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Materials, Volume 10, Issue 11 (November 2017)

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Cover Story The cover image depicts the results of a new approach to model particle–wall interactions that [...] Read more.
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Open AccessArticle Surface Modification of Direct-Current and Radio-Frequency Oxygen Plasma Treatments Enhance Cell Biocompatibility
Materials 2017, 10(11), 1223; doi:10.3390/ma10111223
Received: 7 September 2017 / Revised: 22 October 2017 / Accepted: 23 October 2017 / Published: 25 October 2017
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Abstract
The sand-blasting and acid etching (SLA) method can fabricate a rough topography for mechanical fixation and long-term stability of titanium implant, but can not achieve early bone healing. This study used two kinds of plasma treatments (Direct-Current and Radio-Frequency plasma) to modify the
[...] Read more.
The sand-blasting and acid etching (SLA) method can fabricate a rough topography for mechanical fixation and long-term stability of titanium implant, but can not achieve early bone healing. This study used two kinds of plasma treatments (Direct-Current and Radio-Frequency plasma) to modify the SLA-treated surface. The modification of plasma treatments creates respective power range and different content functional OH groups. The results show that the plasma treatments do not change the micron scale topography, and plasma-treated specimens presented super hydrophilicity. The X-ray photoelectron spectroscopy (XPS)-examined result showed that the functional OH content of the RF plasma-treated group was higher than the control (SLA) and DC treatment groups. The biological responses (protein adsorption, cell attachment, cell proliferation, and differentiation) promoted after plasma treatments, and the cell responses, have correlated to the total content of amphoteric OH groups. The experimental results indicated that plasma treatments can create functional OH groups on SLA-treated specimens, and the RF plasma-treated SLA implant thus has potential for achievement of bone healing in early stage of implantation. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Effect of Dentin Wetness on the Bond Strength of Universal Adhesives
Materials 2017, 10(11), 1224; doi:10.3390/ma10111224
Received: 26 September 2017 / Revised: 20 October 2017 / Accepted: 23 October 2017 / Published: 25 October 2017
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Abstract
The effects of dentin wetness on the bond strength and adhesive interface morphology of universal adhesives have been investigated using micro-tensile bond strength (μTBS) testing and confocal laser scanning microscopy (CLSM). Seventy-two human third molars were wet ground to expose flat dentin surfaces.
[...] Read more.
The effects of dentin wetness on the bond strength and adhesive interface morphology of universal adhesives have been investigated using micro-tensile bond strength (μTBS) testing and confocal laser scanning microscopy (CLSM). Seventy-two human third molars were wet ground to expose flat dentin surfaces. They were divided into three groups according to the air-drying time of the dentin surfaces: 0 (without air drying), 5, and 10 s. The dentin surfaces were then treated with three universal adhesives: G-Premio Bond, Single Bond Universal, and All-Bond Universal in self-etch or etch-and-rinse mode. After composite build up, a μTBS test was performed. One additional tooth was prepared for each group by staining the adhesives with 0.01 wt % of Rhodamine B fluorescent dye for CLSM analysis. The data were analyzed statistically using ANOVA and Tukey’s post hoc tests (α = 0.05). Two-way ANOVA showed significant differences among the adhesive systems and dentin moisture conditions. An interaction effect was also observed (p < 0.05). One-way ANOVA showed that All-Bond Universal was the only material influenced by the wetness of the dentin surfaces. Wetness of the dentin surface is a factor influencing the micro-tensile bond strength of universal adhesives. Full article
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Open AccessArticle Analyzing and Modelling the Corrosion Behavior of Ni/Al2O3, Ni/SiC, Ni/ZrO2 and Ni/Graphene Nanocomposite Coatings
Materials 2017, 10(11), 1225; doi:10.3390/ma10111225
Received: 28 September 2017 / Revised: 16 October 2017 / Accepted: 21 October 2017 / Published: 25 October 2017
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Abstract
A study has been presented on the effects of intrinsic mechanical parameters, such as surface stress, surface elastic modulus, surface porosity, permeability and grain size on the corrosion failure of nanocomposite coatings. A set of mechano-electrochemical equations was developed by combining the popular
[...] Read more.
A study has been presented on the effects of intrinsic mechanical parameters, such as surface stress, surface elastic modulus, surface porosity, permeability and grain size on the corrosion failure of nanocomposite coatings. A set of mechano-electrochemical equations was developed by combining the popular Butler–Volmer and Duhem expressions to analyze the direct influence of mechanical parameters on the electrochemical reactions in nanocomposite coatings. Nanocomposite coatings of Ni with Al2O3, SiC, ZrO2 and Graphene nanoparticles were studied as examples. The predictions showed that the corrosion rate of the nanocoatings increased with increasing grain size due to increase in surface stress, surface porosity and permeability of nanocoatings. A detailed experimental study was performed in which the nanocomposite coatings were subjected to an accelerated corrosion testing. The experimental results helped to develop and validate the equations by qualitative comparison between the experimental and predicted results showing good agreement between the two. Full article
(This article belongs to the Special Issue Wear-Corrosion Synergy, Nanocoating and Control of Materials)
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Open AccessArticle High Thermal Conductivity of Copper Matrix Composite Coatings with Highly-Aligned Graphite Nanoplatelets
Materials 2017, 10(11), 1226; doi:10.3390/ma10111226
Received: 7 September 2017 / Revised: 18 October 2017 / Accepted: 23 October 2017 / Published: 25 October 2017
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Abstract
Nanocomposite coatings with highly-aligned graphite nanoplatelets in a copper matrix were successfully fabricated by electrodeposition. For the first time, the disposition and thermal conductivity of the nanofiller has been evaluated. The degree of alignment and inclination of the filling materials has been quantitatively
[...] Read more.
Nanocomposite coatings with highly-aligned graphite nanoplatelets in a copper matrix were successfully fabricated by electrodeposition. For the first time, the disposition and thermal conductivity of the nanofiller has been evaluated. The degree of alignment and inclination of the filling materials has been quantitatively evaluated by polarized micro-Raman spectroscopy. The room temperature values of the thermal conductivity were extracted for the graphite nanoplatelets by the dependence of the Raman G-peak frequency on the laser power excitation. Temperature dependency of the G-peak shift has been also measured. Most remarkable is the global thermal conductivity of 640 ± 20 W·m−1·K−1 (+57% of copper) obtained for the composite coating by the flash method. Our experimental results are accounted for by an effective medium approximation (EMA) model that considers the influence of filler geometry, orientation, and thermal conductivity inside a copper matrix. Full article
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Open AccessArticle Effects of Hot-Hydrostatic Canned Extrusion on the Stock Utilization, Microstructure and Mechanical Properties of TiBw/TC4 Composites with Quasi-Continuous Network
Materials 2017, 10(11), 1227; doi:10.3390/ma10111227
Received: 1 October 2017 / Revised: 19 October 2017 / Accepted: 20 October 2017 / Published: 25 October 2017
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Abstract
In-situ TiB whisker-reinforced Ti–6Al–4V (TC4) titanium matrix composites (TiBw/TC4) with quasi-continuous networks were successfully fabricated by vacuum hot-pressing sintering. The effects of the hot-hydrostatic canned extrusion on stock utilization, microstructure and mechanical properties of the TiBw/TC4 composites were investigated. It was satisfactory that
[...] Read more.
In-situ TiB whisker-reinforced Ti–6Al–4V (TC4) titanium matrix composites (TiBw/TC4) with quasi-continuous networks were successfully fabricated by vacuum hot-pressing sintering. The effects of the hot-hydrostatic canned extrusion on stock utilization, microstructure and mechanical properties of the TiBw/TC4 composites were investigated. It was satisfactory that the utilization of composites could be obviously improved by canned extrusion compared to that extruded without canned extrusion. The microstructure results showed that after canned extrusion the grain was refined and the TiB whiskers were distributed from a random array state to a state in which the whiskers were distributed along the extrusion direction. The properties testing results revealed that the tensile strength, the hardness and the ductility of the composites all significantly improved after extrusion due to the grain refinement and orientation of the TiB whisker caused by extrusion. Tensile fracture results showed that when the TiB whiskers were randomly distributed only part of them played a role in strengthening the matrix during the deformation process (as-sintered composites), while when the TiB whiskers were oriented all whiskers could strengthen the matrix during the tensile testing process (as-extruded composites). Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Sealing Ability of Alkaline Endodontic Cements versus Resin Cements
Materials 2017, 10(11), 1228; doi:10.3390/ma10111228
Received: 13 September 2017 / Revised: 15 October 2017 / Accepted: 20 October 2017 / Published: 25 October 2017
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Abstract
Penetration of oral bacteria through root fillings leads to their long term failure. Dimensionally stable alkaline cements have been developed. A saliva challenge model was used to compare resistance to bacterial penetration of these alkaline cements to conventional root fillings that combine gutta
[...] Read more.
Penetration of oral bacteria through root fillings leads to their long term failure. Dimensionally stable alkaline cements have been developed. A saliva challenge model was used to compare resistance to bacterial penetration of these alkaline cements to conventional root fillings that combine gutta percha (GP) with epoxy resin sealers. A sample of 140 human roots with single straight canals prepared to standard length and canal size were obturated with mineral trioxide aggregate (MTA) (Nex MTA or MTAmix), with an alkaline calcium hydroxide hard setting cement (Supercal), or with GP and a resin cement (either AH-Plus or Zirmix). Negative control roots were sealed with wax, while positive controls were left open. The test assemblies were gamma sterilised, then the coronal root face was exposed daily to fresh stimulated human saliva diluted in broth. Bacterial penetration was determined by assessing growth in sterile brain-heart infusion (BHI) medium in contact with the root apex. Using Kaplan–Meier survival analysis, in order of performance from highest to lowest: Negative control, Supercal, Nex MTA, Zirmix, MTAmix, GP + AH-Plus, and the positive control. In addition, statistically significant differences were noted between Supercal and AH-Plus, and between the two MTA cements. It can be concluded that alkaline cements, particularly Supercal, can show considerable resistance to bacterial penetration from constant saliva challenge, and provide superior sealing ability in comparison to resin cements. While this property is due mostly to dimensional stability, the release of hydroxide ions could be a contributing factor to impaired bacterial survival, and this aspect should be explored further. Full article
(This article belongs to the Special Issue Dental Biomaterials 2017)
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Open AccessArticle A Rapid One-Step Process for Fabrication of Biomimetic Superhydrophobic Surfaces by Pulse Electrodeposition
Materials 2017, 10(11), 1229; doi:10.3390/ma10111229
Received: 6 September 2017 / Revised: 20 October 2017 / Accepted: 21 October 2017 / Published: 25 October 2017
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Abstract
Inspired by some typical plants such as lotus leaves, superhydrophobic surfaces are commonly prepared by a combination of low surface energy materials and hierarchical micro/nano structures. In this work, superhydrophobic surfaces on copper substrates were prepared by a rapid, facile one-step pulse electrodepositing
[...] Read more.
Inspired by some typical plants such as lotus leaves, superhydrophobic surfaces are commonly prepared by a combination of low surface energy materials and hierarchical micro/nano structures. In this work, superhydrophobic surfaces on copper substrates were prepared by a rapid, facile one-step pulse electrodepositing process, with different duty ratios in an electrolyte containing lanthanum chloride (LaCl3·6H2O), myristic acid (CH3(CH2)12COOH), and ethanol. The equivalent electrolytic time was only 10 min. The surface morphology, chemical composition and superhydrophobic property of the pulse electrodeposited surfaces were fully investigated with SEM, EDX, XRD, contact angle meter and time-lapse photographs of water droplets bouncing method. The results show that the as-prepared surfaces have micro/nano dual scale structures mainly consisting of La[CH3(CH2)12COO]3 crystals. The maximum water contact angle (WCA) is about 160.9°, and the corresponding sliding angle is about 5°. This method is time-saving and can be easily extended to other conductive materials, having a great potential for future applications. Full article
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Open AccessArticle Effect of Built-Up Edge Formation during Stable State of Wear in AISI 304 Stainless Steel on Machining Performance and Surface Integrity of the Machined Part
Materials 2017, 10(11), 1230; doi:10.3390/ma10111230
Received: 4 October 2017 / Revised: 21 October 2017 / Accepted: 23 October 2017 / Published: 25 October 2017
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Abstract
During machining of stainless steels at low cutting -speeds, workpiece material tends to adhere to the cutting tool at the tool–chip interface, forming built-up edge (BUE). BUE has a great importance in machining processes; it can significantly modify the phenomenon in the cutting
[...] Read more.
During machining of stainless steels at low cutting -speeds, workpiece material tends to adhere to the cutting tool at the tool–chip interface, forming built-up edge (BUE). BUE has a great importance in machining processes; it can significantly modify the phenomenon in the cutting zone, directly affecting the workpiece surface integrity, cutting tool forces, and chip formation. The American Iron and Steel Institute (AISI) 304 stainless steel has a high tendency to form an unstable BUE, leading to deterioration of the surface quality. Therefore, it is necessary to understand the nature of the surface integrity induced during machining operations. Although many reports have been published on the effect of tool wear during machining of AISI 304 stainless steel on surface integrity, studies on the influence of the BUE phenomenon in the stable state of wear have not been investigated so far. The main goal of the present work is to investigate the close link between the BUE formation, surface integrity and cutting forces in the stable sate of wear for uncoated cutting tool during the cutting tests of AISI 304 stainless steel. The cutting parameters were chosen to induce BUE formation during machining. X-ray diffraction (XRD) method was used for measuring superficial residual stresses of the machined surface through the stable state of wear in the cutting and feed directions. In addition, surface roughness of the machined surface was investigated using the Alicona microscope and Scanning Electron Microscopy (SEM) was used to reveal the surface distortions created during the cutting process, combined with chip undersurface analyses. The investigated BUE formation during the stable state of wear showed that the BUE can cause a significant improvement in the surface integrity and cutting forces. Moreover, it can be used to compensate for tool wear through changing the tool geometry, leading to the protection of the cutting tool from wear. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Recrystallization-Induced Surface Cracks of Carbon Ions Irradiated 6H-SiC after Annealing
Materials 2017, 10(11), 1231; doi:10.3390/ma10111231
Received: 2 October 2017 / Revised: 20 October 2017 / Accepted: 24 October 2017 / Published: 25 October 2017
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Abstract
Single crystal 6H-SiC wafers with 4° off-axis [0001] orientation were irradiated with carbon ions and then annealed at 900 °C for different time periods. The microstructure and surface morphology of these samples were investigated by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy
[...] Read more.
Single crystal 6H-SiC wafers with 4° off-axis [0001] orientation were irradiated with carbon ions and then annealed at 900 °C for different time periods. The microstructure and surface morphology of these samples were investigated by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Ion irradiation induced SiC amorphization, but the surface was smooth and did not have special structures. During the annealing process, the amorphous SiC was recrystallized to form columnar crystals that had a large amount of twin structures. The longer the annealing time was, the greater the amount of recrystallized SiC would be. The recrystallization volume fraction was accorded with the law of the Johnson–Mehl–Avrami equation. The surface morphology consisted of tiny pieces with an average width of approximately 30 nm in the annealed SiC. The volume shrinkage of irradiated SiC layer and the anisotropy of newly born crystals during annealing process produced internal stress and then induced not only a large number of dislocation walls in the non-irradiated layer but also the initiation and propagation of the cracks. The direction of dislocation walls was perpendicular to the growth direction of the columnar crystal. The longer the annealing time was, the larger the length and width of the formed crack would be. A quantitative model of the crack growth was provided to calculate the length and width of the cracks at a given annealing time. Full article
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Open AccessArticle Effect of Milling Time on the Microstructure, Physical and Mechanical Properties of Al-Al2O3 Nanocomposite Synthesized by Ball Milling and Powder Metallurgy
Materials 2017, 10(11), 1232; doi:10.3390/ma10111232
Received: 7 June 2017 / Revised: 22 July 2017 / Accepted: 1 August 2017 / Published: 26 October 2017
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Abstract
The effect of milling time on the morphology, microstructure, physical and mechanical properties of pure Al-5 wt % Al2O3 (Al-5Al2O3) has been investigated. Al-5Al2O3 nanocomposites were fabricated using ball milling in a powder
[...] Read more.
The effect of milling time on the morphology, microstructure, physical and mechanical properties of pure Al-5 wt % Al2O3 (Al-5Al2O3) has been investigated. Al-5Al2O3 nanocomposites were fabricated using ball milling in a powder metallurgy route. The increase in the milling time resulted in the homogenous dispersion of 5 wt % Al2O3 nanoparticles, the reduction of particle clustering, and the reduction of distances between the composite particles. The significant grain refining during milling was revealed which showed as a reduction of particle size resulting from longer milling time. X-Ray diffraction (XRD) analysis of the nanocomposite powders also showed that designated ball milling contributes to the crystalline refining and accumulation of internal stress due to induced severe plastic deformation of the particles. It can be argued that these morphological and microstructural variations of nanocomposite powders induced by designated ball milling time was found to contribute to an improvement in the density, densification, micro-hardness (HV), nano-hardness (HN), and Young’s modulus (E) of Al-5Al2O3 nanocomposites. HV, HN, and E values of nanocomposites were increased by ~48%, 46%, and 40%, after 12 h of milling, respectively. Full article
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Open AccessArticle Effects of Texture and Grain Size on the Yield Strength of ZK61 Alloy Rods Processed by Cyclic Extrusion and Compression
Materials 2017, 10(11), 1234; doi:10.3390/ma10111234
Received: 23 September 2017 / Revised: 11 October 2017 / Accepted: 23 October 2017 / Published: 26 October 2017
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Abstract
The ZK61 alloy rods with different grain sizes and crystallographic texture were successfully fabricated by cyclic extrusion and compression (CEC). Their room-temperature tension & compression yield strength displayed a significant dependence on grain size and texture, essentially attributed to {10-12} twinning. The texture
[...] Read more.
The ZK61 alloy rods with different grain sizes and crystallographic texture were successfully fabricated by cyclic extrusion and compression (CEC). Their room-temperature tension & compression yield strength displayed a significant dependence on grain size and texture, essentially attributed to {10-12} twinning. The texture variations were characterized by the angle θ between the c-axis of the grain and the extrusion direction (ED) during the process. The contour map of room-temperature yield strength as a function of grain size and the angle θ was obtained. It showed that both the tension yield strength and the compression yield strength of ZK61 alloy were fully consistent with the Hall-Patch relationship at a certain texture, but the change trends of the tension yield strength and the compression yield strength were completely opposite at the same grain size while texture altered. The friction stresses of different deformation modes calculated based on the texture confirmed the tension yield strength of the CECed ZK61 alloy rods, which was determined by both the basal slip and the tension twinning slip during the tension deformation at room temperature, while the compression yield strength was mainly determined by the basal slip during the compression deformation. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Thermoelectric Properties of Bi2Te3: CuI and the Effect of Its Doping with Pb Atoms
Materials 2017, 10(11), 1235; doi:10.3390/ma10111235
Received: 2 October 2017 / Revised: 18 October 2017 / Accepted: 20 October 2017 / Published: 26 October 2017
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Abstract
In order to understand the effect of Pb-CuI co-doping on the thermoelectric performance of Bi2Te3, n-type Bi2Te3 co-doped with x at % CuI and 1/2x at % Pb (x = 0, 0.01, 0.03,
[...] Read more.
In order to understand the effect of Pb-CuI co-doping on the thermoelectric performance of Bi2Te3, n-type Bi2Te3 co-doped with x at % CuI and 1/2x at % Pb (x = 0, 0.01, 0.03, 0.05, 0.07, and 0.10) were prepared via high temperature solid state reaction and consolidated using spark plasma sintering. Electron and thermal transport properties, i.e., electrical conductivity, carrier concentration, Hall mobility, Seebeck coefficient, and thermal conductivity, of CuI-Pb co-doped Bi2Te3 were measured in the temperature range from 300 K to 523 K, and compared to corresponding x% of CuI-doped Bi2Te3 and undoped Bi2Te3. The addition of a small amount of Pb significantly decreased the carrier concentration, which could be attributed to the holes from Pb atoms, thus the CuI-Pb co-doped samples show a lower electrical conductivity and a higher Seebeck coefficient when compared to CuI-doped samples with similar x values. The incorporation of Pb into CuI-doped Bi2Te3 rarely changed the power factor because of the trade-off relationship between the electrical conductivity and the Seebeck coefficient. The total thermal conductivity(κtot) of co-doped samples (κtot ~ 1.4 W/m∙K at 300 K) is slightly lower than that of 1% CuI-doped Bi2Te3tot ~ 1.5 W/m∙K at 300 K) and undoped Bi2Te3tot ~ 1.6 W/m∙K at 300 K) due to the alloy scattering. The 1% CuI-Pb co-doped Bi2Te3 sample shows the highest ZT value of 0.96 at 370 K. All data on electrical and thermal transport properties suggest that the thermoelectric properties of Bi2Te3 and its operating temperature can be controlled by co-doping. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Simulation and Experimental Studies on Grain Selection and Structure Design of the Spiral Selector for Casting Single Crystal Ni-Based Superalloy
Materials 2017, 10(11), 1236; doi:10.3390/ma10111236
Received: 8 September 2017 / Revised: 21 October 2017 / Accepted: 22 October 2017 / Published: 27 October 2017
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Abstract
Grain selection is an important process in single crystal turbine blades manufacturing. Selector structure is a control factor of grain selection, as well as directional solidification (DS). In this study, the grain selection and structure design of the spiral selector were investigated through
[...] Read more.
Grain selection is an important process in single crystal turbine blades manufacturing. Selector structure is a control factor of grain selection, as well as directional solidification (DS). In this study, the grain selection and structure design of the spiral selector were investigated through experimentation and simulation. A heat transfer model and a 3D microstructure growth model were established based on the Cellular automaton-Finite difference (CA-FD) method for the grain selector. Consequently, the temperature field, the microstructure and the grain orientation distribution were simulated and further verified. The average error of the temperature result was less than 1.5%. The grain selection mechanisms were further analyzed and validated through simulations. The structural design specifications of the selector were suggested based on the two grain selection effects. The structural parameters of the spiral selector, namely, the spiral tunnel diameter (dw), the spiral pitch (hb) and the spiral diameter (hs), were studied and the design criteria of these parameters were proposed. The experimental and simulation results demonstrated that the improved selector could accurately and efficiently produce a single crystal structure. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessFeature PaperArticle Pore Size Distribution in Granular Material Microstructure
Materials 2017, 10(11), 1237; doi:10.3390/ma10111237
Received: 1 August 2017 / Revised: 10 October 2017 / Accepted: 20 October 2017 / Published: 27 October 2017
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Abstract
Pore scale modeling plays a key role in fluid flow through porous media and associated macroscale constitutive relationships. The polyhedral shape and effective local pore size within granular material microstructure are computed in this study by means of the Euclidean Distance Transform (EDT),
[...] Read more.
Pore scale modeling plays a key role in fluid flow through porous media and associated macroscale constitutive relationships. The polyhedral shape and effective local pore size within granular material microstructure are computed in this study by means of the Euclidean Distance Transform (EDT), a local maxima search (non-maximum suppression), and a segmentation process. Various synthetic packed particles are simulated and employed as comparative models during the computation of pore size distribution (PSD). Reconstructed un-sheared and sheared Ottawa 20–30 sand samples are used to compute PSD for non-trivial and non-spherical models. Full article
(This article belongs to the Special Issue Granular Materials)
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Open AccessArticle Multifunctional PMMA@Fe3O4@DR Magnetic Materials for Efficient Adsorption of Dyes
Materials 2017, 10(11), 1239; doi:10.3390/ma10111239
Received: 21 September 2017 / Revised: 23 October 2017 / Accepted: 24 October 2017 / Published: 27 October 2017
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Abstract
Magnetic porous microspheres are widely used in modern wastewater treatment technology due to their simple and quick dye adsorption and separation functions. In this article, we prepared porous polymethylmethacrylate (PMMA) microspheres by the seed-swelling method, followed by in situ formation of iron oxide
[...] Read more.
Magnetic porous microspheres are widely used in modern wastewater treatment technology due to their simple and quick dye adsorption and separation functions. In this article, we prepared porous polymethylmethacrylate (PMMA) microspheres by the seed-swelling method, followed by in situ formation of iron oxide (Fe3O4) nanoparticles within the pore. Then, we used diazo-resin (DR) to encapsulate the porous magnetic microspheres and achieve PMMA@Fe3O4@DR magnetic material. We studied the different properties of magnetic microspheres by different dye adsorption experiments before and after the encapsulation and demonstrated that the PMMA@Fe3O4@DR microspheres can be successfully used as a reusable absorbent for fast and easy removal of anionic and aromatic dyes from wastewater and can maintain excellent magnetic and adsorption properties in harsh environments. Full article
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Open AccessArticle Analysis of the Microstructure and Mechanical Properties of Titanium-Based Composites Reinforced by Secondary Phases and B4C Particles Produced via Direct Hot Pressing
Materials 2017, 10(11), 1240; doi:10.3390/ma10111240
Received: 23 October 2017 / Revised: 23 October 2017 / Accepted: 25 October 2017 / Published: 27 October 2017
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Abstract
In the last decade, titanium metal matrix composites (TMCs) have received considerable attention thanks to their interesting properties as a consequence of the clear interface between the matrix and the reinforcing phases formed. In this work, TMCs with 30 vol % of B
[...] Read more.
In the last decade, titanium metal matrix composites (TMCs) have received considerable attention thanks to their interesting properties as a consequence of the clear interface between the matrix and the reinforcing phases formed. In this work, TMCs with 30 vol % of B4C are consolidated by hot pressing. This technique is a powder metallurgy rapid process. Incorporation of the intermetallic to the matrix, 20 vol % (Ti-Al), is also evaluated. Here, the reinforcing phases formed by the reaction between the titanium matrix and the ceramic particles, as well as the intermetallic addition, promote substantial variations to the microstructure and to the properties of the fabricated composites. The influences of the starting materials and the consolidation temperature (900 °C and 1000 °C) are investigated. By X-ray diffraction, scanning and transmission electron microscopy analysis, the in-situ-formed phases in the matrix and the residual ceramic particles were studied. Furthermore, mechanical properties are studied through tensile and bending tests in addition to other properties, such as Young’s modulus, hardness, and densification of the composites. The results show the significant effect of temperature on the microstructure and on the mechanical properties from the same starting powder. Moreover, the Ti-Al addition causes variation in the interface between the reinforcement and the matrix, thereby affecting the behaviour of the TMCs produced at the same temperature. Full article
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Open AccessArticle Ultra-Thin Multi-Band Polarization-Insensitive Microwave Metamaterial Absorber Based on Multiple-Order Responses Using a Single Resonator Structure
Materials 2017, 10(11), 1241; doi:10.3390/ma10111241
Received: 18 September 2017 / Revised: 19 October 2017 / Accepted: 26 October 2017 / Published: 27 October 2017
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Abstract
We design an ultra-thin multi-band polarization-insensitive metamaterial absorber (MMA) using a single circular sector resonator (CSR) structure in the microwave region. Simulated results show that the proposed MMA has three distinctive absorption peaks at 3.35 GHz, 8.65 GHz, and 12.44 GHz, with absorbance
[...] Read more.
We design an ultra-thin multi-band polarization-insensitive metamaterial absorber (MMA) using a single circular sector resonator (CSR) structure in the microwave region. Simulated results show that the proposed MMA has three distinctive absorption peaks at 3.35 GHz, 8.65 GHz, and 12.44 GHz, with absorbance of 98.8%, 99.7%, and 98.3%, respectively, which agree well with an experiment. Simulated surface current distributions of the unit-cell structure reveal that the triple-band absorption mainly originates from multiple-harmonic magnetic resonance. The proposed triple-band MMA can remain at a high absorption level for all polarization of both transverse-electric (TE) and transverse-magnetic (TM) modes under normal incidence. Moreover, by further optimizing the geometric parameters of the CSRs, four-band and five-band MMAs can also be obtained. Thus, our design will have potential application in detection, sensing, and stealth technology. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Synthesis of Quantum Dot-ZnS Nanosheet Inorganic Assembly with Low Thermal Fluorescent Quenching for LED Application
Materials 2017, 10(11), 1242; doi:10.3390/ma10111242
Received: 30 September 2017 / Revised: 17 October 2017 / Accepted: 23 October 2017 / Published: 27 October 2017
PDF Full-text (4605 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this report, to tackle the thermal fluorescent quenching issue of II-VI semiconductor quantum dots (QDs), which hinders their on-chip packaging application to light-emitting diodes (LEDs), a QD-ZnS nanosheet inorganic assembly monolith (QD-ZnS NIAM) is developed through chemisorption of QDs on the surface
[...] Read more.
In this report, to tackle the thermal fluorescent quenching issue of II-VI semiconductor quantum dots (QDs), which hinders their on-chip packaging application to light-emitting diodes (LEDs), a QD-ZnS nanosheet inorganic assembly monolith (QD-ZnS NIAM) is developed through chemisorption of QDs on the surface of two-dimensional (2D) ZnS nanosheets and subsequent assembly of the nanosheets into a compact inorganic monolith. The QD-ZnS NIAM could reduce the thermal fluorescent quenching of QDs effectively, possibly due to fewer thermally induced permanent trap states and decreased Förster resonance energy transfer (FRET) among QDs when compared with those in a reference QD composite thin film. We have demonstrated that the QD-ZnS NIAM enables QDs to be directly packaged on-chip in LEDs with over 90% of their initial luminance being retained at above 85 °C, showing advantage in LED application in comparison with conventional QD composite film. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessCommunication Design of Viologen-Based Liquid Crystals Exhibiting Bicontinuous Cubic Phases and Their Redox-Active Behavior
Materials 2017, 10(11), 1243; doi:10.3390/ma10111243
Received: 14 October 2017 / Revised: 25 October 2017 / Accepted: 26 October 2017 / Published: 27 October 2017
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Abstract
We have succeeded in developing viologen-based liquid-crystalline materials forming bicontinuous cubic phases. They are composed of amphiphilic zwitterions with a viologen ionic-head-group and sulfonyl-imide-type acids. In the bicontinuous cubic liquid-crystalline assemblies, the ionic-head groups of the amphiphiles align along a gyroid minimal surface,
[...] Read more.
We have succeeded in developing viologen-based liquid-crystalline materials forming bicontinuous cubic phases. They are composed of amphiphilic zwitterions with a viologen ionic-head-group and sulfonyl-imide-type acids. In the bicontinuous cubic liquid-crystalline assemblies, the ionic-head groups of the amphiphiles align along a gyroid minimal surface, forming a 3D continuous viologen layer. The ionic state of the viologen-moieties can be tuned from a dication state (V2+) to a radical mono cation state (V1+•) by UV irradiation and/or electric field. This redox reaction proceeds in bulk, accompanying the change of their color from colorless to purple. Interestingly, they preserve the 3D molecular assembled structures beyond the redox reaction, which has been confirmed by polarizing optical microscopy and X-ray diffraction measurements. Full article
(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)
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Open AccessFeature PaperArticle Mesoporous Bioactive Glass Functionalized 3D Ti-6Al-4V Scaffolds with Improved Surface Bioactivity
Materials 2017, 10(11), 1244; doi:10.3390/ma10111244
Received: 6 September 2017 / Revised: 30 September 2017 / Accepted: 26 October 2017 / Published: 27 October 2017
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Abstract
Porous Ti-6Al-4V scaffolds fabricated by means of selective laser melting (SLM), having controllable geometrical features and preferable mechanical properties, have been developed as a class of biomaterials that hold promising potential for bone repair. However, the inherent bio-inertness of the Ti-6Al-4V alloy as
[...] Read more.
Porous Ti-6Al-4V scaffolds fabricated by means of selective laser melting (SLM), having controllable geometrical features and preferable mechanical properties, have been developed as a class of biomaterials that hold promising potential for bone repair. However, the inherent bio-inertness of the Ti-6Al-4V alloy as the matrix of the scaffolds results in a lack in the ability to stimulate bone ingrowth and regeneration. The aim of the present study was to develop a bioactive coating on the struts of SLM Ti-6Al-4V scaffolds in order to add the desired surface osteogenesis ability. Mesoporous bioactive glasses (MBGs) coating was applied on the strut surfaces of the SLM Ti-6Al-4V scaffolds through spin coating, followed by a heat treatment. It was found that the coating could maintain the characteristic mesoporous structure and chemical composition of MBG, and establish good interfacial adhesion to the Ti-6Al-4V substrate. The compressive strength and pore interconnectivity of the scaffolds were not affected by the coating. Moreover, the results obtained from in vitro cell culture experiments demonstrated that the attachment, proliferation, and differentiation of human bone marrow stromal cells (hBMSCs) on the MBG-coated Ti-6Al-4V scaffolds were improved as compared with those on the conventional bioactive glass (BG)-coated Ti-6Al-4V scaffolds and bare-metal Ti-6Al-4V scaffolds. Our results demonstrated that the MBG coating by using the spinning coating method could be an effective approach to achieving enhanced surface biofunctionalization for SLM Ti-6Al-4V scaffolds. Full article
(This article belongs to the Special Issue Bioactive Glasses 2017)
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Open AccessArticle Effects of Fluoride on Two Chemical Models of Enamel Demineralization
Materials 2017, 10(11), 1245; doi:10.3390/ma10111245
Received: 12 September 2017 / Revised: 23 October 2017 / Accepted: 26 October 2017 / Published: 27 October 2017
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Abstract
This study evaluated the effects of fluoride on subsurface enamel demineralization induced by two commonly used chemical models. Forty-eight enamel blocks were demineralized at pH = 5.0 by an acetate buffer (Group 1), a lactate buffer (Group 2), an acetate buffer with 0.02
[...] Read more.
This study evaluated the effects of fluoride on subsurface enamel demineralization induced by two commonly used chemical models. Forty-eight enamel blocks were demineralized at pH = 5.0 by an acetate buffer (Group 1), a lactate buffer (Group 2), an acetate buffer with 0.02 ppm fluoride (Group 3) and a lactate buffer with 0.02 ppm fluoride (Group 4) at 25 °C for 3 weeks. The surface destruction percentage (SDP), mineral loss and lesion depth of the blocks were studied using micro-computed tomography. An elemental analysis of the enamel surface was evaluated using an energy-dispersive X-ray spectroscopy. Surface micro-hardness was determined by the Knoop Hardness Test. The mean lesion depth of Groups 1 through 4 were 134.1 ± 27.2 μm, 96.1 ± 16.5 μm, 97.5 ± 22.4 μm and 91.1 ± 16.2 μm, respectively (p < 0.001; group 1 > 2, 3 > 4). The SDPs of groups 1 through 4 were 7.8 ± 8.93%, 0.71 ± 1.6%, 0.36 ± 1.70% and 1.36 ± 2.94% (p < 0.001; group 1 > 2, 3, 4). The fluoride in mean weight percentages of groups 1 through 4 were 1.12 ± 0.24%, 1.10 ± 0.20%, 1.45 ± 0.40% and 1.51 ± 0.51%, respectively (p < 0.001; group 3, 4 > 1, 2). The mean Knoop hardness values of groups 1 through 4 were 27.5 ± 13.3, 39.7 ± 19.3, 73.6 ± 44.2 and 91.0 ± 57.2, respectively (p < 0.001; group 4 > 3 > 2 > 1). The chemical model using an acetate buffer solution created significantly deeper zones of subsurface demineralization on enamel than the lactate buffer solution. An acetate buffer may damage the enamel surface, but the surface damage can be prevented by adding fluoride. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Thermal Degradation Kinetics of Sugarcane Bagasse and Soft Wood Cellulose
Materials 2017, 10(11), 1246; doi:10.3390/ma10111246
Received: 12 June 2017 / Revised: 24 August 2017 / Accepted: 25 August 2017 / Published: 28 October 2017
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Abstract
The properties of untreated sugar cane bagasse (SCB) and soft wood (SW) and their respective celluloses were investigated. The celluloses indicated improved crystallinity index values and decreased concentration of lignin and hemicellulose compared to their untreated counterparts. Three degradation models, Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa
[...] Read more.
The properties of untreated sugar cane bagasse (SCB) and soft wood (SW) and their respective celluloses were investigated. The celluloses indicated improved crystallinity index values and decreased concentration of lignin and hemicellulose compared to their untreated counterparts. Three degradation models, Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (OFW), and Kissinger (KGR) methods were employed to determine apparent activation energy values. Generally, the thermal degradation processes of both sugarcane bagasse and soft wood included dehydration, degradation of hemicellulose and cellulose, whereas the lignin degraded from the degradation temperature of hemicellulose to the end of the cellulose. The apparent activation energy values obtained from the OFW and KAS models vary with the degree of conversion, and showed similar trends. The activation energies obtained by KGR were relatively lower than those obtained from the KAS and OFW methods. Full article
(This article belongs to the Special Issue Energetic Materials and Processes)
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Open AccessArticle Waterborne Polyurethane Coatings with Covalently Linked Black Dye Sudan Black B
Materials 2017, 10(11), 1247; doi:10.3390/ma10111247
Received: 17 September 2017 / Revised: 26 October 2017 / Accepted: 26 October 2017 / Published: 28 October 2017
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Abstract
Colored waterborne polyurethanes have been widely used in paintings, leathers, textiles, and coatings. Here, a series of black waterborne polyurethanes (WPUs) with different ratios of black dye, Sudan Black B (SDB), were prepared by step-growth polymerization. WPU emulsions as obtained exhibit low particle
[...] Read more.
Colored waterborne polyurethanes have been widely used in paintings, leathers, textiles, and coatings. Here, a series of black waterborne polyurethanes (WPUs) with different ratios of black dye, Sudan Black B (SDB), were prepared by step-growth polymerization. WPU emulsions as obtained exhibit low particle sizes and remarkable storage stability at the same time. At different dye loadings, essential structural, statistical and thermal properties are characterized. FTIR (fourier transform infrared) spectra indicate that SDB is covalently linked into waterborne polyurethane chains. All of the WPUs with covalently linked SDB show better color fastness and resistance of thermal migration than those with SDB mixed physically. Besides, WPUs incorporated SDB covalently with different polymeric diols, polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), poly-1, 4-butylene adipate glycol (PBA) and polycaprolactone glycol (PCL), were prepared to obtain different properties to cater to a variety of practical demands. By a spraying method, the black WPUs can be directly used as metal coatings without complex dyeing process by simply mixing coating additive and other waterborne resins, which exhibit excellent coating performance. Full article
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Open AccessArticle Microstructure, Wear Resistance and Oxidation Behavior of Ni-Ti-Si Coatings Fabricated on Ti6Al4V by Laser Cladding
Materials 2017, 10(11), 1248; doi:10.3390/ma10111248
Received: 8 September 2017 / Revised: 10 October 2017 / Accepted: 20 October 2017 / Published: 30 October 2017
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Abstract
The Ni-Ti-Si composite coatings were successfully fabricated on Ti6Al4V by laser cladding. The microstructure were studied by SEM (scanning electron microscopy) and EDS (energy dispersive spectrometer). It has been found that Ti2Ni and Ti5Si3 phases exist in all
[...] Read more.
The Ni-Ti-Si composite coatings were successfully fabricated on Ti6Al4V by laser cladding. The microstructure were studied by SEM (scanning electron microscopy) and EDS (energy dispersive spectrometer). It has been found that Ti2Ni and Ti5Si3 phases exist in all coatings, and some samples have TiSi2 phases. Moreover, due to the existence of these phases, coatings presented relatively higher microhardness than that of the substrate (826 HV (Vickers hardness)) and the microhardness value of coating 3 is about twice larger than that of the substrate. During the dry sliding friction and wear test, due to the distribution of the relatively ductile phase of Ti2Ni and reinforcement phases of Ti5Si3 and TiSi2, the coatings performed good wear resistance. The oxidation process contains two stages: the rapid oxidation and slow oxidation by high temperature oxidation test at 800 °C for 50 h. Meanwhile, the value of the oxidation weight gain of the substrate is approximately three times larger than that of the coating 4. During the oxidation process, the oxidation film formed on the coating is mainly consisted of TiO2, Al2O3 and SiO2. Phases Ti2Ni, Ti5Si3, TiSi2 and TiSi were still found and it could be responsible for the improvement in oxidation resistance of the coatings by laser cladding. Full article
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Open AccessArticle Simultaneous Contact Sensing and Characterizing of Mechanical and Dynamic Heat Transfer Properties of Porous Polymeric Materials
Materials 2017, 10(11), 1249; doi:10.3390/ma10111249
Received: 2 October 2017 / Revised: 16 October 2017 / Accepted: 28 October 2017 / Published: 30 October 2017
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Abstract
Porous polymeric materials, such as textile fabrics, are elastic and widely used in our daily life for garment and household products. The mechanical and dynamic heat transfer properties of porous polymeric materials, which describe the sensations during the contact process between porous polymeric
[...] Read more.
Porous polymeric materials, such as textile fabrics, are elastic and widely used in our daily life for garment and household products. The mechanical and dynamic heat transfer properties of porous polymeric materials, which describe the sensations during the contact process between porous polymeric materials and parts of the human body, such as the hand, primarily influence comfort sensations and aesthetic qualities of clothing. A multi-sensory measurement system and a new method were proposed to simultaneously sense the contact and characterize the mechanical and dynamic heat transfer properties of porous polymeric materials, such as textile fabrics in one instrument, with consideration of the interactions between different aspects of contact feels. The multi-sensory measurement system was developed for simulating the dynamic contact and psychological judgment processes during human hand contact with porous polymeric materials, and measuring the surface smoothness, compression resilience, bending and twisting, and dynamic heat transfer signals simultaneously. The contact sensing principle and the evaluation methods were presented. Twelve typical sample materials with different structural parameters were measured. The results of the experiments and the interpretation of the test results were described. An analysis of the variance and a capacity study were investigated to determine the significance of differences among the test materials and to assess the gage repeatability and reproducibility. A correlation analysis was conducted by comparing the test results of this measurement system with the results of Kawabata Evaluation System (KES) in separate instruments. This multi-sensory measurement system provides a new method for simultaneous contact sensing and characterizing of mechanical and dynamic heat transfer properties of porous polymeric materials. Full article
(This article belongs to the Special Issue Contact Mechanics and Elastomer Friction of Materials)
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Open AccessArticle Simulation of Intergranular Ductile Cracking in β Titanium Alloys Based on a Micro-Mechanical Damage Model
Materials 2017, 10(11), 1250; doi:10.3390/ma10111250
Received: 25 September 2017 / Revised: 20 October 2017 / Accepted: 23 October 2017 / Published: 30 October 2017
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Abstract
The intergranular crack propagation of the lamellar structure β titanium alloys is investigated by using a modified Gurson-type damage model. The representative microstructure of the lamellar alloy, which consists of the soft α phase layer surrounding the hard grain interiors, is generated based
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The intergranular crack propagation of the lamellar structure β titanium alloys is investigated by using a modified Gurson-type damage model. The representative microstructure of the lamellar alloy, which consists of the soft α phase layer surrounding the hard grain interiors, is generated based on an advanced Voronoi algorithm. Both the normal fracture due to void growth and the shear fracture associated with void shearing are considered for the grain boundary α layer. The individual phase properties are determined according to the experimental nanoindentation result and the macroscopic stress–strain curve from a uni-axial tensile test. The effects of the strain hardening exponent of the grain interiors and the void shearing mechanism of the grain boundary α layer on fracture toughness and the intergranular crack growth behavior are emphatically studied. The computational predictions indicate that fracture toughness can be increased with increasing the strain hardening ability of the grain interiors and void shearing can be deleterious to fracture toughness. Based on the current simulation technique, qualitative understanding of relationships between the individual phase features and the fracture toughness of the lamellar alloys can be obtained, which provides useful suggestions to the heat treatment process of the β titanium alloys. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle A Highly Flexible Supercapacitor Based on MnO2/RGO Nanosheets and Bacterial Cellulose-Filled Gel Electrolyte
Materials 2017, 10(11), 1251; doi:10.3390/ma10111251
Received: 4 October 2017 / Revised: 20 October 2017 / Accepted: 28 October 2017 / Published: 30 October 2017
PDF Full-text (5222 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The flexible supercapacitors (SCs) of the conventional sandwich-type structure have poor flexibility due to the large thickness of the final entire device. Herein, we have fabricated a highly flexible asymmetric SC using manganese dioxide (MnO2) and reduced graphene oxide (RGO) nanosheet-piled
[...] Read more.
The flexible supercapacitors (SCs) of the conventional sandwich-type structure have poor flexibility due to the large thickness of the final entire device. Herein, we have fabricated a highly flexible asymmetric SC using manganese dioxide (MnO2) and reduced graphene oxide (RGO) nanosheet-piled hydrogel films and a novel bacterial cellulose (BC)-filled polyacrylic acid sodium salt-Na2SO4 (BC/PAAS-Na2SO4) neutral gel electrolyte. Apart from being environmentally friendly, this BC/PAAS-Na2SO4 gel electrolyte has high viscosity and a sticky property, which enables it to combine two electrodes together. Meanwhile, the intertangling of the filled BC in the gel electrolyte hinders the decrease of the viscosity with temperature, and forms a separator to prevent the two electrodes from short-circuiting. Using these materials, the total thickness of the fabricated device does not exceed 120 μm. This SC device demonstrates high flexibility, where bending and even rolling have no obvious effect on the electrochemical performance. In addition, owing to the asymmetric configuration, the cell voltage of this flexible SC has been extended to 1.8 V, and the energy density can reach up to 11.7 Wh kg−1 at the power density of 441 W kg−1. This SC also exhibits a good cycling stability, with a capacitance retention of 85.5% over 5000 cycles. Full article
(This article belongs to the Section Energy Materials)
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Open AccessFeature PaperArticle Effect of Fungal Deterioration on Physical and Mechanical Properties of Hemp and Flax Natural Fiber Composites
Materials 2017, 10(11), 1252; doi:10.3390/ma10111252
Received: 7 October 2017 / Revised: 26 October 2017 / Accepted: 26 October 2017 / Published: 31 October 2017
PDF Full-text (6865 KB) | HTML Full-text | XML Full-text
Abstract
The development and application of bio-sourced composites have been gaining wide attention, yet their deterioration due to the growth of ubiquitous microorganisms during storage/manufacturing/in-service phases is still not fully understood for optimum material selection and design purposes. In this study, samples of non-woven
[...] Read more.
The development and application of bio-sourced composites have been gaining wide attention, yet their deterioration due to the growth of ubiquitous microorganisms during storage/manufacturing/in-service phases is still not fully understood for optimum material selection and design purposes. In this study, samples of non-woven flax fibers, hemp fibers, and mats made of co-mingled randomly-oriented flax or hemp fiber (50%) and polypropylene fiber (50%) were subjected to 28 days of exposure to (i) no water-no fungi, (ii) water only and (iii) water along with the Chaetomium globosum fungus. Biocomposite samples were measured for weight loss over time, to observe the rate of fungal growth and the respiration of cellulose components in the fibers. Tensile testing was conducted to measure mechanical properties of the composite samples under different configurations. Scanning electron microscopy was employed to visualize fungal hyphal growth on the natural fibers, as well as to observe the fracture planes and failure modes of the biocomposite samples. Results showed that fungal growth significantly affects the dry mass as well as the tensile elastic modulus of the tested natural fiber mats and composites, and the effect depends on both the type and the length scale of fibers, as well as the exposure condition and time. Full article
(This article belongs to the Special Issue Modeling and Simulation of Advanced Composite Materials)
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Open AccessArticle Remineralization Property of an Orthodontic Primer Containing a Bioactive Glass with Silver and Zinc
Materials 2017, 10(11), 1253; doi:10.3390/ma10111253
Received: 6 September 2017 / Revised: 15 October 2017 / Accepted: 28 October 2017 / Published: 31 October 2017
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Abstract
White spot lesions (WSLs) are irreversible damages in orthodontic treatment due to excessive etching or demineralization by microorganisms. In this study, we conducted a mechanical and cell viability test to examine the antibacterial properties of 0.2% and 1% bioactive glass (BAG) and silver-doped
[...] Read more.
White spot lesions (WSLs) are irreversible damages in orthodontic treatment due to excessive etching or demineralization by microorganisms. In this study, we conducted a mechanical and cell viability test to examine the antibacterial properties of 0.2% and 1% bioactive glass (BAG) and silver-doped and zinc-doped BAGs in a primer and evaluated their clinical applicability to prevent WSLs. The microhardness statistically significantly increased in the adhesive-containing BAG, while the other samples showed no statistically significant difference compared with the control group. The shear bond strength of all samples increased compared with that of the control group. The cell viability of the control and sample groups was similar within 24 h, but decreased slightly over 48 h. All samples showed antibacterial properties. Regarding remineralization property, the group containing 0.2% of the samples showed remineralization properties compared with the control group, but was not statistically significant; further, the group containing 1% of the samples showed a significant difference compared with the control group. Among them, the orthodontic bonding primer containing 1% silver-doped BAG showed the highest remineralization property. The new orthodontic bonding primer used in this study showed an antimicrobial effect, chemical remineralization effect, and WSL prevention as well as clinically applicable properties, both physically and biologically. Full article
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Open AccessArticle Performance of Sustainable Fly Ash and Slag Cement Mortars Exposed to Simulated and Real In Situ Mediterranean Conditions along 90 Warm Season Days
Materials 2017, 10(11), 1254; doi:10.3390/ma10111254
Received: 19 September 2017 / Revised: 6 October 2017 / Accepted: 28 October 2017 / Published: 31 October 2017
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Abstract
Nowadays, cement manufacture is one of the most polluting worldwide industrial sectors. In order to reduce its CO2 emissions, the clinker replacement by ground granulated blast–furnace slag and fly ash is becoming increasingly common. Both additions are well-studied when the hardening conditions
[...] Read more.
Nowadays, cement manufacture is one of the most polluting worldwide industrial sectors. In order to reduce its CO2 emissions, the clinker replacement by ground granulated blast–furnace slag and fly ash is becoming increasingly common. Both additions are well-studied when the hardening conditions of cementitious materials are optimum. Therefore, the main objective of this research was to study the short-term effects of exposure, to both laboratory simulated and real in situ Mediterranean climate environments, on the microstructure and durability-related properties of mortars made using commercial slag and fly ash cements, as well as ordinary Portland cement. The real in situ condition consisted of placing the samples at approximately 100 m away from the Mediterranean Sea. The microstructure was analysed using mercury intrusion porosimetry. The effective porosity, the capillary suction coefficient and the non-steady state chloride migration coefficient were also studied. In view of the results obtained, the non-optimum laboratory simulated Mediterranean environment was a good approach to the real in situ one. Finally, mortars prepared using sustainable cements with slag and fly ash exposed to both Mediterranean climate environments, showed adequate service properties in the short-term (90 days), similar to or even better than those in mortars made with ordinary Portland cement. Full article
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Open AccessArticle Evaluation of Microstructure and Mechanical Properties of Al-TiC Metal Matrix Composite Prepared by Conventional, Microwave and Spark Plasma Sintering Methods
Materials 2017, 10(11), 1255; doi:10.3390/ma10111255
Received: 6 October 2017 / Revised: 24 October 2017 / Accepted: 25 October 2017 / Published: 31 October 2017
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Abstract
In this research, the mechanical properties and microstructure of Al-15 wt % TiC composite samples prepared by spark plasma, microwave, and conventional sintering were investigated. The sintering process was performed by the speak plasma sintering (SPS) technique, microwave and conventional furnaces at 400
[...] Read more.
In this research, the mechanical properties and microstructure of Al-15 wt % TiC composite samples prepared by spark plasma, microwave, and conventional sintering were investigated. The sintering process was performed by the speak plasma sintering (SPS) technique, microwave and conventional furnaces at 400 °C, 600 °C, and 700 °C, respectively. The results showed that sintered samples by SPS have the highest relative density (99% of theoretical density), bending strength (291 ± 12 MPa), and hardness (253 ± 23 HV). The X-ray diffraction (XRD) investigations showed the formation of TiO2 from the surface layer decomposition of TiC particles. Scanning electron microscopy (SEM) micrographs demonstrated uniform distribution of reinforcement particles in all sintered samples. The SEM/EDS analysis revealed the formation of TiO2 around the porous TiC particles. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Calcium Phosphate Cement with Antimicrobial Properties and Radiopacity as an Endodontic Material
Materials 2017, 10(11), 1256; doi:10.3390/ma10111256
Received: 8 September 2017 / Revised: 13 October 2017 / Accepted: 27 October 2017 / Published: 31 October 2017
PDF Full-text (3493 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Calcium phosphate cements (CPCs) have several advantages for use as endodontic materials, and such advantages include ease of use, biocompatibility, potential hydroxyapatite-forming ability, and bond creation between the dentin and appropriate filling materials. However, unlike tricalcium silicate (CS)-based materials, CPCs do not have
[...] Read more.
Calcium phosphate cements (CPCs) have several advantages for use as endodontic materials, and such advantages include ease of use, biocompatibility, potential hydroxyapatite-forming ability, and bond creation between the dentin and appropriate filling materials. However, unlike tricalcium silicate (CS)-based materials, CPCs do not have antibacterial properties. The present study doped a nonwashable CPC with 0.25–1.0 wt % hinokitiol and added 0, 5, and 10 wt % CS. The CPCs with 0.25–0.5 wt % hinokitiol showed appreciable antimicrobial properties without alterations in their working or setting times, mechanical properties, or cytocompatibility. Addition of CS slightly retarded the apatite formation of CPC and the working and setting time was obviously reduced. Moreover, addition of CS dramatically increased the compressive strength of CPC. Doping CS with 5 wt % ZnO provided additional antibacterial effects to the present CPC system. CS and hinokitiol exerted a synergic antibacterial effect, and the CPC with 0.25 wt % hinokitiol and 10 wt % CS (doped with 5 wt % ZnO) had higher antibacterial properties than that of pure CS. The addition of 10 wt % bismuth subgallate doubled the CPC radiopacity. The results demonstrate that hinokitiol and CS can improve the antibacterial properties of CPCs, and they can thus be considered for endodontic applications. Full article
(This article belongs to the Special Issue Dental Biomaterials 2017)
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Open AccessArticle Electrochemical Synthesis of Core–Shell-Structured NbC–Fe Composite Powder for Enforcement in Low-Carbon Steel
Materials 2017, 10(11), 1257; doi:10.3390/ma10111257
Received: 22 September 2017 / Revised: 27 October 2017 / Accepted: 30 October 2017 / Published: 1 November 2017
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Abstract
An NbC–Fe composite powder was synthesized from an Nb2O5/Fe/C mixture by electrochemical reduction and subsequent carbonization in molten CaCl2–NaCl. The composite has a core–shell structure, in which NbC acts as the cores distributing in the Fe matrix.
[...] Read more.
An NbC–Fe composite powder was synthesized from an Nb2O5/Fe/C mixture by electrochemical reduction and subsequent carbonization in molten CaCl2–NaCl. The composite has a core–shell structure, in which NbC acts as the cores distributing in the Fe matrix. A strong bonding between NbC and Fe is benefit from the core–shell structure. The sintering and electrochemical reduction processes were investigated to probe the mechanism for the reactions. The results show that NbC particles about several nanometers were embraced by the Fe shell to form a composite about 100 nm in size. This featured structure can feasibly improve the wettability and sinterability of NbC as well as the uniform distribution of the carbide in the cast steel. By adding the composite into steel in the casting process, the grain size of the casted steel was markedly deceased from 1 mm to 500 μm on average, favoring the hardening of the casted steel. Full article
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Open AccessArticle Influence of Oxygen Pressure on the Domain Dynamics and Local Electrical Properties of BiFe0.95Mn0.05O3 Thin Films Studied by Piezoresponse Force Microscopy and Conductive Atomic Force Microscopy
Materials 2017, 10(11), 1258; doi:10.3390/ma10111258
Received: 30 July 2017 / Revised: 24 October 2017 / Accepted: 28 October 2017 / Published: 1 November 2017
PDF Full-text (3431 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work, we have studied the microstructures, nanodomains, polarization preservation behaviors, and electrical properties of BiFe0.95Mn0.05O3 (BFMO) multiferroic thin films, which have been epitaxially created on the substrates of SrRuO3, SrTiO3, and TiN-buffered
[...] Read more.
In this work, we have studied the microstructures, nanodomains, polarization preservation behaviors, and electrical properties of BiFe0.95Mn0.05O3 (BFMO) multiferroic thin films, which have been epitaxially created on the substrates of SrRuO3, SrTiO3, and TiN-buffered (001)-oriented Si at different oxygen pressures via piezoresponse force microscopy and conductive atomic force microscopy. We found that the pure phase state, inhomogeneous piezoresponse force microscopy (PFM) response, low leakage current with unidirectional diode-like properties, and orientation-dependent polarization reversal properties were found in BFMO thin films deposited at low oxygen pressure. Meanwhile, these films under high oxygen pressures resulted in impurities in the secondary phase in BFMO films, which caused a greater leakage that hindered the polarization preservation capability. Thus, this shows the important impact of the oxygen pressure on modulating the physical effects of BFMO films. Full article
(This article belongs to the Special Issue Scanning Probe Microscopy of Ferroics)
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Open AccessArticle Development of a Model for Dynamic Recrystallization Consistent with the Second Derivative Criterion
Materials 2017, 10(11), 1259; doi:10.3390/ma10111259
Received: 4 October 2017 / Revised: 26 October 2017 / Accepted: 27 October 2017 / Published: 2 November 2017
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Abstract
Dynamic recrystallization (DRX) processes are widely used in industrial hot working operations, not only to keep the forming forces low but also to control the microstructure and final properties of the workpiece. According to the second derivative criterion (SDC) by Poliak and Jonas,
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Dynamic recrystallization (DRX) processes are widely used in industrial hot working operations, not only to keep the forming forces low but also to control the microstructure and final properties of the workpiece. According to the second derivative criterion (SDC) by Poliak and Jonas, the onset of DRX can be detected from an inflection point in the strain-hardening rate as a function of flow stress. Various models are available that can predict the evolution of flow stress from incipient plastic flow up to steady-state deformation in the presence of DRX. Some of these models have been implemented into finite element codes and are widely used for the design of metal forming processes, but their consistency with the SDC has not been investigated. This work identifies three sources of inconsistencies that models for DRX may exhibit. For a consistent modeling of the DRX kinetics, a new strain-hardening model for the hardening stages III to IV is proposed and combined with consistent recrystallization kinetics. The model is devised in the Kocks-Mecking space based on characteristic transition in the strain-hardening rate. A linear variation of the transition and inflection points is observed for alloy 800H at all tested temperatures and strain rates. The comparison of experimental and model results shows that the model is able to follow the course of the strain-hardening rate very precisely, such that highly accurate flow stress predictions are obtained. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle Evolution of Akaganeite in Rust Layers Formed on Steel Submitted to Wet/Dry Cyclic Tests
Materials 2017, 10(11), 1262; doi:10.3390/ma10111262
Received: 14 September 2017 / Revised: 26 October 2017 / Accepted: 28 October 2017 / Published: 2 November 2017
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Abstract
The evolution of akaganeite in rust layers strongly impacts the atmospheric corrosion behavior of steel during long-term exposure; however, the factors affecting the evolution of akaganeite and its mechanism of formation are vague. In this work, wet-dry cyclic corrosion tests were conducted to
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The evolution of akaganeite in rust layers strongly impacts the atmospheric corrosion behavior of steel during long-term exposure; however, the factors affecting the evolution of akaganeite and its mechanism of formation are vague. In this work, wet-dry cyclic corrosion tests were conducted to simulate long-term exposure. Quantitative X-ray diffraction analysis was employed to analyze variations in the relative amounts of akaganeite; scanning electron microscopy and electron probe microanalysis were used to study the migration of relevant elements in the rust layer, which could help elucidate the mechanism of akaganeite evolution. The results indicate that the fraction of akaganeite tends to decrease as the corrosion process proceeded, which is a result of the decrease in the amount of soluble chloride available and the ability of the thick rust layer to block the migration of relevant ions. This work also explores the location of akaganeite formation within the rust layer. Full article
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Open AccessCommunication Preparation of Palladium/Silver-Coated Polyimide Nanotubes: Flexible, Electrically Conductive Fibers
Materials 2017, 10(11), 1263; doi:10.3390/ma10111263
Received: 21 September 2017 / Revised: 27 October 2017 / Accepted: 2 November 2017 / Published: 2 November 2017
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Abstract
A simple and practical method for coating palladium/silver nanoparticles on polyimide (PI) nanotubes is developed. The key steps involved in the process are silver ion exchange/reduction and displacement reactions between silver and palladium ions. With the addition of silver, the conductivity of the
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A simple and practical method for coating palladium/silver nanoparticles on polyimide (PI) nanotubes is developed. The key steps involved in the process are silver ion exchange/reduction and displacement reactions between silver and palladium ions. With the addition of silver, the conductivity of the PI nanotubes is greatly enhanced. Further, the polyimide nanotubes with a dense, homogeneous coating of palladium nanoparticles remain flexible after heat treatment and show the possibility for use as highly efficient catalysts. The approach developed here is applicable for coating various noble metals on a wide range of polymer matrices, and can be used for obtaining polyimide nanotubes with metal loaded on both the inner and outer surface. Full article
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Open AccessArticle Study on Scattering and Absorption Properties of Quantum-Dot-Converted Elements for Light-Emitting Diodes Using Finite-Difference Time-Domain Method
Materials 2017, 10(11), 1264; doi:10.3390/ma10111264
Received: 31 August 2017 / Revised: 6 October 2017 / Accepted: 30 October 2017 / Published: 3 November 2017
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Abstract
CdSe/ZnS quantum-dot-converted elements (QDCEs) are good candidates for substituting rare-earth phosphor-converted elements (PCEs) in white light-emitting diodes (LEDs); however, studies on their scattering and absorption properties are scarce, suppressing further increment in the optical and thermal performance of quantum-dot-converted LEDs. Therefore, we introduce
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CdSe/ZnS quantum-dot-converted elements (QDCEs) are good candidates for substituting rare-earth phosphor-converted elements (PCEs) in white light-emitting diodes (LEDs); however, studies on their scattering and absorption properties are scarce, suppressing further increment in the optical and thermal performance of quantum-dot-converted LEDs. Therefore, we introduce the finite-difference time-domain (FDTD) method to achieve the critical optical parameters of QDCEs when used in white LEDs; their scattering cross-section (coefficient), absorption cross-section (coefficient), and scattering phase distributions are presented and compared with those of traditional YAG phosphor-converted elements (PCEs) at varying particle size and concentration. At a commonly used concentration ( < 50 mg / cm 3 ), QDCEs exhibit stronger absorption (tens of millimeters, even for green-to-red-wavelength light) and weaker scattering ( < 1 mm 1 ) compared to PCEs; the reabsorption, total internal reflection, angular uniformity, and thermal quenching would be more significant concerns for QDCEs. Therefore, the unique scattering and absorption properties of QDCEs should be considered when used in white LEDs. Furthermore, knowledge of these important optical parameters is helpful for beginning a theoretical study on quantum-dot-converted LEDs according to the ray tracing method. Full article
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Open AccessCommunication Tuning Patchy Bonds Induced by Critical Casimir Forces
Materials 2017, 10(11), 1265; doi:10.3390/ma10111265
Received: 22 September 2017 / Revised: 30 October 2017 / Accepted: 31 October 2017 / Published: 3 November 2017
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Abstract
Experimental control of patchy interactions promises new routes for the assembly of complex colloidal structures, but remains challenging. Here, we investigate the role of patch width in the assembly of patchy colloidal particles assembled by critical Casimir forces. The particles are composed of
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Experimental control of patchy interactions promises new routes for the assembly of complex colloidal structures, but remains challenging. Here, we investigate the role of patch width in the assembly of patchy colloidal particles assembled by critical Casimir forces. The particles are composed of a hydrophobic dumbbell with an equatorial hydrophilic polymer shell, and are synthesized to have well-defined patch-to-shell area ratios. Patch-to-patch binding is achieved in near-critical binary solvents, in which the particle interaction strength and range are controlled by the temperature-dependent solvent correlation length. Upon decreasing the patch-to-shell area ratio, we observe a pronounced change of the bonding morphology towards directed single-bonded configurations, as clearly reflected in the formation of chain-like structures. Computer simulations using an effective critical Casimir pair potential for the patches show that the morphology change results from the geometric exclusion of the increasingly thick hydrophilic particle shells. These results highlight the experimental control of patchy interactions through the engineering of the building blocks on the way towards rationally designed colloidal superstructures. Full article
(This article belongs to the Special Issue Designed Colloidal Self-Assembly)
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Open AccessArticle Effects of Nano-Aluminum Nitride on the Performance of an Ultrahigh-Temperature Inorganic Phosphate Adhesive Cured at Room Temperature
Materials 2017, 10(11), 1266; doi:10.3390/ma10111266
Received: 19 September 2017 / Revised: 31 October 2017 / Accepted: 1 November 2017 / Published: 3 November 2017
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Abstract
Based on the optimal proportion of resin and curing agent, an ultrahigh-temperature inorganic phosphate adhesive was prepared with aluminum dihydric phosphate, aluminium oxide (α-Al2O3), etc. and cured at room temperature (RT). Then, nano-aluminum nitride (nano-AlN), nano-Cupric oxide
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Based on the optimal proportion of resin and curing agent, an ultrahigh-temperature inorganic phosphate adhesive was prepared with aluminum dihydric phosphate, aluminium oxide ( α -Al2O3), etc. and cured at room temperature (RT). Then, nano-aluminum nitride (nano-AlN), nano-Cupric oxide (nano-CuO), and nano-titanium oxide (nano-TiO2) were added into the adhesive. Differential scanning calorimetry was conducted using the inorganic phosphate adhesive to analyze the phosphate reactions during heat treatment, and it was found that 15 wt % nano-AlN could clearly decrease the curing temperature. Scanning electron microscopy was used to observe the microphenomenon of the modified adhesive at ultrahigh-temperature. The differential thermal analysis of the inorganic phosphate adhesive showed that the weight loss was approximately 6.5 wt % when the mass ratio of resin to curing agent was 1:1.5. An X-ray diffraction analysis of the adhesive with 10% nano-AlN showed that the phase structure changed from AlPO4(11-0500) to the more stable AlPO4(10-0423) structure after heat treatment. The shear strength of the adhesive containing 10% nano-AlN reached 7.3 MPa at RT due to the addition of nano-AlN, which promoted the formation of phosphate and increased the Al3+. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Fabrication of a Nano-ZnO/Polyethylene/Wood-Fiber Composite with Enhanced Microwave Absorption and Photocatalytic Activity via a Facile Hot-Press Method
Materials 2017, 10(11), 1267; doi:10.3390/ma10111267
Received: 19 September 2017 / Revised: 26 October 2017 / Accepted: 1 November 2017 / Published: 3 November 2017
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Abstract
A polyethylene/wood-fiber composite loaded with nano-ZnO was prepared by a facile hot-press method and was used for the photocatalytic degradation of organic compounds as well as for microwave absorption. ZnO nanoparticles with an average size of 29 nm and polyethylene (PE) powders were
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A polyethylene/wood-fiber composite loaded with nano-ZnO was prepared by a facile hot-press method and was used for the photocatalytic degradation of organic compounds as well as for microwave absorption. ZnO nanoparticles with an average size of 29 nm and polyethylene (PE) powders were dispersed on the wood fibers’ surface through a viscous cationic polyacrylamide (CPAM) solution. The reflection loss (RL) value of the resulting composite was −21 dB, with a thickness of 3.5 mm in the frequency of 17.17 GHz. The PE/ZnO/wood-fiber (PZW) composite exhibited superior photocatalytic activity (84% methyl orange degradation within 300 min) under UV light irradiation. ZnO nanoparticels (NPs) increased the storage modulus of the PZW composite, and the damping factor was transferred to the higher temperature region. The PZW composite exhibited the maximum flexural strength of 58 MPa and a modulus of elasticity (MOE) of 9625 MPa. Meanwhile, it also displayed dimensional stability (thickness swelling value of 9%). Full article
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Open AccessFeature PaperArticle Amidoxime Polymers for Uranium Adsorption: Influence of Comonomers and Temperature
Materials 2017, 10(11), 1268; doi:10.3390/ma10111268
Received: 27 September 2017 / Revised: 27 October 2017 / Accepted: 31 October 2017 / Published: 4 November 2017
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Abstract
Recovering uranium from seawater has been the subject of many studies for decades, and has recently seen significant progress in materials development since the U.S. Department of Energy (DOE) has become involved. With DOE direction, the uranium uptake for amidoxime-based polymer adsorbents has
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Recovering uranium from seawater has been the subject of many studies for decades, and has recently seen significant progress in materials development since the U.S. Department of Energy (DOE) has become involved. With DOE direction, the uranium uptake for amidoxime-based polymer adsorbents has more than tripled in capacity. In an effort to better understand how these new adsorbent materials behave under different environmental stimuli, several experimental and modeling based studies have been employed to investigate impacts of competing ions, salinity, pH, and other factors on uranium uptake. For this study, the effect of temperature and type of comonomer on uranium adsorption by three different amidoxime adsorbents (AF1, 38H, AI8) was examined. Experimental measurements of uranium uptake were taken in 1−L batch reactors from 10 to 40 °C. A chemisorption model was developed and applied in order to estimate unknown system parameters through optimization. Experimental results demonstrated that the overall uranium chemisorption process for all three materials is endothermic, which was also mirrored in the model results. Model simulations show very good agreement with the data and were able to predict the temperature effect on uranium adsorption as experimental conditions changed. This model may be used for predicting uranium uptake by other amidoxime materials. Full article
(This article belongs to the Special Issue Sorption Materials for Environment Purification)
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Open AccessArticle Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability
Materials 2017, 10(11), 1269; doi:10.3390/ma10111269
Received: 21 September 2017 / Revised: 30 October 2017 / Accepted: 3 November 2017 / Published: 5 November 2017
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Abstract
In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For
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In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these alloys and very good values of mechanical properties. Alloying by chromium ensured the highest thermal stability, while nickel addition refined the structure of the consolidated alloy. High thermal stability of all tested alloys was described in context with the transformation of the quasicrystalline phases to other types of intermetallics. Full article
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Open AccessArticle Dynamic Fracture Behavior of Steel Fiber Reinforced Self-Compacting Concretes (SFRSCCs)
Materials 2017, 10(11), 1270; doi:10.3390/ma10111270
Received: 24 September 2017 / Revised: 25 October 2017 / Accepted: 3 November 2017 / Published: 5 November 2017
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Abstract
Three-point bending tests on notched beams of three types of steel fiber-reinforced self-compacting concrete (SFRSCC) have been performed by using both a servo-hydraulic machine and a drop-weight impact instrument. The lo ading rates had a range of six orders of magnitude from 2.20
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Three-point bending tests on notched beams of three types of steel fiber-reinforced self-compacting concrete (SFRSCC) have been performed by using both a servo-hydraulic machine and a drop-weight impact instrument. The lo ading rates had a range of six orders of magnitude from 2.20 × 10−3 mm/s (quasi-static) to 2.66 × 103 mm/s. These SFRSCCs had the same matrix, but various types of steel fiber (straight and hooked-end) and contents (volume ratios), 0.51%, 0.77% and 1.23%, respectively. The results demonstrate that the fracture energy and the flexural strength increase as the loading rate increases. Moreover, such tendency is relatively moderate at low rates. However, at high rates it is accentuated. For the 0.51% fiber content, the dynamic increase factors of the flexural strength and the fracture energy are approximately 6 and 3, while for the 1.23% fiber content, they are around 4 and 2, respectively. Thus, the higher the fiber content the less rate sensitivity there is. Full article
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Open AccessArticle Statistical Analysis on the Mechanical Properties of Magnesium Alloys
Materials 2017, 10(11), 1271; doi:10.3390/ma10111271
Received: 20 September 2017 / Revised: 30 October 2017 / Accepted: 31 October 2017 / Published: 6 November 2017
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Abstract
Knowledge of statistical characteristics of mechanical properties is very important for the practical application of structural materials. Unfortunately, the scatter characteristics of magnesium alloys for mechanical performance remain poorly understood until now. In this study, the mechanical reliability of magnesium alloys is systematically
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Knowledge of statistical characteristics of mechanical properties is very important for the practical application of structural materials. Unfortunately, the scatter characteristics of magnesium alloys for mechanical performance remain poorly understood until now. In this study, the mechanical reliability of magnesium alloys is systematically estimated using Weibull statistical analysis. Interestingly, the Weibull modulus, m, of strength for magnesium alloys is as high as that for aluminum and steels, confirming the very high reliability of magnesium alloys. The high predictability in the tensile strength of magnesium alloys represents the capability of preventing catastrophic premature failure during service, which is essential for safety and reliability assessment. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Atmospheric Pressure Plasma Polymerization Synthesis and Characterization of Polyaniline Films Doped with and without Iodine
Materials 2017, 10(11), 1272; doi:10.3390/ma10111272
Received: 28 September 2017 / Revised: 24 October 2017 / Accepted: 2 November 2017 / Published: 6 November 2017
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Abstract
Although polymerized aniline (polyaniline, PANI) with and without iodine (I2) doping has already been extensively studied, little work has been done on the synthesis of PANI films using atmospheric pressure plasma (APP) deposition. Therefore, this study characterized pure and I2
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Although polymerized aniline (polyaniline, PANI) with and without iodine (I2) doping has already been extensively studied, little work has been done on the synthesis of PANI films using atmospheric pressure plasma (APP) deposition. Therefore, this study characterized pure and I2-doped PANI films synthesized using an advanced APP polymerization system. The I2 doping was conducted ex-situ and using an I2 chamber method following the APP deposition. The pure and I2-doped PANI films were structurally analyzed using field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry (ToF-SIMS) studies. When increasing the I2 doping time, the plane and cross-sectional SEM images showed a decrease in the width and thickness of the PANI nanofibers, while the AFM results showed an increase in the roughness and grain size of the PANI films. Moreover, the FT-IR, XPS, and ToF-SIMS results showed an increase in the content of oxygen-containing functional groups and C=C double bonds, yet decrease in the C–N and C–H bonds when increasing the I2 doping time due to the reduction of hydrogen in the PANI films via the I2. To check the suitability of the conductive layer for polymer display applications, the resistance variations of the PANI films grown on the interdigitated electrode substrates were also examined according to the I2 doping time. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Surface Modification of Li(Ni0.6Co0.2Mn0.2)O2 Cathode Materials by Nano-Al2O3 to Improve Electrochemical Performance in Lithium-Ion Batteries
Materials 2017, 10(11), 1273; doi:10.3390/ma10111273
Received: 28 September 2017 / Revised: 1 November 2017 / Accepted: 1 November 2017 / Published: 6 November 2017
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Abstract
Al2O3-coated Li(Ni0.6Co0.2Mn0.2)O2 cathode materials were prepared by simple surface modification in water media through a sol-gel process with a dispersant. The crystallinity and surface morphology of the samples were characterized through X-ray
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Al2O3-coated Li(Ni0.6Co0.2Mn0.2)O2 cathode materials were prepared by simple surface modification in water media through a sol-gel process with a dispersant. The crystallinity and surface morphology of the samples were characterized through X-ray diffraction analysis and scanning electron microscopy observation. The Li(Ni0.6Co0.2Mn0.2)O2 cathode material was of a polycrystalline hexagonal structure and agglomerated with particles of approximately 0.3 to 0.8 μm in diameter. The nanosized Al2O3 particles of low concentration (0.06–0.12 wt %) were uniformly coated on the surface of Li(Ni0.6Co0.2Mn0.2)O2. Measurement of electrochemical properties showed that Li(Ni0.6Co0.2Mn0.2)O2 coated with Al2O3 of 0.08 wt % had a high initial discharge capacity of 206.9 mAh/g at a rate of 0.05 C over 3.0–4.5 V and high capacity retention of 94.5% at 0.5 C after 30 cycles (cf. uncoated sample: 206.1 mAh/g and 90.8%, respectively). The rate capability of this material was also improved, i.e., it showed a high discharge capacity of 166.3 mAh/g after 5 cycles at a rate of 2 C, whereas the uncoated sample showed 155.8 mAh/g under the same experimental conditions. Full article
(This article belongs to the Section Energy Materials)
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Open AccessFeature PaperArticle In Vitro Degradation of Borosilicate Bioactive Glass and Poly(l-lactide-co-ε-caprolactone) Composite Scaffolds
Materials 2017, 10(11), 1274; doi:10.3390/ma10111274
Received: 26 September 2017 / Revised: 30 October 2017 / Accepted: 1 November 2017 / Published: 6 November 2017
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Abstract
Composite scaffolds were obtained by mixing various amounts (10, 30 and 50 weight % [wt %]) of borosilicate bioactive glass and poly(l-lactide-co-ε-caprolactone) (PLCL) copolymer. The composites were foamed using supercritical CO2. An increase in the glass content led to
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Composite scaffolds were obtained by mixing various amounts (10, 30 and 50 weight % [wt %]) of borosilicate bioactive glass and poly(l-lactide-co-ε-caprolactone) (PLCL) copolymer. The composites were foamed using supercritical CO2. An increase in the glass content led to a decrease in the pore size and density. In vitro dissolution/reaction test was performed in simulated body fluid. As a function of immersion time, the solution pH increased due to the glass dissolution. This was further supported by the increasing amount of Ca in the immersing solution with increasing immersion time and glass content. Furthermore, the change in scaffold mass was significantly greater with increasing the glass content in the scaffold. However, only the scaffolds containing 30 and 50 wt % of glasses exhibited significant hydroxyapatite (HA) formation at 72 h of immersion. The compression strength of the samples was also measured. The Young’s modulus was similar for the 10 and 30 wt % glass-containing scaffolds whereas it increased to 90 MPa for the 50 wt % glass containing scaffold. Upon immersion up to 72 h, the Young’s modulus increased and then remained constant for longer immersion times. The scaffold prepared could have great potential for bone and cartilage regeneration. Full article
(This article belongs to the Special Issue Bioactive Glasses 2017)
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Open AccessArticle Some Properties of Densified Eastern Redcedar as Function of Heat and Pressure
Materials 2017, 10(11), 1275; doi:10.3390/ma10111275
Received: 31 August 2017 / Revised: 19 October 2017 / Accepted: 24 October 2017 / Published: 7 November 2017
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Abstract
The objective of this study was to evaluate some of the properties of densified eastern redcedar as function of temperature and pressure. Surface quality, adhesive bondline shear strength, hardness, and color changes of the samples compressed using different temperature levels ranging from 100
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The objective of this study was to evaluate some of the properties of densified eastern redcedar as function of temperature and pressure. Surface quality, adhesive bondline shear strength, hardness, and color changes of the samples compressed using different temperature levels ranging from 100 °C to 180 °C were investigated. Based on the findings in this work, surface roughness of compressed specimens decreased with increased temperature. Overall adhesive bondline shear strength of the samples decreased as compared to that of control specimens as a result of compression. It appears that densified samples exposed to a temperature of 180 °C had significantly darker surface than those of the others, based on color measurement. Data found in this work provide some basic information for more efficient use of underutilized species such as eastern redcedar. Full article
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Open AccessArticle Ultra Thin Poly-Si Nanosheet Junctionless Field-Effect Transistor with Nickel Silicide Contact
Materials 2017, 10(11), 1276; doi:10.3390/ma10111276
Received: 21 September 2017 / Revised: 18 October 2017 / Accepted: 2 November 2017 / Published: 7 November 2017
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Abstract
This study demonstrated an ultra thin poly-Si junctionless nanosheet field-effect transistor (JL NS-FET) with nickel silicide contact. For the nickel silicide film, two-step annealing and a Ti capping layer were adopted to form an ultra thin uniform nickel silicide film with low sheet
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This study demonstrated an ultra thin poly-Si junctionless nanosheet field-effect transistor (JL NS-FET) with nickel silicide contact. For the nickel silicide film, two-step annealing and a Ti capping layer were adopted to form an ultra thin uniform nickel silicide film with low sheet resistance (Rs). The JL NS-FET with nickel silicide contact exhibited favorable electrical properties, including a high driving current (>107A), subthreshold slope (186 mV/dec.), and low parasitic resistance. In addition, this study compared the electrical characteristics of JL NS-FETs with and without nickel silicide contact. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Characterization of Sheep Wool as a Sustainable Material for Acoustic Applications
Materials 2017, 10(11), 1277; doi:10.3390/ma10111277
Received: 29 September 2017 / Revised: 2 November 2017 / Accepted: 3 November 2017 / Published: 7 November 2017
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Abstract
In recent years, natural materials are becoming a valid alternative to traditional sound absorbers due to reduced production costs and environmental protection. This paper reports the acoustical characterization of sheep wool. Measurements on normal incidence and diffuse-incidence sound absorption coefficients of different samples
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In recent years, natural materials are becoming a valid alternative to traditional sound absorbers due to reduced production costs and environmental protection. This paper reports the acoustical characterization of sheep wool. Measurements on normal incidence and diffuse-incidence sound absorption coefficients of different samples are reported. The airflow resistance has also been measured. The results prove that sheep wool has a comparable sound absorption performance to that of mineral wool or recycled polyurethane foam. An empirical model is used to calculate the sound absorption of sheep wool samples. A reasonable agreement on the acoustic absorption of all sheep wool samples is obtained. Full article
(This article belongs to the Special Issue Recycled Materials, Eco-design and 3D Printing)
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Open AccessArticle Optimizing Low-Concentration Mercury Removal from Aqueous Solutions by Reduced Graphene Oxide-Supported Fe3O4 Composites with the Aid of an Artificial Neural Network and Genetic Algorithm
Materials 2017, 10(11), 1279; doi:10.3390/ma10111279
Received: 26 October 2017 / Accepted: 4 November 2017 / Published: 7 November 2017
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Abstract
Reduced graphene oxide-supported Fe3O4 (Fe3O4/rGO) composites were applied in this study to remove low-concentration mercury from aqueous solutions with the aid of an artificial neural network (ANN) modeling and genetic algorithm (GA) optimization. The Fe3
[...] Read more.
Reduced graphene oxide-supported Fe3O4 (Fe3O4/rGO) composites were applied in this study to remove low-concentration mercury from aqueous solutions with the aid of an artificial neural network (ANN) modeling and genetic algorithm (GA) optimization. The Fe3O4/rGO composites were prepared by the solvothermal method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), N2-sorption, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and superconduction quantum interference device (SQUID). Response surface methodology (RSM) and ANN were employed to model the effects of different operating conditions (temperature, initial pH, initial Hg ion concentration and contact time) on the removal of the low-concentration mercury from aqueous solutions by the Fe3O4/rGO composites. The ANN-GA model results (with a prediction error below 5%) show better agreement with the experimental data than the RSM model results (with a prediction error below 10%). The removal process of the low-concentration mercury obeyed the Freudlich isotherm and the pseudo-second-order kinetic model. In addition, a regeneration experiment of the Fe3O4/rGO composites demonstrated that these composites can be reused for the removal of low-concentration mercury from aqueous solutions. Full article
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Open AccessFeature PaperArticle Low-Temperature Crystal Structures of the Hard Core Square Shoulder Model
Materials 2017, 10(11), 1280; doi:10.3390/ma10111280
Received: 30 September 2017 / Revised: 22 October 2017 / Accepted: 3 November 2017 / Published: 7 November 2017
PDF Full-text (5423 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In many cases, the stability of complex structures in colloidal systems is enhanced by a competition between different length scales. Inspired by recent experiments on nanoparticles coated with polymers, we use Monte Carlo simulations to explore the types of crystal structures that can
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In many cases, the stability of complex structures in colloidal systems is enhanced by a competition between different length scales. Inspired by recent experiments on nanoparticles coated with polymers, we use Monte Carlo simulations to explore the types of crystal structures that can form in a simple hard-core square shoulder model that explicitly incorporates two favored distances between the particles. To this end, we combine Monte Carlo-based crystal structure finding algorithms with free energies obtained using a mean-field cell theory approach, and draw phase diagrams for two different values of the square shoulder width as a function of the density and temperature. Moreover, we map out the zero-temperature phase diagram for a broad range of shoulder widths. Our results show the stability of a rich variety of crystal phases, such as body-centered orthogonal (BCO) lattices not previously considered for the square shoulder model. Full article
(This article belongs to the Special Issue Designed Colloidal Self-Assembly)
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Open AccessArticle Temperature-Dependent Photoluminescence Emission from Unstrained and Strained GaSe Nanosheets
Materials 2017, 10(11), 1282; doi:10.3390/ma10111282
Received: 30 September 2017 / Revised: 27 October 2017 / Accepted: 7 November 2017 / Published: 8 November 2017
PDF Full-text (2199 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Two-dimensional AIIIBVI layered semiconductors have recently attracted great attention due to their potential applications in piezo-phototronics and optoelectronics. Here, we report the temperature-dependent photoluminescence (PL) of strained and unstrained GaSe flakes. It is found that, as the temperature increases, the
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Two-dimensional AIIIBVI layered semiconductors have recently attracted great attention due to their potential applications in piezo-phototronics and optoelectronics. Here, we report the temperature-dependent photoluminescence (PL) of strained and unstrained GaSe flakes. It is found that, as the temperature increases, the PL from both the strained (wrinkled) and unstrained (flat) positions show a prominent red-shift to low energies. However, for the flat case, the slope of PL energy versus temperature at the range of 163–283 K is about −0.36 meV/K, which is smaller than that of the wrinkled one (−0.5 meV/K). This is because more strain can be introduced at the freestanding wrinkled position during the temperature increase, thus accelerates the main PL peak (peak I, direct band gap transition) shift to lower energy. Additionally, for the wrinkled sheet, three new exciton states (peaks III, IV, and V) appear at the red side of peak I, and the emission intensity is highly dependent on the temperature variation. These peaks can be attributed to the bound exciton recombination. These findings demonstrate an interesting route for optical band gap tuning of the layered GaSe sheet, which are important for future optoelectronic device design. Full article
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Open AccessArticle Tensile Fracture Behavior and Failure Mechanism of Additively-Manufactured AISI 4140 Low Alloy Steel by Laser Engineered Net Shaping
Materials 2017, 10(11), 1283; doi:10.3390/ma10111283
Received: 30 August 2017 / Revised: 6 November 2017 / Accepted: 7 November 2017 / Published: 9 November 2017
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Abstract
AISI 4140 powder was directly deposited on AISI 4140 wrought substrate using laser engineered net shaping (LENS) to investigate the compatibility of a LENS-deposited part with the substrate. Tensile testing at room temperature was performed to evaluate the interface bond performance and fracture
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AISI 4140 powder was directly deposited on AISI 4140 wrought substrate using laser engineered net shaping (LENS) to investigate the compatibility of a LENS-deposited part with the substrate. Tensile testing at room temperature was performed to evaluate the interface bond performance and fracture behavior of the test specimens. All the samples failed within the as-deposited zone, indicating that the interfacial bond is stronger than the interlayer bond inside the deposit. The fracture surfaces were analyzed using scanning electron microscopy (SEM) and energy disperse X-ray spectrometry (EDS). Results show that the tensile fracture failure of the as-deposited part is primarily affected by lack-of-fusion defects, carbide precipitation, and oxide particles inclusions, which causes premature failure of the deposit by deteriorating the mechanical properties and structural integrity. Full article
(This article belongs to the Special Issue Mechanical Properties of Additive Structures in Materials)
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Open AccessArticle New SmAPF Mesogens Designed for Analog Electrooptics Applications
Materials 2017, 10(11), 1284; doi:10.3390/ma10111284
Received: 19 September 2017 / Revised: 17 October 2017 / Accepted: 18 October 2017 / Published: 9 November 2017
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Abstract
We have previously reported the first realization of an orthogonal ferroelectric bent-core SmAPF phase by directed design in mesogens with a single tricarbosilane-terminated alkoxy tail. Given the potentially useful electrooptic properties of this phase, including analog phase-only electrooptic index modulation with optical
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We have previously reported the first realization of an orthogonal ferroelectric bent-core SmAPF phase by directed design in mesogens with a single tricarbosilane-terminated alkoxy tail. Given the potentially useful electrooptic properties of this phase, including analog phase-only electrooptic index modulation with optical latching, we have been exploring its “structure space”, searching for novel SmAPF mesogens. Here, we report two classes of these—the first designed to optimize the dynamic range of the index modulation in parallel-aligned cells by lowering the bend angle of the rigid core, and the second expanding the structure space of the phase by replacing the tricarbosilane-terminated alkyl tail with a polyfluorinated polyethylene glycol oligomer. Full article
(This article belongs to the Special Issue Liquid Crystal-Assisted Advanced Functional Materials)
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Open AccessArticle Bamboo–Polylactic Acid (PLA) Composite Material for Structural Applications
Materials 2017, 10(11), 1286; doi:10.3390/ma10111286
Received: 28 September 2017 / Revised: 24 October 2017 / Accepted: 3 November 2017 / Published: 9 November 2017
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Abstract
Developing an eco-friendly industry based on green materials, sustainable technologies, and optimum processes with low environmental impact is a general societal goal, but this remains a considerable challenge to achieve. Despite the large number of research on green structural composites, limited investigation into
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Developing an eco-friendly industry based on green materials, sustainable technologies, and optimum processes with low environmental impact is a general societal goal, but this remains a considerable challenge to achieve. Despite the large number of research on green structural composites, limited investigation into the most appropriate manufacturing methodology to develop a structural material at industrial level has taken place. Laboratory panels have been manufactured with different natural fibers but the methodologies and values obtained could not be extrapolated at industrial level. Bamboo industry panels have increased in the secondary structural sector such as building application, flooring and sport device, because it is one of the cheapest raw materials. At industrial level, the panels are manufactured with only the inner and intermediate region of the bamboo culm. However, it has been found that the mechanical properties of the external shells of bamboo culm are much better than the average cross-sectional properties. Thin strips of bamboo (1.5 mm thick and 1500 mm long) were machined and arranged with the desired lay-up and shape to obtain laminates with specific properties better than those of conventional E-Glass/Epoxy laminates in terms of both strength and stiffness. The strips of bamboo were bonded together by a natural thermoplastic polylactic acid (PLA) matrix to meet biodegradability requirements. The innovative mechanical extraction process developed in this study can extract natural strip reinforcements with high performance, low cost, and high rate, with no negative environmental impact, as no chemical treatments are used. The process can be performed at the industrial level. Furthermore, in order to validate the structural applications of the composite, the mechanical properties were analyzed under ageing conditions. This material could satisfy the requirements for adequate mechanical properties and life cycle costs at industrial sectors such as energy or automotive. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessFeature PaperArticle Effective Thermal Expansion Property of Consolidated Granular Materials
Materials 2017, 10(11), 1289; doi:10.3390/ma10111289
Received: 9 October 2017 / Revised: 1 November 2017 / Accepted: 2 November 2017 / Published: 9 November 2017
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Abstract
Thermally-assisted compaction of granular materials is of keen interest in many engineering applications. A proper estimation of the material behavior of compacted granular materials is contingent upon the knowledge of microstructure formation, which is highly dependent on the bulk material properties and processing
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Thermally-assisted compaction of granular materials is of keen interest in many engineering applications. A proper estimation of the material behavior of compacted granular materials is contingent upon the knowledge of microstructure formation, which is highly dependent on the bulk material properties and processing conditions, during the deformation stage. Originating from the pair interactions between particles, the macroscopic properties are obtained using various homogenization techniques and postulating continuum constitutive laws. While pioneers in this field have laid fundamental groundwork regarding effective medium descriptions, there exists a discrepancy between discrete and continuum level solutions. In our previous work, we elaborated a Particle Mechanics Approach (PMA) that integrates thermal contact and Hertzian deformation models to understand the thermo-mechanically-coupled consolidation problem. We also considered the analogous problem from the perspective of the conventional Continuum Mechanics Approach (CMA). In this study, following the multi-scale modeling framework, we propose an effective thermal expansion coefficient for the thermally-assisted compaction of granular materials. Full article
(This article belongs to the Special Issue Granular Materials)
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Open AccessFeature PaperArticle The Structure of Liquid and Amorphous Hafnia
Materials 2017, 10(11), 1290; doi:10.3390/ma10111290
Received: 15 October 2017 / Revised: 1 November 2017 / Accepted: 2 November 2017 / Published: 10 November 2017
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Abstract
Understanding the atomic structure of amorphous solids is important in predicting and tuning their macroscopic behavior. Here, we use a combination of high-energy X-ray diffraction, neutron diffraction, and molecular dynamics simulations to benchmark the atomic interactions in the high temperature stable liquid and
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Understanding the atomic structure of amorphous solids is important in predicting and tuning their macroscopic behavior. Here, we use a combination of high-energy X-ray diffraction, neutron diffraction, and molecular dynamics simulations to benchmark the atomic interactions in the high temperature stable liquid and low-density amorphous solid states of hafnia. The diffraction results reveal an average Hf–O coordination number of ~7 exists in both the liquid and amorphous nanoparticle forms studied. The measured pair distribution functions are compared to those generated from several simulation models in the literature. We have also performed ab initio and classical molecular dynamics simulations that show density has a strong effect on the polyhedral connectivity. The liquid shows a broad distribution of Hf–Hf interactions, while the formation of low-density amorphous nanoclusters can reproduce the sharp split peak in the Hf–Hf partial pair distribution function observed in experiment. The agglomeration of amorphous nanoparticles condensed from the gas phase is associated with the formation of both edge-sharing and corner-sharing HfO6,7 polyhedra resembling that observed in the monoclinic phase. Full article
(This article belongs to the Special Issue Characterization of Amorphous Materials)
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Open AccessCommunication Assembly Modulated by Particle Position and Shape: A New Concept in Self-Assembly
Materials 2017, 10(11), 1291; doi:10.3390/ma10111291
Received: 29 September 2017 / Revised: 24 October 2017 / Accepted: 4 November 2017 / Published: 10 November 2017
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Abstract
In this communication we outline how the bespoke arrangements and design of micron-sized superparamagnetic shapes provide levers to modulate their assembly under homogeneous magnetic fields. We label this new approach, ‘assembly modulated by particle position and shape’ (APPS). Specifically, using rectangular lattices of
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In this communication we outline how the bespoke arrangements and design of micron-sized superparamagnetic shapes provide levers to modulate their assembly under homogeneous magnetic fields. We label this new approach, ‘assembly modulated by particle position and shape’ (APPS). Specifically, using rectangular lattices of superparamagnetic micron-sized cuboids, we construct distinct microstructures by adjusting lattice pitch and angle of array with respect to a magnetic field. Broadly, we find two modes of assembly: (1) immediate 2D jamming of the cuboids as they rotate to align with the applied field (rotation-induced jamming) and (2) aggregation via translation after their full alignment (dipole-dipole assembly). The boundary between these two assembly pathways is independent on field strength being solely a function of the cuboid’s dimensions, lattice pitch, and array angle with respect to field—a relationship which we capture, along with other features of the assembly process, in a ‘phase diagram’. In doing so, we set out initial design rules to build custom made assemblies. Moreover, these assemblies can be made flexible thanks to the hinged contacts of their particle building blocks. This flexibility, combined with the superparamagnetic nature of the architectures, renders our assembly method particularly appropriate for the construction of complex actuators at a scale hitherto not possible. Full article
(This article belongs to the Special Issue Designed Colloidal Self-Assembly)
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Open AccessArticle Salt-Assisted Ultrasonicated De-Aggregation and Advanced Redox Electrochemistry of Detonation Nanodiamond
Materials 2017, 10(11), 1292; doi:10.3390/ma10111292
Received: 4 September 2017 / Revised: 19 October 2017 / Accepted: 19 October 2017 / Published: 10 November 2017
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Abstract
Nanodiamond particles form agglomerates in the dry powder state and this poses limitation to the accessibility of their diamond-like core thus dramatically impacting their technological advancement. In this work, we report de-agglomeration of nanodiamond (ND) by using a facile technique namely, salt-assisted ultrasonic
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Nanodiamond particles form agglomerates in the dry powder state and this poses limitation to the accessibility of their diamond-like core thus dramatically impacting their technological advancement. In this work, we report de-agglomeration of nanodiamond (ND) by using a facile technique namely, salt-assisted ultrasonic de-agglomeration (SAUD). Utilizing ultrasound energy and ionic salts (sodium chloride and sodium acetate), SAUD is expected to break apart thermally treated nanodiamond aggregates (~50–100 nm) and produce an aqueous slurry of de-aggregated stable colloidal nanodiamond dispersions by virtue of ionic interactions and electrostatic stabilization. Moreover, the SAUD technique neither has toxic chemicals nor is it difficult to remove impurities and therefore the isolated nanodiamonds produced are exceptionally suited for engineered nanocarbon for mechanical (composites, lubricants) and biomedical (bio-labeling, biosensing, bioimaging, theranostic) applications. We characterized the microscopic structure using complementary techniques including transmission electron microscopy combined with selected-area electron diffraction, optical and vibrational spectroscopy. We immobilized SAUD produced NDs on boron-doped diamond electrodes to investigate fundamental electrochemical properties. They included surface potential (or Fermi energy level), carrier density and mapping electrochemical (re)activity using advanced scanning electrochemical microscopy in the presence of a redox-active probe, with the aim of understanding the surface redox chemistry and the interfacial process of isolated nanodiamond particles as opposed to aggregated and untreated nanoparticles. The experimental findings are discussed in terms of stable colloids, quantum confinement and predominantly surface effects, defect sites (sp2–bonded C and unsaturated bonds), inner core (sp3–bonded C)/outer shell (sp2–bonded C) structure, and surface functionality. Moreover, the surface electronic states give rise to midgap states which serve as electron donors (or acceptors) depending upon the bonding (or antibonding). These are important as electroanalytical platforms for various electrocatalytic processes. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle A New Maraging Stainless Steel with Excellent Strength–Toughness–Corrosion Synergy
Materials 2017, 10(11), 1293; doi:10.3390/ma10111293
Received: 17 October 2017 / Revised: 29 October 2017 / Accepted: 8 November 2017 / Published: 10 November 2017
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Abstract
A new maraging stainless steel with superior strength–toughness–corrosion synergy has been developed based on an innovative concept of alloy design. The high strength–toughness combination is achieved by forming dispersive nano-sized intermetallic compounds in the soft lath martensitic matrix with a slight amount of
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A new maraging stainless steel with superior strength–toughness–corrosion synergy has been developed based on an innovative concept of alloy design. The high strength–toughness combination is achieved by forming dispersive nano-sized intermetallic compounds in the soft lath martensitic matrix with a slight amount of residual austenite. The good corrosion resistance is guaranteed by exactly controlling the Co content based on understanding the synergistic effect between Co and Cr. The fine structure characteristics of two dominant strengthening precipitations including Ni3Ti and Mo-rich phases were finely characterized associated with transmission electron microscope (TEM) and atom probe tomography (APT) analyses. The relationship among microstructure, strength and toughness is discussed. The precipitation mechanism of different precipitates in the new maraging stainless steel is revealed based on the APT analysis. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Application of the Taguchi Method for Optimizing the Process Parameters of Producing Lightweight Aggregates by Incorporating Tile Grinding Sludge with Reservoir Sediments
Materials 2017, 10(11), 1294; doi:10.3390/ma10111294
Received: 24 October 2017 / Revised: 8 November 2017 / Accepted: 9 November 2017 / Published: 10 November 2017
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Abstract
This study aimed to apply the Taguchi optimization technique to determine the process conditions for producing synthetic lightweight aggregate (LWA) by incorporating tile grinding sludge powder with reservoir sediments. An orthogonal array L16(45) was adopted, which consisted of five
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This study aimed to apply the Taguchi optimization technique to determine the process conditions for producing synthetic lightweight aggregate (LWA) by incorporating tile grinding sludge powder with reservoir sediments. An orthogonal array L16(45) was adopted, which consisted of five controllable four-level factors (i.e., sludge content, preheat temperature, preheat time, sintering temperature, and sintering time). Moreover, the analysis of variance method was used to explore the effects of the experimental factors on the particle density, water absorption, bloating ratio, and loss on ignition of the produced LWA. Overall, the produced aggregates had particle densities ranging from 0.43 to 2.1 g/cm3 and water absorption ranging from 0.6% to 13.4%. These values are comparable to the requirements for ordinary and high-performance LWAs. The results indicated that it is considerably feasible to produce high-performance LWA by incorporating tile grinding sludge with reservoir sediments. Full article
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Open AccessArticle Reduced Graphene Oxide on Nickel Foam for Supercapacitor Electrodes
Materials 2017, 10(11), 1295; doi:10.3390/ma10111295
Received: 11 September 2017 / Revised: 6 November 2017 / Accepted: 8 November 2017 / Published: 11 November 2017
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Abstract
The focus of this paper is the investigation of reduced graphene oxide (GO)/nickel foam (RGON) samples for use as supercapacitor electrodes. Nickel foam samples were soaked in a GO suspension and dried before being subjected to two different methods to remove oxygen. Atmospheric
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The focus of this paper is the investigation of reduced graphene oxide (GO)/nickel foam (RGON) samples for use as supercapacitor electrodes. Nickel foam samples were soaked in a GO suspension and dried before being subjected to two different methods to remove oxygen. Atmospheric pressure annealed (APA) samples were treated with a varying number (10–18) of nitrogen plasma jet scans, where sample temperatures did not exceed 280 °C. Furnace annealed (FA) samples were processed in an atmosphere of hydrogen and argon, at temperatures ranging from 600 °C to 900 °C. Environmental Scanning Electron Microscope (ESEM) data indicated that the carbon to oxygen (C:O) ratio for APA samples was minimized at an intermediate number of plasma scans. Fourier Transform Infrared Spectroscopic (FTIR) and Raman spectroscopic data supported this finding. ESEM analysis from FA samples showed that with increasing temperatures of annealing, GO is transformed to reduced graphene oxide (RGO), with C:O ratios exceeding 35:1. X-ray Photoelectron Spectroscopy (XPS) and X-ray diffraction (XRD) data indicated the formation of RGO with an increasing annealing temperature until 800 °C, when oxygen reincorporation in the surface atomic layers becomes an issue. Supercapacitors, constructed using the FA samples, demonstrated performances that correlated with surface atomic layer optimization of the C:O ratio. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle Effect of Relative Humidity on Adsorption Breakthrough of CO2 on Activated Carbon Fibers
Materials 2017, 10(11), 1296; doi:10.3390/ma10111296
Received: 1 September 2017 / Revised: 5 November 2017 / Accepted: 9 November 2017 / Published: 11 November 2017
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Abstract
Microporous activated carbon fibers (ACFs) were developed for CO2 capture based on potassium hydroxide (KOH) activation and tetraethylenepentamine (TEPA) amination. The material properties of the modified ACFs were characterized using several techniques. The adsorption breakthrough curves of CO2 were measured and
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Microporous activated carbon fibers (ACFs) were developed for CO2 capture based on potassium hydroxide (KOH) activation and tetraethylenepentamine (TEPA) amination. The material properties of the modified ACFs were characterized using several techniques. The adsorption breakthrough curves of CO2 were measured and the effect of relative humidity in the carrier gas was determined. The KOH activation at high temperature generated additional pore networks and the intercalation of metallic K into the carbon matrix, leading to the production of mesopore and micropore volumes and providing access to the active sites in the micropores. However, this treatment also resulted in the loss of nitrogen functionalities. The TEPA amination has successfully introduced nitrogen functionalities onto the fiber surface, but its long-chain structure blocked parts of the micropores and, thus, made the available surface area and pore volume limited. Introduction of the power of time into the Wheeler equation was required to fit the data well. The relative humidity within the studied range had almost no effects on the breakthrough curves. It was expected that the concentration of CO2 was high enough so that the impact on CO2 adsorption capacity lessened due to increased relative humidity. Full article
(This article belongs to the Special Issue Selected Papers from IMETI2016)
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Open AccessArticle Fiber-Optic Thermal Sensor for TiN Film Crack Monitoring
Materials 2017, 10(11), 1297; doi:10.3390/ma10111297
Received: 29 September 2017 / Revised: 2 November 2017 / Accepted: 7 November 2017 / Published: 11 November 2017
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Abstract
The study focuses on the thermal and temperature sensitivity behavior of an optical fiber sensor device. In this article, a titanium nitride (TiN)-coated fiber Bragg grating (FBG) sensor fabricated using an ion beam sputtering system was investigated. The reflection spectra of the FBG
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The study focuses on the thermal and temperature sensitivity behavior of an optical fiber sensor device. In this article, a titanium nitride (TiN)-coated fiber Bragg grating (FBG) sensor fabricated using an ion beam sputtering system was investigated. The reflection spectra of the FBG sensor were tested using R-soft optical software to simulate the refractive index sensitivity. In these experiments, the temperature sensitivity of the TiN FBG was measured at temperatures ranging from 100 to 500 °C using an optical spectrum analyzer (OSA). The results showed that the temperature sensitivity of the proposed TiN FBG sensor reached 12.8 pm/°C for the temperature range of 100 to 300 °C and 20.8 pm/°C for the temperature range of 300 to 500 °C. Additionally, we found that the produced oxidation at temperatures of 400-500 °C caused a crack, with the crack becoming more and more obvious at higher and higher temperatures. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICICE 2017)
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Open AccessArticle Chemically Modified Polyvinyl Chloride for Removal of Thionine Dye (Lauth’s Violet)
Materials 2017, 10(11), 1298; doi:10.3390/ma10111298
Received: 18 September 2017 / Revised: 16 October 2017 / Accepted: 26 October 2017 / Published: 12 November 2017
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Abstract
The chemical modification of hydrophobic polymer matrices is an alternative way to elchange their surface properties. The introduction of sulfonic groups in the polymer changes the surface properties such as adhesion, wettability, catalytic ability, and adsorption capacity. This work describes the production and
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The chemical modification of hydrophobic polymer matrices is an alternative way to elchange their surface properties. The introduction of sulfonic groups in the polymer changes the surface properties such as adhesion, wettability, catalytic ability, and adsorption capacity. This work describes the production and application of chemically modified polyvinyl chloride (PVC) as adsorbent for dyes removal. Chemical modification of PVC was evaluated by infrared spectroscopy and elemental analysis, which indicated the presence of sulfonic groups on PVC. The chemically modified PVC (PVCDS) showed an ion exchange capacity of 1.03 mmol−1, and efficiently removed the thionine dye (Lauth’s violet) from aqueous solutions, reaching equilibrium in 30 min. The adsorption kinetics was better adjusted for a pseudo second order model. This result indicates that the adsorption of thionine onto PVCDS occurs by chemisorption. Among the models for the state of equilibrium, SIPS and Langmuir exhibited the best fit to the experimental results and PVCDS showed high adsorption capacities (370 mg−1). Thus, it is assumed that the system presents homogeneous characteristics to the distribution of active sites. The modification promoted the formation of surface characteristics favorable to the dye adsorption by the polymer. Full article
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Open AccessArticle Optically Controllable Linear-Polarization Rotator Using Chiral-Azobenzene-Doped Liquid Crystals
Materials 2017, 10(11), 1299; doi:10.3390/ma10111299
Received: 22 September 2017 / Revised: 5 November 2017 / Accepted: 8 November 2017 / Published: 13 November 2017
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Abstract
A linear-polarization rotator based on the optically tunable pitch of chiral-azobenzene-doped liquid crystals (CAdLCs) has been investigated. It is shown that the orientation of linearly polarized (LP) light can be optically tuned using CAdLCs and that the transmitted light possesses a good degree
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A linear-polarization rotator based on the optically tunable pitch of chiral-azobenzene-doped liquid crystals (CAdLCs) has been investigated. It is shown that the orientation of linearly polarized (LP) light can be optically tuned using CAdLCs and that the transmitted light possesses a good degree of linear polarization (DoLP). Experimental and simulation (4 × 4 Berreman matrix) results show that the rotation angle is dependent on the pitch as well as the number of turns of the cholesteric LC helix. Some causes to affect the DoLP of the output LP lights during photoisomerization are also discussed. Moreover, a calibration term, β(t), is also introduced to elucidate the behavior of the discontinuous change of the CAdLC pitch in a fixed cell thickness. Full article
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Open AccessArticle A First-Principle Theoretical Study of Mechanical and Electronic Properties in Graphene Single-Walled Carbon Nanotube Junctions
Materials 2017, 10(11), 1300; doi:10.3390/ma10111300
Received: 20 October 2017 / Revised: 3 November 2017 / Accepted: 8 November 2017 / Published: 13 November 2017
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Abstract
The new three-dimensional structure that the graphene connected with SWCNTs (G-CNTs, Graphene Single-Walled Carbon Nanotubes) can solve graphene and CNTs′ problems. A comprehensive study of the mechanical and electrical performance of the junctions was performed by first-principles theory. There were eight types of
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The new three-dimensional structure that the graphene connected with SWCNTs (G-CNTs, Graphene Single-Walled Carbon Nanotubes) can solve graphene and CNTs′ problems. A comprehensive study of the mechanical and electrical performance of the junctions was performed by first-principles theory. There were eight types of junctions that were constituted by armchair and zigzag graphene and (3,3), (4,0), (4,4), and (6,0) CNTs. First, the junction strength was investigated. Generally, the binding energy of armchair G-CNTs was stronger than that of zigzag G-CNTs, and it was the biggest in the armchair G-CNTs (6,0). Likewise, the electrical performance of armchair G-CNTs was better than that of zigzag G-CNTs. Charge density distribution of G-CNTs (6,0) was the most homogeneous. Next, the impact factors of the electronic properties of armchair G-CNTs were investigated. We suggest that the band gap is increased with the length of CNTs, and its value should be dependent on the combined effect of both the graphene’s width and the CNTs’ length. Last, the relationship between voltage and current (U/I) were studied. The U/I curve of armchair G-CNTs (6,0) possessed a good linearity and symmetry. These discoveries will contribute to the design and production of G-CNT-based devices. Full article
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Open AccessArticle Influence of KMnO4 Concentrationon Infrared Emissivity of Coatings Formed on TC4 Alloys by Micro-Arc Oxidation
Materials 2017, 10(11), 1301; doi:10.3390/ma10111301
Received: 29 September 2017 / Revised: 9 November 2017 / Accepted: 9 November 2017 / Published: 13 November 2017
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Abstract
Ceramic coatings with high emissivity were fabricated on TC4 alloys by micro-arc oxidation technique (MAO) in mixed silicate and phosphate electrolytes with varying KMnO4 addition. The microstructure, phase and chemical composition were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and
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Ceramic coatings with high emissivity were fabricated on TC4 alloys by micro-arc oxidation technique (MAO) in mixed silicate and phosphate electrolytes with varying KMnO4 addition. The microstructure, phase and chemical composition were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the infrared emissivity of the MAO coatings was measured in a waveband of 5–20 μm. The results show that the thickness of the coatings increased with the addition of KMnO4, but the roughness of the coatings first decreased and then increased slightly due to the inhibitory effect of KMnO4 on Na2SiO3 deposition. The main phase composition of the coatings was anatase and rutile TiO2, amorphous form of SiO2 and MnO2. The infrared emissivity value of the coatings strongly depended on KMnO4 concentration, the coating formed at the concentration of 0.8 g/L KMnO4 reached the highest and an average of up to 0.87 was observed. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Fluorescent Magnetopolymersomes: A Theranostic Platform to Track Intracellular Delivery
Materials 2017, 10(11), 1303; doi:10.3390/ma10111303
Received: 18 October 2017 / Revised: 7 November 2017 / Accepted: 10 November 2017 / Published: 13 November 2017
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Abstract
We present a potential theranostic delivery platform based on the amphiphilic diblock copolymer polybutadiene-block-poly (ethylene oxide) combining covalent fluorescent labeling and membrane incorporation of superparamagnetic iron oxide nanoparticles for multimodal imaging. A simple self-assembly and labeling approach to create the fluorescent
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We present a potential theranostic delivery platform based on the amphiphilic diblock copolymer polybutadiene-block-poly (ethylene oxide) combining covalent fluorescent labeling and membrane incorporation of superparamagnetic iron oxide nanoparticles for multimodal imaging. A simple self-assembly and labeling approach to create the fluorescent and magnetic vesicles is described. Cell uptake of the densely PEGylated polymer vesicles could be altered by surface modifications that vary surface charge and accessibility of the membrane active species. Cell uptake and cytotoxicity were evaluated by confocal microscopy, transmission electron microscopy, iron content and metabolic assays, utilizing multimodal tracking of membrane fluorophores and nanoparticles. Cationic functionalization of vesicles promoted endocytotic uptake. In particular, incorporation of cationic lipids in the polymersome membrane yielded tremendously increased uptake of polymersomes and magnetopolymersomes without increase in cytotoxicity. Ultrastructure investigations showed that cationic magnetopolymersomes disintegrated upon hydrolysis, including the dissolution of incorporated iron oxide nanoparticles. The presented platform could find future use in theranostic multimodal imaging in vivo and magnetically triggered delivery by incorporation of thermorepsonsive amphiphiles that can break the membrane integrity upon magnetic heating via the embedded superparamagnetic nanoparticles. Full article
(This article belongs to the Special Issue Polymeric Materials for Medical Applications)
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Open AccessArticle Morphological Transition in Diamond Thin-Films Induced by Boron in a Microwave Plasma Deposition Process
Materials 2017, 10(11), 1305; doi:10.3390/ma10111305
Received: 22 October 2017 / Revised: 10 November 2017 / Accepted: 12 November 2017 / Published: 14 November 2017
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Abstract
The purpose of this study is to understand the basic mechanisms responsible for the synthesis of nanostructured diamond films in a microwave plasma chemical vapor deposition (MPCVD) process and to identify plasma chemistry suitable for controlling the morphology and electrical properties of deposited
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The purpose of this study is to understand the basic mechanisms responsible for the synthesis of nanostructured diamond films in a microwave plasma chemical vapor deposition (MPCVD) process and to identify plasma chemistry suitable for controlling the morphology and electrical properties of deposited films. The nanostructured diamond films were synthesized by MPCVD on Ti-6Al-4V alloy substrates using H2/CH4/N2 precursor gases and the plasma chemistry was monitored by the optical emission spectroscopy (OES). The synthesized thin-films were characterized by x-ray diffraction and scanning electron microscopy. The addition of B2H6 to the feedgas during MPCVD of diamond thin-films changes the crystal grain size from nanometer to micron scale. Nanostructured diamond films grown with H2/CH4/N2 gases demonstrate a broad (111) Bragg x-ray diffraction peak (Full-Width at Half-Maximum (FWHM) = 0.93° 2θ), indicating a small grain size, whereas scans show a definite sharpening of the diamond (111) peak (FWHM = 0.30° 2θ) with the addition of boron. OES showed a decrease in CN (carbon–nitrogen) radical in the plasma with B2H6 addition to the gas mixture. Our study indicates that CN radical plays a critical role in the synthesis of nanostructured diamond films and suppression of CN radical by boron-addition in the plasma causes a morphological transition to microcrystalline diamond. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Modifying the Morphology of Silicon Surfaces by Laser Induced Liquid Assisted Colloidal Lithography
Materials 2017, 10(11), 1306; doi:10.3390/ma10111306
Received: 13 October 2017 / Revised: 8 November 2017 / Accepted: 10 November 2017 / Published: 14 November 2017
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Abstract
Single, or isolated small arrays of, spherical silica colloidal particles (with refractive index ncolloid = 1.47 and radius R = 350 nm or 1.5 μm) were placed on a silicon substrate and immersed in carbon tetrachloride (nliquid = 1.48) or
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Single, or isolated small arrays of, spherical silica colloidal particles (with refractive index ncolloid = 1.47 and radius R = 350 nm or 1.5 μm) were placed on a silicon substrate and immersed in carbon tetrachloride (nliquid = 1.48) or toluene (nliquid = 1.52). Areas of the sample were then exposed to a single laser pulse (8 ps duration, wavelength λ = 355 nm), and the spatial intensity modulation of the near field in the vicinity of the particles revealed via the resulting patterning of the substrate surface. In this regime, ncolloid < nliquid and the near-field optical intensification is concentrated at and beyond the edge of the particle. Detailed experimental characterization of the irradiated Si surface using atomic force microscopy reveals contrasting topographies. The same optical behavior is observed with both liquids, i.e., the incident laser light diverges on interaction with the colloidal particle, but the resulting interaction with the substrate is liquid dependent. Topographic analysis indicates localized ablation and patterning of the Si substrate when using toluene, whereas the patterning induced under carbon tetrachloride is on a larger scale and extends well below the original substrate surface—hinting at a laser induced photochemical contribution to the surface patterning. Full article
(This article belongs to the Special Issue Designed Colloidal Self-Assembly)
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Open AccessArticle A Statistical Study on the Effect of Hydrostatic Pressure on Metastable Pitting Corrosion of X70 Pipeline Steel
Materials 2017, 10(11), 1307; doi:10.3390/ma10111307
Received: 28 September 2017 / Revised: 7 November 2017 / Accepted: 10 November 2017 / Published: 14 November 2017
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Abstract
Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead
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Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS) results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance. Full article
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Open AccessFeature PaperArticle Ultra-Fast Microwave Synthesis of ZnO Nanorods on Cellulose Substrates for UV Sensor Applications
Materials 2017, 10(11), 1308; doi:10.3390/ma10111308
Received: 31 October 2017 / Revised: 10 November 2017 / Accepted: 12 November 2017 / Published: 15 November 2017
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Abstract
In the present work, tracing and Whatman papers were used as substrates to grow zinc oxide (ZnO) nanostructures. Cellulose-based substrates are cost-efficient, highly sensitive and environmentally friendly. ZnO nanostructures with hexagonal structure were synthesized by hydrothermal under microwave irradiation using an ultrafast approach,
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In the present work, tracing and Whatman papers were used as substrates to grow zinc oxide (ZnO) nanostructures. Cellulose-based substrates are cost-efficient, highly sensitive and environmentally friendly. ZnO nanostructures with hexagonal structure were synthesized by hydrothermal under microwave irradiation using an ultrafast approach, that is, a fixed synthesis time of 10 min. The effect of synthesis temperature on ZnO nanostructures was investigated from 70 to 130 °C. An Ultra Violet (UV)/Ozone treatment directly to the ZnO seed layer prior to microwave assisted synthesis revealed expressive differences regarding formation of the ZnO nanostructures. Structural characterization of the microwave synthesized materials was carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The optical characterization has also been performed. The time resolved photocurrent of the devices in response to the UV turn on/off was investigated and it has been observed that the ZnO nanorod arrays grown on Whatman paper substrate present a responsivity 3 times superior than the ones grown on tracing paper. By using ZnO nanorods, the surface area-to-volume ratio will increase and will improve the sensor sensibility, making these types of materials good candidates for low cost and disposable UV sensors. The sensors were exposed to bending tests, proving their high stability, flexibility and adaptability to different surfaces. Full article
(This article belongs to the Special Issue Zinc Oxide Nanostructures: Synthesis and Characterization)
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Open AccessArticle An Investigation of Polyoxometalate Hybrid Materials as Patternable Dielectrics and Lithographic Resists
Materials 2017, 10(11), 1309; doi:10.3390/ma10111309
Received: 1 November 2017 / Revised: 8 November 2017 / Accepted: 9 November 2017 / Published: 15 November 2017
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Abstract
Polyoxometalate (POM) hybrid materials have shown potential as spin-coatable, patternable dielectric thin-films and components for lithographic resists. In particular, the octamolybdate cluster has been shown to possess good spin-coating properties and the patterning capabilities of hybrid octamolybdate thin-films were explored using a combination
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Polyoxometalate (POM) hybrid materials have shown potential as spin-coatable, patternable dielectric thin-films and components for lithographic resists. In particular, the octamolybdate cluster has been shown to possess good spin-coating properties and the patterning capabilities of hybrid octamolybdate thin-films were explored using a combination of broadband UV and electron beam lithography (EBL) techiniques. Dielectric properties of these films were determined by ellipsometry, and octamolybdate clusters were subsequently investigated as negative resists in various blends for potential uses in next-generation photolithography, where contrast, sensitivity, and line edge roughness characteristics were determined. Preliminary evidence for the suppression of the diffusion of photo-generated acids is presented. Full article
(This article belongs to the Special Issue Polyoxometalate and Nanohybrid Materials)
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Open AccessArticle Anisotropic Failure Strength of Shale with Increasing Confinement: Behaviors, Factors and Mechanism
Materials 2017, 10(11), 1310; doi:10.3390/ma10111310
Received: 25 October 2017 / Revised: 13 November 2017 / Accepted: 13 November 2017 / Published: 15 November 2017
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Abstract
Some studies reported that the anisotropic failure strength of shale will be weakened by increasing confinement. In this paper, it is found that there are various types of anisotropic strength behaviors. Four types of anisotropic strength ratio (SA1) behaviors
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Some studies reported that the anisotropic failure strength of shale will be weakened by increasing confinement. In this paper, it is found that there are various types of anisotropic strength behaviors. Four types of anisotropic strength ratio ( S A 1 ) behaviors and three types of anisotropic strength difference ( S A 2 ) behaviors have been classified based on laboratory experiments on nine groups of different shale samples. The cohesion c w and friction angle ϕ w of the weak planes are proven to be two dominant factors according to a series of bonded-particle discrete element modelling analyses. It is observed that shale is more prone to a slight increase of S A 1 and significant increase of S A 2 with increasing confinement for higher cohesion c w and lower to medium friction angle ϕ w . This study also investigated the mechanism of the anisotropic strength behaviors with increasing confinement. Owing to different contributions of c w and ϕ w under different confinements, different combinations of c w and ϕ w may have various types of influences on the minimum failure strength with the increasing confinement; therefore, different types of anisotropic behaviors occur for different shale specimens as the confinement increases. These findings are very important to understand the stability of wellbore and underground tunneling in the shale rock mass, and should be helpful for further studies on hydraulic fracture propagations in the shale reservoir. Full article
(This article belongs to the Special Issue The Brittle Failure of Different Materials)
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Open AccessArticle Magnetic Material Assessment of a Novel Ultra-High Step-Up Converter with Single Semiconductor Switch and Galvanic Isolation for Fuel-Cell Power System
Materials 2017, 10(11), 1311; doi:10.3390/ma10111311
Received: 26 October 2017 / Revised: 6 November 2017 / Accepted: 6 November 2017 / Published: 15 November 2017
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Abstract
In this paper, a novel step-up converter is proposed, which has the particular features of single semiconductor switch, ultra-high conversion ratio, galvanic isolation, and easy control. Therefore, the proposed converter is suitable for the applications of fuel-cell power system. Coupled inductors and switched
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In this paper, a novel step-up converter is proposed, which has the particular features of single semiconductor switch, ultra-high conversion ratio, galvanic isolation, and easy control. Therefore, the proposed converter is suitable for the applications of fuel-cell power system. Coupled inductors and switched capacitors are incorporated in the converter to obtain an ultra-high voltage ratio that is much higher than that of a conventional high step-up converter. Even if the turns ratio of coupled inductor and duty ratio are only to be 1 and 0.5, respectively, the converter can readily achieve a voltage gain of up to 18. Owing to this outstanding performance, it can also be applied to any other low voltage source for voltage boosting. In the power stage, only one active switch is used to handle the converter operation. In addition, the leakage energy of the two couple inductors can be totally recycled without any snubber, which simplifies the control mechanism and improves the conversion efficiency. Magnetic material dominates the conversion performance of the converter. Different types of iron cores are discussed for the possibility to serve as a coupled inductor. A 200 W prototype with 400 V output voltage is built to validate the proposed converter. In measurement, it indicates that the highest efficiency can be up to 94%. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2017)
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