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Materials, Volume 5, Issue 11 (November 2012), Pages 2015-2438

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Research

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Open AccessArticle Concrete Open-Wall Systems Wrapped with FRP under Torsional Loads
Materials 2012, 5(11), 2055-2068; doi:10.3390/ma5112055
Received: 24 September 2012 / Revised: 18 October 2012 / Accepted: 19 October 2012 / Published: 25 October 2012
Cited by 4 | PDF Full-text (247 KB) | HTML Full-text | XML Full-text
Abstract
The static behavior of reinforced concrete (RC) beams plated with layers of fiber-reinforced composite material (FRP) is widely investigated in current literature, which deals with both its numerical modeling as well as experiments. Scientific interest in this topic is explained by the [...] Read more.
The static behavior of reinforced concrete (RC) beams plated with layers of fiber-reinforced composite material (FRP) is widely investigated in current literature, which deals with both its numerical modeling as well as experiments. Scientific interest in this topic is explained by the increasing widespread use of composite materials in retrofitting techniques, as well as the consolidation and upgrading of existing reinforced concrete elements to new service conditions. The effectiveness of these techniques is typically influenced by the debonding of the FRP at the interface with concrete, where the transfer of stresses occurs from one element (RC member) to the other (FRP strengthening). In fact, the activation of the well-known premature failure modes can be regarded as a consequence of high peak values of the interfacial interactions. Until now, typical applications of FRP structural plating have included cases of flexural or shear-flexural strengthening. Within this context, the present study aims at extending the investigation to the case of wall-systems with open cross-section under torsional loads. It includes the results of some numerical analyses carried out by means of a finite element approximation. Full article
(This article belongs to the Special Issue Innovative Materials in Civil Constructions)
Open AccessArticle A Decolorization Technique with Spent “Greek Coffee” Grounds as Zero-Cost Adsorbents for Industrial Textile Wastewaters
Materials 2012, 5(11), 2069-2087; doi:10.3390/ma5112069
Received: 26 September 2012 / Revised: 19 October 2012 / Accepted: 22 October 2012 / Published: 25 October 2012
Cited by 20 | PDF Full-text (682 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the decolorization of industrial textile wastewaters was studied in batch mode using spent “Greek coffee” grounds (COF) as low-cost adsorbents. In this attempt, there is a cost-saving potential given that there was no further modification of COF (just washed [...] Read more.
In this study, the decolorization of industrial textile wastewaters was studied in batch mode using spent “Greek coffee” grounds (COF) as low-cost adsorbents. In this attempt, there is a cost-saving potential given that there was no further modification of COF (just washed with distilled water to remove dirt and color, then dried in an oven). Furthermore, tests were realized both in synthetic and real textile wastewaters for comparative reasons. The optimum pH of adsorption was acidic (pH = 2) for synthetic effluents, while experiments in free pH (non-adjusted) were carried out for real effluents. Equilibrium data were fitted to the Langmuir, Freundlich and Langmuir-Freundlich (L-F) models. The calculated maximum adsorption capacities (Qmax) for total dye (reactive) removal at 25 °C was 241 mg/g (pH = 2) and 179 mg/g (pH = 10). Thermodynamic parameters were also calculated (ΔH0, ΔG0, ΔS0). Kinetic data were fitted to the pseudo-first, -second and -third order model. The optimum pH for desorption was determined, in line with desorption and reuse analysis. Experiments dealing the increase of mass of adsorbent showed a strong increase in total dye removal. Full article
Open AccessArticle Electronic and Optical Properties of Substitutional and Interstitial Si-Doped ZnO
Materials 2012, 5(11), 2088-2100; doi:10.3390/ma5112088
Received: 9 August 2012 / Revised: 15 October 2012 / Accepted: 23 October 2012 / Published: 29 October 2012
Cited by 16 | PDF Full-text (748 KB) | HTML Full-text | XML Full-text
Abstract
This study investigates the formation energies, electronic structures, and optical properties of pure and Si-doped ZnO using density functional theory and the Hubbard U (DFT + Ud + Up) method. The difference in lattice constants between calculated results and [...] Read more.
This study investigates the formation energies, electronic structures, and optical properties of pure and Si-doped ZnO using density functional theory and the Hubbard U (DFT + Ud + Up) method. The difference in lattice constants between calculated results and experimental measurements is within 1%, and the calculated band gap of pure ZnO is in excellent agreement with experimental values. This study considers three possible Si-doped ZnO structures including the substitution of Si for Zn (Sis(Zn)), interstitial Si in an octahedron (Sii(oct)), and interstitial Si in a tetrahedron (Sii(tet)). Results show that the formation energy of Sis(Zn) defects is the lowest, indicating that Sis(Zn) defects are formed more easily than Sii(oct) and Sii(tet). All three of the Si defect models exhibited n-type conductive characteristics, and except for the Sii(oct) mode the optical band gap expanded beyond that of pure ZnO. In both the Sii(oct) and Sii(tet) models, a heavier effective mass decreased carrier mobility, and deeper donor states significantly decreased transmittance. Therefore, the existence of interestitial Si atoms was bad for the electric and optical properties of ZnO. Full article
(This article belongs to the Special Issue Compound Semiconductor Materials)
Open AccessArticle Creep Behavior of a Sn-Ag-Bi Pb-Free Solder
Materials 2012, 5(11), 2151-2175; doi:10.3390/ma5112151
Received: 28 July 2012 / Revised: 27 September 2012 / Accepted: 18 October 2012 / Published: 2 November 2012
PDF Full-text (1187 KB) | HTML Full-text | XML Full-text
Abstract
Compression creep tests were performed on the ternary 91.84Sn-3.33Ag-4.83Bi (wt.%, abbreviated Sn-Ag-Bi) Pb-free alloy. The test temperatures were: −25 °C, 25 °C, 75 °C, 125 °C, and 160 °C (± 0.5 °C). Four loads were used at the two lowest temperatures and [...] Read more.
Compression creep tests were performed on the ternary 91.84Sn-3.33Ag-4.83Bi (wt.%, abbreviated Sn-Ag-Bi) Pb-free alloy. The test temperatures were: −25 °C, 25 °C, 75 °C, 125 °C, and 160 °C (± 0.5 °C). Four loads were used at the two lowest temperatures and five at the higher temperatures. The specimens were tested in the as-fabricated condition or after having been subjected to one of two air aging conditions: 24 hours at either 125 °C or 150 °C. The strain-time curves exhibited frequent occurrences of negative creep and small-scale fluctuations, particularly at the slower strain rates, that were indicative of dynamic recrystallization (DRX) activity. The source of tertiary creep behavior at faster strain rates was likely to also be DRX rather than a damage accumulation mechanism. Overall, the strain-time curves did not display a consistent trend that could be directly attributed to the aging condition. The sinh law equation satisfactorily represented the minimum strain rate as a function of stress and temperature so as to investigate the deformation rate kinetics: dε/dtmin = Asinhn (ασ) exp (−ΔH/RT). The values of α, n, and  ΔH were in the following ranges (±95% confidence interval): α, 0.010–0.015 (±0.005 1/MPa); n, 2.2–3.1 (±0.5); and ΔH, 54–66 (±8 kJ/mol). The rate kinetics analysis indicated that short-circuit diffusion was a contributing mechanism to dislocation motion during creep. The rate kinetics analysis also determined that a minimum creep rate trend could not be developed between the as-fabricated versus aged conditions. This study showed that the elevated temperature aging treatments introduced multiple changes to the Sn-Ag-Bi microstructure that did not result in a simple loss (“softening”) of its mechanical strength. Full article
(This article belongs to the Special Issue Creep and Fracture of Engineering Materials and Structures)
Open AccessArticle Preparation of Polyaminopyridines Using a CuI/l-Proline-Catalyzed C-N Polycoupling Reaction
Materials 2012, 5(11), 2176-2189; doi:10.3390/ma5112176
Received: 2 August 2012 / Revised: 10 October 2012 / Accepted: 1 November 2012 / Published: 5 November 2012
Cited by 4 | PDF Full-text (294 KB) | HTML Full-text | XML Full-text
Abstract
Polyaminopyridines (PAPy) were chemically prepared from amino-bromopyridines by a CuI/l-proline-catalyzed C-N polycondensation reaction. The formation of the polymer was confirmed by GPC, XRD, XRF, FTIR, UV-vis (λmax = 400 nm), 1H and 13C NMR. The number-average molecular weights ( [...] Read more.
Polyaminopyridines (PAPy) were chemically prepared from amino-bromopyridines by a CuI/l-proline-catalyzed C-N polycondensation reaction. The formation of the polymer was confirmed by GPC, XRD, XRF, FTIR, UV-vis (λmax = 400 nm), 1H and 13C NMR. The number-average molecular weights (Mn) were estimated by end-group analysis using X-ray fluorescence (up to 6000 Da). TGA analysis of PAPy with higher Mn showed greater thermal stability up to 170 oC. Viscosity measurements of polymer in formic acid at 30 oC indicated a polyelectrolyte nature of PAPy solutions. Furthermore, the amorphicity of the material was observed by X-ray diffraction analysis. Full article
(This article belongs to the Special Issue Conjugated Polymers)
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Open AccessArticle Strain Measurements within Fibreboard. Part III: Analyzing the Process Zone at the Crack Tip of Medium Density Fiberboards (MDF) Double Cantilever I-Beam Specimens
Materials 2012, 5(11), 2190-2204; doi:10.3390/ma5112190
Received: 13 September 2012 / Revised: 15 October 2012 / Accepted: 29 October 2012 / Published: 7 November 2012
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Abstract
This paper is the third part of a study dealing with the mechanical and fracture mechanical characterization of Medium Density Fiberboards (MDF). In the first part, an analysis of internal bond strength testing was performed and in the second part MDF was [...] Read more.
This paper is the third part of a study dealing with the mechanical and fracture mechanical characterization of Medium Density Fiberboards (MDF). In the first part, an analysis of internal bond strength testing was performed and in the second part MDF was analyzed by means of the wedge splitting experiment; this part deals with the double cantilever I beam test, which is designed for measuring the fracture energy as well as stress intensity factor in Mode I. For a comparison of isotropic and orthotropic material behavior, finite element modeling was performed. In addition to the calculation of fracture energy the stress intensity factor was analyzed by means of finite elements simulation and calculation. In order to analyze strain deformations and the process zone, electronic speckle pattern interferometry measurements were performed. The results revealed an elongated process zone and lower results for KIC if compared to the wedge splitting experiment. The Gf numbers are higher compared to the wedge splitting results and can be explained by the thicker process zone formed during the crack propagation. The process zone width on its part is influenced by the stiff reinforcements and yields a similar crack surface as with the internal bond test. Full article
(This article belongs to the Special Issue Creep and Fracture of Engineering Materials and Structures)
Open AccessArticle Physisorbed Polymer-Tethered Lipid Bilayer with Lipopolymer Gradient
Materials 2012, 5(11), 2243-2257; doi:10.3390/ma5112243
Received: 15 October 2012 / Revised: 6 November 2012 / Accepted: 6 November 2012 / Published: 8 November 2012
Cited by 7 | PDF Full-text (5963 KB) | HTML Full-text | XML Full-text
Abstract
Physisorbed polymer-tethered lipid bilayers consisting of phospholipids and lipopolymers represent an attractive planar model membrane platform, in which bilayer fluidity and membrane elastic properties can be regulated through lipopolymer molar concentration. Herein we report a method for the fabrication of such a [...] Read more.
Physisorbed polymer-tethered lipid bilayers consisting of phospholipids and lipopolymers represent an attractive planar model membrane platform, in which bilayer fluidity and membrane elastic properties can be regulated through lipopolymer molar concentration. Herein we report a method for the fabrication of such a planar model membrane system with a lateral gradient of lipopolymer density. In addition, a procedure is described, which leads to a sharp boundary between regions of low and high lipopolymer molar concentrations. Resulting gradients and sharp boundaries are visualized on the basis of membrane buckling structures at elevated lipopolymer concentrations using epifluorescence microscopy and atomic force microscopy. Furthermore, results from spot photobleaching experiments are presented, which provide insight into the lipid lateral fluidity in these model membrane architectures. The presented experimental data highlight a planar, solid-supported membrane characterized by fascinating length scale-dependent dynamics and elastic properties with remarkable parallels to those observed in cellular membranes. Full article
(This article belongs to the Special Issue Supported Lipid Membranes)
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Open AccessArticle Copper Substitution and Noise Reduction in Brake Pads: Graphite Type Selection
Materials 2012, 5(11), 2258-2269; doi:10.3390/ma5112258
Received: 24 September 2012 / Revised: 29 October 2012 / Accepted: 5 November 2012 / Published: 9 November 2012
Cited by 8 | PDF Full-text (4260 KB) | HTML Full-text | XML Full-text
Abstract
Graphite is commonly used in brake pads. The use of graphite powder has the main goal of solid state lubrication and friction coefficient stabilization. In this article results on resin bonded brake pads with focus on noise performance and heat dissipation are [...] Read more.
Graphite is commonly used in brake pads. The use of graphite powder has the main goal of solid state lubrication and friction coefficient stabilization. In this article results on resin bonded brake pads with focus on noise performance and heat dissipation are presented. Experimental tests are based on model friction materials with a known formulation and a reduced number of components for a better identification of the role of the graphite type. Results clearly indicate that both noise performance and thermal conductivity are strongly affected by the type of graphite. Guidelines for the selection of graphite types for optimized friction materials are given. Full article
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Open AccessArticle Graphene as a Buffer Layer for Silicon Carbide-on-Insulator Structures
Materials 2012, 5(11), 2270-2279; doi:10.3390/ma5112270
Received: 14 September 2012 / Revised: 4 November 2012 / Accepted: 6 November 2012 / Published: 9 November 2012
Cited by 8 | PDF Full-text (523 KB) | HTML Full-text | XML Full-text
Abstract
We report an innovative technique for growing the silicon carbide-on-insulator (SiCOI) structure by utilizing polycrystalline single layer graphene (SLG) as a buffer layer. The epitaxial growth was carried out using a hot-mesh chemical vapor deposition (HM-CVD) technique. Cubic SiC (3C-SiC) thin film [...] Read more.
We report an innovative technique for growing the silicon carbide-on-insulator (SiCOI) structure by utilizing polycrystalline single layer graphene (SLG) as a buffer layer. The epitaxial growth was carried out using a hot-mesh chemical vapor deposition (HM-CVD) technique. Cubic SiC (3C-SiC) thin film in (111) domain was realized at relatively low substrate temperature of 750 °C. 3C-SiC energy bandgap of 2.2 eV was confirmed. The Si-O absorption band observed in the grown film can be caused by the out-diffusion of the oxygen atom from SiO2 substrate or oxygen doping during the cleaning process. Further experimental works by optimizing the cleaning process, growth parameters of the present growth method, or by using other growth methods, as well, are expected to realize a high quality SiCOI structure, thereby opening up the way for a breakthrough in the development of advanced ULSIs with multifunctionalities. Full article
(This article belongs to the Special Issue Compound Semiconductor Materials)
Open AccessArticle Fatigue Failure Analyses on a Ti-45Al-8Nb-0.2W-0.2B-0.1Y Alloy at Different Temperatures
Materials 2012, 5(11), 2280-2291; doi:10.3390/ma5112280
Received: 27 August 2012 / Revised: 28 October 2012 / Accepted: 1 November 2012 / Published: 9 November 2012
Cited by 2 | PDF Full-text (1946 KB) | HTML Full-text | XML Full-text
Abstract
The fatigue micro crack initiation and propagation tests of a TiAl alloy with 8% Nb content were carried out by using scanning electron microscopy in situ technology at room temperature and at 750 °C. These results indicated that the fatigue micro crack [...] Read more.
The fatigue micro crack initiation and propagation tests of a TiAl alloy with 8% Nb content were carried out by using scanning electron microscopy in situ technology at room temperature and at 750 °C. These results indicated that the fatigue micro crack initiation was mainly caused by the stress concentration at room temperature, but at an elevated temperature (750 °C) the multi-cracks were caused by the coupled factors of both lamellar microstructure and stress concentration. Therefore, fatigue micro crack initiation behavior is much more dependent on the lamellar structure at an elevated temperature. One of the reasons is that the elevated temperature degrades the interface strength between the lamellar of the TiAl alloy with 8% Nb content. Therefore, the small fatigue crack propagation behavior of the alloy exhibited a mixture damage model of interlamellar and translamellar at a micro scale. The crack growth path and fracture characteristics provided a proof of crack deflection, branching and/or bridging induced either by interlamellar or by translamellar failure mode. Full article
Open AccessArticle Cholesterol Organization in Phosphatidylcholine Liposomes: A Surface Plasmon Resonance Study
Materials 2012, 5(11), 2306-2325; doi:10.3390/ma5112306
Received: 29 August 2012 / Revised: 31 October 2012 / Accepted: 2 November 2012 / Published: 13 November 2012
Cited by 5 | PDF Full-text (744 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Models for the organization of sterols into regular arrays within phospholipid bilayers have been proposed previously. The existence of such arrays in real systems has been supported by the fact that concentration-dependent sterol properties show discontinuities at the cholesterol mole fractions corresponding [...] Read more.
Models for the organization of sterols into regular arrays within phospholipid bilayers have been proposed previously. The existence of such arrays in real systems has been supported by the fact that concentration-dependent sterol properties show discontinuities at the cholesterol mole fractions corresponding to regular lattice arrangements. Experimental results presented here are based on a surface plasmon resonance assay that was used to analyze rates of cyclodextrin-mediated removal of cholesterol from adsorbed liposomes at cholesterol mole fractions up to χC = 0.55. Two kinetic pools of cholesterol were detected; there was a fast pool present at χC > 0.25, and a slow pool, with a removal rate that was dependent on the initial χC but that did not vary as χC decreased during the course of one experiment. The cholesterol activity therefore seems to be affected by sample history as well as local concentration, which could be explained in terms of the formation of superlattices that are stable for relatively long times. We also describe a variation on the traditional lattice models, with phosphatidylcholine (PC) being treated as an arrangement of hexagonal tiles; the cholesterol is then introduced at any vertex point, without increasing the total area occupied by all the lipid molecules. This model is consistent with Langmuir trough measurements of total lipid area and provides a simple explanation for the maximum solubility of cholesterol in the PC bilayer. Full article
(This article belongs to the Special Issue Supported Lipid Membranes)
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Open AccessArticle Impact of High Concentration Solutions on Hydraulic Properties of Geosynthetic Clay Liner Materials
Materials 2012, 5(11), 2326-2341; doi:10.3390/ma5112326
Received: 21 August 2012 / Revised: 12 October 2012 / Accepted: 7 November 2012 / Published: 14 November 2012
Cited by 3 | PDF Full-text (186 KB) | HTML Full-text | XML Full-text
Abstract
This study focuses on the impact of landfill high concentration solutions erosion on geosynthetic clay liner (GCL) materials permeability. The permeation tests on the GCL, submerged using different kinds of solutions with different concentrations, were carried out systematically by taking these chemical [...] Read more.
This study focuses on the impact of landfill high concentration solutions erosion on geosynthetic clay liner (GCL) materials permeability. The permeation tests on the GCL, submerged using different kinds of solutions with different concentrations, were carried out systematically by taking these chemical solutions as permeant liquids. Based on seasonal variations of ion concentrations in Chenjiachong landfill leachate (Wuhan Province), CaCl2, MgCl2, NaCl, and KCl were selected as chemical attack solutions to carry out experimental investigations under three concentrations (50 mM, 100 mM, 200 mM) and soak times (5, 10, and 20 days). The variation law of the GCL hydraulic conductivity under different operating conditions was analyzed. The relationship between GCL hydraulic conductivity, chemical solutions categories, concentrations, and soak times were further discussed. The GCL hydraulic conductivity, when soaked and permeated with high concentration chemical solutions, increases several times or exceeds two orders of magnitude, as compared with the permeation test under normal conditions that used water as the permeant liquid. This reveals that GCL is very susceptible to chemical attack. For four chemical solutions, the chemical attack effect on GCL hydraulic conductivity is CaCl2 > MgCl2 > KCl > NaCl. The impact of soak times on GCL hydraulic conductivity is the cooperative contribution of the liner chemical attack reaction and hydration swelling. A longer soak time results in a more advantageous hydration swelling effect. The chemical attack reaction restrains the hydration swelling of the GCL. Moreover, the GCL hydraulic conductivity exponentially decreases with the increased amplitude of thickness. Full article
(This article belongs to the Special Issue Geopolymers and Geopolymeric Materials)
Open AccessArticle Time-Dependent Behavior of Reinforced Polymer Concrete Columns under Eccentric Axial Loading
Materials 2012, 5(11), 2342-2352; doi:10.3390/ma5112342
Received: 17 October 2012 / Revised: 9 November 2012 / Accepted: 14 November 2012 / Published: 16 November 2012
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Abstract
Polymer concretes (PCs) represent a promising alternative to traditional cementitious materials in the field of new construction. In fact, PCs exhibit high compressive strength and ultimate compressive strain values, as well as good chemical resistance. Within the context of these benefits, this [...] Read more.
Polymer concretes (PCs) represent a promising alternative to traditional cementitious materials in the field of new construction. In fact, PCs exhibit high compressive strength and ultimate compressive strain values, as well as good chemical resistance. Within the context of these benefits, this paper presents a study on the time-dependent behavior of polymer concrete columns reinforced with different bar types using a mechanical model recently developed by the authors. Balanced internal reinforcements are considered (i.e., two bars at both the top and bottom of the cross-section). The investigation highlights relevant stress and strain variations over time and, consequently, the emergence of a significant decrease in concrete’s stiffness and strength over time. Therefore, the results indicate that deferred effects due to viscous flow may significantly affect the reliability of reinforced polymer concrete elements over time. Full article
Open AccessArticle Carbon Nanotube Electron Emitter for X-ray Imaging
Materials 2012, 5(11), 2353-2359; doi:10.3390/ma5112353
Received: 21 September 2012 / Revised: 24 October 2012 / Accepted: 12 November 2012 / Published: 16 November 2012
Cited by 6 | PDF Full-text (1303 KB) | HTML Full-text | XML Full-text
Abstract
The carbon nanotube field emitter array was grown on silicon substrate through a resist-assisted patterning (RAP) process. The shape of the carbon nanotube array is elliptical with 2.0 × 0.5 mm2 for an isotropic focal spot size at anode target. The [...] Read more.
The carbon nanotube field emitter array was grown on silicon substrate through a resist-assisted patterning (RAP) process. The shape of the carbon nanotube array is elliptical with 2.0 × 0.5 mm2 for an isotropic focal spot size at anode target. The field emission properties with triode electrodes show a gate turn-on field of 3 V/µm at an anode emission current of 0.1 mA. The author demonstrated the X-ray source with triode electrode structure utilizing the carbon nanotube emitter, and the transmitted X-ray image was of high resolution. Full article
(This article belongs to the Special Issue X-ray Imaging in Materials Science)
Open AccessArticle Wear Behavior of Fiber Laser Textured TiN Coatings in a Heavy Loaded Sliding Regime
Materials 2012, 5(11), 2360-2382; doi:10.3390/ma5112360
Received: 8 October 2012 / Revised: 5 November 2012 / Accepted: 12 November 2012 / Published: 16 November 2012
Cited by 10 | PDF Full-text (3442 KB) | HTML Full-text | XML Full-text
Abstract
In heavy loaded mating components, such as sliders and sliding bearings, guaranteeing the efficiency of lubricant films for long times during severe service conditions is very complicated. In this work, the benefits deriving from the use of fiber laser sources for surface [...] Read more.
In heavy loaded mating components, such as sliders and sliding bearings, guaranteeing the efficiency of lubricant films for long times during severe service conditions is very complicated. In this work, the benefits deriving from the use of fiber laser sources for surface texturing of very thin TiN coatings in severe wear working conditions were demonstrated. Evaluations of the laser textured dimples shape, geometry and density are given. Wear performance of the fiber laser textured surfaces was evaluated in discontinuous oil lubricated conditions with a flat contact. High normal load and low sliding speed were applied. Comparison tests were also performed on commercial TiN and WC/C coatings. In terms of average wear volume and maximum wear depth, Laser Surface Texturing of TiN provided respectively a 70% and a 45% reduction if compared to plain TiN. If compared to WC/C the wear resistance gains were lower but LST TiN maintained such benefits for longer wear runs. SEM analysis also revealed that the laser interaction provided a localized thermal cracking to the TiN coating. However, the sliding action caused very limited and localized coating fragmentation or delamination. Full article
Open AccessArticle Nopal Cactus (Opuntia Ficus-Indica) as a Holographic Material
Materials 2012, 5(11), 2383-2402; doi:10.3390/ma5112383
Received: 21 September 2012 / Revised: 8 October 2012 / Accepted: 23 October 2012 / Published: 20 November 2012
Cited by 5 | PDF Full-text (379 KB) | HTML Full-text | XML Full-text
Abstract
The nopal cactus (Opuntia ficus-indica) releases a substance through its mucilage, which comes from the degradation of pectic substances and chlorophyll. Combined in a polyvinyl alcohol matrix, this substance can be used as a recording medium. The resulting extract material [...] Read more.
The nopal cactus (Opuntia ficus-indica) releases a substance through its mucilage, which comes from the degradation of pectic substances and chlorophyll. Combined in a polyvinyl alcohol matrix, this substance can be used as a recording medium. The resulting extract material has excellent photosensitizer properties, is easy to handle, has a low cost, and low toxicity. This material has the property of self-developing, and it can be used in holographic applications. The polyvinyl alcohol and extract from the nopal cactus was deposited by a gravity technique on a glass substrate, which dried to form a photosensitive emulsion. We show experimental results on a holographic grating using this material, written by a He-Cd laser (442 nm). We obtained diffraction gratings by transmission with a diffraction efficiency of approximately 32.3% to first order. Full article
Open AccessArticle A Novel Active Targeting Preparation, Vinorelbine Tartrate (VLBT) Encapsulated by Folate-Conjugated Bovine Serum Albumin (BSA) Nanoparticles: Preparation, Characterization and in Vitro Release Study
Materials 2012, 5(11), 2403-2422; doi:10.3390/ma5112403
Received: 14 September 2012 / Revised: 5 November 2012 / Accepted: 14 November 2012 / Published: 20 November 2012
Cited by 4 | PDF Full-text (800 KB) | HTML Full-text | XML Full-text
Abstract
Vinorelbine tartrate (VLBT), as a kind of high hydrophilic and temperature-induced degradation drug, was prepared into nanoparticles by a desolvation procedure. Bovine serum albumin (BSA), as a drug carrier, was stabilized by chemical cross-linking with glutaraldehyde. Firstly, the optimization process of preparing [...] Read more.
Vinorelbine tartrate (VLBT), as a kind of high hydrophilic and temperature-induced degradation drug, was prepared into nanoparticles by a desolvation procedure. Bovine serum albumin (BSA), as a drug carrier, was stabilized by chemical cross-linking with glutaraldehyde. Firstly, the optimization process of preparing VLBT-loaded BSA nanoparticles (VLBT-BSANPs) was accomplished using response surface methodology (RSM) by desolvation. Then VLBT-BSANPs were conjugated with folate, namely Fa-BSANPs-VLBT. Hence targeting drug carrier delivery system loading VLBT was produced. In this study, the characteristics of the nanoparticles, such as the amount of folate conjugation, surface morphology, surface chemistry, physical status of VLBT in Fa-BSANPs-VLBT, stability of Fa-BSANPs-VLBT with mannitol and in vitro drug release behavior were all investigated. The VLBT-BSANPs were obtained under optimum conditions, with a mean particle size (MPS) of 155.4 nm and a zeta potential (ZP) of −32.97 mV at a pH value of 5.4. Drug loading efficiency (DLE) and drug entrapment efficiency (DEE) of this obtained drug were approximately 45.6% and 90.6%, respectively. Full article
(This article belongs to the Special Issue Advances in Nanoscale Biomaterials)
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Open AccessArticle Photocatalytic Water Splitting for Hydrogen Production with Novel Y2MSbO7 (M = Ga, In, Gd) under Visible Light Irradiation
Materials 2012, 5(11), 2423-2438; doi:10.3390/ma5112423
Received: 3 September 2012 / Revised: 14 November 2012 / Accepted: 20 November 2012 / Published: 21 November 2012
Cited by 1 | PDF Full-text (248 KB) | HTML Full-text | XML Full-text
Abstract
Novel photocatalysts Y2MSbO7 (M = Ga, In, Gd) were synthesized by the solid state reaction method for the first time. A comparative study on the structural and photocatalytic properties of Y2MSbO7 (M = Ga, In, Gd) [...] Read more.
Novel photocatalysts Y2MSbO7 (M = Ga, In, Gd) were synthesized by the solid state reaction method for the first time. A comparative study on the structural and photocatalytic properties of Y2MSbO7 (M = Ga, In, Gd) was reported. The results showed that Y2GaSbO7, Y2InSbO7 and Y2GdSbO7 crystallized with the pyrochlore-type structure, cubic crystal system, and space group Fd3m. The lattice parameter for Y2GaSbO7 was 10.17981 Å. The lattice parameter for Y2InSbO7 was 10.43213 Å. The lattice parameter for Y2GdSbO7 was 10.50704 Å. The band gap of Y2GaSbO7 was estimated to be 2.245 eV. The band gap of Y2InSbO7 was 2.618 eV. The band gap of Y2GdSbO7 was 2.437 eV. For the photocatalytic water-splitting reaction, H2 or O2 evolution was observed from pure water with Y2GaSbO7, Y2InSbO7 or Y2GdSbO7 as catalyst under visible light irradiation. (Wavelength > 420 nm). Furthermore, H2 and O2 were also evolved by using Y2GaSbO7, Y2InSbO7 or Y2GdSbO7 as a catalyst from CH3OH/H2O and AgNO3/H2O solutions, respectively, under visible light irradiation (λ > 420 nm). Y2GaSbO7 showed the highest activity compared with Y2InSbO7 or Y2GdSbO7. At the same time, Y2InSbO7 showed higher activity compared with Y2GdSbO7. The photocatalytic activities were further improved under visible light irradiation with Y2GaSbO7, Y2InSbO7 or Y2GdSbO7 being loaded by Pt, NiO or RuO2. The effect of Pt was better than that of NiO or RuO2 for improving the photocatalytic activity of Y2GaSbO7, Y2InSbO7 or Y2GdSbO7. Full article
(This article belongs to the Special Issue Advanced Materials for Water-Splitting)

Review

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Open AccessReview Materials-Related Aspects of Thermochemical Water and Carbon Dioxide Splitting: A Review
Materials 2012, 5(11), 2015-2054; doi:10.3390/ma5112015
Received: 3 September 2012 / Revised: 12 October 2012 / Accepted: 17 October 2012 / Published: 24 October 2012
Cited by 36 | PDF Full-text (709 KB) | HTML Full-text | XML Full-text
Abstract
Thermochemical multistep water- and CO2-splitting processes are promising options to face future energy problems. Particularly, the possible incorporation of solar power makes these processes sustainable and environmentally attractive since only water, CO2 and solar power are used; the concentrated [...] Read more.
Thermochemical multistep water- and CO2-splitting processes are promising options to face future energy problems. Particularly, the possible incorporation of solar power makes these processes sustainable and environmentally attractive since only water, CO2 and solar power are used; the concentrated solar energy is converted into storable and transportable fuels. One of the major barriers to technological success is the identification of suitable active materials like catalysts and redox materials exhibiting satisfactory durability, reactivity and efficiencies. Moreover, materials play an important role in the construction of key components and for the implementation in commercial solar plants. The most promising thermochemical water- and CO2-splitting processes are being described and discussed with respect to further development and future potential. The main materials-related challenges of those processes are being analyzed. Technical approaches and development progress in terms of solving them are addressed and assessed in this review. Full article
(This article belongs to the Special Issue Advanced Materials for Water-Splitting)
Open AccessReview Potential Applications of Zeolite Membranes in Reaction Coupling Separation Processes
Materials 2012, 5(11), 2101-2136; doi:10.3390/ma5112101
Received: 26 July 2012 / Revised: 28 August 2012 / Accepted: 13 September 2012 / Published: 30 October 2012
Cited by 11 | PDF Full-text (949 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
Future production of chemicals (e.g., fine and specialty chemicals) in industry is faced with the challenge of limited material and energy resources. However, process intensification might play a significant role in alleviating this problem. A vision of process intensification through multifunctional reactors [...] Read more.
Future production of chemicals (e.g., fine and specialty chemicals) in industry is faced with the challenge of limited material and energy resources. However, process intensification might play a significant role in alleviating this problem. A vision of process intensification through multifunctional reactors has stimulated research on membrane-based reactive separation processes, in which membrane separation and catalytic reaction occur simultaneously in one unit. These processes are rather attractive applications because they are potentially compact, less capital intensive, and have lower processing costs than traditional processes. Therefore this review discusses the progress and potential applications that have occurred in the field of zeolite membrane reactors during the last few years. The aim of this article is to update researchers in the field of process intensification and also provoke their thoughts on further research efforts to explore and exploit the potential applications of zeolite membrane reactors in industry. Further evaluation of this technology for industrial acceptability is essential in this regard. Therefore, studies such as techno-economical feasibility, optimization and scale-up are of the utmost importance. Full article
(This article belongs to the Special Issue Zeolite Membranes: Novel Synthesis and Innovative Applications)
Open AccessReview InN Nanowires: Growth and Optoelectronic Properties
Materials 2012, 5(11), 2137-2150; doi:10.3390/ma5112137
Received: 10 September 2012 / Revised: 12 October 2012 / Accepted: 23 October 2012 / Published: 31 October 2012
Cited by 10 | PDF Full-text (612 KB) | HTML Full-text | XML Full-text
Abstract
An overview on InN nanowires, fabricated using either a catalyst-free molecular beam epitaxy method or a catalyst assisted chemical vapor deposition process, is provided. Differences and similarities of the nanowires prepared using the two techniques are presented. The present understanding of the [...] Read more.
An overview on InN nanowires, fabricated using either a catalyst-free molecular beam epitaxy method or a catalyst assisted chemical vapor deposition process, is provided. Differences and similarities of the nanowires prepared using the two techniques are presented. The present understanding of the growth and of the basic optical and transport properties is discussed. Full article
(This article belongs to the Special Issue Epitaxial Materials)
Open AccessReview Challenges in the Development of Functional Assays of Membrane Proteins
Materials 2012, 5(11), 2205-2242; doi:10.3390/ma5112205
Received: 29 September 2012 / Revised: 25 October 2012 / Accepted: 1 November 2012 / Published: 7 November 2012
Cited by 14 | PDF Full-text (1681 KB) | HTML Full-text | XML Full-text
Abstract
Lipid bilayers are natural barriers of biological cells and cellular compartments. Membrane proteins integrated in biological membranes enable vital cell functions such as signal transduction and the transport of ions or small molecules. In order to determine the activity of a protein [...] Read more.
Lipid bilayers are natural barriers of biological cells and cellular compartments. Membrane proteins integrated in biological membranes enable vital cell functions such as signal transduction and the transport of ions or small molecules. In order to determine the activity of a protein of interest at defined conditions, the membrane protein has to be integrated into artificial lipid bilayers immobilized on a surface. For the fabrication of such biosensors expertise is required in material science, surface and analytical chemistry, molecular biology and biotechnology. Specifically, techniques are needed for structuring surfaces in the micro- and nanometer scale, chemical modification and analysis, lipid bilayer formation, protein expression, purification and solubilization, and most importantly, protein integration into engineered lipid bilayers. Electrochemical and optical methods are suitable to detect membrane activity-related signals. The importance of structural knowledge to understand membrane protein function is obvious. Presently only a few structures of membrane proteins are solved at atomic resolution. Functional assays together with known structures of individual membrane proteins will contribute to a better understanding of vital biological processes occurring at biological membranes. Such assays will be utilized in the discovery of drugs, since membrane proteins are major drug targets. Full article
(This article belongs to the Special Issue Supported Lipid Membranes)
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Open AccessReview Cell-Sized Liposomes and Droplets: Real-World Modeling of Living Cells
Materials 2012, 5(11), 2292-2305; doi:10.3390/ma5112292
Received: 18 October 2012 / Revised: 8 November 2012 / Accepted: 8 November 2012 / Published: 13 November 2012
Cited by 15 | PDF Full-text (878 KB) | HTML Full-text | XML Full-text
Abstract
Recent developments in studies concerning cell-sized vesicles, such as liposomes with a lipid bilayer and water-in-oil droplets covered by a lipid monolayer, aim to realize the real-world modeling of living cells. Compartmentalization with a membrane boundary is essential for the organization of [...] Read more.
Recent developments in studies concerning cell-sized vesicles, such as liposomes with a lipid bilayer and water-in-oil droplets covered by a lipid monolayer, aim to realize the real-world modeling of living cells. Compartmentalization with a membrane boundary is essential for the organization of living systems. Due to the relatively large surface/volume ratio in microconfinement, the membrane interface influences phenomena related to biological functions. In this article, we mainly focus on the following subjects: (i) conformational transition of biopolymers in a confined space; (ii) molecular association on the membrane surface; and (iii) remote control of cell-sized membrane morphology. Full article
(This article belongs to the Special Issue Supported Lipid Membranes)
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