Advances in Materials Science and Engineering The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Current Development in Lead-Free -Based Piezoelectric Materials Sun, 21 Sep 2014 11:37:52 +0000 The lead-free piezoelectric ceramics display good piezoelectric properties which are comparable with Pb(Zr,Ti)O3 (PZT) and these materials overcome the hazard to the environment and human health. The Bi0.5(Na,K)0.5TiO3 (BNKT) is rapidly developed because of good piezoelectric, ferroelectric, and dielectric properties compared to PZT. The origin of giant strain of BNKT piezoelectric materials was found at morphotropic phase boundary due to crystal change from tetragonal to orthorhombic and/or precipitation of cubic phases, in addition to domain switching mechanism. The dopants or secondary phases with ABO3 structure as solid solution are expected to change the crystal structure and create the vacancies which results in enhancement of the piezoelectric properties. In this work, we reviewed the current development of BNKT by dopants and secondary phase as solid solution. Our discussion will focus on role of dopants and secondary phase to piezoelectric properties of BNKT. This result will open the direction to control the properties of lead-free piezoelectric materials. Ngo Duc Quan, Luong Huu Bac, Duong Van Thiet, Vu Ngoc Hung, and Dang Duc Dung Copyright © 2014 Ngo Duc Quan et al. All rights reserved. Palm Olein as Renewable Raw Materials for Industrial and Pharmaceutical Products Applications: Chemical Characterization and Physicochemical Properties Studies Thu, 18 Sep 2014 07:27:51 +0000 Palm olein (P) is widely produced as edible oil in tropical countries. P is considered as renewable raw material for the new industrial and pharmaceutical products synthesis based on its characterization. Palm olein was good on its viscosity index, oxidative stability, and flash and fire point. P contained unsaturated triacylglycerols (TAGs): POO (33.3%); POP (29.6%) which plays an important role in chemical modification process to produce new industrial products. The double bond was detected on 1H-NMR (5.3 ppm) and 13C-NMR (130 ppm) spectra. The chemical compositions of P were tested by using high performance liquid chromatography (HPLC) and gas chromatography (GC) techniques. This unsaturated oil is potentially to be used as renewable raw materials in chemical modification process to synthesise polyols, polyurethane, and biolubricant for industrial and pharmaceutical products application. Darfizzi Derawi, Bashar Mudhaffar Abdullah, Hasniza Zaman Huri, Rahimi M. Yusop, Jumat Salimon, Nany Hairunisa, and Nadia Salih Copyright © 2014 Darfizzi Derawi et al. All rights reserved. Assessment of Size-Dependent Antimicrobial and Cytotoxic Properties of Silver Nanoparticles Mon, 15 Sep 2014 00:00:00 +0000 Nanoscale silver has been increasingly applied to commercial products for their antimicrobial function as antibiotics and disinfectants. In this work, the different sizes of silver nanoparticles (AgNPs) were studied not only in Methylobacterium spp. for their antimicrobial potential but also in human peripheral blood mononuclear cells (PBMCs) for their cytotoxicity in order to determine responses dependent on their particle size. Size controlled silver particles were prepared by chemical reduction of silver cations (Ag+) and then dispersed in water for their physicochemical characterization using transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential measurements. To ascertain antimicrobial response, water-soluble silver nanoparticles were mixed into Methylobacterium spp. cultured for two days and the sample from the broth was spread on the agar plate for colony counting. 10 nm nanoparticles showed more antimicrobial activity than 100 nm particles at which concentrations were equivalently controlled. Increased cytotoxic effect of smaller silver nanoparticles was also observed in PBMCs cocultured with particles. Silver ions released from 10 nm particles might be correlated with upregulated antimicrobial and cytotoxic properties of AgNPs. Yoon Jeong, Dong Woo Lim, and Jonghoon Choi Copyright © 2014 Yoon Jeong et al. All rights reserved. A Study of Antibioactivity of Nanosilver Colloid and Silver Ion Solution Sun, 14 Sep 2014 12:52:49 +0000 The colloidal silver solution was successfully prepared in dielectric fluid by using electrical spark discharge (ESD) without any surfactants. It does not require the toxic chemical agents in the process, which may affect the effectiveness of nanosilver colloid as an antibacterial agent. Nanocolloidal silver produced by ESD is characterized as low cost, zero environmental pollution, continuous, and rapid mass production process. In order to test the effect of antibioactivity, nanosilver dough was tested; the silver nanofluid was prepared by ESD machine, made into dough at different concentrations, and fermented for three hours in order to observe changes in the diameter of the dough. The results showed that the effect of effectiveness of nanosilver at the concentration of 100 ppm was weak, whereas the effect of 60 ppm silver ion (100 ppm AgNO3) was significant, as the dissociation rate of silver ion concentration correlates to the antibioactivity. Kuo-Hsiung Tseng, Heng-Lin Lee, Der-Chi Tien, Ya-Lan Tang, and Yi-Syuan Kao Copyright © 2014 Kuo-Hsiung Tseng et al. All rights reserved. Growth and Device Performance of AlGaN/GaN Heterostructure with AlSiC Precoverage on Silicon Substrate Thu, 11 Sep 2014 12:32:40 +0000 A crack-free AlGaN/GaN heterostructure was grown on 4-inch Si (111) substrate with initial dot-like AlSiC precoverage layer. It is believed that introducing the AlSiC layer between AlN wetting layer and Si substrate is more effective in obtaining a compressively stressed film growth than conventional Al precoverage on Si surface. The metal semiconductor field effect transistor (MESFET), fabricated on the AlGaN/GaN heterostructure grown with the AlSiC layer, exhibited normally on characteristics, such as threshold voltage of −2.3 V, maximum drain current of 370 mA/mm, and transconductance of 124 mS/mm. Jae-Hoon Lee and Jung-Hee Lee Copyright © 2014 Jae-Hoon Lee and Jung-Hee Lee. All rights reserved. Evaluation Technique of Chloride Penetration Using Apparent Diffusion Coefficient and Neural Network Algorithm Thu, 11 Sep 2014 07:10:09 +0000 Diffusion coefficient from chloride migration test is currently used; however this cannot provide a conventional solution like total chloride contents since it depicts only ion migration velocity in electrical field. This paper proposes a simple analysis technique for chloride behavior using apparent diffusion coefficient from neural network algorithm with time-dependent diffusion phenomena. For this work, thirty mix proportions of high performance concrete are prepared and their diffusion coefficients are obtained after long term-NaCl submerged test. Considering time-dependent diffusion coefficient based on Fick’s 2nd Law and NNA (neural network algorithm), analysis technique for chloride penetration is proposed. The applicability of the proposed technique is verified through the results from accelerated test, long term submerged test, and field investigation results. Yun-Yong Kim, Byung-Jae Lee, and Seung-Jun Kwon Copyright © 2014 Yun-Yong Kim et al. All rights reserved. Microwave Analysis for Two-Dimensional C-V and Noise Model of AlGaN/GaN MODFET Wed, 10 Sep 2014 08:38:38 +0000 A new two-dimensional analytical model for the capacitance-voltage and noise characteristics of a AlGaN/GaN MODFET is developed. The two-dimensional electron gas density is calculated as a function of device dimensions. The model includes the spontaneous and polarization effects. The contribution of various capacitances to the performance of the device is shown. The model further predicts the transconductance, drain conductance, and frequency of operation. A high transconductance of 160 mS/mm and a cut-off frequency of 11.6 GHz are obtained for a device of 50 nm gate length. The effect of gate length on the gate length behaviour of the noise coefficients P, R, and C is also studied. The effect of parasitic source and gate resistance has also been studied to evaluate the minimum noise figure. The excellent agreement with the previously simulated results confirms the validity of the proposed model to optimize the device performance at high frequencies. Ramnish Kumar, Sandeep K. Arya, and Anil Ahlawat Copyright © 2014 Ramnish Kumar et al. All rights reserved. Reactivity and Microstructure of Al2O3-Reinforced Magnesium-Matrix Composites Wed, 10 Sep 2014 00:00:00 +0000 Performances of metal matrix composites (MMCs) rely strongly on the distribution of particles within the metal matrix but also on the chemical reaction which may occur at the liquid-solid interfaces. This paper presents the chemical reaction between aluminum based particles Al2O3 and Al2O3-AlOOH with magnesium alloys matrixes AZ91 and EL21, respectively, and studies the microstructure of these reinforced composites. Different methods such as transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and XRD were used to highlight these chemical reactions and to identify products. Results demonstrate the formation of MgO particles within the matrix for both composites and also the dissolution of aluminum in the eutectic region in the case of EL21. Maher Mounib, Matteo Pavese, Claudio Badini, Williams Lefebvre, and Hajo Dieringa Copyright © 2014 Maher Mounib et al. All rights reserved. Effect of Nanofillers on the Polarization and Depolarization Current Characteristics of New LLDPE-NR Compound for High Voltage Application Tue, 09 Sep 2014 11:06:32 +0000 Polymeric nanocomposites in which the nanosize fillers are evenly distributed in the polymer material attract attention as an insulating material due to their ability to enhance the materials performance properties of electrical and mechanical. For high voltage (HV) insulation application, one of the targets is to obtain new insulators with improved dielectric properties. This paper presents the outcome of an experimental study to determine the conductivity level of the linear low-density polyethylene- (LLDPE-)natural rubber (NR) compound, filled with different amount of SiO2 and TiO2 nanofiller by using the polarization and depolarization current (PDC) measurement technique. linear low-density polyethylene (LLDPE) and natural rubber (NR) with the ratio composition of 80 : 20 are selected as a base polymer. The experiment was conducted to find PDC pattern and conductivity variations of each of the LLDPE-NR/SiO2 and LLDPE-NR/TiO2 samples. The results show that the addition of SiO2 filler exhibited less conductivity compared to TiO2 filler with certain percentage. From the study, it can be concluded that LLDPE-NR/SiO2 is a better insulator compared with LLDPE-NR/TiO2. N. A. M. Jamail, M. A. M. Piah, N. A. Muhamad, Z. Salam, N. F. Kasri, R. A. Zainir, and Q. E. Kamarudin Copyright © 2014 N. A. M. Jamail et al. All rights reserved. Unstable Temperature Distribution in Friction Stir Welding Tue, 09 Sep 2014 09:38:26 +0000 In the friction stir welding process, a nonuniform and high generated temperature is undesirable. Unstable temperature and distribution affect thermal and residual stresses along the welding line, thus necessitating mitigation. This paper presents a simple method to prevent significant temperature difference along the welding line and also to help nullifying some defect types associated with this welding, such as end-hole, initial unwelded line, and deformed areas. In the experimental investigation, a heat and force thermocouple and dynamometer were utilized while couple-field thermomechanical models were used to evaluate temperature and its distribution, plastic strain, and material displacement. The suggested method generated uniform temperature distributions. Measurement results are discussed, showing a good correlation with predictions. Sadiq Aziz Hussein, S. Thiru, R. Izamshah, and Abd Salam Md Tahir Copyright © 2014 Sadiq Aziz Hussein et al. All rights reserved. Design and Simulated Characteristics of Nanosized InSb Based Heterostructure Devices Mon, 08 Sep 2014 05:24:03 +0000 Indium antimonide nanoparticles were synthesized at room temperature. X-ray diffraction measurements are utilized to characterize the nanocomposites. The InSb nanoparticle has an average particle size in a range of 47 mm to 99 mm which is observed using the XRD result. The InSb is a material which is used to design the transistor. For designing purpose the simulator TCAD is used, by which the HEMT device is structured and its performance is analyzed and it is found that transistor operates as normal devices. This designed device is more valuable since a nanocomposite InSb material is used as a channel in HEMT device, thereby leading to the nanosized HEMT device. In addition, InSb has the property of high saturation velocity and mobility which results in higher performance of the device than any other materials in III-V compounds. T. D. Subash, T. Gnanasekaran, C. Divya, and J. Jagannathan Copyright © 2014 T. D. Subash et al. All rights reserved. Performance Evaluation of Stone Mastic Asphalt and Hot Mix Asphalt Mixtures Containing Recycled Concrete Aggregate Sun, 07 Sep 2014 12:06:03 +0000 Environmental and economic considerations have encouraged civil engineers to find ways to reuse recycled materials in new constructions. The current paper presents an experimental research on the possibility of utilizing recycled concrete aggregates (RCA) in stone mastic asphalt (SMA) and hot mix asphalt (HMA) mixtures. Three categories of RCA in various percentages were mixed with virgin granite aggregates to produce SMA and HMA specimens. The obtained results indicated that, regardless of the RCA particular sizes, the use of RCA to replace virgin aggregates increased the needed binder content in the asphalt mixtures. Moreover, it was found that even though the volumetric and mechanical properties of the asphalt mixtures are highly affected by the sizes and percentages of the RCA but, based on the demands of the project and traffic volume, utilizing specific amounts of RCA in both types of mixtures could easily satisfy the standard requirements. Mohammad Saeed Pourtahmasb and Mohamed Rehan Karim Copyright © 2014 Mohammad Saeed Pourtahmasb and Mohamed Rehan Karim. All rights reserved. Degradation of Tetracycline by Birnessite under Microwave Irradiation Tue, 02 Sep 2014 09:08:58 +0000 The efficiency and factors affecting tetracycline (TC) degradation by birnessite under microwave irradiation (MI) were investigated under different initial TC concentrations, solution pH, MI time, and MI power. The crystal structure, degradation efficiency, and reaction mechanism were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible spectroscopy (UV-Vis). The results showed that birnessite was an excellent microwave catalyst. The maximum TC removal efficiency by birnessite was 99% under MI at 400 W for 30 min in strongly acidic media. Under MI, the surface activity of birnessite increased, resulting in the ability to accelerate TC removal in high temperature. Meng Liu, Guocheng Lv, Lefu Mei, Xiaoyu Wang, Xuebing Xing, and Libing Liao Copyright © 2014 Meng Liu et al. All rights reserved. Effects of Electric Pulse Current on the Aging Kinetics of 2219 Aluminum Alloy Tue, 02 Sep 2014 00:00:00 +0000 The conventional aging experiments and the low density electric pulse current (LDEPC for short) added aging experiments, with the self-made positive and negative alternating pulse power equipment, were conducted to study the influence of LDEPC on the dynamics of phase transformation in 2219 aluminum alloy by means of measuring the variation of hardness with aging time. The results showed that the hardness in both aging systems increased with the increasing of aging time until it reached the peak value; then it gradually reduced. The hardness of LDEPC added aging is generally greater than the conventional one before the peak aging time. The Avrami dynamics equation of conventional isothermal aging was obtained based on the hardness evolution law. The effects of electromigration and ponderomotive force were introduced into the Avrami empirical equation; in turn, the dynamics equation of LDEPC added aging was established. At last, the isothermal transformation curves of both the regular aging and the LDEPC added aging were derived which revealed that the nucleation rate, as well as the growth rate, was promoted by electric pulse current. The research work provided the theoretical support for the regulation of the coupling energy field on the dynamics of phase transformation in 2219 aluminum alloy. Jiao Zhang, Lihua Zhan, and Shufeng Jia Copyright © 2014 Jiao Zhang et al. All rights reserved. Effect of PVA-co-MMA Copolymer on the Physical, Mechanical, and Thermal Properties of Tropical Wood Materials Sun, 31 Aug 2014 07:02:30 +0000 The present study demonstrates the effect of copolymer on the physical, mechanical, and thermal properties of tropical wood and wood polymer composites (WPCs). Mixed monomers of methyl methacrylate (MMA) and polyvinyl alcohol (PVA) were effectively impregnated into the cellular structure of several types of tropical wood, which then underwent a catalyst-thermal process to polymerize and form WPC. The manufacturing of WPC was confirmed through Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopic (SEM) analysis. The SEM observation showed that polymer converted from monomers filled up wood cell cavities and tightly interacted with wood matrix. The X-ray diffraction results reveal that the degree of crystallinity was significantly improved upon impregnation with PVA-co-MMA copolymer. The modulus of elasticity (MOE) and compressive modulus were found to be significantly higher after treatment with MMA/PVA indicating improvement of mechanical properties of the wood samples. In addition, the modified WPC had lower water absorption compared to their corresponding raw samples. It is interesting to note that thermogravimetric (TGA) analysis shows an extensive improvement in thermal properties of WPC. Md. Saiful Islam, Sinin Hamdan, Mansor B. Ahmad, Mahbub Hasan, Azman Hassan, M. K. Mohamad Haafiz, and M. Jawaid Copyright © 2014 Md. Saiful Islam et al. All rights reserved. Numerical Simulation and Response of Stiffened Plates Subjected to Noncontact Underwater Explosion Thu, 28 Aug 2014 13:17:51 +0000 A numerical simulation has been carried out to examine the response of steel plates with different arrangement of stiffeners and subjected to noncontact underwater explosion (UNDEX) with different shock loads. Numerical analysis of the underwater explosion phenomena is implemented in the nonlinear finite element code ABAQUS/Explicit. The aim of this work is to enhance the dynamic response to resist UNDEX. Special emphasis is focused on the evolution of mid-point displacements. Further investigations have been performed to study the effects of including material damping and the rate-dependant material properties at different shock loads. The results indicate that stiffeners configurations and shock loads affect greatly the overall performance of steel plates and sensitive to the materials data. Also, the numerical results can be used to obtain design guidelines of floating structures to enhance resistance of underwater shock damage, since explosive tests are costly and dangerous. Elsayed Fathallah, Hui Qi, Lili Tong, and Mahmoud Helal Copyright © 2014 Elsayed Fathallah et al. All rights reserved. Preparation of N-Doped TiO2-ZrO2 Composite Films under Electric Field and Heat Treatment and Assessment of Their Removal of Methylene Blue from Solution Thu, 28 Aug 2014 11:26:49 +0000 TiO2-ZrO2 composite film with the grain size of 50 nm was synthesized by electric field and heat (EF&H) treatments. Portions of O atoms in the TiO2 network structure were replaced by N atoms as revealed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses, suggesting formation of a nonstoichiometric compound on the composite film. The UV-Vis spectra of the film suggested that the visible light with wavelength of 550 nm could be absorbed for the N-doped composite film after EF&H treatment in comparison to a cutoff wavelength of 400 nm for the composite film without EF treatment. Photocatalytic experiments showed that the degradation rate of methylene blue by N-doped composite films increased significantly under visible light irradiation. The partial replacement of O by doped N played a very important role in narrowing the band gap and improving the visible light photocatalytic reactivity. Lefu Mei, Ranfang Zuo, Jing Xie, Libing Liao, and Hao Ding Copyright © 2014 Lefu Mei et al. All rights reserved. Improving the Efficiency Enhancement of Photonic Crystal Based InGaN Solar Cell by Using a GaN Cap Layer Wed, 27 Aug 2014 12:06:08 +0000 We studied a high indium content (0.8) InGaN based solar cell design where the active InGaN layer is sandwiched between a GaN cap layer and a GaN spacer layer. The incorporation of the sacrificial cap layer allows for the etching of the front surface without removing the active InGaN resulting in a 50% enhancement of the short-circuit current density for a 15 nm-thick InGaN layer. T. F. Gundogdu, M. Gökkavas, and E. Ozbay Copyright © 2014 T. F. Gundogdu et al. All rights reserved. Investigating the Possibility to Reduce the Residual Stress Level in 2.5D Cutting Using Titanium Coated Carbide Ball End Mill Wed, 27 Aug 2014 08:48:55 +0000 End milling is a multipoint cutting process in which material is removed from a workpiece by a rotating tool. It is widely used in cutting 2.5D profiles such as point-to-point, contouring, and pocketing operations. 2.5D machining possesses the capability to translate in all 3 axes but can perform the cutting operation in only 2 of the 3 axes at a time. This study focuses on optimizing the cutting parameters, such as machined surface inclinationangle, axial depth of cut, spindle speed, and feed rate for better surface integrity, namely, microhardness, residual stress, and microstructure in 2.5D cutting utilizing a titanium-coated carbide ball end mill. An optimization method known as Taguchi optimization, which includes planning, conducting, and analyzing results of matrix experiments, was used in order to achieve the best cutting parameter level. Data analysis was conducted using signal-to-noise () and target performance measurement (TPM) response analysis and analysis of variance (Pareto ANOVA). The optimum condition results obtained through analysis show improvements in microhardness of about 0.7%, residual stress in the feed direction of about 18.6%, and residual stress in the cutting direction of about 15.4%. N. Masmiati, H. S. Chan, Ahmed A. D. Sarhan, M. A. Hassan, and M. Hamdi Copyright © 2014 N. Masmiati et al. All rights reserved. Tribological Behavior of Si3N4/Ti3SiC2 Contacts Lubricated by Lithium-Based Ionic Liquids Wed, 27 Aug 2014 06:52:55 +0000 The tribological performance of Si3N4 ball sliding against Ti3SiC2 disc lubricated by lithium-based ionic liquids (ILs) was investigated using an Optimol SRV-IV oscillating reciprocating friction and wear tester at room temperature (RT) and elevated temperature (100°C). Glycerol and the conventional imidazolium-based IL 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (L-F106) were used as references under the same experimental conditions. The results show that the lithium-based ILs had higher thermal stabilities than glycerol and lower costs associated with IL preparation than L-F106. The tribotest results show that the lithium-based ILs were effective in reducing the friction and wear of Si3N4/Ti3SiC2 contacts. [Li(urea)]TFSI even produced better tribological properties than glycerol and L-F106 both at RT and 100°C. The SEM/EDS and XPS results reveal that the excellent tribological endurance of Si3N4/Ti3SiC2 contacts lubricated by lithium-based ILs was mainly attributed to the formation of surface protective films composed of various tribochemical products. Haizhong Wang, Zenghong Song, Dan Qiao, Dapeng Feng, and Jinjun Lu Copyright © 2014 Haizhong Wang et al. All rights reserved. Sintering Behavior and Mechanical Properties of Biphasic Calcium Phosphate Ceramics Mon, 25 Aug 2014 10:56:18 +0000 The sintering behavior and the mechanical properties of a mechanical mixture of hydroxyapatite and tricalcium phosphate (BCP) ceramics with the composition of 30% HA and 70% TCP are experimentally investigated in the temperature range between 1000°C and 1300°C. The results show that consolidation, grain growth, and Vickers hardness generally increase with increasing sintering temperature up to 1200°C. However, microstructure observation indicates that cracks are formed along the grain boundaries as well as in the bulk of the grains after sintering at 1200°C. Moreover, the best values of compressive strength, modulus of elasticity, and toughness are achieved in the samples sintered at 1100°C. These properties at 1100°C decay with sintering at 1200°C and increase again after sintering at 1300°C. Mehmet Yetmez Copyright © 2014 Mehmet Yetmez. All rights reserved. Fabrication of Porous and Nanoporous Aluminum via Selective Dissolution of Al-Zn Alloys Sun, 24 Aug 2014 11:33:55 +0000 Porous and nanoporous aluminum have been fabricated via selective dissolution. Al-Zn alloys were dealloyed in an aqueous solution of nitric acid to selectively dissolve zinc. Fast solidification methods permitted to adjust the precursor microstructure of the parent alloy in order to induce supersaturation of zinc in aluminum. An electric potential applied during corrosion affected the final morphology of porosity. Electronic imaging evinced the presence of regions with less than 100 nm diameter pores. This nanoporosity was only present in electrochemically dealloyed samples. We observed two types of porosity in dealloyed samples: a primary porosity resulting from the selective removal of zinc-rich interdendritic phases and a secondary porosity resulting from nanoporosity evolution inside zinc-supersaturated dendrites. Oscar Marcelo Suárez, Elvin G. Estremera, Rafael Soler, Amarilis Declet, and Arturo J. Hernández-Maldonado Copyright © 2014 Oscar Marcelo Suárez et al. All rights reserved. Numerical Simulation Procedure for Modeling TGO Crack Propagation and TGO Growth in Thermal Barrier Coatings upon Thermal-Mechanical Cycling Thu, 21 Aug 2014 07:21:57 +0000 This paper reports a numerical simulation procedure to model crack propagation in TGO layer and TGO growth near a surface groove in metal substrate upon multiple thermal-mechanical cycles. The material property change method is employed to model TGO formation cycle by cycle, and the creep properties for constituent materials are also incorporated. Two columns of repeated nodes are placed along the interface of the potential crack, and these nodes are bonded together as one node at a geometrical location. In terms of critical crack opening displacement criterion, onset of crack propagation in TGO layer has been determined by finite element analyses in comparison with that without predefined crack. Then, according to the results from the previous analyses, the input values for the critical failure parameters for the subsequent analyses can be decided. The robust capabilities of restart analysis in ABAQUS help to implement the overall simulation for TGO crack propagation. The comparison of the TGO final deformation profile between numerical and experimental observation shows a good agreement indicating the correctness and effectiveness of the present procedure, which can guide the prediction of the failure in TGO for the future design and optimization for TBC system. Ding Jun, Huang Xia, Chen Song, and Yang E-Chuan Copyright © 2014 Ding Jun et al. All rights reserved. Evaluation of Concrete Durability Performance with Sodium Silicate Impregnants Thu, 21 Aug 2014 00:00:00 +0000 This paper presents an enhanced performance in concrete impregnated with silicate compound. Two different types of impregnant materials (inorganic and combined type) are applied to concrete samples with different strength grade (21 MPa and 34 MPa). Through lab-scale test, improved performances in impregnated concrete are evaluated regarding porosity, strength, chloride diffusion coefficient, permeability of air/water, and absorption. Long-term exposure tests including strength, chloride penetration depth and contents, and electrical potential for steel corrosion are performed for different marine conditions. While the surface-impregnated concrete shows marginal increase in strength, significant improvements of porosity, absorption, and permeability are evaluated. The resistance to chloride attack reasonably improved through simply spraying the inorganic silicate in atmospheric-salt spraying condition. Sang-Soon Park, Yun Yong Kim, Byung Jae Lee, and Seung-Jun Kwon Copyright © 2014 Sang-Soon Park et al. All rights reserved. Investigation on the Crack Initiation of V-Shaped Notch Tip in Precision Cropping Thu, 21 Aug 2014 00:00:00 +0000 The crack initiation of V-shaped notch tip has a very important influence on the cross-section quality and the cropping time for every segment of metal bar in course of low stress precision cropping. By the finite element method, the influence of machining precision of V-shaped notch bottom corner on the crack initiation location is analyzed and it is pointed out that the crack initiation point locates in the place at the maximal equivalent stress change rate on V-shaped notch surface. The judgment criterion of the crack initiation direction is presented and the corresponding crack initiation angle can be calculated by means of the displacement extrapolation method. The factual crack initiation angle of the metal bar has been measured by using the microscopic measurement system. The formula of the crack initiation life of V-shaped notch tip is built, which mainly includes the stress concentration factor of V-shaped notch, the tensile properties of metal material, and the cyclic loading conditions. The experimental results show that the obtained theoretical analyses about the crack initiation location, the crack initiation direction, and the crack initiation time in this paper are correct. It is also shown that the crack initiation time accounts for about 80% of the cropping time for every segment of the metal bar. Lijun Zhang, Shengdun Zhao, and Zhenwei Wang Copyright © 2014 Lijun Zhang et al. All rights reserved. Electrical Characterization of Sol-Gel Derived TiO2 Film on c-Si Substrate by Admittance Measurement Wed, 20 Aug 2014 10:38:48 +0000 Transport and storage properties of sol-gel synthesized, namely, dip coating technique, titanium dioxide (TiO2) thin film over crystalline silicon (c-Si), has been investigated by means of current-voltage (I-V) and admittance analysis within different ambient. Considering the work function of anatase TiO2 film, determined by both FTIR and TG/DTA analysis, silver (Ag) as front metal electrode was chosen to hinder a barrier for charge carriers. Electrical analysis implied that Ag/TiO2/c-Si structure was actually constituted by Ag/TiO2/native silicon dioxide (SiO2)/c-Si [SIS] structure, in which SiO2 layer was identified by FTIR analysis. Consequently, the electrical features of the film were interpreted in terms of SIS diode that is capable of explaining C-V features. Ayşe Evrim Saatci and Orhan Özdemir Copyright © 2014 Ayşe Evrim Saatci and Orhan Özdemir. All rights reserved. Experimental Study on Thermal Performance of Externally Insulated Walls of Intermittent Air-Conditioned Rooms in Summer in Hot Summer and Cold Winter Region, China Wed, 20 Aug 2014 08:55:21 +0000 Now requirements for the thermal performance of building walls are based on the assumption that heat flux transfers in one direction through the wall. However, in Hot Summer and Cold Winter Region of China, the direction of heat flow in the wall not only changes with the seasons, but also changes in the same period of using. In this paper, dynamic thermal process of externally insulated walls in different air-conditioner’s running state in summer in Chongqing, China, was tested. The distribution characteristics of the outdoor and indoor air temperature and the surface and inner temperatures of the wall were analyzed and demonstrated. Based on the unsteady-state heat transfer theory, the study calculated and analyzed the distribution characteristics of the direction of the heat flux in the thermal process. Also the characteristics of insulation and heat preservation for walls under different air-conditioner’s running state were analyzed. It is shown that, in any air-conditioner’s running state, the direction of the heat flux through the wall is obviously dynamically changing. There is obvious difference in the thermal performance needs of the wall; that is, it has strong demand for thermal insulation in daytime and strong demand for heat dissipation during night time in summer. Yong Ding, Lu Xu, Baizhan Li, and Xiaoqing Liu Copyright © 2014 Yong Ding et al. All rights reserved. Study of Interface Charge Densities for ZrO2 and HfO2 Based Metal-Oxide-Semiconductor Devices Wed, 20 Aug 2014 06:28:59 +0000 A thickness-dependent interfacial distribution of oxide charges for thin metal oxide semiconductor (MOS) structures using high-k materials ZrO2 and HfO2 has been methodically investigated. The interface charge densities are analyzed using capacitance-voltage (C-V) method and also conductance (G-V) method. It indicates that, by reducing the effective oxide thickness (EOT), the interface charge densities () increases linearly. For the same EOT, has been found for the materials to be of the order of 1012 cm−2 eV−1 and it is originated to be in good agreement with published fabrication results at p-type doping level of  cm−3. Numerical calculations and solutions are performed by MATLAB and device simulation is done by ATLAS. N. P. Maity, Reshmi Maity, R. K. Thapa, and S. Baishya Copyright © 2014 N. P. Maity et al. All rights reserved. Membrane Material-Based Rigid Solar Array Design and Thermal Simulation for Stratospheric Airships Tue, 19 Aug 2014 11:45:04 +0000 In order to improve effective utilization of rigid solar array used in stratospheric airships here, the flexible connection design and light laminated design were introduced to rigid solar array. Based on the analysis of the design scheme, firstly, the equivalent coefficient of thermal conductivity was calculated by the theoretical formula. Subsequently, the temperature variation characteristics of the solar cell module were accurately modeled and simulated by using Computational Fluid Dynamics (CFD) software. Compared to the results of test samples, the solar cell module described here guaranteed effective output as well as good heat insulating ability, effectively improving the feasibility of the stratospheric airship design. In addition, the simulation model can effectively simulate the temperature variation characteristics of the solar cell, which, therefore, provides technical support for the engineering application. Kangwen Sun, Ming Zhu, and Qiang Liu Copyright © 2014 Kangwen Sun et al. All rights reserved. Structural, Electrical, and Ethanol-Sensing Properties of Nanoparticles Mon, 18 Aug 2014 13:04:24 +0000 The nanocrystalline () powders with orthorhombic perovskite phase were prepared by sol-gel method. The average crystallite sizes of powders are about 20 nm. The resistance and gas-sensing properties of the based sensors were investigated in the temperature range from 160 to 300°C. The results demonstrated that the resistance and response of the perovskite thick films changed with the increase of Nd content. Nguyen Thi Thuy, Dang Le Minh, Ho Truong Giang, and Nguyen Ngoc Toan Copyright © 2014 Nguyen Thi Thuy et al. All rights reserved.