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Materials, Volume 7, Issue 1 (January 2014), Pages 1-622

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Open AccessArticle Accurate Measurement of Magnetic Resonance Imaging Gradient Characteristics
Materials 2014, 7(1), 1-15; doi:10.3390/ma7010001
Received: 3 November 2013 / Revised: 13 December 2013 / Accepted: 16 December 2013 / Published: 19 December 2013
Cited by 4 | PDF Full-text (384 KB) | HTML Full-text | XML Full-text
Abstract
Recently, gradient performance and fidelity has become of increasing interest, as the fidelity of the magnetic resonance (MR) image is somewhat dependent on the fidelity of the gradient system. In particular, for high fidelity non-Cartesian imaging, due to non-fidelity of the gradient system,
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Recently, gradient performance and fidelity has become of increasing interest, as the fidelity of the magnetic resonance (MR) image is somewhat dependent on the fidelity of the gradient system. In particular, for high fidelity non-Cartesian imaging, due to non-fidelity of the gradient system, it becomes necessary to know the actual k-space trajectory as opposed to the requested trajectory. In this work we show that, by considering the gradient system as a linear time-invariant system, the gradient impulse response function (GIRF) can be reliably measured to a relatively high degree of accuracy with a simple setup, using a small phantom and a series of simple experiments. It is shown experimentally that the resulting GIRF is able to predict actual gradient performance with a high degree of accuracy. The method captures not only the frequency response but also gradient timing errors and artifacts due to mechanical vibrations of the gradient system. Some discussion is provided comparing the method presented here with other analogous methods, along with limitations of these methods. Full article
(This article belongs to the Special Issue High Field Magnetic Resonance Methods and Materials)
Open AccessArticle Effect of Acid Hydrolysis Conditions on the Properties of Cellulose Nanoparticle-Reinforced Polymethylmethacrylate Composites
Materials 2014, 7(1), 16-29; doi:10.3390/ma7010016
Received: 3 October 2013 / Revised: 28 November 2013 / Accepted: 16 December 2013 / Published: 20 December 2013
Cited by 9 | PDF Full-text (1073 KB) | HTML Full-text | XML Full-text
Abstract
Cellulose nanoparticles (CNPs) were prepared from microcrystalline cellulose using two concentration levels of sulfuric acid (i.e., 48 wt% and 64 wt% with produced CNPs designated as CNPs-48 and CNPs-64, respectively) followed by high-pressure homogenization. CNP-reinforced polymethylmethacrylate (PMMA) composite films at various
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Cellulose nanoparticles (CNPs) were prepared from microcrystalline cellulose using two concentration levels of sulfuric acid (i.e., 48 wt% and 64 wt% with produced CNPs designated as CNPs-48 and CNPs-64, respectively) followed by high-pressure homogenization. CNP-reinforced polymethylmethacrylate (PMMA) composite films at various CNP loadings were made using solvent exchange and solution casting methods. The ultraviolet-visible (UV-vis) transmittance spectra between 400 and 800 nm showed that CNPs-64/PMMA composites had a significantly higher optical transmittance than that of CNPs-48/PMMA. Their transmittance decreased with increased CNP loadings. The addition of CNPs to the PMMA matrix reduced composite’s coefficient of thermal expansion (CTE), and CNPs-64/PMMA had a lower CTE than CNPs-48/PMMA at the same CNP level. Reinforcement effect was achieved with the addition of CNPs to the PMMA matrix, especially at higher temperature levels. CNPs-64/PMMA exhibited a higher storage modulus compared with CNPs-48/PMMA material. All CNP-reinforced composites showed higher Young’s modulus and tensile strengths than pure PMMA. The effect increased with increased CNP loadings in the PMMA matrix for both CNPs-64/PMMA and CNPs-48/PMMA composites. CNPs affected the Young’s modulus more than they affected the tensile strength. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle Gain of Imaging Fidelity by Employing a Higher Number of Independent Transmit Channels Together with Slice-Selective Radio-Frequency (RF) Shimming at 7T
Materials 2014, 7(1), 30-43; doi:10.3390/ma7010030
Received: 24 September 2013 / Revised: 29 November 2013 / Accepted: 16 December 2013 / Published: 20 December 2013
PDF Full-text (640 KB) | HTML Full-text | XML Full-text
Abstract
Dielectric resonance effects and radio-frequency (RF) power deposition have become challenging issues for magnetic resonance imaging at ultrahigh-field (UHF) strengths. The use of transmit (Tx) coil arrays with independently-driven RF sources using a parallel transmission system is a promising method for alleviating the
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Dielectric resonance effects and radio-frequency (RF) power deposition have become challenging issues for magnetic resonance imaging at ultrahigh-field (UHF) strengths. The use of transmit (Tx) coil arrays with independently-driven RF sources using a parallel transmission system is a promising method for alleviating the resulting RF inhomogeneities. In this study, the effect on homogeneity and RF-power when employing a higher number of transmit channels with multi-slice acquisition in vivo at high field strength (7T) is scrutinized. An 8-channel head coil array was driven to emulate circular polarized (CP) and 2-, 4-, and 8-channel independent transmit configurations at 7T. Static RF shimming was employed on human subjects in order to homogenize the B1+ field in the excited volume. Slice-selective and global RF shimming methods were applied with CP and 2-, 4-, and 8-channel transmit channel configurations. RF shimming was performed from CP to 2-, 4-, and 8-channel Tx configurations globally and slice-selectively. Systematic improvement in B1+ homogeneity and/or reduction in RF-power were observed. RF shimming in the human brain with 8-channel transmit and slice-selective shimming yields an increase in B1+ homogeneity of 43% and/or reduces RF-power by 68% when compared with CP global RF shimming at 7T. Full article
(This article belongs to the Special Issue High Field Magnetic Resonance Methods and Materials 2013)
Open AccessCommunication Optical Fiber Embedded in Epoxy Glass Unidirectional Fiber Composite System
Materials 2014, 7(1), 44-57; doi:10.3390/ma7010044
Received: 16 September 2013 / Revised: 24 November 2013 / Accepted: 17 December 2013 / Published: 20 December 2013
PDF Full-text (1162 KB) | HTML Full-text | XML Full-text
Abstract
We aimed to embed silica optical fibers in composites (epoxy vinyl ester matrix reinforced with E-glass unidirectional fibers in mass fraction of 60%) in order to further monitor the robustness of civil engineering structures (such as bridges). A simple system was implemented using
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We aimed to embed silica optical fibers in composites (epoxy vinyl ester matrix reinforced with E-glass unidirectional fibers in mass fraction of 60%) in order to further monitor the robustness of civil engineering structures (such as bridges). A simple system was implemented using two different silica optical fibers (F1—double coating of 172 µm diameter and F2—single coating of 101.8 µm diameter respectively). The optical fibers were dynamically tensile tested and Weibull plots were traced. Interfacial adhesion stress was determined using pull-out test and stress values were correlated to fracture mechanisms based on SEM observations. In the case of the optical fiber (OF) (F1)/resin system and OF (F1)/composite system, poor adhesion was reported that may be correlated to interface fracture at silica core level. Relevant applicable results were determined for OF (F2)/composite system. Full article
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Open AccessArticle Effect of Stretching on Ultraviolet Protection of Cotton and Cotton/Coolmax Blended Weft Knitted Fabric in a Wet State
Materials 2014, 7(1), 58-74; doi:10.3390/ma7010058
Received: 1 November 2013 / Revised: 9 December 2013 / Accepted: 12 December 2013 / Published: 20 December 2013
Cited by 4 | PDF Full-text (817 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the ultraviolet protection factor (UPF) of plain knitted fabrics made from 20Ne cotton yarns, Coolmax yarn and their combinations in wet, relaxed and stretched states were studied. According to the fiber composition, fabric samples are divided into three groups including
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In this paper, the ultraviolet protection factor (UPF) of plain knitted fabrics made from 20Ne cotton yarns, Coolmax yarn and their combinations in wet, relaxed and stretched states were studied. According to the fiber composition, fabric samples are divided into three groups including Group I (single cotton yarn), Group II (cotton/cotton combination) and Group III (Coolmax/cotton combination) for discussion. In order to study the effect of wet condition on the UPF of different plain knitted fabrics, five wetting solutions, namely: (i) chlorinated pool water; (ii) sea water, (iii) acidic perspiration; (iv) alkaline perspiration and (v) deionized water (DI water) were prepared and the fabrics were wetted with different percentages of 50%, 75% and 100%. The UPF of the plain knitted fabrics in wet, relaxed and stretched states was measured and the results were discussed. In addition, yarn and fabric properties such as yarn tenacity, yarn strength, fiber combination and water vapor transmission, which affect the corresponding UPF values, were used for generating a prediction model in order to determine UPF. Verification of the prediction model was also conducted. Full article
Open AccessArticle Mechanical, Microstructure and Surface Characterizations of Carbon Fibers Prepared from Cellulose after Liquefying and Curing
Materials 2014, 7(1), 75-84; doi:10.3390/ma7010075
Received: 11 November 2013 / Revised: 5 December 2013 / Accepted: 13 December 2013 / Published: 20 December 2013
Cited by 9 | PDF Full-text (582 KB) | HTML Full-text | XML Full-text
Abstract
In this study, Cellulose-based carbon fibers (CBCFs) were prepared from cellulose after phenol liquefaction and curing. The characteristics and properties of CBCFs were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy
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In this study, Cellulose-based carbon fibers (CBCFs) were prepared from cellulose after phenol liquefaction and curing. The characteristics and properties of CBCFs were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that, with increasing carbonization temperature, the La, Lc, and Lc/d(002) of CBCFs increased gradually, whereas the degree of disorder R decreased. The –OH, –CH2–, –O–C– and phenyl group characteristic absorption peaks of CBCFs reduced gradually. The cross-linked structure of CBCFs was converted into a graphite structure with a six-ring carbon network during carbonization. The surface of CBCFs were mainly comprised of C–C, C–O, and C=O. The tensile strength, carbonization yield and carbon content of CBCFs obtained at 1000 °C were 1015 MPa, 52%, and 95.04%, respectively. Full article
(This article belongs to the Special Issue Carbon Fibers) Print Edition available
Open AccessArticle Cytotoxicity Test of One-Step Self-Etching Bonding Agents by Standardized Dentin Barrier Test Using Polyurethane Discs
Materials 2014, 7(1), 85-96; doi:10.3390/ma7010085
Received: 5 November 2013 / Revised: 5 December 2013 / Accepted: 18 December 2013 / Published: 23 December 2013
Cited by 1 | PDF Full-text (778 KB) | HTML Full-text | XML Full-text
Abstract
This study was performed to standardize a dentin barrier test with the substitute and evaluate the cytotoxicity of one-step self-etching bonding agents. Each of the natural bovine dentin and polyurethane discs were 500-μm thick and were tested using a perfusion device. Following the
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This study was performed to standardize a dentin barrier test with the substitute and evaluate the cytotoxicity of one-step self-etching bonding agents. Each of the natural bovine dentin and polyurethane discs were 500-μm thick and were tested using a perfusion device. Following the treatment with 0.05% phenol on the natural bovine disc or three kinds of polyurethane discs—30, 40, and 50 pcf (pounds per cubic foot)—cell viability of L-929 was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and expressed as percentages of non-treated group, respectively. A substitute showing permeability similar to that of bovine dentin was determined based on this result. Cytotoxicity test of bonding agents was performed by the selected substitute, the results of which were expressed as percentages of the control. In addition, SEM images were taken after the tests. The cell viability by 40-pcf polyurethane disc was not statistically different from that by bovine dentin disc (P > 0.05). Futurabond DC resulted in the highest cell viability and Bond force the lowest by the 40-pcf polyurethane disc (P < 0.05). The adhesives on the 40-pcf polyurethane disc changed cellular morphology with different degrees on the SEM images. This standardized test might be useful for assessing the cytotoxicity of dental materials applied to dentin before clinical applications. Full article
(This article belongs to the Special Issue Biocompatibility of Materials 2013)
Open AccessArticle Controlled Synthesis of Carbon Nanoparticles in a Supercritical Carbon Disulfide System
Materials 2014, 7(1), 97-105; doi:10.3390/ma7010097
Received: 25 November 2013 / Revised: 13 December 2013 / Accepted: 23 December 2013 / Published: 27 December 2013
Cited by 6 | PDF Full-text (316 KB) | HTML Full-text | XML Full-text
Abstract
Carbon nanoparticles with large surface areas were produced by the reduction of carbon disulfide with metallic lithium at 500 °C. The carbon nanoparticles account for about 80% of the carbon product. The carbon nanoparticles were characterized by X-ray powder diffraction, field emission scanning
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Carbon nanoparticles with large surface areas were produced by the reduction of carbon disulfide with metallic lithium at 500 °C. The carbon nanoparticles account for about 80% of the carbon product. The carbon nanoparticles were characterized by X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and N2 physisorption. The results showed that carbon nanoparticles predominate in the product. The influence of experimental conditions was investigated, which indicated that temperature plays a crucial role in the formation of carbon nanoparticles. The possible formation mechanism of the carbon nanoparticles was discussed. This method provides a simple and efficient route to the synthesis of carbon nanoparticles. Full article
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Open AccessArticle Room Temperature Ferromagnetic Mn:Ge(001)
Materials 2014, 7(1), 106-129; doi:10.3390/ma7010106
Received: 27 September 2013 / Revised: 16 December 2013 / Accepted: 16 December 2013 / Published: 27 December 2013
Cited by 2 | PDF Full-text (1272 KB) | HTML Full-text | XML Full-text
Abstract
We report the synthesis of a room temperature ferromagnetic Mn-Ge system obtained by simple deposition of manganese on Ge(001), heated at relatively high temperature (starting with 250 °C). The samples were characterized by low energy electron diffraction (LEED), scanning tunneling microscopy (STM), high
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We report the synthesis of a room temperature ferromagnetic Mn-Ge system obtained by simple deposition of manganese on Ge(001), heated at relatively high temperature (starting with 250 °C). The samples were characterized by low energy electron diffraction (LEED), scanning tunneling microscopy (STM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), superconducting quantum interference device (SQUID), and magneto-optical Kerr effect (MOKE). Samples deposited at relatively elevated temperature (350 °C) exhibited the formation of ~5–8 nm diameter Mn5Ge3 and Mn11Ge8 agglomerates by HRTEM, while XPS identified at least two Mn-containing phases: the agglomerates, together with a Ge-rich MnGe~2.5 phase, or manganese diluted into the Ge(001) crystal. LEED revealed the persistence of long range order after a relatively high amount of Mn (100 nm) deposited on the single crystal substrate. STM probed the existence of dimer rows on the surface, slightly elongated as compared with Ge–Ge dimers on Ge(001). The films exhibited a clear ferromagnetism at room temperature, opening the possibility of forming a magnetic phase behind a nearly ideally terminated Ge surface, which could find applications in integration of magnetic functionalities on semiconductor bases. SQUID probed the co-existence of a superparamagnetic phase, with one phase which may be attributed to a diluted magnetic semiconductor. The hypothesis that the room temperature ferromagnetic phase might be the one with manganese diluted into the Ge crystal is formulated and discussed. Full article
(This article belongs to the Special Issue Spintronics)
Open AccessArticle In situ Surface Tailoring with Zwitterionic Carboxybetaine Moieties on Self-Assembled Thin Film for Antifouling Biointerfaces
Materials 2014, 7(1), 130-142; doi:10.3390/ma7010130
Received: 16 September 2013 / Revised: 12 November 2013 / Accepted: 20 December 2013 / Published: 27 December 2013
Cited by 6 | PDF Full-text (743 KB) | HTML Full-text | XML Full-text
Abstract
A novel biointerface bearing zwitterionic carboxybetaine moieties was developed for effective resistance to nonspecific adsorption of proteins and blood cells. Self-assembled thin films (SAFs) of (N,N-dimethylaminopropyl) trimethoxysilane were formed as mattress layers by either vapor or solution deposition. Subsequently,
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A novel biointerface bearing zwitterionic carboxybetaine moieties was developed for effective resistance to nonspecific adsorption of proteins and blood cells. Self-assembled thin films (SAFs) of (N,N-dimethylaminopropyl) trimethoxysilane were formed as mattress layers by either vapor or solution deposition. Subsequently, the tertiary amine head groups on SAFs were reacted with β-propiolactone to give zwitterionic carboxybetaine moieties via in situ synthesis. The optimal reaction time of 8 h for both preparation methods was verified by static contact angle measurements. According to the X-ray photoelectron spectroscopy, 67.3% of amine groups on SAFs prepared from the vapor deposition was converted to the zwitterionic structures after reaction of β-propiolactone. The antifouling properties of the zwitterionic biointerfaces were quantitatively evaluated in the presence of protein solutions using a quartz crystal microbalance with dissipation, showing a great improvement by factors of 6.5 and 20.2 from tertiary amine SAFs and bare SiO2 surfaces, respectively. More importantly, the zwitterionic SAFs were brought to contact with undiluted human blood in chaotic-mixer microfluidic systems; the results present their capability to effectively repel blood cell adhesion. Accordingly, in this work, development of carboxybetaine SAFs offers a facile yet effective strategy to fabricate biocompatible biointerfaces for a variety of potential applications in surface coatings for medical devices. Full article
(This article belongs to the Special Issue Biocompatibility of Materials 2013)
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Open AccessArticle Effects of Ground Conditions on Microbial Cementation in Soils
Materials 2014, 7(1), 143-156; doi:10.3390/ma7010143
Received: 25 September 2013 / Revised: 6 December 2013 / Accepted: 23 December 2013 / Published: 27 December 2013
Cited by 5 | PDF Full-text (1200 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this study is to understand the effect of ground conditions on microbial cementation in cohesionless soils. Since the method of microbial cementation is still at the experimental stage, for its practical use in the field, a number of laboratory experiments
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The purpose of this study is to understand the effect of ground conditions on microbial cementation in cohesionless soils. Since the method of microbial cementation is still at the experimental stage, for its practical use in the field, a number of laboratory experiments are required for the quantification of microbial cementation under various ground conditions, such as relative densities, relative compactions and particle size distributions. In this study, in order to evaluate the effectiveness of microbial cementation in treated sands and silts, an experiment was performed for different relative densities of silica sands, for different relative compactions of silts and for different particle size distributions of weathered soils sampled from the field. Scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy and mapping analyses were implemented for the quantification of the levels of microbial cementations for sand, silt and weathered soil specimens. Based on the test results, a considerable microbial cementation was estimated depending on the soil conditions; therefore, an implementation of this new type of bio-grouting on a weak foundation may be possible to increase the strength and stiffness of weak ground. Full article
(This article belongs to the Special Issue Construction Materials)
Open AccessArticle Lu2O3:Pr,Hf Storage Phosphor: Compositional and Technological Issues
Materials 2014, 7(1), 157-169; doi:10.3390/ma7010157
Received: 3 November 2013 / Revised: 9 December 2013 / Accepted: 11 December 2013 / Published: 31 December 2013
Cited by 4 | PDF Full-text (998 KB) | HTML Full-text | XML Full-text
Abstract
Lu2O3:Pr,Hf ceramics were investigated using mainly thermoluminescence (TL) technique. Their ability to efficiently store energy acquired upon irradiation with X-rays was proven. The best TL performance was achieved for compositions containing 0.025%–0.05% of Pr and about 0.1% of Hf.
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Lu2O3:Pr,Hf ceramics were investigated using mainly thermoluminescence (TL) technique. Their ability to efficiently store energy acquired upon irradiation with X-rays was proven. The best TL performance was achieved for compositions containing 0.025%–0.05% of Pr and about 0.1% of Hf. Further enhancement of TL efficiency was attained by increasing the temperature of sintering of the ceramics up to 1700 °C and applying reducing atmosphere of forming gas. It was also proven that fast cooling after the sintering at 1700 °C significantly enhanced the storage phosphor performance. TL glow curve contained three components peaking around 130, 250 and 350 °C. Among them, the one at 250 °C contributed the most to the total TL. Full article
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Open AccessArticle Fluorescence Sensing of the Interaction between Biomembranes with Different Lipid Composition and Endocrine Disrupting Chemicals
Materials 2014, 7(1), 170-179; doi:10.3390/ma7010170
Received: 28 November 2013 / Revised: 9 December 2013 / Accepted: 21 December 2013 / Published: 31 December 2013
PDF Full-text (314 KB) | HTML Full-text | XML Full-text
Abstract
Fluorescence sensing of the interaction between biomembranes with different lipid composition and endocrine disrupting chemicals (EDCs) was carried out by using a liposome-encapsulating fluorescence dye (carboxyfluorescein (CF)-liposome). We detected a significant increase in fluorescence intensity in CF-liposome solutions due to the leakage of
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Fluorescence sensing of the interaction between biomembranes with different lipid composition and endocrine disrupting chemicals (EDCs) was carried out by using a liposome-encapsulating fluorescence dye (carboxyfluorescein (CF)-liposome). We detected a significant increase in fluorescence intensity in CF-liposome solutions due to the leakage of fluorescence caused by the interaction of EDCs with the biomembranes of liposomes. The temporal increases in fluorescent were significantly different among the lipid compositions of CF-liposome and the EDCs. Results were considered by summarizing the interactions in radar charts and by showing the pattern of interaction of each EDC. Each chart showed a dissimilar pattern reflecting the complexity of the biomembrane-EDC interaction. The results indicate that this fluorescence sensing could be useful to evaluate the interaction. Full article
(This article belongs to the Special Issue Functional Materials and Proteins for Bio-Sensing Applications)
Open AccessArticle Improvement to the Corrosion Resistance of Ti-Based Implants Using Hydrothermally Synthesized Nanostructured Anatase Coatings
Materials 2014, 7(1), 180-194; doi:10.3390/ma7010180
Received: 4 November 2013 / Revised: 9 December 2013 / Accepted: 20 December 2013 / Published: 2 January 2014
Cited by 10 | PDF Full-text (934 KB) | HTML Full-text | XML Full-text
Abstract
The electrochemical behavior of polycrystalline TiO2 anatase coatings prepared by a one-step hydrothermal synthesis on commercially pure (CP) Ti grade 2 and a Ti13Nb13Zr alloy for bone implants was investigated in Hank’s solution at 37.5 °C. The aim was to verify to
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The electrochemical behavior of polycrystalline TiO2 anatase coatings prepared by a one-step hydrothermal synthesis on commercially pure (CP) Ti grade 2 and a Ti13Nb13Zr alloy for bone implants was investigated in Hank’s solution at 37.5 °C. The aim was to verify to what extent the in-situ-grown anatase improved the behavior of the substrate in comparison to the bare substrates. Tafel-plot extrapolations from the potentiodynamic curves revealed a substantial improvement in the corrosion potentials for the anatase coatings. Moreover, the coatings grown on titanium also exhibited lower corrosion-current densities, indicating a longer survival of the implant. The results were explained by considering the effects of crystal morphology, coating thickness and porosity. Evidence for the existing porosity was obtained from corrosion and nano-indentation tests. The overall results indicated that the hydrothermally prepared anatase coatings, with the appropriate morphology and surface properties, have attractive prospects for use in medical devices, since better corrosion protection of the implant can be expected. Full article
(This article belongs to the Special Issue Titanium Materials for Biomedical Application 2013)
Open AccessArticle Preparation of Fe3O4-Embedded Poly(styrene)/Poly(thiophene) Core/Shell Nanoparticles and Their Hydrogel Patterns for Sensor Applications
Materials 2014, 7(1), 195-205; doi:10.3390/ma7010195
Received: 30 November 2013 / Revised: 26 December 2013 / Accepted: 27 December 2013 / Published: 2 January 2014
Cited by 3 | PDF Full-text (611 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This research describes the preparation and sensor applications of multifunctional monodisperse, Fe3O4 nanoparticles-embedded poly(styrene)/poly(thiophene) (Fe3O4-PSt/PTh), core/shell nanoparticles. Monodisperse Fe3O4-PSt/PTh nanoparticles were prepared by free-radical combination (mini-emulsion/emulsion) polymerization for Fe3O4
[...] Read more.
This research describes the preparation and sensor applications of multifunctional monodisperse, Fe3O4 nanoparticles-embedded poly(styrene)/poly(thiophene) (Fe3O4-PSt/PTh), core/shell nanoparticles. Monodisperse Fe3O4-PSt/PTh nanoparticles were prepared by free-radical combination (mini-emulsion/emulsion) polymerization for Fe3O4-PSt core and oxidative seeded emulsion polymerization for PTh shell in the presence of FeCl3/H2O2 as a redox catalyst, respectively. For applicability of Fe3O4-PSt/PTh as sensors, Fe3O4-PSt/PTh-immobilized poly(ethylene glycol) (PEG)-based hydrogels were fabricated by photolithography. The hydrogel patterns showed a good sensing performance under different H2O2 concentrations. They also showed a quenching sensitivity of 1 µg/mL for the Pd2+ metal ion within 1 min. The hydrogel micropatterns not only provide a fast water uptake property but also suggest the feasibility of both H2O2 and Pd2+ detection. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
Open AccessArticle Fabrication of CIS Absorber Layers with Different Thicknesses Using A Non-Vacuum Spray Coating Method
Materials 2014, 7(1), 206-217; doi:10.3390/ma7010206
Received: 8 October 2013 / Revised: 14 December 2013 / Accepted: 19 December 2013 / Published: 3 January 2014
Cited by 3 | PDF Full-text (1180 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a new thin-film deposition process, spray coating method (SPM), was investigated to deposit the high-densified CuInSe2 absorber layers. The spray coating method developed in this study was a non-vacuum process, based on dispersed nano-scale CuInSe2 precursor and could
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In this study, a new thin-film deposition process, spray coating method (SPM), was investigated to deposit the high-densified CuInSe2 absorber layers. The spray coating method developed in this study was a non-vacuum process, based on dispersed nano-scale CuInSe2 precursor and could offer a simple, inexpensive, and alternative formation technology for CuInSe2 absorber layers. After spraying on Mo/glass substrates, the CuInSe2 thin films were annealed at 550 °C by changing the annealing time from 5 min to 30 min in a selenization furnace, using N2 as atmosphere. When the CuInSe2 thin films were annealed, without extra Se or H2Se gas used as the compensation source during the annealing process. The aim of this project was to investigate the influence of annealing time on the densification and crystallization of the CuInSe2 absorber layers to optimize the quality for cost effective solar cell production. The thickness of the CuInSe2 absorber layers could be controlled as the volume of used dispersed CuInSe2-isopropyl alcohol solution was controlled. In this work, X-ray diffraction patterns, field emission scanning electron microscopy, and Hall parameter measurements were performed in order to verify the quality of the CuInSe2 absorber layers obtained by the Spray Coating Method. Full article
(This article belongs to the Special Issue Solar Energy Materials 2013)
Open AccessArticle Study on the Carbonation Behavior of Cement Mortar by Electrochemical Impedance Spectroscopy
Materials 2014, 7(1), 218-231; doi:10.3390/ma7010218
Received: 28 November 2013 / Revised: 17 December 2013 / Accepted: 23 December 2013 / Published: 3 January 2014
Cited by 5 | PDF Full-text (636 KB) | HTML Full-text | XML Full-text
Abstract
A new electrochemical model has been carefully established to explain the carbonation behavior of cement mortar, and the model has been validated by the experimental results. In fact, it is shown by this study that the electrochemical impedance behavior of mortars varies in
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A new electrochemical model has been carefully established to explain the carbonation behavior of cement mortar, and the model has been validated by the experimental results. In fact, it is shown by this study that the electrochemical impedance behavior of mortars varies in the process of carbonation. With the cement/sand ratio reduced, the carbonation rate reveals more remarkable. The carbonation process can be quantitatively accessed by a parameter, which can be obtained by means of the electrochemical impedance spectroscopy (EIS)-based electrochemical model. It has been found that the parameter is a function of carbonation depth and of carbonation time. Thereby, prediction of carbonation depth can be achieved. Full article
(This article belongs to the Special Issue Construction Materials)
Open AccessArticle Influence of Oxygen Content and Microstructure on the Mechanical Properties and Biocompatibility of Ti–15 wt%Mo Alloy Used for Biomedical Applications
Materials 2014, 7(1), 232-243; doi:10.3390/ma7010232
Received: 5 November 2013 / Revised: 20 November 2013 / Accepted: 26 December 2013 / Published: 6 January 2014
PDF Full-text (525 KB) | HTML Full-text | XML Full-text
Abstract
The Ti–15Mo alloy has its mechanical properties strongly altered by heat treatments and by addition of interstitial elements, such as, oxygen, for example. In this sense, the objective of this paper is to analyze the effect of the introduction of oxygen in selected
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The Ti–15Mo alloy has its mechanical properties strongly altered by heat treatments and by addition of interstitial elements, such as, oxygen, for example. In this sense, the objective of this paper is to analyze the effect of the introduction of oxygen in selected mechanical properties and the biocompatibility of Ti–15Mo alloy. The samples used in this study were prepared by arc-melting and characterized by density measurements, X-ray diffraction, scanning electron microscopy, microhardness, modulus of elasticity, and biocompatibility tests. Hardness measurements were shown to be sensitive to concentration of oxygen. The modulus results showed interstitial influence in value; this was verified under several conditions to which the samples were exposed. Cytotoxicity tests conducted in vitro showed that the various processing conditions did not alter the biocompatibility of the material. Full article
(This article belongs to the Special Issue Titanium Materials for Biomedical Application 2013)
Open AccessArticle Microstructural Evolution and Dynamic Softening Mechanisms of Al-Zn-Mg-Cu Alloy during Hot Compressive Deformation
Materials 2014, 7(1), 244-264; doi:10.3390/ma7010244
Received: 7 November 2013 / Revised: 20 December 2013 / Accepted: 2 January 2014 / Published: 8 January 2014
Cited by 15 | PDF Full-text (1957 KB) | HTML Full-text | XML Full-text
Abstract
The hot deformation behavior and microstructural evolution of an Al-Zn-Mg-Cu (7150) alloy was studied during hot compression at various temperatures (300 to 450 °C) and strain rates (0.001 to 10 s−1). A decline ratio map of flow stresses was proposed and
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The hot deformation behavior and microstructural evolution of an Al-Zn-Mg-Cu (7150) alloy was studied during hot compression at various temperatures (300 to 450 °C) and strain rates (0.001 to 10 s−1). A decline ratio map of flow stresses was proposed and divided into five deformation domains, in which the flow stress behavior was correlated with different microstructures and dynamic softening mechanisms. The results reveal that the dynamic recovery is the sole softening mechanism at temperatures of 300 to 400 °C with various strain rates and at temperatures of 400 to 450 °C with strain rates between 1 and 10 s−1. The level of dynamic recovery increases with increasing temperature and with decreasing strain rate. At the high deformation temperature of 450 °C with strain rates of 0.001 to 0.1 s−1, a partially recrystallized microstructure was observed, and the dynamic recrystallization (DRX) provided an alternative softening mechanism. Two kinds of DRX might operate at the high temperature, in which discontinuous dynamic recrystallization was involved at higher strain rates and continuous dynamic recrystallization was implied at lower strain rates. Full article
(This article belongs to the Special Issue Light Alloys and Their Applications)
Open AccessArticle Electrodeposition of Manganese-Nickel Oxide Films on a Graphite Sheet for Electrochemical Capacitor Applications
Materials 2014, 7(1), 265-274; doi:10.3390/ma7010265
Received: 15 November 2013 / Revised: 26 December 2013 / Accepted: 30 December 2013 / Published: 9 January 2014
Cited by 12 | PDF Full-text (673 KB) | HTML Full-text | XML Full-text
Abstract
Manganese-nickel (Mn-Ni) oxide films were electrodeposited on a graphite sheet in a bath consisting of manganese acetate and nickel chloride, and the structural, morphological, and electrochemical properties of these films were investigated. The electrodeposited Mn-Ni oxide films had porous structures covered with nanofibers.
[...] Read more.
Manganese-nickel (Mn-Ni) oxide films were electrodeposited on a graphite sheet in a bath consisting of manganese acetate and nickel chloride, and the structural, morphological, and electrochemical properties of these films were investigated. The electrodeposited Mn-Ni oxide films had porous structures covered with nanofibers. The X-ray diffractometer pattern revealed the presence of separate manganese oxide (g-MnO2) and nickel oxide (NiO) in the films. The electrodeposited Mn-Ni oxide electrode exhibited a specific capacitance of 424 F/g in Na2SO4 electrolyte. This electrode maintained 86% of its initial specific capacitance over 2000 cycles of the charge-discharge operation, showing good cycling stability. Full article
(This article belongs to the Section Materials for Energy Applications)
Open AccessArticle Alginate-Poly(ethylene glycol) Hybrid Microspheres for Primary Cell Microencapsulation
Materials 2014, 7(1), 275-286; doi:10.3390/ma7010275
Received: 11 November 2013 / Revised: 17 December 2013 / Accepted: 2 January 2014 / Published: 9 January 2014
Cited by 8 | PDF Full-text (706 KB) | HTML Full-text | XML Full-text
Abstract
The progress of medical therapies, which rely on the transplantation of microencapsulated living cells, depends on the quality of the encapsulating material. Such material has to be biocompatible, and the microencapsulation process must be simple and not harm the cells. Alginate-poly(ethylene glycol) hybrid
[...] Read more.
The progress of medical therapies, which rely on the transplantation of microencapsulated living cells, depends on the quality of the encapsulating material. Such material has to be biocompatible, and the microencapsulation process must be simple and not harm the cells. Alginate-poly(ethylene glycol) hybrid microspheres (alg-PEG-M) were produced by combining ionotropic gelation of sodium alginate (Na-alg) using calcium ions with covalent crosslinking of vinyl sulfone-terminated multi-arm poly(ethylene glycol) (PEG-VS). In a one-step microsphere formation process, fast ionotropic gelation yields spherical calcium alginate gel beads, which serve as a matrix for simultaneously but slowly occurring covalent cross-linking of the PEG-VS molecules. The feasibility of cell microencapsulation was studied using primary human foreskin fibroblasts (EDX cells) as a model. The use of cell culture media as polymer solvent, gelation bath, and storage medium did not negatively affect the alg-PEG-M properties. Microencapsulated EDX cells maintained their viability and proliferated. This study demonstrates the feasibility of primary cell microencapsulation within the novel microsphere type alg-PEG-M, serves as reference for future therapy development, and confirms the suitability of EDX cells as control model. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Self-Assembled M2L4 Nanocapsules: Synthesis, Structure and Host-Guest Recognition Toward Square Planar Metal Complexes
Materials 2014, 7(1), 287-301; doi:10.3390/ma7010287
Received: 1 October 2013 / Revised: 28 November 2013 / Accepted: 17 December 2013 / Published: 9 January 2014
Cited by 12 | PDF Full-text (950 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Metallosupramolecular cages of the general formulas [M2(L)4][X]4 can be self-assembled in good yields, where M = Pd, X = NO3,L = L1 (1a); M = Pd, X = OTf, L = L
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Metallosupramolecular cages of the general formulas [M2(L)4][X]4 can be self-assembled in good yields, where M = Pd, X = NO3, L = L1 (1a); M = Pd, X = OTf, L = L1 (1b); M = Pt, X = OTf, L = L1 (2); M = Pd, X = OTf, L = L2 (3); L1 = 1,3-bis(pyridin-3-ylethynyl)-5-methoxybenzene; and L2 = 2,6-(pyridin-3-ylethynyl)- 4-methoxyaniline, respectively. These cages have been fully characterized using 1H, 13C NMR, elemental analysis, IR spectroscopy, and electrospray mass spectrometry. Additionally the molecular structure of [Pd2(L1)4][OTf]4 (1b) was confirmed using single crystal X-ray diffraction. The capacity of central cavities of M2L4 cages to accommodate square planar metal complexes was investigated. In particular, the tetracationic cage [Pd2(L2)4][OTf]4 (3) was found to encapsulate the anionic metal complex [PtCl4]2− through electrostatic interactions and also via hydrogen bonding with the amino groups of the bridging ligand displayed by this nanocage. Full article
(This article belongs to the Special Issue Supramolecular Cage Complexes)
Open AccessArticle The Influence of Grain Interactions on the Plastic Stability of Heterophase Interfaces
Materials 2014, 7(1), 302-322; doi:10.3390/ma7010302
Received: 1 November 2013 / Revised: 13 December 2013 / Accepted: 17 December 2013 / Published: 13 January 2014
Cited by 10 | PDF Full-text (2266 KB) | HTML Full-text | XML Full-text
Abstract
Two-phase bimetal composites contain both grain boundaries and bi-phase interfaces between dissimilar crystals. In this work, we use a crystal plasticity finite element framework to explore the effects of grain boundary interactions on the plastic stability of bi-phase interfaces. We show that neighboring
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Two-phase bimetal composites contain both grain boundaries and bi-phase interfaces between dissimilar crystals. In this work, we use a crystal plasticity finite element framework to explore the effects of grain boundary interactions on the plastic stability of bi-phase interfaces. We show that neighboring grain interactions do not significantly alter interface plastic stability during plane strain compression. The important implications are that stable orientations at bimetal interfaces can be different than those within the bulk layers. This finding provides insight into bi-phase microstructural development and suggests a pathway for tuning interface properties via severe plastic deformation. Full article
(This article belongs to the Special Issue Computational Modeling and Simulation in Materials Study)
Open AccessCommunication Thermo-Plasmonics for Localized Graphitization and Welding of Polymeric Nanofibers
Materials 2014, 7(1), 323-332; doi:10.3390/ma7010323
Received: 29 November 2013 / Revised: 25 December 2013 / Accepted: 7 January 2014 / Published: 13 January 2014
Cited by 1 | PDF Full-text (433 KB) | HTML Full-text | XML Full-text
Abstract
There is a growing interest in modulating the temperature under the illumination of light. As a heat source, metal nanoparticles (NPs) have played an important role to pave the way for a new branch of plasmonics, i.e., thermo-plasmonics. While thermo-plasmonics have been
[...] Read more.
There is a growing interest in modulating the temperature under the illumination of light. As a heat source, metal nanoparticles (NPs) have played an important role to pave the way for a new branch of plasmonics, i.e., thermo-plasmonics. While thermo-plasmonics have been well established in photo-thermal therapy, it has received comparatively less attention in materials science and chemistry. Here, we demonstrate the first proof of concept experiment of local chemistry and graphitization of metalized polymeric nanofibers through thermo-plasmonic effect. In particular, by tuning the plasmonic absorption of the nanohybrid through a change in the thickness of the deposited silver film on the fibers, the thermo-plasmonic effect can be adjusted in such a way that high enough temperature is generated enabling local welding and graphitization of the polymeric nanofibers. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
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Open AccessArticle Rapid Growth of Nanostructured Diamond Film on Silicon and Ti–6Al–4V Alloy Substrates
Materials 2014, 7(1), 365-374; doi:10.3390/ma7010365
Received: 18 October 2013 / Revised: 25 November 2013 / Accepted: 2 January 2014 / Published: 13 January 2014
Cited by 4 | PDF Full-text (578 KB) | HTML Full-text | XML Full-text
Abstract
Nanostructured diamond (NSD) films were grown on silicon and Ti–6Al–4V alloy substrates by microwave plasma chemical vapor deposition (MPCVD). NSD Growth rates of 5 µm/h on silicon, and 4 µm/h on Ti–6Al–4V were achieved. In a chemistry of H2/CH4/N
[...] Read more.
Nanostructured diamond (NSD) films were grown on silicon and Ti–6Al–4V alloy substrates by microwave plasma chemical vapor deposition (MPCVD). NSD Growth rates of 5 µm/h on silicon, and 4 µm/h on Ti–6Al–4V were achieved. In a chemistry of H2/CH4/N2, varying ratios of CH4/H2 and N2/CH4 were employed in this research and their effect on the resulting diamond films were studied by X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. As a result of modifying the stock cooling stage of CVD system, we were able to utilize plasma with high power densities in our NSD growth experiments, enabling us to achieve high growth rates. Substrate temperature and N2/CH4 ratio have been found to be key factors in determining the diamond film quality. NSD films grown as part of this study were shown to contain 85% to 90% sp3 bonded carbon. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Open AccessArticle Characterization of Thermo-Mechanical and Fracture Behaviors of Thermoplastic Polymers
Materials 2014, 7(1), 375-398; doi:10.3390/ma7010375
Received: 28 October 2013 / Revised: 14 December 2013 / Accepted: 16 December 2013 / Published: 13 January 2014
Cited by 7 | PDF Full-text (2961 KB) | HTML Full-text | XML Full-text
Abstract
In this paper the effects of the strain rate on the inelastic behavior and the self-heating under load conditions are presented for polymeric materials, such as polymethyl methacrylate (PMMA), polycarbonate (PC), and polyamide (PA66). By a torsion test, it was established that the
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In this paper the effects of the strain rate on the inelastic behavior and the self-heating under load conditions are presented for polymeric materials, such as polymethyl methacrylate (PMMA), polycarbonate (PC), and polyamide (PA66). By a torsion test, it was established that the shear yield stress behavior of PMMA, PC, and PA66 is well-described by the Ree-Eyring theory in the range of the considered strain rates. During the investigation, the surface temperature was monitored using an infrared camera. The heat release appeared at the early stage of the deformation and increased with the strain and strain rate. This suggested that the external work of deformation was dissipated into heat so the torsion tests could not be considered isothermal. Eventually, the effect of the strain rate on the failure modes was analyzed by scanning electron microscopy. Full article
(This article belongs to the Special Issue Smart Polymers and Polymeric Structures)
Open AccessArticle A Study of Crystalline Mechanism of Penetration Sealer Materials
Materials 2014, 7(1), 399-412; doi:10.3390/ma7010399
Received: 23 November 2013 / Revised: 31 December 2013 / Accepted: 7 January 2014 / Published: 14 January 2014
Cited by 3 | PDF Full-text (772 KB) | HTML Full-text | XML Full-text
Abstract
It is quite common to dispense a topping material like crystalline penetration sealer materials (CPSM) onto the surface of a plastic substance such as concrete to extend its service life span by surface protections from outside breakthrough. The CPSM can penetrate into the
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It is quite common to dispense a topping material like crystalline penetration sealer materials (CPSM) onto the surface of a plastic substance such as concrete to extend its service life span by surface protections from outside breakthrough. The CPSM can penetrate into the existing pores or possible cracks in such a way that it may form crystals to block the potential paths which provide breakthrough for any unknown materials. This study investigated the crystalline mechanism formed in the part of concrete penetrated by the CPSM. We analyzed the chemical composites, in order to identify the mechanism of CPSM and to evaluate the penetrated depth. As shown in the results, SEM observes the acicular-structured crystals filling capillary pores for mortar substrate of the internal microstructure beneath the concrete surface; meanwhile, XRD and FT-IR showed the main hydration products of CPSM to be C-S-H gel and CaCO3. Besides, MIP also shows CPSM with the ability to clog capillary pores of mortar substrate; thus, it reduces porosity, and appears to benefit in sealing pores or cracks. The depth of CPSM penetration capability indicated by TGA shows 0–10 mm of sealer layer beneath the concrete surface. Full article
(This article belongs to the Special Issue Construction Materials)
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Open AccessArticle Decoration of ZnO Nanorods with Coral Reefs like NiO Nanostructures by the Hydrothermal Growth Method and Their Luminescence Study
Materials 2014, 7(1), 430-440; doi:10.3390/ma7010430
Received: 10 November 2013 / Revised: 8 January 2014 / Accepted: 9 January 2014 / Published: 15 January 2014
Cited by 4 | PDF Full-text (479 KB) | HTML Full-text | XML Full-text
Abstract
Composite nanostructures of coral reefs like p-type NiO/n-type ZnO were synthesized on fluorine-doped tin oxide glass substrates by hydrothermal growth. Structural characterization was performed by field emission scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction techniques. This investigation shows that the
[...] Read more.
Composite nanostructures of coral reefs like p-type NiO/n-type ZnO were synthesized on fluorine-doped tin oxide glass substrates by hydrothermal growth. Structural characterization was performed by field emission scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction techniques. This investigation shows that the adopted synthesis leads to high crystalline quality nanostructures. The morphological study shows that the coral reefs like nanostructures are densely packed on the ZnO nanorods. Cathodoluminescence (CL) spectra for the synthesized composite nanostructures are dominated mainly by a broad interstitial defect related luminescence centered at ~630 nm. Spatially resolved CL images reveal that the luminescence of the decorated ZnO nanostructures is enhanced by the presence of the NiO. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle On the Rule of Mixtures for Predicting Stress-Softening and Residual Strain Effects in Biological Tissues and Biocompatible Materials
Materials 2014, 7(1), 441-456; doi:10.3390/ma7010441
Received: 30 October 2013 / Revised: 23 December 2013 / Accepted: 7 January 2014 / Published: 16 January 2014
Cited by 4 | PDF Full-text (715 KB) | HTML Full-text | XML Full-text
Abstract
In this work, we use the rule of mixtures to develop an equivalent material model in which the total strain energy density is split into the isotropic part related to the matrix component and the anisotropic energy contribution related to the fiber effects.
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In this work, we use the rule of mixtures to develop an equivalent material model in which the total strain energy density is split into the isotropic part related to the matrix component and the anisotropic energy contribution related to the fiber effects. For the isotropic energy part, we select the amended non-Gaussian strain energy density model, while the energy fiber effects are added by considering the equivalent anisotropic volumetric fraction contribution, as well as the isotropized representation form of the eight-chain energy model that accounts for the material anisotropic effects. Furthermore, our proposed material model uses a phenomenological non-monotonous softening function that predicts stress softening effects and has an energy term, derived from the pseudo-elasticity theory, that accounts for residual strain deformations. The model’s theoretical predictions are compared with experimental data collected from human vaginal tissues, mice skin, poly(glycolide-co-caprolactone) (PGC25 3-0) and polypropylene suture materials and tracheal and brain human tissues. In all cases examined here, our equivalent material model closely follows stress-softening and residual strain effects exhibited by experimental data. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle Diffuse Reflectance Infrared Fourier Transform Spectroscopy for the Determination of Asbestos Species in Bulk Building Materials
Materials 2014, 7(1), 457-470; doi:10.3390/ma7010457
Received: 25 November 2013 / Revised: 9 December 2013 / Accepted: 7 January 2014 / Published: 16 January 2014
Cited by 2 | PDF Full-text (255 KB) | HTML Full-text | XML Full-text
Abstract
Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy is a well-known technique for thin film characterization. Since all asbestos species exhibit intense adsorptions peaks in the 4000–400 cm−1 region of the infrared spectrum, a quantitative analysis of asbestos in bulk samples by DRIFT
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Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy is a well-known technique for thin film characterization. Since all asbestos species exhibit intense adsorptions peaks in the 4000–400 cm−1 region of the infrared spectrum, a quantitative analysis of asbestos in bulk samples by DRIFT is possible. In this work, different quantitative analytical procedures have been used to quantify chrysotile content in bulk materials produced by building requalification: partial least squares (PLS) chemometrics, the Linear Calibration Curve Method (LCM) and the Method of Additions (MoA). Each method has its own pros and cons, but all give affordable results for material characterization: the amount of asbestos (around 10%, weight by weight) can be determined with precision and accuracy (errors less than 0.1). Full article
Open AccessArticle Luminescent Properties of Surface Functionalized BaTiO3 Embedded in Poly(methyl methacrylate)
Materials 2014, 7(1), 471-483; doi:10.3390/ma7010471
Received: 1 December 2013 / Revised: 19 December 2013 / Accepted: 8 January 2014 / Published: 16 January 2014
Cited by 3 | PDF Full-text (645 KB) | HTML Full-text | XML Full-text
Abstract
As-received BaTiO3 nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyl)triethoxysilane (APTES) and mixed with poly(methyl methacrylate)/toluene solution. The nanocomposite solution was spin coated on Si substrates to form thin films. The photoluminescence spectrum of the pure
[...] Read more.
As-received BaTiO3 nanopowders of average grain sizes 50 nm and 100 nm were functionalized by (3-aminopropyl)triethoxysilane (APTES) and mixed with poly(methyl methacrylate)/toluene solution. The nanocomposite solution was spin coated on Si substrates to form thin films. The photoluminescence spectrum of the pure powder was composed of a bandgap emission at 3.0 eV and multiple bands centered about 2.5 eV. Surface functionalization of the BaTiO3 powder via APTES increases overall luminescence at room temperature while only enhancing bandgap emission at low-temperature. Polymer coating of the functionalized nanoparticles significantly enhances bandgap emissions while decreasing emissions associated with near-surface lattice distortions at 2.5 eV. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
Open AccessArticle Plastron Respiration Using Commercial Fabrics
Materials 2014, 7(1), 484-495; doi:10.3390/ma7010484
Received: 24 October 2013 / Revised: 6 January 2014 / Accepted: 13 January 2014 / Published: 16 January 2014
Cited by 4 | PDF Full-text (567 KB) | HTML Full-text | XML Full-text
Abstract
A variety of insect and arachnid species are able to remain submerged in water indefinitely using plastron respiration. A plastron is a surface-retained film of air produced by surface morphology that acts as an oxygen-carbon dioxide exchange surface. Many highly water repellent and
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A variety of insect and arachnid species are able to remain submerged in water indefinitely using plastron respiration. A plastron is a surface-retained film of air produced by surface morphology that acts as an oxygen-carbon dioxide exchange surface. Many highly water repellent and hydrophobic surfaces when placed in water exhibit a silvery sheen which is characteristic of a plastron. In this article, the hydrophobicity of a range of commercially available water repellent fabrics and polymer membranes is investigated, and how the surface of the materials mimics this mechanism of underwater respiration is demonstrated allowing direct extraction of oxygen from oxygenated water. The coverage of the surface with the plastron air layer was measured using confocal microscopy. A zinc/oxygen cell is used to consume oxygen within containers constructed from the different membranes, and the oxygen consumed by the cell is compared to the change in oxygen concentration as measured by an oxygen probe. By comparing the membranes to an air-tight reference sample, it was found that the membranes facilitated oxygen transfer from the water into the container, with the most successful membrane showing a 1.90:1 ratio between the cell oxygen consumption and the change in concentration within the container. Full article
(This article belongs to the Section Porous Materials)
Open AccessArticle Crystal Growth and Spectroscopic Investigations of Tm3+:Li3Ba2Gd3(MoO4)8 Crystal
Materials 2014, 7(1), 496-507; doi:10.3390/ma7010496
Received: 3 October 2013 / Revised: 11 December 2013 / Accepted: 17 December 2013 / Published: 17 January 2014
Cited by 3 | PDF Full-text (927 KB) | HTML Full-text | XML Full-text
Abstract
Tm3+:Li3Ba2Gd3(MoO4)8 crystal has been grown by the top seeded solution growth (TSSG) method from a Li2MoO4 flux. The room temperature polarized absorption spectra, fluorescence spectra, and fluorescence decay curves
[...] Read more.
Tm3+:Li3Ba2Gd3(MoO4)8 crystal has been grown by the top seeded solution growth (TSSG) method from a Li2MoO4 flux. The room temperature polarized absorption spectra, fluorescence spectra, and fluorescence decay curves of the crystal were measured. Based on the Judd-Ofelt (J-O) theory, the main spectroscopic parameters of the crystal, including the spontaneous emission probabilities, fluorescence branching ratios, and radiative lifetimes were calculated and analyzed. The broad and strong absorption bands of the crystal show that it can be efficiently pumped by the diode laser, while the large emission cross-sections of the 3F43H6 transition indicate that the crystal is a promising candidate for tunable and short pulse lasers. Full article
(This article belongs to the Special Issue Luminescent Materials 2013)
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Open AccessArticle Desorption of Furfural from Bimetallic Pt-Fe Oxides/Alumina Catalysts
Materials 2014, 7(1), 527-541; doi:10.3390/ma7010527
Received: 14 October 2013 / Revised: 10 January 2014 / Accepted: 13 January 2014 / Published: 20 January 2014
Cited by 1 | PDF Full-text (885 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the desorption of furfural, which is a competitive intermediate during the production of biofuel and valuable aromatic compounds, was studied using pure alumina, as well as alumina impregnated with iron and platinum oxides both individually and in combination, using thermogravimetric
[...] Read more.
In this work, the desorption of furfural, which is a competitive intermediate during the production of biofuel and valuable aromatic compounds, was studied using pure alumina, as well as alumina impregnated with iron and platinum oxides both individually and in combination, using thermogravimetric analysis (TGA). The bimetallic sample exhibited the lowest desorption percentage for furfural. High-resolution transmission electron microscopy (HRTEM) imaging revealed the intimate connection between the iron and platinum oxide species on the alumina support. The mechanism of furfural desorption from the Pt-Fe/Al2O3 0.5%-0.5% sample was determined using physisorbed furfural instead of chemisorbed furfural; this mechanism involved the oxidation of the C=O group on furfural by the catalyst. The oxide nanoparticles on γ-Al2O3 support helped to stabilize the furfural molecule on the surface. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle The Influence of Small Quantities of Oxygen in the Structure, Microstructure, Hardness, Elasticity Modulus and Cytocompatibility of Ti-Zr Alloys for Dental Applications
Materials 2014, 7(1), 542-553; doi:10.3390/ma7010542
Received: 31 October 2013 / Revised: 27 December 2013 / Accepted: 30 December 2013 / Published: 20 January 2014
Cited by 8 | PDF Full-text (726 KB) | HTML Full-text | XML Full-text
Abstract
The mechanical properties of Ti alloys are changed significantly with the addition of interstitial elements, such as oxygen. Because oxygen is a strong stabilizer of the α phase and has an effect on hardening in a solid solution, it has aroused great interest
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The mechanical properties of Ti alloys are changed significantly with the addition of interstitial elements, such as oxygen. Because oxygen is a strong stabilizer of the α phase and has an effect on hardening in a solid solution, it has aroused great interest in the biomedical area. In this paper, Ti-Zr alloys were subjected to a doping process with small amounts of oxygen. The influence of interstitial oxygen in the structure, microstructure and some selected mechanical properties of interest for use as biomaterial and biocompatibility of the alloys were analyzed. The results showed that in the range of 0.02 wt% to 0.04 wt%, oxygen has no influence on the structure, microstructure or biocompatibility of the studied alloys, but causes hardening of the alloys, increasing the values of the microhardness and causing variation in the elasticity modulus values. Full article
(This article belongs to the Special Issue Titanium Materials for Biomedical Application 2013)
Open AccessArticle Visible Light Curable Restorative Composites for Dental Applications Based on Epoxy Monomer
Materials 2014, 7(1), 554-562; doi:10.3390/ma7010554
Received: 29 November 2013 / Revised: 16 January 2014 / Accepted: 16 January 2014 / Published: 20 January 2014
Cited by 16 | PDF Full-text (395 KB) | HTML Full-text | XML Full-text
Abstract
A cationic photo-curable cycloaliphatic epoxy resin has been investigated as reactive monomer in blue light crosslinking process. We have demonstrated that camphorquinone is able to abstract labile hydrogen from the epoxy monomer, giving rise to the formation of carbon-centered radicals that are oxidized
[...] Read more.
A cationic photo-curable cycloaliphatic epoxy resin has been investigated as reactive monomer in blue light crosslinking process. We have demonstrated that camphorquinone is able to abstract labile hydrogen from the epoxy monomer, giving rise to the formation of carbon-centered radicals that are oxidized by the onium salt; a complete epoxy group conversion was reached after 50 s of irradiation. The presence of water up to 1 wt% was tolerated without any important detrimental effect on the kinetics of light-curing. The presence of the inorganic filler up to 65 wt% did not significantly influence the curing process. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
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Open AccessArticle High-Voltage Insulation Organic-Inorganic Nanocomposites by Plasma Polymerization
Materials 2014, 7(1), 563-575; doi:10.3390/ma7010563
Received: 13 December 2013 / Revised: 10 January 2014 / Accepted: 16 January 2014 / Published: 20 January 2014
Cited by 1 | PDF Full-text (1030 KB) | HTML Full-text | XML Full-text
Abstract
In organic-inorganic nanocomposites, interfacial regions are primarily influenced by the dispersion uniformity of nanoparticles and the strength of interfacial bonds between the nanoparticles and the polymer matrix. The insulating performance of organic-inorganic dielectric nanocomposites is highly influenced by the characteristics of interfacial regions.
[...] Read more.
In organic-inorganic nanocomposites, interfacial regions are primarily influenced by the dispersion uniformity of nanoparticles and the strength of interfacial bonds between the nanoparticles and the polymer matrix. The insulating performance of organic-inorganic dielectric nanocomposites is highly influenced by the characteristics of interfacial regions. In this study, we prepare polyethylene oxide (PEO)-like functional layers on silica nanoparticles through plasma polymerization. Epoxy resin/silica nanocomposites are subsequently synthesized with these plasma-polymerized nanoparticles. It is found that plasma at a low power (i.e., 10 W) can significantly increase the concentration of C–O bonds on the surface of silica nanoparticles. This plasma polymerized thin layer can not only improve the dispersion uniformity by increasing the hydrophilicity of the nanoparticles, but also provide anchoring sites to enable the formation of covalent bonds between the organic and inorganic phases. Furthermore, electrical tests reveal improved electrical treeing resistance and decreased dielectric constant of the synthesized nanocomposites, while the dielectric loss of the nanocomposites remains unchanged as compared to the pure epoxy resin. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
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Open AccessArticle A Constitutive Description for Shape Memory Alloys with the Growth of Martensite Band
Materials 2014, 7(1), 576-590; doi:10.3390/ma7010576
Received: 25 November 2013 / Revised: 23 December 2013 / Accepted: 15 January 2014 / Published: 20 January 2014
Cited by 1 | PDF Full-text (370 KB) | HTML Full-text | XML Full-text
Abstract
Based on the experimental results and the finite element analysis, a constitutive model is proposed for two phase shape memory alloys by introducing a compensative volumetric strain into a constrained relationship between the two phases, accounting for the reduced constraint due to the
[...] Read more.
Based on the experimental results and the finite element analysis, a constitutive model is proposed for two phase shape memory alloys by introducing a compensative volumetric strain into a constrained relationship between the two phases, accounting for the reduced constraint due to the growth of martensite band. The pseudoelasticity of NiTi shape memory alloy micro-tube, subjected to pure tension, is analyzed and compared with the experimental results. It can be seen that the pseudoelastic behavior, especially the phenomena of a stress drop during tension processes, can be well described with the proposed model. The proposed model separates the complicated constitutive behavior of a shape memory alloy (SMA) into simple responses arising respectively from its two phases, taking into account laminar microstructure, the thickness of martensite phase and the interaction between the two phases, and provides an easy but comprehensive method for the description of the constitutive behavior of SMAs under complex thermomechanical loading. Full article
(This article belongs to the Special Issue Shape Memory Materials)
Open AccessArticle Nanocomposites Based on Luminescent Colloidal Nanocrystals and Polymeric Ionic Liquids towards Optoelectronic Applications
Materials 2014, 7(1), 591-610; doi:10.3390/ma7010591
Received: 29 November 2013 / Revised: 9 January 2014 / Accepted: 16 January 2014 / Published: 21 January 2014
Cited by 2 | PDF Full-text (847 KB) | HTML Full-text | XML Full-text
Abstract
Polymeric ionic liquids (PILs) are an interesting class of polyelectrolytes, merging peculiar physical-chemical features of ionic liquids with the flexibility, mechanical stability and processability typical of polymers. The combination of PILs with colloidal semiconducting nanocrystals leads to novel nanocomposite materials with high potential
[...] Read more.
Polymeric ionic liquids (PILs) are an interesting class of polyelectrolytes, merging peculiar physical-chemical features of ionic liquids with the flexibility, mechanical stability and processability typical of polymers. The combination of PILs with colloidal semiconducting nanocrystals leads to novel nanocomposite materials with high potential for batteries and solar cells. We report the synthesis and properties of a hybrid nanocomposite made of colloidal luminescent CdSe nanocrystals incorporated in a novel ex situ synthesized imidazolium-based PIL, namely, either a poly(N-vinyl-3-butylimidazolium hexafluorophosphate) or a homologous PIL functionalized with a thiol end-group exhibiting a chemical affinity with the nanocrystal surface. A capping exchange procedure has been implemented for replacing the pristine organic capping molecules of the colloidal CdSe nanocrystals with inorganic chalcogenide ions, aiming to disperse the nano-objects in the PILs, by using a common polar solvent. The as-prepared nanocomposites have been studied by TEM investigation, UV-Vis, steady-state and time resolved photoluminescence spectroscopy for elucidating the effects of the PIL functionalization on the morphological and optical properties of the nanocomposites. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2013)
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Open AccessArticle A Self-Assembled Electro-Active M8L4 Cage Based on Tetrathiafulvalene Ligands
Materials 2014, 7(1), 611-622; doi:10.3390/ma7010611
Received: 29 November 2013 / Revised: 9 January 2014 / Accepted: 9 January 2014 / Published: 22 January 2014
Cited by 11 | PDF Full-text (876 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Two self-assembled redox-active cages are presented. They are obtained by coordination-driven self-assembly of a tetra-pyridile tetrathiafulvalene ligand with cis-M(dppf)(OTf)2 (M = Pd or Pt; dppf = 1,1′-bis(diphenylphosphino)ferrocene; OTf = trifluoromethane-sulfonate) complexes. Both species are fully characterized and are constituted of 12
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Two self-assembled redox-active cages are presented. They are obtained by coordination-driven self-assembly of a tetra-pyridile tetrathiafulvalene ligand with cis-M(dppf)(OTf)2 (M = Pd or Pt; dppf = 1,1′-bis(diphenylphosphino)ferrocene; OTf = trifluoromethane-sulfonate) complexes. Both species are fully characterized and are constituted of 12 electro-active subunits that can be reversibly oxidized. Full article
(This article belongs to the Special Issue Supramolecular Cage Complexes)
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Review

Jump to: Research, Other

Open AccessReview Green Adsorbents for Wastewaters: A Critical Review
Materials 2014, 7(1), 333-364; doi:10.3390/ma7010333
Received: 4 November 2013 / Revised: 26 December 2013 / Accepted: 31 December 2013 / Published: 13 January 2014
Cited by 41 | PDF Full-text (750 KB) | HTML Full-text | XML Full-text
Abstract
One of the most serious environmental problems is the existence of hazardous and toxic pollutants in industrial wastewaters. The major hindrance is the simultaneous existence of many/different types of pollutants as (i) dyes; (ii) heavy metals; (iii) phenols; (iv) pesticides and (v) pharmaceuticals.
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One of the most serious environmental problems is the existence of hazardous and toxic pollutants in industrial wastewaters. The major hindrance is the simultaneous existence of many/different types of pollutants as (i) dyes; (ii) heavy metals; (iii) phenols; (iv) pesticides and (v) pharmaceuticals. Adsorption is considered to be one of the most promising techniques for wastewater treatment over the last decades. The economic crisis of the 2000s led researchers to turn their interest in adsorbent materials with lower cost. In this review article, a new term will be introduced, which is called “green adsorption”. Under this term, it is meant the low-cost materials originated from: (i) agricultural sources and by-products (fruits, vegetables, foods); (ii) agricultural residues and wastes; (iii) low-cost sources from which most complex adsorbents will be produced (i.e., activated carbons after pyrolysis of agricultural sources). These “green adsorbents” are expected to be inferior (regarding their adsorption capacity) to the super-adsorbents of previous literature (complex materials as modified chitosans, activated carbons, structurally-complex inorganic composite materials etc.), but their cost-potential makes them competitive. This review is a critical approach to green adsorption, discussing many different (maybe in some occasions doubtful) topics such as: (i) adsorption capacity; (ii) kinetic modeling (given the ultimate target to scale up the batch experimental data to fixed-bed column calculations for designing/optimizing commercial processes) and (iii) critical techno-economical data of green adsorption processes in order to scale-up experiments (from lab to industry) with economic analysis and perspectives of the use of green adsorbents. Full article
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Other

Jump to: Research, Review

Open AccessConcept Paper Non-Destructive Thermography Analysis of Impact Damage on Large-Scale CFRP Automotive Parts
Materials 2014, 7(1), 413-429; doi:10.3390/ma7010413
Received: 30 September 2013 / Revised: 28 November 2013 / Accepted: 6 January 2014 / Published: 14 January 2014
Cited by 5 | PDF Full-text (1156 KB) | HTML Full-text | XML Full-text
Abstract
Laminated composites are increasingly used in aeronautics and the wind energy industry, as well as in the automotive industry. In these applications, the construction and processing need to fulfill the highest requirements regarding weight and mechanical properties. Environmental issues, like fuel consumption and
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Laminated composites are increasingly used in aeronautics and the wind energy industry, as well as in the automotive industry. In these applications, the construction and processing need to fulfill the highest requirements regarding weight and mechanical properties. Environmental issues, like fuel consumption and CO2-footprint, set new challenges in producing lightweight parts that meet the highly monitored standards for these branches. In the automotive industry, one main aspect of construction is the impact behavior of structural parts. To verify the quality of parts made from composite materials with little effort, cost and time, non-destructive test methods are increasingly used. A highly recommended non-destructive testing method is thermography analysis. In this work, a prototype for a car’s base plate was produced by using vacuum infusion. For research work, testing specimens were produced with the same multi-layer build up as the prototypes. These specimens were charged with defined loads in impact tests to simulate the effect of stone chips. Afterwards, the impacted specimens were investigated with thermography analysis. The research results in that work will help to understand the possible fields of application and the usage of thermography analysis as the first quick and economic failure detection method for automotive parts. Full article
Open AccessConcept Paper Mechanical Characterization of High-Performance Steel-Fiber Reinforced Cement Composites with Self-Healing Effect
Materials 2014, 7(1), 508-526; doi:10.3390/ma7010508
Received: 10 December 2013 / Revised: 2 January 2014 / Accepted: 7 January 2014 / Published: 20 January 2014
Cited by 6 | PDF Full-text (2408 KB) | HTML Full-text | XML Full-text
Abstract
The crack self-healing behavior of high-performance steel-fiber reinforced cement composites (HPSFRCs) was investigated. High-strength deformed steel fibers were employed in a high strength mortar with very fine silica sand to decreasing the crack width by generating higher interfacial bond strength. The width of
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The crack self-healing behavior of high-performance steel-fiber reinforced cement composites (HPSFRCs) was investigated. High-strength deformed steel fibers were employed in a high strength mortar with very fine silica sand to decreasing the crack width by generating higher interfacial bond strength. The width of micro-cracks, strongly affected by the type of fiber and sand, clearly produced the effects on the self-healing behavior. The use of fine silica sand in HPSFRCs with high strength deformed steel fibers successfully led to rapid healing owing to very fine cracks with width less than 20 µm. The use of very fine silica sand instead of normal sand produced 17%–19% higher tensile strength and 51%–58% smaller width of micro-cracks. Full article
(This article belongs to the Special Issue Self-healing Concrete)

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