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Materials, Volume 9, Issue 3 (March 2016)

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Open AccessCommunication Synthesis of Porous Carbon Monoliths Using Hard Templates
Materials 2016, 9(3), 214; https://doi.org/10.3390/ma9030214
Received: 19 November 2015 / Revised: 15 March 2016 / Accepted: 16 March 2016 / Published: 21 March 2016
Cited by 6 | PDF Full-text (4553 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The preparation of porous carbon monoliths with a defined shape via template-assisted routes is reported. Monoliths made from porous concrete and zeolite were each used as the template. The porous concrete-derived carbon monoliths exhibited high gravimetric specific surface areas up to 2000 m
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The preparation of porous carbon monoliths with a defined shape via template-assisted routes is reported. Monoliths made from porous concrete and zeolite were each used as the template. The porous concrete-derived carbon monoliths exhibited high gravimetric specific surface areas up to 2000 m2·g−1. The pore system comprised macro-, meso-, and micropores. These pores were hierarchically arranged. The pore system was created by the complex interplay of the actions of both the template and the activating agent as well. On the other hand, zeolite-made template shapes allowed for the preparation of microporous carbon monoliths with a high volumetric specific surface area. This feature could be beneficial if carbon monoliths must be integrated into technical systems under space-limited conditions. Full article
(This article belongs to the Special Issue Porous Monolithic Materials for Applications in Separation Science)
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Open AccessArticle On the Behavior of Different PCMs in a Hot Water Storage Tank against Thermal Demands
Materials 2016, 9(3), 213; https://doi.org/10.3390/ma9030213
Received: 19 January 2016 / Revised: 11 March 2016 / Accepted: 17 March 2016 / Published: 21 March 2016
Cited by 3 | PDF Full-text (7631 KB) | HTML Full-text | XML Full-text
Abstract
Advantages, such as thermal storage improvement, are found when using PCMs (Phase Change Materials) in storage tanks. The inclusion of three different types of materials in a 60 l test tank is studied. Two test methodologies were developed, and four tests were performed
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Advantages, such as thermal storage improvement, are found when using PCMs (Phase Change Materials) in storage tanks. The inclusion of three different types of materials in a 60 l test tank is studied. Two test methodologies were developed, and four tests were performed following each methodology. A thermal analysis is performed to check the thermal properties of each PCM. The distributions of the water temperatures inside the test tanks are evaluated by installing four Pt-100 sensors at different heights. A temperature recovery is observed after exposing the test tank to an energy demand. An energetic analysis that takes into account the energy due to the water temperature, the energy due to the PCM and the thermal loss to the ambient environment is also presented. The percentage of each PCM that remains in the liquid state after the energy demand is obtained. Full article
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Open AccessFeature PaperArticle Polystyrene-co-Divinylbenzene PolyHIPE Monoliths in 1.0 mm Column Formats for Liquid Chromatography
Materials 2016, 9(3), 212; https://doi.org/10.3390/ma9030212
Received: 18 January 2016 / Revised: 26 February 2016 / Accepted: 15 March 2016 / Published: 18 March 2016
Cited by 1 | PDF Full-text (2064 KB) | HTML Full-text | XML Full-text
Abstract
The reversed phase liquid chromatographic (RP-HPLC) separation of small molecules using a polystyrene-co-divinylbenzene (PS-co-DVB) polyHIPE stationary phases housed within 1.0 mm i.d. silcosteel columns is presented within this study. A 90% PS-co-DVB polyHIPE was covalently attached to
[...] Read more.
The reversed phase liquid chromatographic (RP-HPLC) separation of small molecules using a polystyrene-co-divinylbenzene (PS-co-DVB) polyHIPE stationary phases housed within 1.0 mm i.d. silcosteel columns is presented within this study. A 90% PS-co-DVB polyHIPE was covalently attached to the walls of the column housing by prior wall modification with 3-(trimethoxysilyl) propyl methacrylate and could withstand operating backpressures in excess of 200 bar at a flow rate of 1.2 mL/min. Permeability studies revealed that the monolith swelled slightly in 100% acetonitrile relative to 100% water but could nevertheless be used to separate five alkylbenzenes using a flow rate of 40 µL/min (linear velocity: 0.57 mm/s). Remarkable column-to-column reproducibility is shown with retention factor variation between 2.6% and 6.1% for two separately prepared columns. Full article
(This article belongs to the Special Issue Porous Monolithic Materials for Applications in Separation Science)
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Open AccessArticle Photoassisted Electrochemical Treatment of Azo and Phtalocyanine Reactive Dyes in the Presence of Surfactants
Materials 2016, 9(3), 211; https://doi.org/10.3390/ma9030211
Received: 12 February 2016 / Revised: 10 March 2016 / Accepted: 15 March 2016 / Published: 18 March 2016
Cited by 2 | PDF Full-text (2223 KB) | HTML Full-text | XML Full-text
Abstract
An electrochemical treatment (EC) was applied at different intensities to degrade the chromophoric groups of dyes C.I. Reactive Black 5 (RB5) and C.I. Reactive Blue 7 (Rb7) until uncolored species were obtained. Decolorization rate constants of the azo dye RB5 were higher than
[...] Read more.
An electrochemical treatment (EC) was applied at different intensities to degrade the chromophoric groups of dyes C.I. Reactive Black 5 (RB5) and C.I. Reactive Blue 7 (Rb7) until uncolored species were obtained. Decolorization rate constants of the azo dye RB5 were higher than the phtalocyanine Rb7 ones. In addition, the EC treatment was more efficient at higher intensities, but these conditions significantly increased the generation of undesirable by-products such as chloroform. The combination of EC with UV irradiation (UVEC) drastically minimized the generation of chloroform. The photo-assisted electrochemical treatment was also able to achieve decolorization values of 99%. Finally, mixtures of dyes and surfactants were treated by EC and UVEC. In the presence of surfactants, the decolorization kinetic of dyes was slowed due to the competitive reactions of surfactants degradation. Both methods achieved total decolorization and in both cases, the generation of haloforms was negligible. Full article
(This article belongs to the Special Issue Functional Organic Dyes and Pigments)
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Open AccessArticle Effect of Curing Mode on Shear Bond Strength of Self-Adhesive Cement to Composite Blocks
Materials 2016, 9(3), 210; https://doi.org/10.3390/ma9030210
Received: 17 January 2016 / Revised: 12 March 2016 / Accepted: 15 March 2016 / Published: 18 March 2016
Cited by 2 | PDF Full-text (1574 KB) | HTML Full-text | XML Full-text
Abstract
To overcome the disadvantages of computer-aided design/computer-aided manufacturing (CAD/CAM) processed indirect restorations using glass-ceramics and other ceramics, resin nano ceramic, which has high strength and wear resistance with improved polish retention and optical properties, was introduced. The purpose of this study was to
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To overcome the disadvantages of computer-aided design/computer-aided manufacturing (CAD/CAM) processed indirect restorations using glass-ceramics and other ceramics, resin nano ceramic, which has high strength and wear resistance with improved polish retention and optical properties, was introduced. The purpose of this study was to evaluate the shear bond strength and fracture pattern of indirect CAD/CAM composite blocks cemented with two self-etch adhesive cements with different curing modes. Sand-blasted CAD/CAM composite blocks were cemented using conventional resin cement, Rely X Ultimate Clicker (RXC, 3M ESPE, St. Paul, MN, USA) with Single Bond Universal (SB, 3M ESPE, St. Paul, MN, USA) for the control group or two self-adhesive resin cements: Rely X U200 (RXU, 3M ESPE, St. Paul, MN, USA) and G-CEM Cerasmart (GC, GC corporation, Tokyo, Japan). RXU and GC groups included different curing modes (light-curing (L) and auto-curing (A)). Shear bond strength (SBS) analyses were performed on all the specimens. The RXC group revealed the highest SBS and the GC A group revealed the lowest SBS. According to Tukey’s post hoc test, the RXC group showed a significant difference compared to the GC A group (p < 0.05). For the curing mode, RXU A and RXU L did not show any significant difference between groups and GC A and GC L did not show any significant difference either. Most of the groups except RXC and RXU L revealed adhesive failure patterns predominantly. The RXC group showed a predominant cohesive failure pattern in their CAD/CAM composite, LavaTM Ultimate (LU, 3M ESPE, St. Paul, MN, USA). Within the limitations of this study, no significant difference was found regarding curing modes but more mixed fracture patterns were showed when using the light-curing mode than when using the self-curing mode. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Perpendicular Magnetization Behavior of Low- Temperature Ordered FePt Films with Insertion of Ag Nanolayers
Materials 2016, 9(3), 209; https://doi.org/10.3390/ma9030209
Received: 10 November 2015 / Revised: 16 March 2016 / Accepted: 16 March 2016 / Published: 18 March 2016
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Abstract
FePt-Ag nanocomposite films with large perpendicular magnetic anisotropy have been fabricated by alternate-atomic-layer electron beam evaporation onto MgO(100) substrates at the low temperature of 300 °C. Their magnetization behavior and microstructure have been studied. The surface topography was observed and varied from continuous
[...] Read more.
FePt-Ag nanocomposite films with large perpendicular magnetic anisotropy have been fabricated by alternate-atomic-layer electron beam evaporation onto MgO(100) substrates at the low temperature of 300 °C. Their magnetization behavior and microstructure have been studied. The surface topography was observed and varied from continuous to nanogranular microstructures with insertion of Ag nanolayers into Fe/Pt bilayer films. The measurement of angular-dependent coercivity showed a tendency of the domain-wall motion as a typical peak behavior shift toward more like a coherent Stoner-Wohlfarth rotation type with the insertion of Ag nanolayers into the FePt films. On the other hand, the inter-grain interaction was determined from a Kelly-Henkel plot. The FePt film without insertion of Ag nanolayers has a positive δM, indicating strong exchange coupling between neighboring grains, whereas the FePt film with insertion of Ag nanolayers has a negative δM, indicating that inter-grain exchange coupling is weaker, thus leading to the presence of dipole interaction in the FePt–Ag nanogranular films. The magnetic characteristic measurements confirmed that the perpendicular magnetization reversal behavior and related surface morphology of low-temperature-ordered FePt(001) nanogranular films can be systematically controlled by the insertion of Ag nanolayers into the FePt system for next generation magnetic storage medium applications. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Site-Control of InAs/GaAs Quantum Dots with Indium-Assisted Deoxidation
Materials 2016, 9(3), 208; https://doi.org/10.3390/ma9030208
Received: 21 December 2015 / Revised: 7 March 2016 / Accepted: 11 March 2016 / Published: 18 March 2016
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Abstract
Site-controlled epitaxial growth of InAs quantum dots on GaAs substrates patterned with periodic nanohole arrays relies on the deterministic nucleation of dots into the holes. In the ideal situation, each hole should be occupied exactly by one single dot, with no nucleation onto
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Site-controlled epitaxial growth of InAs quantum dots on GaAs substrates patterned with periodic nanohole arrays relies on the deterministic nucleation of dots into the holes. In the ideal situation, each hole should be occupied exactly by one single dot, with no nucleation onto planar areas. However, the single-dot occupancy per hole is often made difficult by the fact that lithographically-defined holes are generally much larger than the dots, thus providing several nucleation sites per hole. In addition, deposition of a thin GaAs buffer before the dots tends to further widen the holes in the [110] direction. We have explored a method of native surface oxide removal by using indium beams, which effectively prevents hole elongation along [110] and greatly helps single-dot occupancy per hole. Furthermore, as compared to Ga-assisted deoxidation, In-assisted deoxidation is efficient in completely removing surface contaminants, and any excess In can be easily re-desorbed thermally, thus leaving a clean, smooth GaAs surface. Low temperature photoluminescence showed that inhomogeneous broadening is substantially reduced for QDs grown on In-deoxidized patterns, with respect to planar self-assembled dots. Full article
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Open AccessArticle Fatigue Life Prediction of Fiber-Reinforced Ceramic-Matrix Composites with Different Fiber Preforms at Room and Elevated Temperatures
Materials 2016, 9(3), 207; https://doi.org/10.3390/ma9030207
Received: 19 February 2016 / Revised: 7 March 2016 / Accepted: 14 March 2016 / Published: 17 March 2016
Cited by 3 | PDF Full-text (8933 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the fatigue life of fiber-reinforced ceramic-matrix composites (CMCs) with different fiber preforms, i.e., unidirectional, cross-ply, 2D (two dimensional), 2.5D and 3D CMCs at room and elevated temperatures in air and oxidative environments, has been predicted using the micromechanics approach.
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In this paper, the fatigue life of fiber-reinforced ceramic-matrix composites (CMCs) with different fiber preforms, i.e., unidirectional, cross-ply, 2D (two dimensional), 2.5D and 3D CMCs at room and elevated temperatures in air and oxidative environments, has been predicted using the micromechanics approach. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. Under cyclic fatigue loading, the fiber broken fraction was determined by combining the interface wear model and fiber statistical failure model at room temperature, and interface/fiber oxidation model, interface wear model and fiber statistical failure model at elevated temperatures, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfies the Global Load Sharing (GLS) criterion. When the broken fiber fraction approaches the critical value, the composites fatigue fracture. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Nitric Acid-Treated Carbon Fibers with Enhanced Hydrophilicity for Candida tropicalis Immobilization in Xylitol Fermentation
Materials 2016, 9(3), 206; https://doi.org/10.3390/ma9030206
Received: 24 January 2016 / Revised: 4 March 2016 / Accepted: 7 March 2016 / Published: 17 March 2016
Cited by 8 | PDF Full-text (2099 KB) | HTML Full-text | XML Full-text
Abstract
Nitric acid (HNO3)-treated carbon fiber (CF) rich in hydrophilic groups was applied as a cell-immobilized carrier for xylitol fermentation. Using scanning electron microscopy, we characterized the morphology of the HNO3-treated CF. Additionally, we evaluated the immobilized efficiency (IE) of
[...] Read more.
Nitric acid (HNO3)-treated carbon fiber (CF) rich in hydrophilic groups was applied as a cell-immobilized carrier for xylitol fermentation. Using scanning electron microscopy, we characterized the morphology of the HNO3-treated CF. Additionally, we evaluated the immobilized efficiency (IE) of Candida tropicalis and xylitol fermentation yield by investigating the surface properties of nitric acid treated CF, specifically, the acidic group content, zero charge point, degree of moisture and contact angle. We found that adhesion is the major mechanism for cell immobilization and that it is greatly affected by the hydrophilic–hydrophilic surface properties. In our experiments, we found 3 hto be the optimal time for treating CF with nitric acid, resulting in an improved IE of Candida tropicalis of 0.98 g∙g−1 and the highest xylitol yield and volumetric productivity (70.13% and 1.22 g∙L−1∙h−1, respectively). The HNO3-treated CF represents a promising method for preparing biocompatible biocarriers for multi-batch fermentation. Full article
(This article belongs to the Section Biomaterials)
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Open AccessFeature PaperArticle Computational Study of the Effect of Cortical Porosity on Ultrasound Wave Propagation in Healthy and Osteoporotic Long Bones
Materials 2016, 9(3), 205; https://doi.org/10.3390/ma9030205
Received: 23 January 2016 / Revised: 23 February 2016 / Accepted: 8 March 2016 / Published: 17 March 2016
Cited by 4 | PDF Full-text (4835 KB) | HTML Full-text | XML Full-text
Abstract
Computational studies on the evaluation of bone status in cases of pathologies have gained significant interest in recent years. This work presents a parametric and systematic numerical study on ultrasound propagation in cortical bone models to investigate the effect of changes in cortical
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Computational studies on the evaluation of bone status in cases of pathologies have gained significant interest in recent years. This work presents a parametric and systematic numerical study on ultrasound propagation in cortical bone models to investigate the effect of changes in cortical porosity and the occurrence of large basic multicellular units, simply called non-refilled resorption lacunae (RL), on the velocity of the first arriving signal (FAS). Two-dimensional geometries of cortical bone are established for various microstructural models mimicking normal and pathological tissue states. Emphasis is given on the detection of RL formation which may provoke the thinning of the cortical cortex and the increase of porosity at a later stage of the disease. The central excitation frequencies 0.5 and 1 MHz are examined. The proposed configuration consists of one point source and multiple successive receivers in order to calculate the FAS velocity in small propagation paths (local velocity) and derive a variation profile along the cortical surface. It was shown that: (a) the local FAS velocity can capture porosity changes including the occurrence of RL with different number, size and depth of formation; and (b) the excitation frequency 0.5 MHz is more sensitive for the assessment of cortical microstructure. Full article
(This article belongs to the Special Issue Acoustic Waves in Advanced Materials)
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Open AccessArticle Cavitation Erosion of Cermet-Coated Aluminium Bronzes
Materials 2016, 9(3), 204; https://doi.org/10.3390/ma9030204
Received: 22 January 2016 / Revised: 9 March 2016 / Accepted: 10 March 2016 / Published: 17 March 2016
Cited by 1 | PDF Full-text (4889 KB) | HTML Full-text | XML Full-text
Abstract
The cavitation erosion resistance of CuAl10Ni5Fe2.5Mn1 following plasma spraying with Al2O3·30(Ni20Al) powder and laser re-melting was analyzed in view of possible improvements of the lifetime of components used in hydraulic environments. The cavitation erosion resistance was substantially
[...] Read more.
The cavitation erosion resistance of CuAl10Ni5Fe2.5Mn1 following plasma spraying with Al2O3·30(Ni20Al) powder and laser re-melting was analyzed in view of possible improvements of the lifetime of components used in hydraulic environments. The cavitation erosion resistance was substantially improved compared with the one of the base material. The thickness of the re-melted layer was in the range of several hundred micrometers, with a surface microhardness increasing from 250 to 420 HV 0.2. Compositional, structural, and microstructural explorations showed that the microstructure of the re-melted and homogenized layer, consisting of a cubic Al2O3 matrix with dispersed Ni-based solid solution is associated with the hardness increase and consequently with the improvement of the cavitation erosion resistance. Full article
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Open AccessArticle Surface Morphology and Tooth Adhesion of a Novel Nanostructured Dental Restorative Composite
Materials 2016, 9(3), 203; https://doi.org/10.3390/ma9030203
Received: 1 February 2016 / Revised: 17 February 2016 / Accepted: 26 February 2016 / Published: 16 March 2016
Cited by 4 | PDF Full-text (892 KB) | HTML Full-text | XML Full-text
Abstract
Recently, a novel dental restorative composite based on nanostructured micro-fillers of anodic porous alumina has been proposed. While its bulk properties are promising thanks to decreased aging and drug delivery capabilities, its surface properties are still unknown. Here we investigated the surface morphology
[...] Read more.
Recently, a novel dental restorative composite based on nanostructured micro-fillers of anodic porous alumina has been proposed. While its bulk properties are promising thanks to decreased aging and drug delivery capabilities, its surface properties are still unknown. Here we investigated the surface morphology and the adhesion to tooth dentin of this composite as prepared. For comparison, we used two commercial composites: Tetric EVO Flow (Ivoclar) and Enamel HRi Plus (Micerium). The surface morphology was characterized by atomic force microscopy and the adhesion strength by tensile tests. The experimental composite is rougher than the commercial composites, with root mean square roughness of ~549 nm against 170–511 nm, and presents an adhesion strength of ~15 MPa against 19–21 MPa. These results show at the same time some proximity to the commercial composites, but also the need for optimization of the experimental material formulation. Full article
(This article belongs to the Section Biomaterials)
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Open AccessFeature PaperArticle Study of Polydiacetylene-Poly (Ethylene Oxide) Electrospun Fibers Used as Biosensors
Materials 2016, 9(3), 202; https://doi.org/10.3390/ma9030202
Received: 31 January 2016 / Revised: 5 March 2016 / Accepted: 7 March 2016 / Published: 16 March 2016
Cited by 7 | PDF Full-text (3460 KB) | HTML Full-text | XML Full-text
Abstract
Polydiacetylene (PDA) is an attractive conjugated material for use in biosensors due to its unique characteristic of undergoing a blue-to-red color change in response to external stimuli. 10,12-Pentacosadiynoic acid (PCDA) and poly (ethylene oxide) (PEO) were used in this study to develop fiber
[...] Read more.
Polydiacetylene (PDA) is an attractive conjugated material for use in biosensors due to its unique characteristic of undergoing a blue-to-red color change in response to external stimuli. 10,12-Pentacosadiynoic acid (PCDA) and poly (ethylene oxide) (PEO) were used in this study to develop fiber composites via an electrospinning method at various mass ratios of PEO to PCDA, solution concentrations, and injection speeds. The PEO-PDA fibers in blue phase were obtained via photo-polymerization upon UV-light irritation. High mass ratios of PEO to PCDA, low polymer concentrations of spinning solution, and low injection speeds promoted fine fibers with small diameters and smooth surfaces. The colorimetric transition of the fibers was investigated when the fibers were heated at temperatures ranging from 25 °C to 120 °C. A color switch from blue to red in the fibers was observed when the fibers were heated at temperatures greater than 60 °C. The color transition was more sensitive in the fibers made with a low mass ratio of PEO to PCDA due to high fraction of PDA in the fibers. The large diameter fibers also promoted the color switch due to high reflectance area in the fibers. All of the fibers were analyzed using Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) and compared before and after the color change occurred. The colorimetric transitional mechanism is proposed to occur due to conformational changes in the PDA macromolecules. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessFeature PaperArticle Controlled Photocatalytic Synthesis of Core–Shell SiC/Polyaniline Hybrid Nanostructures
Materials 2016, 9(3), 201; https://doi.org/10.3390/ma9030201
Received: 31 January 2016 / Revised: 4 March 2016 / Accepted: 7 March 2016 / Published: 16 March 2016
Cited by 8 | PDF Full-text (4450 KB) | HTML Full-text | XML Full-text
Abstract
Hybrid materials of electrically conducting polymers and inorganic semiconductors form an exciting class of functional materials. To fully exploit the potential synergies of the hybrid formation, however, sophisticated synthetic methods are required that allow for the fine-tuning of the nanoscale structure of the
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Hybrid materials of electrically conducting polymers and inorganic semiconductors form an exciting class of functional materials. To fully exploit the potential synergies of the hybrid formation, however, sophisticated synthetic methods are required that allow for the fine-tuning of the nanoscale structure of the organic/inorganic interface. Here we present the photocatalytic deposition of a conducting polymer (polyaniline) on the surface of silicon carbide (SiC) nanoparticles. The polymerization is facilitated on the SiC surface, via the oxidation of the monomer molecules by ultraviolet-visible (UV-vis) light irradiation through the photogenerated holes. The synthesized core–shell nanostructures were characterized by UV-vis, Raman, and Fourier Transformed Infrared (FT-IR) Spectroscopy, thermogravimetric analysis, transmission and scanning electron microscopy, and electrochemical methods. It was found that the composition of the hybrids can be varied by simply changing the irradiation time. In addition, we proved the crucial importance of the irradiation wavelength in forming conductive polyaniline, instead of its overoxidized, insulating counterpart. Overall, we conclude that photocatalytic deposition is a promising and versatile approach for the synthesis of conducting polymers with controlled properties on semiconductor surfaces. The presented findings may trigger further studies using photocatalysis as a synthetic strategy to obtain nanoscale hybrid architectures of different semiconductors. Full article
(This article belongs to the Special Issue Advancement of Photocatalytic Materials 2016)
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Open AccessArticle Effect of Chromium on Corrosion Behavior of P110 Steels in CO2-H2S Environment with High Pressure and High Temperature
Materials 2016, 9(3), 200; https://doi.org/10.3390/ma9030200
Received: 22 January 2016 / Revised: 5 March 2016 / Accepted: 8 March 2016 / Published: 16 March 2016
Cited by 16 | PDF Full-text (7075 KB) | HTML Full-text | XML Full-text
Abstract
The novel Cr-containing low alloy steels have exhibited good corrosion resistance in CO2 environment, mainly owing to the formation of Cr-enriched corrosion film. In order to evaluate whether it is applicable to the CO2 and H2S coexistence conditions, the
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The novel Cr-containing low alloy steels have exhibited good corrosion resistance in CO2 environment, mainly owing to the formation of Cr-enriched corrosion film. In order to evaluate whether it is applicable to the CO2 and H2S coexistence conditions, the corrosion behavior of low-chromium steels in CO2-H2S environment with high pressure and high temperature was investigated using weight loss measurement and surface characterization. The results showed that P110 steel suffered localized corrosion and both 3Cr-P110 and 5Cr-P110 steels exhibited general corrosion. However, the corrosion rate of 5Cr-P110 was the highest among them. The corrosion process of the steels was simultaneously governed by CO2 and H2S. The outer scales on the three steels mainly consisted of FeS1−x crystals, whereas the inner scales on Cr-containing steels comprised of amorphous FeS1−x, Cr(OH)3 and FeCO3, in contrast with the amorphous FeS1−x and FeCO3 mixture film of P110 steel. The more chromium the steel contains, the more chromium compounds the corrosion products contain. The addition of chromium in steels increases the uniformity of the Cr-enriched corrosion scales, eliminates the localized corrosion, but cannot decrease the general corrosion rates. The formation of FeS1−x may interfere with Cr-enriched corrosion scales and lowering the corrosion performance of 3Cr-P110 and 5Cr-P110 steels. Full article
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Open AccessArticle Semisolid Microstructural Evolution during Partial Remelting of a Bulk Alloy Prepared by Cold Pressing of the Ti-Al-2024Al Powder Mixture
Materials 2016, 9(3), 199; https://doi.org/10.3390/ma9030199
Received: 15 December 2015 / Revised: 29 February 2016 / Accepted: 9 March 2016 / Published: 16 March 2016
Cited by 5 | PDF Full-text (10376 KB) | HTML Full-text | XML Full-text
Abstract
A new method, powder thixoforming, has been proposed to fabricate an in situ Al3Tip/2024Al composite. During partial remelting, the microstructural evolution of the bulk alloy prepared by cold pressing of the Ti, Al, 2024Al powder mixture was investigated, and
[...] Read more.
A new method, powder thixoforming, has been proposed to fabricate an in situ Al3Tip/2024Al composite. During partial remelting, the microstructural evolution of the bulk alloy prepared by cold pressing of the Ti, Al, 2024Al powder mixture was investigated, and the formation mechanism of the Al3Ti particles produced by the reaction between the Ti powder and the Al alloy melt is also discussed in detail. The results indicate that the microstructural evolution of the 2024 alloy matrix can be divided into three stages: a rapid coarsening of the powder grains; a formation of primary α-Al particles surrounded with a continuous liquid film; and a slight coarsening of the primary α-Al particles. Simultaneously, a reaction layer of Al3Ti can be formed on the Ti powder surface when the bulk is heated for 10 min at 640 °C The thickness (X) of the reaction layer increases with the time according to the parabolic law of \(X = -0.43t^{2} + 4.21t + 0.17\). The stress generated in the reaction layer due to the volume dilatation can be calculated by using the equationσ \(\sigma_{Al_{3}Ti} = -\frac{ E_{Al_{3}Ti} }{6(1-v{Al_{3}Ti})} \frac{ t^{3}_{Al_{3}Ti} }{t_{Ti}} \left(\frac{1}{R} - \frac{1}{R_{0}} \right) \). Comparing the obtained data with the results of the drip experiment, the reaction rate for the Ti powder and Al powder mixture is greater than that for the Ti plate and Al alloy mixture, respectively. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Development and Characterization of a Bioinspired Bone Matrix with Aligned Nanocrystalline Hydroxyapatite on Collagen Nanofibers
Materials 2016, 9(3), 198; https://doi.org/10.3390/ma9030198
Received: 29 January 2016 / Revised: 2 March 2016 / Accepted: 10 March 2016 / Published: 15 March 2016
Cited by 7 | PDF Full-text (3078 KB) | HTML Full-text | XML Full-text
Abstract
Various kinds of three-dimensional (3D) scaffolds have been designed to mimic the biological spontaneous bone formation characteristics by providing a suitable microenvironment for osteogenesis. In view of this, a natural bone-liked composite scaffold, which was combined with inorganic (hydroxyapatite, Hap) and organic (type
[...] Read more.
Various kinds of three-dimensional (3D) scaffolds have been designed to mimic the biological spontaneous bone formation characteristics by providing a suitable microenvironment for osteogenesis. In view of this, a natural bone-liked composite scaffold, which was combined with inorganic (hydroxyapatite, Hap) and organic (type I collagen, Col) phases, has been developed through a self-assembly process. This 3D porous scaffold consisting of a c-axis of Hap nanocrystals (nHap) aligning along Col fibrils arrangement is similar to natural bone architecture. A significant increase in mechanical strength and elastic modulus of nHap/Col scaffold is achieved through biomimetic mineralization process when compared with simple mixture of collagen and hydroxyapatite method. It is suggested that the self-organization of Hap and Col produced in vivo could also be achieved in vitro. The oriented nHap/Col composite not only possesses bone-like microstructure and adequate mechanical properties but also enhances the regeneration and reorganization abilities of bone tissue. These results demonstrated that biomimetic nHap/Col can be successfully reconstructed as a bone graft substitute in bone tissue engineering. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Post Processing and Biological Evaluation of the Titanium Scaffolds for Bone Tissue Engineering
Materials 2016, 9(3), 197; https://doi.org/10.3390/ma9030197
Received: 1 February 2016 / Revised: 25 February 2016 / Accepted: 7 March 2016 / Published: 15 March 2016
Cited by 14 | PDF Full-text (9466 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, post-surgical or post-accidental bone loss can be substituted by custom-made scaffolds fabricated by additive manufacturing (AM) methods from metallic powders. However, the partially melted powder particles must be removed in a post-process chemical treatment. The aim of this study was to investigate
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Nowadays, post-surgical or post-accidental bone loss can be substituted by custom-made scaffolds fabricated by additive manufacturing (AM) methods from metallic powders. However, the partially melted powder particles must be removed in a post-process chemical treatment. The aim of this study was to investigate the effect of the chemical polishing with various acid baths on novel scaffolds’ morphology, porosity and mechanical properties. In the first stage, Magics software (Materialise NV, Leuven, Belgium) was used to design a porous scaffolds with pore size equal to (A) 200 µm, (B) 500 µm and (C) 200 + 500 µm, and diamond cell structure. The scaffolds were fabricated from commercially pure titanium powder (CP Ti) using a SLM50 3D printing machine (Realizer GmbH, Borchen, Germany). The selective laser melting (SLM) process was optimized and the laser beam energy density in range of 91–151 J/mm3 was applied to receive 3D structures with fully dense struts. To remove not fully melted titanium particles the scaffolds were chemically polished using various HF and HF-HNO3 acid solutions. Based on scaffolds mass loss and scanning electron (SEM) observations, baths which provided most uniform surface cleaning were proposed for each porosity. The pore and strut size after chemical treatments was calculated based on the micro-computed tomography (µ-CT) and SEM images. The mechanical tests showed that the treated scaffolds had Young’s modulus close to that of compact bone. Additionally, the effect of pore size of chemically polished scaffolds on cell retention, proliferation and differentiation was studied using human mesenchymal stem cells. Small pores yielded higher cell retention within the scaffolds, which then affected their growth. This shows that in vitro cell performance can be controlled to certain extent by varying pore sizes. Full article
(This article belongs to the Special Issue Metallic Scaffolds for Bone Regeneration)
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Open AccessFeature PaperArticle Blazed Gratings Recorded in Absorbent Photopolymers
Materials 2016, 9(3), 195; https://doi.org/10.3390/ma9030195
Received: 25 January 2016 / Revised: 29 February 2016 / Accepted: 8 March 2016 / Published: 15 March 2016
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Abstract
Phase diffractive optical elements, which have many interesting applications, are usually fabricated using a photoresist. In this paper, they were made using a hybrid optic-digital system and a photopolymer as recording medium. We analyzed the characteristics of the input and recording light and
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Phase diffractive optical elements, which have many interesting applications, are usually fabricated using a photoresist. In this paper, they were made using a hybrid optic-digital system and a photopolymer as recording medium. We analyzed the characteristics of the input and recording light and then simulated the generation of blazed gratings with different spatial periods in different types of photopolymers using a diffusion model. Finally, we analyzed the output and diffraction efficiencies of the 0 and 1st order so as to compare the simulated values with those measured experimentally. We evaluated the effects of index matching in a standard PVA/AA photopolymer, and in a variation of Biophotopol, a more biocompatible photopolymer. Diffraction efficiencies near 70%, for a wavelength of 633 nm, were achieved for periods longer than 300 µm in this kind of materials. Full article
(This article belongs to the Special Issue Photopolymers for Holographic Applications)
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Open AccessFeature PaperArticle Influence of 4,4’-azobis (4-cyanopentanoic acid) in Transmission and Reflection Gratings Stored in a PVA/AA Photopolymer
Materials 2016, 9(3), 194; https://doi.org/10.3390/ma9030194
Received: 27 January 2016 / Revised: 1 March 2016 / Accepted: 4 March 2016 / Published: 15 March 2016
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Abstract
Holographic transmission gratings with a spatial frequency of 2658 lines/mm and reflection gratings with a spatial frequency of 4553 lines/mm were stored in a polyvinyl alcohol (PVA)/acrylamide (AA) based photopolymer. This material can reach diffraction efficiencies close to 100% for spatial frequencies about
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Holographic transmission gratings with a spatial frequency of 2658 lines/mm and reflection gratings with a spatial frequency of 4553 lines/mm were stored in a polyvinyl alcohol (PVA)/acrylamide (AA) based photopolymer. This material can reach diffraction efficiencies close to 100% for spatial frequencies about 1000 lines/mm. However, for higher spatial frequencies, the diffraction efficiency decreases considerably as the spatial frequency increases. To enhance the material response at high spatial frequencies, a chain transfer agent, the 4,4’-azobis (4-cyanopentanoic acid), ACPA, is added to the composition of the material. Different concentrations of ACPA are incorporated into the main composition of the photopolymer to find the concentration value that provides the highest diffraction efficiency. Moreover, the refractive index modulation and the optical thickness of the transmission and reflection gratings were obtained, evaluated and compared to procure more information about the influence of the ACPA on them. Full article
(This article belongs to the Special Issue Photopolymers for Holographic Applications)
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Open AccessArticle Preparation and Characterization of All-Biomass Soy Protein Isolate-Based Films Enhanced by Epoxy Castor Oil Acid Sodium and Hydroxypropyl Cellulose
Materials 2016, 9(3), 193; https://doi.org/10.3390/ma9030193
Received: 25 January 2016 / Revised: 28 February 2016 / Accepted: 2 March 2016 / Published: 15 March 2016
Cited by 5 | PDF Full-text (3195 KB) | HTML Full-text | XML Full-text
Abstract
All-biomass soy protein-based films were prepared using soy protein isolate (SPI), glycerol, hydroxypropyl cellulose (HPC) and epoxy castor oil acid sodium (ECOS). The effect of the incorporated HPC and ECOS on the properties of the SPI film was investigated. The experimental results showed
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All-biomass soy protein-based films were prepared using soy protein isolate (SPI), glycerol, hydroxypropyl cellulose (HPC) and epoxy castor oil acid sodium (ECOS). The effect of the incorporated HPC and ECOS on the properties of the SPI film was investigated. The experimental results showed that the tensile strength of the resultant films increased from 2.84 MPa (control) to 4.04 MPa and the elongation at break increased by 22.7% when the SPI was modified with 2% HPC and 10% ECOS. The increased tensile strength resulted from the reaction between the ECOS and SPI, which was confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). It was found that ECOS and HPC effectively improved the performance of SPI-based films, which can provide a new method for preparing environmentally-friendly polymer films for a number of commercial applications. Full article
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Open AccessArticle Molecular Mobility in Hyperbranched Polymers and Their Interaction with an Epoxy Matrix
Materials 2016, 9(3), 192; https://doi.org/10.3390/ma9030192
Received: 21 December 2015 / Accepted: 10 March 2016 / Published: 15 March 2016
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Abstract
The molecular mobility related to the glass transition and secondary relaxations in a hyperbranched polyethyleneimine, HBPEI, and its relaxation behaviour when incorporated into an epoxy resin matrix are investigated by dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA). Three systems are analysed:
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The molecular mobility related to the glass transition and secondary relaxations in a hyperbranched polyethyleneimine, HBPEI, and its relaxation behaviour when incorporated into an epoxy resin matrix are investigated by dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA). Three systems are analysed: HBPEI, epoxy and an epoxy/HBPEI mixture, denoted ELP. The DRS behaviour is monitored in the ELP system in three stages: prior to curing, during curing, and in the fully cured system. In the stage prior to curing, DRS measurements show three dipolar relaxations: γ, β and α, for all systems (HBPEI, epoxy and ELP). The α-relaxation for the ELP system deviates significantly from that for HBPEI, but superposes on that for the epoxy resin. The fully cured thermoset displays both β- and α-relaxations. In DMA measurements, both α- and β-relaxations are observed in all systems and in both the uncured and fully cured systems, similar to the behaviour identified by DRS. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Nanotextured Shrink Wrap Superhydrophobic Surfaces by Argon Plasma Etching
Materials 2016, 9(3), 196; https://doi.org/10.3390/ma9030196
Received: 11 January 2016 / Revised: 3 March 2016 / Accepted: 3 March 2016 / Published: 14 March 2016
Cited by 7 | PDF Full-text (2825 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We present a rapid, simple, and scalable approach to achieve superhydrophobic (SH) substrates directly in commodity shrink wrap film utilizing Argon (Ar) plasma. Ar plasma treatment creates a stiff skin layer on the surface of the shrink film. When the film shrinks, the
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We present a rapid, simple, and scalable approach to achieve superhydrophobic (SH) substrates directly in commodity shrink wrap film utilizing Argon (Ar) plasma. Ar plasma treatment creates a stiff skin layer on the surface of the shrink film. When the film shrinks, the mismatch in stiffness between the stiff skin layer and bulk shrink film causes the formation of multiscale hierarchical wrinkles with nano-textured features. Scanning electron microscopy (SEM) images confirm the presence of these biomimetic structures. Contact angle (CA) and contact angle hysteresis (CAH) measurements, respectively, defined as values greater than 150° and less than 10°, verified the SH nature of the substrates. Furthermore, we demonstrate the ability to reliably pattern hydrophilic regions onto the SH substrates, allowing precise capture and detection of proteins in urine. Finally, we achieved self-driven microfluidics via patterning contrasting superhydrophilic microchannels on the SH Ar substrates to induce flow for biosensing. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Materials)
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Open AccessArticle A Novel HA/β-TCP-Collagen Composite Enhanced New Bone Formation for Dental Extraction Socket Preservation in Beagle Dogs
Materials 2016, 9(3), 191; https://doi.org/10.3390/ma9030191
Received: 9 November 2015 / Revised: 7 March 2016 / Accepted: 9 March 2016 / Published: 11 March 2016
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Abstract
Past studies in humans have demonstrated horizontal and vertical bone loss after six months following tooth extraction. Many biomaterials have been developed to preserve bone volume after tooth extraction. Type I collagen serves as an excellent delivery system for growth factors and promotes
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Past studies in humans have demonstrated horizontal and vertical bone loss after six months following tooth extraction. Many biomaterials have been developed to preserve bone volume after tooth extraction. Type I collagen serves as an excellent delivery system for growth factors and promotes angiogenesis. Calcium phosphate ceramics have also been investigated because their mineral chemistry resembles human bone. The aim of this study was to compare the performance of a novel bioresorbable purified fibrillar collagen and hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) ceramic composite versus collagen alone and a bovine xenograft-collagen composite in beagles. Collagen plugs, bovine graft-collagen composite and HA/β-TCP-collagen composite were implanted into the left and right first, second and third mandibular premolars, and the fourth molar was left empty for natural healing. In total, 20 male beagle dogs were used, and quantitative and histological analyses of the extraction ridge was done. The smallest width reduction was 19.09% ± 8.81% with the HA/β-TCP-collagen composite at Week 8, accompanied by new bone formation at Weeks 4 and 8. The HA/β-TCP-collagen composite performed well, as a new osteoconductive and biomimetic composite biomaterial, for socket bone preservation after tooth extraction. Full article
(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)
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Open AccessReview Repopulating Decellularized Kidney Scaffolds: An Avenue for Ex Vivo Organ Generation
Materials 2016, 9(3), 190; https://doi.org/10.3390/ma9030190
Received: 15 December 2015 / Revised: 1 March 2016 / Accepted: 4 March 2016 / Published: 11 March 2016
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Abstract
Recent research has shown that fully developed organs can be decellularized, resulting in a complex scaffold and extracellular matrix (ECM) network capable of being populated with other cells. This work has resulted in a growing field in bioengineering focused on the isolation, characterization,
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Recent research has shown that fully developed organs can be decellularized, resulting in a complex scaffold and extracellular matrix (ECM) network capable of being populated with other cells. This work has resulted in a growing field in bioengineering focused on the isolation, characterization, and modification of organ derived acellular scaffolds and their potential to sustain and interact with new cell populations, a process termed reseeding. In this review, we cover contemporary advancements in the bioengineering of kidney scaffolds including novel work showing that reseeded donor scaffolds can be transplanted and can function in recipients using animal models. Several major areas of the field are taken into consideration, including the decellularization process, characterization of acellular and reseeded scaffolds, culture conditions, and cell sources. Finally, we discuss future avenues based on the advent of 3D bioprinting and recent developments in kidney organoid cultures as well as animal models of renal genesis. The ongoing mergers and collaborations between these fields hold the potential to produce functional kidneys that can be generated ex vivo and utilized for kidney transplantations in patients suffering with renal disease. Full article
(This article belongs to the Special Issue Regenerative Materials)
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Open AccessArticle Thermal Mechanical Processing Effects on Microstructure Evolution and Mechanical Properties of the Sintered Ti-22Al-25Nb Alloy
Materials 2016, 9(3), 189; https://doi.org/10.3390/ma9030189
Received: 4 January 2016 / Revised: 26 February 2016 / Accepted: 29 February 2016 / Published: 11 March 2016
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Abstract
This work illustrates the effect of thermal mechanical processing parameters on the microstructure and mechanical properties of the Ti-22Al-25Nb alloy prepared by reactive sintering with element powders, consisting of O, B2 and Ti3Al phases. Tensile and plane strain fracture toughness tests
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This work illustrates the effect of thermal mechanical processing parameters on the microstructure and mechanical properties of the Ti-22Al-25Nb alloy prepared by reactive sintering with element powders, consisting of O, B2 and Ti3Al phases. Tensile and plane strain fracture toughness tests were carried out at room temperature to understand the mechanical behavior of the alloys and its correlation with the microstructural features characterized by scanning and transmission electron microscopy. The results show that the increased tensile strength (from 340 to 500 MPa) and elongation (from 3.6% to 4.2%) is due to the presence of lamellar O/B2 colony and needle-like O phase in B2 matrix in the as-processed Ti-22Al-25Nb alloys, as compared to the coarse lath O adjacent to B2 in the sintered alloys. Changes in morphologies of O phase improve the fracture toughness (KIC) of the sintered alloys from 7 to 15 MPa·m−1/2. Additionally, the fracture mechanism shifts from cleavage fracture in the as-sintered alloys to quasi-cleavage fracture in the as-processed alloys. Full article
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Open AccessFeature PaperArticle Spatial Frequency Responses of Anisotropic Refractive Index Gratings Formed in Holographic Polymer Dispersed Liquid Crystals
Materials 2016, 9(3), 188; https://doi.org/10.3390/ma9030188
Received: 31 January 2016 / Revised: 24 February 2016 / Accepted: 29 February 2016 / Published: 10 March 2016
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Abstract
We report on an experimental investigation of spatial frequency responses of anisotropic transmission refractive index gratings formed in holographic polymer dispersed liquid crystals (HPDLCs). We studied two different types of HPDLC materials employing two different monomer systems: one with acrylate monomer capable of
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We report on an experimental investigation of spatial frequency responses of anisotropic transmission refractive index gratings formed in holographic polymer dispersed liquid crystals (HPDLCs). We studied two different types of HPDLC materials employing two different monomer systems: one with acrylate monomer capable of radical mediated chain-growth polymerizations and the other with thiol-ene monomer capable of step-growth polymerizations. It was found that the photopolymerization kinetics of the two HPDLC materials could be well explained by the autocatalytic model. We also measured grating-spacing dependences of anisotropic refractive index gratings at a recording wavelength of 532 nm. It was found that the HPDLC material with the thiol-ene monomer gave higher spatial frequency responses than that with the acrylate monomer. Statistical thermodynamic simulation suggested that such a spatial frequency dependence was attributed primarily to a difference in the size of formed liquid crystal droplets due to different photopolymerization mechanisms. Full article
(This article belongs to the Special Issue Photopolymers for Holographic Applications)
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Open AccessArticle PEEK Primary Crowns with Cobalt-Chromium, Zirconia and Galvanic Secondary Crowns with Different Tapers—A Comparison of Retention Forces
Materials 2016, 9(3), 187; https://doi.org/10.3390/ma9030187
Received: 21 January 2016 / Revised: 23 February 2016 / Accepted: 8 March 2016 / Published: 10 March 2016
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Abstract
In prosthetic dentistry, double crown systems have proved their suitability as retainers for removable partial dentures. However, investigations in this context, regarding polyetheretherketone, are scarce. Therefore, the aim of this study was to test the retention force (RF) between polyetheretherketone (PEEK) primary and
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In prosthetic dentistry, double crown systems have proved their suitability as retainers for removable partial dentures. However, investigations in this context, regarding polyetheretherketone, are scarce. Therefore, the aim of this study was to test the retention force (RF) between polyetheretherketone (PEEK) primary and cobalt-chromium (CoCr), zirconia (ZrO2) and galvanic (GAL) secondary crowns with three different tapers. Primary PEEK-crowns were milled with the tapers 0°, 1°, and 2° (n = 10/taper, respectively). Afterwards, 90 secondary crowns were fabricated: (i) 30 CoCr-crowns milled from Ceramill Sintron (AmannGirrbach, Koblach, Austria) (n = 10/taper), (ii) 30 ZrO2-crowns milled from Ceramill ZI (AmannGirrbach, Koblach, Austria) (n = 10/taper), and (iii) 30 GAL-crowns made using electroforming (n = 10/taper). RF was measured in a pull-off test (20 pull-offs/specimen) and data were analyzed using 2-/1-way Analysis of Variance (ANOVA) followed by the Tukey-Honestly Significant Difference (HSD) post hoc test and linear regression analyses (p < 0.05). The measured mean RF values ranged between 9.6 and 38.2 N. With regard to the 0°, 1°, and 2° tapered crowns, no statistically significant differences between CoCr and ZrO2 were observed (p > 0.141). At 0° taper, no differences in retention forces between GAL, CrCr, and ZrO2 crowns were found (p = 0.075). However, at 1° and 2° taper, lower RF for GAL-crowns were observed (p < 0.009, p < 0.001, respectively). According to this laboratory study, PEEK might be a suitable material for primary crowns, regardless of the taper and the material of secondary crown. Long-term results, however, are still necessary. Full article
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Open AccessArticle Topological Design of Cellular Phononic Band Gap Crystals
Materials 2016, 9(3), 186; https://doi.org/10.3390/ma9030186
Received: 28 January 2016 / Revised: 2 March 2016 / Accepted: 3 March 2016 / Published: 10 March 2016
Cited by 17 | PDF Full-text (4051 KB) | HTML Full-text | XML Full-text
Abstract
This paper systematically investigated the topological design of cellular phononic crystals with a maximized gap size between two adjacent bands. Considering that the obtained structures may sustain a certain amount of static loadings, it is desirable to ensure the optimized designs to have
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This paper systematically investigated the topological design of cellular phononic crystals with a maximized gap size between two adjacent bands. Considering that the obtained structures may sustain a certain amount of static loadings, it is desirable to ensure the optimized designs to have a relatively high stiffness. To tackle this issue, we conducted a multiple objective optimization to maximize band gap size and bulk or shear modulus simultaneously with a prescribed volume fraction of solid material so that the resulting structures can be lightweight, as well. In particular, we first conducted the finite element analysis of the phononic band gap crystals and then adapted a very efficient optimization procedure to resolve this problem based on bi-directional evolutionary structure optimization (BESO) algorithm in conjunction with the homogenization method. A number of optimization results for maximizing band gaps with bulk and shear modulus constraints are presented for out-of-plane and in-plane modes. Numerical results showed that the optimized structures are similar to those obtained for composite case, except that additional slim connections are added in the cellular case to support the propagation of shear wave modes and meanwhile to satisfy the prescribed bulk or shear modulus constraints. Full article
(This article belongs to the Special Issue Cellular Materials: Design and Optimisation)
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Open AccessArticle Strength Development and Hydration Behavior of Self-Activation of Commercial Ground Granulated Blast-Furnace Slag Mixed with Purified Water
Materials 2016, 9(3), 185; https://doi.org/10.3390/ma9030185
Received: 14 January 2016 / Revised: 29 February 2016 / Accepted: 1 March 2016 / Published: 10 March 2016
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Abstract
In this study, ground granulated blast-furnace slag (GGBFS) samples from Singapore, Korea, and the United Arab Emirates were hydrated with purified water to estimate the cementing capabilities without activators. Raw GGBFS samples and hardened pastes were characterized to provide rational explanations for the
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In this study, ground granulated blast-furnace slag (GGBFS) samples from Singapore, Korea, and the United Arab Emirates were hydrated with purified water to estimate the cementing capabilities without activators. Raw GGBFS samples and hardened pastes were characterized to provide rational explanations for the strengths and hydration products. The slag characteristics that influenced the best strength of raw GGBFS were identified. Although it is widely recognized that GGBFS alone generally shows little cementing capability when hydrated with water, the GGBFSs examined in this study demonstrated various strength developments and hydration behaviors; one of the GGBFS samples even produced a high strength comparable to that of alkali- or Ca(OH)2-activated GGBFS. In particular, as the GGBFS exhibited a greater number of favorable slag characteristics for hydraulic reactivity, it produced more C-S-H and ettringite. The results demonstrated a reasonable potential for commercial GGBFS with calcium sulfates to function as an independent cementitious binder without activators. Full article
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