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Materials, Volume 8, Issue 10 (October 2015), Pages 6589-7240

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Open AccessArticle Study of Fresh and Hardening Process Properties of Gypsum with Three Different PCM Inclusion Methods
Materials 2015, 8(10), 6589-6596; doi:10.3390/ma8105324
Received: 6 August 2015 / Revised: 10 September 2015 / Accepted: 15 September 2015 / Published: 24 September 2015
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Abstract
Gypsum has two important states (fresh and hardened states), and the addition of phase change materials (PCM) can vary the properties of the material. Many authors have extensively studied properties in the hardened state; however, the variation of fresh state properties due to
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Gypsum has two important states (fresh and hardened states), and the addition of phase change materials (PCM) can vary the properties of the material. Many authors have extensively studied properties in the hardened state; however, the variation of fresh state properties due to the addition of Micronal® DS 5001 X PCM into gypsum has been the object of few investigations. Properties in fresh state define the workability, setting time, adherence and shrinkage, and, therefore the possibility of implementing the material in building walls. The aim of the study is to analyze, compare and evaluate the variability of fresh state properties after the inclusion of 10% PCM. PCM are added into a common gypsum matrix by three different methods: adding microencapsulated PCM, making a suspension of PCM/water, and incorporating PCM through a vacuum impregnation method. Results demonstrate that the inclusion of PCM change completely the water required by the gypsum to achieve good workability, especially the formulation containing Micronal® DS 5001 X: the water required is higher, the retraction is lower (50% less) due to the organic nature of the PCM with high elasticity and, the adherence is reduced (up to 45%) due to the difference between the porosity of the different surfaces as well as the surface tension difference. Full article
Open AccessArticle Influence of Surface Modification on the Microstructure and Thermo-Mechanical Properties of Bamboo Fibers
Materials 2015, 8(10), 6597-6608; doi:10.3390/ma8105327
Received: 11 August 2015 / Revised: 2 September 2015 / Accepted: 21 September 2015 / Published: 24 September 2015
Cited by 7 | PDF Full-text (2849 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study is to investigate the effect of surface treatment on the morphology and thermo-mechanical properties of bamboo fibers. The fibers are subjected to an alkali treatment using 4 wt % sodium hydroxide (NaOH) for 1 h. Mechanical measurements show
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The objective of this study is to investigate the effect of surface treatment on the morphology and thermo-mechanical properties of bamboo fibers. The fibers are subjected to an alkali treatment using 4 wt % sodium hydroxide (NaOH) for 1 h. Mechanical measurements show that the present concentration has an insignificant effect on the fiber tensile strength. In addition, systematic experimental results characterizing the morphological aspects and thermal properties of the bamboo fibers are analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. It is found that an alkali treatment may increase the effective surface area, which is in turn available for superior bonding with the matrix. Fourier transform infrared spectroscopy analysis reveals that the alkali treatment leads to a gradual removal of binding materials, such as hemicellulose and lignin from the bamboo fiber. A comparison of the curve of thermogravimetric analysis and differential scanning calorimetry for the treated and untreated samples is presented to demonstrate that the presence of treatment contributes to a better thermal stability for bamboo fibers. Full article
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Open AccessArticle Fatigue Behavior of a Box-Type Welded Structure of Hydraulic Support Used in Coal Mine
Materials 2015, 8(10), 6609-6622; doi:10.3390/ma8105325
Received: 7 July 2015 / Revised: 7 September 2015 / Accepted: 8 September 2015 / Published: 24 September 2015
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Abstract
Hydraulic support is the main supporting equipment of the coal mining systems, and they are usually subjected to fatigue failure under the high dynamic load. The fracture positions are generally at welded joints where there is a serious stress concentration. In order to
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Hydraulic support is the main supporting equipment of the coal mining systems, and they are usually subjected to fatigue failure under the high dynamic load. The fracture positions are generally at welded joints where there is a serious stress concentration. In order to investigate and further improve the fatigue strength of hydraulic support, the present work first located the possible position where fatigue failure occurs through finite element analysis, and then fatigue tests were carried out on the different forms of welded joints for the dangerous parts. Finally, Fatigue strength-life (S-N) curves and fracture mechanism were studied. This research will provide a theoretical reference for the fatigue design of welded structures for hydraulic support. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Synthesis and Tribological Studies of Branched Alcohol Derived Epoxidized Biodiesel
Materials 2015, 8(10), 6623-6632; doi:10.3390/ma8105326
Received: 25 June 2015 / Revised: 25 August 2015 / Accepted: 21 September 2015 / Published: 24 September 2015
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Abstract
The optimization and kinetics of the ring-opening reaction of an epoxidized biodiesel (epoxidized rapeseed oil methyl ester) (EBD) with 2-ethyl hexanol (2-EH) were studied. The determined optimum conditions were 4:1 2-EH/oil molar ratio, 90 °C, 18 h, and 7 wt % of Amberlyst
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The optimization and kinetics of the ring-opening reaction of an epoxidized biodiesel (epoxidized rapeseed oil methyl ester) (EBD) with 2-ethyl hexanol (2-EH) were studied. The determined optimum conditions were 4:1 2-EH/oil molar ratio, 90 °C, 18 h, and 7 wt % of Amberlyst D001 (dry) catalyst; the product’s oxirane oxygen content was 0.081% with 38.32 mm2/s viscosity at 40 °C. The catalyst retained its high catalytic power after recycling five times. Furthermore, the determined non-catalyzed activation energy was 76 kJ·mol−1 and 54 kJ·mol−1 with the D001 resin catalyst. The product’s chemical structure was investigated through FT-IR and 1H NMR. The viscosity, flash point, pour point, and anti-wear properties of the product were improved compared with those of epoxidized biodiesel. Full article
Open AccessCommunication Fast Blue RR—Siloxane Derivatized Materials Indicate Wound Infection Due to a Deep Blue Color Development
Materials 2015, 8(10), 6633-6639; doi:10.3390/ma8105329
Received: 29 June 2015 / Revised: 10 September 2015 / Accepted: 21 September 2015 / Published: 25 September 2015
Cited by 1 | PDF Full-text (1025 KB) | HTML Full-text | XML Full-text
Abstract
There is a strong need for simple and fast methods for wound infection determination. Myeloperoxidase, an immune system-derived enzyme was found to be a suitable biomarker for wound infection. Hence, alkoxysilane-derivatized Fast Blue RR was immobilized via simple hydrolytic polymerization. The resulting enzyme-responsive
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There is a strong need for simple and fast methods for wound infection determination. Myeloperoxidase, an immune system-derived enzyme was found to be a suitable biomarker for wound infection. Hence, alkoxysilane-derivatized Fast Blue RR was immobilized via simple hydrolytic polymerization. The resulting enzyme-responsive siloxane layers were incubated with myeloperoxidase, wound fluid or hemoglobin. The reaction was monitored via HPLC measurements and the color development quantified spectrophotometrically. Myeloperoxidase was indeed able to oxidize immobilized Fast Blue RR leading to a blue colored product. No conversion was detected in non-infected wound fluids. The visible color changes of these novel materials towards blue enable an easy distinction between infected and non-infected wound fluids. Full article
Open AccessArticle Wear Improvement of Tools in the Cold Forging Process for Long Hex Flange Nuts
Materials 2015, 8(10), 6640-6657; doi:10.3390/ma8105328
Received: 18 August 2015 / Revised: 16 September 2015 / Accepted: 22 September 2015 / Published: 25 September 2015
Cited by 7 | PDF Full-text (7415 KB) | HTML Full-text | XML Full-text
Abstract
Cold forging has played a critical role in fasteners and has been widely used in automotive production, manufacturing, aviation and 3C (Computer, Communication, and Consumer electronics). Despite its extensive use in fastener forming and die design, operator experience and trial and error make
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Cold forging has played a critical role in fasteners and has been widely used in automotive production, manufacturing, aviation and 3C (Computer, Communication, and Consumer electronics). Despite its extensive use in fastener forming and die design, operator experience and trial and error make it subjective and unreliable owing to the difficulty of controlling the development schedule. This study used finite element analysis to establish and simulate wear in automotive repair fastener manufacturing dies based on actual process conditions. The places on a die that wore most quickly were forecast, with the stress levels obtained being substituted into the Archard equation to calculate die wear. A 19.87% improvement in wear optimization occurred by applying the Taguchi quality method to the new design. Additionally, a comparison of actual manufacturing data to simulations revealed a nut forging size error within 2%, thereby demonstrating the accuracy of this theoretical analysis. Finally, SEM micrographs of the worn surfaces on the upper punch indicate that the primary wear mechanism on the cold forging die for long hex flange nuts was adhesive wear. The results can simplify the development schedule, reduce the number of trials and further enhance production quality and die life. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Inexpensive Ipomoea aquatica Biomass-Modified Carbon Black as an Active Pt-Free Electrocatalyst for Oxygen Reduction Reaction in an Alkaline Medium
Materials 2015, 8(10), 6658-6667; doi:10.3390/ma8105331
Received: 13 July 2015 / Revised: 22 August 2015 / Accepted: 26 August 2015 / Published: 25 September 2015
Cited by 2 | PDF Full-text (1810 KB) | HTML Full-text | XML Full-text
Abstract
The development of inexpensive and active Pt-free catalysts as an alternative to Pt-based catalysts for oxygen reduction reaction (ORR) is an essential prerequisite for fuel cell commercialization. In this paper, we report a strategy for the design of a new Fe–N/C electrocatalyst derived
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The development of inexpensive and active Pt-free catalysts as an alternative to Pt-based catalysts for oxygen reduction reaction (ORR) is an essential prerequisite for fuel cell commercialization. In this paper, we report a strategy for the design of a new Fe–N/C electrocatalyst derived from the co-pyrolysis of Ipomoea aquatica biomass, carbon black (Vulcan XC-72R) and FeCl3·6H2O at 900 °C under nitrogen atmosphere. Electrochemical results show that the Fe–N/C catalyst exhibits higher electrocatalytic activity for ORR, longer durability and higher tolerance to methanol compared to a commercial Pt/C catalyst (40 wt %) in an alkaline medium. In particular, Fe–N/C presents an onset potential of 0.05 V (vs. Hg/HgO) for ORR in an alkaline medium, with an electron transfer number (n) of ~3.90, which is close to that of Pt/C. Our results confirm that the catalyst derived from I. aquatica and carbon black is a promising non-noble metal catalyst as an alternative to commercial Pt/C catalysts. Full article
(This article belongs to the Special Issue Porous Carbonaceous Materials from Biomass)
Open AccessArticle Performance-Enhanced Textured Silicon Solar Cells Based on Plasmonic Light Scattering Using Silver and Indium Nanoparticles
Materials 2015, 8(10), 6668-6676; doi:10.3390/ma8105330
Received: 29 June 2015 / Revised: 20 September 2015 / Accepted: 21 September 2015 / Published: 25 September 2015
Cited by 7 | PDF Full-text (9066 KB) | HTML Full-text | XML Full-text
Abstract
Performances of textured crystalline-silicon (c-Si) solar cells enhanced by silver nanoparticles (Ag-NPs) and indium nanoparticles (In-NPs) plasmonic effects are experimentally demonstrated and compared. Plasmonic nanoparticles integrated into textured c-Si solar cells can further increase the absorption and enhance the short-circuit current density (
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Performances of textured crystalline-silicon (c-Si) solar cells enhanced by silver nanoparticles (Ag-NPs) and indium nanoparticles (In-NPs) plasmonic effects are experimentally demonstrated and compared. Plasmonic nanoparticles integrated into textured c-Si solar cells can further increase the absorption and enhance the short-circuit current density (Jsc) of the solar cell. To examine the profile of the proposed metallic particles, the average diameter and coverage of the In-NPs (Ag-NPs) at 17.7 nm (19.07 nm) and 30.5% (35.1%), respectively, were obtained using scanning electron microscopy. Optical reflectance and external quantum efficiency response were used to measure plasmonic light scattering at various wavelengths. Compared to a bare reference cell, the application of In-NPs increased the Jsc of the cells by 8.64% (from 30.32 to 32.94 mA/cm2), whereas the application of Ag-NPs led to an increase of 4.71% (from 30.32 to 31.75 mA/cm2). The conversion efficiency of cells with embedded In-NPs (14.85%) exceeded that of cells with embedded Ag-NPs (14.32%), which can be attributed to the broadband plasmonic light scattering of the In-NPs. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Ultrathin Gas Permeable Oxide Membranes for Chemical Sensing: Nanoporous Ta2O5 Test Study
Materials 2015, 8(10), 6677-6684; doi:10.3390/ma8105333
Received: 24 August 2015 / Revised: 17 September 2015 / Accepted: 21 September 2015 / Published: 25 September 2015
Cited by 1 | PDF Full-text (1552 KB) | HTML Full-text | XML Full-text
Abstract
Conductometric gas sensors made of gas permeable metal oxide ultrathin membranes can combine the functions of a selective filter, preconcentrator, and sensing element and thus can be particularly promising for the active sampling of diluted analytes. Here we report a case study of
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Conductometric gas sensors made of gas permeable metal oxide ultrathin membranes can combine the functions of a selective filter, preconcentrator, and sensing element and thus can be particularly promising for the active sampling of diluted analytes. Here we report a case study of the electron transport and gas sensing properties of such a membrane made of nanoporous Ta2O5. These membranes demonstrated a noticeable chemical sensitivity toward ammonia, ethanol, and acetone at high temperatures above 400 °C. Different from traditional thin films, such gas permeable, ultrathin gas sensing elements can be made suspended enabling advanced architectures of ultrasensitive analytical systems operating at high temperatures and in harsh environments. Full article
(This article belongs to the Special Issue Nanostructured Materials for Chemical Sensing Applications)
Open AccessArticle Preparation, Characterization and Evaluation of α-Tocopherol Succinate-Modified Dextran Micelles as Potential Drug Carriers
Materials 2015, 8(10), 6685-6696; doi:10.3390/ma8105332
Received: 18 August 2015 / Revised: 13 September 2015 / Accepted: 17 September 2015 / Published: 28 September 2015
Cited by 7 | PDF Full-text (3896 KB) | HTML Full-text | XML Full-text | Correction
Abstract
In the present study, α-tocopherol succinate (TOS) conjugated dextran (Dex-TOS) was synthesized and characterized by fourier transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance (1H NMR), dynamic light scattering (DLS) and fluorescence spectroscopy. Dex-TOS could form nanoscaled micelles in aqueous
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In the present study, α-tocopherol succinate (TOS) conjugated dextran (Dex-TOS) was synthesized and characterized by fourier transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance (1H NMR), dynamic light scattering (DLS) and fluorescence spectroscopy. Dex-TOS could form nanoscaled micelles in aqueous medium. The critical micelle concentration (CMC) is 0.0034 mg/mL. Doxorubicin (Dox) was selected as a model drug. Dox-loaded Dex-TOS (Dex-TOS/Dox) micelles were prepared by a dialysis method. The size of Dex-TOS/Dox micelles increased from 295 to 325 nm with the Dox-loading content increasing from 4.21% to 8.12%. The Dex-TOS/Dox micelles were almost spherical in shape, as determined by transmission electron microscopy (TEM). In vitro release demonstrated that Dox release from the micelles was in a sustained manner for up to 96 h. The cellular uptake of Dex-TOS/Dox micelles in human nasopharyngeal epidermoid carcinoma (KB) cells is an endocytic process determined by confocal laser scanning microscopy (CLSM). Moreover, Dex-TOS/Dox micelles exhibited comparable cytotoxicity in contrast with doxorubicin hydrochloride. These results suggested that Dex-TOS micelles could be a promising carrier for drug delivery. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle Modeling Percolation in Polymer Nanocomposites by Stochastic Microstructuring
Materials 2015, 8(10), 6697-6718; doi:10.3390/ma8105334
Received: 2 July 2015 / Revised: 20 September 2015 / Accepted: 23 September 2015 / Published: 30 September 2015
Cited by 1 | PDF Full-text (6037 KB) | HTML Full-text | XML Full-text
Abstract
A methodology was developed for the prediction of the electrical properties of carbon nanotube-polymer nanocomposites via Monte Carlo computational simulations. A two-dimensional microstructure that takes into account waviness, fiber length and diameter distributions is used as a representative volume element. Fiber interactions in
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A methodology was developed for the prediction of the electrical properties of carbon nanotube-polymer nanocomposites via Monte Carlo computational simulations. A two-dimensional microstructure that takes into account waviness, fiber length and diameter distributions is used as a representative volume element. Fiber interactions in the microstructure are identified and then modeled as an equivalent electrical circuit, assuming one-third metallic and two-thirds semiconductor nanotubes. Tunneling paths in the microstructure are also modeled as electrical resistors, and crossing fibers are accounted for by assuming a contact resistance associated with them. The equivalent resistor network is then converted into a set of linear equations using nodal voltage analysis, which is then solved by means of the Gauss–Jordan elimination method. Nodal voltages are obtained for the microstructure, from which the percolation probability, equivalent resistance and conductivity are calculated. Percolation probability curves and electrical conductivity values are compared to those found in the literature. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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Open AccessArticle Bonding Properties of Basalt Fiber and Strength Reduction According to Fiber Orientation
Materials 2015, 8(10), 6719-6727; doi:10.3390/ma8105335
Received: 23 July 2015 / Revised: 10 August 2015 / Accepted: 23 September 2015 / Published: 30 September 2015
Cited by 4 | PDF Full-text (1115 KB) | HTML Full-text | XML Full-text
Abstract
The basalt fiber is a promising reinforcing fiber because it has a relatively higher tensile strength and a density similar to that of a concrete matrix as well as no corrosion possibility. This study investigated experimentally the bonding properties of basalt fiber with
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The basalt fiber is a promising reinforcing fiber because it has a relatively higher tensile strength and a density similar to that of a concrete matrix as well as no corrosion possibility. This study investigated experimentally the bonding properties of basalt fiber with cementitious material as well as the effect of fiber orientation on the tensile strength of basalt fiber for evaluating basalt fiber’s suitability as a reinforcing fiber. Single fiber pullout tests were performed and then the tensile strength of fiber was measured according to fiber orientation. The test results showed that basalt fiber has a strong chemical bond with the cementitious matrix, 1.88 times higher than that of polyvinyl alcohol fibers with it. However, other properties of basalt fiber such as slip-hardening coefficient and strength reduction coefficient were worse than PVA and polyethylene fibers in terms of fiber bridging capacity. Theoretical fiber-bridging curves showed that the basalt fiber reinforcing system has a higher cracking strength than the PVA fiber reinforcing system, but the reinforcing system showed softening behavior after cracking. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle Mechanical and Permeability Characteristics of Latex-Modified Pre-Packed Pavement Repair Concrete as a Function of the Rapid-Set Binder Content
Materials 2015, 8(10), 6728-6737; doi:10.3390/ma8105339
Received: 31 July 2015 / Revised: 13 September 2015 / Accepted: 28 September 2015 / Published: 1 October 2015
Cited by 1 | PDF Full-text (1723 KB) | HTML Full-text | XML Full-text
Abstract
We evaluated the strength and durability characteristics of latex-polymer-modified, pre-packed pavement repair concrete (LMPPRC) with a rapid-set binder. The rapid-set binder was a mixture of rapid-set cement and silica sand, where the fluidity was controlled using a latex polymer. The resulting mix exhibited
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We evaluated the strength and durability characteristics of latex-polymer-modified, pre-packed pavement repair concrete (LMPPRC) with a rapid-set binder. The rapid-set binder was a mixture of rapid-set cement and silica sand, where the fluidity was controlled using a latex polymer. The resulting mix exhibited a compressive strength of ¥21 MPa and a flexural strength of ¥3.5 MPa after 4 h of curing (i.e., the traffic opening term for emergency repairs of pavement). The ratio of latex polymer to rapid-set binder material was varied through 0.40, 0.33, 0.29, and 0.25. Mechanical characterization revealed that the mechanical performance, permeability, and impact resistance increased as the ratio of latex polymer to rapid-set binder decreased. The mixture exhibited a compressive strength of ¥21 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ¤0.29. The mixture exhibited a flexural strength of ¥3.5 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ¤0.33. The permeability resistance to chloride ions satisfied 2000 C after 7 days of curing for all ratios. The ratio of latex polymer to rapid-set binder material that satisfied all conditions for emergency pavement repair was ¤0.29. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle Influence of Fiber Orientation on Single-Point Cutting Fracture Behavior of Carbon-Fiber/Epoxy Prepreg Sheets
Materials 2015, 8(10), 6738-6751; doi:10.3390/ma8105336
Received: 17 July 2015 / Revised: 7 September 2015 / Accepted: 21 September 2015 / Published: 2 October 2015
Cited by 1 | PDF Full-text (13219 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this article is to investigate the influences of carbon fibers on the fracture mechanism of carbon fibers both in macroscopic view and microscopic view by using single-point flying cutting method. Cutting tools with three different materials were used in this
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The purpose of this article is to investigate the influences of carbon fibers on the fracture mechanism of carbon fibers both in macroscopic view and microscopic view by using single-point flying cutting method. Cutting tools with three different materials were used in this research, namely, PCD (polycrystalline diamond) tool, CVD (chemical vapor deposition) diamond thin film coated carbide tool and uncoated carbide tool. The influence of fiber orientation on the cutting force and fracture topography were analyzed and conclusions were drawn that cutting forces are not affected by cutting speeds but significantly influenced by the fiber orientation. Cutting forces presented smaller values in the fiber orientation of 0/180° and 15/165° but the highest one in 30/150°. The fracture mechanism of carbon fibers was studied in different cutting conditions such as 0° orientation angle, 90° orientation angle, orientation angles along fiber direction, and orientation angles inverse to the fiber direction. In addition, a prediction model on the cutting defects of carbon fiber reinforced plastic was established based on acoustic emission (AE) signals. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle Effect of Annealing Process on the Properties of Ni(55%)Cr(40%)Si(5%) Thin-Film Resistors
Materials 2015, 8(10), 6752-6760; doi:10.3390/ma8105338
Received: 12 August 2015 / Revised: 11 September 2015 / Accepted: 22 September 2015 / Published: 2 October 2015
Cited by 4 | PDF Full-text (1587 KB) | HTML Full-text | XML Full-text
Abstract
Resistors in integrated circuits (ICs) are implemented using diffused methods fabricated in the base and emitter regions of bipolar transistor or in source/drain regions of CMOS. Deposition of thin films on the wafer surface is another choice to fabricate the thin-film resistors in
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Resistors in integrated circuits (ICs) are implemented using diffused methods fabricated in the base and emitter regions of bipolar transistor or in source/drain regions of CMOS. Deposition of thin films on the wafer surface is another choice to fabricate the thin-film resistors in ICs’ applications. In this study, Ni(55%)Cr(40%)Si(5%) (abbreviated as NiCrSi) in wt % was used as the target and the sputtering method was used to deposit the thin-film resistors on Al2O3 substrates. NiCrSi thin-film resistors with different thicknesses of 30.8 nm~334.7 nm were obtained by controlling deposition time. After deposition, the thin-film resistors were annealed at 400 °C under different durations in N2 atmosphere using the rapid thermal annealing (RTA) process. The sheet resistance of NiCrSi thin-film resistors was measured using the four-point-probe method from 25 °C to 125 °C, then the temperature coefficient of resistance could be obtained. We aim to show that resistivity of NiCrSi thin-film resistors decreased with increasing deposition time (thickness) and the annealing process had apparent effect on the sheet resistance and temperature coefficient of resistance. We also aim to show that the annealed NiCrSi thin-film resistors had a low temperature coefficient of resistance (TCR) between 0 ppm/°C and +50 ppm/°C. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Improving Efficiency of Multicrystalline Silicon and CIGS Solar Cells by Incorporating Metal Nanoparticles
Materials 2015, 8(10), 6761-6771; doi:10.3390/ma8105337
Received: 25 August 2015 / Revised: 25 September 2015 / Accepted: 28 September 2015 / Published: 8 October 2015
Cited by 3 | PDF Full-text (12177 KB) | HTML Full-text | XML Full-text
Abstract
This work studies the use of gold (Au) and silver (Ag) nanoparticles in multicrystalline silicon (mc-Si) and copper-indium-gallium-diselenide (CIGS) solar cells. Au and Ag nanoparticles are deposited by spin-coating method, which is a simple and low cost process. The random distribution of nanoparticles
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This work studies the use of gold (Au) and silver (Ag) nanoparticles in multicrystalline silicon (mc-Si) and copper-indium-gallium-diselenide (CIGS) solar cells. Au and Ag nanoparticles are deposited by spin-coating method, which is a simple and low cost process. The random distribution of nanoparticles by spin coating broadens the resonance wavelength of the transmittance. This broadening favors solar cell applications. Metal shadowing competes with light scattering in a manner that varies with nanoparticle concentration. Experimental results reveal that the mc-Si solar cells that incorporate Au nanoparticles outperform those with Ag nanoparticles. The incorporation of suitable concentration of Au and Ag nanoparticles into mc-Si solar cells increases their efficiency enhancement by 5.6% and 4.8%, respectively. Incorporating Au and Ag nanoparticles into CIGS solar cells improve their efficiency enhancement by 1.2% and 1.4%, respectively. The enhancement of the photocurrent in mc-Si solar cells is lower than that in CIGS solar cells, owing to their different light scattering behaviors and material absorption coefficients. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Influence of Orientation and Radiative Heat Transfer on Aluminum Foams in Buoyancy-Induced Convection
Materials 2015, 8(10), 6792-6805; doi:10.3390/ma8105340
Received: 30 July 2015 / Revised: 21 September 2015 / Accepted: 23 September 2015 / Published: 9 October 2015
Cited by 6 | PDF Full-text (3608 KB) | HTML Full-text | XML Full-text
Abstract
Two differently-produced open-cell aluminum foams were compared to a commercially available finned heat sink. Further, an aluminum plate and block were tested as a reference. All heat sinks have the same base plate dimensions of four by six inches. The first foam was
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Two differently-produced open-cell aluminum foams were compared to a commercially available finned heat sink. Further, an aluminum plate and block were tested as a reference. All heat sinks have the same base plate dimensions of four by six inches. The first foam was made by investment casting of a polyurethane preform and has a porosity of 0.946 and a pore density of 10 pores per linear inch. The second foam is manufactured by casting over a solvable core and has a porosity of 0.85 and a pore density of 2.5 pores per linear inch. The effects of orientation and radiative heat transfer are experimentally investigated. The heat sinks are tested in a vertical and horizontal orientation. The effect of radiative heat transfer is investigated by comparing a painted/anodized heat sink with an untreated one. The heat flux through the heat sink for a certain temperature difference between the environment and the heat sink’s base plate is used as the performance indicator. For temperature differences larger than 30 °C, the finned heat sink outperforms the in-house-made aluminum foam heat sink on average by 17%. Furthermore, the in-house-made aluminum foam dissipates on average 12% less heat than the other aluminum foam for a temperature difference larger than 40 °C. By painting/anodizing the heat sinks, the heat transfer rate increased on average by 10% to 50%. Finally, the thermal performance of the horizontal in-house-made aluminum foam heat sink is up to 18% larger than the one of the vertical aluminum foam heat sink. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Inhibitory Effect of Waste Glass Powder on ASR Expansion Induced by Waste Glass Aggregate
Materials 2015, 8(10), 6849-6862; doi:10.3390/ma8105344
Received: 18 July 2015 / Revised: 21 September 2015 / Accepted: 28 September 2015 / Published: 9 October 2015
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Abstract
Detailed research is carried out to ascertain the inhibitory effect of waste glass powder (WGP) on alkali-silica reaction (ASR) expansion induced by waste glass aggregate in this paper. The alkali reactivity of waste glass aggregate is examined by two methods in accordance with
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Detailed research is carried out to ascertain the inhibitory effect of waste glass powder (WGP) on alkali-silica reaction (ASR) expansion induced by waste glass aggregate in this paper. The alkali reactivity of waste glass aggregate is examined by two methods in accordance with the China Test Code SL352-2006. The potential of WGP to control the ASR expansion is determined in terms of mean diameter, specific surface area, content of WGP and curing temperature. Two mathematical models are developed to estimate the inhibitory efficiency of WGP. These studies show that there is ASR risk with an ASR expansion rate over 0.2% when the sand contains more than 30% glass aggregate. However, WGP can effectively control the ASR expansion and inhibit the expansion rate induced by the glass aggregate to be under 0.1%. The two mathematical models have good simulation results, which can be used to evaluate the inhibitory effect of WGP on ASR risk. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
Open AccessCommunication Integrating Microtissues in Nanofiber Scaffolds for Regenerative Nanomedicine
Materials 2015, 8(10), 6863-6867; doi:10.3390/ma8105342
Received: 26 August 2015 / Revised: 18 September 2015 / Accepted: 28 September 2015 / Published: 9 October 2015
Cited by 4 | PDF Full-text (5359 KB) | HTML Full-text | XML Full-text
Abstract
A new generation of biomaterials focus on smart materials incorporating cells. Here, we describe a novel generation of synthetic nanofibrous implant functionalized with living microtissues for regenerative nanomedicine. The strategy designed here enhances the effectiveness of therapeutic implants compared to current approaches used
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A new generation of biomaterials focus on smart materials incorporating cells. Here, we describe a novel generation of synthetic nanofibrous implant functionalized with living microtissues for regenerative nanomedicine. The strategy designed here enhances the effectiveness of therapeutic implants compared to current approaches used in the clinic today based on single cells added to the implant. Full article
(This article belongs to the Special Issue Therapeutics Delivery Systems for Regenerative Nanomedicine)
Open AccessArticle Rice Husk Ash to Stabilize Heavy Metals Contained in Municipal Solid Waste Incineration Fly Ash: First Results by Applying New Pre-treatment Technology
Materials 2015, 8(10), 6868-6879; doi:10.3390/ma8105346
Received: 26 August 2015 / Revised: 25 September 2015 / Accepted: 29 September 2015 / Published: 9 October 2015
Cited by 5 | PDF Full-text (2669 KB) | HTML Full-text | XML Full-text
Abstract
A new technology was recently developed for municipal solid waste incineration (MSWI) fly ash stabilization, based on the employment of all waste and byproduct materials. In particular, the proposed method is based on the use of amorphous silica contained in rice husk ash
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A new technology was recently developed for municipal solid waste incineration (MSWI) fly ash stabilization, based on the employment of all waste and byproduct materials. In particular, the proposed method is based on the use of amorphous silica contained in rice husk ash (RHA), an agricultural byproduct material (COSMOS-RICE project). The obtained final inert can be applied in several applications to produce “green composites”. In this work, for the first time, a process for pre-treatment of rice husk, before its use in the stabilization of heavy metals, based on the employment of Instant Pressure Drop technology (DIC) was tested. The aim of this work is to verify the influence of the pre-treatment on the efficiency on heavy metals stabilization in the COSMOS-RICE technology. DIC technique is based on a thermomechanical effect induced by an abrupt transition from high steam pressure to a vacuum, to produce changes in the material. Two different DIC pre-treatments were selected and thermal annealing at different temperatures were performed on rice husk. The resulting RHAs were employed to obtain COSMOS-RICE samples, and the stabilization procedure was tested on the MSWI fly ash. In the frame of this work, some thermal treatments were also realized in O2-limiting conditions, to test the effect of charcoal obtained from RHA on the stabilization procedure. The results of this work show that the application of DIC technology into existing treatment cycles of some waste materials should be investigated in more details to offer the possibility to stabilize and reuse waste. Full article
(This article belongs to the Special Issue Green Composites)
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Open AccessArticle Contamination Effects on Improving the Hydrogenation/Dehydrogenation Kinetics of Binary Magnesium Hydride/Titanium Carbide Systems Prepared by Reactive Ball Milling
Materials 2015, 8(10), 6880-6892; doi:10.3390/ma8105350
Received: 18 August 2015 / Accepted: 15 September 2015 / Published: 10 October 2015
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Abstract
Ultrafine MgH2 nanocrystalline powders were prepared by reactive ball milling of elemental Mg powders after 200 h of high-energy ball milling under a hydrogen gas pressure of 50 bar. The as-prepared metal hydride powders were contaminated with 2.2 wt. % of FeCr-stainless
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Ultrafine MgH2 nanocrystalline powders were prepared by reactive ball milling of elemental Mg powders after 200 h of high-energy ball milling under a hydrogen gas pressure of 50 bar. The as-prepared metal hydride powders were contaminated with 2.2 wt. % of FeCr-stainless steel that was introduced to the powders upon using stainless steel milling tools made of the same alloy. The as-synthesized MgH2 was doped with previously prepared TiC nanopowders, which were contaminated with 2.4 wt. % FeCr (materials of the milling media), and then ball milled under hydrogen gas atmosphere for 50 h. The results related to the morphological examinations of the fabricated nanocomposite powders beyond the micro-and nano-levels showed excellent distributions of 5.2 wt. % TiC/4.6 wt. % FeCr dispersoids embedded into the fine host matrix of MgH2 powders. The as-fabricated nanocomposite MgH2/5.2 wt. % TiC/4.6 wt. % FeCr powders possessed superior hydrogenation/dehydrogenation characteristics, suggested by the low value of the activation energy (97.74 kJ/mol), and the short time required for achieving a complete absorption (6.6 min) and desorption (8.4 min) of 5.51 wt. % H2 at a moderate temperature of 275 °C under a hydrogen gas pressure ranging from 100 mbar to 8 bar. van’t Hoff approach was used to calculate the enthalpy (DH) and entropy (DS) of hydrogenation for MgH2, which was found to be -72.74 kJ/mol and 112.79 J/mol H2/K, respectively. Moreover, van’t Hoff method was employed to calculate the DH and DS of dehydrogenation, which was found to be 76.76 kJ/mol and 119.15 J/mol H2/K, respectively. This new nanocomposite system possessed excellent absorption/desorption cyclability of 696 complete cycles, achieved in a cyclic-life-time of 682 h. Full article
Open AccessArticle Study of a Steel’s Energy Absorption System for Heavy Quadricycles and Nonlinear Explicit Dynamic Analysis of its Behavior under Impact by FEM
Materials 2015, 8(10), 6893-6908; doi:10.3390/ma8105345
Received: 19 August 2015 / Accepted: 28 September 2015 / Published: 10 October 2015
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Abstract
Current knowledge of the behavior of heavy quadricycles under impact is still very poor. One of the most significant causes is the lack of energy absorption in the vehicle frame or its steel chassis structure. For this reason, special steels (with yield stresses
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Current knowledge of the behavior of heavy quadricycles under impact is still very poor. One of the most significant causes is the lack of energy absorption in the vehicle frame or its steel chassis structure. For this reason, special steels (with yield stresses equal to or greater than 350 MPa) are commonly used in the automotive industry due to their great strain hardening properties along the plastic zone, which allows good energy absorption under impact. This paper presents a proposal for a steel quadricycle energy absorption system which meets the percentages of energy absorption for conventional vehicles systems. This proposal is validated by explicit dynamics simulation, which will define the whole problem mathematically and verify behavior under impact at speeds of 40 km/h and 56 km/h using the finite element method (FEM). One of the main consequences of this study is that this FEM–based methodology can tackle high nonlinear problems like this one with success, avoiding the need to carry out experimental tests, with consequent economical savings since experimental tests are very expensive. Finally, the conclusions from this innovative research work are given. Full article
Open AccessArticle Global Warming Implications of the Use of By-Products and Recycled Materials in Western Australia’s Housing Sector
Materials 2015, 8(10), 6909-6925; doi:10.3390/ma8105347
Received: 11 September 2015 / Revised: 25 September 2015 / Accepted: 7 October 2015 / Published: 12 October 2015
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Abstract
Western Australia’s housing sector is growing rapidly and around half a million houses are expected to be built by 2030, which not only will result in increased energy and resources demand but will have socio-economic impacts. Majority of Western Australians live in detached
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Western Australia’s housing sector is growing rapidly and around half a million houses are expected to be built by 2030, which not only will result in increased energy and resources demand but will have socio-economic impacts. Majority of Western Australians live in detached houses made of energy intensive clay bricks, which have a high potential to generate construction and demolition (C&D) waste. Therefore, there is a need to look into the use of alternative materials and construction methods. Due to Western Australia’s temperate climate, concrete could not only offer a comfortable living space but an operational energy saving also can be achieved. This paper has assessed the global warming implications of cast in-situ concrete sandwich wall system as an alternative to clay brick walls (CBW) with partial replacement of cement in concrete with by-products such as fly ash (FA) and ground granulated blast furnace slag (GGBFS), natural aggregate (NA) with recycled crushed aggregate (RCA), natural sand (NS) with manufactured sand (MS) and, polyethylene terephthalate (PET) foam core as a replacement to polystyrene core for construction of a typical 4 × 2 × 2 detached house in Perth. Life cycle management (LCM) approach has been used to determine global warming reduction benefits due to the use of available by-products and recycled materials in Western Australian houses. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
Open AccessArticle Low-Temperature Solution-Processed Gate Dielectrics for High-Performance Organic Thin Film Transistors
Materials 2015, 8(10), 6926-6934; doi:10.3390/ma8105352
Received: 27 August 2015 / Revised: 23 September 2015 / Accepted: 8 October 2015 / Published: 12 October 2015
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Abstract
A low-temperature solution-processed high-k gate dielectric layer for use in a high-performance solution-processed semiconducting polymer organic thin-film transistor (OTFT) was demonstrated. Photochemical activation of sol-gel-derived AlOx films under 150 °C permitted the formation of a dense film with low leakage and relatively high
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A low-temperature solution-processed high-k gate dielectric layer for use in a high-performance solution-processed semiconducting polymer organic thin-film transistor (OTFT) was demonstrated. Photochemical activation of sol-gel-derived AlOx films under 150 °C permitted the formation of a dense film with low leakage and relatively high dielectric-permittivity characteristics, which are almost comparable to the results yielded by the conventionally used vacuum deposition and high temperature annealing method. Octadecylphosphonic acid (ODPA) self-assembled monolayer (SAM) treatment of the AlOx was employed in order to realize high-performance (>0.4 cm2/Vs saturation mobility) and low-operation-voltage (<5 V) diketopyrrolopyrrole (DPP)-based OTFTs on an ultra-thin polyimide film (3-μm thick). Thus, low-temperature photochemically-annealed solution-processed AlOx film with SAM layer is an attractive candidate as a dielectric-layer for use in high-performance organic TFTs operated at low voltages. Full article
Open AccessArticle Controlled Emissivity Coatings to Delay Ignition of Polyethylene
Materials 2015, 8(10), 6935-6949; doi:10.3390/ma8105349
Received: 9 June 2015 / Revised: 25 September 2015 / Accepted: 30 September 2015 / Published: 12 October 2015
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Abstract
Semi-opaque to opaque films containing small amounts of various aluminium particles to decrease emissivity were easily prepared and coated onto low-density polyethylene (LDPE) sheets. The thermal-radiative properties (reflectivity, transmissivity and absorptivity) of the films were measured and related to the aluminum particles’ content,
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Semi-opaque to opaque films containing small amounts of various aluminium particles to decrease emissivity were easily prepared and coated onto low-density polyethylene (LDPE) sheets. The thermal-radiative properties (reflectivity, transmissivity and absorptivity) of the films were measured and related to the aluminum particles’ content, size and nature. Time-to-ignition of samples was assessed using a cone calorimeter at different heat flux values (35, 50 and 75 kW/m2). The coatings allowed significant ignition delay and, in some cases, changed the material behaviour from thermally thin to thick behaviour. These effects are related both to their emissivity and transmissivity. A lower emissivity, which decreases during the degradation, and a lower transmissivity are the key points to ensure an optimal reaction-to-fire. Full article
Open AccessArticle Investigation of Key Parameters of Rock Cracking Using the Expansion of Vermiculite Materia
Materials 2015, 8(10), 6950-6961; doi:10.3390/ma8105351
Received: 15 July 2015 / Revised: 13 September 2015 / Accepted: 28 September 2015 / Published: 12 October 2015
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Abstract
The demand for the development of underground spaces has been sharply increased in lieu of saturated ground spaces because the residents of cities have steadily increased since the 1980s. The traditional widely used excavation methods (i.e., explosion and shield) have caused
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The demand for the development of underground spaces has been sharply increased in lieu of saturated ground spaces because the residents of cities have steadily increased since the 1980s. The traditional widely used excavation methods (i.e., explosion and shield) have caused many problems, such as noise, vibration, extended schedule, and increased costs. The vibration-free (and explosion-free) excavation method has currently attracted attention in the construction site because of the advantage of definitively solving these issues. For such reason, a new excavation method that utilizes the expansion of vermiculite with relatively fewer defects is proposed in this study. In general, vermiculite materials are rapidly expanded in volume when they receive thermal energy. Expansion pressure can be produced by thermal expansion of vermiculite in a steel tube, and measured by laboratory tests. The experimental tests are performed with various influencing parameters in an effort to seek the optimal condition to effectively increase expansion pressure at the same temperature. Then, calibrated expansion pressure is estimated, and compared to each model. After analyzing test results for expansion pressure, it is verified that vermiculite expanded by heat can provide enough internal pressure to break hard rock during tunneling work. Full article
Open AccessArticle Engineering Behavior and Characteristics of Wood Ash and Sugarcane Bagasse Ash
Materials 2015, 8(10), 6962-6977; doi:10.3390/ma8105353
Received: 7 August 2015 / Revised: 16 September 2015 / Accepted: 28 September 2015 / Published: 12 October 2015
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Abstract
Biomasses are organic materials that are derived from any living or recently-living structure. Plenty of biomasses are produced nationwide. Biomasses are mostly combusted and usually discarded or disposed of without treatment as biomass ashes, which include wood and sugarcane bagasse ashes. Thus, recycling
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Biomasses are organic materials that are derived from any living or recently-living structure. Plenty of biomasses are produced nationwide. Biomasses are mostly combusted and usually discarded or disposed of without treatment as biomass ashes, which include wood and sugarcane bagasse ashes. Thus, recycling or treatment of biomass ashes leads to utilizing the natural materials as an economical and environmental alternative. This study is intended to provide an environmental solution for uncontrolled disposal of biomass ashes by way of recycling the biomass ash and replacing the soils in geotechnical engineering projects. Therefore, in this study, characteristic tests of wood and sugarcane bagasse ashes that are considered the most common biomass ashes are conducted. The test of chemical compositions of biomass ashes is conducted using energy dispersive X-ray spectroscopy (EDS), and Scanning Electron Microscope (SEM), and heavy metal analysis is also conducted. Engineering behaviors including hydraulic conductivity, constrained modulus and shear modulus are examined. Also, coal fly ash Class C is used in this study for comparison with biomass ashes, and Ottawa 20/30 sands containing biomass ashes are examined to identify the soil replacement effect of biomass ashes. The results show that the particle sizes of biomass ashes are halfway between coal fly ash Class C and Ottawa 20/30 sand, and biomass ashes consist of a heterogeneous mixture of different particle sizes and shapes. Also, all heavy metal concentrations were found to be below the US Environmental Protection Agency (EPA) maximum limit. Hydraulic conductivity values of Ottawa 20/30 sand decrease significantly when replacing them with only 1%–2% of biomass ashes. While both the constrained modulus and shear modulus of biomass ashes are lower than Ottawa 20/30 sand, those of mixtures containing up to 10% biomass ashes are little affected by replacing the soils with biomass ashes. Full article
(This article belongs to the Section Materials for Energy Applications)
Open AccessArticle Optical, Structural and Paramagnetic Properties of Eu-Doped Ternary Sulfides ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y)
Materials 2015, 8(10), 6978-6998; doi:10.3390/ma8105348
Received: 7 August 2015 / Revised: 19 September 2015 / Accepted: 28 September 2015 / Published: 13 October 2015
Cited by 7 | PDF Full-text (4994 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Eu-doped ternary sulfides of general formula ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y) are presented as a novel interesting material family which may find usage as X-ray phosphors or solid state white light emitting diode (LED) lighting.
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Eu-doped ternary sulfides of general formula ALnS2 (A = Na, K, Rb; Ln = La, Gd, Lu, Y) are presented as a novel interesting material family which may find usage as X-ray phosphors or solid state white light emitting diode (LED) lighting. Samples were synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. Their physical properties were investigated by means of X-ray diffraction, time-resolved photoluminescence spectroscopy, electron paramagnetic resonance, and X-ray excited fluorescence. Corresponding characteristics, including absorption, radioluminescence, photoluminescence excitation and emission spectra, and decay kinetics curves, were measured and evaluated in a broad temperature range (8–800 K). Calculations including quantum local crystal field potential and spin-Hamiltonian for a paramagnetic particle in D3d local symmetry and phenomenological model dealing with excited state dynamics were performed to explain the experimentally observed features. Based on the results, an energy diagram of lanthanide energy levels in KLuS2 is proposed. Color model xy-coordinates are used to compare effects of dopants on the resulting spectrum. The application potential of the mentioned compounds in the field of white LED solid state lighting or X-ray phosphors is thoroughly discussed. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle The Promotion Strategy of Green Construction Materials: A Path Analysis Approach
Materials 2015, 8(10), 6999-7005; doi:10.3390/ma8105354
Received: 4 August 2015 / Revised: 22 September 2015 / Accepted: 28 September 2015 / Published: 14 October 2015
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Abstract
As one of the major materials used in construction, cement can be very resource-consuming and polluting to produce and use. Compared with traditional cement processing methods, dry-mix mortar is more environmentally friendly by reducing waste production or carbon emissions. Despite the continuous development
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As one of the major materials used in construction, cement can be very resource-consuming and polluting to produce and use. Compared with traditional cement processing methods, dry-mix mortar is more environmentally friendly by reducing waste production or carbon emissions. Despite the continuous development and promotion of green construction materials, only a few of them are accepted or widely used in the market. In addition, the majority of existing research on green construction materials focuses more on their physical or chemical characteristics than on their promotion. Without effective promotion, their benefits cannot be fully appreciated and realized. Therefore, this study is conducted to explore the promotion of dry-mix mortars, one of the green materials. This study uses both qualitative and quantitative methods. First, through a case study, the potential of reducing carbon emission is verified. Then a path analysis is conducted to verify the validity and predictability of the samples based on the technology acceptance model (TAM) in this study. According to the findings of this research, to ensure better promotion results and wider application of dry-mix mortar, it is suggested that more systematic efforts be invested in promoting the usefulness and benefits of dry-mix mortar. The model developed in this study can provide helpful references for future research and promotion of other green materials. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Fabrication of Microdots Using Piezoelectric Dispensing Technique for Viscous Fluids
Materials 2015, 8(10), 7006-7016; doi:10.3390/ma8105355
Received: 30 July 2015 / Revised: 22 September 2015 / Accepted: 8 October 2015 / Published: 14 October 2015
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Abstract
A simple microfluidic control method that uses a piezoelectric dispenser head is developed to fabricate microdots. A glycerol mixture was used as the test fluid to simulate conductive metallic solutions. The orifice diameter of the dispenser was 50 μm. Investigations were conducted at
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A simple microfluidic control method that uses a piezoelectric dispenser head is developed to fabricate microdots. A glycerol mixture was used as the test fluid to simulate conductive metallic solutions. The orifice diameter of the dispenser was 50 μm. Investigations were conducted at room temperature (25 °C). For each bipolar waveform, fluid was extruded in the form of a stretching liquid column, which eventually retracted into the dispenser orifice. Microdots were obtained by governing the liquid transfer process between the dispenser orifice and the target surface, where the gap was smaller than the maximum extrusion length during liquid column formation. Three fluid behaviors were observed using high-speed imaging, namely extrusion, impact on the target surface, and pinch-off of liquid ligament. For gaps of below 70 μm, some of the fluid sticking on the target surface resulted in a microdot diameter of 26 μm (about half of the orifice diameter). Full article
(This article belongs to the Section Materials for Energy Applications)
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Open AccessArticle Thermal, Electrical and Surface Hydrophobic Properties of Electrospun Polyacrylonitrile Nanofibers for Structural Health Monitoring
Materials 2015, 8(10), 7017-7031; doi:10.3390/ma8105356
Received: 24 August 2015 / Revised: 16 September 2015 / Accepted: 30 September 2015 / Published: 14 October 2015
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Abstract
This paper presents an idea of using carbonized electrospun Polyacrylonitrile (PAN) fibers as a sensor material in a structural health monitoring (SHM) system. The electrospun PAN fibers are lightweight, less costly and do not interfere with the functioning of infrastructure. This study deals
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This paper presents an idea of using carbonized electrospun Polyacrylonitrile (PAN) fibers as a sensor material in a structural health monitoring (SHM) system. The electrospun PAN fibers are lightweight, less costly and do not interfere with the functioning of infrastructure. This study deals with the fabrication of PAN-based nanofibers via electrospinning followed by stabilization and carbonization in order to remove all non-carbonaceous material and ensure pure carbon fibers as the resulting material. Electrochemical impedance spectroscopy was used to determine the ionic conductivity of PAN fibers. The X-ray diffraction study showed that the repeated peaks near 42° on the activated nanofiber film were α and β phases, respectively, with crystalline forms. Contact angle, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were also employed to examine the surface, thermal and chemical properties of the carbonized electrospun PAN fibers. The test results indicated that the carbonized PAN nanofibers have superior physical properties, which may be useful for structural health monitoring (SHM) applications in different industries. Full article
(This article belongs to the Special Issue Electrospun Materials)
Open AccessArticle Characterization and Curing Kinetics of Epoxy/Silica Nano-Hybrids
Materials 2015, 8(10), 7032-7040; doi:10.3390/ma8105357
Received: 31 August 2015 / Revised: 2 October 2015 / Accepted: 10 October 2015 / Published: 16 October 2015
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Abstract
The sol-gel technique was used to prepare epoxy/silica nano-hybrids. The thermal characteristics, curing kinetics and structure of epoxy/silica nano-hybrids were studied using differential scanning calorimetry (DSC), 29Si nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). To improve the compatibility between the
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The sol-gel technique was used to prepare epoxy/silica nano-hybrids. The thermal characteristics, curing kinetics and structure of epoxy/silica nano-hybrids were studied using differential scanning calorimetry (DSC), 29Si nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). To improve the compatibility between the organic and inorganic phases, a coupling agent was used to modify the diglycidyl ether of bisphenol A (DGEBA) epoxy. The sol-gel technique enables the silica to be successfully incorporated into the network of the hybrids, increasing the thermal stability and improving the mechanical properties of the prepared epoxy/silica nano-hybrids. An autocatalytic mechanism of the epoxy/SiO2 nanocomposites was observed. The low reaction rate of epoxy in the nanocomposites is caused by the steric hindrance in the network of hybrids that arises from the consuming of epoxide group in the network of hybrids by the silica. In the nanocomposites, the nano-scale silica particles had an average size of approximately 35 nm, and the particles were well dispersed in the epoxy matrix, according to the TEM images. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
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Open AccessCommunication The Histone Deacetylase Inhibitor JAHA Down-Regulates pERK and Global DNA Methylation in MDA-MB231 Breast Cancer Cells
Materials 2015, 8(10), 7041-7047; doi:10.3390/ma8105358
Received: 29 August 2015 / Revised: 7 October 2015 / Accepted: 9 October 2015 / Published: 16 October 2015
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Abstract
The histone deacetylase inhibitor N1-(ferrocenyl)-N8-hydroxyoctanediamide (JAHA) down-regulates extracellular-signal-regulated kinase (ERK) and its activated form in triple-negative MDA-MB231 breast cancer cells after 18 h and up to 30 h of treatment, and to a lesser extent AKT and phospho-AKT after
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The histone deacetylase inhibitor N1-(ferrocenyl)-N8-hydroxyoctanediamide (JAHA) down-regulates extracellular-signal-regulated kinase (ERK) and its activated form in triple-negative MDA-MB231 breast cancer cells after 18 h and up to 30 h of treatment, and to a lesser extent AKT and phospho-AKT after 30 h and up to 48 h of treatment. Also, DNA methyltransferase 1 (DNMT1), 3b and, to a lesser extent, 3a, downstream ERK targets, were down-regulated already at 18 h with an increase up to 48 h of exposure. Methylation-sensitive restriction arbitrarily-primed (MeSAP) polymerase chain reaction (PCR) analysis confirmed the ability of JAHA to induce genome-wide DNA hypomethylation at 48 h of exposure. Collective data suggest that JAHA, by down-regulating phospho-ERK, impairs DNMT1 and 3b expression and ultimately DNA methylation extent, which may be related to its cytotoxic effect on this cancer cytotype. Full article
(This article belongs to the Special Issue Organometallic Compounds 2015)
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Open AccessArticle Reduction Expansion Synthesis as Strategy to Control Nitrogen Doping Level and Surface Area in Graphene
Materials 2015, 8(10), 7048-7058; doi:10.3390/ma8105359
Received: 2 September 2015 / Revised: 8 October 2015 / Accepted: 9 October 2015 / Published: 16 October 2015
Cited by 4 | PDF Full-text (2207 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Graphene sheets doped with nitrogen were produced by the reduction-expansion (RES) method utilizing graphite oxide (GO) and urea as precursor materials. The simultaneous graphene generation and nitrogen insertion reactions are based on the fact that urea decomposes upon heating to release reducing gases.
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Graphene sheets doped with nitrogen were produced by the reduction-expansion (RES) method utilizing graphite oxide (GO) and urea as precursor materials. The simultaneous graphene generation and nitrogen insertion reactions are based on the fact that urea decomposes upon heating to release reducing gases. The volatile byproducts perform two primary functions: (i) promoting the reduction of the GO and (ii) providing the nitrogen to be inserted in situ as the graphene structure is created. Samples with diverse urea/GO mass ratios were treated at 800 °C in inert atmosphere to generate graphene with diverse microstructural characteristics and levels of nitrogen doping. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the microstructural features of the products. The effects of doping on the samples structure and surface area were studied by X-ray diffraction (XRD), Raman Spectroscopy, and Brunauer Emmet Teller (BET). The GO and urea decomposition-reduction process as well as nitrogen-doped graphene stability were studied by thermogravimetric analysis (TGA) coupled with mass spectroscopy (MS) analysis of the evolved gases. Results show that the proposed method offers a high level of control over the amount of nitrogen inserted in the graphene and may be used alternatively to control its surface area. To demonstrate the practical relevance of these findings, as-produced samples were used as electrodes in supercapacitor and battery devices and compared with conventional, thermally exfoliated graphene. Full article
Open AccessArticle Numerical Analysis of the Bending Properties of Cathay Poplar Glulam
Materials 2015, 8(10), 7059-7073; doi:10.3390/ma8105362
Received: 11 June 2015 / Revised: 24 September 2015 / Accepted: 28 September 2015 / Published: 19 October 2015
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Abstract
This paper presents the formulae and finite element analysis models for predicting the Modulus of Elastic (MOE) and Modulus of Rupture (MOR) of Cathay poplar finger-jointed glulam. The formula of the MOE predicts the MOE of Cathay poplar glulam glued with one-component polyurethane
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This paper presents the formulae and finite element analysis models for predicting the Modulus of Elastic (MOE) and Modulus of Rupture (MOR) of Cathay poplar finger-jointed glulam. The formula of the MOE predicts the MOE of Cathay poplar glulam glued with one-component polyurethane precisely. Three formulae are used to predict the MOR, and Equation (12) predicts the MOR of Cathay poplar glulam precisely. The finite element analysis simulation results of both the MOE and MOR are similar to the experimental results. The predicted results of the finite element analysis are shown to be more accurate than those of the formulae, because the finite element analysis considers the glue layers, but the formulae do not. Three types of typical failure modes due to bending were summarized. The bending properties of Cathay poplar glulam were compared to those of Douglas fir glulam. The results show that Cathay poplar glulam has a lower stiffness, but a marginally higher strength. One-component polyurethane adhesive is shown to be more effective than resorcinol formaldehyde resin adhesive for Cathay poplar glulam. This study shows that Cathay poplar has the potential to be a glulam material in China. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
Open AccessArticle A Micro Rectangular-Shaped Long-Period Fiber Grating Coated With Fe3O4 Nanoparticle Thin Overlay For Magnetic Sensing
Materials 2015, 8(10), 7074-7083; doi:10.3390/ma8105361
Received: 29 August 2015 / Revised: 3 October 2015 / Accepted: 8 October 2015 / Published: 19 October 2015
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Abstract
In this paper, we provide a novel micro rectangular-shaped long-period fiber grating (MRSLPFG) coated with Fe3O4 nanoparticles as the sensing material and packaged in polydimethylsiloxane (PDMS) for magnetic sensing application. The micro rectangular-shaped grating structures are fully dip coated with
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In this paper, we provide a novel micro rectangular-shaped long-period fiber grating (MRSLPFG) coated with Fe3O4 nanoparticles as the sensing material and packaged in polydimethylsiloxane (PDMS) for magnetic sensing application. The micro rectangular-shaped grating structures are fully dip coated with the magnetic fluid and heated to form a thin solid film. This thin overlay is used as the sensing media to measure the external magnetic flux density parallel to the optical fiber axis. According to our experimental results, the phenomenon of the transmission loss of the MRSLPFG magnetic sensor was increased monotonically when the external applied magnetic flux density increased. As the external applied magnetic flux density was increased from 0 to 91.10 mT, the resonance attenuation dip of the MRSLPFG increased and the average sensitivity achieved during the experiments was 0.129 dB/mT. We infer that the aforementioned experimental results were due to the magnetostrictive effect exerted on the thin layer of Fe3O4 nanoparticles, which in turn induced slight longitudinal strains on the micro rectangular-shaped fiber grating structures under different magnetic flux density. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Single-Crystal Y2O3 Epitaxially on GaAs(001) and (111) Using Atomic Layer Deposition
Materials 2015, 8(10), 7084-7093; doi:10.3390/ma8105364
Received: 9 August 2015 / Revised: 25 September 2015 / Accepted: 12 October 2015 / Published: 19 October 2015
Cited by 8 | PDF Full-text (1926 KB) | HTML Full-text | XML Full-text
Abstract
Single-crystal atomic-layer-deposited (ALD) Y\(_{\mathrm{2}}\)O\(_{\mathrm{3}}\) films 2 nm thick were epitaxially grown on molecular beam epitaxy (MBE) GaAs(001)-4 \(\times\) 6 and GaAs(111)A-2 \(\times\) 2 reconstructed surfaces. The in-plane epitaxy between the ALD-oxide films and GaAs was observed using \textit{in-situ} reflection high-energy electron diffraction in
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Single-crystal atomic-layer-deposited (ALD) Y\(_{\mathrm{2}}\)O\(_{\mathrm{3}}\) films 2 nm thick were epitaxially grown on molecular beam epitaxy (MBE) GaAs(001)-4 \(\times\) 6 and GaAs(111)A-2 \(\times\) 2 reconstructed surfaces. The in-plane epitaxy between the ALD-oxide films and GaAs was observed using \textit{in-situ} reflection high-energy electron diffraction in our uniquely designed MBE/ALD multi-chamber system. More detailed studies on the crystallography of the hetero-structures were carried out using high-resolution synchrotron radiation X-ray diffraction. When deposited on GaAs(001), the Y\(_{\mathrm{2}}\)O\(_{\mathrm{3}}\) films are of a cubic phase and have (110) as the film normal, with the orientation relationship being determined: Y\(_{\mathrm{2}}\)O\(_{\mathrm{3}}\)(\(110\))[\(001\)][\(\overline{1}10\)]//GaAs(\(001\))[\(110\)][\(1\overline{1}0\)]. On GaAs(\(111\))A, the Y\(_{\mathrm{2}}\)O\(_{\mathrm{3}}\) films are also of a cubic phase with (\(111\)) as the film normal, having the orientation relationship of Y\(_{\mathrm{2}}\)O\(_{\mathrm{3}}\)(\(111\))[\(2\overline{1}\overline{1}\)] [\(01\overline{1}\)]//GaAs (\(111\)) [\(\overline{2}11\)][\(0\overline{1}1\)]. The relevant orientation for the present/future integrated circuit platform is (\(001\)). The ALD-Y\(_{\mathrm{2}}\)O\(_{\mathrm{3}}\)/GaAs(\(001\))-4 \(\times\) 6 has shown excellent electrical properties. These include small frequency dispersion in the capacitance-voltage CV curves at accumulation of ~7% and ~14% for the respective p- and n-type samples with the measured frequencies of 1 MHz to 100 Hz. The interfacial trap density (Dit) is low of ~10\(^{12}\) cm\(^{−2}\)eV\(^{−1}\) as extracted from measured quasi-static CVs. The frequency dispersion at accumulation and the D\(_{it}\) are the lowest ever achieved among all the ALD-oxides on GaAs(\(001\)). Full article
(This article belongs to the Special Issue Epitaxial Materials 2015)
Open AccessArticle Numerical Study of the Effects of Residual Stress on Fretting Fatigue Using XFEM
Materials 2015, 8(10), 7094-7105; doi:10.3390/ma8105365
Received: 10 August 2015 / Revised: 4 October 2015 / Accepted: 9 October 2015 / Published: 19 October 2015
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Abstract
Residual compressive stress can improve fretting fatigue strength. In this paper, the effects of residual stress on fretting fatigue of Al 2024-T351 alloy specimens are studied using a numerical approach. The extended finite element method combined with the cyclic cohesive zone model is
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Residual compressive stress can improve fretting fatigue strength. In this paper, the effects of residual stress on fretting fatigue of Al 2024-T351 alloy specimens are studied using a numerical approach. The extended finite element method combined with the cyclic cohesive zone model is adopted to model fretting fatigue crack growth behavior. It is shown that residual stress changes the fretting fatigue crack growth path and enhances fretting fatigue life. Crack initiation angle, depth of knee point, crack initiation life, crack propagation life and total life are greater for specimens with residual stress compared to specimens without residual stress. The effects of residual stress are more remarkable for specimens with a high intensity of residual stress. However, the effects of residual stress reduce at a high bulk load level. Full article
Open AccessArticle Effect of Extrusion on the Mechanical and Rheological Properties of a Reinforced Poly(Lactic Acid): Reprocessing and Recycling of Biobased Materials
Materials 2015, 8(10), 7106-7117; doi:10.3390/ma8105360
Received: 21 August 2015 / Revised: 2 October 2015 / Accepted: 12 October 2015 / Published: 19 October 2015
Cited by 3 | PDF Full-text (4114 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this research paper is to study the behaviour of a common used biopolymer (Poly(Lactic Acid) (PLA)) after several reprocesses and how two different types of additives (a melt strength enhancer and a nanoadditive) affect its mechanical and rheological properties. Systematic
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The aim of this research paper is to study the behaviour of a common used biopolymer (Poly(Lactic Acid) (PLA)) after several reprocesses and how two different types of additives (a melt strength enhancer and a nanoadditive) affect its mechanical and rheological properties. Systematic extraction of extrudate samples from a twin-screw compounder was done in order to study the effect in the properties of the reprocessed material. Detailed rheological tests on a capillary rheometer as well as mechanical studies on a universal tensile machine after preparation of injected specimens were carried out. Results evidenced that PLA and reinforced PLA materials can be reprocessed and recycled without a remarkable loss in their mechanical properties. Several processing restrictions and specific phenomena were identified and are explained in the present manuscript. Full article
(This article belongs to the Special Issue Green Composites)
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Open AccessArticle Advanced Chemical Reduction of Reduced Graphene Oxide and Its Photocatalytic Activity in Degrading Reactive Black 5
Materials 2015, 8(10), 7118-7128; doi:10.3390/ma8105363
Received: 22 July 2015 / Revised: 18 August 2015 / Accepted: 21 August 2015 / Published: 19 October 2015
Cited by 14 | PDF Full-text (3006 KB) | HTML Full-text | XML Full-text
Abstract
Textile industries consume large volumes of water for dye processing, leading to undesirable toxic dyes in water bodies. Dyestuffs are harmful to human health and aquatic life, and such illnesses as cholera, dysentery, hepatitis A, and hinder the photosynthetic activity of aquatic plants.
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Textile industries consume large volumes of water for dye processing, leading to undesirable toxic dyes in water bodies. Dyestuffs are harmful to human health and aquatic life, and such illnesses as cholera, dysentery, hepatitis A, and hinder the photosynthetic activity of aquatic plants. To overcome this environmental problem, the advanced oxidation process is a promising technique to mineralize a wide range of dyes in water systems. In this work, reduced graphene oxide (rGO) was prepared via an advanced chemical reduction route, and its photocatalytic activity was tested by photodegrading Reactive Black 5 (RB5) dye in aqueous solution. rGO was synthesized by dispersing the graphite oxide into the water to form a graphene oxide (GO) solution followed by the addition of hydrazine. Graphite oxide was prepared using a modified Hummers’ method by using potassium permanganate and concentrated sulphuric acid. The resulted rGO nanoparticles were characterized using ultraviolet-visible spectrophotometry (UV-Vis), X-ray powder diffraction (XRD), Raman, and Scanning Electron Microscopy (SEM) to further investigate their chemical properties. A characteristic peak of rGO-48 h (275 cm−1) was observed in the UV spectrum. Further, the appearance of a broad peak (002), centred at 2θ = 24.1°, in XRD showing that graphene oxide was reduced to rGO. Based on our results, it was found that the resulted rGO-48 h nanoparticles achieved 49% photodecolorization of RB5 under UV irradiation at pH 3 in 60 min. This was attributed to the high and efficient electron transport behaviors of rGO between aromatic regions of rGO and RB5 molecules. Full article
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Open AccessArticle 3D Microstructure Effects in Ni-YSZ Anodes: Influence of TPB Lengths on the Electrochemical Performance
Materials 2015, 8(10), 7129-7144; doi:10.3390/ma8105370
Received: 17 September 2015 / Revised: 13 October 2015 / Accepted: 15 October 2015 / Published: 21 October 2015
Cited by 6 | PDF Full-text (5310 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
3D microstructure-performance relationships in Ni-YSZ anodes for electrolyte-supported cells are investigated in terms of the correlation between the triple phase boundary (TPB) length and polarization resistance (Rpol). Three different Ni-YSZ anodes of varying microstructure are subjected to eight reduction-oxidation (redox)
[...] Read more.
3D microstructure-performance relationships in Ni-YSZ anodes for electrolyte-supported cells are investigated in terms of the correlation between the triple phase boundary (TPB) length and polarization resistance (Rpol). Three different Ni-YSZ anodes of varying microstructure are subjected to eight reduction-oxidation (redox) cycles at 950 °C. In general the TPB lengths correlate with anode performance. However, the quantitative results also show that there is no simplistic relationship between TPB and Rpol. The degradation mechanism strongly depends on the initial microstructure. Finer microstructures exhibit lower degradation rates of TPB and Rpol. In fine microstructures, TPB loss is found to be due to Ni coarsening, while in coarse microstructures reduction of active TPB results mainly from loss of YSZ percolation. The latter is attributed to weak bottlenecks associated with lower sintering activity of the coarse YSZ. The coarse anode suffers from complete loss of YSZ connectivity and associated drop of TPBactive by 93%. Surprisingly, this severe microstructure degradation did not lead to electrochemical failure. Mechanistic scenarios are discussed for different anode microstructures. These scenarios are based on a model for coupled charge transfer and transport, which allows using TPB and effective properties as input. The mechanistic scenarios describe the microstructure influence on current distributions, which explains the observed complex relationship between TPB lengths and anode performances. The observed loss of YSZ percolation in the coarse anode is not detrimental because the electrochemical activity is concentrated in a narrow active layer. The anode performance can be predicted reliably if the volume-averaged properties (TPBactive, effective ionic conductivity) are corrected for the so-called short-range effect, which is particularly important in cases with a narrow active layer. Full article
(This article belongs to the Special Issue Electrode Materials)
Open AccessArticle Fatigue Life Prediction Based on Crack Closure and Equivalent Initial Flaw Size
Materials 2015, 8(10), 7145-7160; doi:10.3390/ma8105367
Received: 21 August 2015 / Revised: 2 October 2015 / Accepted: 13 October 2015 / Published: 21 October 2015
Cited by 3 | PDF Full-text (3273 KB) | HTML Full-text | XML Full-text
Abstract
Failure analysis and fatigue life prediction are necessary and critical for engineering structural materials. In this paper, a general methodology is proposed to predict fatigue life of smooth and circular-hole specimens, in which the crack closure model and equivalent initial flaw size (EIFS)
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Failure analysis and fatigue life prediction are necessary and critical for engineering structural materials. In this paper, a general methodology is proposed to predict fatigue life of smooth and circular-hole specimens, in which the crack closure model and equivalent initial flaw size (EIFS) concept are employed. Different effects of crack closure on small crack growth region and long crack growth region are considered in the proposed method. The EIFS is determined by the fatigue limit and fatigue threshold stress intensity factor Kth. Fatigue limit is directly obtained from experimental data, and Kth is calculated by using a back-extrapolation method. Experimental data for smooth and circular-hole specimens in three different alloys (Al2024-T3, Al7075-T6 and Ti-6Al-4V) under multiple stress ratios are used to validate the method. In the validation section, Semi-circular surface crack and quarter-circular corner crack are assumed to be the initial crack shapes for the smooth and circular-hole specimens, respectively. A good agreement is observed between model predictions and experimental data. The detailed analysis and discussion are performed on the proposed model. Some conclusions and future work are given. Full article
Open AccessArticle Deformation and Plateau Region of Functionally Graded Aluminum Foam by Amount Combinations of Added Blowing Agent
Materials 2015, 8(10), 7161-7168; doi:10.3390/ma8105366
Received: 2 August 2015 / Revised: 22 September 2015 / Accepted: 6 October 2015 / Published: 21 October 2015
PDF Full-text (2916 KB) | HTML Full-text | XML Full-text
Abstract
Recently, to further improve the performance of aluminum foam, functionally graded (FG) aluminum foams, whose pore structure varies with their position, have been developed. In this study, three types of FG aluminum foam of aluminum alloy die casting ADC12 with combinations of two
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Recently, to further improve the performance of aluminum foam, functionally graded (FG) aluminum foams, whose pore structure varies with their position, have been developed. In this study, three types of FG aluminum foam of aluminum alloy die casting ADC12 with combinations of two different amounts of added blowing agent titanium(II) hydride (TiH2) powder were fabricated by a friction stir welding (FSW) route precursor foaming method. The combinations of 1.0–0 mass %, 0.4–0 mass %, and 0.2–0 mass % TiH2 were selected as the amounts of TiH2 relative to the mass of the volume stirred by FSW. The static compression tests of the fabricated FG aluminum foams were carried out. The deformation and fracture of FG aluminum foams fundamentally started in the high-porosity (with TiH2 addition) layer and shifted to the low-porosity (without TiH2 addition) layer. The first and second plateau regions in the relationship between compressive stress and strain independently appeared with the occurrence of deformations and fractures in the high- and low-porosity layers. It was shown that FG aluminum foams, whose plateau region varies in steps by the combination of amounts of added TiH2 (i.e., the combination of pore structures), can be fabricated. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Improving Non-Destructive Concrete Strength Tests Using Support Vector Machines
Materials 2015, 8(10), 7169-7178; doi:10.3390/ma8105368
Received: 27 August 2015 / Revised: 16 September 2015 / Accepted: 13 October 2015 / Published: 22 October 2015
Cited by 2 | PDF Full-text (1812 KB) | HTML Full-text | XML Full-text
Abstract
Non-destructive testing (NDT) methods are important alternatives when destructive tests are not feasible to examine the in situ concrete properties without damaging the structure. The rebound hammer test and the ultrasonic pulse velocity test are two popular NDT methods to examine the properties
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Non-destructive testing (NDT) methods are important alternatives when destructive tests are not feasible to examine the in situ concrete properties without damaging the structure. The rebound hammer test and the ultrasonic pulse velocity test are two popular NDT methods to examine the properties of concrete. The rebound of the hammer depends on the hardness of the test specimen and ultrasonic pulse travelling speed is related to density, uniformity, and homogeneity of the specimen. Both of these two methods have been adopted to estimate the concrete compressive strength. Statistical analysis has been implemented to establish the relationship between hammer rebound values/ultrasonic pulse velocities and concrete compressive strength. However, the estimated results can be unreliable. As a result, this research proposes an Artificial Intelligence model using support vector machines (SVMs) for the estimation. Data from 95 cylinder concrete samples are collected to develop and validate the model. The results show that combined NDT methods (also known as SonReb method) yield better estimations than single NDT methods. The results also show that the SVM model is more accurate than the statistical regression model. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Fabrication of Aluminum Tubes Filled with Aluminum Alloy Foam by Friction Welding
Materials 2015, 8(10), 7180-7190; doi:10.3390/ma8105373
Received: 10 September 2015 / Revised: 8 October 2015 / Accepted: 10 October 2015 / Published: 23 October 2015
Cited by 8 | PDF Full-text (7049 KB) | HTML Full-text | XML Full-text
Abstract
Aluminum foam is usually used as the core of composite materials by combining it with dense materials, such as in Al foam core sandwich panels and Al-foam-filled tubes, owing to its low tensile and bending strengths. In this study, all-Al foam-filled tubes consisting
[...] Read more.
Aluminum foam is usually used as the core of composite materials by combining it with dense materials, such as in Al foam core sandwich panels and Al-foam-filled tubes, owing to its low tensile and bending strengths. In this study, all-Al foam-filled tubes consisting of ADC12 Al-Si-Cu die-cast aluminum alloy foam and a dense A1050 commercially pure Al tube with metal bonding were fabricated by friction welding. First, it was found that the ADC12 precursor was firmly bonded throughout the inner wall of the A1050 tube without a gap between the precursor and the tube by friction welding. No deformation of the tube or foaming of the precursor was observed during the friction welding. Next, it was shown that by heat treatment of an ADC12-precursor-bonded A1050 tube, gases generated by the decomposition of the blowing agent expand the softened ADC12 to produce the ADC12 foam interior of the dense A1050 tube. A holding time during the foaming process of approximately tH = 8.5 min with a holding temperature of 948 K was found to be suitable for obtaining a sound ADC12-foam-filled A1050 tube with sufficient foaming, almost uniform pore structures over the entire specimen, and no deformation or reduction in the thickness of the tube. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessArticle Effects of Electrodes on the Switching Behavior of Strontium Titanate Nickelate Resistive Random Access Memory
Materials 2015, 8(10), 7191-7198; doi:10.3390/ma8105374
Received: 30 August 2015 / Revised: 11 October 2015 / Accepted: 19 October 2015 / Published: 26 October 2015
Cited by 11 | PDF Full-text (3811 KB) | HTML Full-text | XML Full-text
Abstract
Strontium titanate nickelate (STN) thin films on indium tin oxide (ITO)/glass substrate were synthesized using the sol-gel method for resistive random access memory (RRAM) applications. Aluminum (Al), titanium (Ti), tungsten (W), gold (Au) and platinum (Pt) were used as top electrodes in the
[...] Read more.
Strontium titanate nickelate (STN) thin films on indium tin oxide (ITO)/glass substrate were synthesized using the sol-gel method for resistive random access memory (RRAM) applications. Aluminum (Al), titanium (Ti), tungsten (W), gold (Au) and platinum (Pt) were used as top electrodes in the STN-based RRAM to probe the switching behavior. The bipolar resistive switching behavior of the set and reset voltages is in opposite bias in the Al/STN/ITO and Pt/STN/ITO RRAMs, which can be partly ascribed to the different work functions of top electrodes in the ITO. Analyses of the fitting results and temperature-dependent performances showed that the Al/STN/ITO switching was mainly attributed to the absorption/release of oxygen-based functional groups, whereas the Pt/STN/ITO switching can be associated with the diffusion of metal electrode ions. The Al/STN/ITO RRAM demonstrated a high resistance ratio of >106 between the high-resistance state (HRS) and the low-resistance state (LRS), as well as a retention ability of >105 s. Furthermore, the Pt/STN/ITO RRAM displayed a HRS/LRS resistance ratio of >103 and a retention ability of >105 s. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Simplified Calculation Model and Experimental Study of Latticed Concrete-Gypsum Composite Panels
Materials 2015, 8(10), 7199-7216; doi:10.3390/ma8105375
Received: 21 August 2015 / Revised: 11 October 2015 / Accepted: 19 October 2015 / Published: 27 October 2015
Cited by 1 | PDF Full-text (8297 KB) | HTML Full-text | XML Full-text
Abstract
In order to address the performance complexity of the various constituent materials of (dense-column) latticed concrete-gypsum composite panels and the difficulty in the determination of the various elastic constants, this paper presented a detailed structural analysis of the (dense-column) latticed concrete-gypsum composite panel
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In order to address the performance complexity of the various constituent materials of (dense-column) latticed concrete-gypsum composite panels and the difficulty in the determination of the various elastic constants, this paper presented a detailed structural analysis of the (dense-column) latticed concrete-gypsum composite panel and proposed a feasible technical solution to simplified calculation. In conformity with mechanical rules, a typical panel element was selected and divided into two homogenous composite sub-elements and a secondary homogenous element, respectively for solution, thus establishing an equivalence of the composite panel to a simple homogenous panel and obtaining the effective formulas for calculating the various elastic constants. Finally, the calculation results and the experimental results were compared, which revealed that the calculation method was correct and reliable and could meet the calculation needs of practical engineering and provide a theoretical basis for simplified calculation for studies on composite panel elements and structures as well as a reference for calculations of other panels. Full article
Open AccessArticle Active Nanofibrous Membrane Effects on Gingival Cell Inflammatory Response
Materials 2015, 8(10), 7217-7229; doi:10.3390/ma8105376
Received: 25 August 2015 / Revised: 8 October 2015 / Accepted: 20 October 2015 / Published: 27 October 2015
Cited by 2 | PDF Full-text (10118 KB) | HTML Full-text | XML Full-text
Abstract
Alpha-melanocyte stimulating hormone (α-MSH) is involved in normal skin wound healing and also has anti-inflammatory properties. The association of α-MSH to polyelectrolyte layers with various supports has been shown to improve these anti-inflammatory properties. This study aimed to evaluate the effects of nanofibrous
[...] Read more.
Alpha-melanocyte stimulating hormone (α-MSH) is involved in normal skin wound healing and also has anti-inflammatory properties. The association of α-MSH to polyelectrolyte layers with various supports has been shown to improve these anti-inflammatory properties. This study aimed to evaluate the effects of nanofibrous membrane functionalized with α-MSH linked to polyelectrolyte layers on gingival cell inflammatory response. Human oral epithelial cells (EC) and fibroblasts (FB) were cultured on plastic or electrospun Poly-#-caprolactone (PCL) membranes with α-MSH covalently coupled to Poly-L-glutamic acid (PGA-α-MSH), for 6 to 24 h. Cells were incubated with or without Porphyromonas gingivalis lipopolysaccharide (Pg-LPS). Cell proliferation and migration were determined using AlamarBlue test and scratch assay. Expression of interleukin-6 (IL-6), tumor necrosis factor (TNF-α), and transforming growth factor-beta (TGF-β) was evaluated using RT-qPCR method. Cell cultures on plastic showed that PGA-α-MSH reduced EC and FB migration and decreased IL-6 and TGF-β expression in Pg-LPS stimulated EC. PGA-α-MSH functionalized PCL membranes reduced proliferation of Pg-LPS stimulated EC and FB. A significant decrease of IL-6, TNF-α, and TGF-β expression was also observed in Pg-LPS stimulated EC and FB. This study showed that the functionalization of nanofibrous PCL membranes efficiently amplified the anti-inflammatory effect of PGA-α-MSH on gingival cells. Full article
(This article belongs to the Special Issue Therapeutics Delivery Systems for Regenerative Nanomedicine)
Open AccessArticle The Effects of Zr Doping on the Optical, Electrical and Microstructural Properties of Thin ZnO Films Deposited by Atomic Layer Deposition
Materials 2015, 8(10), 7230-7240; doi:10.3390/ma8105369
Received: 16 September 2015 / Revised: 14 October 2015 / Accepted: 15 October 2015 / Published: 27 October 2015
Cited by 6 | PDF Full-text (1605 KB) | HTML Full-text | XML Full-text
Abstract
Transparent conducting oxides (TCOs), with high optical transparency (≥85%) and low electrical resistivity (10−4 Ω·cm) are used in a wide variety of commercial devices. There is growing interest in replacing conventional TCOs such as indium tin oxide with lower cost, earth abundant
[...] Read more.
Transparent conducting oxides (TCOs), with high optical transparency (≥85%) and low electrical resistivity (10−4 Ω·cm) are used in a wide variety of commercial devices. There is growing interest in replacing conventional TCOs such as indium tin oxide with lower cost, earth abundant materials. In the current study, we dope Zr into thin ZnO films grown by atomic layer deposition (ALD) to target properties of an efficient TCO. The effects of doping (0–10 at.% Zr) were investigated for ~100 nm thick films and the effect of thickness on the properties was investigated for 50–250 nm thick films. The addition of Zr4+ ions acting as electron donors showed reduced resistivity (1.44 × 10−3 Ω·cm), increased carrier density (3.81 × 1020 cm−3), and increased optical gap (3.5 eV) with 4.8 at.% doping. The increase of film thickness to 250 nm reduced the electron carrier/photon scattering leading to a further reduction of resistivity to 7.5 × 10−4 Ω·cm and an average optical transparency in the visible/near infrared (IR) range up to 91%. The improved n-type properties of ZnO: Zr films are promising for TCO applications after reaching the targets for high carrier density (>1020 cm−3), low resistivity in the order of 10−4 Ω·cm and high optical transparency (≥85%). Full article
(This article belongs to the Special Issue Atomic Layer Deposition of Functional Materials)

Review

Jump to: Research, Other

Open AccessReview Utilization of Field Enhancement in Plasmonic Waveguides for Subwavelength Light-Guiding, Polarization Handling, Heating, and Optical Sensing
Materials 2015, 8(10), 6772-6791; doi:10.3390/ma8105341
Received: 28 July 2015 / Revised: 6 September 2015 / Accepted: 17 September 2015 / Published: 9 October 2015
Cited by 6 | PDF Full-text (5728 KB) | HTML Full-text | XML Full-text
Abstract
Plasmonic nanostructures have attracted intensive attention for many applications in recent years because of the field enhancement at the metal/dielectric interface. First, this strong field enhancement makes it possible to break the diffraction limit and enable subwavelength optical waveguiding, which is desired for
[...] Read more.
Plasmonic nanostructures have attracted intensive attention for many applications in recent years because of the field enhancement at the metal/dielectric interface. First, this strong field enhancement makes it possible to break the diffraction limit and enable subwavelength optical waveguiding, which is desired for nanophotonic integrated circuits with ultra-high integration density. Second, the field enhancement in plasmonic nanostructures occurs only for the polarization mode whose electric field is perpendicular to the metal/dielectric interface, and thus the strong birefringence is beneficial for realizing ultra-small polarization-sensitive/selective devices, including polarization beam splitters, and polarizers. Third, plasmonic nanostructures provide an excellent platform of merging electronics and photonics for some applications, e.g., thermal tuning, photo-thermal detection, etc. Finally, the field enhancement at the metal/dielectric interface helps a lot to realize optical sensors with high sensitivity when introducing plasmonic nanostrutures. In this paper, we give a review for recent progresses on the utilization of field enhancement in plasmonic nanostructures for these applications, e.g., waveguiding, polarization handling, heating, as well as optical sensing. Full article
(This article belongs to the Special Issue Plasmonic Materials)
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Open AccessFeature PaperReview Polymer/Carbon-Based Hybrid Aerogels: Preparation, Properties and Applications
Materials 2015, 8(10), 6806-6848; doi:10.3390/ma8105343
Received: 25 August 2015 / Revised: 20 September 2015 / Accepted: 28 September 2015 / Published: 9 October 2015
Cited by 15 | PDF Full-text (7343 KB) | HTML Full-text | XML Full-text
Abstract
Aerogels are synthetic porous materials derived from sol-gel materials in which the liquid component has been replaced with gas to leave intact solid nanostructures without pore collapse. Recently, aerogels based on natural or synthetic polymers, called polymer or organic aerogels, have been widely
[...] Read more.
Aerogels are synthetic porous materials derived from sol-gel materials in which the liquid component has been replaced with gas to leave intact solid nanostructures without pore collapse. Recently, aerogels based on natural or synthetic polymers, called polymer or organic aerogels, have been widely explored due to their porous structures and unique properties, such as high specific surface area, low density, low thermal conductivity and dielectric constant. This paper gives a comprehensive review about the most recent progresses in preparation, structures and properties of polymer and their derived carbon-based aerogels, as well as their potential applications in various fields including energy storage, adsorption, thermal insulation and flame retardancy. To facilitate further research and development, the technical challenges are discussed, and several future research directions are also suggested in this review. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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Other

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Open AccessCorrection Correction: Thermal Stability and Magnetic Properties of Polyvinylidene Fluoride/Magnetite Nanocomposites. Materials 2015, 8, 4553–4564
Materials 2015, 8(10), 7179; doi:10.3390/ma8105371
Received: 29 May 2015 / Accepted: 10 July 2015 / Published: 22 October 2015
PDF Full-text (152 KB) | HTML Full-text | XML Full-text
Abstract
In the published manuscript, “Thermal Stability and Magnetic Properties of Polyvinylidene Fluoride/Magnetite Nanocomposites. Materials 2015, 8(7), 4553–4564” [1], we detected that in three places the explanations were slightly incorrect. We apologize for any inconvenience this may have caused. [...] Full article

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