder X-ray diffraction and fluorescence spectroscopy, showing high crystallinity and intense photoluminescence. Scanning electron microscope images revealed that MOF crystals were mainly in the form of microneedles with a high surface-to-volume ratio, which together with the high porosity of the material enhances its interaction with gas molecules. MOF crystals were soft-imprinted into cellulose acetate (CA) films on quartz at different pressures. Atomic force microscope images of soft-imprinted films showed that MOF crystals were partially embedded into the CA. With this procedure, mechanically stable films were created, with crystals protruding from the CA surface and therefore available for incoming gas molecules. The sensing properties of the films were assessed by exposing them to saturated atmospheres of 2,4-dinitrotoluene, which resulted in a substantial quenching of the fluorescence after few seconds. The soft-imprinted MOF films on CA/quartz exhibit good sensing capabilities for the detection of nitroaromatics, which was attributed to the MOF sensitivity and to the novel and more efficient film processing method based on soft-imprinting. Full article

(This article belongs to the Special Issue Luminescent Materials 2017)

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19 pages, 9343 KiB

Open AccessArticle

Fatigue Performance of Ti-6Al-4V Additively Manufactured Specimens with Integrated Capillaries of an Embedded Structural Health Monitoring System

by Michaël Hinderdael^1,*, Maria Strantza², Dieter De Baere¹, Wim Devesse¹, Iris De Graeve³, Herman Terryn³ and Patrick Guillaume¹

¹ Department of Mechanical Engineering, Vrije Universiteit Brussel, 1050 Brussels, Belgium

² Department of Mechanics of Materials and Constructions, Vrije Universiteit Brussel, 1050 Brussels, Belgium

³ Department of Electrochemical and Surface Engineering, Vrije Universiteit Brussel, 1050 Brussels, Belgium

Materials 2017, 10(9), 993; https://doi.org/10.3390/ma10090993 - 25 Aug 2017

Cited by 17 | Viewed by 6029

Abstract

Additive manufacturing (AM) of metals offers new possibilities for the production of complex structures. Up to now, investigations on the mechanical response of AM metallic parts show a significant spread and unexpected failures cannot be excluded. In this work, we focus on the [...] Read more.

Additive manufacturing (AM) of metals offers new possibilities for the production of complex structures. Up to now, investigations on the mechanical response of AM metallic parts show a significant spread and unexpected failures cannot be excluded. In this work, we focus on the detection of fatigue cracks through the integration of a Structural Health Monitoring (SHM) system in Ti-6Al-4V specimens. The working principle of the presented system is based on the integration of small capillaries that are capable of detecting fatigue cracks. Four-point bending fatigue tests have been performed on Ti-6Al-4V specimens with integrated capillaries and compared to the reference specimenswithout capillaries. Specimens were produced by conventional subtractive manufacturing of wrought material and AM, using the laser based Directed Energy Deposition (DED) process. In this study, we investigated the effect of the presence of the capillary on the fatigue strength and fatigue initiation location. Finite element (FEM) simulations were performed to validate the experimental test results. The presence of a drilled capillary in the specimens did not alter the fatigue initiation location. However, the laser based DED production process introduced roughness on the capillary surface that altered the fatigue initiation location to the capillary surface. The fatigue performance was greatly reduced when considering a printed capillary. It is concluded that the surface quality of the integrated capillary is of primary importance in order not to influence the structural integrity of the component to be monitored. Full article

(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)

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19 pages, 1037 KiB

Open AccessFeature PaperArticle

Growth Description for Vessel Wall Adaptation: A Thick-Walled Mixture Model of Abdominal Aortic Aneurysm Evolution

by Andrii Grytsan^1,2

, Thomas S. E. Eriksson³, Paul N. Watton^2,4,5

and T. Christian Gasser^1,*,†

¹ KTH Solid Mechanics, KTH Royal Institute of Technology, 100 44 Stockholm, Sweden

² Insigneo Institute for in silico Medicine, University of Sheffield, Sheffield S1 3JD, UK

³ Swedish Defence Research Agency, 164 90 Stockholm, Sweden

⁴ Department of Computer Science, University of Sheffield, Sheffield S1 4DP, UK

⁵ Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261, USA

^† Current address: Teknikringen 8D, KTH Solid Mechanics, KTH Royal Institute of Technology, 100 44 Stockholm, Sweden.

Materials 2017, 10(9), 994; https://doi.org/10.3390/ma10090994 - 25 Aug 2017

Cited by 39 | Viewed by 6025

Abstract

(1) Background: Vascular tissue seems to adapt towards stable homeostatic mechanical conditions, however, failure of reaching homeostasis may result in pathologies. Current vascular tissue adaptation models use many ad hoc assumptions, the implications of which are far from being fully understood; (2) Methods: [...] Read more.

(1) Background: Vascular tissue seems to adapt towards stable homeostatic mechanical conditions, however, failure of reaching homeostasis may result in pathologies. Current vascular tissue adaptation models use many ad hoc assumptions, the implications of which are far from being fully understood; (2) Methods: The present study investigates the plausibility of different growth kinematics in modeling Abdominal Aortic Aneurysm (AAA) evolution in time. A structurally motivated constitutive description for the vessel wall is coupled to multi-constituent tissue growth descriptions; Constituent deposition preserved either the constituent’s density or its volume, and Isotropic Volume Growth (IVG), in-Plane Volume Growth (PVG), in-Thickness Volume Growth (TVG) and No Volume Growth (NVG) describe the kinematics of the growing vessel wall. The sensitivity of key modeling parameters is explored, and predictions are assessed for their plausibility; (3) Results: AAA development based on TVG and NVG kinematics provided not only quantitatively, but also qualitatively different results compared to IVG and PVG kinematics. Specifically, for IVG and PVG kinematics, increasing collagen mass production accelerated AAA expansion which seems counterintuitive. In addition, TVG and NVG kinematics showed less sensitivity to the initial constituent volume fractions, than predictions based on IVG and PVG; (4) Conclusions: The choice of tissue growth kinematics is of crucial importance when modeling AAA growth. Much more interdisciplinary experimental work is required to develop and validate vascular tissue adaption models, before such models can be of any practical use. Full article

(This article belongs to the Special Issue Constitutive Modelling of Biological Tissues and Biomaterials)

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17 pages, 3871 KiB

Open AccessReview

Synthesis of Hollow Sphere and 1D Structural Materials by Sol-Gel Process

by Fa-Liang Li^1,2,* and Hai-Jun Zhang¹

¹ The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China

² Jiangxi Engineering Research Center of Industrial Ceramics, Pingxiang 337022, China

Materials 2017, 10(9), 995; https://doi.org/10.3390/ma10090995 - 25 Aug 2017

Cited by 12 | Viewed by 9871

Abstract

The sol-gel method is a simple and facile wet chemical process for fabricating advanced materials with high homogeneity, high purity, and excellent chemical reactivity at a relatively low temperature. By adjusting the processing parameters, the sol-gel technique can be used to prepare hollow [...] Read more.

The sol-gel method is a simple and facile wet chemical process for fabricating advanced materials with high homogeneity, high purity, and excellent chemical reactivity at a relatively low temperature. By adjusting the processing parameters, the sol-gel technique can be used to prepare hollow sphere and 1D structural materials that exhibit a wide application in the fields of catalyst, drug or gene carriers, photoactive, sensors and Li-ion batteries. This feature article reviewed the development of the preparation of hollow sphere and 1D structural materials using the sol-gel method. The effects of calcination temperature, soaking time, pH value, surfactant, etc., on the preparation of hollow sphere and 1D structural materials were summarized, and their formation mechanisms were generalized. Finally, possible future research directions of the sol-gel technique were outlined. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry Applied to Materials Science)

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13 pages, 5955 KiB

Open AccessArticle

Experimental Study on Fatigue Behaviour of Shot-Peened Open-Hole Steel Plates

by Zhi-Yu Wang^1,2, Qing-Yuan Wang^2,3,* and Mengqin Cao¹

¹ Department of Civil Engineering, Sichuan University, Chengdu 610065, China

² Sichuan Provincial Key Laboratory of Failure Mechanics and Engineering Disaster Prevention & Mitigation, Sichuan University, Chengdu 610065, China

³ School of Architecture and Civil Engineering, Chengdu University, Chengdu 610106, China

Materials 2017, 10(9), 996; https://doi.org/10.3390/ma10090996 - 25 Aug 2017

Cited by 16 | Viewed by 4560

Abstract

This paper presents an experimental study on the fatigue behaviour of shot-peened open-hole plates with Q345 steel. The beneficial effects induced by shot peening on the fatigue life improvement are highlighted. The characteristic fatigue crack initiation and propagation modes of open-hole details under [...] Read more.

This paper presents an experimental study on the fatigue behaviour of shot-peened open-hole plates with Q345 steel. The beneficial effects induced by shot peening on the fatigue life improvement are highlighted. The characteristic fatigue crack initiation and propagation modes of open-hole details under fatigue loading are revealed. The surface hardening effect brought by the shot peening is analyzed from the aspects of in-depth micro-hardness and compressive residual stress. The fatigue life results are evaluated and related design suggestions are made as a comparison with codified detail categories. In particular, a fracture mechanics theory-based method is proposed and demonstrated its validity in predicting the fatigue life of studied shot-peened open-hole details. Full article

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15 pages, 3621 KiB

Open AccessArticle

Enhancing the Ignition, Hardness and Compressive Response of Magnesium by Reinforcing with Hollow Glass Microballoons

by Vyasaraj Manakari¹

, Gururaj Parande¹

, Mrityunjay Doddamani²

and Manoj Gupta^1,*

¹ Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore

² Advanced Manufacturing Laboratory, Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal 575025, India

Materials 2017, 10(9), 997; https://doi.org/10.3390/ma10090997 - 25 Aug 2017

Cited by 51 | Viewed by 5107

Abstract

Magnesium (Mg)/glass microballoons (GMB) metal matrix syntactic foams (1.47–1.67 g/cc) were synthesized using a disintegrated melt deposition (DMD) processing route. Such syntactic foams are of great interest to the scientific community as potential candidate materials for the ever-changing demands in automotive, aerospace, and [...] Read more.

Magnesium (Mg)/glass microballoons (GMB) metal matrix syntactic foams (1.47–1.67 g/cc) were synthesized using a disintegrated melt deposition (DMD) processing route. Such syntactic foams are of great interest to the scientific community as potential candidate materials for the ever-changing demands in automotive, aerospace, and marine sectors. The synthesized composites were evaluated for their microstructural, thermal, and compressive properties. Results showed that microhardness and the dimensional stability of pure Mg increased with increasing GMB content. The ignition response of these foams was enhanced by ~22 °C with a 25 wt % GMB addition to the Mg matrix. The authors of this work propose a new parameter, ignition factor, to quantify the superior ignition performance that the developed Mg foams exhibit. The room temperature compressive strengths of pure Mg increased with the addition of GMB particles, with Mg-25 wt % GMB exhibiting the maximum compressive yield strength (CYS) of 161 MPa and an ultimate compressive strength (UCS) of 232 MPa for a GMB addition of 5 wt % in Mg. A maximum failure strain of 37.7% was realized in Mg-25 wt % GMB foam. The addition of GMB particles significantly enhanced the energy absorption by ~200% prior to compressive failure for highest filler loading, as compared to pure Mg. Finally, microstructural changes in Mg owing to the presence of hollow GMB particles were elaborately discussed. Full article

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Graphical abstract

16 pages, 4953 KiB

Open AccessArticle

Green Composites Based on Blends of Polypropylene with Liquid Wood Reinforced with Hemp Fibers: Thermomechanical Properties and the Effect of Recycling Cycles

by Gianluca Cicala^1,*

, Claudio Tosto¹

, Alberta Latteri¹, Angela Daniela La Rosa¹, Ignazio Blanco^1,*

, Ahmed Elsabbagh^2,3

, Pietro Russo⁴

and Gerhard Ziegmann³

¹ Department of Civil Engineering and Architecture, University of Catania, Viale Andrea Doria 6, Catania 95125, Italy

² Design and Production Engineering Department, Faculty of Engineering, Ain Shams University, 1 Assarayat St., Abbasiya, Al Waili, Cairo Governorate 1153, Egypt

³ Institute of Polymer Materials and Plastics Engineering, Clausthal University of Technology, Agricolastr. 6, Clausthal-Zellerfeld 38678, Germany

⁴ Institute for Polymers, Composites and Biomaterials, National Research Council, Via Campi Flegrei 34, Pozzuoli 80078, Italy

Materials 2017, 10(9), 998; https://doi.org/10.3390/ma10090998 - 26 Aug 2017

Cited by 44 | Viewed by 6390

Abstract

Green composites from polypropylene and lignin-based natural material were manufactured using a melt extrusion process. The lignin-based material used was the so called “liquid wood”. The PP/“Liquid Wood” blends were extruded with “liquid wood” content varying from 20 wt % to 80 wt [...] Read more.

Green composites from polypropylene and lignin-based natural material were manufactured using a melt extrusion process. The lignin-based material used was the so called “liquid wood”. The PP/“Liquid Wood” blends were extruded with “liquid wood” content varying from 20 wt % to 80 wt %. The blends were thoroughly characterized by flexural, impact, and dynamic mechanical testing. The addition of the Liquid Wood resulted in a great improvement in terms of both the flexural modulus and strength but, on the other hand, a reduction of the impact strength was observed. For one blend composition, the composites reinforced with hemp fibers were also studied. The addition of hemp allowed us to further improve the mechanical properties. The composite with 20 wt % of hemp, subjected to up to three recycling cycles, showed good mechanical property retention and thermal stability after recycling. Full article

(This article belongs to the Special Issue Recycled Materials, Eco-design and 3D Printing)

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13 pages, 10527 KiB

Open AccessArticle

Preparation of Desirable Porous Cell Structure Polylactide/Wood Flour Composite Foams Assisted by Chain Extender

by Youyong Wang¹, Yongming Song^1,*

, Jun Du¹

, Zhenhao Xi² and Qingwen Wang³

¹ Key Laboratory of Bio-Based Material Science and Technology (Ministry of Education), Northeast Forestry University, Harbin 150040, China

² State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China

³ College of Materials and Energy, South China Agricultural University, Guangzhou 510642, China

Materials 2017, 10(9), 999; https://doi.org/10.3390/ma10090999 - 26 Aug 2017

Cited by 21 | Viewed by 5787

Abstract

Polylactide (PLA)/wood flour composite foam were prepared through a batch foaming process. The effect of the chain extender on the crystallization behavior and dynamic rheological properties of the PLA/wood flour composites were investigated as well as the crystal structure and cell morphology of [...] Read more.

Polylactide (PLA)/wood flour composite foam were prepared through a batch foaming process. The effect of the chain extender on the crystallization behavior and dynamic rheological properties of the PLA/wood flour composites were investigated as well as the crystal structure and cell morphology of the composite foams. The incorporation of the chain extender enhanced the complex viscosity and storage modulus of PLA/wood flour composites, indicating the improved melt elasticity. The chain extender also led to a decreased crystallization rate and final crystallinity of PLA/wood flour composites. With an increasing chain extender content, a finer and more uniform cell structure was formed, and the expansion ratio of PLA/wood flour composite foams was much higher than without the chain extender. Compared to the unfoamed composites, the crystallinity of the foamed PLA/wood flour composites was improved and the crystal was loosely packed. However, the new crystalline form was not evident. Full article

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10 pages, 3756 KiB

Open AccessArticle

The Effect of Heat Treatment on the Emission Color of P-Doped Ca₂SiO₄ Phosphor

by Hiromi Nakano^1,2,*, Konatsu Kamimoto², Nobuyuki Yokoyama² and Koichiro Fukuda³

¹ Cooperative Research Facility Center, Toyohashi University of Technology, Toyohashi 441-8580, Japan

² Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi 441-8580, Japan

³ Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan

Materials 2017, 10(9), 1000; https://doi.org/10.3390/ma10091000 - 26 Aug 2017

Cited by 7 | Viewed by 4578

Abstract

In a series of (Ca_2–x/2–yEu_y□_x_/2)(Si_1–xP_x)O₄ (x = 0.06, 0.02 ≤ y ≤0.5), various color-emitting phosphors were successfully synthesized by a solid-state reaction. These phosphors were characterized [...] Read more.

In a series of (Ca_2–x/2–yEu_y□_x_/2)(Si_1–xP_x)O₄ (x = 0.06, 0.02 ≤ y ≤0.5), various color-emitting phosphors were successfully synthesized by a solid-state reaction. These phosphors were characterized by photoluminescence (PL) spectroscopy, X-ray powder diffractometry, transmission electron microscopy, and X-ray absorption fine structure spectroscopy. We evaluated the effect of heat treatment on PL properties with various annealing temperatures at 1373–1773 K for 4 h before/after reduction treatment from Eu³⁺ to Eu²⁺. In the red-emitting (Ca_1.95Eu³⁺_0.02□_0.03)(Si_0.94P_0.06)O_4+δ phosphor, the highest PL intensity exhibited when it was annealed at 1773 K. On the other hand, in the green-emitting (Ca_1.95Eu²⁺_0.02□_0.03)(Si_0.94P_0.06)O₄ phosphor, the highest PL intensity was realized when it was annealed at 1473 K and consequently treated under a reductive atmosphere. With increasing annealing temperature, the emission peak wavelength steadily decreased. Furthermore, with increasing Eu²⁺ content, the emission peak wavelength increased, with the color of emitting light becoming yellowish. Thus, the PL properties of the phosphors were affected by both the structural change from β to α’_L, which occurred by heat treatment, and the amount of doped Eu ions. Full article

(This article belongs to the Special Issue Luminescent Materials 2017)

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13 pages, 5074 KiB

Open AccessArticle

Enhanced Azo-Dyes Degradation Performance of Fe-Si-B-P Nanoporous Architecture

by Nan Weng¹, Feng Wang¹, Fengxiang Qin^1,*, Wanying Tang^2,* and Zhenhua Dan^3,*

¹ School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

² School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

³ College of Materials Science and Engineering, Nanjing TECH University, Nanjing 210009, China

Materials 2017, 10(9), 1001; https://doi.org/10.3390/ma10091001 - 27 Aug 2017

Cited by 27 | Viewed by 4847

Abstract

Nanoporous structures were fabricated from Fe₇₆Si₉B₁₀P₅ amorphous alloy annealed at 773 K by dealloying in 0.05 M H₂SO₄ solution, as a result of preferential dissolution of α-Fe grains in form of the micro-coupling [...] Read more.

Nanoporous structures were fabricated from Fe₇₆Si₉B₁₀P₅ amorphous alloy annealed at 773 K by dealloying in 0.05 M H₂SO₄ solution, as a result of preferential dissolution of α-Fe grains in form of the micro-coupling cells between α-Fe and cathodic residual phases. Nanoporous Fe-Si-B-P powders exhibit much better degradation performance to methyl orange and direct blue azo dyes compared with gas-atomized Fe₇₆Si₉B₁₀P₅ amorphous powders and commercial Fe powders. The degradation reaction rate constants of nanoporous powders are almost one order higher than those of the amorphous counterpart powders and Fe powders, accompanying with lower activation energies of 19.5 and 26.8 kJ mol⁻¹ for the degradation reactions of methyl orange and direct blue azo dyes, respectively. The large surface area of the nanoporous structure, and the existence of metalloids as well as residual amorphous phase with high catalytic activity are responsible for the enhanced azo-dyes degradation performance of the nanoporous Fe-Si-B-P powders. Full article

(This article belongs to the Section Porous Materials)

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18 pages, 5583 KiB

Open AccessArticle

Rapid Removal of Zinc(II) from Aqueous Solutions Using a Mesoporous Activated Carbon Prepared from Agricultural Waste

by Xiaotao Zhang^1,2,†

, Yinan Hao^2,†, Ximing Wang^2,* and Zhangjing Chen³

¹ College of Science, Inner Mongolia Agricultural University, Hohhot 010018, China

² College of Material Science and Art Design, Inner Mongolia Agricultural University, Hohhot 010018, China

³ Department of Sustainable Biomaterials Virginia Tech University, Blacksburg, VA 24061, USA

^† Contributed equally to this paper.

Materials 2017, 10(9), 1002; https://doi.org/10.3390/ma10091002 - 28 Aug 2017

Cited by 35 | Viewed by 5493

Abstract

A low-cost activated carbon (XSBLAC) prepared from Xanthoceras Sorbifolia Bunge hull via chemical activation was investigated to determine its adsorption and desorption properties for zinc(II) ions from aqueous solutions. XSBLAC was characterized based on its N₂-adsorption/desorption isotherm, EDX, XRD, SEM and [...] Read more.

A low-cost activated carbon (XSBLAC) prepared from Xanthoceras Sorbifolia Bunge hull via chemical activation was investigated to determine its adsorption and desorption properties for zinc(II) ions from aqueous solutions. XSBLAC was characterized based on its N₂-adsorption/desorption isotherm, EDX, XRD, SEM and FTIR results. An adsorption study was conducted in a series of experiments to optimize the process variables for zinc(II) removal using XSBLAC. Modeling the adsorption kinetics indicated good agreement between the experimental data and the pseudo-second-order kinetic model. The Langmuir equilibrium isotherm fit the experimental data reasonably well. The calculated enthalpy (ΔH⁰), entropy (ΔS⁰) and Gibbs free energy (ΔG⁰) values revealed the endothermic and spontaneous nature of the adsorption process. HNO₃ displayed the best desorption performance. The adsorption mechanism was investigated in detail through FTIR and SEM/EDX spectroscopic analyses. The results suggested that XSBLAC is a potential biosorbent for removing zinc(II) from aqueous solutions. Full article

(This article belongs to the Section Biomaterials)

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10 pages, 1925 KiB

Open AccessArticle

Analytical Model of Nonlinear Stress-Strain Relation for a Strand Made of Two Materials

by Keunhee Cho^*

, Sung Tae Kim, Jeong-Rae Cho and Young-Hwan Park

Structural Engineering Research Institute, Korea Institute of Civil Engineering and Building Technology, 283, Goyangdae-Ro, Ilsanseo-Gu, Goyang-Si, Gyeonggi-Do 10223, Korea

Materials 2017, 10(9), 1003; https://doi.org/10.3390/ma10091003 - 28 Aug 2017

Cited by 5 | Viewed by 3861

Abstract

Unlike conventional steel strands, the smart strand supports strain-measuring function and adopts different materials for its core wire and helical wires. This study intends to analytically derive the nonlinear stress-strain model of this strand made of two materials. The effect of the bending [...] Read more.

Unlike conventional steel strands, the smart strand supports strain-measuring function and adopts different materials for its core wire and helical wires. This study intends to analytically derive the nonlinear stress-strain model of this strand made of two materials. The effect of the bending moment and torsional moment of the helical wires on the overall load within the range of geometric shapes shown by actually used strands is verified to be negligible and is thus ignored in order to simplify the analytical model. Moreover, the slight difference between the actual and analytic behaviors, which only appears in the slope varying part in the case of bilinear behavior, such as that of steel, is also ignored. The proposed constitutive model of the smart strand obtained by introducing the experimental stress-strain relation between the carbon fiber reinforced polymer core wire and the helical steel wires is in good agreement with the experimental data. The previous analytical models are applicable only to strands made of a unique linear material, whereas the model proposed in this study is also applicable to strands in which the core wire and the helical wires are made of two different materials, exhibiting nonlinear behavior. Full article

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9 pages, 6098 KiB

Open AccessArticle

The Preparation of Ag Nanoparticle and Ink Used for Inkjet Printing of Paper Based Conductive Patterns

by Lin Cao, Xiaohe Bai, Zhidan Lin^*

, Peng Zhang^*

, Shuling Deng, Xusheng Du and Wei Li

Institute of Advanced Wear & Corrosion Resistant and Functional Materials, Jinan University, Guangzhou 510632, China

Materials 2017, 10(9), 1004; https://doi.org/10.3390/ma10091004 - 28 Aug 2017

Cited by 36 | Viewed by 6871

Abstract

Ag nanoparticles were successfully prepared using a liquid reduction method with a suitable mixture reductant of polyethylene glycol (PEG) and ethylene glycol (EG). OP-10 as a dispersing agent, was used to prepare the conductive Ag ink. Ag nanoparticles with an average particle size [...] Read more.

Ag nanoparticles were successfully prepared using a liquid reduction method with a suitable mixture reductant of polyethylene glycol (PEG) and ethylene glycol (EG). OP-10 as a dispersing agent, was used to prepare the conductive Ag ink. Ag nanoparticles with an average particle size of 40 nm were prepared while the ratio of PEG to EG was 1:2. Meanwhile, the Ag particles had a narrow size distribution and great dispersion performance. The effects of paper substrates, sintering temperature, and sintering time on the conductivity of the printed Ag ink pattern were also studied. It was found that Lucky porous high glossy photo paper was a good candidate as the printing substrate. The resistivity of the printed pattern could reach 5.1 × 10⁻³ Ω·cm after heated at 100 °C for 2 h. Hence, the printed pattern showed good conductivity which led to the LED light being on. Furthermore, the Ag nanoparticle ink could be printed to form any pattern as required that still showed good electrical conductivity after being sintered under low-temperature. This could provide new possibilities for the preparation of flexible electrodes. Full article

(This article belongs to the Section Energy Materials)

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15 pages, 4018 KiB

Open AccessArticle

Numerical Simulation of Droplets Behavior of Cu-Pb Immiscible Alloys Solidifying under Magnetic Field

by Lin Zhang^*, Tiannan Man, Minghao Huang, Jianwen Gao, Xiaowei Zuo

and Engang Wang^*

Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, China

Materials 2017, 10(9), 1005; https://doi.org/10.3390/ma10091005 - 28 Aug 2017

Cited by 8 | Viewed by 3407

Abstract

A model has been presented for the coarsening of the dispersed phase of liquid-liquid two-phase mixtures in Cu-Pb alloys under the effect of a high magnetic field (HMF). The numerical results show that the evolution of size distribution is the result of several [...] Read more.

A model has been presented for the coarsening of the dispersed phase of liquid-liquid two-phase mixtures in Cu-Pb alloys under the effect of a high magnetic field (HMF). The numerical results show that the evolution of size distribution is the result of several factors and the diffusional growth, the collision-coagulation of the Cu-rich droplets (gravity sedimentation and Marangoni migration), and melt flow also have obvious effects on the movement of droplets and coarsening process. The effect of the HMF in the coarsening process of Cu-Pb alloy is studied in this work both by simulation and experiment. The analysis shows that the HMF leads to a decrease in the melt flow velocity, and can also lead to a decrease in the moving velocity of Cu-rich droplets. The HMF significantly reduces the coarsening rate of droplets as compared by the distribution evolutions. Finally, it is shown that droplet collision and coagulation can be dramatically retarded by the HMF. The results of the simulation are compared with the experiments performed with immiscible Cu-Pb alloys, and the discrepancy between theory and experiment is discussed. Full article

(This article belongs to the Section Advanced Materials Characterization)

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12 pages, 1725 KiB

Open AccessArticle

Characterization and Applications of Kaolinite Robustly Grafted by an Ionic Liquid with Naphthyl Functionality

by Gustave Kenne Dedzo^1,2,*

and Christian Detellier¹

¹ Center for Catalysis Research and Innovation and Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada

² Laboratory of Analytical Chemistry, Faculty of Science, University of Yaoundé I, Yaoundé B.P. 812, Cameroon

Materials 2017, 10(9), 1006; https://doi.org/10.3390/ma10091006 - 29 Aug 2017

Cited by 13 | Viewed by 4183

Abstract

Functionalization of the kaolinite (K) interlayer space is challenging. In this work, a new kaolinite-based nanohybridmaterial (K-NI) was successfully synthesized by grafting on the interlayer aluminol surfaces the ionic liquid, 1-(1-methylnaphthyl)-3-(2-hydroxyethyl) imidazolium chloride (NI), using a guest displacement strategy. A substantial increase of [...] Read more.

Functionalization of the kaolinite (K) interlayer space is challenging. In this work, a new kaolinite-based nanohybridmaterial (K-NI) was successfully synthesized by grafting on the interlayer aluminol surfaces the ionic liquid, 1-(1-methylnaphthyl)-3-(2-hydroxyethyl) imidazolium chloride (NI), using a guest displacement strategy. A substantial increase of the basal spacing (10.8 Å) was obtained. This is a grafted derivative of kaolinite possessing one of the largest d-values. Washing in water for several days and other vigorous treatments such as sonication showed a minor effect on the integrity of the material. FTIR and ¹³C NMR confirmed the conservation of the structure of the ionic liquid after the grafting. Thermal analysis confirmed the presence of grafted material and was used to estimate the abundance of the grafted ionic liquid (0.44 mole per mole of kaolinite structural formula, (Al₂Si₂O₅(OH)₄)). By using cyclic voltammetry, the permeability of a film of K-NI for the bulky ferricyanide ions was demonstrated. The accumulation of nitrophenolate anions was effective (maximum capacity of 190 μmol/g), but was less important than what was expected due to the steric hindrance of the bulky grafted NI. Although the presence of chloride anions reduced the adsorption capacity, the affinity of the modified kaolinite interlayer space for the nitrophenolate anions was demonstrated. Full article

(This article belongs to the Special Issue Ionic Liquids: New Materials for Sensors and Catalysis)

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8 pages, 3827 KiB

Open AccessArticle

Formation Mechanism of Spherical TiC in Ni-Ti-C System during Combustion Synthesis

by Guoliang Zhu^1,2, Wei Wang^1,2, Rui Wang^1,2, Chuanbao Zhao^1,2, Weitao Pan², Haijun Huang^1,2, Dafan Du^1,2, Donghong Wang^1,2, Da Shu^1,2,*, Anping Dong^1,2,*, Baode Sun^1,2,3,4, Sheng Jiang⁵ and Yilong Pu⁵

¹ Shanghai Key Lab of Advanced High-Temperature Materials and Precision Forming, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China

² School of Materials Science and Engineering, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China

³ State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China

⁴ Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China

⁵ Jiangsu Longda Superalloy Material Co., Ltd, Wuxi 214105, China

Materials 2017, 10(9), 1007; https://doi.org/10.3390/ma10091007 - 29 Aug 2017

Cited by 23 | Viewed by 4840

Abstract

The formation mechanism of TiC particles in a Ni-Ti-C system were revealed by using differential thermal analysis (DTA), XRD, and SEM to identify the reaction products in different temperature ranges. The results indicated that the synthesis mechanism of TiC in Ni-Ti-C system was [...] Read more.

The formation mechanism of TiC particles in a Ni-Ti-C system were revealed by using differential thermal analysis (DTA), XRD, and SEM to identify the reaction products in different temperature ranges. The results indicated that the synthesis mechanism of TiC in Ni-Ti-C system was complex; several reactions were involved in the combustion synthesis of TiC-Ni composite. The Ni-Ti intermediate phases play important roles during the formation of TiC. Moreover, the influence of heating rate on the size range of TiC was also discussed. Full article

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

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26 pages, 1866 KiB

Open AccessFeature PaperReview

On the Use of PLA-PHB Blends for Sustainable Food Packaging Applications

by Marina Patricia Arrieta^1,*, María Dolores Samper², Miguel Aldas^2,3

and Juan López²

¹ Institute of Polymer Science and Technology (ICTP-CSIC), Juan de la Cierva 3, 28006 Madrid, Spain

² Instituto de Tecnología de Materiales, Universitat Politècnica de València, 03801 Alcoy-Alicante, Spain

³ Departamento de Ciencia de Alimentos y Biotecnología, Facultad de Ingeniería Química y Agroindustria, Escuela Politécnica Nacional, Quito 170517, Ecuador

Materials 2017, 10(9), 1008; https://doi.org/10.3390/ma10091008 - 29 Aug 2017

Cited by 336 | Viewed by 22594

Abstract

Poly(lactic acid) (PLA) is the most used biopolymer for food packaging applications. Several strategies have been made to improve PLA properties for extending its applications in the packaging field. Melt blending approaches are gaining considerable interest since they are easy, cost-effective and readily [...] Read more.

Poly(lactic acid) (PLA) is the most used biopolymer for food packaging applications. Several strategies have been made to improve PLA properties for extending its applications in the packaging field. Melt blending approaches are gaining considerable interest since they are easy, cost-effective and readily available processing technologies at the industrial level. With a similar melting temperature and high crystallinity, poly(hydroxybutyrate) (PHB) represents a good candidate to blend with PLA. The ability of PHB to act as a nucleating agent for PLA improves its mechanical resistance and barrier performance. With the dual objective to improve PLAPHB processing performance and to obtain stretchable materials, plasticizers are frequently added. Current trends to enhance PLA-PHB miscibility are focused on the development of composite and nanocomposites. PLA-PHB blends are also interesting for the controlled release of active compounds in the development of active packaging systems. This review explains the most relevant processing aspects of PLA-PHB based blends such as the influence of polymers molecular weight, the PLA-PHB composition as well as the thermal stability. It also summarizes the recent developments in PLA-PHB formulations with an emphasis on their performance with interest in the sustainable food packaging field. PLA-PHB blends shows highly promising perspectives for the replacement of traditional petrochemical based polymers currently used for food packaging. Full article

(This article belongs to the Special Issue Biobased Polymers for Packaging Applications)

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18 pages, 1379 KiB

Open AccessArticle

How Stress Treatments Influence the Performance of Biodegradable Poly(Butylene Succinate)-Based Copolymers with Thioether Linkages for Food Packaging Applications

by Valentina Siracusa^1,*

, Laura Genovese²

, Andrea Munari²

and Nadia Lotti²

¹ Department of Chemical Science, University of Catania, Viale A. Doria 6, 95125 Catania (CT), Italy

² Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali, Università di Bologna, Via Terracini 28, 40131 Bologna, Italy

Materials 2017, 10(9), 1009; https://doi.org/10.3390/ma10091009 - 30 Aug 2017

Cited by 8 | Viewed by 5140

Abstract

Biodegradable poly(butylene succinate) (PBS)-based random copolymers containing thioether linkages (P(BSxTDGSy)) of various compositions have been investigated and characterized from the gas barrier, thermal, and mechanical point of view, after food contact simulants or thermal and photoaging processes. Each stress treatment was performed on [...] Read more.

Biodegradable poly(butylene succinate) (PBS)-based random copolymers containing thioether linkages (P(BSxTDGSy)) of various compositions have been investigated and characterized from the gas barrier, thermal, and mechanical point of view, after food contact simulants or thermal and photoaging processes. Each stress treatment was performed on thin films and the results obtained have been compared to the same untreated film, used as a standard. Barrier properties with different gases (O₂ and CO₂) were evaluated, showing that the polymer chemical composition strongly influenced the permeability behavior. The relationships between the diffusion coefficients (D) and solubility (S) with polymer composition were also investigated. The results highlighted a correlation between polymer chemical structure and treatment. Gas transmission rate (GTR) mainly depending on the performed treatment, as GTR increased with the increase of TDGS co-unit amount. Thermal and mechanical tests allowed for the recording of variations in the degree of crystallinity and in the tensile properties. An increase in the crystallinity degree was recorded after contact with simulant liquids and aging treatments, together with a molecular weight decrease, a slight enhancement of the elastic modulus and a decrement of the elongation at break, proportional to the TDGS co-unit content. Full article

(This article belongs to the Special Issue Biobased Polymers for Packaging Applications)

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13 pages, 5301 KiB

Open AccessArticle

Application of Dynamic Analysis in Semi-Analytical Finite Element Method

by Pengfei Liu¹

, Qinyan Xing²

, Dawei Wang^1,3,*

and Markus Oeser¹

¹ Institute of Highway Engineering, RWTH Aachen University, Mies-van-der-Rohe-Street 1, D52074 Aachen, Germany

² Department of Civil Engineering, Tsinghua University, Beijing 100084, China

³ Institute of Highway Engineering, Paul-Bonatz-Street 9–11, University of Siegen, D57076 Siegen, Germany

Materials 2017, 10(9), 1010; https://doi.org/10.3390/ma10091010 - 30 Aug 2017

Cited by 32 | Viewed by 6011

Abstract

Analyses of dynamic responses are significantly important for the design, maintenance and rehabilitation of asphalt pavement. In order to evaluate the dynamic responses of asphalt pavement under moving loads, a specific computational program, SAFEM, was developed based on a semi-analytical finite element method. [...] Read more.

Analyses of dynamic responses are significantly important for the design, maintenance and rehabilitation of asphalt pavement. In order to evaluate the dynamic responses of asphalt pavement under moving loads, a specific computational program, SAFEM, was developed based on a semi-analytical finite element method. This method is three-dimensional and only requires a two-dimensional FE discretization by incorporating Fourier series in the third dimension. In this paper, the algorithm to apply the dynamic analysis to SAFEM was introduced in detail. Asphalt pavement models under moving loads were built in the SAFEM and commercial finite element software ABAQUS to verify the accuracy and efficiency of the SAFEM. The verification shows that the computational accuracy of SAFEM is high enough and its computational time is much shorter than ABAQUS. Moreover, experimental verification was carried out and the prediction derived from SAFEM is consistent with the measurement. Therefore, the SAFEM is feasible to reliably predict the dynamic response of asphalt pavement under moving loads, thus proving beneficial to road administration in assessing the pavement’s state. Full article

(This article belongs to the Special Issue Theory, Experiment and Modelling of the Dynamic Response of Materials)

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12 pages, 4052 KiB

Open AccessReview

Evaluating the Tensile Properties of Aluminum Foundry Alloys through Reference Castings—A Review

by A.R. Anilchandra^1,*, Lars Arnberg², Franco Bonollo³, Elena Fiorese³ and Giulio Timelli³

¹ Department of Mechanical Engineering, BMS College of Engineering, Bengaluru 560019, India

² Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway

³ Department of Management and Engineering (DTG), University of Padova, Stradella S. Nicola, 3 I-36100 Vicenza, Italy

Materials 2017, 10(9), 1011; https://doi.org/10.3390/ma10091011 - 30 Aug 2017

Cited by 18 | Viewed by 9349

Abstract

The tensile properties of an alloy can be exploited if detrimental defects and imperfections of the casting are minimized and the microstructural characteristics are optimized through several strategies that involve die design, process management and metal treatments. This paper presents an analysis and [...] Read more.

The tensile properties of an alloy can be exploited if detrimental defects and imperfections of the casting are minimized and the microstructural characteristics are optimized through several strategies that involve die design, process management and metal treatments. This paper presents an analysis and comparison of the salient characteristics of the reference dies proposed in the literature, both in the field of pressure and gravity die-casting. The specimens produced with these reference dies, called separately poured specimens, are effective tools for the evaluation and comparison of the tensile and physical behaviors of Al-Si casting alloys. Some of the findings of the present paper have been recently developed in the frame of the European StaCast project whose results are complemented here with some more recent outcomes and a comprehensive analysis and discussion. Full article

(This article belongs to the Special Issue Welding, Joining and Casting of Advanced Materials)

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8 pages, 12377 KiB

Open AccessArticle

Effect of Coiling Temperature on Microstructure, Properties and Resistance to Fish-Scaling of Hot Rolled Enamel Steel

by Yang Zhao^1,*, Xueqi Huang^1,2, Bo Yu³, Xiaoyun Yuan⁴ and Xianghua Liu³

¹ School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China

² Shougang Research Institute of Technology, Beijing 100043, China

³ State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China

⁴ College of Mechanical and Electrical Engineering, Xi’an Polytechnic University, Xi’an 710048, China

Materials 2017, 10(9), 1012; https://doi.org/10.3390/ma10091012 - 31 Aug 2017

Cited by 18 | Viewed by 4495

Abstract

The microstructure, mechanical properties, and hydrogen permeation behavior of hot rolled enamel steel were investigated. Three coiling temperatures were adopted to gain different sizes of ferrite grain and TiC precipitates. The results show that a large number of interphase precipitates of nano-sized TiC [...] Read more.

The microstructure, mechanical properties, and hydrogen permeation behavior of hot rolled enamel steel were investigated. Three coiling temperatures were adopted to gain different sizes of ferrite grain and TiC precipitates. The results show that a large number of interphase precipitates of nano-sized TiC can be obtained at coiling temperatures of 650 and 700 °C, while a few precipitates are found in experimental steel when coiling temperature is 600 °C. The yield strength and ultimate tensile strength decrease with increasing coiling temperature, while elongation increases. The experimental steel has the best resistance to fish-scaling at coiling temperature of 700 °C, due to the large quantities of nano-sized interphase precipitates of TiC. Full article

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30 pages, 882 KiB

Open AccessReview

A Review of Recent Advances towards the Development of (Quantitative) Structure-Activity Relationships for Metallic Nanomaterials

by Guangchao Chen^1,*

, Martina G. Vijver¹

, Yinlong Xiao¹ and Willie J.G.M. Peijnenburg^1,2

¹ Institute of Environmental Sciences, Leiden University, 2300 RA Leiden, The Netherlands

² Centre for Safety of Substances and Products, National Institute of Public Health and the Environment (RIVM), 3720 BA Bilthoven, The Netherlands

Materials 2017, 10(9), 1013; https://doi.org/10.3390/ma10091013 - 31 Aug 2017

Cited by 24 | Viewed by 5215

Abstract

Gathering required information in a fast and inexpensive way is essential for assessing the risks of engineered nanomaterials (ENMs). The extension of conventional (quantitative) structure-activity relationships ((Q)SARs) approach to nanotoxicology, i.e., nano-(Q)SARs, is a possible solution. The preliminary attempts of correlating ENMs’ characteristics [...] Read more.

Gathering required information in a fast and inexpensive way is essential for assessing the risks of engineered nanomaterials (ENMs). The extension of conventional (quantitative) structure-activity relationships ((Q)SARs) approach to nanotoxicology, i.e., nano-(Q)SARs, is a possible solution. The preliminary attempts of correlating ENMs’ characteristics to the biological effects elicited by ENMs highlighted the potential applicability of (Q)SARs in the nanotoxicity field. This review discusses the current knowledge on the development of nano-(Q)SARs for metallic ENMs, on the aspects of data sources, reported nano-(Q)SARs, and mechanistic interpretation. An outlook is given on the further development of this frontier. As concluded, the used experimental data mainly concern the uptake of ENMs by different cell lines and the toxicity of ENMs to cells lines and Escherichia coli. The widely applied techniques of deriving models are linear and non-linear regressions, support vector machine, artificial neural network, k-nearest neighbors, etc. Concluded from the descriptors, surface properties of ENMs are seen as vital for the cellular uptake of ENMs; the capability of releasing ions and surface redox properties of ENMs are of importance for evaluating nanotoxicity. This review aims to present key advances in relevant nano-modeling studies and stimulate future research efforts in this quickly developing field of research. Full article

(This article belongs to the Special Issue Environmental Impact of Nanomaterials)

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21 pages, 4865 KiB

Open AccessArticle

Force Transmission Modes of Non-Cohesive and Cohesive Materials at the Critical State

by Ji-Peng Wang

Building Architecture and Town Planning Department (BATir), Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, CP 194/2, 1050 Brussels, Belgium

Materials 2017, 10(9), 1014; https://doi.org/10.3390/ma10091014 - 31 Aug 2017

Cited by 9 | Viewed by 5211

Abstract

This paper investigates the force transmission modes, mainly described by probability density distributions, in non-cohesive dry and cohesive wet granular materials by discrete element modeling. The critical state force transmission patterns are focused on with the contact model effect being analyzed. By shearing [...] Read more.

This paper investigates the force transmission modes, mainly described by probability density distributions, in non-cohesive dry and cohesive wet granular materials by discrete element modeling. The critical state force transmission patterns are focused on with the contact model effect being analyzed. By shearing relatively dense and loose dry specimens to the critical state in the conventional triaxial loading path, it is observed that there is a unique critical state force transmission mode. There is a universe critical state force distribution pattern for both the normal contact forces and tangential contact forces. Furthermore, it is found that using either the linear Hooke or the non-linear Hertz model does not affect the universe force transmission mode, and it is only related to the grain size distribution. Wet granular materials are also simulated by incorporating a water bridge model. Dense and loose wet granular materials are tested, and the critical state behavior for the wet material is also observed. The critical state strength and void ratio of wet granular materials are higher than those of a non-cohesive material. The critical state inter-particle distribution is altered from that of a non-cohesive material with higher probability in relatively weak forces. Grains in non-cohesive materials are under compressive stresses, and their principal directions are mainly in the axial loading direction. However, for cohesive wet granular materials, some particles are in tension, and the tensile stresses are in the horizontal direction on which the confinement is applied. The additional confinement by the tensile stress explains the macro strength and dilatancy increase in wet samples. Full article

(This article belongs to the Special Issue Granular Materials)

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21 pages, 6871 KiB

Open AccessArticle

Research on the Mechanism of In-Plane Vibration on Friction Reduction

by Peng Wang¹, Hongjian Ni^1,*, Ruihe Wang², Weili Liu² and Shuangfang Lu¹

¹ Research Institute of Unconventional Oil & Gas and Renewable Energy, China University of Petroleum (East China), Qingdao 266580, China

² School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China

Materials 2017, 10(9), 1015; https://doi.org/10.3390/ma10091015 - 1 Sep 2017

Cited by 17 | Viewed by 4757

Abstract

A modified model for predicting the friction force between drill-string and borehole wall under in-plane vibrations was developed. It was found that the frictional coefficient in sliding direction decreased significantly after applying in-plane vibration on the bottom specimen. The friction reduction is due [...] Read more.

A modified model for predicting the friction force between drill-string and borehole wall under in-plane vibrations was developed. It was found that the frictional coefficient in sliding direction decreased significantly after applying in-plane vibration on the bottom specimen. The friction reduction is due to the direction change of friction force, elastic deformation of surface asperities and the change of frictional coefficient. Normal load, surface topography, vibration direction, velocity ratio and interfacial shear factor are the main influence factors of friction force in sliding direction. Lower driving force can be realized for a pair of determinate rubbing surfaces under constant normal load by setting the driving direction along the minimum arithmetic average attack angle direction, and applying intense longitudinal vibration on the rubbing pair. The modified model can significantly improve the accuracy in predicting frictional coefficient under vibrating conditions, especially under the condition of lower velocity ratio. The results provide a theoretical gist for friction reduction technology by vibrating drill-string, and provide a reference for determination of frictional coefficient during petroleum drilling process, which has great significance for realizing digitized and intelligent drilling. Full article

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10 pages, 5395 KiB

Open AccessArticle

In situ Observation of Phase Transformation in MnAl(C) Magnetic Materials

by Ping-Zhan Si^1,2,*, Hui-Dong Qian¹

, Chul-Jin Choi^1,*, Jihoon Park¹

, Sangho Han¹, Hong-Liang Ge² and Kiran P. Shinde¹

¹ Powder & Ceramic Division, Korea Institute of Materials Science, Changwon, Gyeongnam 51508, Korea

² College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China

Materials 2017, 10(9), 1016; https://doi.org/10.3390/ma10091016 - 31 Aug 2017

Cited by 28 | Viewed by 5944

Abstract

The phase transformation in two modes, including both displacive and massive growth of τ-phase from ε-MnAl(C), was observed by in situ transmission electron microscopy. The exact temperature range for different phase transformation modes was determined by magnetic measurements. The displacive growth of ε→τ [...] Read more.

The phase transformation in two modes, including both displacive and massive growth of τ-phase from ε-MnAl(C), was observed by in situ transmission electron microscopy. The exact temperature range for different phase transformation modes was determined by magnetic measurements. The displacive growth of ε→τ in Mn₅₄Al₄₆ (or Mn₅₄Al₄₆C_2.44) occurs at temperatures below 650 K (or 766 K), above which both modes coexist. One-third or less of the ε-phase can be transformed into τ-phase via displacive mode while the remaining two-thirds or more via massive mode. In bulk τ-phase, most τ-nanocrystals formed via displacive mode are distributed in the matrix of large τ-grains that formed via massive mode. The typical massive growth rate of the τ-phase is 8–60 nm/s, while the displacive growth rate is low. A more complete understanding of the ε→τ phase transformations in the MnAl-based magnets was provided in this work, based on which the annealing process for ε→τ was optimized and thus high purity τ-phase with high saturation magnetization was obtained. Full article

(This article belongs to the Section Advanced Materials Characterization)

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11 pages, 5239 KiB

Open AccessArticle

The Effect of Precipitate Evolution on Austenite Grain Growth in RAFM Steel

by Biyu Yan¹, Yongchang Liu^1,2, Zejun Wang³, Chenxi Liu^1,*, Yonghong Si³, Huijun Li¹ and Jianxing Yu^1,2

¹ State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science & Engineering, Tianjin University, Tianjin 300350, China

² Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai Jiao Tong University, Shanghai 200240, China

³ Tianjin Special Equipment Inspection Institute, Tianjin 300192, China

Materials 2017, 10(9), 1017; https://doi.org/10.3390/ma10091017 - 1 Sep 2017

Cited by 36 | Viewed by 7242

Abstract

To study the effects of various types of precipitates and precipitate evolution behavior on austenite (size and phase fraction) in reduced activation ferritic/martensitic (RAFM) steel, RAFM steel was heated to various austenitizing temperatures. The microstructures of specimens were observed using optical microscopy (OM) [...] Read more.

To study the effects of various types of precipitates and precipitate evolution behavior on austenite (size and phase fraction) in reduced activation ferritic/martensitic (RAFM) steel, RAFM steel was heated to various austenitizing temperatures. The microstructures of specimens were observed using optical microscopy (OM) and transmission electron microscopy (TEM). The results indicate that the M₂₃C₆ and MX precipitates gradually coarsen and dissolve into the matrix as the austenitizing temperatures increase. The M₂₃C₆ precipitates dissolve completely at 1100 °C, while the MX precipitates dissolve completely at 1200 °C. The evolution of two types of precipitate has a significant effect on the size of austenite. Based on the Zener pinning model, the effect of precipitate evolution on austenite grain size is quantified. It was found that the coarsening and dissolution of M₂₃C₆ and MX precipitates leads to a decrease in pinning pressure on grain boundaries, facilitating the rapid growth of austenite grains. The austenite phase fraction is also affected by the coarsening and dissolution of precipitates. Full article

(This article belongs to the Special Issue Energetic Materials and Processes)

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19 pages, 23925 KiB

Open AccessArticle

The Efficacy of Electron Beam Irradiated Bacterial Cellulose Membranes as Compared with Collagen Membranes on Guided Bone Regeneration in Peri-Implant Bone Defects

by So-Hyoun Lee^1,†, Sung-Jun An^2,†, Youn-Mook Lim² and Jung-Bo Huh^1,*

¹ Department of Prosthodontics, Dental Research Institute, Institute of Translational Dental Sciences, BK21 PLUS Project, School of Dentistry, Pusan National University, Yangsan 50612, Korea

² Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, 1266 Sinjeong-dong, Jeongeup-si, Jeollabuk-do 56212, Korea

^† These authors contributed equally to this work.

Materials 2017, 10(9), 1018; https://doi.org/10.3390/ma10091018 - 1 Sep 2017

Cited by 30 | Viewed by 8423

Abstract

Bacterial cellulose (BC) is a natural polysaccharide produced by some bacteria, and consists of a linear polymer linked by β-(1,4) glycosidic bonds. BC has been developed as a material for tissue regeneration purposes. This study was conducted to evaluate the efficacy of resorbable [...] Read more.

Bacterial cellulose (BC) is a natural polysaccharide produced by some bacteria, and consists of a linear polymer linked by β-(1,4) glycosidic bonds. BC has been developed as a material for tissue regeneration purposes. This study was conducted to evaluate the efficacy of resorbable electron beam irradiated BC membranes (EI-BCMs) for guided bone regeneration (GBR). The electron beam irradiation (EI) was introduced to control the biodegradability of BC for dental applications. EI-BCMs had higher porosity than collagen membranes (CMs), and had similar wet tensile strengths to CMs. NIH3T3 cell adhesion and proliferation on EI-BCMs were not significantly different from those on CMs (p > 0.05). Micro-computed tomography (μCT) and histometric analysis in peri-implant dehiscence defects of beagle dogs showed that EI-BCMs were non-significantly different from CMs in terms of new bone area (NBA; %), remaining bone substitute volume (RBA; %) and bone-to-implant contact (BIC; %) (p > 0.05). These results suggest resorbable EI-BCMs can be used as an alternative biomaterial for bone tissue regeneration. Full article

(This article belongs to the Special Issue Dental Biomaterials 2017)

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14 pages, 447 KiB

Open AccessArticle

Quantifying the Performance of P-Type Transparent Conducting Oxides by Experimental Methods

by Karsten Fleischer^*

, Emma Norton

, Daragh Mullarkey, David Caffrey and Igor V. Shvets

School of Physics, Trinity College, The University of Dublin, D02PD91 Dublin 2, Ireland

Materials 2017, 10(9), 1019; https://doi.org/10.3390/ma10091019 - 1 Sep 2017

Cited by 59 | Viewed by 9184

Abstract

Screening for potential new materials with experimental and theoretical methods has led to the discovery of many promising candidate materials for p-type transparent conducting oxides. It is difficult to reliably assess a good p-type transparent conducting oxide (TCO) from limited information available at [...] Read more.

Screening for potential new materials with experimental and theoretical methods has led to the discovery of many promising candidate materials for p-type transparent conducting oxides. It is difficult to reliably assess a good p-type transparent conducting oxide (TCO) from limited information available at an early experimental stage. In this paper we discuss the influence of sample thickness on simple transmission measurements and how the sample thickness can skew the commonly used figure of merit of TCOs and their estimated band gap. We discuss this using copper-deficient CuCrO

_{2}

as an example, as it was already shown to be a good p-type TCO grown at low temperatures. We outline a modified figure of merit reducing thickness-dependent errors, as well as how modern ab initio screening methods can be used to augment experimental methods to assess new materials for potential applications as p-type TCOs, p-channel transparent thin film transistors, and selective contacts in solar cells. Full article

(This article belongs to the Special Issue Advances in Transparent Conducting Materials)

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14 pages, 4324 KiB

Open AccessFeature PaperArticle

Sol-Gel Derived Active Material for Yb Thin-Disk Lasers

by Rui M. Almeida^*, Tiago Ribeiro and Luís F. Santos^*

Centro de Química Estrutural/DEQ, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

Materials 2017, 10(9), 1020; https://doi.org/10.3390/ma10091020 - 2 Sep 2017

Cited by 2 | Viewed by 4546

Abstract

A ytterbium doped active material for thin-disk laser was developed based on aluminosilicate and phosphosilicate glass matrices containing up to 30 mol% YbO_1.5. Thick films and bulk samples were prepared by sol-gel processing. The structural nature of the base material was [...] Read more.

A ytterbium doped active material for thin-disk laser was developed based on aluminosilicate and phosphosilicate glass matrices containing up to 30 mol% YbO_1.5. Thick films and bulk samples were prepared by sol-gel processing. The structural nature of the base material was assessed by X-ray diffraction and Raman spectroscopy and the film morphology was evidenced by scanning electron microscopy. The photoluminescence (PL) properties of different compositions, including emission spectra and lifetimes, were also studied. Er³⁺ was used as an internal reference to compare the intensities of the Yb³⁺ PL peaks at ~ 1020 nm. The Yb³⁺ PL lifetimes were found to vary between 1.0 and 0.5 ms when the Yb concentration increased from 3 to 30 mol%. Based on a figure of merit, the best active material selected was the aluminosilicate glass composition 71 SiO₂-14 AlO_1.5-15 YbO_1.5 (in mol%). An active disk, ~ 36 μm thick, consisting of a Bragg mirror, an aluminosilicate layer doped with 15 mol% Yb and an anti-reflective coating, was fabricated. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry Applied to Materials Science)

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8 pages, 2369 KiB

Open AccessArticle

Photoswitchable Fluorescent Diarylethene Derivatives with Thiophene 1,1-Dioxide Groups: Effect of Alkyl Substituents at the Reactive Carbons

by Masakazu Morimoto^*

, Takaki Sumi and Masahiro Irie^*

Department of Chemistry and Research Center for Smart Molecules, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan

Materials 2017, 10(9), 1021; https://doi.org/10.3390/ma10091021 - 2 Sep 2017

Cited by 15 | Viewed by 5327

Abstract

Photoswitching and fluorescent properties of sulfone derivatives of 1,2-bis(2-alkyl-4-methyl-5-phenyl-3-thienyl)perfluorocyclopentene, 1–5, having methyl, ethyl, n-propyl, i-propyl, and i-butyl substituents at the reactive carbons (2- and 2′-positions) of the thiophene 1,1-dioxide rings were studied. Diarylethenes 1–5 underwent [...] Read more.

Photoswitching and fluorescent properties of sulfone derivatives of 1,2-bis(2-alkyl-4-methyl-5-phenyl-3-thienyl)perfluorocyclopentene, 1–5, having methyl, ethyl, n-propyl, i-propyl, and i-butyl substituents at the reactive carbons (2- and 2′-positions) of the thiophene 1,1-dioxide rings were studied. Diarylethenes 1–5 underwent isomerization reactions between open-ring and closed-ring forms upon alternate irradiation with ultraviolet (UV) and visible light and showed fluorescence in the closed-ring forms. The alkyl substitution at the reactive carbons affects the fluorescent property of the closed-ring isomers. The closed-ring isomers 2b–5b with ethyl, n-propyl, i-propyl, and i-butyl substituents show higher fluorescence quantum yields than 1b with methyl substituents. In polar solvents, the fluorescence quantum yield of 1b markedly decreases, while 2b–5b maintain the relatively high fluorescence quantum yields. Although the cycloreversion quantum yields of the derivatives with methyl, ethyl, n-propyl, and i-propyl substituents are quite low and in the order of 10⁻⁵, introduction of i-butyl substituents was found to increase the yield up to the order of 10⁻³. These results indicate that appropriate alkyl substitution at the reactive carbons is indispensable for properly controlling the photoswitching and fluorescent properties of the photoswitchable fluorescent diarylethenes, which are potentially applicable to super-resolution fluorescence microscopies. Full article

(This article belongs to the Special Issue Photoswitchable Materials)

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17 pages, 9769 KiB

Open AccessArticle

Relationship between Degree of Deformation in Quartz and Silica Dissolution for the Development of Alkali-Silica Reaction in Concrete

by Francieli Tiecher^1,*, Marcia E. B. Gomes², Denise C. C. Dal Molin³, Nicole P. Hasparyk⁴ and Paulo J. M. Monteiro⁵

¹ Polytechnic School of Civil Engineering, IMED, Passo Fundo 99070-220, Brazil

² Department of Geology, Universidade Federal do Rio Grande do Sul, Porto Alegre 91501-970, Brazil

³ Department of Civil Engineering, Universidade Federal do Rio Grande do Sul, Porto Alegre 90010-281, Brazil

⁴ Department of Services and Technological Innovation of FURNAS Centrais Elétricas S. A., Goiânia 74984-670, Brazil

⁵ Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720, USA

Materials 2017, 10(9), 1022; https://doi.org/10.3390/ma10091022 - 4 Sep 2017

Cited by 12 | Viewed by 4660

Abstract

This paper presents research on the influence of quartz deformation in aggregates for the development of the alkali-silica reaction in concrete and its relationship with silica dissolution. The study also compares these characteristics with the field behavior of such rocks in concrete. The [...] Read more.

This paper presents research on the influence of quartz deformation in aggregates for the development of the alkali-silica reaction in concrete and its relationship with silica dissolution. The study also compares these characteristics with the field behavior of such rocks in concrete. The paper proposes parameters to classify the different degrees of deformation of quartz. Transmission electron microscopy showed the presence of walls even in slightly deformed quartz, which indicate the presence of the internal paths available to react with the alkaline concrete pore solutions and point to the potential development of an alkali-silica reaction. The presence of the deformation bands in the quartz grains leads to the alkali aggregate reaction occurring more rapidly. The visible spectrophotometer test was performed to evaluate the dissolution potential of the different samples of deformed quartz, which confirmed that the reactivity of the quartz increases as the deformation of the crystalline structure increases. The parameters established in the present study could be verified by analyzing the behavior of reactive and innocuous aggregates from the buildings. Full article

(This article belongs to the Section Advanced Materials Characterization)

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12 pages, 2130 KiB

Open AccessArticle

The Application of a Novel Ceramic Liner Improves Bonding between Zirconia and Veneering Porcelain

by Hee-Sung Lee¹ and Tae-Yub Kwon^2,*

¹ Department of Dental Science, Graduate School, Kyungpook National University, 2-188-1 Samduk-dong, Jung-gu, Daegu 700-412, Korea

² Department of Dental Biomaterials, School of Dentistry and Institute for Biomaterials Research & Development, Kyungpook National University, 2-188-1 Samduk-dong, Jung-gu, Daegu 700-412, Korea

Materials 2017, 10(9), 1023; https://doi.org/10.3390/ma10091023 - 2 Sep 2017

Cited by 11 | Viewed by 5199

Abstract

The adhesion of porcelain to zirconia is a key factor in the success of bilayered restorations. In this study, the efficacy of a novel experimental liner (EL) containing zirconia for improved bonding between zirconia and veneering porcelain was tested. Four ELs containing various [...] Read more.

The adhesion of porcelain to zirconia is a key factor in the success of bilayered restorations. In this study, the efficacy of a novel experimental liner (EL) containing zirconia for improved bonding between zirconia and veneering porcelain was tested. Four ELs containing various concentrations (0, 3.0, 6.0, and 9.0 wt %) of zirconia were prepared. Testing determined the most effective EL (EL3 containing 3.0 wt % zirconia) in terms of shear bond strength value (n = 15). Three different bar-shaped zirconia/porcelain bilayer specimens were prepared for a three-point flexural strength (TPFS) test (n = 15): no-liner (NL), commercial liner (CL), and EL3. Specimens were tested for TPFS with the porcelain under tension and the maximum load was measured at the first sign of fracture. The strength data were analyzed using one-way ANOVA and Tukey’s test (α = 0.05) as well as Weibull distribution. When compared to NL, the CL application had no effect, while the EL3 application had a significant positive effect (p < 0.001) on the flexural strength. Weibull analysis also revealed the highest shape and scale parameters for group EL3. Within the limitations of this study, the novel ceramic liner containing 3.0 wt % zirconia (EL3) significantly enhanced the zirconia/porcelain interfacial bonding. Full article

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18 pages, 11559 KiB

Open AccessArticle

Multi-Scale Low-Entropy Method for Optimizing the Processing Parameters during Automated Fiber Placement

by Zhenyu Han, Shouzheng Sun, Hongya Fu and Yunzhong Fu^*

School of Mechatronics Engineering, Harbin Institute of Technology, No.92, Xidazhi Street, Harbin 150001, China

Materials 2017, 10(9), 1024; https://doi.org/10.3390/ma10091024 - 3 Sep 2017

Cited by 15 | Viewed by 6375

Abstract

Automated fiber placement (AFP) process includes a variety of energy forms and multi-scale effects. This contribution proposes a novel multi-scale low-entropy method aiming at optimizing processing parameters in an AFP process, where multi-scale effect, energy consumption, energy utilization efficiency and mechanical properties of [...] Read more.

Automated fiber placement (AFP) process includes a variety of energy forms and multi-scale effects. This contribution proposes a novel multi-scale low-entropy method aiming at optimizing processing parameters in an AFP process, where multi-scale effect, energy consumption, energy utilization efficiency and mechanical properties of micro-system could be taken into account synthetically. Taking a carbon fiber/epoxy prepreg as an example, mechanical properties of macro–meso–scale are obtained by Finite Element Method (FEM). A multi-scale energy transfer model is then established to input the macroscopic results into the microscopic system as its boundary condition, which can communicate with different scales. Furthermore, microscopic characteristics, mainly micro-scale adsorption energy, diffusion coefficient entropy–enthalpy values, are calculated under different processing parameters based on molecular dynamics method. Low-entropy region is then obtained in terms of the interrelation among entropy–enthalpy values, microscopic mechanical properties (interface adsorbability and matrix fluidity) and processing parameters to guarantee better fluidity, stronger adsorption, lower energy consumption and higher energy quality collaboratively. Finally, nine groups of experiments are carried out to verify the validity of the simulation results. The results show that the low-entropy optimization method can reduce void content effectively, and further improve the mechanical properties of laminates. Full article

(This article belongs to the Special Issue Modeling and Simulation of Advanced Composite Materials)

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13 pages, 2122 KiB

Open AccessFeature PaperArticle

Level of Theory and Solvent Effects on DASA Absorption Properties Prediction: Comparing TD-DFT, CASPT2 and NEVPT2

by Cristina García-Iriepa^1,*

and Marco Marazzi^2,3,*

¹ Laboratoire Modélisation et Simulation Multi Echelle, Université Paris-Est, MSME, UMR 8208 CNRS, UPEM, 5 bd Descartes, 77454 Marne-la-Vallée, France

² Théorie-Modélisation-Simulation, Université de Lorraine—Nancy, SRSMC Boulevard des Aiguillettes, 54506 Vandoeuvre-lès-Nancy, France

³ Théorie-Modélisation-Simulation, CNRS, SRSMC Boulevard des Aiguillettes, 54506 Vandoeuvre-lès-Nancy, France

Materials 2017, 10(9), 1025; https://doi.org/10.3390/ma10091025 - 3 Sep 2017

Cited by 24 | Viewed by 6924

Abstract

Donor–acceptor Stenhouse adducts (DASAs) are a very recent class of organic photoswitches that combine excellent properties, such as color and polarity change, a large structural modification, and excellent fatigue resistance. Despite their potential applications in different fields, very few studies have focused on [...] Read more.

Donor–acceptor Stenhouse adducts (DASAs) are a very recent class of organic photoswitches that combine excellent properties, such as color and polarity change, a large structural modification, and excellent fatigue resistance. Despite their potential applications in different fields, very few studies have focused on rationalizing their electronic structure properties. Here, by means of different state-of-the-art theoretical methods, including solvent and vibrational effects, we show that while time dependent-density functional theory (TD-DFT) can qualitatively describe DASAs’ excited states, multiconfigurational quantum chemistry methods along with dynamic electron correlation (CASPT2, NEVPT2) are required for a quantitative agreement with the experiment. This finding is reasoned based on the different charge transfer characteristics observed. Moreover, the TD-DFT computed two-photon absorption properties are reported and suggested to red-shift the absorption band, as required for biological applications. Full article

(This article belongs to the Special Issue Photoswitchable Materials)

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9 pages, 3806 KiB

Open AccessArticle

Eco-Friendly and Biodegradable Biopolymer Chitosan/Y₂O₃ Composite Materials in Flexible Organic Thin-Film Transistors

by Bo-Wei Du

, Shao-Ying Hu, Ranjodh Singh, Tsung-Tso Tsai, Ching-Chang Lin^* and Fu-Hsiang Ko^*

Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan

Materials 2017, 10(9), 1026; https://doi.org/10.3390/ma10091026 - 3 Sep 2017

Cited by 47 | Viewed by 7542

Abstract

The waste from semiconductor manufacturing processes causes serious pollution to the environment. In this work, a non-toxic material was developed under room temperature conditions for the fabrication of green electronics. Flexible organic thin-film transistors (OTFTs) on plastic substrates are increasingly in demand due [...] Read more.

The waste from semiconductor manufacturing processes causes serious pollution to the environment. In this work, a non-toxic material was developed under room temperature conditions for the fabrication of green electronics. Flexible organic thin-film transistors (OTFTs) on plastic substrates are increasingly in demand due to their high visible transmission and small size for use as displays and wearable devices. This work investigates and analyzes the structured formation of aqueous solutions of the non-toxic and biodegradable biopolymer, chitosan, blended with high-k-value, non-toxic, and biocompatible Y₂O₃ nanoparticles. Chitosan thin films blended with Y₂O₃ nanoparticles were adopted as the gate dielectric thin film in OTFTs, and an improvement in the dielectric properties and pinholes was observed. Meanwhile, the on/off current ratio was increased by 100 times, and a low leakage current was observed. In general, the blended chitosan/Y₂O₃ thin films used as the gate dielectric of OTFTs are non-toxic, environmentally friendly, and operate at low voltages. These OTFTs can be used on surfaces with different curvature radii because of their flexibility. Full article

(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)

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14 pages, 4790 KiB

Open AccessFeature PaperArticle

Design of Waveguide Bars for Transmitting a Pure Shear Horizontal Wave to Monitor High Temperature Components

by Jiuhong Jia, Qiyue Wang, Zuoyu Liao, Yun Tu^* and Shan-Tung Tu

Key Laboratory of Pressure Systems and Safety, Ministry of Education, East China University of Science and Technology, Shanghai 200237, China

Materials 2017, 10(9), 1027; https://doi.org/10.3390/ma10091027 - 4 Sep 2017

Cited by 16 | Viewed by 5335

Abstract

Guided wave technique could be a possible method for monitoring components working in high temperature above 350 °C. However, this would require the design of an appropriate waveguide bar to transmit the wave, so that its sensing part is not influenced by the [...] Read more.

Guided wave technique could be a possible method for monitoring components working in high temperature above 350 °C. However, this would require the design of an appropriate waveguide bar to transmit the wave, so that its sensing part is not influenced by the high temperature. In the present study, the shape of waveguide bars is designed based on the analysis of wave source characteristics. The critical frequency-width and frequency-thickness products of waveguide bars are analyzed theoretically and numerically to transmit the zeroth shear horizontal wave SH0* in bars. The results show that waveguide bars can cut off all the other wave modes when their frequency-thickness products are smaller than the critical value fd*, and frequency-width products are not smaller than the critical value fw*. Six waveguide bars are designed and fabricated based on the design criteria, and an experiment system is set up to check their work performance. The testing results indicate that the wave signals of the SH0* mode propagate clearly in waveguide bars, and cut off all the other modes when the frequency-thickness products and frequency-width products of the bars meet the design criteria. It is also demonstrated that the dependency of the experimental group velocity of each waveguide bar on frequency is in good agreement with the numerical result. High-temperature experiments also validate the reliability of the designed waveguide bars. Therefore, the critical frequency-thickness product and frequency-width product can be the basis for the design of the waveguide bars. Full article

(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)

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15 pages, 1669 KiB

Open AccessFeature PaperArticle

Poly(Neopentyl Glycol Furanoate): A Member of the Furan-Based Polyester Family with Smart Barrier Performances for Sustainable Food Packaging Applications

by Laura Genovese¹

, Nadia Lotti^1,*

, Valentina Siracusa²

and Andrea Munari¹

¹ Civil, Chemical, Environmental and Materials Engineering Department via Terracini 28, 40131 Bologna, Italy

² Department of Chemical Science, University of Catania, Viale A. Doria 6, 95125 Catania (CT), Italy

Materials 2017, 10(9), 1028; https://doi.org/10.3390/ma10091028 - 4 Sep 2017

Cited by 67 | Viewed by 7330

Abstract

In the last decade, there has been an increased interest from the food packaging industry toward the development and application of bioplastics, to contribute to the sustainable economy and to reduce the huge environmental problem afflicting the planet. In the present work, we [...] Read more.

In the last decade, there has been an increased interest from the food packaging industry toward the development and application of bioplastics, to contribute to the sustainable economy and to reduce the huge environmental problem afflicting the planet. In the present work, we focus on a new furan-based polyester, poly(neopentyl glycol 2,5-furanoate) (PNF) to be used for sustainable food packaging applications. The aromatic polyester was successfully synthesized with high molecular weight, through a solvent-free process, starting directly from 2,5-furandicarboxylic acid. PNF was revealed to be a material with good thermal stability, characterized by a higher T_g and T_m and a lower RAF fraction compared to poly(propylene 2,5-furanoate) (PPF), ascribable to the two methyl side groups present in PNF glycol-sub-unit. PNF’s mechanical characteristics, i.e., very high elastic modulus and brittle fracture, were found to be similar to those of PPF and PEF. Barrier properties to different gases, temperatures and relative humidity were evaluated. From the results obtained, PNF was showed to be a material with very smart barrier performances, significantly superior with respect to PEF’s ones. Lastly, PNF’s permeability behavior did not appreciably change after contact with food simulants, whereas it got worse with increasing RH, due to the polar nature of furan ring. Full article

(This article belongs to the Special Issue Biobased Polymers for Packaging Applications)

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11 pages, 2239 KiB

Open AccessArticle

Magnetic Abrasive Machining of Difficult-to-Cut Materials for Ultra-High-Speed Machining of AISI 304 Bars

by Rui Wang

, Pyo Lim, Lida Heng and Sang Don Mun^*

Division of Mechanical Design Engineering, Chonbuk National University, 664-14, Duckjin-gu, Jeonju 561-756, Korea

Materials 2017, 10(9), 1029; https://doi.org/10.3390/ma10091029 - 4 Sep 2017

Cited by 12 | Viewed by 4580

Abstract

This research proposes an optimized magnetic abrasive machining process that uses an ultra-high-speed system to perform precision machining on a workpiece. The system can process several microns of material, either for machining surface roughness or for machining a workpiece for a precise micro-diameter. [...] Read more.

This research proposes an optimized magnetic abrasive machining process that uses an ultra-high-speed system to perform precision machining on a workpiece. The system can process several microns of material, either for machining surface roughness or for machining a workpiece for a precise micro-diameter. The stainless steel workpieces have been machined using an ultra-high-speed magnetic abrasive machining (UHSMAM) process. The experiments were performed analyzing the accuracy of the machined workpiece diameter, using response surface methodology. The results obtained after machining have been analyzed to determine the effect of different process parameters such as machining speed, machining time, machining frequencies, inert gas in/out, magnetic pole types, and magnetic abrasive mesh size for the individual workpiece, as well as to study various interaction effects that may significantly affect the machining performance of the process. The obtained outcomes of the analysis for different workpieces have been critically compared to understand the effect of the considered process parameters based on the resulting mechanical properties. Regression analysis was used to confirm the stability of the micro-diameter and the processing efficiency. Atomic force microscope (AFM) micrographs were also obtained to study the surface morphology of the precision-machined workpiece. Full article

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

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9 pages, 2344 KiB

Open AccessArticle

Nitrogen-Doped Carbon Nanoparticles for Oxygen Reduction Prepared via a Crushing Method Involving a High Shear Mixer

by Lei Shi^1,†, Tao Wu^1,†, Yiqing Wang^1,†, Jie Zhang¹, Gang Wang^1,2,3, Jinli Zhang¹, Bin Dai¹ and Feng Yu^1,2,3,*

¹ Key Laboratory for Green Processing of Chemical Engineering of Xinjiang Bingtuan, School of Chemistry and Chemical Engineering, Shihezi University, Shihezi 832003, China

² Key Laboratory of Materials-Oriented Chemical Engineering of Xinjiang Uygur Autonomous Region, Shihezi 832003, China

³ Key Laboratory of Xinjiang Phytomedicine Resources of Ministry of Education, School of Pharmacy, Shihezi University, Shihezi 832002, China

^† Authors contributed equally to this work.

Materials 2017, 10(9), 1030; https://doi.org/10.3390/ma10091030 - 4 Sep 2017

Cited by 18 | Viewed by 6274

Abstract

The disposal of agricultural wastes such as fresh banana peels (BPs) is an environmental issue. In this work, fresh BPs were successfully transformed into nitrogen-doped carbon nanoparticles (N-CNPs) by using a high shear mixer facilitated crushing method (HSM-FCM) followed by carbonization under Ar [...] Read more.

The disposal of agricultural wastes such as fresh banana peels (BPs) is an environmental issue. In this work, fresh BPs were successfully transformed into nitrogen-doped carbon nanoparticles (N-CNPs) by using a high shear mixer facilitated crushing method (HSM-FCM) followed by carbonization under Ar atmosphere. Ammonia-activated N-CNPs (N-CNPs-NH₃) were prepared via subsequent ammonia activation treatments at a high temperature. The as-prepared N-CNPs and N-CNPs-NH₃ materials both exhibited high surface areas (above 700 m²/g) and mean particle size of 50 nm. N-CNPs-NH₃showed a relatively higher content of pyridinic and graphitic N compared to N-CNPs. In alkaline media, N-CNPs-NH₃ showed superior performances as an oxygen reduction reaction (ORR) catalyst (E₀ = −0.033 V, J = 2.4 mA/cm²) compared to N-CNPs (E₀ = 0.07 V, J = 1.8 mA/cm²). In addition, N-CNPs-NH₃ showed greater oxygen reduction stability and superior methanol crossover avoidance than a conventional Pt/C catalyst. This study provides a novel, simple, and scalable approach to valorize biomass wastes by synthesizing highly efficient electrochemical ORR catalysts. Full article

(This article belongs to the Special Issue Green Activated Carbons)

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12 pages, 8106 KiB

Open AccessArticle

Study of Gravity Effects on Titanium Laser Welding in the Vertical Position

by Baohua Chang¹

, Zhang Yuan¹, Haitao Pu¹, Haigang Li², Hao Cheng², Dong Du^1,* and Jiguo Shan^1,*

¹ State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China

² Aerospace Research Institute of Materials & Processing Technology, Beijing 100076, China

Materials 2017, 10(9), 1031; https://doi.org/10.3390/ma10091031 - 8 Sep 2017

Cited by 21 | Viewed by 7721

Abstract

To obtain satisfactory welds in positional laser beam welding, it is necessary to know how process parameters will influence the quality of welds in different welding positions. In this study, the titanium alloy Ti6Al4V sheets were laser welded in two vertical welding positions [...] Read more.

To obtain satisfactory welds in positional laser beam welding, it is necessary to know how process parameters will influence the quality of welds in different welding positions. In this study, the titanium alloy Ti6Al4V sheets were laser welded in two vertical welding positions (vertical up and vertical down), and the appearance, porosity, strength, and ductility of the laser joints were evaluated. Results show that undercuts of the vertical up welds were greater than that of vertical down welds, while the porosity contents were much higher in vertical down welds than that in vertical up welds. When welding with a higher heat input, the vertical up welding position resulted in poor weld profiles (undercuts and burn-through holes), whereas the vertical down welding position led to excessive porosity contents in welds. Both severe undercut and excessive porosity were detrimental to the tensile properties of the welds. Weld appearance was improved and porosity contents were reduced by using a lower heat input, achieving better weld quality. Therefore, it is suggested that process parameter settings with relatively high laser powers and welding speeds, which can result in lower heat inputs, are used when laser welding the Ti6Al4V titanium alloys vertically. Full article

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

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7 pages, 10784 KiB

Open AccessArticle

A Piezoresponse Force Microscopy Study of Ca_xBa_1−xNb₂O₆ Single Crystals

by Vladimir V. Shvartsman^1,*

, Danka Gobeljic¹, Jan Dec² and Doru C. Lupascu¹

¹ Institute for Materials Science and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141 Essen, Germany

² Institute of Materials Science, University of Silesia, 40-007 Katowice, Poland

Materials 2017, 10(9), 1032; https://doi.org/10.3390/ma10091032 - 5 Sep 2017

Cited by 4 | Viewed by 3526

Abstract

Polar structures of Ca_xBa_1−xNb₂O₆ (CBN100x) single crystals were investigated using piezoresponse force microscopy. Increasing Ca content results in decreasing domain size and enhancement of the polar disorder. For the composition with x = [...] Read more.

Polar structures of Ca_xBa_1−xNb₂O₆ (CBN100x) single crystals were investigated using piezoresponse force microscopy. Increasing Ca content results in decreasing domain size and enhancement of the polar disorder. For the composition with x = 0.32 the characteristic domain size is similar to that reported for relaxor Sr_0.61Ba_0.39Nb₂O₆ (SBN61). However, decay of an artificial macroscopic domain in CBN32 takes place below the macroscopic transition temperature, contrary to SBN61, where random fields stabilize it above the transition temperature. We can conclude that CBN with 0.26 ≤ x ≤ 0.32 does not display classical relaxor behavior and might be considered as a disordered ferroelectric. Full article

(This article belongs to the Special Issue Scanning Probe Microscopy of Ferroics)

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19 pages, 8007 KiB

Open AccessArticle

Electron Beam Welding of IN792 DS: Effects of Pass Speed and PWHT on Microstructure and Hardness

by Giuliano Angella¹, Giuseppe Barbieri²

, Riccardo Donnini¹

, Roberto Montanari^3,*

, Maria Richetta³ and Alessandra Varone³

¹ Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE), National Research Council of Italy (CNR), 20125 Milan, Italy

² ENEA, Department for Sustainability-Research Centre of Casaccia, Santa Maria di Galeria, 00123 Rome, Italy

³ Department of Industrial Engineering, University of Rome Tor Vergata, 00133 Rome, Italy

Materials 2017, 10(9), 1033; https://doi.org/10.3390/ma10091033 - 5 Sep 2017

Cited by 23 | Viewed by 9465

Abstract

Electron Beam (EB) welding has been used to realize seams on 2 mm-thick plates of directionally solidified (DS) IN792 superalloy. The first part of this work evidenced the importance of pre-heating the workpiece to avoid the formation of long cracks in the seam. [...] Read more.

Electron Beam (EB) welding has been used to realize seams on 2 mm-thick plates of directionally solidified (DS) IN792 superalloy. The first part of this work evidenced the importance of pre-heating the workpiece to avoid the formation of long cracks in the seam. The comparison of different pre-heating temperatures (PHT) and pass speeds (v) allowed the identification of optimal process parameters, namely PHT = 300 °C and v = 2.5 m/min. The microstructural features of the melted zone (MZ); the heat affected zone (HAZ), and base material (BM) were investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), electron back-scattered diffraction (EBSD), X-ray diffraction (XRD), and micro-hardness tests. In the as-welded condition; the structure of directionally oriented grains was completely lost in MZ. The γ’ phase in MZ consisted of small (20–40 nm) round shaped particles and its total amount depended on both PHT and welding pass speed, whereas in HAZ, it was the same BM. Even if the amount of γ’ phase in MZ was lower than that of the as-received material, the nanometric size of the particles induced an increase in hardness. EDS examinations did not show relevant composition changes in the γ’ and γ phases. Post-welding heat treatments (PWHT) at 700 and 750 °C for two hours were performed on the best samples. After PWHTs, the amount of the ordered phase increased, and the effect was more pronounced at 750 °C, while the size of γ’ particles in MZ remained almost the same. The hardness profiles measured across the joints showed an upward shift, but peak-valley height was a little lower, indicating more homogeneous features in the different zones. Full article

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7 pages, 3310 KiB

Open AccessArticle

Magnetic Force Microscopy of Nanostructured Co/Pt Multilayer Films with Perpendicular Magnetization

by O. L. Ermolaeva^1,*, N. S. Gusev¹, E. V. Skorohodov¹, Yu. V. Petrov², M. V. Sapozhnikov¹ and V. L. Mironov¹

¹ Institute for Physics of Microstructures RAS, GSP-105, 603950 Nizhny Novgorod, Russia

² Saint Petersburg State University, University Embankment, 7/9, 199034 St. Petersburg, Russia

Materials 2017, 10(9), 1034; https://doi.org/10.3390/ma10091034 - 5 Sep 2017

Cited by 13 | Viewed by 7552

Abstract

We present the results of magnetic force microscopy investigations of domain structures in multilayer [Co (0.5 nm)/Pt (1 nm)]₅ thin film structures (denoted hereafter as Co/Pt) modified by additional Co capping layers and by ion irradiation. It is demonstrated that a Co [...] Read more.

We present the results of magnetic force microscopy investigations of domain structures in multilayer [Co (0.5 nm)/Pt (1 nm)]₅ thin film structures (denoted hereafter as Co/Pt) modified by additional Co capping layers and by ion irradiation. It is demonstrated that a Co capping layer essentially changes the domain structure and decreases the threshold of magnetization reversal, due to the formation of noncollinear magnetization in Co/Pt. It is shown that local irradiation with a focused He⁺ ion beam enables the formation of regions with decreased easy-axis anisotropy (magnetic bubbles) that have the inverse magnetization direction in the demagnetized state of Co/Pt. The experimental results demonstrate that the magnetic bubbles can be switched using a probe of a magnetic force microscope. The possible application of these effects for the development of magnetic logic and data storage systems is discussed. Full article

(This article belongs to the Special Issue Scanning Probe Microscopy of Ferroics)

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11 pages, 4144 KiB

Open AccessArticle

Preparation of Humidity-Sensitive Poly(Ethylene Glycol) Inverse Opal Micropatterns Using Colloidal Lithography

by Bing Yu^1,2, Hailin Cong^1,2,*

, Zhen Yang¹, Shujing Yang¹, Yuezhong Wang¹, Feng Zhai¹ and Yifan Wang¹

¹ Institute of Biomedical Materials and Engineering, College of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, China

² Laboratory for New Fiber Materials and Modern Textile, Growing Base for State Key Laboratory, College of Materials Science and Engineering, Qingdao University, Qingdao 266071, China

Materials 2017, 10(9), 1035; https://doi.org/10.3390/ma10091035 - 5 Sep 2017

Cited by 15 | Viewed by 7501

Abstract

Humidity-sensitive poly(ethylene glycol) (PEG) inverse opals with micropatterns of 2 μm wide anti-swell-broken grooves were prepared using polystyrene (PS) colloidal crystals as templates and colloidal lithography. Monodisperse PS colloids were deposited in an ordered manner onto glass slides using a double-substrate vertical deposition [...] Read more.

Humidity-sensitive poly(ethylene glycol) (PEG) inverse opals with micropatterns of 2 μm wide anti-swell-broken grooves were prepared using polystyrene (PS) colloidal crystals as templates and colloidal lithography. Monodisperse PS colloids were deposited in an ordered manner onto glass slides using a double-substrate vertical deposition method to form colloidal crystal templates. Poly(ethylene glycol) diacrylate (PEGDA) with photoinitiator was infiltrated into the interspaces of the colloidal crystals and photo-crosslinked by UV irradiation through a photomask. After removal the PS templates and unexposed PEGDA by tetrahydrofuran (THF), PEG hydrogel micropatterns with three-dimensional ordered porous structures were obtained. The band gaps of the PS colloidal crystals and corresponding PEG hydrogel inverse opals were measured by UV-VIS reflection spectrometer, calculated by Bragg law and simulated by Band SOLVE. The obtained PEG hydrogel inverse opal micropatterns can be used as sensors for humidity sensing due to absorption and desorption of moisture in the band gap structures. The sensor had a very reliable performance after repeated humidity sensing, and could be mass produced facilely with very low cost. The photopatterned anti-swell-broken grooves play an important role in the reliability of the sensors. Full article

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30 pages, 3814 KiB

Open AccessReview

Copper Corrosion and Biocorrosion Events in Premise Plumbing

by Ignacio T. Vargas^1,2

, Diego A. Fischer¹, Marco A. Alsina¹, Juan P. Pavissich³

, Pablo A. Pastén^1,2 and Gonzalo E. Pizarro^1,2,*

¹ Departamento de Ingeniería Hidráulica y Ambiental, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile

² CEDEUS, Centro de Desarrollo Urbano Sustentable, Santiago 7820436, Chile

³ Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago 7941169, Chile

Materials 2017, 10(9), 1036; https://doi.org/10.3390/ma10091036 - 5 Sep 2017

Cited by 66 | Viewed by 14875

Abstract

Corrosion of copper pipes may release high amounts of copper into the water, exceeding the maximum concentration of copper for drinking water standards. Typically, the events with the highest release of copper into drinking water are related to the presence of biofilms. This [...] Read more.

Corrosion of copper pipes may release high amounts of copper into the water, exceeding the maximum concentration of copper for drinking water standards. Typically, the events with the highest release of copper into drinking water are related to the presence of biofilms. This article reviews this phenomenon, focusing on copper ingestion and its health impacts, the physicochemical mechanisms and the microbial involvement on copper release, the techniques used to describe and understand this phenomenon, and the hydrodynamic effects. A conceptual model is proposed and the mathematical models are reviewed. Full article

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17 pages, 5684 KiB

Open AccessFeature PaperReview

Metamaterial Waveguide Devices for Integrated Optics

by Tomohiro Amemiya^1,2,*

, Toru Kanazawa², Satoshi Yamasaki² and Shigehisa Arai^1,2

¹ Institute of Innovative Research (IIR), Tokyo Institute of Technology, Tokyo 152-8552, Japan

² Department of Electrical and Electronic Engineering, Tokyo Institute of Technology, Tokyo 152-8552, Japan

Materials 2017, 10(9), 1037; https://doi.org/10.3390/ma10091037 - 5 Sep 2017

Cited by 28 | Viewed by 7863

Abstract

We show the feasibility of controlling the magnetic permeability of optical semiconductor devices on InP-based photonic integration platforms. We have achieved the permeability control of GaInAsP/InP semiconductor waveguides by combining the waveguide with a metamaterial consisting of gate-controlled split ring resonators. The split-ring [...] Read more.

We show the feasibility of controlling the magnetic permeability of optical semiconductor devices on InP-based photonic integration platforms. We have achieved the permeability control of GaInAsP/InP semiconductor waveguides by combining the waveguide with a metamaterial consisting of gate-controlled split ring resonators. The split-ring resonators interact magnetically with light travelling in the waveguide and move the effective relative permeability of the waveguide away from 1 at optical frequencies. The variation in permeability can be controlled with the gate voltage. Using this variable-permeability waveguide, we have built an optical modulator consisting of a GaInAsP/InP Mach–Zehnder interferometer for use at an optical communication wavelength of 1.55 μm. The device changes the permeability of its waveguide arm with controlling gate voltage, thereby varying the refractive index of the arm to modulate the intensity of light. For the study of variable-permeability waveguide devices, we also propose a method of extracting separately the permittivity and permeability values of devices from the experimental data of light transmission. Adjusting the permeability of optical semiconductors to the needs of device designers will open the promising field of ‘permeability engineering’. Permeability engineering will facilitate the manipulation of light and the management of photons, thereby contributing to the development of novel devices with sophisticated functions for photonic integration. Full article

(This article belongs to the Special Issue Advance in Plasmonics and Metamaterials)

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11 pages, 17500 KiB

Open AccessArticle

Improving the Mechanical Properties of Cu-15Ni-8Sn Alloys by Addition of Titanium

by Chao Zhao¹, Weiwen Zhang^1,2,*, Zhi Wang^1,2

, Daoxi Li¹, Zongqiang Luo^1,2, Chao Yang^1,2 and Datong Zhang^1,2

¹ Guangdong Key Laboratory for Processing and Forming of Advanced Metallic Materials, South China University of Technology, Guangzhou 510640, China

² School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China

Materials 2017, 10(9), 1038; https://doi.org/10.3390/ma10091038 - 6 Sep 2017

Cited by 67 | Viewed by 6578

Abstract

The effect of Ti addition on the microstructure and mechanical properties of Cu-15Ni-8Sn alloys was investigated. Optical microscopy (OM), scanning electronic microscopy (SEM), and transmission electron microscopy (TEM) were used to determine grain size and distribution of the second phases in the alloys. [...] Read more.

The effect of Ti addition on the microstructure and mechanical properties of Cu-15Ni-8Sn alloys was investigated. Optical microscopy (OM), scanning electronic microscopy (SEM), and transmission electron microscopy (TEM) were used to determine grain size and distribution of the second phases in the alloys. The results indicate that the tensile properties of Cu-15Ni-8Sn alloys are improved significantly with Ti addition. Tensile elongation increased from 2.7% for the alloy without Ti to 17.9% for the alloy with 0.3% Ti, while tensile strength was maintained and even increased from 935 MPa to 1024 MPa. The improvement of the mechanical properties of Cu-15Ni-8Sn alloys by the addition of Ti is attributed to the grain refinement and suppression of discontinuous precipitation during heat treatment. Full article

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18 pages, 4916 KiB

Open AccessArticle

Compression Fracture of CFRP Laminates Containing Stress Intensifications

by Christian Leopold^1,*

, Martin Schütt², Wilfried V. Liebig³

, Timo Philipkowski¹, Jonas Kürten¹, Karl Schulte¹ and Bodo Fiedler¹

¹ Institute of Polymer and Composites, Hamburg University of Technology (TUHH), Denickestrasse 15, D-21073 Hamburg, Germany

² CompriseTec GmbH, Steinhöft 5, D-20459 Hamburg, Germany

³ Institute of Vehicle System Technology, Karlsruhe Institute of Technology (KIT), Rintheimer Querallee 2, D-76131 Karlsruhe, Germany

Materials 2017, 10(9), 1039; https://doi.org/10.3390/ma10091039 - 5 Sep 2017

Cited by 17 | Viewed by 8794

Abstract

For brittle fracture behaviour of carbon fibre reinforced plastics (CFRP) under compression, several approaches exist, which describe different mechanisms during failure, especially at stress intensifications. The failure process is not only initiated by the buckling fibres, but a shear driven fibre compressive failure [...] Read more.

For brittle fracture behaviour of carbon fibre reinforced plastics (CFRP) under compression, several approaches exist, which describe different mechanisms during failure, especially at stress intensifications. The failure process is not only initiated by the buckling fibres, but a shear driven fibre compressive failure beneficiaries or initiates the formation of fibres into a kink-band. Starting from this kink-band further damage can be detected, which leads to the final failure. The subject of this work is an experimental investigation on the influence of ply thickness and stacking sequence in quasi-isotropic CFRP laminates containing stress intensifications under compression loading. Different effects that influence the compression failure and the role the stacking sequence has on damage development and the resulting compressive strength are identified and discussed. The influence of stress intensifications is investigated in detail at a hole in open hole compression (OHC) tests. A proposed interrupted test approach allows identifying the mechanisms of damage initiation and propagation from the free edge of the hole by causing a distinct damage state and examine it at a precise instant of time during fracture process. Compression after impact (CAI) tests are executed in order to compare the OHC results to a different type of stress intensifications. Unnotched compression tests are carried out for comparison as a reference. With this approach, a more detailed description of the failure mechanisms during the sudden compression failure of CFRP is achieved. By microscopic examination of single plies from various specimens, the different effects that influence the compression failure are identified. First damage of fibres occurs always in 0°-ply. Fibre shear failure leads to local microbuckling and the formation and growth of a kink-band as final failure mechanisms. The formation of a kink-band and finally steady state kinking is shifted to higher compressive strains with decreasing ply thickness. Final failure mode in laminates with stress intensification depends on ply thickness. In thick or inner plies, damage initiates as shear failure and fibre buckling into the drilled hole. The kink-band orientation angle is changing with increasing strain. In outer or thin plies shear failure of single fibres is observed as first damage and the kink-band orientation angle is constant until final failure. Decreasing ply thickness increases the unnotched compressive strength. When stress intensifications are present, the position of the 0°-layer is critical for stability under compression and is thus more important than the ply thickness. Central 0°-layers show best results for OHC and CAI strength due to higher bending stiffness and better supporting effect of the adjacent layers. Full article

(This article belongs to the Special Issue The Brittle Failure of Different Materials)

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21 pages, 33372 KiB

Open AccessArticle

Effect of Silane Coupling Agent on Tribological Properties of Hemp Fiber-Reinforced Plant-Derived Polyamide 1010 Biomass Composites

by Yosuke Nishitani^1,*

, Tetsuto Kajiyama² and Toshiyuki Yamanaka³

¹ Department of Mechanical Engineering, Faculty of Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015, Japan

² Jonan Branch, Tokyo Metropolitan Industrial Technology Research Institute, 1-20-20, Minamikamata, Ota, Tokyo 144-0035, Japan

³ Tokyo Metropolitan Industrial Technology Research Institute, 2-4-10, Aomi, Kotoku, Tokyo 135-0064, Japan

Materials 2017, 10(9), 1040; https://doi.org/10.3390/ma10091040 - 5 Sep 2017

Cited by 50 | Viewed by 7545

Abstract

We have studied the effects of silane coupling agents used for the surface treatment of fiber on the tribological properties of hemp fiber (HF) reinforced plant-derived polyamide 1010 (PA1010) biomass composites. Hemp fibers were surface-treated by two surface treatment methods: (a) alkali treatment [...] Read more.

We have studied the effects of silane coupling agents used for the surface treatment of fiber on the tribological properties of hemp fiber (HF) reinforced plant-derived polyamide 1010 (PA1010) biomass composites. Hemp fibers were surface-treated by two surface treatment methods: (a) alkali treatment by sodium hydroxide solution and (b) surface treatment by silane coupling agents. Three types of silane coupling agents, namely aminosilane, epoxysilane and ureidosilane were used. These HF/PA1010 biomass composites were extruded using a twin extruder, and injection-molded. The mechanical and tribological properties were evaluated by the ring-on-plate type sliding wear test. It was found that tribological properties of HF/PA1010 biomass composites improved with the surface treatment by the silane coupling agent. This may be attributed to the change in the mode of friction and wear mechanism by the interfacial adhesion between fiber and matrix polymer according to the type of silane coupling agent used. In particular, the ureidosilane coupling agent showed the best improvement effect for the tribological properties of these biomass composites in this study. Full article

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13 pages, 5800 KiB

Open AccessArticle

Monitoring Ion Track Formation Using In Situ RBS/c, ToF-ERDA, and HR-PIXE

by Marko Karlušić^1,*, Stjepko Fazinić¹, Zdravko Siketić¹, Tonči Tadić¹, Donny Domagoj Cosic¹, Iva Božičević-Mihalić¹, Ivana Zamboni¹, Milko Jakšić¹ and Marika Schleberger²

¹ Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia

² Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg, Germany

Materials 2017, 10(9), 1041; https://doi.org/10.3390/ma10091041 - 6 Sep 2017

Cited by 9 | Viewed by 5038

Abstract

The aim of this work is to investigate the feasibility of ion beam analysis techniques for monitoring swift heavy ion track formation. First, the use of the in situ Rutherford backscattering spectrometry in channeling mode to observe damage build-up in quartz SiO₂ [...] Read more.

The aim of this work is to investigate the feasibility of ion beam analysis techniques for monitoring swift heavy ion track formation. First, the use of the in situ Rutherford backscattering spectrometry in channeling mode to observe damage build-up in quartz SiO₂ after MeV heavy ion irradiation is demonstrated. Second, new results of the in situ grazing incidence time-of-flight elastic recoil detection analysis used for monitoring the surface elemental composition during ion tracks formation in various materials are presented. Ion tracks were found on SrTiO₃, quartz SiO₂, a-SiO₂, and muscovite mica surfaces by atomic force microscopy, but in contrast to our previous studies on GaN and TiO₂, surface stoichiometry remained unchanged. Third, the usability of high resolution particle induced X-ray spectroscopy for observation of electronic dynamics during early stages of ion track formation is shown. Full article

(This article belongs to the Special Issue Ion Beam Analysis, Modification, and Irradiation of Materials)

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19 pages, 18441 KiB

Open AccessArticle

Biological Evaluation of Flexible Polyurethane/Poly l-Lactic Acid Composite Scaffold as a Potential Filler for Bone Regeneration

by Yuk Fai Lui^*

and Wing Yuk Ip^*

Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong, China

Materials 2017, 10(9), 1042; https://doi.org/10.3390/ma10091042 - 13 Sep 2017

Cited by 6 | Viewed by 6416

Abstract

Degradable bone graft substitute for large-volume bone defects is a continuously developing field in orthopedics. With the advance in biomaterial in past decades, a wide range of new materials has been investigated for their potential in this application. When compared to common biopolymers [...] Read more.

Degradable bone graft substitute for large-volume bone defects is a continuously developing field in orthopedics. With the advance in biomaterial in past decades, a wide range of new materials has been investigated for their potential in this application. When compared to common biopolymers within the field such as PLA or PCL, elastomers such as polyurethane offer some unique advantages in terms of flexibility. In cases of bone defect treatments, a flexible soft filler can help to establish an intimate contact with surrounding bones to provide a stable bone-material interface for cell proliferation and ingrowth of tissue. In this study, a porous filler based on segmented polyurethane incorporated with poly l-lactic acid was synthesized by a phase inverse salt leaching method. The filler was put through in vitro and in vivo tests to evaluate its potential in acting as a bone graft substitute for critical-sized bone defects. In vitro results indicated there was a major improvement in biological response, including cell attachment, proliferation and alkaline phosphatase expression for osteoblast-like cells when seeded on the composite material compared to unmodified polyurethane. In vivo evaluation on a critical-sized defect model of New Zealand White (NZW) rabbit indicated there was bone ingrowth along the defect area with the introduction of the new filler. A tight interface formed between bone and filler, with osteogenic cells proliferating on the surface. The result suggested polyurethane/poly l-lactic acid composite is a material with the potential to act as a bone graft substitute for orthopedics application. Full article

(This article belongs to the Special Issue Polymeric Materials for Medical Applications)

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12 pages, 2724 KiB

Open AccessArticle

Simplified Models for the Material Characterization of Cold-Formed RHS

by Carlos López-Colina^*

, Miguel A. Serrano

, Miguel Lozano, Fernando L. Gayarre and Jesús Suárez

Department of Construction and Manufacturing Engineering, University of Oviedo, Building 7, Campus of Gijón/Xixón, 33203 Asturias, Spain

Materials 2017, 10(9), 1043; https://doi.org/10.3390/ma10091043 - 6 Sep 2017

Cited by 8 | Viewed by 4286

Abstract

It is well known that the cold-forming process used to manufacture tubes causes an increase in both the yielding stress and the ultimate strength of the corner material in rectangular steel hollow sections. This may have a significant effect on the resistance of [...] Read more.

It is well known that the cold-forming process used to manufacture tubes causes an increase in both the yielding stress and the ultimate strength of the corner material in rectangular steel hollow sections. This may have a significant effect on the resistance of any structure built with those profiles. However, the mentioned material hardening can be difficult to take into account in the calculations for member design or to evaluate the connection resistance through the design formulation or when using numerical simulation models. As an attempt to face the above-mentioned problem, the present paper presents a comparison among simplified approaches that consider homogeneous material properties for the whole section. It has been carried out by comparing the results obtained from the finite element modelling of stub column tests in which the material properties based on the flat faces were considered for the whole profile. Full article

(This article belongs to the Section Advanced Materials Characterization)

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13 pages, 11081 KiB

Open AccessArticle

Composite Fibers from Recycled Plastics Using Melt Centrifugal Spinning

by Nicole E. Zander^*, Margaret Gillan and Daniel Sweetser

United States Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Aberdeen, MD 21005, USA

Materials 2017, 10(9), 1044; https://doi.org/10.3390/ma10091044 - 6 Sep 2017

Cited by 33 | Viewed by 9521

Abstract

New methods are being developed to enable the production of value-added materials from high-volume, low-cost feedstocks arising from domestic recycling streams. In this work, recycled bottle-grade polyethylene terephthalate, polystyrene, and polypropylene were spun into fibers from the melt using a centrifugal spinning technique. [...] Read more.

New methods are being developed to enable the production of value-added materials from high-volume, low-cost feedstocks arising from domestic recycling streams. In this work, recycled bottle-grade polyethylene terephthalate, polystyrene, and polypropylene were spun into fibers from the melt using a centrifugal spinning technique. Mono-component fibers and 50/50 blends of each polymer and a 33/33/33 blend of all three polymers were evaluated. Fiber morphology, chemistry, thermal, and mechanical properties were probed. Fiber diameters ranged from ca. 1 to over 12 µm, with polypropylene fibers having the smallest fiber diameters. Mono-component fibers were generally defect-free, while composite fibers containing polypropylene were beady. Fibers made from polyethylene terephthalate had the highest tensile strength, and the addition of polyethylene terephthalate to the other polymers improved the mechanical properties of the blends. Nano- and micro-fibers from both pure and mixed waste streams are expected to have applications in myriad areas such as ultra/micro-filtration, composites, and insulation. Full article

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10 pages, 11751 KiB

Open AccessArticle

Tribological Properties of AlSi12-Al₂O₃ Interpenetrating Composite Layers in Comparison with Unreinforced Matrix Alloy

by Anna Janina Dolata

Faculty of Materials Engineering and Metallurgy, Silesian University of Technology, Krasińskiego 8, 40-019 Katowice, Poland

Materials 2017, 10(9), 1045; https://doi.org/10.3390/ma10091045 - 6 Sep 2017

Cited by 23 | Viewed by 4622

Abstract

Alumina–Aluminum composites with interpenetrating network structures are a new class of advanced materials with potentially better properties than composites reinforced by particles or fibers. Local casting reinforcement was proposed to take into account problems with the machinability of this type of materials and [...] Read more.

Alumina–Aluminum composites with interpenetrating network structures are a new class of advanced materials with potentially better properties than composites reinforced by particles or fibers. Local casting reinforcement was proposed to take into account problems with the machinability of this type of materials and the shaping of the finished products. The centrifugal infiltration process fabricated composite castings in the form of locally reinforced shafts. The main objective of the research presented in this work was to compare the tribological properties (friction coefficient, wear resistance) of AlSi12/Al₂O₃ interpenetrating composite layers with unreinforced AlSi12 matrix areas. Profilometric tests enabled both quantitative and qualitative analyses of the wear trace that formed on investigated surfaces. It has been shown that interpenetrating composite layers are characterized by lower and more stable coefficients of friction (μ), as well as higher wear resistance than unreinforced matrix areas. At the present stage, the study confirmed that the tribological properties of the composite layers depend on the spatial structure of the ceramic reinforcement, and primarily the volume and size of alumina foam cells. Full article

(This article belongs to the Section Advanced Composites)

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26 pages, 17088 KiB

Open AccessReview

Metasurfaces Based on Phase-Change Material as a Reconfigurable Platform for Multifunctional Devices

by Niloufar Raeis-Hosseini¹ and Junsuk Rho^1,2,*

¹ Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea

² Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea

Materials 2017, 10(9), 1046; https://doi.org/10.3390/ma10091046 - 6 Sep 2017

Cited by 144 | Viewed by 18544

Abstract

Integration of phase-change materials (PCMs) into electrical/optical circuits has initiated extensive innovation for applications of metamaterials (MMs) including rewritable optical data storage, metasurfaces, and optoelectronic devices. PCMs have been studied deeply due to their reversible phase transition, high endurance, switching speed, and data [...] Read more.

Integration of phase-change materials (PCMs) into electrical/optical circuits has initiated extensive innovation for applications of metamaterials (MMs) including rewritable optical data storage, metasurfaces, and optoelectronic devices. PCMs have been studied deeply due to their reversible phase transition, high endurance, switching speed, and data retention. Germanium-antimony-tellurium (GST) is a PCM that has amorphous and crystalline phases with distinct properties, is bistable and nonvolatile, and undergoes a reliable and reproducible phase transition in response to an optical or electrical stimulus; GST may therefore have applications in tunable photonic devices and optoelectronic circuits. In this progress article, we outline recent studies of GST and discuss its advantages and possible applications in reconfigurable metadevices. We also discuss outlooks for integration of GST in active nanophotonic metadevices. Full article

(This article belongs to the Special Issue Advance in Plasmonics and Metamaterials)

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12 pages, 8354 KiB

Open AccessArticle

Effect of Mo on Microstructures and Wear Properties of In Situ Synthesized Ti(C,N)/Ni-Based Composite Coatings by Laser Cladding

by Fan Wu¹

, Tao Chen¹

, Haojun Wang¹ and Defu Liu^1,2,*

¹ College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China

² State Key Laboratory of High Performance Complex Manufacturing, Changsha 410083, China

Materials 2017, 10(9), 1047; https://doi.org/10.3390/ma10091047 - 6 Sep 2017

Cited by 37 | Viewed by 4813

Abstract

Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt [...] Read more.

Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt % Mo, 4 wt % Mo and 8 wt % Mo additions are studied comparatively. Results indicate that Ti(C,N) is formed by the in situ metallurgical reaction, the (Ti,Mo)(C,N) rim phase surrounding the Ti(C,N) ceramic particle is synthesized with the addition of Mo, and the increase of Mo content is beneficial to improve the wear properties of the cladding coatings. Because of the effect of Mo, the grains are remarkably refined and a unique core-rim structure that is uniformly dispersed in the matrix appears; meanwhile, the composite coatings with Mo addition exhibit high hardness and excellent wear resistance due to the comprehensive action of dispersion strengthening, fine grain strengthening and solid solution strengthening. Full article

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

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17 pages, 6289 KiB

Open AccessArticle

Study on Topology Optimization Design, Manufacturability, and Performance Evaluation of Ti-6Al-4V Porous Structures Fabricated by Selective Laser Melting (SLM)

by Yangli Xu, Dongyun Zhang^*, Yan Zhou, Weidong Wang and Xuanyang Cao

Institute for Laser Engineering, Beijing University of Technology, Pingleyuan No. 100, Chaoyang District, Beijing 100124, China

Materials 2017, 10(9), 1048; https://doi.org/10.3390/ma10091048 - 7 Sep 2017

Cited by 62 | Viewed by 8023

Abstract

The combination of topology optimization (TOP) and selective laser melting (SLM) provides the possibility of fabricating the complex, lightweight and high performance geometries overcoming the traditional manufacturing “bottleneck”. This paper evaluates the biomechanical properties of porous structures with porosity from 40% to 80% [...] Read more.

The combination of topology optimization (TOP) and selective laser melting (SLM) provides the possibility of fabricating the complex, lightweight and high performance geometries overcoming the traditional manufacturing “bottleneck”. This paper evaluates the biomechanical properties of porous structures with porosity from 40% to 80% and unit cell size from 2 to 8 mm, which are designed by TOP and manufactured by SLM. During manufacturability exploration, three typical structures including spiral structure, arched bridge structure and structures with thin walls and small holes are abstracted and investigated, analyzing their manufacturing limits and forming reason. The property tests show that dynamic elastic modulus and compressive strength of porous structures decreases with increases of porosity (constant unit cell size) or unit cell size (constant porosity). Based on the Gibson-Ashby model, three failure models are proposed to describe their compressive behavior, and the structural parameter λ is used to evaluate the stability of the porous structure. Finally, a numerical model for the correlation between porous structural parameters (unit cell size and porosity) and elastic modulus is established, which provides a theoretical reference for matching the elastic modulus of human bones from different age, gender and skeletal sites during innovative medical implant design and manufacturing. Full article

(This article belongs to the Section Porous Materials)

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13 pages, 7077 KiB

Open AccessArticle

Evaluation of the Healing Potential of Demineralized Dentin Matrix Fixed with Recombinant Human Bone Morphogenetic Protein-2 in Bone Grafts

by Sang-Yun Kim¹, Young-Kyun Kim^1,2,*, Yeoung-Hyun Park^2,3, Joo-Cheol Park^2,3

, Jeong-Kui Ku¹

, In-Woong Um⁴ and Ji-Yun Kim⁵

¹ Department of Oral and Maxillofacial Surgery, Section of Dentistry, Seoul National University Bundang Hospital, 82 Gumi-ro 173, 173beon-gil, Bundang-gu, Seongnam 13620, Korea

² Department of Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul 03080, Korea

³ Department of Oral Histology-Developmental Biology, School of Dentistry, Seoul National University, Seoul 03080, Korea

⁴ R&D Institute, Korea Tooth Bank, Seoul 06101, Korea

⁵ Department of Science Education, College of Education, Dankook University, Yongin 16890, Korea

Materials 2017, 10(9), 1049; https://doi.org/10.3390/ma10091049 - 7 Sep 2017

Cited by 49 | Viewed by 6700

Abstract

We aimed to evaluate the efficacy of demineralized dentin matrix (DDM) fixed with recombinant human bone morphogenetic protein-2 (rhBMP-2) through an experimental and a clinical study. Unilateral upper second and third premolars of eight beagles were extracted. A mucoperiosteal flap was elevated around [...] Read more.

We aimed to evaluate the efficacy of demineralized dentin matrix (DDM) fixed with recombinant human bone morphogenetic protein-2 (rhBMP-2) through an experimental and a clinical study. Unilateral upper second and third premolars of eight beagles were extracted. A mucoperiosteal flap was elevated around the extraction socket, and a bone defect was made using a surgical drill. Each DDM was fixed with rhBMP-2, and autogenous bone was grafted at the bone defect area with a collagenous membrane. The beagles were euthanized at two, four, eight, and 12 weeks after receiving the bone graft. Block specimens involving grafted bone and surrounding natural bone were extracted. A total of 23 patients who received bone grafts using human DDM fixed with rhBMP-2 (AutoBT BMP) with implant placements (36 implants; maxilla: 14, mandible: 22) were selected. The implant stability, marginal bone loss, and clinical outcome were evaluated. Three trephine cores were harvested fourmonths after bone grafting, and histologic examination was performed. In the histological evaluation performed four weeks after the bone graft, autogenous bone showed 52% new bone formation and DDM fixed with rhBMP-2 showed 33% new bone formation. Twelve weeks after the bone graft, autogenous bone showed 75% new bone formation and DDM fixed with rhBMP-2 showed 48% new bone formation. In the clinical study, favorable osseointegration was obtained in 35 out of 36 implant sites (one case of osseointegration failure). In all cases, severe complications were not observed. Histomorphometrically, new bone formation was observed in 14.98% of the cases. The residual DDM particles were 6.22%. AutoBT BMP provides good osteoinductive and osteoconductive potential and clinical efficacy. Full article

(This article belongs to the Special Issue Biocompatible Metals for Skeletal Fixation and Joint Replacement Devices)

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15 pages, 3249 KiB

Open AccessArticle

Improvement of Early Strength of Cement Mortar Containing Granulated Blast Furnace Slag Using Industrial Byproducts

by Jin-Hyoung Kim¹ and Han-Seung Lee^2,*

¹ Department of Architectural Engineering, Hanyang University, 68 Munam 1-ga, Dong Nam-gu, Cheonan-si 31065, Chungcheongnam-do, Korea

² Department of Architectural Engineering, Hanyang University, 55, Hanyangdaehak-ro, Sangrok-gu, Ansan-si 15588, Gyeonggi-do, Korea

Materials 2017, 10(9), 1050; https://doi.org/10.3390/ma10091050 - 7 Sep 2017

Cited by 18 | Viewed by 4620

Abstract

In the field of construction, securing the early strength of concrete (on the first and third days of aging) has been an important problem in deciding the mold release time (i.e., shortening the construction time period). Therefore, the problem of reduced compressive strength [...] Read more.

In the field of construction, securing the early strength of concrete (on the first and third days of aging) has been an important problem in deciding the mold release time (i.e., shortening the construction time period). Therefore, the problem of reduced compressive strength in the early aging stage caused by mixing granulated blast furnace slag (GBFS) with concrete must certainly be resolved. In this study, we conduct experiments to explore methods for generating a concrete that develops an early strength equivalent to that of 100% OPC. The objective of this study is the development of an early-strength accelerator (ESA) made from an industrial by-product, for a GBFS-mixed cement mortar. This study also analyzes the mechanism of the early-strength generation in the concrete to evaluate the influence of the burning temperature of ESA on the optimal compressive strength of the concrete. According to the results of the experiment, GBFS, whose ESA is burnt at 800 °C, shows an activation factor of 102.6–104.7% in comparison with 100% OPC on the first and third days during early aging, thereby meeting the target compressive strength. The results of the micro-analytic experiment are as follows: ESA showed a pH of strongly alkaline. In addition, it was found that the content of SO₃ was high in the chemical components, thus activating the hydration reaction of GBFS in the early age. This initial hydration reaction was thought to be due to the increase in the filling effect of the hydrate and the generation of C-S-H of the early age by the mass production of Ettringite. Full article

(This article belongs to the Section Advanced Materials Characterization)

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13 pages, 13571 KiB

Open AccessArticle

Magnetoelectric Force Microscopy on Antiferromagnetic 180^∘ Domains in Cr₂O₃

by Peggy Schoenherr^1,*,†

, L. Marcela Giraldo^1,†, Martin Lilienblum¹, Morgan Trassin¹

, Dennis Meier² and Manfred Fiebig¹

¹ Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 4, 8093 Zürich, Switzerland

² Department of Materials Science and Engineering, Norwegian University of Science and Technology, Sem Sælandsvei 12, 7034 Trondheim, Norway

^† These authors contributed equally to this work.

Materials 2017, 10(9), 1051; https://doi.org/10.3390/ma10091051 - 7 Sep 2017

Cited by 18 | Viewed by 7736

Abstract

Magnetoelectric force microscopy (MeFM) is characterized as methodical tool for the investigation of antiferromagnetic domain states, in particular of the 180

^{\circ}

variety. As reference compound for this investigation we use Cr

_{2}

O

_{3}

. Access to the antiferromagnetic order is provided [...] Read more.

Magnetoelectric force microscopy (MeFM) is characterized as methodical tool for the investigation of antiferromagnetic domain states, in particular of the 180

^{\circ}

variety. As reference compound for this investigation we use Cr

_{2}

O

_{3}

. Access to the antiferromagnetic order is provided by the linear magnetoelectric effect. We resolve the opposite antiferromagnetic 180

^{\circ}

domain states of Cr

_{2}

O

_{3}

and estimate the sensitivity of the MeFM approach, its inherent advantages in comparison to alternative techniques and its general feasibility for probing antiferromagnetic order. Full article

(This article belongs to the Special Issue Scanning Probe Microscopy of Ferroics)

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15 pages, 5437 KiB

Open AccessArticle

Release of VEGF from Dental Implant Improves Osteogenetic Process: Preliminary In Vitro Tests

by Barbara Zavan^1,2,*

, Letizia Ferroni¹, Chiara Gardin¹, Stefano Sivolella³, Adriano Piattelli⁴ and Eitan Mijiritsky⁵

¹ Department of Biomedical Sciences, University of Padova, via G. Colombo 3, 35100 Padova, Italy

² Maria Cecilia Hospital, GVM Care & Research, 48033 Cotignola, Ravenna, Italy

³ Department of Neurosciences, University of Padova, via Giustiniani 5, 35100 Padova, Italy

⁴ Department of Medical, Oral, and Biotechnological Sciences, University of Chieti-Pescara, via dei Vestini 31, 66100 Chieti, Italy

⁵ Department of Otolaryngology, Head and Neck and Maxillofacial Surgery, Sackler Faculty of Medicine, Tel-Aviv Sourasky Medical Center, Tel Aviv University, 6 Weitzman Street, 64239 Tel Aviv, Israel

Materials 2017, 10(9), 1052; https://doi.org/10.3390/ma10091052 - 8 Sep 2017

Cited by 22 | Viewed by 5308

Abstract

Introduction: During osseointegration process, the presence of an inflammatory event could negatively influence the proper osteogenetic ability of the implant surface. In order to reduce this possibility, an implementation of angiogenetic event through the release of Vascular Endothelial Growth Factor (VEGF) can be [...] Read more.

Introduction: During osseointegration process, the presence of an inflammatory event could negatively influence the proper osteogenetic ability of the implant surface. In order to reduce this possibility, an implementation of angiogenetic event through the release of Vascular Endothelial Growth Factor (VEGF) can be a tool as co-factor for osteoblastic differentiation. In this paper, novel dental implant surfaces enriched with VEGF have been tested. Material and methods: The ability of VEGF-enriched titanium implants to improve the osteogenetic properties of Mesenchymal stem cells (MSC), also in the presence of an inflammatory environment, have been in vitro tested. Molecular biology, morphological analyses, and biochemical tests have been performed in order to confirm biological properties of these surfaces. Results: Our results confirm that the presence of VEGF onto the implant surface is able not only to protect the cells from in vitro aging and from Reactive Oxygen Species (ROS) damage, but it also improves their osteogenic and endothelial differentiation, even in the presence of inflammatory cytokines. Conclusion: This study establishes a biologically powerful novel tool that could enhance bone repair in dental implant integration. Full article

(This article belongs to the Special Issue Dental Implant Materials)

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17 pages, 16662 KiB

Open AccessArticle

Effect of Multi-Pass Friction Stir Processing on Mechanical Properties for AA2024/Al₂O₃ Nanocomposites

by Essam Moustafa

Mechanical Engineering Department, Faculty of Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia

Materials 2017, 10(9), 1053; https://doi.org/10.3390/ma10091053 - 8 Sep 2017

Cited by 86 | Viewed by 7332

Abstract

In the present work, an aluminum metal matrix reinforced with (Al₂O₃) nanoparticles was fabricated as a surface composite sheet using friction stir processing (FSP). The effects of processing parameters on mechanical properties, hardness, and microstructure grain were investigated. The [...] Read more.

In the present work, an aluminum metal matrix reinforced with (Al₂O₃) nanoparticles was fabricated as a surface composite sheet using friction stir processing (FSP). The effects of processing parameters on mechanical properties, hardness, and microstructure grain were investigated. The results revealed that multi-pass FSP causes a homogeneous distribution and good dispersion of Al₂O₃ in the metal matrix, and consequently an increase in the hardness of the matrix composites. A finer grain is observed in the microstructure examination in specimens subjected to second and third passes of FSP. The improvement in the grain refinement is 80% compared to base metal. The processing parameters, particularly rotational tool speed and pass number in FSP, have a major effect on strength properties and surface hardness. The ultimate tensile strength (UTS) and the average hardness are improved by 25% and 46%, respectively, due to presence of reinforcement Al₂O₃ nanoparticles. Full article

(This article belongs to the Special Issue Improving Performance of Nanocomposite Materials)

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15 pages, 4242 KiB

Open AccessArticle

Porcine Bone Scaffolds Adsorb Growth Factors Secreted by MSCs and Improve Bone Tissue Repair

by Eitan Mijiritsky¹, Letizia Ferroni², Chiara Gardin², Eriberto Bressan³, Gastone Zanette³, Adriano Piattelli⁴ and Barbara Zavan^2,5,*

¹ Department of Otolaryngology, Head and Neck and Maxillofacial Surgery, Sackler Faculty of Medicine, Tel-Aviv Sourasky Medical Center, Tel Aviv University, 6 Weitzman Street, 64239 Tel Aviv, Israel

² Department of Biomedical Sciences, University of Padova, via G. Colombo 3, 35100 Padova, Italy

³ Department of Neurosciences, University of Padova, via Giustiniani 5, 35100 Padova, Italy

⁴ Department of Medical, Oral, and Biotechnological Sciences, University of Chieti-Pescara, via dei Vestini 31, 66100 Chieti, Italy

⁵ Maria Cecilia Hospital, GVM & Research, Cotignola, 48033 Ravenna, Italy

Materials 2017, 10(9), 1054; https://doi.org/10.3390/ma10091054 - 8 Sep 2017

Cited by 16 | Viewed by 5851

Abstract

An ideal tissue-engineered bone graft should have both excellent pro-osteogenesis and pro-angiogenesis properties to rapidly realize the bone regeneration in vivo. To meet this goal, in this work a porcine bone scaffold was successfully used as a Trojan horse to store growth factors [...] Read more.

An ideal tissue-engineered bone graft should have both excellent pro-osteogenesis and pro-angiogenesis properties to rapidly realize the bone regeneration in vivo. To meet this goal, in this work a porcine bone scaffold was successfully used as a Trojan horse to store growth factors produced by mesenchymal stem cells (MSCs). This new scaffold showed a time-dependent release of bioactive growth factors, such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), in vitro. The biological effect of the growth factors-adsorbed scaffold on the in vitro commitment of MSCs into osteogenic and endothelial cell phenotypes has been evaluated. In addition, we have investigated the activity of growth factor-impregnated granules in the repair of critical-size defects in rat calvaria by means of histological, immunohistochemical, and molecular biology analyses. Based on the results of our work bone tissue formation and markers for bone and vascularization were significantly increased by the growth factor-enriched bone granules after implantation. This suggests that the controlled release of active growth factors from porcine bone granules can enhance and promote bone regeneration. Full article

(This article belongs to the Special Issue Dental Implant Materials)

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15 pages, 11766 KiB

Open AccessArticle

Research on High Layer Thickness Fabricated of 316L by Selective Laser Melting

by Shuo Wang

, Yude Liu^*, Wentian Shi, Bin Qi, Jin Yang, Feifei Zhang, Dong Han and Yingyi Ma

School of Material and Mechanical Engineering, Beijing Technology and Business University, Beijing 100048, China

Materials 2017, 10(9), 1055; https://doi.org/10.3390/ma10091055 - 8 Sep 2017

Cited by 65 | Viewed by 7853

Abstract

Selective laser melting (SLM) is a potential additive manufacturing (AM) technology. However, the application of SLM was confined due to low efficiency. To improve efficiency, SLM fabrication with a high layer thickness and fine powder was systematically researched, and the void areas and [...] Read more.

Selective laser melting (SLM) is a potential additive manufacturing (AM) technology. However, the application of SLM was confined due to low efficiency. To improve efficiency, SLM fabrication with a high layer thickness and fine powder was systematically researched, and the void areas and hollow powders can be reduced by using fine powder. Single-track experiments were used to narrow down process parameter windows. Multi-layer fabrication relative density can be reached 99.99% at the exposure time-point distance-hatch space of 120 μs-40 μm-240 μm. Also, the building rate can be up to 12 mm³/s, which is about 3–10 times higher than the previous studies. Three typical defects were found by studying deeply, including the un-melted defect between the molten pools, the micro-pore defect within the molten pool, and the irregular distribution of the splashing phenomenon. Moreover, the microstructure is mostly equiaxed crystals and a small amount of columnar crystals. The averages of ultimate tensile strength, yield strength, and elongation are 625 MPa, 525 MPa, and 39.9%, respectively. As exposure time increased from 80 μs to 200 μs, the grain size is gradually grown up from 0.98 μm to 2.23 μm, the grain aspect ratio is close to 1, and the tensile properties are shown as a downward trend. The tensile properties of high layer thickness fabricated are not significantly different than those with a coarse-powder layer thickness of low in previous research. Full article

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12 pages, 6971 KiB

Open AccessArticle

Self-Assembled Gold Nano-Ripple Formation by Gas Cluster Ion Beam Bombardment

by Buddhi P. Tilakaratne^1,*, Quark Y. Chen^1,2 and Wei-Kan Chu¹

¹ Department of Physics and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Rd, Houston, TX 77204, USA

² Department of Physics and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan

Materials 2017, 10(9), 1056; https://doi.org/10.3390/ma10091056 - 8 Sep 2017

Cited by 23 | Viewed by 5521

Abstract

In this study, we used a 30 keV argon cluster ion beam bombardment to investigate the dynamic processes during nano-ripple formation on gold surfaces. Atomic force microscope analysis shows that the gold surface has maximum roughness at an incident angle of 60° from [...] Read more.

In this study, we used a 30 keV argon cluster ion beam bombardment to investigate the dynamic processes during nano-ripple formation on gold surfaces. Atomic force microscope analysis shows that the gold surface has maximum roughness at an incident angle of 60° from the surface normal; moreover, at this angle, and for an applied fluence of 3 × 10¹⁶ clusters/cm², the aspect ratio of the nano-ripple pattern is in the range of ~50%. Rutherford backscattering spectrometry analysis reveals a formation of a surface gradient due to prolonged gas cluster ion bombardment, although the surface roughness remains consistent throughout the bombarded surface area. As a result, significant mass redistribution is triggered by gas cluster ion beam bombardment at room temperature. Where mass redistribution is responsible for nano-ripple formation, the surface erosion process refines the formed nano-ripple structures. Full article

(This article belongs to the Special Issue Ion Beam Analysis, Modification, and Irradiation of Materials)

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9 pages, 3559 KiB

Open AccessArticle

Fatigue Properties of the Ultra-High Strength Steel TM210A

by Guang-qiang Yin^1,2

, Xia Kang¹ and Gui-ping Zhao^1,*

¹ State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China

² Institute of Aviation Equipment, Qing’an Group Corporation Limited, Xi’an 710077, China

Materials 2017, 10(9), 1057; https://doi.org/10.3390/ma10091057 - 9 Sep 2017

Cited by 19 | Viewed by 4879

Abstract

This paper presents the results of an experiment to investigate the high cycle fatigue properties of the ultra-high strength steel TM210A. A constant amplitude rotating bending fatigue experiment was performed at room temperature at stress ratio R = −1. In order to evaluate [...] Read more.

This paper presents the results of an experiment to investigate the high cycle fatigue properties of the ultra-high strength steel TM210A. A constant amplitude rotating bending fatigue experiment was performed at room temperature at stress ratio R = −1. In order to evaluate the notch effect, the fatigue experiment was carried out upon two sets of specimens, smooth and notched, respectively. In the experiment, the rotating bending fatigue life was tested using the group method, and the rotating bending fatigue limit was tested using the staircase method at 1 × 10⁷ cycles. A double weighted least square method was then used to fit the stress-life (S–N) curve. The S–N curves of the two sets of specimens were obtained and the morphologies of the fractures of the two sets of specimens were observed with scanning electron microscopy (SEM). The results showed that the fatigue limit of the smooth specimen for rotating bending fatigue was 615 MPa; the ratio of the fatigue limit to tensile strength was 0.29, and the cracks initiated at the surface of the smooth specimen; while the fatigue limit of the notched specimen for rotating bending fatigue was 363 MPa, and the cracks initiated at the edge of the notch. The fatigue notch sensitivity index of the ultra-high strength maraging steel TM210A was 0.69. Full article

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12 pages, 4679 KiB

Open AccessArticle

Towards Understanding the Polymerization Process in Bitumen Bio-Fluxes

by Jan B. Król¹

, Łukasz Niczke² and Karol J. Kowalski^1,*

¹ Faculty of Civil Engineering, Warsaw University of Technology, 00-637 Warsaw, Poland

² General Directorate for National Roads and Motorways, 66-004 Zielona Góra, Poland

Materials 2017, 10(9), 1058; https://doi.org/10.3390/ma10091058 - 9 Sep 2017

Cited by 24 | Viewed by 4994

Abstract

Bitumen is a commonly used material for road construction. According to environmental regulations, vegetable-based materials are applied for binder modification. Fluxed road bitumen containing a bio-flux oxidation product increases the consistency over time. The efficiency of crosslinking depends on the number of double [...] Read more.

Bitumen is a commonly used material for road construction. According to environmental regulations, vegetable-based materials are applied for binder modification. Fluxed road bitumen containing a bio-flux oxidation product increases the consistency over time. The efficiency of crosslinking depends on the number of double bonds and their position in the aliphatic chain of fatty acid. The main goal of this paper was to examine the structural changes taking place during hardening bitumen with bio-flux additives. Two types of road bitumens fluxed with two different oxidized methyl esters of rapeseed oil were used in this study. Various chemical and rheological tests were applied for the fluxed-bitumen at different stages of oxygen exposure. The oxidation of rapeseed oil methyl ester reduced the iodine amount by about 10%–30%. Hardening of the fluxed bitumen generally results in an increase of the resins content and a reduction of the aromatics and asphaltenes. In the temperature range of 0 °C to 40 °C, bio-flux results with a much higher increase in the phase angle than in temperatures above 40 °C in the bitumen binder. The increase in the proportion of the viscous component in the low and medium binder temperature is favorable due to the potential improvement of the fatigue resistance of the asphalt mixture with such binders. Full article

(This article belongs to the Section Biomaterials)

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8 pages, 2204 KiB

Open AccessArticle

Optical Characterization of Nano- and Microcrystals of EuPO₄ Created by One-Step Synthesis of Antimony-Germanate-Silicate Glass Modified by P₂O₅

by Jacek Zmojda^1,*, Marcin Kochanowicz¹

, Piotr Miluski¹

, Agata Baranowska¹, Wojciech A. Pisarski², Joanna Pisarska², Renata Jadach³, Maciej Sitarz³

and Dominik Dorosz³

¹ Department of Power Engineering, Photonics and Lighting Technology, Bialystok University of Technology 45D Wiejska Street, 15-351 Bialystok, Poland

² Institute of Chemistry, University of Silesia, 9 Szkolna Street, 40-007 Katowice, Poland

³ Faculty of Materials Science and Ceramics, AGH University of Science and Technology, 30 Mickiewicza Av., 30-059 Krakow, Poland

Materials 2017, 10(9), 1059; https://doi.org/10.3390/ma10091059 - 9 Sep 2017

Cited by 14 | Viewed by 4639

Abstract

Technology of active glass-ceramics (GC) is an important part of luminescent materials engineering. The classic method to obtain GC is based on annealing of parent glass in proper temperature and different time periods. Generally, only the bulk materials are investigated as a starting [...] Read more.

Technology of active glass-ceramics (GC) is an important part of luminescent materials engineering. The classic method to obtain GC is based on annealing of parent glass in proper temperature and different time periods. Generally, only the bulk materials are investigated as a starting host for further applications. However, the effect of an additional heat-treatment process on emission and structural properties during GC processing is omitted. Here, we focus on the possibility of obtaining transparent glass-ceramic doped with europium ions directly with a melt-quenching method. The influence of phosphate concentration (up to 10 mol %) on the inversion symmetry of local environment of Eu³⁺ ions in antimony-germanate-silicate (SGS) glass has been investigated. The Stark splitting of luminescence spectra and the local asymmetry ratio estimated by relation of (⁵D₀→⁷F₂)/(⁵D₀→⁷F₁) transitions in fabricated glass confirms higher local symmetry around Eu³⁺ ions. Based on XRD and SEM/EDX measurements, the EuPO₄ nano- and microcrystals with monoclinic geometry were determined. Therefore, in our experiment, we confirmed possibility of one-step approach to fabricate crystalline structures (glass-ceramic) in Eu–doped SGS glass without additional annealing process. Full article

(This article belongs to the Special Issue Luminescent Materials 2017)

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21 pages, 5492 KiB

Open AccessReview

Cellulose-Based Smart Fluids under Applied Electric Fields

by Kisuk Choi¹, Chun Yan Gao², Jae Do Nam¹ and Hyoung Jin Choi^2,*

¹ Department of Polymer Science and Engineering, Sungkyunkwan University, Suwon 440-746, Korea

² Department of Polymer Science and Engineering, Inha University, Incheon 22212, Korea

Materials 2017, 10(9), 1060; https://doi.org/10.3390/ma10091060 - 10 Sep 2017

Cited by 34 | Viewed by 6781

Abstract

Cellulose particles, their derivatives and composites have special environmentally benign features and are abundant in nature with their various applications. This review paper introduces the essential properties of several types of cellulose and their derivatives obtained from various source materials, and their use [...] Read more.

Cellulose particles, their derivatives and composites have special environmentally benign features and are abundant in nature with their various applications. This review paper introduces the essential properties of several types of cellulose and their derivatives obtained from various source materials, and their use in electro-responsive electrorheological (ER) suspensions, which are smart fluid systems that are actively responsive under applied electric fields, while, at zero electric field, ER fluids retain a liquid-like state. Given the actively controllable characteristics of cellulose-based smart ER fluids under an applied electric field regarding their rheological and dielectric properties, they can potentially be applied for various industrial devices including dampers and haptic devices. Full article

(This article belongs to the Special Issue Nanocellulose-Based Functional Materials)

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10 pages, 6016 KiB

Open AccessArticle

Coercivity Mechanism of (Nd_0.8Ce_0.2)_2.4Fe₁₂Co₂B Ribbons with Ferromagnetic Grain Boundary Phase

by Heyun Li, Yang Liang, Xiaohua Tan^*, Hui Xu, Pengfei Hu^* and Kezhi Ren

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

Materials 2017, 10(9), 1062; https://doi.org/10.3390/ma10091062 - 11 Sep 2017

Cited by 15 | Viewed by 4094

Abstract

Understanding the coercivity mechanism has had a substantial impact on developing economically more attractive RE-based (RE = rare earth) permanent materials because of price volatility of key RE metals (i.e., Nd and Dy) in recent years. In this work, we investigated the microstructure [...] Read more.

Understanding the coercivity mechanism has had a substantial impact on developing economically more attractive RE-based (RE = rare earth) permanent materials because of price volatility of key RE metals (i.e., Nd and Dy) in recent years. In this work, we investigated the microstructure and magnetic properties of melt-spun (Nd_0.8Ce_0.2)_2.4Fe₁₂Co₂B ribbons and annealed samples at 773 K for 15 min with 1 Tesla (T) magnetic field to better understand the coercivity mechanism. We found hard magnetic grains were surrounded by thin and continuous layers along the grain boundaries (GBs) with a high concentration of ferromagnetic elements (Fe + Co >74 at%). The obvious positive peak in the δM plot and the interaction domain structure observed by Lorentz magnetic microscopy indicate that there is strong exchange coupling interaction through the ferromagnetic GB phase between hard magnetic grains. The annealing in an applied magnetic field of 1 T increases the remanence by enhancing the exchange coupling interaction, leading to a maximum product energy ((BH)_max) which is 16% higher than that of melt-spun ribbons. We also studied the temperature dependence of the coercivity in a temperature range of 300–500 K, and proposed that the coercivity of melt-spun (Nd_0.8Ce_0.2)_2.4Fe₁₂Co₂B ribbons with ferromagnetic GB phase at room temperature was from the combination of strong domain-wall pinning and nucleation. The same mechanism works in the annealed ribbons. Full article

(This article belongs to the Section Advanced Materials Characterization)

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12 pages, 1536 KiB

Open AccessFeature PaperArticle

Optimal Structure of a Plasmonic Chip for Sensitive Bio-Detection with the Grating-Coupled Surface Plasmon-Field Enhanced Fluorescence (GC-SPF)

by Keiko Tawa^1,2,*

, Takuya Nakayama^1,2 and Kenji Kintaka²

¹ School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan

² Inorganic Functional Materials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan

Materials 2017, 10(9), 1063; https://doi.org/10.3390/ma10091063 - 11 Sep 2017

Cited by 16 | Viewed by 5031

Abstract

Surface plasmon field-enhanced fluorescence (SPF) has been one of the powerful tools for biosensors and bioimaging. A wavelength-scale periodic structure coated with a thin metal film is called a plasmonic chip, and it can provide SPF. SPF of Cy5-streptavidin (Cy5-SA) was measured on [...] Read more.

Surface plasmon field-enhanced fluorescence (SPF) has been one of the powerful tools for biosensors and bioimaging. A wavelength-scale periodic structure coated with a thin metal film is called a plasmonic chip, and it can provide SPF. SPF of Cy5-streptavidin (Cy5-SA) was measured on a biotinylated plasmonic chip with a grating of 480 nm-pitch. The optimal structure of a plasmonic sensor-chip was designed for improving detection sensitivity. The silver film thickness dependence of the SPF intensity was measured under the irradiation of the top panel of a sensor chip. Furthermore, the dependence of the SPF intensity on the distance from the metal surface was also investigated. The optimal structure for the largest fluorescence enhancement factor was 150 nm-thick silver and 10 nm-thick SiO₂ layers due to the enhanced electric field (excitation field), the surface plasmon coupled emission (SPCE), and the interference effect with reflected light. The largest enhancement factor was found to be 170-fold. Furthermore, not only the largest fluorescence intensity but also stable lower background noise were found to be essential for higher-sensitive detection. Full article

(This article belongs to the Special Issue Advance in Plasmonics and Metamaterials)

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8 pages, 1703 KiB

Open AccessArticle

Efficient Inverted Organic Solar Cells Based on a Fullerene Derivative-Modified Transparent Cathode

by Yifan Wang^1,2, Hailin Cong^1,2,*

, Bing Yu^1,2, Zhiguo Zhang³ and Xiaowei Zhan⁴

¹ Institute of Biomedical Materials and Engineering, College of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, China

² Laboratory for New Fiber Materials and Modern Textile, Growing Base for State Key Laboratory, College of Materials Science and Engineering, Qingdao University, Qingdao 266071, China

³ Beijing National Laboratory for Molecular Sciences and Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China

⁴ Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China

Materials 2017, 10(9), 1064; https://doi.org/10.3390/ma10091064 - 11 Sep 2017

Cited by 16 | Viewed by 4666

Abstract

Indium tin oxide (ITO) is a transparent conductive material which is extensively used in organic solar cells (OSCs) as electrodes. In inverted OSCs, ITO is usually employed as a cathode, which should be modified by cathode buffer layers (CBLs) to achieve better contact [...] Read more.

Indium tin oxide (ITO) is a transparent conductive material which is extensively used in organic solar cells (OSCs) as electrodes. In inverted OSCs, ITO is usually employed as a cathode, which should be modified by cathode buffer layers (CBLs) to achieve better contact with the active layers. In this paper, an amine group functionalized fullerene derivative (DMAPA-C₆₀) is used as a CBL to modify the transparent cathode ITO in inverted OSCs based on PTB7 as a donor and PC₇₁BM as an acceptor. Compared with traditional ZnO CBL, DMAPA-C₆₀ exhibited comparable transmittance. OSCs based on DMAPA-C₆₀ show much better device performance compared with their ZnO counterparts (power conversion efficiencies (PCEs) improved from 6.24 to 7.43%). This is mainly because a better contact between the DMAPA-C₆₀ modified ITO and the active layer is formed, which leads to better electron transport and collection. Nanoscale morphologies also demonstrate that the surface of DMAPA-C₆₀-modified ITO is plainer than the ZnO counterparts, which also leads to the better device performance. Full article

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14 pages, 7886 KiB

Open AccessArticle

A Novel Approach to Estimate the Plastic Anisotropy of Metallic Materials Using Cross-Sectional Indentation Applied to Extruded Magnesium Alloy AZ31B

by Mingzhi Wang, Jianjun Wu^*, Hongfei Wu, Zengkun Zhang and He Fan

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

Materials 2017, 10(9), 1065; https://doi.org/10.3390/ma10091065 - 11 Sep 2017

Cited by 12 | Viewed by 4296

Abstract

In this paper, a methodology is presented for obtaining the plastic anisotropy of bulk metallic materials using cross-sectional indentation. This method relies on spherical indentation on the free edge of a specimen, and examining the out-of-plane residual deformation contour persisting on the cross-section [...] Read more.

In this paper, a methodology is presented for obtaining the plastic anisotropy of bulk metallic materials using cross-sectional indentation. This method relies on spherical indentation on the free edge of a specimen, and examining the out-of-plane residual deformation contour persisting on the cross-section after unloading. Results obtained from numerical simulation revealed that some important aspects of the out-of-plane residual deformation field are only sensitive to the extent of the material plastic anisotropy, and insensitive to strain hardening, yield strain, elastic anisotropy, and the selected displacement threshold value. An explicit equation is presented to correlate the plastic anisotropy with the characteristic parameter of the bottom shape of residual deformation contour, and it is used to uniquely determine the material plastic anisotropy in cross-sectional indentation. Effectiveness of the proposed method is verified by application on magnesium alloy AZ31B, and the plastic anisotropy parameter obtained from indentation and uniaxial tests show good agreement. Full article

(This article belongs to the Special Issue Advanced Nanoindentation in Materials)

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26 pages, 11998 KiB

Open AccessFeature PaperReview

Review on the Antimicrobial Properties of Carbon Nanostructures

by Ahmed Al-Jumaili¹, Surjith Alancherry¹, Kateryna Bazaka^1,2 and Mohan V. Jacob^1,*

¹ Electronics Materials Lab, College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia

² School of Chemistry, Physics, Mechanical Engineering, Queensland University of Technology, Brisbane, QLD 4000, Australia

Materials 2017, 10(9), 1066; https://doi.org/10.3390/ma10091066 - 11 Sep 2017

Cited by 388 | Viewed by 18577

Abstract

Swift developments in nanotechnology have prominently encouraged innovative discoveries across many fields. Carbon-based nanomaterials have emerged as promising platforms for a broad range of applications due to their unique mechanical, electronic, and biological properties. Carbon nanostructures (CNSs) such as fullerene, carbon nanotubes (CNTs), [...] Read more.

Swift developments in nanotechnology have prominently encouraged innovative discoveries across many fields. Carbon-based nanomaterials have emerged as promising platforms for a broad range of applications due to their unique mechanical, electronic, and biological properties. Carbon nanostructures (CNSs) such as fullerene, carbon nanotubes (CNTs), graphene and diamond-like carbon (DLC) have been demonstrated to have potent broad-spectrum antibacterial activities toward pathogens. In order to ensure the safe and effective integration of these structures as antibacterial agents into biomaterials, the specific mechanisms that govern the antibacterial activity of CNSs need to be understood, yet it is challenging to decouple individual and synergistic contributions of physical, chemical and electrical effects of CNSs on cells. In this article, recent progress in this area is reviewed, with a focus on the interaction between different families of carbon nanostructures and microorganisms to evaluate their bactericidal performance. Full article

(This article belongs to the Special Issue Biocompatibility of Materials)

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17 pages, 2016 KiB

Open AccessArticle

Time-Dependent Material Properties of Shotcrete: Experimental and Numerical Study

by Matthias Neuner^1,*

, Tobias Cordes², Martin Drexel¹ and Günter Hofstetter¹

¹ Unit for Strength of Materials and Structural Analysis, Institute of Basic Sciences in Engineering Sciences, University of Innsbruck, Technikerstr 13, A-6020 Innsbruck, Austria

² Brenner Basetunnel BBT SE, A-6020 Innsbruck, Austria

Materials 2017, 10(9), 1067; https://doi.org/10.3390/ma10091067 - 11 Sep 2017

Cited by 29 | Viewed by 6017

Abstract

A new experimental program, focusing on the evolution of the Young’s modulus, uniaxial compressive strength, shrinkage and creep of shotcrete is presented. The laboratory tests are, starting at very young ages of the material, conducted on two different types of specimens sampled at [...] Read more.

A new experimental program, focusing on the evolution of the Young’s modulus, uniaxial compressive strength, shrinkage and creep of shotcrete is presented. The laboratory tests are, starting at very young ages of the material, conducted on two different types of specimens sampled at the site of the Brenner Basetunnel. The experimental results are evaluated and compared to other experiments from the literature. In addition, three advanced constitutive models for shotcrete, i.e., the model by Meschke, the model by Schädlich and Schweiger, and the model by Neuner et al., are validated on the basis of the test data, and the capabilities of the models to represent the observed shotcrete behavior are assessed. Hence, the gap between the the outdated experimental data on shotcrete available in the literature on the one hand and the nowadays available advanced shotcrete models, on the other hand, is closed. Full article

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11 pages, 4025 KiB

Open AccessArticle

A Graphene-Based Flexible Pressure Sensor with Applications to Plantar Pressure Measurement and Gait Analysis

by Cunguang Lou¹

, Shuo Wang¹, Tie Liang¹, Chenyao Pang¹, Lei Huang², Mingtao Run³ and Xiuling Liu^1,*

¹ Department of Biomedical Engineering, College of Electronic Information Engineering & Key Laboratory of Digital Medical Engineering of Hebei Province, Hebei University, Baoding 071002, China

² Department of Molecular, Cell and Cancer Biology University of Massachusetts Medical School, Plantation Street, Worcester, MA 01605, USA

³ College of Chemistry & Environment Science, Hebei University, Baoding 071002, China

Materials 2017, 10(9), 1068; https://doi.org/10.3390/ma10091068 - 11 Sep 2017

Cited by 120 | Viewed by 12323

Abstract

In the present study, we propose and develop a flexible pressure sensor based on the piezoresistive effect of multilayer graphene films on polyester textile. The pressure response results from the deformation of graphene conductive network structure and the changes in resistance. Here, we [...] Read more.

In the present study, we propose and develop a flexible pressure sensor based on the piezoresistive effect of multilayer graphene films on polyester textile. The pressure response results from the deformation of graphene conductive network structure and the changes in resistance. Here, we show that the graphene pressure sensor can achieve a sensitivity value of 0.012 kPa

^{- 1}

, the measurement range can be as high as 800 kPa, and the response time can reach to 50 ms. Subsequently, a stable in-shoe wireless plantar pressure measurement system is developed and dynamic pressure distribution is acquired in real-time. Overall, the graphene textile pressure sensor has the advantage of wide dynamic range, flexibility and comfort, which provides the high possibility for footwear evaluation, clinical gait analysis and pathological foot diagnosis. Full article

(This article belongs to the Special Issue Polymeric Materials for Medical Applications)

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18 pages, 5139 KiB

Open AccessArticle

Drilling High Precision Holes in Ti6Al4V Using Rotary Ultrasonic Machining and Uncertainties Underlying Cutting Force, Tool Wear, and Production Inaccuracies

by M. A. K. Chowdhury^1,*, A. M. M. Sharif Ullah²

and Saqib Anwar¹

¹ Industrial Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia

² Faculty of Engineering, Kitami Institute of Technology, 165 Koen-cho, Kitami, Hokkaido 090-8507, Japan

Materials 2017, 10(9), 1069; https://doi.org/10.3390/ma10091069 - 12 Sep 2017

Cited by 15 | Viewed by 6369

Abstract

Ti6Al4V alloys are difficult-to-cut materials that have extensive applications in the automotive and aerospace industry. A great deal of effort has been made to develop and improve the machining operations of Ti6Al4V alloys. This paper presents an experimental study that systematically analyzes the [...] Read more.

Ti6Al4V alloys are difficult-to-cut materials that have extensive applications in the automotive and aerospace industry. A great deal of effort has been made to develop and improve the machining operations of Ti6Al4V alloys. This paper presents an experimental study that systematically analyzes the effects of the machining conditions (ultrasonic power, feed rate, spindle speed, and tool diameter) on the performance parameters (cutting force, tool wear, overcut error, and cylindricity error), while drilling high precision holes on the workpiece made of Ti6Al4V alloys using rotary ultrasonic machining (RUM). Numerical results were obtained by conducting experiments following the design of an experiment procedure. The effects of the machining conditions on each performance parameter have been determined by constructing a set of possibility distributions (i.e., trapezoidal fuzzy numbers) from the experimental data. A possibility distribution is a probability-distribution-neural representation of uncertainty, and is effective in quantifying the uncertainty underlying physical quantities when there is a limited number of data points which is the case here. Lastly, the optimal machining conditions have been identified using these possibility distributions. Full article

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

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13 pages, 4427 KiB

Open AccessArticle

Laser Indirect Shock Welding of Fine Wire to Metal Sheet

by Xiao Wang^*, Tao Huang, Yapeng Luo and Huixia Liu

School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China

Materials 2017, 10(9), 1070; https://doi.org/10.3390/ma10091070 - 12 Sep 2017

Cited by 9 | Viewed by 5092

Abstract

The purpose of this paper is to present an advanced method for welding fine wire to metal sheet, namely laser indirect shock welding (LISW). This process uses silica gel as driver sheet to accelerate the metal sheet toward the wire to obtain metallurgical [...] Read more.

The purpose of this paper is to present an advanced method for welding fine wire to metal sheet, namely laser indirect shock welding (LISW). This process uses silica gel as driver sheet to accelerate the metal sheet toward the wire to obtain metallurgical bonding. A series of experiments were implemented to validate the welding ability of Al sheet/Cu wire and Al sheet/Ag wire. It was found that the use of a driver sheet can maintain high surface quality of the metal sheet. With the increase of laser pulse energy, the bonding area of the sheet/wire increased and the welding interfaces were nearly flat. Energy dispersive spectroscopy (EDS) results show that the intermetallic phases were absent and a short element diffusion layer which would limit the formation of the intermetallic phases emerging at the welding interface. A tensile shear test was used to measure the mechanical strength of the welding joints. The influence of laser pulse energy on the tensile failure modes was investigated, and two failure modes, including interfacial failure and failure through the wire, were observed. The nanoindentation test results indicate that as the distance to the welding interface decreased, the microhardness increased due to the plastic deformation becoming more violent. Full article

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

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13 pages, 22155 KiB

Open AccessArticle

Influence of Hot Rolling and Heat Treatment on the Microstructural Evolution of β20C Titanium Alloy

by Xin Liu^1,2, Donghui Yu^1,2, Qunbo Fan^1,2,* and Ran Shi^1,2

¹ School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China

² National Key Laboratory of Science and Technology on Materials under Shock and Impact, Beijing Institute of Technology, Beijing 100081, China

Materials 2017, 10(9), 1071; https://doi.org/10.3390/ma10091071 - 12 Sep 2017

Cited by 10 | Viewed by 3601

Abstract

The microstructural evolution and underlying mechanism of a new high strength, high toughness near β titanium alloy, β20C, during hot deformation, and heat treatment were studied qualitatively and quantitatively. It was found that dynamic recovery occurs mainly in β phase, while α phase [...] Read more.

The microstructural evolution and underlying mechanism of a new high strength, high toughness near β titanium alloy, β20C, during hot deformation, and heat treatment were studied qualitatively and quantitatively. It was found that dynamic recovery occurs mainly in β phase, while α phase undergoes both a dynamic recovery and continuous incomplete dynamic recrystallization with a fraction of high-angle grain boundaries (≥15°) of 21.1% under hot-rolling. Subsequently, α phase undergoes static recrystallization with an increasing fraction of high-angle grain boundaries (21.1%→60.7%) under annealing, while the grains are equiaxed with refined grain sizes of 1.63 µm observed from the rolling direction (RD) and 1.66 µm observed from the transverse direction (TD). Moreover, the average aspect ratio of the lamellar α phase was 2.44 observed from the RD and 3.12 observed from the TD after hot rolling, but decreased to 2.20 observed from the RD, and 2.53 observed from the TD after annealing. Furthermore, the strict Burgers’ relationship between α and β phases changed after hot-rolling and remains the distortion, even after the static recrystallization process of α phase during annealing. Full article

(This article belongs to the Section Advanced Materials Characterization)

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17 pages, 3085 KiB

Open AccessArticle

Wet-Chemical Synthesis of 3D Stacked Thin Film Metal-Oxides for All-Solid-State Li-Ion Batteries

by Evert Jonathan Van den Ham¹, Giulia Maino¹, Gilles Bonneux¹, Wouter Marchal¹, Ken Elen^1,2, Sven Gielis¹, Felix Mattelaer³

, Christophe Detavernier³, Peter H. L. Notten^4,5, Marlies K. Van Bael¹

and An Hardy^1,*

¹ Inorganic and Physical Chemistry and Imec, Division Imomec, Institute for Materials Research, Hasselt University, Martelarenlaan 42, 3500 Hasselt, Belgium

² Imec vzw, Division Imomec, Wetenschapspark 1, B-3590 Diepenbeek, Belgium

³ Department of Solid State Sciences, Ghent University, Krijgslaan 281 S1, 9000 Gent, Belgium

⁴ Energy Materials & Devices, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands

⁵ Forschungszentrum Jülich, Fundamental Electrochemistry (IEK-9), D-52425 Jülich, Germany

Materials 2017, 10(9), 1072; https://doi.org/10.3390/ma10091072 - 12 Sep 2017

Cited by 1 | Viewed by 5947

Abstract

By ultrasonic spray deposition of precursors, conformal deposition on 3D surfaces of tungsten oxide (WO₃) negative electrode and amorphous lithium lanthanum titanium oxide (LLT) solid-electrolyte has been achieved as well as an all-solid-state half-cell. Electrochemical activity was achieved of the WO [...] Read more.

By ultrasonic spray deposition of precursors, conformal deposition on 3D surfaces of tungsten oxide (WO₃) negative electrode and amorphous lithium lanthanum titanium oxide (LLT) solid-electrolyte has been achieved as well as an all-solid-state half-cell. Electrochemical activity was achieved of the WO₃ layers, annealed at temperatures of 500 °C. Galvanostatic measurements show a volumetric capacity (415 mAh·cm⁻³) of the deposited electrode material. In addition, electrochemical activity was shown for half-cells, created by coating WO₃ with LLT as the solid-state electrolyte. The electron blocking properties of the LLT solid-electrolyte was shown by ferrocene reduction. 3D depositions were done on various micro-sized Si template structures, showing fully covering coatings of both WO₃ and LLT. Finally, the thermal budget required for WO₃ layer deposition was minimized, which enabled attaining active WO₃ on 3D TiN/Si micro-cylinders. A 2.6-fold capacity increase for the 3D-structured WO₃ was shown, with the same current density per coated area. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry Applied to Materials Science)

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14 pages, 4543 KiB

Open AccessFeature PaperArticle

Controlled Shrinkage of Expanded Glass Particles in Metal Syntactic Foams

by Kadhim Al-Sahlani, Mehdi Taherishargh, Erich Kisi and Thomas Fiedler^*

School of Engineering, the University of Newcastle, Callaghan 2308, Australia

Materials 2017, 10(9), 1073; https://doi.org/10.3390/ma10091073 - 13 Sep 2017

Cited by 26 | Viewed by 6282

Abstract

Metal matrix syntactic foams have been fabricated via counter-gravity infiltration of a packed bed of recycled expanded glass particles (EG) with A356 aluminum alloy. Particle shrinkage was studied and has been utilized to increase the particles’ strength and tailor the mechanical properties of [...] Read more.

Metal matrix syntactic foams have been fabricated via counter-gravity infiltration of a packed bed of recycled expanded glass particles (EG) with A356 aluminum alloy. Particle shrinkage was studied and has been utilized to increase the particles’ strength and tailor the mechanical properties of the expanded glass/metal syntactic foam (EG-MSF). The crushing strength of particles could be doubled by shrinking them for 20 min at 700 °C. Owing to the low density of EG (0.20–0.26 g/cm³), the resulting foam exhibits a low density (1.03–1.19 g/cm³) that increases slightly due to particle shrinkage. Chemical and physical analyses of EG particles and the resulting foams were conducted. Furthermore, metal syntactic foam samples were tested in uni-axial compression tests. The stress-strain curves obtained exhibit three distinct regions: elastic deformation followed by a stress plateau and densification commencing at 70–80% macroscopic strain. Particle shrinkage increased the mechanical strength of the foam samples and their average plateau stress increased from 15.5 MPa to 26.7 MPa. Full article

(This article belongs to the Section Porous Materials)

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8 pages, 1315 KiB

Open AccessArticle

Measuring the Pull-Off Force of an Individual Fiber Using a Novel Picoindenter/Scanning Electron Microscope Technique

by Rahul Sahay¹, Ihor Radchenko²

, Arief S. Budiman^2,* and Avinash Baji^1,*

¹ Engineering Product Development (EPD) Pillar, Singapore University of Technology and Design, 8 Somapah Rd, Singapore 487372, Singapore

² The Xtreme Materials Laboratory (XML), Singapore University of Technology and Design, 8 Somapah Rd, Singapore 487372, Singapore

Materials 2017, 10(9), 1074; https://doi.org/10.3390/ma10091074 - 13 Sep 2017

Cited by 3 | Viewed by 4327

Abstract

We employed a novel picoindenter (PI)/scanning electron microscopy (SEM) technique to measure the pull-off force of an individual electrospun poly(vinylidene fluoride) (PVDF) fibers. Individual fibers were deposited over a channel in a custom-designed silicon substrate, which was then attached to a picoindenter. The [...] Read more.

We employed a novel picoindenter (PI)/scanning electron microscopy (SEM) technique to measure the pull-off force of an individual electrospun poly(vinylidene fluoride) (PVDF) fibers. Individual fibers were deposited over a channel in a custom-designed silicon substrate, which was then attached to a picoindenter. The picoindenter was then positioned firmly on the sample stage of the SEM. The picoindenter tip laterally pushed individual fibers to measure the force required to detach it from the surface of substrate. SEM was used to visualize and document the process. The measured pull-off force ranged between 5.8 ± 0.2 μN to ~17.8 ± 0.2 μN for individual fibers with average diameter ranging from 0.8 to 2.3 μm. Thus, this study, a first of its kind, demonstrates the use of a picoindenter to measure the pull-off force of a single micro/nanofiber. Full article

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

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13 pages, 4900 KiB

Open AccessArticle

Chitosan Gel Sheet Containing Polymeric Micelles: Synthesis and Gelation Properties of PEG-Grafted Chitosan

by Chikara Yoshida, Yusuke Uchida, Tomoki Ito, Taku Takami and Yoshihiko Murakami^*

Department of Organic and Polymer Materials Chemistry, Faculty of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan

Materials 2017, 10(9), 1075; https://doi.org/10.3390/ma10091075 - 13 Sep 2017

Cited by 11 | Viewed by 6885

Abstract

Wound-dressing sheet biomaterials can cover wound sites and enhance wound healing. In this study, a detailed evaluation of the factors affecting both the PEG modification percentage (PMP) in poly(ethylene glycol) (PEG)-grafted chitosan synthesis and the gelation properties of PEG-grafted chitosan was presented for [...] Read more.

Wound-dressing sheet biomaterials can cover wound sites and enhance wound healing. In this study, a detailed evaluation of the factors affecting both the PEG modification percentage (PMP) in poly(ethylene glycol) (PEG)-grafted chitosan synthesis and the gelation properties of PEG-grafted chitosan was presented for constructing our novel hybrid hydrogel sheet consisting of PEG-grafted chitosan (a gel-forming polymer) and a reactive polymeric micelle (a crosslinker). It was confirmed that various factors (i.e., the weight ratio of PEG/chitosan, the pH of the buffer solution, reaction times, and reaction temperatures) in the preparation stage of PEG-grafted chitosans affected the PMP of PEG-grafted chitosans. Furthermore, the PMP of PEG-grafted chitosans affected their gelation properties. Finally, a ‘flexible’ hydrogel sheet that can be reversibly dried and moistened was successfully obtained. The dried rigid, thin sheet is expected to be suitable for stable preservation. The results obtained in this paper show that the incorporation of drug carriers into biomaterials is a novel approach to improve functionality. Full article

(This article belongs to the Section Biomaterials)

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14 pages, 6971 KiB

Open AccessArticle

Pitting Initiation and Propagation of X70 Pipeline Steel Exposed to Chloride-Containing Environments

by Zixuan Yang¹, Bo Kan¹, Jinxu Li^1,*, Yanjing Su¹, Lijie Qiao¹ and Alex A. Volinsky²

¹ Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), University of Science and Technology Beijing, Beijing 100083, China

² Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620, USA

Materials 2017, 10(9), 1076; https://doi.org/10.3390/ma10091076 - 13 Sep 2017

Cited by 37 | Viewed by 6222

Abstract

Inclusion-induced pitting initiation mechanisms in X70 steel were investigated by scanning electron microscopy, scanning Kelvin probe force microscopy (SKPFM), immersion and electrochemical polarization tests in chloride-containing ion solutions. There are three inclusion types in the X70 steel. Corrosion test results indicated that pitting [...] Read more.

Inclusion-induced pitting initiation mechanisms in X70 steel were investigated by scanning electron microscopy, scanning Kelvin probe force microscopy (SKPFM), immersion and electrochemical polarization tests in chloride-containing ion solutions. There are three inclusion types in the X70 steel. Corrosion test results indicated that pitting corrosion resistance of type A inclusion < type C inclusion < type B inclusion, i.e., (Mn, Ca)S < matrix < (Al, Ca)O. SKPFM test results show that the type A inclusion exhibited both lower and higher potentials than the matrix, while the type B inclusion exhibited higher potential than the matrix. The corrosion test and the SKPFM potential test results are consistent. Potentiodynamic polarization results indicate that the type A and C are active inclusions, while the type B is an inactive inclusion. Three kinds of possible mechanisms of inclusion-induced pitting corrosion are established for the X70 steel. Full article

(This article belongs to the Section Energy Materials)

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11 pages, 2671 KiB

Open AccessArticle

Material Viscoelasticity-Induced Drift of Micro-Accelerometers

by Wu Zhou¹

, Peng Peng^1,*, Huijun Yu¹, Bei Peng^1,* and Xiaoping He²

¹ School of Mechatronics Engineering, University of Electronic Technology and Science of China, Chengdu 611731, China

² Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang 621900, China

Materials 2017, 10(9), 1077; https://doi.org/10.3390/ma10091077 - 14 Sep 2017

Cited by 12 | Viewed by 5458

Abstract

Polymer-based materials are commonly used as an adhesion layer for bonding die chip and substrate in micro-system packaging. Their properties exhibit significant impact on the stability and reliability of micro-devices. The viscoelasticity, one of most important attributes of adhesive materials, is investigated for [...] Read more.

Polymer-based materials are commonly used as an adhesion layer for bonding die chip and substrate in micro-system packaging. Their properties exhibit significant impact on the stability and reliability of micro-devices. The viscoelasticity, one of most important attributes of adhesive materials, is investigated for the first time in this paper to evaluate the long-term drift of micro-accelerometers. The accelerometer was modeled by a finite element (FE) method to emulate the structure deformation and stress development induced by change of adhesive property. Furthermore, the viscoelastic property of the adhesive was obtained by a series of stress–relaxation experiments using dynamic mechanical analysis (DMA). The DMA curve was imported into the FE model to predict the drift of micro-accelerometers over time and temperature. The prediction results verified by experiments showed that the accelerometer experienced output drift due to the development of packaging stress induced by both the thermal mismatch and viscoelastic behaviors of the adhesive. The accelerometers stored at room temperature displayed a continuous drift of zero offset and sensitivity because of the material viscoelasticity. Moreover, the drift level of accelerometers experiencing high temperature load was relatively higher than those of lower temperature in the same period. Full article

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15 pages, 11004 KiB

Open AccessArticle

Largest Magnetic Moments in the Half-Heusler Alloys XCrZ (X = Li, K, Rb, Cs; Z = S, Se, Te): A First-Principles Study

by Xiaotian Wang^1,3

, Zhenxiang Cheng³

and Guodong Liu^2,*

¹ School of Physical Science and Technology, Southwest University, Chongqing 400715, China

² College of Physics and Information Technology, Chongqing Normal University, Chongqing 401331, China

³ Institute for Superconducting & Electronic Materials (ISEM), University of Wollongong, Wollongong 2500, Australia

Materials 2017, 10(9), 1078; https://doi.org/10.3390/ma10091078 - 14 Sep 2017

Cited by 51 | Viewed by 8912

Abstract

A recent theoretical work indicates that intermetallic materials LiMnZ (Z = N, P) with a half-Heusler structure exhibit half-metallic (HM) behaviors at their strained lattice constants, and the magnetic moments of these alloys are expected to reach as high as 5 μ_B [...] Read more.

A recent theoretical work indicates that intermetallic materials LiMnZ (Z = N, P) with a half-Heusler structure exhibit half-metallic (HM) behaviors at their strained lattice constants, and the magnetic moments of these alloys are expected to reach as high as 5 μ_B per formula unit. (Damewood et al. Phys. Rev. B 2015, 91, 064409). This work inspired us to find new Heusler-based half-metals with the largest magnetic moment. With the help of the first-principles calculation, we reveal that XCrZ (X = K, Rb, Cs; Z = S, Se, Te) alloys show a robust, half-metallic nature with a large magnetic moment of 5 μ_B at their equilibrium and strained lattice constants in their most stable phases, while the excellent HM nature of LiCrZ (Z = S, Se, Te) alloys can be observed in one of their metastable phases. Moreover, the effects of uniform strain in LiCrZ (Z = S, Se, Te) alloys in type II arrangement have also been discussed. Full article

(This article belongs to the Special Issue Intermetallic Alloys: Fabrication, Properties and Applications 2017)

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14 pages, 3193 KiB

Open AccessArticle

Low-Temperature Self-Healing of a Microcapsule-Type Protective Coating

by Dong-Min Kim

, Yu-Jin Cho, Ju-Young Choi, Beom-Jun Kim, Seung-Won Jin and Chan-Moon Chung^*

Department of Chemistry, Yonsei University, Wonju 26493, Gangwon-do, Korea

Materials 2017, 10(9), 1079; https://doi.org/10.3390/ma10091079 - 14 Sep 2017

Cited by 31 | Viewed by 6297

Abstract

Low-temperature self-healing capabilities are essential for self-healing materials exposed to cold environments. Although low-temperature self-healing concepts have been proposed, there has been no report of a microcapsule-type low-temperature self-healing system wherein the healing ability was demonstrated at low temperature. In this work, low-temperature [...] Read more.

Low-temperature self-healing capabilities are essential for self-healing materials exposed to cold environments. Although low-temperature self-healing concepts have been proposed, there has been no report of a microcapsule-type low-temperature self-healing system wherein the healing ability was demonstrated at low temperature. In this work, low-temperature self-healing of a microcapsule-type protective coating was demonstrated. This system employed silanol-terminated polydimethylsiloxane (STP) as a healing agent and dibutyltin dilaurate (DD) as a catalyst. STP underwent a condensation reaction at −20 °C in the presence of DD to give a viscoelastic product. The reaction behavior of STP and the viscoelasticity of the reaction product were investigated. STP and DD were separately microencapsulated by in situ polymerization and interfacial polymerization methods, respectively. The STP- and DD-loaded microcapsules were mixed into a commercial enamel paint, and the resulting formulation was applied to glass slides, steel panels, and mortars to prepare self-healing coatings. When the self-healing coatings were damaged at a low temperature (−20 °C), STP and DD were released from broken microcapsules and filled the damaged area. This process was effectively visualized using a fluorescent dye. The self-healing coatings were scratched and subjected to corrosion tests, electrochemical tests, and saline solution permeability tests. The temperature of the self-healing coatings was maintained at −20 °C before and after scratching and during the tests. We successfully demonstrated that the STP/DD-based coating system has good low-temperature self-healing capability. Full article

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13 pages, 4906 KiB

Open AccessArticle

Facile Preparation of a Robust and Durable Superhydrophobic Coating Using Biodegradable Lignin-Coated Cellulose Nanocrystal Particles

by Jingda Huang^1,2, Siqun Wang^1,2,*

and Shaoyi Lyu^1,*

¹ Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China

² Center for Renewable Carbon, University of Tennessee, Knoxville, TN 37996, USA

Materials 2017, 10(9), 1080; https://doi.org/10.3390/ma10091080 - 14 Sep 2017

Cited by 32 | Viewed by 7948

Abstract

It is a challenge for a superhydrophobic coating to overcome the poor robustness and the rough surface structure that is usually built using inorganic particles that are difficult to degrade. In this study, a robust superhydrophobic coating is facilely prepared by using commercial [...] Read more.

It is a challenge for a superhydrophobic coating to overcome the poor robustness and the rough surface structure that is usually built using inorganic particles that are difficult to degrade. In this study, a robust superhydrophobic coating is facilely prepared by using commercial biodegradable lignin-coated cellulose nanocrystal (L-CNC) particles after hydrophobic modification to build rough surface structures, and by choosing two different adhesives (double-sided tape and quick-setting epoxy) to support adhesion between the L-CNC particles and the substrates. In addition to excellent self-cleaning and water repellence properties, the resulting coatings show outstanding mechanical strength and durability against sandpaper abrasion, finger-wipe, knife-scratch, water jet, UV radiation, high temperature, and acidic and alkali solutions, possessing a wide application prospect. Full article

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13 pages, 4990 KiB

Open AccessFeature PaperArticle

The Role of Controlled Surface Topography and Chemistry on Mouse Embryonic Stem Cell Attachment, Growth and Self-Renewal

by Melanie Macgregor¹

, Rachel Williams^2,*

, Joni Downes², Akash Bachhuka³ and Krasimir Vasilev^1,*

¹ School of Engineering, Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia

² Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool L7 8TX, UK

³ Institute for Photonics and Advanced Sensing, University of Adelaide, Adelaide, SA 5000, Australia

Materials 2017, 10(9), 1081; https://doi.org/10.3390/ma10091081 - 14 Sep 2017

Cited by 25 | Viewed by 5472

Abstract

The success of stem cell therapies relies heavily on our ability to control their fate in vitro during expansion to ensure an appropriate supply. The biophysical properties of the cell culture environment have been recognised as a potent stimuli influencing cellular behaviour. In [...] Read more.

The success of stem cell therapies relies heavily on our ability to control their fate in vitro during expansion to ensure an appropriate supply. The biophysical properties of the cell culture environment have been recognised as a potent stimuli influencing cellular behaviour. In this work we used advanced plasma-based techniques to generate model culture substrates with controlled nanotopographical features of 16 nm, 38 nm and 68 nm in magnitude, and three differently tailored surface chemical functionalities. The effect of these two surface properties on the adhesion, spreading, and self-renewal of mouse embryonic stem cells (mESCs) were assessed. The results demonstrated that physical and chemical cues influenced the behaviour of these stem cells in in vitro culture in different ways. The size of the nanotopographical features impacted on the cell adhesion, spreading and proliferation, while the chemistry influenced the cell self-renewal and differentiation. Full article

(This article belongs to the Special Issue Biocompatibility of Materials)

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17 pages, 4735 KiB

Open AccessArticle

Bonding Behavior of Deformed Steel Rebars in Sustainable Concrete Containing both Fine and Coarse Recycled Aggregates

by Sun-Woo Kim¹, Wan-Shin Park¹, Young-Il Jang¹, Seok-Joon Jang² and Hyun-Do Yun^2,*

¹ Department of Construction Engineering Education, Chungnam National University, Daejeon 34134, Korea

² Department of Architectural Engineering, Chungnam National University, Daejeon 34134, Korea

Materials 2017, 10(9), 1082; https://doi.org/10.3390/ma10091082 - 14 Sep 2017

Cited by 23 | Viewed by 6722

Abstract

In order to assess the bond behavior of deformed steel rebars in recycled-aggregate concrete (RAC) incorporating both fine and coarse recycled aggregate, pull-out tests were carried out in this study on 16-mm diameter deformed steel rebars embedded concentrically in RAC. The concrete was [...] Read more.

In order to assess the bond behavior of deformed steel rebars in recycled-aggregate concrete (RAC) incorporating both fine and coarse recycled aggregate, pull-out tests were carried out in this study on 16-mm diameter deformed steel rebars embedded concentrically in RAC. The concrete was designed using equivalently mixed proportions of both recycled coarse aggregate and recycled fine aggregate. The tests employed five types of recycled aggregate replacement combinations and three types of rebar placement orientation (i.e., vertical bars and two-tiered and three-tiered horizontal bars). Based on the pull-out test results, the maximum bond strength tended to decrease and the slip at the maximum bond strength increased as the average water absorption of the aggregate increased, irrespective of the rebar orientation or placement location within the concrete member. The pull-out test results for the horizontal steel rebars embedded in RAC indicate that the casting position effect could be determined from the mid-depth of the concrete member, irrespective of the member’s height. The normalized bond versus slip relationship between the deformed rebar and the RAC could be predicted using an empirical model based on regression analysis of the experimental data. Full article

(This article belongs to the Special Issue Recycled Materials, Eco-design and 3D Printing)

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23 pages, 9685 KiB

Open AccessArticle

Shape Memory Polyurethane Materials Containing Ferromagnetic Iron Oxide and Graphene Nanoplatelets

by Magdalena Urban and Michał Strankowski^*

Polymer Technology Department, Chemical Faculty, Gdańsk University of Technology,11/12 Narutowicza Street, 80233 Gdańsk, Poland

Materials 2017, 10(9), 1083; https://doi.org/10.3390/ma10091083 - 14 Sep 2017

Cited by 33 | Viewed by 7132

Abstract

Intelligent materials, such as memory shape polymers, have attracted considerable attention due to wide range of possible applications. Currently, intensive research is underway, in matters of obtaining memory shape materials that can be actuated via inductive methods, for example with help of magnetic [...] Read more.

Intelligent materials, such as memory shape polymers, have attracted considerable attention due to wide range of possible applications. Currently, intensive research is underway, in matters of obtaining memory shape materials that can be actuated via inductive methods, for example with help of magnetic field. In this work, an attempt was made to develop a new polymer composite—polyurethane modified with graphene nanoplates and ferromagnetic iron oxides—with improved mechanical properties and introduced magnetic and memory shape properties. Based on the conducted literature review, gathered data were compared to the results of similar materials. Obtained materials were tested for their thermal, rheological, mechanical and shape memory properties. Structure of both fillers and composites were also analyzed using various spectroscopic methods. The addition of fillers to the polyurethane matrix improved the mechanical and shape memory properties, without having a noticeable impact on thermal properties. As it was expected, the high content of fillers caused a significant change in viscosity of filled prepolymers (during the synthesis stage). Each of the studied composites showed better mechanical properties than the unmodified polyurethanes. The addition of magnetic particles introduced additional properties to the composite, which could significantly expand the functionality of the materials developed in this work. Full article

(This article belongs to the Special Issue Improving Performance of Nanocomposite Materials)

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21 pages, 4864 KiB

Open AccessArticle

Multiple Fatigue Failure Behaviors and Long-Life Prediction Approach of Carburized Cr-Ni Steel with Variable Stress Ratio

by Hailong Deng^1,2, Wei Li^1,*, Hongqiao Zhao¹ and Tatsuo Sakai³

¹ School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China

² College of Mechanical Engineering, Inner Mongulia University of Technology, Hohhot 010051, China

³ College of Science and Engineering, Ritsumeikan University, Kusatsu 5258577, Japan

Materials 2017, 10(9), 1084; https://doi.org/10.3390/ma10091084 - 14 Sep 2017

Cited by 17 | Viewed by 5809

Abstract

Axial loading tests with stress ratios R of −1, 0 and 0.3 were performed to examine the fatigue failure behavior of a carburized Cr-Ni steel in the long-life regime from 10⁴ to 10⁸ cycles. Results show that this steel represents continuously [...] Read more.

Axial loading tests with stress ratios R of −1, 0 and 0.3 were performed to examine the fatigue failure behavior of a carburized Cr-Ni steel in the long-life regime from 10⁴ to 10⁸ cycles. Results show that this steel represents continuously descending S-N characteristics with interior inclusion-induced failure under R = −1, whereas it shows duplex S-N characteristics with surface defect-induced failure and interior inclusion-induced failure under R = 0 and 0.3. The increasing tension eliminates the effect of compressive residual stress and promotes crack initiation from the surface or interior defects in the carburized layer. The FGA (fine granular area) formation greatly depends on the number of loading cycles, but can be inhibited by decreasing the compressive stress. Based on the evaluation of the stress intensity factor at the crack tip, the surface and interior failures in the short life regime can be characterized by the crack growth process, while the interior failure with the FGA in the long life regime can be characterized by the crack initiation process. In view of the good agreement between predicted and experimental results, the proposed approach can be well utilized to predict fatigue lives associated with interior inclusion-FGA-fisheye induced failure, interior inclusion-fisheye induced failure, and surface defect induced failure. Full article

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8 pages, 10447 KiB

Open AccessFeature PaperArticle

Enhanced Plasmonic Wavelength Selective Infrared Emission Combined with Microheater

by Hiroki Ishihara¹, Katsuya Masuno¹, Makoto Ishii¹, Shinya Kumagai² and Minoru Sasaki^2,*

¹ Yazaki Corporation, Shizuoka 4101194, Japan

² Toyota Technical Institute, Aichi 4688511, Japan

Materials 2017, 10(9), 1085; https://doi.org/10.3390/ma10091085 - 14 Sep 2017

Cited by 2 | Viewed by 5057

Abstract

The indirect wavelength selective thermal emitter that we have proposed is constructed using a new microheater, demonstrating the enhancement of the emission peak generated by the surface plasmon polariton. The thermal isolation is improved using a 2 μm-thick Si membrane having 3.6 and [...] Read more.

The indirect wavelength selective thermal emitter that we have proposed is constructed using a new microheater, demonstrating the enhancement of the emission peak generated by the surface plasmon polariton. The thermal isolation is improved using a 2 μm-thick Si membrane having 3.6 and 5.4 mm outer diameter. The emission at around the wavelength of the absorption band of CO₂ gas is enhanced. The absorption signal increases, confirming the suitability for gas sensing. Against input power, the intensity at the peak wavelength shows a steeper increasing ratio than the background intensity. The microheater with higher thermal isolation gives larger peak intensity and its increasing ratio against the input power. Full article

(This article belongs to the Special Issue Advance in Plasmonics and Metamaterials)

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14 pages, 2420 KiB

Open AccessArticle

Impact of Source and Manufacturing of Collagen Matrices on Fibroblast Cell Growth and Platelet Aggregation

by Stefanie Böhm¹, Christine Strauß², Stefan Stoiber², Cornelia Kasper^1,2

and Verena Charwat^2,*

¹ Technical Chemistry, Leibniz University Hannover, 30167 Hannover, Germany

² Department of Biotechnology, University of Natural Resources and Life Sciences, 1190 Vienna, Austria

Materials 2017, 10(9), 1086; https://doi.org/10.3390/ma10091086 - 15 Sep 2017

Cited by 36 | Viewed by 7356

Abstract

Collagen is a main component of the extracellular matrix. It is often used in medical applications to support tissue regeneration, hemostasis, or wound healing. Due to different sources of collagen, the properties and performance of available products can vary significantly. In this in [...] Read more.

Collagen is a main component of the extracellular matrix. It is often used in medical applications to support tissue regeneration, hemostasis, or wound healing. Due to different sources of collagen, the properties and performance of available products can vary significantly. In this in vitro study, a comparison of seven different collagen matrices derived from bovine, equine, and porcine sources was performed. As performance indicators, the scaffold function for fibroblasts and platelet aggregation were used. We found strong variation in platelet aggregation and fibroblast growth on the different collagen materials. The observed variations could not be attributed to species differences alone, but were highly dependent on differences in the manufacturing process. Full article

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45 pages, 7590 KiB

Open AccessFeature PaperReview

Hole-Transporting Materials for Printable Perovskite Solar Cells

by Paola Vivo^*

, Jagadish K. Salunke and Arri Priimagi

Laboratory of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere, Finland

Materials 2017, 10(9), 1087; https://doi.org/10.3390/ma10091087 - 15 Sep 2017

Cited by 110 | Viewed by 16943

Abstract

Perovskite solar cells (PSCs) represent undoubtedly the most significant breakthrough in photovoltaic technology since the 1970s, with an increase in their power conversion efficiency from less than 5% to over 22% in just a few years. Hole-transporting materials (HTMs) are an essential building [...] Read more.

Perovskite solar cells (PSCs) represent undoubtedly the most significant breakthrough in photovoltaic technology since the 1970s, with an increase in their power conversion efficiency from less than 5% to over 22% in just a few years. Hole-transporting materials (HTMs) are an essential building block of PSC architectures. Currently, 2,2’,7,7’-tetrakis-(N,N’-di-p-methoxyphenylamine)-9,9’-spirobifluorene), better known as spiro-OMeTAD, is the most widely-used HTM to obtain high-efficiency devices. However, it is a tremendously expensive material with mediocre hole carrier mobility. To ensure wide-scale application of PSC-based technologies, alternative HTMs are being proposed. Solution-processable HTMs are crucial to develop inexpensive, high-throughput and printable large-area PSCs. In this review, we present the most recent advances in the design and development of different types of HTMs, with a particular focus on mesoscopic PSCs. Finally, we outline possible future research directions for further optimization of the HTMs to achieve low-cost, stable and large-area PSCs. Full article

(This article belongs to the Special Issue Highly Ordered Organic Thin Films)

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10 pages, 3548 KiB

Open AccessArticle

Multi-Aperture Shower Design for the Improvement of the Transverse Uniformity of MOCVD-Derived GdYBCO Films

by Ruipeng Zhao¹, Qing Liu¹, Yudong Xia², Fei Zhang³, Yuming Lu⁴, Chuanbing Cai⁴, Bowan Tao^1,* and Yanrong Li¹

¹ State Key Lab of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China

² School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, China

³ Chengdu Fine Optical Engineering Research Center, Chengdu 610041, China

⁴ School of Physics, Shanghai University, Shanghai 200444, China

Materials 2017, 10(9), 1088; https://doi.org/10.3390/ma10091088 - 15 Sep 2017

Cited by 6 | Viewed by 4373

Abstract

A multi-aperture shower design is reported to improve the transverse uniformity of GdYBCO superconducting films on the template of sputtered-LaMnO₃/epitaxial-MgO/IBAD-MgO/solution deposition planarization (SDP)-Y₂O₃-buffered Hastelloy tapes. The GdYBCO films were prepared by the metal organic chemical vapor deposition [...] Read more.

A multi-aperture shower design is reported to improve the transverse uniformity of GdYBCO superconducting films on the template of sputtered-LaMnO₃/epitaxial-MgO/IBAD-MgO/solution deposition planarization (SDP)-Y₂O₃-buffered Hastelloy tapes. The GdYBCO films were prepared by the metal organic chemical vapor deposition (MOCVD) process. The transverse uniformities of structure, morphology, thickness, and performance were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), step profiler, and the standard four-probe method using the criteria of 1 μV/cm, respectively. Through adopting the multi-aperture shower instead of the slit shower, measurement by step profiler revealed that the thickness difference between the middle and the edges based on the slit shower design was well eliminated. Characterization by SEM showed that a GdYBCO film with a smooth surface was successfully prepared. Moreover, the transport critical current density (J_c) of its middle and edge positions at 77 K and self-field were found to be over 5 MA/cm² through adopting the micro-bridge four-probe method. Full article

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14 pages, 15465 KiB

Open AccessArticle

Dynamic Recrystallization of the Constituent γ Phase and Mechanical Properties of Ti-43Al-9V-0.2Y Alloy Sheet

by Yu Zhang^1,2, Xiaopeng Wang², Fantao Kong^1,2,* and Yuyong Chen^1,2,*

¹ State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China

² National Key Laboratory of Science and Technology on Precision Heat Processing of Metals, Harbin Institute of Technology, Harbin 150001, China

Materials 2017, 10(9), 1089; https://doi.org/10.3390/ma10091089 - 15 Sep 2017

Cited by 13 | Viewed by 4900

Abstract

A crack-free Ti-43Al-9V-0.2Y alloy sheet was successfully fabricated via hot-pack rolling at 1200 °C. After hot-rolling, the β/γ lamellar microstructure of the as-forged TiAl alloy was completely converted into a homogeneous duplex microstructure with an average γ grain size of 10.5 μm. The [...] Read more.

A crack-free Ti-43Al-9V-0.2Y alloy sheet was successfully fabricated via hot-pack rolling at 1200 °C. After hot-rolling, the β/γ lamellar microstructure of the as-forged TiAl alloy was completely converted into a homogeneous duplex microstructure with an average γ grain size of 10.5 μm. The dynamic recrystallization (DRX) of the γ phase was systematically investigated. A recrystallization fraction of 62.5% was obtained for the γ phase in the TiAl alloy sheet, when a threshold value of 0.8° was applied to the distribution of grain orientation spread (GOS) values. The high strain rate and high stress associated with hot-rolling are conducive for discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), respectively. A certain high-angle boundary (HAGB: θ = 89° ± 3°<100>), which is associated with DDRX, occurs in both the recrystallized and deformed γ grains. The twin boundaries play an important role in the DDRX of the γ phase. Additionally, the sub-structures and sub-boundaries originating from low-angle boundaries in the deformed grains also indicate that CDRX occurs. The mechanical properties of the alloy sheet were determined at both room and elevated temperatures. At 750 °C, the alloy sheet exhibited excellent elongation (53%), corresponding to a failure strength of 467 MPa. Full article

(This article belongs to the Section Advanced Materials Characterization)

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7 pages, 4174 KiB

Open AccessCommunication

Enhanced Interface Structure and Properties of Titanium Carbonitride-Based Cermets with the Extra Solid Phase Reaction

by Nan Lin^1,*, Yuehui He^2,* and Xiyue Kang²

¹ College of Materials Science and Engineering, Hunan University, Changsha 410082, China

² State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China

Materials 2017, 10(9), 1090; https://doi.org/10.3390/ma10091090 - 15 Sep 2017

Cited by 14 | Viewed by 6219

Abstract

In this paper, the influence of the extra solid phase reaction on the interface structure and mechanical properties of titanium carbonitride-based cermets were investigated. The extra solid phase reaction in the preparation process of cermets could induce the formation of a core/rim/binder interface [...] Read more.

In this paper, the influence of the extra solid phase reaction on the interface structure and mechanical properties of titanium carbonitride-based cermets were investigated. The extra solid phase reaction in the preparation process of cermets could induce the formation of a core/rim/binder interface with the coherent structure and reinforce the interface bonding strength in cermets. The existence of a coherent structure interface can inhibit crack spread and improve the toughness and abrasion resistance of titanium carbonitride-based cermets significantly. Cermets can exhibit the high hardness Rockwell Hardness A (HRA) 92.3, fracture toughness of 11.6 MPa·m^1/2, and transverse rupture strength of 2810 MPa. Full article

(This article belongs to the Section Advanced Materials Characterization)

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16 pages, 32700 KiB

Open AccessArticle

Effects of Pulse Parameters on Weld Microstructure and Mechanical Properties of Extra Pulse Current Aided Laser Welded 2219 Aluminum Alloy Joints

by Xinge Zhang^1,2,*, Liqun Li², Yanbin Chen², Zhaojun Yang¹, Yanli Chen¹ and Xinjian Guo²

¹ School of Mechanical Science and Engineering, Jilin University, Changchun 130025, China

² State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China

Materials 2017, 10(9), 1091; https://doi.org/10.3390/ma10091091 - 15 Sep 2017

Cited by 17 | Viewed by 6147

Abstract

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The [...] Read more.

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The effect mechanisms of the pulse current interactions with the weld pool were evaluated. The results indicated that the coarse dendritic structure in the weld zone changed to a fine equiaxed structure using an extra pulse current, and the pulse parameters, including medium peak current, relatively high pulse frequency, and low pulse duty ratio benefited to improving the weld structure. The effect mechanisms of the pulse current were mainly ascribed to the magnetic pinch effect, thermal effect, and electromigration effect caused by the pulse current. The effect of the pulse parameters on the mechanical properties of welded joints were consistent with that of the weld microstructure. The tensile strength and elongation of the optimal pulse current-aided laser-welded joint increased by 16.4% and 105%, respectively, compared with autogenous laser welding. Full article

(This article belongs to the Special Issue Laser Materials Processing)

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15 pages, 2256 KiB

Open AccessFeature PaperArticle

N-Doped Carbon Xerogels as Pt Support for the Electro-Reduction of Oxygen

by Cinthia Alegre^1,2, David Sebastián^1,*

, María E. Gálvez³, Estela Baquedano¹, Rafael Moliner¹, Antonino S. Aricò², Vincenzo Baglio^2,*

and María J. Lázaro¹

¹ Instituto de Carboquímica, Consejo Superior de Investigaciones Científicas (CSIC), C/Miguel Luesma Castán 4, 50018 Zaragoza, Spain

² Istituto di Tecnologie Avanzate per l’Energia “Nicola Giordano”, Consiglio Nazionale delle Ricerche (CNR), Salita Santa Lucia sopra Contesse, 5, 98126 Messina, Italy

³ Sorbonne Universités, Universite Pierre et Marie Curie (UPMC) Paris, Institut Jean le Rond D’Alembert, UMR CNRS 7190, 78210 Saint-Cyr L’Ecole, France

Materials 2017, 10(9), 1092; https://doi.org/10.3390/ma10091092 - 17 Sep 2017

Cited by 31 | Viewed by 6267

Abstract

Durability and limited catalytic activity are key impediments to the commercialization of polymer electrolyte fuel cells. Carbon materials employed as catalyst support can be doped with different heteroatoms, like nitrogen, to improve both catalytic activity and durability. Carbon xerogels are nanoporous carbons that [...] Read more.

Durability and limited catalytic activity are key impediments to the commercialization of polymer electrolyte fuel cells. Carbon materials employed as catalyst support can be doped with different heteroatoms, like nitrogen, to improve both catalytic activity and durability. Carbon xerogels are nanoporous carbons that can be easily synthesized in order to obtain N-doped materials. In the present work, we introduced melamine as a carbon xerogel precursor together with resorcinol for an effective in-situ N doping (3–4 wt % N). Pt nanoparticles were supported on nitrogen-doped carbon xerogels and their activity for the oxygen reduction reaction (ORR) was evaluated in acid media along with their stability. Results provide new evidences of the type of N groups aiding the activity of Pt for the ORR and of a remarkable stability for N-doped carbon-supported Pt catalysts, providing appropriate physico-chemical features. Full article

(This article belongs to the Special Issue Advanced Materials in Polymer Electrolyte Fuel Cells)

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8 pages, 1562 KiB

Open AccessArticle

Large Electrocaloric Effect in Lead-Free (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ Ceramics Prepared via Citrate Route

by Jing Shi^1,2, Rongfeng Zhu¹, Xing Liu³, Bijun Fang^1,*, Ningyi Yuan¹, Jianning Ding^1,4,* and Haosu Luo^5,*

¹ School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovolatic Science and Engineering, Jiangsu Province Cultivation Base for State Key Laboratory of Photovoltaic Science and Technology, National Experimental Demonstration Center for Materials Science and Engineering, Changzhou University, Changzhou 213164, China

² Institute of Electronic and Electrical, Changzhou College of Information Technology, Changzhou 213164, China

³ School of Materials Science and Engineering, Tongji University, Shanghai 201804, China

⁴ School of Material Science and Engineering, Jiangsu University, Zhenjiang 212013, China

⁵ Key Laboratory of Inorganic Function Material and Device, Chinese Academy of Sciences, Shanghai 201800, China

Materials 2017, 10(9), 1093; https://doi.org/10.3390/ma10091093 - 18 Sep 2017

Cited by 34 | Viewed by 5796

Abstract

The 1 wt % Li-doped (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT-Li) ceramics prepared by the citrate method exhibit improved phase purity, densification and electrical properties, which provide prospective possibility to develop high-performance electrocaloric materials. The electrocaloric effect was [...] Read more.

The 1 wt % Li-doped (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT-Li) ceramics prepared by the citrate method exhibit improved phase purity, densification and electrical properties, which provide prospective possibility to develop high-performance electrocaloric materials. The electrocaloric effect was evaluated by phenomenological method, and the BCZT-Li ceramics present large electrocaloric temperature change ∆T, especially large electrocaloric responsibility ξ = ∆T_max/∆E_max, which can be comparable to the largest values reported in the lead-free piezoelectric ceramics. The excellent electrocaloric effect is considered as correlating with the coexistence of polymorphic ferroelectric phases, which are detected by the Raman spectroscopy. The large ξ value accompanied by decreased Curie temperature (around 73 °C) of the BCZT-Li ceramics prepared by the citrate method presents potential applications as the next-generation solid-state cooling devices. Full article

(This article belongs to the Section Energy Materials)

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13 pages, 1853 KiB

Open AccessArticle

Expanding the Applicability of Poly(Ionic Liquids) in Solid Phase Microextraction: Pyrrolidinium Coatings

by David J. S. Patinha^1,2, Liliana C. Tomé¹

, Mehmet Isik³

, David Mecerreyes^3,4

, Armando J. D. Silvestre^2,*

and Isabel M. Marrucho^1,2,5,*

¹ Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. Da República, 2780-157 Oeiras, Portugal

² CICECO—Aveiro Institute of Materials and Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal

³ POLYMAT, University of the Basque Country UPV/EHU, Joxe Mari Korta Center, Avda. Tolosa 72, 20018 Donostia-San Sebastian, Spain

⁴ IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain

⁵ Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisboa, Portugal

Materials 2017, 10(9), 1094; https://doi.org/10.3390/ma10091094 - 18 Sep 2017

Cited by 15 | Viewed by 4819

Abstract

Crosslinked pyrrolidinium-based poly(ionic liquids) (Pyrr-PILs) were synthesized through a fast, simple, and solventless photopolymerization scheme, and tested as solid phase microextraction (SPME) sorbents. A series of Pyrr-PILs bearing three different alkyl side chain lengths with two, eight, and fourteen carbons was prepared, characterized, [...] Read more.

Crosslinked pyrrolidinium-based poly(ionic liquids) (Pyrr-PILs) were synthesized through a fast, simple, and solventless photopolymerization scheme, and tested as solid phase microextraction (SPME) sorbents. A series of Pyrr-PILs bearing three different alkyl side chain lengths with two, eight, and fourteen carbons was prepared, characterized, and homogeneously coated on a steel wire by using a very simple procedure. The resulting coatings showed a high thermal stability, with decomposition temperatures above 350 °C, excellent film stability, and lifetime of over 100 injections. The performance of these PIL-based SPME fibers was evaluated using a mixture of eleven organic compounds with different molar volumes and chemical functionalities (alcohols, ketones, and monoterpenes). The Pyrr-PIL fibers were obtained as dense film coatings, with 67 μm thickness, with an overall sorption increase of 90% and 55% as compared to commercial fibers of Polyacrylate (85 μm) (PA85) and Polydimethylsiloxane (7 μm) (PDMS7) coatings, respectively. A urine sample doped with the sample mixture was used to study the matrix effect and establish relative recoveries, which ranged from 60.2% to 104.1%. Full article

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32 pages, 6127 KiB

Open AccessFeature PaperReview

Carrier Multiplication Mechanisms and Competing Processes in Colloidal Semiconductor Nanostructures

by Stephen V. Kershaw^* and Andrey L. Rogach

Department of Materials Science and Engineering and Centre for Functional Photonics (CFP), City University of Hong Kong, Hong Kong S.A.R., China

Materials 2017, 10(9), 1095; https://doi.org/10.3390/ma10091095 - 18 Sep 2017

Cited by 23 | Viewed by 7916

Abstract

Quantum confined semiconductor nanoparticles, such as colloidal quantum dots, nanorods and nanoplatelets have broad extended absorption spectra at energies above their bandgaps. This means that they can absorb light at high photon energies leading to the formation of hot excitons with finite excited [...] Read more.

Quantum confined semiconductor nanoparticles, such as colloidal quantum dots, nanorods and nanoplatelets have broad extended absorption spectra at energies above their bandgaps. This means that they can absorb light at high photon energies leading to the formation of hot excitons with finite excited state lifetimes. During their existence, the hot electron and hole that comprise the exciton may start to cool as they relax to the band edge by phonon mediated or Auger cooling processes or a combination of these. Alongside these cooling processes, there is the possibility that the hot exciton may split into two or more lower energy excitons in what is termed carrier multiplication (CM). The fission of the hot exciton to form lower energy multiexcitons is in direct competition with the cooling processes, with the timescales for multiplication and cooling often overlapping strongly in many materials. Once CM has been achieved, the next challenge is to preserve the multiexcitons long enough to make use of the bonus carriers in the face of another competing process, non-radiative Auger recombination. However, it has been found that Auger recombination and the several possible cooling processes can be manipulated and usefully suppressed or retarded by engineering the nanoparticle shape, size or composition and by the use of heterostructures, along with different choices of surface treatments. This review surveys some of the work that has led to an understanding of the rich carrier dynamics in semiconductor nanoparticles, and that has started to guide materials researchers to nanostructures that can tilt the balance in favour of efficient CM with sustained multiexciton lifetimes. Full article

(This article belongs to the Special Issue Colloidal Quantum Dots)

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11 pages, 3090 KiB

Open AccessArticle

Can More Nanoparticles Induce Larger Viscosities of Nanoparticle-Enhanced Wormlike Micellar System (NEWMS)?

by Mingwei Zhao, Yue Zhang, Chenwei Zou, Caili Dai^*, Mingwei Gao, Yuyang Li, Wenjiao Lv, Jianfeng Jiang and Yining Wu^*

State Key Laboratory of Heavy Oil Processing, School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China

Materials 2017, 10(9), 1096; https://doi.org/10.3390/ma10091096 - 18 Sep 2017

Cited by 39 | Viewed by 5861

Abstract

There have been many reports about the thickening ability of nanoparticles on the wormlike micelles in the recent years. Through the addition of nanoparticles, the viscosity of wormlike micelles can be increased. There still exists a doubt: can viscosity be increased further by [...] Read more.

There have been many reports about the thickening ability of nanoparticles on the wormlike micelles in the recent years. Through the addition of nanoparticles, the viscosity of wormlike micelles can be increased. There still exists a doubt: can viscosity be increased further by adding more nanoparticles? To answer this issue, in this work, the effects of silica nanoparticles and temperature on the nanoparticles-enhanced wormlike micellar system (NEWMS) were studied. The typical wormlike micelles (wormlike micelles) are prepared by 50 mM cetyltrimethyl ammonium bromide (CTAB) and 60 mM sodium salicylate (NaSal). The rheological results show the increase of viscoelasticity in NEWMS by adding nanoparticles, with the increase of zero-shear viscosity and relaxation time. However, with the further increase of nanoparticles, an interesting phenomenon appears. The zero-shear viscosity and relaxation time reach the maximum and begin to decrease. The results show a slight increasing trend for the contour length of wormlike micelles by adding nanoparticles, while no obvious effect on the entanglement and mesh size. In addition, with the increase of temperature, remarkable reduction of contour length and relaxation time can be observed from the calculation. NEWMS constantly retain better viscoelasticity compared with conventional wormlike micelles without silica nanoparticles. According to the Arrhenius equation, the activation energy E_a shows the same increase trend of NEWMS. Finally, a mechanism is proposed to explain this interesting phenomenon. Full article

(This article belongs to the Section Advanced Materials Characterization)

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16 pages, 5107 KiB

Open AccessArticle

Towards an Ultrasonic Guided Wave Procedure for Health Monitoring of Composite Vessels: Application to Hydrogen-Powered Aircraft

by Slah Yaacoubi^1,*, Peter McKeon², Weina Ke¹, Nico F. Declercq² and Fethi Dahmene¹

¹ Institut de Soudure, 4 Bvd Henri Becquerel, Espace Cormontaigne, 57970 Yutz, France

² Unité Mixte Internationale Georgia Tech—CNRS 2958, George W. Woodruff School of Mechanical Engineering, Metz Technopole, 2 Rue Marconi, 57070 Metz, France

Materials 2017, 10(9), 1097; https://doi.org/10.3390/ma10091097 - 19 Sep 2017

Cited by 16 | Viewed by 5919

Abstract

This paper presents an overview and description of the approach to be used to investigate the behavior and the defect sensitivity of various ultrasonic guided wave (UGW) modes propagating specifically in composite cylindrical vessels in the framework of the safety of hydrogen energy [...] Read more.

This paper presents an overview and description of the approach to be used to investigate the behavior and the defect sensitivity of various ultrasonic guided wave (UGW) modes propagating specifically in composite cylindrical vessels in the framework of the safety of hydrogen energy transportation such as hydrogen-powered aircrafts. These structures which consist of thick and multi-layer composites are envisioned for housing hydrogen gas at high pressures. Due to safety concerns associated with a weakened structure, structural health monitoring techniques are needed. A procedure for optimizing damage detection in these structural types is presented. It is shown that a finite element method can help identify useful experimental parameters including frequency range, excitation type, and receiver placement. Full article

(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)

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15 pages, 5933 KiB

Open AccessArticle

On the Role of Processing Parameters in Producing Recycled Aluminum AA6061 Based Metal Matrix Composite (MMC-Al_R) Prepared Using Hot Press Forging (HPF) Process

by Azlan Ahmad^*, Mohd Amri Lajis and Nur Kamilah Yusuf

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

Materials 2017, 10(9), 1098; https://doi.org/10.3390/ma10091098 - 19 Sep 2017

Cited by 23 | Viewed by 8219

Abstract

Solid-state recycling, which involves the direct recycling of scrap metal into bulk material using severe plastic deformation, has emerged as a potential alternative to the conventional remelting and recycling techniques. Hot press forging has been identified as a sustainable direct recycling technique that [...] Read more.

Solid-state recycling, which involves the direct recycling of scrap metal into bulk material using severe plastic deformation, has emerged as a potential alternative to the conventional remelting and recycling techniques. Hot press forging has been identified as a sustainable direct recycling technique that has fewer steps and maintains excellent material performance. An experimental investigation was conducted to explore the hardness and density of a recycled aluminum-based metal matrix composite by varying operating temperature and holding time. A mixture of recycled aluminum, AA6061, and aluminum oxide were simultaneously heated to 430, 480, and 530 °C and forged for 60, 90, and 120 min. We found a positive increase in microhardness and density for all composites. The hardness increased approximately 33.85%, while density improved by about 15.25% whenever the temperature or the holding time were increased. Based on qualitative analysis, the composite endures substantial plastic deformation due to the presence of hardness properties due to the aluminum oxide embedded in the aluminum matrix. These increases were significantly affected by the operating temperature; the holding time also had a subordinate role in enhancing the metal matrix composite properties. Furthermore, in an effort to curb the shortage of primary resources, this study reviewed the promising performance of secondary resources produced by using recycled aluminum and aluminum oxide as the base matrix and reinforcement constituent, respectively. This study is an outline for machining practitioners and the manufacturing industry to help increase industry sustainability with the aim of preserving the Earth for our community in the future. Full article

(This article belongs to the Special Issue Recycled Materials, Eco-design and 3D Printing)

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15 pages, 5107 KiB

Open AccessArticle

Strengthening of Existing Bridge Structures for Shear and Bending with Carbon Textile-Reinforced Mortar

by Martin Herbrand^*, Viviane Adam

, Martin Classen, Dominik Kueres and Josef Hegger

Institute of Structural Concrete, RWTH Aachen University, 52056 Aachen, Germany

Materials 2017, 10(9), 1099; https://doi.org/10.3390/ma10091099 - 19 Sep 2017

Cited by 58 | Viewed by 7837

Abstract

Increasing traffic loads and changes in code provisions lead to deficits in shear and flexural capacity of many existing highway bridges. Therefore, a large number of structures are expected to require refurbishment and strengthening in the future. This projection is based on the [...] Read more.

Increasing traffic loads and changes in code provisions lead to deficits in shear and flexural capacity of many existing highway bridges. Therefore, a large number of structures are expected to require refurbishment and strengthening in the future. This projection is based on the current condition of many older road bridges. Different strengthening methods for bridges exist to extend their service life, all having specific advantages and disadvantages. By applying a thin layer of carbon textile-reinforced mortar (CTRM) to bridge deck slabs and the webs of pre-stressed concrete bridges, the fatigue and ultimate strength of these members can be increased significantly. The CTRM layer is a combination of a corrosion resistant carbon fiber reinforced polymer (CFRP) fabric and an efficient mortar. In this paper, the strengthening method and the experimental results obtained at RWTH Aachen University are presented. Full article

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14 pages, 4591 KiB

Open AccessArticle

Precipitation Behavior and Quenching Sensitivity of a Spray Deposited Al-Zn-Mg-Cu-Zr Alloy

by Xiaofei Sheng^1,2

, Qian Lei^1,3,*, Zhu Xiao¹ and Mingpu Wang¹

¹ School of Materials Science and Engineering, Central South University, Changsha 410083, China

² School of Materials Science and Engineering, Hubei University of Automotive Technology, Shiyan 442002, China

³ Department of Materials Science and Engineering, College of Engineering, University of Michigan, Ann Arbor, MI 48109, USA

Materials 2017, 10(9), 1100; https://doi.org/10.3390/ma10091100 - 19 Sep 2017

Cited by 12 | Viewed by 5418

Abstract

Precipitation behavior and the quenching sensitivity of a spray deposited Al-Zn-Mg-Cu-Zr alloy during isothermal heat treatment have been studied systematically. Results demonstrate that both the hardness and the ultimate tensile strength of the studied alloy decreased with the isothermal treatment time at certain [...] Read more.

Precipitation behavior and the quenching sensitivity of a spray deposited Al-Zn-Mg-Cu-Zr alloy during isothermal heat treatment have been studied systematically. Results demonstrate that both the hardness and the ultimate tensile strength of the studied alloy decreased with the isothermal treatment time at certain temperatures. More notably, the hardness decreases rapidly after the isothermal heat treatment. During isothermal heat treatment processing, precipitates readily nucleated in the medium-temperature zone (250–400 °C), while the precipitation nucleation was scarce in the low-temperature zone (<250 °C) and in the high-temperature zone (>400 °C). Precipitates with sizes of less than ten nanometers would contribute a significant increase in yield strength, while the ones with a larger size than 300 nm would contribute little strengthening effect. Quenching sensitivity is high in the medium-temperature zone (250–400 °C), and corresponding time-temperature-property (TTP) curves of the studied alloy have been established. Full article

(This article belongs to the Section Advanced Materials Characterization)

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10 pages, 3280 KiB

Open AccessArticle

Modification of 13X Molecular Sieve by Chitosan for Adsorptive Removal of Cadmium from Simulated Wastewater

by Yan Shi¹, Ken Sun¹, Lixin Huo¹, Xiuxiu Li², Xuebin Qi^3,* and Zhaohui Li^4,*

¹ School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450045, China

² Henan Province key Laboratory of Water-Saving Agriculture, North China University of Water Resources and Electric Power, Zhengzhou 450045, China

³ Farmland Irrigation Research Institute, CAAS, Xinxiang 453002, China

⁴ Geosciences Department, University of Wisconsin—Parkside, Kenosha, WI 53144, USA

Materials 2017, 10(9), 1101; https://doi.org/10.3390/ma10091101 - 19 Sep 2017

Cited by 8 | Viewed by 4724

Abstract

Chitosan was used to modify a 13X molecular sieve to improve its cadmium removal capability. After being modified with 2% chitosan-acetate for 2 h at 30 °C, significant uptake of Cd²⁺ could be achieved. The uptake of Cd²⁺ on the modified [...] Read more.

Chitosan was used to modify a 13X molecular sieve to improve its cadmium removal capability. After being modified with 2% chitosan-acetate for 2 h at 30 °C, significant uptake of Cd²⁺ could be achieved. The uptake of Cd²⁺ on the modified 13X molecular sieve followed the Langmuir isotherms with a capacity of 1 mg/g. The kinetics of Cd²⁺ removal by modified 13X molecular sieve followed a pseudo second-order reaction, suggesting chemisorption or surface complexation. The Cd²⁺ removal with a sorbent dose of 2 g/L from an initial concentration of 100 μg/L reached more than 95% in 90 min. The equilibrium Cd²⁺ concentration was <5 μg/L, which meets the requirements of “Standards for Irrigation Water Quality” (GB5084-2005) (10 μg/L) and MCL and MCLG for groundwater and drinking water (5 μg/L) set by United States Environmental Protection Agency. Full article

(This article belongs to the Special Issue Advances in Pillared Clays and Similar Materials: Synthesis, Characterization and Applications)

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13 pages, 9217 KiB

Open AccessArticle

Superplastic Deformation Mechanisms of Superfine/Nanocrystalline Duplex PM-TiAl-Based Alloy

by Xuebo Gong, Zhenxin Duan, Wen Pei and Hua Chen^*

School of Materials Science and Engineering, Changchun University of Technology, Changchun 130012, China

Materials 2017, 10(9), 1103; https://doi.org/10.3390/ma10091103 - 19 Sep 2017

Cited by 11 | Viewed by 4603

Abstract

In this paper, the equiaxed superfine/nanocrystalline duplex PM-TiAl-based alloy with (γ + α₂) microstructure, Ti-45Al-5Nb (at %), has been synthesized by high-energy ball milling and vacuum hot pressing sintering. Superplastic deformation behavior has been investigated at 1000 °C and 1050 °C [...] Read more.

In this paper, the equiaxed superfine/nanocrystalline duplex PM-TiAl-based alloy with (γ + α₂) microstructure, Ti-45Al-5Nb (at %), has been synthesized by high-energy ball milling and vacuum hot pressing sintering. Superplastic deformation behavior has been investigated at 1000 °C and 1050 °C with strain rates from 5 × 10⁻⁵ s⁻¹ to 1 × 10⁻³ s⁻¹. The effects of deformation on the microstructure and mechanical behaviors of high Nb containing TiAl alloy have been characterized and analyzed. The results showed that, the ultimate tensile strength of the alloy was 58.7 MPa at 1000 °C and 10.5 MPa at 1050 °C with a strain rate of 5 × 10⁻⁵ s⁻¹, while the elongation was 121% and 233%, respectively. The alloy exhibited superplastic elongation at 1000 and 1050 °C with an exponent (m) of 0.48 and 0.45. The main softening mechanism was dynamic recrystallization of γ grains; the dislocation slip and γ/γ interface twinning were responsible for superplastic deformation. The orientation relationship of γ/γ interface twinning obeyed the classical one: (001)_γ//(110)_γ. Full article

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13 pages, 4269 KiB

Open AccessFeature PaperArticle

A Method for Medical Diagnosis Based on Optical Fluence Rate Distribution at Tissue Surface

by Omnia Hamdy^1,*, Jala El-Azab¹, Tarek A. Al-Saeed², Mahmoud F. Hassan³ and Nahed H. Solouma^1,4

¹ Department of Engineering Applications of Laser, National Institute of Laser Enhanced Sciences (NILES), Cairo University, Giza Governorate 12613, Egypt

² Department of Biomedical Engineering, Faculty of Engineering, Helwan University, Cairo Governorate 11795, Egypt

³ Department of Basic Sciences, Faculty of Engineering, Benha University, Qalubiya Governorate 13511, Egypt

⁴ Department of Biomedical Engineering, Faculty of Engineering, King Faisal University, Al-Ahsa 31982, Saudi Arabia

Materials 2017, 10(9), 1104; https://doi.org/10.3390/ma10091104 - 20 Sep 2017

Cited by 34 | Viewed by 6058

Abstract

Optical differentiation is a promising tool in biomedical diagnosis mainly because of its safety. The optical parameters’ values of biological tissues differ according to the histopathology of the tissue and hence could be used for differentiation. The optical fluence rate distribution on tissue [...] Read more.

Optical differentiation is a promising tool in biomedical diagnosis mainly because of its safety. The optical parameters’ values of biological tissues differ according to the histopathology of the tissue and hence could be used for differentiation. The optical fluence rate distribution on tissue boundaries depends on the optical parameters. So, providing image displays of such distributions can provide a visual means of biomedical diagnosis. In this work, an experimental setup was implemented to measure the spatially-resolved steady state diffuse reflectance and transmittance of native and coagulated chicken liver and native and boiled breast chicken skin at 635 and 808 nm wavelengths laser irradiation. With the measured values, the optical parameters of the samples were calculated in vitro using a combination of modified Kubelka-Munk model and Bouguer-Beer-Lambert law. The estimated optical parameters values were substituted in the diffusion equation to simulate the fluence rate at the tissue surface using the finite element method. Results were verified with Monte-Carlo simulation. The results obtained showed that the diffuse reflectance curves and fluence rate distribution images can provide discrimination tools between different tissue types and hence can be used for biomedical diagnosis. Full article

(This article belongs to the Special Issue Laser in Nanotechnology and Biomedical Applications)

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20 pages, 59767 KiB

Open AccessArticle

Nanocrystalline Al7075 + 1 wt % Zr Alloy Prepared Using Mechanical Milling and Spark Plasma Sintering

by Orsolya Molnárová^1,*

, Přemysl Málek¹, Jozef Veselý¹

, Michaela Šlapáková¹

, Peter Minárik¹, František Lukáč^2,3

, Tomáš Chráska³

, Pavel Novák⁴ and Filip Průša⁴

¹ Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague 12116, Czech Republic

² Department of Low-Temperature Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, Prague 18000, Czech Republic

³ Institute of Plasma Physics of the CAS, Za Slovankou 1782/3, Prague 18200, Czech Republic

⁴ Department of Metals and Corrosion Engineering, UCT Prague, Technická 5, Prague 16628, Czech Republic

Materials 2017, 10(9), 1105; https://doi.org/10.3390/ma10091105 - 20 Sep 2017

Cited by 6 | Viewed by 6168

Abstract

The microstructure, phase composition, and microhardness of both gas-atomized and mechanically milled powders of the Al7075 + 1 wt % Zr alloy were investigated. The gas-atomized powder exhibited a cellular microstructure (grain size of a few µm) with layers of intermetallic phases along [...] Read more.

The microstructure, phase composition, and microhardness of both gas-atomized and mechanically milled powders of the Al7075 + 1 wt % Zr alloy were investigated. The gas-atomized powder exhibited a cellular microstructure (grain size of a few µm) with layers of intermetallic phases along the cell boundaries. Mechanical milling (400 revolutions per minute (RPM)/8 h) resulted in a grain size reduction to the nanocrystalline range (20 to 100 nm) along with the dissolution of the intermetallic phases. Milling led to an increase in the powder’s microhardness from 97 to 343 HV. Compacts prepared by spark plasma sintering (SPS) exhibited negligible porosity. The grain size of the originally gas-atomized material was retained, but the continuous layers of intermetallic phases were replaced by individual particles. Recrystallization led to a grain size increase to 365 nm in the SPS compact prepared from the originally milled powder. Small precipitates of the Al₃Zr phase were observed in the SPS compacts, and they are believed to be responsible for the retainment of the sub-microcrystalline microstructure during SPS. A more intensive precipitation in this SPS compact can be attributed to a faster diffusion due to a high density of dislocations and grain boundaries in the milled powder. Full article

(This article belongs to the Section Advanced Materials Characterization)

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Open AccessArticle

Microstructural Investigation of Heat-Treated Ultra-High Performance Concrete for Optimum Production

by Sung-Hoon Kang^1,2, Ji-Hyung Lee¹, Sung-Gul Hong^1,* and Juhyuk Moon^2,*

¹ Department of Architecture & Architectural Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea

² Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore 117576, Singapore

Materials 2017, 10(9), 1106; https://doi.org/10.3390/ma10091106 - 20 Sep 2017

Cited by 92 | Viewed by 7255

Abstract

For optimum production of ultra-high performance concrete (UHPC), the material and microstructural properties of UHPC cured under various heat treatment (HT) conditions are studied. The effects of HT temperature and duration on the hydration reaction, microstructure, and mechanical properties of UHPC are investigated. [...] Read more.

For optimum production of ultra-high performance concrete (UHPC), the material and microstructural properties of UHPC cured under various heat treatment (HT) conditions are studied. The effects of HT temperature and duration on the hydration reaction, microstructure, and mechanical properties of UHPC are investigated. Increasing HT temperature accelerates both cement hydration and pozzolanic reaction, but the latter is more significantly affected. This accelerated pozzolanic reaction in UHPC clearly enhances compressive strength. However, strength after the HT becomes stable as most of the hydration finishes during the HT period. Particularly, it was concluded that the mechanical benefit of the increased temperature and duration on the 28 day-strength is not noticeable when the HT temperature is above 60 °C (with a 48 h duration) or the HT duration is longer than 12 h (with 90 °C temperature). On the other hand, even with a minimal HT condition such as 1 day at 60 °C or 12 h at 90 °C, outstanding compressive strength of 179 MPa and flexural tensile strength of 49 MPa are achieved at 28 days. Microstructural investigation conducted herein suggests that portlandite content can be a good indicator for the mechanical performance of UHPC regardless of its HT curing conditions. These findings can contribute to reducing manufacturing energy consumption, cost, and environmental impact in the production of UHPC and be helpful for practitioners to better understand the effect of HT on UHPC and optimize its production. Full article

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Materials, Volume 10, Issue 9 (September 2017) – 125 articles

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