Advances in Materials Science and Engineering The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Stress Monitoring for Anchor Rods System in Subway Tunnel Using FBG Technology Wed, 25 Feb 2015 09:47:35 +0000 This paper presents a model test, used on the tunnels on Xi’an Metro Line 2, as the prototype for evaluating the reinforcing effect of the anchor rod in tunnel construction in loess areas. An independently designed fiber Bragg grating (FBG) sensor was used to monitor the seven strain conditions of the rock bolts during the construction. The result shows that the axial stress of the rock bolt changes after the excavation and increases steadily with the growing pressure in the wall rock. Results additionally show that the anchor rods at the tunnel vault are subjected to a compressive stress that remains relatively constant after the primary and the secondary lining, while those at the spandrel and the corner of the tunnel are subjected to increased tensile stress. This paper demonstrates the feasibility and the superiority of FBG technology for tunnel model tests. Xiaolin Weng, Haohao Ma, and Jun Wang Copyright © 2015 Xiaolin Weng et al. All rights reserved. Optimum Control for Nonlinear Dynamic Radial Deformation of Turbine Casing with Time-Varying LSSVM Wed, 25 Feb 2015 06:39:33 +0000 With the development of the high performance and high reliability of aeroengine, the blade-tip radial running clearance (BTRRC) of high pressure turbine seriously influences the reliability and performance of aeroengine, wherein the radial deformation control of turbine casing has to be concerned in BTRRC design. To improve BTRRC design, the optimum control-based probabilistic optimization of turbine casing radial deformation was implemented using time-varying least square support vector machine (T-LSSVM) by considering nonlinear material properties and dynamic thermal load. First the T-LSSVM method was proposed and its mathematical model was established. And then the nonlinear dynamic optimal control model of casing radial deformation was constructed with T-LSSVM. Thirdly, through the numerical experiments, the T-LSSVM method is demonstrated to be a promising approach in reducing additional design samples and improving computational efficiency with acceptable computational precision. Through the optimum control-based probabilistic optimization for nonlinear dynamic radial turbine casing deformation, the optimum radial deformation is 7.865 × 10−4 m with acceptable reliability degree 0.995 6, which is reduced by 7.86 × 10−5 m relative to that before optimization. These results validate the effectiveness and feasibility of the proposed T-LSSVM method, which provides a useful insight into casing radial deformation, BTRRC control, and the development of gas turbine with high performance and high reliability. Cheng-Wei Fei, Guang-Chen Bai, Wen-Zhong Tang, and Yatsze Choy Copyright © 2015 Cheng-Wei Fei et al. All rights reserved. Influence of Heat Treatment on Biocorrosion and Hemocompatibility of Biodegradable Mg-35Zn-3Ca Alloy Tue, 24 Feb 2015 11:45:24 +0000 Mg-35Zn-3Ca (wt.%) alloy containing nontoxic and biocompatible Zn and Ca as alloying elements was prepared and subjected to heat treatment and artificial aging for different duration of time to reduce its rate of degradation. Solution heat treatment was performed at 310°C while artificial aging was performed at 170°C for 0, 2.5, 5.0, 7.5, and 10.0 h and they were designated as AT0, AT1, AT2, AT3, and AT4, respectively. The finest and most homogenous reticulum was observed on the surface of the AT2 group. The result of immersion test in Hank’s balanced salt solution (HBSS) showed that the corrosion rate of the AT2 group was 2.32 mg/(cm2 day), which was significantly lower as compared to other groups . The hemolysis value was ≤5% in all groups, indicating no toxicity during short-term blood reaction. Jeong-Hui Ji, Il-Song Park, Yu-Kyoung Kim, Sook-Jeong Lee, Tae-Sung Bae, and Min-Ho Lee Copyright © 2015 Jeong-Hui Ji et al. All rights reserved. Feasible Time Evolution Model That Predicts Breakdown in Thin SiO2 Films within Unstressed Interval after Constant-Current Stress Tue, 24 Feb 2015 08:21:09 +0000 This paper proposes a poststress time evolution model for sub-10-nm thick SiO2 films for degradation prediction and the extraction of trap-related parameters. The model is based on the understanding that the degradation in thin SiO2 films continues within the unstressed interval. The phenomenon is captured by an analytical expression that indicates that the time evolution of SiO2 film degradation roughly consists of two stages and that the degradation is more likely to occur if water molecules are present. It is demonstrated that the simple analytical model successfully reproduces measured results. It is also suggested that the degradation process considered here is related to oxygen diffusion in the resistive transition process. Yasuhisa Omura Copyright © 2015 Yasuhisa Omura. All rights reserved. High-Performance Grouting Mortar Based on Mineral Admixtures Mon, 23 Feb 2015 15:02:22 +0000 A study on high-performance grouting mortar is reported. The common mortar was modified by mineral admixtures such as gypsum, bauxite, and alunite. The effects of mineral admixtures on the fluidity, setting time, expansion, strength, and other properties of mortar were evaluated experimentally. The microstructure of the modified mortar was characterized by X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry. Moreover, the expansive performance and strength of the grouting mortar were verified by anchor pullout test. The results show that the best conditions for gypsum-bauxite grouting mortar are as follows: a water-to-binder ratio of 0.3, a mineral admixture content of ~15%, and a molar ratio K of 2. The ultimate bearing capacity of the gypsum-bauxite grouting mortar anchor increased by 39.6% compared to the common mortar anchor. The gypsum-bauxite grouting mortar has good fluidity, quick-setting, microexpansion, early strength, and high strength performances. Cong Ma, Yuehu Tan, Erbing Li, Yinsuo Dai, and Meng Yang Copyright © 2015 Cong Ma et al. All rights reserved. Statistical Analysis of the Tensile Strength of Coal Fly Ash Concrete with Fibers Using Central Composite Design Sun, 22 Feb 2015 10:16:12 +0000 The influence of coal fly ash and glass fiber waste on the tensile strength of cement concrete was studied using central composite design. Coal fly ash was used to replace 10% of the cement in the concrete mix. Glass fiber was added to improve the tensile properties of the concrete in different dosages and lengths. In total, 14 mixes were investigated, one only with 10% coal fly ash replacement of cement and the other thirteen were determined by the experimental design. Using analysis of variance, the order of importance of the variables was established for each property (flexural strength and split tensile strength). From the nonlinear response surfaces, it was found that higher values of flexural strength were obtained for fibers longer than 12 mm and at a dosage of 1-2%. For split tensile strength, higher values were obtained for fibers with a length of 19–28 mm and at a dosage of 1–1.5%. Marinela Barbuta, Emanuela Marin, Sorin Mihai Cimpeanu, Gigel Paraschiv, Daniel Lepadatu, and Roxana Dana Bucur Copyright © 2015 Marinela Barbuta et al. All rights reserved. Hydraulic Performance Modifications of a Zeolite Membrane after an Alkaline Treatment: Contribution of Polar and Apolar Surface Tension Components Thu, 19 Feb 2015 13:49:23 +0000 Hydraulic permeability measurements are performed on low cut-off Na-mordenite (MOR-type zeolites) membranes after a mild alkaline treatment. A decrease of the hydraulic permeability is systematically observed. Contact angle measurements are carried out (with three polar liquids) on Na-mordenite films seeded onto alumina plates (flat membranes). A decrease of the contact angles is observed after the alkaline treatment for the three liquids. According to the theory of Lifshitz-van der Waals interactions in condensated state, surface modifications are investigated and a variation of the polar component of the material surface tension is observed. After the alkaline treatment, the electron-donor contribution (mainly due to the two remaining lone electron pairs of the oxygen atoms present in the zeolite extra frameworks) decreases and an increase of the electron-receptor contribution is observed and quantified. The contribution of the polar component to the surface tension is attributed to the presence of surface defaults, which increase the surface hydrophilicity. The estimated modifications of the surface interaction energy between the solvent (water) and the Na-mordenite active layer are in good agreement with the decrease of the hydraulic permeability observed after a mild alkaline treatment. Patrick Dutournié, Ali Said, T. Jean Daou, Jacques Bikaï, and Lionel Limousy Copyright © 2015 Patrick Dutournié et al. All rights reserved. Evaluation of Permanent Deformation of Unmodified and Rubber-Reinforced SMA Asphalt Mixtures Using Dynamic Creep Test Wed, 18 Feb 2015 11:28:38 +0000 This paper presents the evaluation of permanent deformation of rubber-reinforced SMA asphalt mixtures by using dynamic creep test. The effect of trans-polyoctenamer as a cross-linking agent in permanent deformation of rubberized mixtures was also evaluated. Dynamic creep test was conducted at different stress levels (200 kPa, 400 kPa) and temperatures (40°C, 50°C). Permanent deformation parameters such as dynamic creep curve, ultimate strain, and creep strain slope (CSS) were used to analyse the results. Finally, the creep behaviour of the specimens was estimated by the Zhou three-stage creep model. The results show that crumb rubber and trans-polyoctenamer significantly affected the parameters especially at high stress and temperatures. Consistent findings were observed for all permanent deformation parameters. Moreover, based on Zhou model, it was concluded that resistance to permanent deformation was improved by application of crumb rubber and trans-polyoctenamer. Herda Yati Katman, Mohd Rasdan Ibrahim, Mohamed Rehan Karim, Nuha Salim Mashaan, and Suhana Koting Copyright © 2015 Herda Yati Katman et al. All rights reserved. Properties and Microstructures of Sn-Ag-Cu-X Lead-Free Solder Joints in Electronic Packaging Wed, 18 Feb 2015 11:03:57 +0000 SnAgCu solder alloys were considered as one of the most popular lead-free solders because of its good reliability and mechanical properties. However, there are also many problems that need to be solved for the SnAgCu solders, such as high melting point and poor wettability. In order to overcome these shortcomings, and further enhance the properties of SnAgCu solders, many researchers choose to add a series of alloying elements (In, Ti, Fe, Zn, Bi, Ni, Sb, Ga, Al, and rare earth) and nanoparticles to the SnAgCu solders. In this paper, the work of SnAgCu lead-free solders containing alloying elements and nanoparticles was reviewed, and the effects of alloying elements and nanoparticles on the melting temperature, wettability, mechanical properties, hardness properties, microstructures, intermetallic compounds, and whiskers were discussed. Lei Sun and Liang Zhang Copyright © 2015 Lei Sun and Liang Zhang. All rights reserved. Properties of GH4169 Superalloy Characterized by Nonlinear Ultrasonic Waves Tue, 17 Feb 2015 14:20:11 +0000 The nonlinear wave motion equation is solved by the perturbation method. The nonlinear ultrasonic coefficients β and δ are related to the fundamental and harmonic amplitudes. The nonlinear ultrasonic testing system is used to detect received signals during tensile testing and bending fatigue testing of GH4169 superalloy. The results show that the curves of nonlinear ultrasonic parameters as a function of tensile stress or fatigue life are approximately saddle. There are two stages in relationship curves of relative nonlinear coefficients β′ and δ′ versus stress and fatigue life. The relative nonlinear coefficients β′ and δ′ increase with tensile stress when tensile stress is lower than 65.8% of the yield strength, and they decrease with tensile stress when tensile stress is higher than 65.8% of the yield strength. The nonlinear coefficients have the extreme values at 53.3% of fatigue life. For the second order relative nonlinear coefficient β′, there is good agreement between the experimental data and the comprehensive model. For the third order relative nonlinear coefficient δ′, however, the experiment data does not accord with the theoretical model. Hongjuan Yan, Chunguang Xu, Dingguo Xiao, and Haichao Cai Copyright © 2015 Hongjuan Yan et al. All rights reserved. Specimen Test of Large-Heat-Input Fusion Welding Method for Use of SM570TMCP Sun, 15 Feb 2015 08:38:28 +0000 In this research, the large-heat-input welding conditions optimized to use the rear plate and the high-performance steel of SM570TMCP, a new kind of steel suitable for the requirements of prospective customers, are proposed. The goal of this research is to contribute to securing the welding fabrication optimized to use the high-strength steel and rear steel plates in the field of construction industry in the future. This research is judged to contribute to securing the welding fabrication optimized to use the high-strength steel and rear steel plates in the field of construction industry in the future. Dongkyu Lee and Soomi Shin Copyright © 2015 Dongkyu Lee and Soomi Shin. All rights reserved. Enhanced Fatigue Strength of Commercially Pure Ti Processed by Rotary Swaging Thu, 12 Feb 2015 13:19:33 +0000 Fully reversed bending fatigue tests were performed on polished hour-glass specimens of commercially pure titanium grade 1 with three different grain sizes, that were produced by severe plastic deformation (rotary swaging) and subheat treatments, in order to examine the effect of grain size on fatigue. An improvement in fatigue strength was observed, as the polycrystal grain size was refined. The endurance limit stress was shown to depend on the inverse square root of the grain size as described empirically by a type of Hall-Petch relation. The effect of refining grain size on fatigue crack growth is to increase the number of microstructural barriers to the advancing crack and to reduce the slip length ahead of the crack tip, and thereby lower the crack growth rate. It was found that postdeformation annealing above recrystallization temperature could additionally enhance the work-hardening capability and the ductility of the swaged material, which led to a marked reduction in the fatigue notch sensitivity. At the same time, this reduction was accompanied with a pronounced loss in strength. The high cycle fatigue performance was discussed in detail based on microstructure and mechanical properties. Hasan ALkhazraji, Ehab El-Danaf, Manfred Wollmann, and Lothar Wagner Copyright © 2015 Hasan ALkhazraji et al. All rights reserved. Development of Silver Ion Doped Antibacterial Clays and Investigation of Their Antibacterial Activity Thu, 12 Feb 2015 11:27:38 +0000 Kaolinite, sepiolite, and clinoptilolite were used as carriers to develop antibacterial materials. The materials were enriched in sodium by ion exchange. Silver ion exchange by silver nitrate followed by phosphoric acid treatment enabled the controlled release of silver. The antibacterial function of the materials was investigated by halo test and the amount of silver released was investigated by energy dispersive X-ray spectroscopy. The enhanced antibacterial efficiency was obtained by minimizing the silver release which further provided longevity to the material and prevented the health risks posed by excess silver release. Filiz B. Karel, Ali S. Koparal, and Elif Kaynak Copyright © 2015 Filiz B. Karel et al. All rights reserved. Electrocatalytic Study of Paracetamol at a Single-Walled Carbon Nanotube/Nickel Nanocomposite Modified Glassy Carbon Electrode Wed, 11 Feb 2015 14:24:34 +0000 A rapid, simple, and sensitive method for the electrochemical determination of paracetamol was developed. A single-walled carbon nanotube/nickel (SWCNT/Ni) nanocomposite was prepared and immobilized on a glassy carbon electrode (GCE) surface via mechanical attachment. This paper reports the voltammetry study on the effect of paracetamol concentration, scan rate, pH, and temperature at a SWCNT/Ni-modified electrode in the determination of paracetamol. The characterization of the SWCNT/Ni/GCE was performed by cyclic voltammetry. Variable pressure scanning electron microscopy (VPSEM) and energy dispersive X-ray (EDX) spectrometer were used to examine the surface morphology and elemental profile of the modified electrode, respectively. Cyclic voltammetry showed significant enhancement in peak current for the determination of paracetamol at the SWCNT/Ni-modified electrode. A linear calibration curve was obtained for the paracetamol concentration between 0.05 and 0.50 mM. The SWCNT/Ni/GCE displayed a sensitivity of 64 mA M−1 and a detection limit of 1.17 × 10−7 M in paracetamol detection. The proposed electrode can be applied for the determination of paracetamol in real pharmaceutical samples with satisfactory performance. Results indicate that electrodes modified with SWCNT and nickel nanoparticles exhibit better electrocatalytic activity towards paracetamol. Koh Sing Ngai, Wee Tee Tan, Zulkarnain Zainal, Ruzniza Mohd Zawawi, and Joon Ching Juan Copyright © 2015 Koh Sing Ngai et al. All rights reserved. Corrigendum to “Recent Advances in Dye Sensitized Solar Cells” Wed, 11 Feb 2015 09:02:27 +0000 Umer Mehmood, Saleem-ur Rahman, Khalil Harrabi, Ibnelwaleed A. Hussein, and B. V. S. Reddy Copyright © 2015 Umer Mehmood et al. All rights reserved. Design and Micromagnetic Simulation of Fe/L10-FePt/Fe Trilayer for Exchange Coupled Composite Bit Patterned Media at Ultrahigh Areal Density Wed, 11 Feb 2015 07:43:12 +0000 Exchange coupled composite bit patterned media (ECC-BPM) are one candidate to solve the trilemma issues, overcome superparamagnetic limitations, and obtain ultrahigh areal density. In this work, the ECC continuous media and ECC-BPM of Fe/L10-FePt/Fe trilayer schemes are proposed and investigated based on the Landau-Lifshitz-Gilbert equation. The switching field, , of the hard phase in the proposed continuous ECC trilayer media structure is reduced below the maximum write head field at interlayer exchange coupling between hard and soft phases, , higher than 20 pJ/m and its value is lower than that for continuous L10-FePt single layer media and L10-FePt/Fe bilayer. Furthermore, the of the proposed ECC-BPM is lower than the maximum write head field with exchange coupling coefficient between neighboring dots of 5 pJ/m and over 10 pJ/m. Therefore, the proposed ECC-BPM trilayer has the highest potential and is suitable for ultrahigh areal density magnetic recording technology at ultrahigh areal density. The results of this work may be gainful idea for nanopatterning in magnetic media nanotechnology. Warunee Tipcharoen, Arkom Kaewrawang, and Apirat Siritaratiwat Copyright © 2015 Warunee Tipcharoen et al. All rights reserved. Optical Properties of Erbium Zinc Tellurite Glass System Wed, 11 Feb 2015 07:32:48 +0000 Er3+-doped tellurite glasses with molar compositions of xEr2O3-20ZnO-()TeO2 (, 1, 2, 3, and 4 mole%) (EZT) have been successfully synthesized by the melt-quenching method. Density and molar volume have been measured. UV-VIS absorption spectra in the wavelength range of 400–800 nm at room temperature has been measured. The band gap for every composition has been calculated. Photoluminescence spectroscopy in the wavelength range of 400–650 nm and at room temperature has been evaluated. Sidek Hj. Abdul Aziz, R. El-Mallawany, Siti Shawaliza Badaron, Halimah Mohamed Kamari, and Khamirul Amin Matori Copyright © 2015 Sidek Hj. Abdul Aziz et al. All rights reserved. Influence of Fly Ash, Bottom Ash, and Light Expanded Clay Aggregate on Concrete Tue, 10 Feb 2015 12:22:48 +0000 Invention of new methods in strengthening concrete is under work for decades. Developing countries like India use the extensive reinforced construction works materials such as fly ash and bottom ash and other ingredients in RCC construction. In the construction industry, major attention has been devoted to the use of fly ash and bottom ash as cement and fine aggregate replacements. In addition, light expanded clay aggregate has been introduced instead of coarse aggregate to make concrete have light weight. This paper presents the results of a real-time work carried out to form light weight concrete made with fly ash, bottom ash, and light expanded clay aggregate as mineral admixtures. Experimental investigation on concrete mix M20 is done by replacement of cement with fly ash, fine aggregate with bottom ash, and coarse aggregate with light expanded clay aggregate at the rates of 5%, 10%, 15%, 20%, 25%, 30%, and 35% in each mix and their compressive strength and split tensile strength of concrete were discussed for 7, 28, and 56 days and flexural strength has been discussed for 7, 28, and 56 days depending on the optimum dosage of replacement in compressive strength and split tensile strength of concrete. S. Sivakumar and B. Kameshwari Copyright © 2015 S. Sivakumar and B. Kameshwari. All rights reserved. The Use of Le Bail Method to Analyze the Semicrystalline Pattern of a Nanocomposite Based on Polyaniline Emeraldine-Salt Form and α-Al2O3 Mon, 09 Feb 2015 10:06:20 +0000 Ceramic nanocomposites constituted by a matrix of α-Al2O3 microparticles reinforced by polyaniline emeraldine-salt form (PANI-ES) nanoparticles were prepared by in situ polymerization and characterized structural and morphologically. Peaks related to both materials were observed through XRD technique: PANI-ES presented peaks at = 8.9, 14.9, 20.8, 25.3, 27.1, and 30.0° and in α-Al2O3 phase peaks were found at = 25.6, 35.2, 37.9, 43.5, 52.6, 57.6, and 68.1°. Nanocomposite crystallinity percentage was estimated around 70%. SEM showed a polymerization of PANI-ES over alumina plates. By Le Bail method it was observed that PANI-ES and α-Al2O3 have crystallite average size around, respectively, 41 and 250 Å. By FTIR analysis characteristic absorption bands of both materials were identified. Additional bands indicating new chemical bonds were not observed, suggesting that nanocomposite was formed by physical deposition. Nanocomposite DC electrical conductivity was found around 0.24 S/cm (against  S/cm for pure PANI-ES), showing an increase of about 1,300 times compared to the pure PANI-ES at room temperature. Thus, this paper showed that both materials have kept its original structural characteristics and exhibited high electrical conductivity when combined in nanocomposite form. Edgar A. Sanches, Adriano de S. Carolino, Amanda L. dos Santos, Edson G. R. Fernandes, Daniela M. Trichês, and Yvonne P. Mascarenhas Copyright © 2015 Edgar A. Sanches et al. All rights reserved. The Mechanism of Intragranular Acicular Ferrite Nucleation Induced by Mg-Al-O Inclusions Thu, 05 Feb 2015 10:08:05 +0000 The features of inclusion and microstructure for carbon structural steel containing Mg-Al-O inclusions were studied through the scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). It can be seen that, in Mg-Al-O inclusions, the elements of Mn, Si, and S coexist, and their central mole ratio of Mg/Al varies in a wide range. This value for most inclusions is larger than 0.5, which suggests the formation of solid solution between MgAl2O4 and MgO. After etching, the typical microstructure of intragranular acicular ferrites is observed, which is due to the nucleation effect induced by Mg-Al-O inclusions. From the SEM-EDS mapping images, it is found that the element of sulfur accumulates on the periphery of nucleation inclusion. Moreover, line EDS analysis hints that Mn-depletion zone (MDZ) exists in steel matrix, which is adjacent to the complex inclusion. Combined with the theoretical analysis, this phenomenon can be explained by the absorption of Mn due to the magnesium vacancy in MgAl2O4, and this MDZ promotes the nucleation of intragranular acicular ferrite. Through statistical analysis of SEM images for microstructure, the probabilistic nature of inducing nucleation effect is revealed. These results may be helpful to clarify the nature of oxide metallurgy. Kong Hui, Zhou YaHui, Lin Hao, Xia Yunjin, Li Jie, Yue Qiang, and Cai ZhengYu Copyright © 2015 Kong Hui et al. All rights reserved. Experimental Research for the Application of Mining Waste in the Trench Cutting Remixing Deep Wall Method Sun, 01 Feb 2015 12:53:19 +0000 This paper focuses on the use of fly ash (FA) or ground granulated blast slag (GGBS) and reactive lime blends for cement-stabilized Nanjing clay, comparing them with Portland cement (PC) for enhanced technical performance. A range of tests were conducted to investigate the properties of stabilized soils, including macrostrength (UCS), permeability, and microstructure analyses by scanning electron microscopy (SEM). The influence of PC : (FA + lime) ratio, PC : (GGBS + lime) ratio and curing time was addressed. The UCS and permeability results revealed that PC-FA-lime was more efficient than PC-GGBS-lime as a binder for soil stabilization, with an optimum proportion of PC : (FA + lime) = 3 : 7 at 25% binder content, varying with curing time. The microstructure analysis reveals that fly ash mainly changes the pore volume distribution, which ranges between 0.01 μm and 1 μm, and produces more CSH/CASH bonding and fissures due to the secondary hydration and pozzolanic reactions. Based on the favourable results obtained, it can be concluded that the soft soils can be successfully stabilized by the combined action of cement, fly ash, and lime. Since fly ash is much cheaper than cement, the addition of fly ash and lime in cement-soil mix may particularly become attractive and can result in cost reduction of construction. Yan Chao, Liu Songyu, and Deng Yongfeng Copyright © 2015 Yan Chao et al. All rights reserved. TiC0.5N0.5-Based Cermets with Varied Amounts of Si3N4 Nanopowders Prepared by Spark Plasma Sintering Sun, 01 Feb 2015 12:14:05 +0000 TiCN-based cermets with varied fractions of Si3N4 nanopowder (0–5 wt.%) were prepared by spark plasma sintering. The microstructural and mechanical properties of these cermets were investigated. In general, with increasing addition amount of Si3N4 nanopowder the relative density as well as mechanical properties of the as-prepared TiCN cermets increased first and then decreased. The samples containing 2 wt.% Si3N4 nanopowder presented the best performance with the relative density of about 98%, bending strength of 1000 MPa, and Vickers microhardness of about 1810 HV10. Changchun Lv, Zhijian Peng, Zhiqiang Fu, and Chengbiao Wang Copyright © 2015 Changchun Lv et al. All rights reserved. Effect of Pore Size on the Biodegradation Rate of Silk Fibroin Scaffolds Sun, 01 Feb 2015 09:35:45 +0000 Controlling the degradation rate of silk fibroin-based biomaterial is an important capability for the fabrication of silk-based tissue engineering scaffolds. In this study, scaffolds with different pore sizes were prepared by controlling the freezing temperature and the silk fibroin concentration. In vitro degradation results showed that the internal pore walls of the scaffolds with a larger pore size collapsed upon exposure to collagenase IA for times ranging from 6 to 12 days, and the silk scaffolds exhibited a faster rate of weight loss. The morphological and structural features of the silk scaffolds with a smaller pore size maintained structural integrity after incubation in the protease solution for 18 days, and the rate of weight loss was relatively slow. Scaffolds with a smaller pore size or a higher pore density degraded more slowly than scaffolds with a larger pore size or lower pore density. These results demonstrate that the pore size of silk biomaterials is crucial in controlling the degradation rate of tissue engineering scaffolds. Zuwei Luo, Qin Zhang, Meijing Shi, Yang Zhang, Wei Tao, and Mingzhong Li Copyright © 2015 Zuwei Luo et al. All rights reserved. Temperature and pH Responsive Microfibers for Controllable and Variable Ibuprofen Delivery Thu, 29 Jan 2015 09:01:31 +0000 Electrospun microfibers (MFs) composed of pH and temperature responsive polymers can be used for controllable and variable delivery of ibuprofen. First, electrospinning technique was employed to prepare poly(ε-caprolactone) (PCL) and poly(N-isopropylacrylamide-co-methacrylic acid) (pNIPAM-co-MAA) MFs containing ibuprofen. It was found that drug release rates from PCL MFs cannot be significantly varied by either temperature (22–40°C) or pH values (1.7–7.4). In contrast, the ibuprofen (IP) diffusion rates from pNIPAM-co-MAA MFs were very sensitive to changes in both temperature and pH. The IP release from pNIPAM-co-MAA MFs was highly linear and controllable when the temperature was above the lower critical solution temperature (LCST) of pNIPAM-co-MAA (33°C) and the pH was lower than the of carboxylic acids (pH 2). At room temperature, however, the release rate was dramatically increased by nearly ten times compared to that at higher temperature and lower pH. Such a unique and controllable drug delivery system could be naturally envisioned to find many practical applications in biomedical and pharmaceutical sciences such as programmable transdermal drug delivery. Toan Tran, Mariana Hernandez, Dhruvil Patel, and Ji Wu Copyright © 2015 Toan Tran et al. All rights reserved. Synthesis of Micro- and Nanoparticles of Metal Oxides and Their Application for Reinforcement of Al-Based Alloys Wed, 28 Jan 2015 09:54:47 +0000 This paper presents a comparative analysis of morphology, chemical and phase compositions, and particle size distribution of nanopowders produced by electric explosion of wire (EEW) and plasma-chemical methods. The possibility of introduction of Al2O3 particles into Al alloy by means of a special master alloy and with ultrasonic processing is shown. The improvement of tensile properties of an Al-based composite material reinforced with 0.1 wt% of EEW Al2O3 is demonstrated. S. Vorozhtsov, I. Zhukov, A. Vorozhtsov, A. Zhukov, D. Eskin, and A. Kvetinskaya Copyright © 2015 S. Vorozhtsov et al. All rights reserved. Effect of Nanosized NiF2 Addition on the Transport Critical Current Density of Ag-Sheathed (Bi1.6Pb0.4)Sr2Ca2Cu3O10 Superconductor Tapes Wed, 28 Jan 2015 09:40:20 +0000 We report the effect of NiF2 (10 nm) additions on the transport critical current density, of (Bi1.6Pb0.4)Sr2Ca2Cu3O10/Ag sheathed superconductor tapes. Pellets of (Bi1.6Pb0.4)Sr2Ca2Cu3O10(NiF2)x (–0.05 wt.%) superconductor were prepared using the acetate coprecipitation method. The sample with 0.04 wt.% addition of NiF2 exhibited the highest . Ag-sheathed (Bi1.6Pb0.4)Sr2Ca2Cu3O10(NiF2)0.04 superconductor tapes were fabricated using the powder-in-tube (PIT) method and sintered at 845°C for 50 and 100 h. of nonadded tapes at 30 K sintered for 50 and 100 h was 6370 and 8280 A/cm2, respectively. of (Bi1.6Pb0.4)Sr2Ca2Cu3O10(NiF2)0.04/Ag tape at 30 K sintered for 50 and 100 h was 14390 and 17270 A/cm2, respectively. In magnetic fields (0 to 0.7 T), of the NiF2 added tapes was also higher compared with the nonadded tape indicating that NiF2 nanoparticles can act as effective flux pinning centers and longer sintering time improved the microstructure. A steeper increase in was observed below 60 K in the NiF2 added tapes which coincided with the Neel temperature, of nanosized NiF2 (60 K). The pronounced enhancement of was attributed to the strong interaction between flux line network and the antiferromagnetic NiF2 below . M. Hafiz and R. Abd-Shukor Copyright © 2015 M. Hafiz and R. Abd-Shukor. All rights reserved. Computational Approach in Formulating Mechanical Characteristics of 3D Star Honeycomb Auxetic Structure Tue, 27 Jan 2015 08:54:46 +0000 Auxetic materials exhibit a unique characteristic due to the altered microstructure. Different structures have been used to model these materials. This paper treats a development of finite element model and theoretical formulation of 3D star honeycomb structure of these materials. Various shape parameters of the structural cell were evaluated with respect to the basic mechanical properties of the cell. Finite element and analytical approach for various geometrical parameters were numerically used to formulate the characteristics of the material. The study aims at quantifying mechanical properties for any domain in which auxetic material is of interest for variations in geometrical parameters. It is evident that mechanical properties of the material could be controlled by changing the base wall angle of the configuration. The primary outcome of the study is a design guideline for the use of 3D star honeycomb auxetic cellular structure in structural applications. Mozafar Shokri Rad, Zaini Ahmad, and Amran Alias Copyright © 2015 Mozafar Shokri Rad et al. All rights reserved. Ostwald Ripening Process of Coherent β′ Precipitates during Aging in Fe0.75Ni0.10Al0.15 and Fe0.74Ni0.10Al0.15Cr0.01 Alloys Tue, 27 Jan 2015 06:56:26 +0000 The Ostwald ripening process was studied in Fe0.75Ni0.10Al0.15 and Fe0.74Ni0.10Al0.15Cr0.01 alloys after aging at 750, 850, and 950°C for different times. The microstructural evolution shows a rounded cube morphology (Fe, Ni)Al β′ precipitates aligned in the ferrite matrix, which changes to elongated plates after prolonged aging. The variation of the equivalent radii of precipitates with time follows the modified Lifshitz-Slyozov-Wagner theory for diffusion-controlled coarsening. Thermo-Calc analysis shows that the chromium content is richer in the matrix than in the precipitates which causes higher hardness and coarsening resistance in the aged Fe0.74Ni0.10Al0.15Cr0.01 alloy. N. Cayetano-Castro, M. L. Saucedo-Muñoz, H. J. Dorantes-Rosales, Jorge L. Gonzalez-Velazquez, J. D. Villegas-Cardenas, and V. M. Lopez-Hirata Copyright © 2015 N. Cayetano-Castro et al. All rights reserved. Magnetic Properties and Core Loss Behavior of Fe-6.5wt.%Si Ribbons Prepared by Melt Spinning Mon, 26 Jan 2015 14:31:48 +0000 Fe-6.5wt.%Si alloy is prepared in the form of continuous ribbons with 25 mm in width and 0.03 mm in thickness by using melt spinning technique. The ribbons are flexible and could be wounded into tapes. DC magnetic properties and core loss behaviors of the ribbons after heat treatment are investigated in this paper. The magnetic properties are compared with ribbons by cold rolling and CVD methods. The melt spinning ribbons exhibit much less core loss in the frequencies more than 10 kHz. The melt spinning ribbons are promising to be used for electric devices used in medium or higher frequencies. S. Wang, Y. M. Jiang, Y. F. Liang, F. Ye, and J. P. Lin Copyright © 2015 S. Wang et al. All rights reserved. Correlation of Grain Size, Stacking Fault Energy, and Texture in Cu-Al Alloys Deformed under Simulated Rolling Conditions Mon, 26 Jan 2015 13:07:27 +0000 The effect of grain size and stacking fault energy (SFE) on the strain hardening rate behavior under plane strain compression (PSC) is investigated for pure Cu and binary Cu-Al alloys containing 1, 2, 4.7, and 7 wt. % Al. The alloys studied have a wide range of SFE from a low SFE of 4.5 mJm−2 for Cu-7Al to a medium SFE of 78 mJm−2 for pure Cu. A series of PSC tests have been conducted on these alloys for three average grain sizes of ~15, 70, and 250 m. Strain hardening rate curves were obtained and a criterion relating twinning stress to grain size is established. It is concluded that the stress required for twinning initiation decreases with increasing grain size. Low values of SFE have an indirect influence on twinning stress by increasing the strain hardening rate which is reflected in building up the critical dislocation density needed to initiate mechanical twinning. A study on the effect of grain size on the intensity of the brass texture component for the low SFE alloys has revealed the reduction of the orientation density of that component with increasing grain size. Ehab A. El-Danaf, Mahmoud S. Soliman, and Ayman A. Al-Mutlaq Copyright © 2015 Ehab A. El-Danaf et al. All rights reserved.