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Materials, Volume 5, Issue 7 (July 2012) – 11 articles , Pages 1176-1335

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Open AccessReview
Surface Preparation and Deposited Gate Oxides for Gallium Nitride Based Metal Oxide Semiconductor Devices
Materials 2012, 5(7), 1297-1335; https://doi.org/10.3390/ma5071297 - 24 Jul 2012
Cited by 64 | Viewed by 6282
Abstract
The literature on polar Gallium Nitride (GaN) surfaces, surface treatments and gate dielectrics relevant to metal oxide semiconductor devices is reviewed. The significance of the GaN growth technique and growth parameters on the properties of GaN epilayers, the ability to modify GaN surface [...] Read more.
The literature on polar Gallium Nitride (GaN) surfaces, surface treatments and gate dielectrics relevant to metal oxide semiconductor devices is reviewed. The significance of the GaN growth technique and growth parameters on the properties of GaN epilayers, the ability to modify GaN surface properties using in situ and ex situ processes and progress on the understanding and performance of GaN metal oxide semiconductor (MOS) devices are presented and discussed. Although a reasonably consistent picture is emerging from focused studies on issues covered in each of these topics, future research can achieve a better understanding of the critical oxide-semiconductor interface by probing the connections between these topics. The challenges in analyzing defect concentrations and energies in GaN MOS gate stacks are discussed. Promising gate dielectric deposition techniques such as atomic layer deposition, which is already accepted by the semiconductor industry for silicon CMOS device fabrication, coupled with more advanced physical and electrical characterization methods will likely accelerate the pace of learning required to develop future GaN-based MOS technology. Full article
(This article belongs to the Special Issue High-k Materials and Devices)
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Open AccessArticle
Resin Flow Behavior Simulation of Grooved Foam Sandwich Composites with the Vacuum Assisted Resin Infusion (VARI) Molding Process
Materials 2012, 5(7), 1285-1296; https://doi.org/10.3390/ma5071285 - 23 Jul 2012
Cited by 5 | Viewed by 3669
Abstract
The resin flow behavior in the vacuum assisted resin infusion molding process (VARI) of foam sandwich composites was studied by both visualization flow experiments and computer simulation. Both experimental and simulation results show that: the distribution medium (DM) leads to a shorter molding [...] Read more.
The resin flow behavior in the vacuum assisted resin infusion molding process (VARI) of foam sandwich composites was studied by both visualization flow experiments and computer simulation. Both experimental and simulation results show that: the distribution medium (DM) leads to a shorter molding filling time in grooved foam sandwich composites via the VARI process, and the mold filling time is linearly reduced with the increase of the ratio of DM/Preform. Patterns of the resin sources have a significant influence on the resin filling time. The filling time of center source is shorter than that of edge pattern. Point pattern results in longer filling time than of linear source. Short edge/center patterns need a longer time to fill the mould compared with Long edge/center sources. Full article
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Open AccessArticle
Self-Assembly of Bi2Te3-Nanoplate/Graphene-Nanosheet Hybrid by One-Pot Route and Its Improved Li-Storage Properties
Materials 2012, 5(7), 1275-1284; https://doi.org/10.3390/ma5071275 - 23 Jul 2012
Cited by 18 | Viewed by 4727
Abstract
A sandwich structured Bi2Te3-nanoplates/graphene-nanosheet (Bi2Te3/G) hybrid has been synthesized by a facile in situ solvothermal route and has been investigated as a potential anode material for Li-ion batteries. Bi2Te3 grows during the [...] Read more.
A sandwich structured Bi2Te3-nanoplates/graphene-nanosheet (Bi2Te3/G) hybrid has been synthesized by a facile in situ solvothermal route and has been investigated as a potential anode material for Li-ion batteries. Bi2Te3 grows during the solvothermal process with the simultaneous reduction of graphite oxide into graphene. The in situ formation process of the hybrid has been investigated by X-ray diffraction and X-ray photoelectron spectra. The Li-storage mechanism and performance of Bi2Te3/G and bare Bi2Te3 have been studied by galvanostatic cycling and cyclic voltammetry. The Bi2Te3/G sandwich exhibits an obviously improved cycling stability compared to bare Bi2Te3. The enhancement in electrochemical performance can be attributed to the combined conducting, confining and dispersing effects of graphene for Bi2Te3 nanoplates and to the self-assembled sandwich structure. Full article
(This article belongs to the Special Issue Advanced Materials for Lithium Ion Batteries)
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Open AccessArticle
Effect of Elemental Powder Size on Foaming Behavior of NiTi Alloy Made by Combustion Synthesis
Materials 2012, 5(7), 1267-1274; https://doi.org/10.3390/ma5071267 - 23 Jul 2012
Cited by 5 | Viewed by 2585
Abstract
Nickel titanium (NiTi) foams were made by combustion synthesis of powders with the help of ZrH2 as foaming agent and TiB2 as endothermic agent. In this paper, we investigated the effect of elemental powder size on the foaming. The powder size [...] Read more.
Nickel titanium (NiTi) foams were made by combustion synthesis of powders with the help of ZrH2 as foaming agent and TiB2 as endothermic agent. In this paper, we investigated the effect of elemental powder size on the foaming. The powder size of Ni and Ti affected the ignition temperature of the combustion reaction, cell morphology and microstructure of the foams. The cell morphology of the foams was also modified by the powder size of TiB2. Full article
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Open AccessArticle
Pseudocapacitive Effects of N-Doped Carbon Nanotube Electrodes in Supercapacitors
Materials 2012, 5(7), 1258-1266; https://doi.org/10.3390/ma5071258 - 19 Jul 2012
Cited by 55 | Viewed by 4258
Abstract
Nitrogen- and micropore-containing carbon nanotubes (NMCNTs) were prepared by carbonization of nitrogen-enriched, polymer-coated carbon nanotubes (CNTs), and the electrochemical performances of the NMCNTs with different heteroatom contents were investigated. NMCNTs-700 containing 9.1 wt% nitrogen atoms had a capacitance of 190.8 F/g, which was [...] Read more.
Nitrogen- and micropore-containing carbon nanotubes (NMCNTs) were prepared by carbonization of nitrogen-enriched, polymer-coated carbon nanotubes (CNTs), and the electrochemical performances of the NMCNTs with different heteroatom contents were investigated. NMCNTs-700 containing 9.1 wt% nitrogen atoms had a capacitance of 190.8 F/g, which was much higher than that of pristine CNTs (48.4 F/g), despite the similar surface area of the two CNTs, and was also higher than that of activated CNTs (151.7 F/g) with a surface area of 778 m2/g and a nitrogen atom content of 1.2 wt%. These results showed that pseudocapacitive effects play an important role in the electrochemical performance of supercapacitor electrodes. Full article
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Open AccessArticle
Laser Treatment of Cotton Fabric for Durable Antibacterial Properties of Silver Nanoparticles
Materials 2012, 5(7), 1247-1257; https://doi.org/10.3390/ma5071247 - 16 Jul 2012
Cited by 28 | Viewed by 3615
Abstract
In the present study, cotton fabric was exposed to laser exposure at different energy levels and then the silver nanoparticles were coated on untreated and laser treated cotton fabrics. Methylene blue dye was used to detect the presence of carboxylic acid groups (-COO [...] Read more.
In the present study, cotton fabric was exposed to laser exposure at different energy levels and then the silver nanoparticles were coated on untreated and laser treated cotton fabrics. Methylene blue dye was used to detect the presence of carboxylic acid groups (-COO) on laser treated cotton and the dye absorption results were determined spectrophotometrically. ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy) analysis and antibacterial tests were carried out to investigate the silver ion content and bactericidal properties of silver nanoparticles on cotton fabrics. Infrared spectroscopy (FTIR/ATR) analysis and scanning electron microscopy (SEM) were used to identify chemical changes and to study the morphology of the surface of the fibers. EDAX (Energy Dispersive X-ray Spectroscopy) analysis was calculated for SEM micrographs. The results showed according to the higher uptake of methylene blue dye that the negative charge of the carboxylic acid groups had been created by laser treatment. Although the FTIR spectroscopy results did not show an increase in carboxylic acid groups, the cationic dye absorption increased. The durability of the Ag+ ion particles on repeated laundered laser treated cotton was proven by antibacterial and ICP tests, particularly when the laser energy was increased. Full article
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Open AccessReview
Stockpiling and Comprehensive Utilization of Red Mud Research Progress
Materials 2012, 5(7), 1232-1246; https://doi.org/10.3390/ma5071232 - 16 Jul 2012
Cited by 48 | Viewed by 3614
Abstract
With increasing production of red mud, the environmental problems caused by it are increasingly serious, and thus the integrated treatment of red mud is imminent. This article provides an overview of the composition and the basic characteristics of red mud. The research progress [...] Read more.
With increasing production of red mud, the environmental problems caused by it are increasingly serious, and thus the integrated treatment of red mud is imminent. This article provides an overview of the composition and the basic characteristics of red mud. The research progress of safe stockpiling and comprehensive utilization of red mud is summarized. The safe stockpiling of red mud can be divided into two aspects: the design and safe operation of the stocking yard. The comprehensive utilization of red mud can be further divided into three aspects: the effective recycling of components, resource utilization and application in the field of environmental protection. This paper points out that the main focus of previous studies on red mud stockpiling is cost reproduction and land tenure. The recovery of resources from red mud has a high value-added, but low level industrialization. The use of red mud as a building material and filler material is the most effective way to reduce the stockpiling of red mud. Red mud used for environmental remediation materials is a new hotspot and worth promoting for its simple processing and low cost. Full article
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Open AccessArticle
Solid-State Synthesis of Polyaniline/Single-Walled Carbon Nanotubes: A Comparative Study with Polyaniline/Multi-Walled Carbon Nanotubes
Materials 2012, 5(7), 1219-1231; https://doi.org/10.3390/ma5071219 - 16 Jul 2012
Cited by 16 | Viewed by 3882
Abstract
The polyaniline/single-walled carbon nanotubes (PANI/SWNTs) composites with a content of SWNTs varying from 8 wt% to 32 wt% were synthesized using a solid-state synthesis method. The structure and morphology of the samples were characterized by fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-vis) absorption [...] Read more.
The polyaniline/single-walled carbon nanotubes (PANI/SWNTs) composites with a content of SWNTs varying from 8 wt% to 32 wt% were synthesized using a solid-state synthesis method. The structure and morphology of the samples were characterized by fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-vis) absorption spectra, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrochemical performances of the composites were investigated by galvanostatic charge–discharge and cycling stability measurements. The structure and properties of PANI/SWNTs were compared with those of PANI/multi-walled carbon nanotubes (PANI/MWNTs) prepared under the same polymerization conditions. The results from FTIR and UV-vis spectra showed that the composites with SWNTs displayed a higher oxidation and doping degree than pure PANI, which is similar to that of PANI/MWNTs. The morphological studies revealed that PANI/SWNTs did not display any rod-like and granular-like features, which appeared in PANI/MWNTs. The galvanostatic charge–discharge measurements indicated that the specific capacitance of PANI/SWNTs is not higher than that of PANI/MWNTs, but the PANI/SWNTs exhibited higher cycling stability and more stable electrochemical behavior in neutral and alkaline electrolytes than PANI/MWNTs. Full article
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Open AccessArticle
Effect of Alkyl Chain Length on Carboxylic Acid SAMs on Ti-6Al-4V
Materials 2012, 5(7), 1206-1218; https://doi.org/10.3390/ma5071206 - 09 Jul 2012
Cited by 7 | Viewed by 3644
Abstract
The formation of methyl-terminated carboxylic acid self-assembled monolayers (SAMs) with even numbers of carbons, from eighteen to thirty, was investigated on the oxide surface of Ti-6Al-4V and component metal oxides. Modified surfaces were characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), matrix [...] Read more.
The formation of methyl-terminated carboxylic acid self-assembled monolayers (SAMs) with even numbers of carbons, from eighteen to thirty, was investigated on the oxide surface of Ti-6Al-4V and component metal oxides. Modified surfaces were characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and contact angle analysis. Infrared spectroscopy indicated that using aerosol spray deposition techniques, stable, all-trans SAMs of octacosanoic (28 carbons) and triacontanoic (30 carbons) acids were formed on the alloy. Films were similarly formed on titanium and aluminum oxide. The surface of vanadium oxide exhibited limited reactivity. MALDI-TOF MS confirmed that formed films were monolayers, without multilayers or aggregates present. Water contact angles are indicative of the presence of hydrophobic methyl groups at the interface. This stable carboxylic acid SAM formation could be a useful alternative to phosphonic acid SAMs for corrosion and other applications. Full article
(This article belongs to the Special Issue Titanium Materials for Biomedical Application)
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Open AccessArticle
Photonic Paint Developed with Metallic Three-Dimensional Photonic Crystals
Materials 2012, 5(7), 1196-1205; https://doi.org/10.3390/ma5071196 - 02 Jul 2012
Cited by 3 | Viewed by 3600
Abstract
This work details the design and simulation of an inconspicuous photonic paint that can be applied onto an object for anticounterfeit and tag, track, and locate (TTL) applications. The paint consists of three-dimensional metallic tilted woodpile photonic crystals embedded into a visible and [...] Read more.
This work details the design and simulation of an inconspicuous photonic paint that can be applied onto an object for anticounterfeit and tag, track, and locate (TTL) applications. The paint consists of three-dimensional metallic tilted woodpile photonic crystals embedded into a visible and infrared transparent polymer film, which can be applied to almost any surface. The tilted woodpile photonic crystals are designed with a specific pass band detectable at nearly all incident angles of light. When painted onto a surface, these crystals provide a unique reflective infra-red optical signature that can be easily observed and recorded to verify the location or contents of a package. Full article
(This article belongs to the Special Issue Photonic Materials and Applications)
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Open AccessArticle
Automatic Actin Filament Quantification of Osteoblasts and Their Morphometric Analysis on Microtextured Silicon-Titanium Arrays
Materials 2012, 5(7), 1176-1195; https://doi.org/10.3390/ma5071176 - 27 Jun 2012
Cited by 28 | Viewed by 4173
Abstract
Microtexturing of implant surfaces is of major relevance in the endeavor to improve biorelevant implant designs. In order to elucidate the role of biomaterial’s topography on cell physiology, obtaining quantitative correlations between cellular behavior and distinct microarchitectural properties is in great demand. Until [...] Read more.
Microtexturing of implant surfaces is of major relevance in the endeavor to improve biorelevant implant designs. In order to elucidate the role of biomaterial’s topography on cell physiology, obtaining quantitative correlations between cellular behavior and distinct microarchitectural properties is in great demand. Until now, the microscopically observed reorganization of the cytoskeleton on structured biomaterials has been difficult to convert into data. We used geometrically microtextured silicon-titanium arrays as a model system. Samples were prepared by deep reactive-ion etching of silicon wafers, resulting in rectangular grooves (width and height: 2 µm) and cubic pillars (pillar dimensions: 2 × 2 × 5 and 5 × 5 × 5 µm); finally sputter-coated with 100 nm titanium. We focused on the morphometric analysis of MG-63 osteoblasts, including a quantification of the actin cytoskeleton. By means of our novel software FilaQuant, especially developed for automatic actin filament recognition, we were first able to quantify the alterations of the actin network dependent on the microtexture of a material surface. The cells’ actin fibers were significantly reduced in length on the pillared surfaces versus the grooved array (4–5 fold) and completely reorganized on the micropillars, but without altering the orientation of cells. Our morpho-functional approach opens new possibilities for the data correlation of cell-material interactions. Full article
(This article belongs to the Special Issue Titanium Materials for Biomedical Application)
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