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Materials, Volume 8, Issue 10 (October 2015)

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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; https://doi.org/10.3390/ma8105369
Received: 16 September 2015 / Revised: 14 October 2015 / Accepted: 15 October 2015 / Published: 27 October 2015
Cited by 13 | 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
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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)
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Open AccessArticle Active Nanofibrous Membrane Effects on Gingival Cell Inflammatory Response
Materials 2015, 8(10), 7217-7229; https://doi.org/10.3390/ma8105376
Received: 25 August 2015 / Revised: 8 October 2015 / Accepted: 20 October 2015 / Published: 27 October 2015
Cited by 4 | 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
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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)
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Open AccessArticle Simplified Calculation Model and Experimental Study of Latticed Concrete-Gypsum Composite Panels
Materials 2015, 8(10), 7199-7216; https://doi.org/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
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Open AccessArticle Effects of Electrodes on the Switching Behavior of Strontium Titanate Nickelate Resistive Random Access Memory
Materials 2015, 8(10), 7191-7198; https://doi.org/10.3390/ma8105374
Received: 30 August 2015 / Revised: 11 October 2015 / Accepted: 19 October 2015 / Published: 26 October 2015
Cited by 16 | 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
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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)
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Open AccessArticle Fabrication of Aluminum Tubes Filled with Aluminum Alloy Foam by Friction Welding
Materials 2015, 8(10), 7180-7190; https://doi.org/10.3390/ma8105373
Received: 10 September 2015 / Revised: 8 October 2015 / Accepted: 10 October 2015 / Published: 23 October 2015
Cited by 9 | 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
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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)
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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; https://doi.org/10.3390/ma8105371
Received: 29 May 2015 / Accepted: 10 July 2015 / Published: 22 October 2015
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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
Open AccessArticle Improving Non-Destructive Concrete Strength Tests Using Support Vector Machines
Materials 2015, 8(10), 7169-7178; https://doi.org/10.3390/ma8105368
Received: 27 August 2015 / Revised: 16 September 2015 / Accepted: 13 October 2015 / Published: 22 October 2015
Cited by 5 | 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)
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Open AccessArticle Deformation and Plateau Region of Functionally Graded Aluminum Foam by Amount Combinations of Added Blowing Agent
Materials 2015, 8(10), 7161-7168; https://doi.org/10.3390/ma8105366
Received: 2 August 2015 / Revised: 22 September 2015 / Accepted: 6 October 2015 / Published: 21 October 2015
Cited by 1 | 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)
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Open AccessArticle Fatigue Life Prediction Based on Crack Closure and Equivalent Initial Flaw Size
Materials 2015, 8(10), 7145-7160; https://doi.org/10.3390/ma8105367
Received: 21 August 2015 / Revised: 2 October 2015 / Accepted: 13 October 2015 / Published: 21 October 2015
Cited by 5 | 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
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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; https://doi.org/10.3390/ma8105370
Received: 17 September 2015 / Revised: 13 October 2015 / Accepted: 15 October 2015 / Published: 21 October 2015
Cited by 10 | 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)
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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)
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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; https://doi.org/10.3390/ma8105363
Received: 22 July 2015 / Revised: 18 August 2015 / Accepted: 21 August 2015 / Published: 19 October 2015
Cited by 22 | 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 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; https://doi.org/10.3390/ma8105360
Received: 21 August 2015 / Revised: 2 October 2015 / Accepted: 12 October 2015 / Published: 19 October 2015
Cited by 8 | 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 Numerical Study of the Effects of Residual Stress on Fretting Fatigue Using XFEM
Materials 2015, 8(10), 7094-7105; https://doi.org/10.3390/ma8105365
Received: 10 August 2015 / Revised: 4 October 2015 / Accepted: 9 October 2015 / Published: 19 October 2015
Cited by 2 | PDF Full-text (1162 KB) | HTML Full-text | XML Full-text
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
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Open AccessArticle Single-Crystal Y2O3 Epitaxially on GaAs(001) and (111) Using Atomic Layer Deposition
Materials 2015, 8(10), 7084-7093; https://doi.org/10.3390/ma8105364
Received: 9 August 2015 / Revised: 25 September 2015 / Accepted: 12 October 2015 / Published: 19 October 2015
Cited by 10 | 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)
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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; https://doi.org/10.3390/ma8105361
Received: 29 August 2015 / Revised: 3 October 2015 / Accepted: 8 October 2015 / Published: 19 October 2015
Cited by 1 | PDF Full-text (2525 KB) | HTML Full-text | XML Full-text
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)
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Open AccessArticle Numerical Analysis of the Bending Properties of Cathay Poplar Glulam
Materials 2015, 8(10), 7059-7073; https://doi.org/10.3390/ma8105362
Received: 11 June 2015 / Revised: 24 September 2015 / Accepted: 28 September 2015 / Published: 19 October 2015
Cited by 1 | PDF Full-text (2820 KB) | HTML Full-text | XML Full-text
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)
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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; https://doi.org/10.3390/ma8105359
Received: 2 September 2015 / Revised: 8 October 2015 / Accepted: 9 October 2015 / Published: 16 October 2015
Cited by 5 | 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
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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; https://doi.org/10.3390/ma8105358
Received: 29 August 2015 / Revised: 7 October 2015 / Accepted: 9 October 2015 / Published: 16 October 2015
Cited by 6 | PDF Full-text (1468 KB) | HTML Full-text | XML Full-text
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 Characterization and Curing Kinetics of Epoxy/Silica Nano-Hybrids
Materials 2015, 8(10), 7032-7040; https://doi.org/10.3390/ma8105357
Received: 31 August 2015 / Revised: 2 October 2015 / Accepted: 10 October 2015 / Published: 16 October 2015
Cited by 3 | PDF Full-text (2563 KB) | HTML Full-text | XML Full-text
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 AccessArticle Thermal, Electrical and Surface Hydrophobic Properties of Electrospun Polyacrylonitrile Nanofibers for Structural Health Monitoring
Materials 2015, 8(10), 7017-7031; https://doi.org/10.3390/ma8105356
Received: 24 August 2015 / Revised: 16 September 2015 / Accepted: 30 September 2015 / Published: 14 October 2015
Cited by 20 | PDF Full-text (4271 KB) | HTML Full-text | XML Full-text
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)
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Open AccessArticle Fabrication of Microdots Using Piezoelectric Dispensing Technique for Viscous Fluids
Materials 2015, 8(10), 7006-7016; https://doi.org/10.3390/ma8105355
Received: 30 July 2015 / Revised: 22 September 2015 / Accepted: 8 October 2015 / Published: 14 October 2015
Cited by 2 | PDF Full-text (3022 KB) | HTML Full-text | XML Full-text
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 Energy Materials)
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Open AccessArticle The Promotion Strategy of Green Construction Materials: A Path Analysis Approach
Materials 2015, 8(10), 6999-7005; https://doi.org/10.3390/ma8105354
Received: 4 August 2015 / Revised: 22 September 2015 / Accepted: 28 September 2015 / Published: 14 October 2015
Cited by 1 | PDF Full-text (612 KB) | HTML Full-text | XML Full-text
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)
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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; https://doi.org/10.3390/ma8105348
Received: 7 August 2015 / Revised: 19 September 2015 / Accepted: 28 September 2015 / Published: 13 October 2015
Cited by 9 | 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)
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Open AccessArticle Engineering Behavior and Characteristics of Wood Ash and Sugarcane Bagasse Ash
Materials 2015, 8(10), 6962-6977; https://doi.org/10.3390/ma8105353
Received: 7 August 2015 / Revised: 16 September 2015 / Accepted: 28 September 2015 / Published: 12 October 2015
Cited by 8 | PDF Full-text (6379 KB) | HTML Full-text | XML Full-text
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 Energy Materials)
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Open AccessArticle Investigation of Key Parameters of Rock Cracking Using the Expansion of Vermiculite Materia
Materials 2015, 8(10), 6950-6961; https://doi.org/10.3390/ma8105351
Received: 15 July 2015 / Revised: 13 September 2015 / Accepted: 28 September 2015 / Published: 12 October 2015
Cited by 3 | PDF Full-text (5557 KB) | HTML Full-text | XML Full-text
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
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Open AccessArticle Controlled Emissivity Coatings to Delay Ignition of Polyethylene
Materials 2015, 8(10), 6935-6949; https://doi.org/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
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Open AccessArticle Low-Temperature Solution-Processed Gate Dielectrics for High-Performance Organic Thin Film Transistors
Materials 2015, 8(10), 6926-6934; https://doi.org/10.3390/ma8105352
Received: 27 August 2015 / Revised: 23 September 2015 / Accepted: 8 October 2015 / Published: 12 October 2015
Cited by 6 | PDF Full-text (3639 KB) | HTML Full-text | XML Full-text
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
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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; https://doi.org/10.3390/ma8105347
Received: 11 September 2015 / Revised: 25 September 2015 / Accepted: 7 October 2015 / Published: 12 October 2015
Cited by 9 | PDF Full-text (2041 KB) | HTML Full-text | XML Full-text
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)
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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; https://doi.org/10.3390/ma8105345
Received: 19 August 2015 / Accepted: 28 September 2015 / Published: 10 October 2015
Cited by 2 | PDF Full-text (5113 KB) | HTML Full-text | XML Full-text
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
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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; https://doi.org/10.3390/ma8105350
Received: 18 August 2015 / Accepted: 15 September 2015 / Published: 10 October 2015
Cited by 2 | PDF Full-text (6372 KB) | HTML Full-text | XML Full-text
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
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