Advances in Materials Science and Engineering The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Preparation and Sintering Effect in Quartz-Barium Titanate Porous Ceramics and Permeability Modulation Using an Implanted Electrode Wed, 16 Apr 2014 11:10:46 +0000 Barium titanate and quartz mixed in different proportions were used to create porous piezoelectric ceramics. Three different sintering temperatures were used for the ceramics preparation; a nichrome wire was used as internal electrode in porous ceramics. Characteristics as porous area, porosity, and its relationship with quartz percentage and sintering temperatures were studied. Porous ceramics with an implanted electrode were created, by applying an alternating voltage in the internal electrode that controlled the liquid permeability coefficient, calculated by the Darcy Law. Ernesto Suaste Gómez, José de Jesús Agustín Flores Cuautle, and Omar Terán Jiménez Copyright © 2014 Ernesto Suaste Gómez et al. All rights reserved. A Review of the Flammability Factors of Kenaf and Allied Fibre Reinforced Polymer Composites Tue, 15 Apr 2014 14:05:38 +0000 Natural fibre is a well-known reinforcement fibre in polymer-matrix Composites (PMC) lately. Natural fibre has fast growing and abundance properties which make it available at very low cost. For kenaf fibre there is long lists of research projects which have been done regarding its behaviour, and properties and modification made to it. In this paper, fire flammability is the main concern for natural fibre reinforced polymer (NFRP) composites especially kenaf fibre. To estimate its flammability, a wide range of factors can be considered such as fibre content, type of matrices, pH conditions, treatment, and fire retardant (FR) filler’s type. The most important criteria are the ignition time, rate of propagation, and fire behavior. thermogravimetric analysis (TGA), different scanning calorimetric (DSC), and dynamic mechanical analysis (DMA) are the three most famous methods used to investigate the fire behaviour of composites. C. H. Lee, Mohd Sapuan Salit, and M. R. Hassan Copyright © 2014 C. H. Lee et al. All rights reserved. Effect of W/C Ratio on Durability and Porosity in Cement Mortar with Constant Cement Amount Tue, 15 Apr 2014 11:43:14 +0000 Water is often added to concrete placing for easy workability and finishability in construction site. The additional mixing water can help easy mixing and workability but causes increased porosity, which yields degradation of durability and structural performances. In this paper, cement mortar samples with 0.45 of W/C (water to cement) ratio are prepared for control case and durability performances are evaluated with additional water from 0.45 to 0.60 of W/C. Several durability tests including strength, chloride diffusion, air permeability, saturation, and moisture diffusion are performed, and they are analyzed with changed porosity. The changing ratios and patterns of durability performance are evaluated considering pore size distribution, total porosity, and additional water content. Yun-Yong Kim, Kwang-Myung Lee, Jin-Wook Bang, and Seung-Jun Kwon Copyright © 2014 Yun-Yong Kim et al. All rights reserved. Enzyme-Free Electrochemical Glucose Sensors Prepared by Dealloying Pd-Ni-P Metallic Glasses Tue, 15 Apr 2014 11:41:59 +0000 We report the formation of enzyme-free electrochemical glucose sensors by electrochemical dealloying palladium-containing Pd-Ni-P metallic glasses. When metallic glasses with different Pd contents are used as the dealloying precursor alloys, palladium-based nanoporous metals with different ligament and pore sizes can be obtained. The chemical compositions of the nanoporous metals also vary according to the different precursor compositions. All the as-obtained nanoporous metals exhibit electrochemical catalytic activity towards the oxidation of d-glucose, indicating that the nanoporous metals prepared by dealloying the Pd-Ni-P metallic glasses are promising materials for enzyme-free electrochemical glucose sensor. Yuqiao Zeng, Hua Xiang, Chunlei Yang, Shengchen Yang, Luyang Chen, Mingwei Chen, Akihisa Inoue, Xuhai Zhang, and Jianqing Jiang Copyright © 2014 Yuqiao Zeng et al. All rights reserved. Mesostructural Design and Manufacturing of Open-Pore Metal Foams by Investment Casting Tue, 15 Apr 2014 06:46:22 +0000 The present paper describes the manufacturing process of open-pore metal foams by investment casting and the mesostructural/morphological evolution resulting from a new technique of modifying the precursor. By this technique, the precursor is coated with a polymer layer whereby a thickening of the struts occurs. Relative densities in the range of of open-pore metal foams can be achieved with high accuracy. The samples investigated have pore densities of  ppi, 10 ppi, and 13 ppi. The relevant processing parameters needed for a homogenous formation of the polymer layer are determined for two different coating materials and the resulting open-pore foam’s mesostructure is characterized qualitatively and quantitatively. The alloy used for investment casting open-pore metal foamsis AlZn11. The microstructural evolution of these foams is evaluated as a function of the mesostructure. Differences in the microstructure are observed for foams with low and high relative densities and discussed in terms of cooling subsequent to investment casting. Alexander Martin Matz, Bettina Stefanie Mocker, Daniel Wyn Müller, Norbert Jost, and Gunther Eggeler Copyright © 2014 Alexander Martin Matz et al. All rights reserved. Advances in Smart Materials and Applications Tue, 15 Apr 2014 00:00:00 +0000 Kuan Yew Cheong, Kean Aw, Khasan S. Karimov, Feng Zhao, Mohammad Mahroof-Tahir, and Rupert Schreiner Copyright © 2014 Kuan Yew Cheong et al. All rights reserved. Fabrication of Ni-Mn Microprobe Structure with Low Internal Stress and High Hardness by Employing DC Electrodeposition Tue, 15 Apr 2014 00:00:00 +0000 Due to its widely tunable mechanical property and incompatibility with most solders, Ni-Mn alloy can become a viable candidate in the fabrication of testing probe for microelectronic devices. In this study, the electrodeposition of Ni-Mn alloy in nickel sulphamate electrolyte with the addition of manganese sulphate was investigated under direct current (DC) power source. The effects of current density and Mn2+ concentration in the electrolyte on the coating composition, cathodic efficiency, microstructure and mechanical properties were explored. The results showed that the raise of the Mn2+ concentration in the electrolyte alone did not effectively increase the Mn content in the coating but reduce the cathodic efficiency. On the other hand, increasing the current density facilitated the codeposition of the Mn and rendered the crystallite from coarse columnar grain to the refined one. Thus, both hardness and internal stress of the coating increased. The fabrication of testing probes at 1 A/dm2 was shown to satisfy the high hardness, low internal stress, reasonable fatigue life, and nonsticking requirements for this microelectronic application. Kuan-Hui Cheng, Fu-Je Chen, Chun-Ying Lee, Chao-Sung Lin, Jung-Tang Huang, Chang-Cheng Lan, Ping-Huan Tsou, and Tzu-I Ho Copyright © 2014 Kuan-Hui Cheng et al. All rights reserved. Structural Characterization of Silica Particles Extracted from Grass Stenotaphrum secundatum: Biotransformation via Annelids Mon, 14 Apr 2014 13:56:02 +0000 This study shows the structural characterization of silica particles extracted from Stenotaphrum secundatum (St. Augustine) grass using an annelid-based biotransformation process. This bioprocess starts when St. Augustine grass is turned into humus by vermicompost, and then goes through calcination and acid treatment to obtain silica particles. To determine the effect of the bioprocess, silica particles without biotransformation were extracted directly from the sample of grass. The characterization of the silica particles was performed using Infrared (FTIR) and Raman spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Dynamic Light Scattering (DLS), and Energy Dispersion Spectroscopy (EDS). Both types of particles showed differences in morphology and size. The particles without biotransformation were essentially amorphous while those obtained via annelids showed specific crystalline phases. The biological relationship between the metabolisms of worms and microorganisms and the organic-mineral matter causes changes to the particles' properties. The results of this study are important because they will allow synthesis of silica in cheaper and more ecofriendly ways. A. Espíndola-Gonzalez, R. Fuentes-Ramirez, A. L. Martínez-Hernández, V. M. Castaño, and C. Velasco-Santos Copyright © 2014 A. Espíndola-Gonzalez et al. All rights reserved. Tensile Testing with Cyclic Strain Holding to Analyze Dynamic Recrystallization of Pure Lead Mon, 14 Apr 2014 08:23:04 +0000 We analyzed the dynamic recrystallization of pure lead by tensile testing with cyclic strain holding at room temperature. The specimens were held at an identical strain and subsequently reloaded, providing the strength before and after the strain holding process. The difference in strength enables factors affecting dynamic recrystallization behavior to be analyzed through mechanical testing. For instance, the effects of strain rate on dynamic recrystallization were analyzed by comparing the results obtained from tensile tests with and without strain holding. This experimental technique demonstrated some parts of contribution of elastic strain, dynamic recovery, dynamic recrystallization, and necking to stress-strain responses. Mayu Muramatsu, Motomichi Koyama, and Ikumu Watanabe Copyright © 2014 Mayu Muramatsu et al. All rights reserved. Microstructural and Dielectric Properties of Zr Doped Microwave Sintered Synthesized by Sol-Gel Route Sun, 13 Apr 2014 00:00:00 +0000 Polycrystalline samples with the chemical formula CaCu3O12 (, 0.02, 0.1, 0.2, 0.5, and 0.1) CCTZO were synthesized from metal nitrate solutions by the sol-gel method, followed by conventional and microwave heat treatments. The X-ray diffraction pattern of powder calcined at 800°C in conventional furnace for 3 h showed formation of a single phase. The crystal structure did not change on doping with zirconium and it remained cubic in the five studied compositions. The surface morphology of samples sintered at 1000°C in microwave furnace for 10 min was observed using a high resolution scanning electron microscope (HR-SEM). The grain sizes were in the range of 250 nm–5 μm for these samples. HRSEM results show that doping with Zr enhanced grain growth or densification. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of Zr. The dielectric characteristics of Zr doped CCTO were studied with an LCR meter in the frequency range of 50 Hz–1 MHz. A very high dielectric constant 21,500 was observed for the sample doped with Zr (0.02 mol%) at 50 Hz. S. Jesurani, S. Kanagesan, M. Hashim, I. Ismail, and I. R. Ibrahim Copyright © 2014 S. Jesurani et al. All rights reserved. Evaluation of Relationship between Water Absorption and Durability of Concrete Materials Thu, 10 Apr 2014 08:51:55 +0000 Environment has significant effects on the water absorption of concrete materials. This paper presents an experimental study of the influence of water absorption on the durability of concrete materials. A detailed analysis is also presented in order to establish useful relationship between them. Concrete specimens of different water absorption were prepared through different curing conditions, and results indicated that curing condition can significantly affect the surface water absorption. SEM photos also showed that different curing conditions caused different microstructure. After 28-days curing, compressive strength, permeability, sulfate attack, and chloride ion diffusion of concrete samples were investigated. As a result, both of surface sorptivity and internal sorptivity have no clear relationship with compressive strength. Results obtained also showed that only surface water absorption related to the performance of concrete including permeability, sulfate attack, and chloride ion diffusion. In addition, both impermeability and resistance to sulfate attack were linearly associated with surface sorptivity, and both correlation coefficients were not less than 0.9. Furthermore, chloride ion diffusion coefficient has exponent relation to surface water absorption with higher correlation coefficient. However, no apparent relationship was found between internal water absorption and durability like impermeability, resistance to sulfate attack, and chloride ion diffusion. S. P. Zhang and L. Zong Copyright © 2014 S. P. Zhang and L. Zong. All rights reserved. Thin Film Applications in Advanced Electron Devices Thu, 10 Apr 2014 07:45:11 +0000 Fu-Chien Chiu, Tung-Ming Pan, Tapas Kumar Kundu, and Chun-Hsing Shih Copyright © 2014 Fu-Chien Chiu et al. All rights reserved. Numerical Analysis of the Energy Improvement of Plastering Mortars with Phase Change Materials Thu, 10 Apr 2014 07:19:46 +0000 Building components with incorporated phase change materials (PCMs) meant to increase heat storage capacity and enable stabilization of interior buildings surface temperatures, whereby influencing the thermal comfort sensation and the stabilization of the interior ambient temperatures. The potential of advanced simulation tools to evaluate and optimize the usage of PCM in the control of indoor temperature, allowing for an improvement in the comfort conditions and/or in the cooling energy demand, was explored. This paper presents a numerical and sensitivity analysis of the enthalpy and melting temperature effect on the inside building comfort sensation potential of the plastering PCM. A. Váz Sá, R. M. S. F. Almeida, H. Sousa, and J. M. P. Q. Delgado Copyright © 2014 A. Váz Sá et al. All rights reserved. Effects of CFRP Strengthening on Dynamic and Fatigue Responses of Composite Bridge Mon, 07 Apr 2014 14:02:14 +0000 This paper investigates the effect of CFRP strengthening on dynamic and fatigue responses of composite bridge using finite element program ABAQUS. Dynamic and fatigue responses of composite bridge due to truck load based on AASHTO standard are investigated. Two types of CFRP strengthening techniques, CFRP sheets and CFRP deck, are applied to both the damaged and undamaged bridges. For the case of damaged bridge, two through-thickness crack sizes, 3 mm and 6 mm in depth, are assumed at midspan of the steel girders. Furthermore, effects of the number of steel girders on the dynamic and fatigue responses are also considered. The results show that the maximum responses of composite bridges occur for dual lane cases. By using CFRP as a strengthening material, the maximum stress and deflection of the steel girders reduce and consequently increase the fatigue life of the girders. After introducing initial crack into the steel girders of the composite bridges, the fatigue life of the bridges is dramatically reduced. However, the overall performance of the damaged composite bridge can be improved by using CFRP, albeit with less effectiveness. Therefore, if cracks are found, steel welding must be performed before strengthening the composite bridge by CFRP. Kittisak Kuntiyawichai and Suchart Limkatanyu Copyright © 2014 Kittisak Kuntiyawichai and Suchart Limkatanyu. All rights reserved. Metal-Containing Ionic Liquids: Highly Effective Catalysts for Degradation of Poly(Ethylene Terephthalate) Mon, 07 Apr 2014 13:47:46 +0000 Poly(ethylene terephthalate) (PET) waste from local market was depolymerized by ethylene glycol (EG) in the presence of metal-containing ionic liquids, and the qualitative analysis showed that the bis(hydroxyethyl) terephthalate (BHET) was the main product in this process. Compared with other metal-containing ionic liquids, [Bmim]ZnCl3 was considered the best catalyst in the glycolysis of PET. When the reaction temperature was 180°C, the conversion of PET reached 97.9% and the BHET was yielded to 83.3% within 5 h. At the same time, [Bmim]ZnCl3 could be reused for six times without obvious decrease in the yield of BHET. Additional, the effects of waste PET’s source and size were investigated. Qun Feng Yue, Hua Guang Yang, Mi Lin Zhang, and Xue Feng Bai Copyright © 2014 Qun Feng Yue et al. All rights reserved. Fatigue Properties of Layered Double Hydroxides Modified Asphalt and Its Mixture Mon, 07 Apr 2014 09:21:18 +0000 This study investigated the influence of layered double hydroxides (LDHs) on the fatigue properties of asphalt mixture. In this paper, different aging levels (thin film oven test (TFOT) and ultraviolet radiation aging (UV aging for short)) of bitumen modified with various mass ratios of the LDHs were investigated. The TFOT and UV aging process were used to simulate short-term field thermal-oxidative aging and long-term field light UV aging of bitumen, respectively. The influences of LDHs on the fatigue properties of LDHs were evaluated by dynamic shear rheometer (DSR) and indirect tensile fatigue test. Results indicated that the introduction of LDHs could change the fatigue properties of bitumen under a stress control mode. The mixture with modified bitumen showed better fatigue resistance than the mixture with base bitumen. The results illustrated that the LDHs would be alternative modifiers used in the bitumen to improve the lifetime of asphalt pavements. Xing Liu, Shaopeng Wu, Ling Pang, Yue Xiao, and Pan Pan Copyright © 2014 Xing Liu et al. All rights reserved. Molecular Imprinting for High-Added Value Metals: An Overview of Recent Environmental Applications Mon, 07 Apr 2014 06:33:53 +0000 One of the most hot topics of recent research is the reuse of some compounds existing as pollutants in environment. These compounds (molecules, ions, complexes, etc.) are of high-added value and it will be ideal to selectively bind them with any environmental application and reuse them in their initial or modified form. The latter can be achieved using molecular imprinting. In the present review article, an overview of the recent attempts for the selective binding of some precious metals (i.e., gold, silver, and platinum) of high-added value is done using molecular imprinted polymers (MIPs) as materials. The simplicity of their use, their relatively low cost, and the broad range of possible guest molecules (small organic molecules, ions, metals, and also biological macromolecules) have since led to the important development of molecular imprinting. George Z. Kyzas and Dimitrios N. Bikiaris Copyright © 2014 George Z. Kyzas and Dimitrios N. Bikiaris. All rights reserved. Improvement of Homogeneity and Aspect Ratio of Silicon Tips for Field Emission by Reactive-Ion Etching Sun, 06 Apr 2014 12:27:01 +0000 The homogeneity of emitters is very important for the performance of field emission (FE) devices. Reactive-ion etching (RIE) and oxidation have significant influences on the geometry of silicon tips. The RIE influences mainly the anisotropy of the emitters. Pressure has a strong impact on the anisotropic factor. Reducing the pressure results in a higher anisotropy, but the etch rate is also lower. A longer time of etching compensates this effect. Furthermore an improvement of homogeneity was observed. The impact of uprating is quite low for the anisotropic factor, but significant for the homogeneity. At low power the height and undercut of the emitters are more constant over the whole wafer. The oxidation itself is very homogeneous and has no observable effect on further variation of the homogeneity. This modified fabrication process allows solving the problem of inhomogeneity of previous field emission arrays. Robert Damian Lawrowski, Christian Prommesberger, Christoph Langer, Florian Dams, and Rupert Schreiner Copyright © 2014 Robert Damian Lawrowski et al. All rights reserved. Computational and Simulation Analysis of Pull-Out Fiber Reinforced Concrete Thu, 03 Apr 2014 14:19:44 +0000 The computational and simulation analysis of pull-out fiber reinforced concrete was investigated. The finite element analysis was used to make this modeling and analysis on this reinforced system and three parts (concrete matrix, the placed fiber reinforcement polymers (FRP), and resin layer) were studied. A constant load was directly applied on the free end of placed FRP and the deformation, von Mises stress, displacement, and strain of these three analyzed parts were obtained. Meanwhile, the specimen system of bonding strength and strain was calculated by the method of ABAQUS. The results showed that, with the constant load, the von Mises stress, deformation, and strain appeared in these three parts, and the maximum values in both FRP and resin layer were shown at the free end side, which provides an accurate description of the rupture mode. Xia Zhao, Xiong-Jun He, Sheng Yan, and Nguyen Phan Anh Copyright © 2014 Xia Zhao et al. All rights reserved. Effect of Laser Welding Parameters on Formation of NiTi Shape Memory Alloy Welds Thu, 03 Apr 2014 09:37:54 +0000 In this work experimental trials of welding of NiTi flat plates with 2.0 mm thickness were conducted using a 4.5 kW continuous wave (CW) Nd:YAG laser. The influences of laser output power, welding speed, defocus amount and side-blow shielding gas flow rate on the morphology, welding depth and width, and quality of the welded seam were investigated. Meanwhile, the effects of heat input on the mechanical and functional properties of welded joints were studied. The results show that laser welding can take better formation in NiTi alloys. The matching curves with laser power and welding speed affecting different formation of welds were experimentally acquired, which can provide references for laser welding and engineering application of NiTi alloy. The heat input has obvious effects on the ultimate tensile strength (UTS) and shape memory behavior of the welded joints. Wei Wang, Xiaohong Yang, Hongguang Li, Fuzhong Cong, and Yongbing Liu Copyright © 2014 Wei Wang et al. All rights reserved. Effect of Material Thickness on Attenuation (dB) of PTFE Using Finite Element Method at X-Band Frequency Thu, 03 Apr 2014 07:45:53 +0000 PTFE samples were prepared with different thicknesses. Their electric field intensity and distribution of the PTFE samples placed inside a rectangular waveguide were simulated using finite element method. The calculation of transmission/reflection coefficients for all samples thickness was achieved via FEM. Amongst other observable features, result from calculation using FEM showed that the attenuation for the 15 mm PTFE sample is −3.32 dB; the 30 mm thick PTFE sample has an attenuation of 0.64 dB, while the 50 mm thick PTFE sample has an attenuation of 1.97 dB. It then suffices to say that, as the thickness of the PTFE sample increases, the attenuation of the samples at the corresponding thicknesses increases. Abubakar Yakubu, Zulkifly Abbas, and Mansor Hashim Copyright © 2014 Abubakar Yakubu et al. All rights reserved. The Role of Foaming Agent and Processing Route in Mechanical Performance of Fabricated Aluminum Foams Mon, 31 Mar 2014 13:45:44 +0000 The results of this study highlight the role of foaming agent and processing route in influencing the contamination of cell wall material by side products, which, in turn, affects the macroscopic mechanical response of closed-cell Al-foams. Several kinds of Al-foams have been produced with pure Al/Al-alloys by the Alporas like melt process, all performed with and without Ca additive and processed either with conventional TiH2 foaming agent or CaCO3 as an alternative one. Damage behavior of contaminations was believed to affect the micromechanism of foam deformation, favoring either plastic buckling or brittle failure of cell walls. No discrepancy between experimental values of compressive strengths for Al-foams comprising ductile cell wall constituents and those prescribed by theoretical models for closed-cell structure was found while the presence of low ductile and/or brittle eutectic domains and contaminations including particles/layers of Al3Ti, residues of partially reacted TiH2, and Ca bearing compounds, results in reducing the compressive strength to values close to or even below those of open-cell foams of the same relative density. Alexandra Byakova, Iegor Kartuzov, Svyatoslav Gnyloskurenko, and Takashi Nakamura Copyright © 2014 Alexandra Byakova et al. All rights reserved. Spontaneous Emission of an Excited Atom in a Dusty Unmagnetized Plasma Medium Mon, 31 Mar 2014 08:02:57 +0000 Investigation of spontaneous decay of an excited atom in dusty unmagnetized plasma is presented in this paper. The transverse contribution to the decay rate is normally associated with spontaneous emission. The rate of spontaneous emission can be obtained by Fermi’s golden rule. In this calculation, the transverse contribution to dielectric permittivity and Green function technique are used. Calculation of the decay rate of atoms is applicable to understand the particular structure of the vacuum state of the electromagnetic field. Naser Alinejad and Noushin Pishbin Copyright © 2014 Naser Alinejad and Noushin Pishbin. All rights reserved. Effect of Fly Ash on Mortar Mixes with Quarry Dust as Fine Aggregate Thu, 27 Mar 2014 11:16:44 +0000 This paper presents the results of an experimental investigation carried out to evaluate the compressive strength and transverse strength of 1 : 3 mortar mixes in which natural sand was replaced with 20%, 50%, and 100% quarry dust by weight which were further modified by partially replacing cement with four percentages (15%, 20%, 25%, and 30%) of low calcium fly ash. The compressive strength was determined at 3, 7, 28, and 50 days of age while transverse strength was determined at 28 and 50 days age. Test results revealed that the combined use of quarry rock dust and fly ash exhibited excellent performance due to efficient microfilling ability and pozzolanic activity. Baboo Rai, Sanjay Kumar, and Kumar Satish Copyright © 2014 Baboo Rai et al. All rights reserved. Synthesis and Characterization of SiO2 Nanoparticles and Their Efficacy in Chemical Mechanical Polishing Steel Substrate Thu, 27 Mar 2014 07:59:37 +0000 Chemical mechanical polishing (CMP) technology is extensively used in the global planarization of highly value-added and large components in the aerospace industry. A nanopowder of SiO2 was prepared by the sol-gel method and was compounded into polishing slurry for the CMP of steel substrate. The size of the SiO2 abrasives was controlled by varying the sol-gel reaction conditions. The polishing efficacy of nano-SiO2 was studied, and the CMP mechanism with nanosized abrasives was further investigated. The proposed methods can produce SiO2 abrasives whose size can be controlled by varying the sol-gel reaction conditions. The size of the SiO2 abrasives was controlled in the range from 58 to 684 nm. The roughness of the steel substrate strongly depends on the size of the abrasive, and the surface roughness decreases as the abrasive size declines. A super-smooth surface with a roughness of 8.4 nm is obtained with nanosized SiO2. Ideal CMP slurry can be used to produce material surfaces with low roughness, excellent global planarization, high selectivity, an excellent finish, and a low-defected rate. M. J. Kao, F. C. Hsu, and D. X. Peng Copyright © 2014 M. J. Kao et al. All rights reserved. Narrowband, Visible-Blind UV-A Sensor Based on a Film Deposited by Radio-Frequency Sputtering Using a ZnO-Mg Composite Target Wed, 26 Mar 2014 09:51:53 +0000 A narrowband, visible-blind ultraviolet photodetector (PD) for UV-A is fabricated using a Mg0.52Zn0.48O film that is formed on a quartz substrate by a radio-frequency sputtering technique using a ZnO-Mg composite target. The content of Mg in the film is controlled by varying the number of Mg chips on the ZnO plate. The fabricated PD has a metal-semiconductor-metal structure with interdigitated electrodes and exhibits a narrow 3 dB bandwidth of 26 nm with a peak response wavelength of 340 nm and a cut-off wavelength of 353 nm. Moreover, the peak responsivity of the PD increases linearly with the bias voltage up to 30 V, indicating that the device operates via a photoconductive gain mechanism. Yuki Kohama, Takuya Nagai, Mitsuru Inada, and Tadashi Saitoh Copyright © 2014 Yuki Kohama et al. All rights reserved. Tunable Nanodielectric Composites Tue, 25 Mar 2014 10:07:57 +0000 This paper presents a progress update with the development of nanodielectric composites with electric field tunability for various high energy, high power electrical applications. It is demonstrated that nonlinear electrical/dielectric properties can be achieved via the nanostructure and interface engineering. A high level summary was given on the progress achieved as well as challenges remaining in nanodielectric engineering towards high energy density capacitors for energy storage and conversion, nonlinear dielectrics for tunable device, and high voltage varistor for surge suppression. Daniel Qi Tan, Yang Cao, Xiaomei Fang, and Patricia C. Irwin Copyright © 2014 Daniel Qi Tan et al. All rights reserved. A New Solution for the Compression of a Two-Layer Strip and Its Application to Analysis of Bonding by Rolling Tue, 25 Mar 2014 07:37:21 +0000 The paper presents a theoretical study on the compression of a two-layer strip of strain-hardening rigid-plastic materials between rigid platens. Semianalytical solutions are obtained for stress and velocity fields in each layer. Special attention is devoted to the conditions corresponding to the beginning of cold bond formation between the layers. Depending on input parameters various general deformation patterns are possible. In particular, there exists such a range of process parameters that the soft metal layer yields while the hard metal layer is rigid at the beginning of the process. As the deformation proceeds, yielding also starts in the hard metal layer and the entire strip becomes plastic. This is a typical deformation pattern adopted in describing the process of joining by rolling. However, at a certain range of input parameters plastic deformation of the entire strip begins at the initial instant. Moreover, it is possible that only the hard metal layer yields while the soft metal layer does not. This deformation pattern takes place when the thickness of the soft metal layer is much smaller than that of the hard metal layer. Sergei Alexandrov and Yusof Mustafa Copyright © 2014 Sergei Alexandrov and Yusof Mustafa. All rights reserved. Simulation of Hydraulic Fracture in Unsaturated Soils with High Degree of Saturation Thu, 20 Mar 2014 17:50:26 +0000 A numerical simulation approach of hydraulic fracture process, considering the couplings of the stress distribution, the fluid flow of the water-air mixture, the compression and dissolution of air, and the element damage evolution, has been developed to investigate the mechanisms of crack initiation and propagation in porous media during hydraulic fracturing. The concept of homogenized pore fluid has been adopted to represent the water air mixture. A large number of numerical analysis on hydraulic fracturing in clay with incipient injection slot have been carried out to study the mechanism of hydraulic fracturing in unsaturated soil with the characteristic of critical model I type of crack loading using stress intensity factor . The results provide a numerical picture depicting the mechanisms of crack initiation and propagation during hydraulic fracturing. The numerical results are in good agreement with the experimental results, which confirms the adequacy and the power of the numerical approach. Tielin Chen, Liangyi Zhang, and Dingli Zhang Copyright © 2014 Tielin Chen et al. All rights reserved. Influence of Surface Modification of Alumina on Improvement of Wetability in Aluminium Matrix Composite Wed, 19 Mar 2014 11:33:25 +0000 In this research, aluminium powder (50 wt%) and alumina (50 wt%) were first milled at a specific ball-to-powder ratio in a high-energy planetary mill at different times to manufacture Al-Al2O3 composite. Then, the capsules of powdery composites (Al-Al2O3)CP produced at the milling stage were added to aluminium melt and cast through ex situ. Scanning electron microscope SEM was used to study the morphology of the capsules and the microstructure of the produced composite. The percentage of powdery composite capsules and reinforcing particles present in the microstructure of Al-Al2O3 composite was measured by Image Tool software. The results of the tests showed that, by optimizing the milling time to 5 hours, the alumina particles are sufficiently placed in the matrix of the capsules; on the other hand, alumina particles are also properly coated with aluminium powder. When these capsules are added to aluminium melt, the rate of the wetting of alumina particles greatly increases and accordingly the percentage of the reinforcing particles in the cast composite matrix increases dramatically. By surface modification and accordingly increasing percentage of Al2O3, the tensile strength increases and the tensile strength of the composites is higher than that of the matrix alloy. Alireza Samiee, Mohammad Hosein Bina, and Mahmood Meratian Copyright © 2014 Alireza Samiee et al. All rights reserved.