Advances in Materials Science and Engineering The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Influence of Molybdenum Content and MoO Species on the Textural and Structural ZrO2 Properties Thu, 18 Dec 2014 13:28:46 +0000 The present work proposes to study the incorporation of molybdenum into the zirconium oxide precursor (Zr(OH)4), in order to analyze its possible repercussions on the textural and structural zirconia properties (ZrO2). For this, the Zr(OH)4 was synthesized by the sol-gel method and modified with 5, 10, and 15 wt% of molybdenum into the stabilized oxide. The synthesized materials were dried at 120°C for 24 h and then were calcined at 600°C for 3 h. The characterization of the solids was carried out by thermal analysis, X-ray diffraction, nitrogen physisorption, infrared spectroscopy, and scanning electron microscopy. The thermal analyses results showed that the change from the amorphous to the crystalline phase of ZrO2 is shifted to higher temperatures due to the presence of molybdenum content. Tetragonal phase was identified for all synthesized materials, showing a decrease in crystallinity as a function of the metal content. The textural properties were improved due to the incorporation of molybdenum into the ZrO2 structure, developing specific surface areas which are above up to four times the area of pure ZrO2. The synthesized materials presented spherical morphology with particle sizes less than 1 µm, with a change of this morphology for high metal contents (15 wt%) being observed. Alberto Hernández Zapién, Juan Manuel Hernández Enríquez, Ricardo García Alamilla, Guillermo Sandoval Robles, Ulises Páramo García, and Luz Arcelia García Serrano Copyright © 2014 Alberto Hernández Zapién et al. All rights reserved. Novel Technologies and Applications for Construction Materials Thu, 18 Dec 2014 11:28:15 +0000 Gonzalo Martínez-Barrera, Osman Gencel, João Marciano Laredo dos Reis, and Juan José del Coz Díaz Copyright © 2014 Gonzalo Martínez-Barrera et al. All rights reserved. Experimental Investigation of the Variation of Concrete Pores under the Action of Freeze-Thaw Cycles by Using X-Ray CT Thu, 18 Dec 2014 00:11:02 +0000 The variation of concrete pores under the action of freeze-thaw cycles was investigated experimentally by using the X-ray CT. Firstly, the statistical characteristics of pores of concrete specimens were obtained by using the X-ray image analysis. Secondly, the variation of porosity and pore volume of concrete pores were analyzed and discussed by comparing with above characteristics. Thirdly, the failure process of the concrete specimens acted by the freeze-thaw cycles was investigated by scanning the interior of concrete specimens. The results showed that the pore volumes of concrete pores whose volumes were located at the interval [0.5 mm3, 20 mm3] have no big variation in both the amounts and volume of concrete pores, while others were found to have huge change during the process of experiment. The extent of damage acted by the repeated freezing and thawing gradually ranged from surface to complete disintegration of the interior of concrete specimens after 30 cycles of freeze-thaw acting. Jie Yuan, Yang Liu, Hongxia Li, and Baokun Zhang Copyright © 2014 Jie Yuan et al. All rights reserved. Influence of Sc on Microstructure and Mechanical Properties of High Zn-Containing Mg Alloy Thu, 18 Dec 2014 00:11:00 +0000 Microstructures and mechanical properties of Mg-11Zn and Mg-11Zn-1Sc (wt%) alloys were investigated. The main secondary phase of Mg-11Zn and Mg-11Zn-1Sc alloys is MgZn2 phase. Rare earth Sc element is an effective grain refiner and the grain size of Mg-11Zn-1Sc alloy is greatly refined. The mechanical properties of the Mg-11Zn alloy were greatly improved with incorporation of 1 wt% Sc, especially for the elevated temperature strength. Such mechanical property enhancement is ascribed to the refinement and pinning mechanism of high heat-resistant Sc and Sc-containing intermetallic particles in Mg alloy. Lidong Wang, Jie Yang, Limin Wang, and Zhanyi Cao Copyright © 2014 Lidong Wang et al. All rights reserved. Synthesis and Dimerization Behavior of Five Metallophthalocyanines in Different Solvents Thu, 18 Dec 2014 00:10:58 +0000 Metallophthalocyanine (MPc) has become one of the metal organic compounds with the largest production and the most widely application, because of its excellent performance in catalytic oxidation. However, aggregation of the MPc in solution, resulting in decreased solubility, greatly limits the performance of application. Studying the behavior of dimerization of MPcs can provide a theoretical basis for solving the problem of the low solubility. So five metallophthalocyanines (FePc, CoPc, NiPc, CuPc, and ZnPc) were prepared with improved method and characterized. Dimerization of the five MPcs was measured by UV-Vis spectroscopy separately in N,N-dimethyl formamide (DMF) and dimethylsulfoxide (DMSO). The red-shift of maximum absorption wavelength and deviations from Lambert-Beer law with increasing the concentration were observed for all the five MPcs. The dimerization equilibrium constants (K) of the five MPcs in DMF were arranged in order of CoPc > ZnPc > CuPc > FePc > NiPc, while in DMSO they were arranged in order of ZnPc > CoPc > FePc > CuPc > NiPc. The type of the central metal and nature of the solvent affect the dimerization of the MPcs. Zhenhua Cheng, Na Cui, Hongxiao Zhang, Lijun Zhu, and Daohong Xia Copyright © 2014 Zhenhua Cheng et al. All rights reserved. Experimental Investigation on Use of Wheat Straw Ash and Bentonite in Self-Compacting Cementitious System Wed, 17 Dec 2014 00:10:47 +0000 In this research, we evaluated the feasibility of wheat straw ash and bentonite (raw and heated at 150°C for 8 hrs) as secondary raw materials in self-compacting paste (SCP). The fresh and hardened properties of SCP formulations including water and superplasticizer demand, flow behavior, compressive and flexural strength development, water absorption, and acid attack resistance were evaluated. Moreover, porosity, microstructural, and mineralogical investigations were also carried out on SCP formulations. Test results showed that the properties of SCP formulations in fresh state depend on the morphology of secondary raw materials. For heated bentonite and wheat straw ash formulations, the 28 days of compressive and flexural strength were higher or almost similar to reference SCP formulation. Among SCP formulations, wheat straw ash formulation was found to be more effective in consuming free lime and showed significant decrease in porosity with time, which in turn improved the resistance of this SCP formulation against water absorption and acid attack. Based on the test results, it can be concluded that the successful utilization of wheat straw ash and bentonite SCP formulations will offer durable and environmental friendly option to construction industry. Rao Arsalan Khushnood, Syed Ali Rizwan, Shazim Ali Memon, Jean-Marc Tulliani, and Giuseppe Andrea Ferro Copyright © 2014 Rao Arsalan Khushnood et al. All rights reserved. Utilization of Recycled Concrete Aggregates in Stone Mastic Asphalt Mixtures Wed, 17 Dec 2014 00:10:44 +0000 Recycled concrete aggregate (RCA) is considered as one of the largest wastes in the entire world which is produced by demolishing concrete structures such as buildings, bridges, and dams. It is the intention of scientists and researchers, as well as people in authority, to explore waste material recycling for environmental and economic advantages. The current paper presents an experimental research on the feasibility of reusing RCA in stone mastic asphalt (SMA) mixtures as a partial replacement of coarse and fine aggregates. The engineering properties of SMA mixtures containing RCA have been evaluated for different percentages of binders based on the Marshall mix design method. The outcomes were statistically analyzed using two-factor analysis of variance (ANOVA). Test results revealed that the performance of SMA mixtures is affected by RCA due to higher porosity and absorption of RCA in comparison with virgin granite aggregates. However, the engineering properties of SMA mixtures containing a particular amount of RCA showed the acceptable trends and could satisfy the standard requirements. Moreover, to achieve desirable performance characteristics, more caution should be made on properties of SMA mixtures containing RCA. Mohammad Saeed Pourtahmasb and Mohamed Rehan Karim Copyright © 2014 Mohammad Saeed Pourtahmasb and Mohamed Rehan Karim. All rights reserved. Performance Analysis of γ-Radiation Test Monitor Using Monocrystalline n+pp++ Silicon Solar Cell: CsI(Tl) Scintillator Mon, 15 Dec 2014 12:47:55 +0000 The silicon solar cells are largely insensitive to gamma-radiation because the radiation passes through solar cells without imparting all of its energy. In order to enhance the sensitivity to radiation, the solar cells are coupled to CsI(Tl) scintillator. With the help of n+pp++ PESC monocrystalline silicon solar cells and CsI(Tl) scintillators, a gamma-radiation test monitor (TM) is developed. Due to safety concerns, a convenience relatively intense 60Co gamma-source is used as a suitable substitute for spent fuel. Two designs made of two representative arrays of monocrystalline solar cells are suggested. The induced current and voltage generated by these solar cells are measured. The temperature dependence of the induced current and the angular characteristic of the TM, for both designs, are presented. In comparison to conventional gamma-ray sensors, the Si solar cells exhibited better performance than the conventional types. Design II is found to be more efficient than I and superior performance for all of the measured parameters is obtained. Ali Abd El-Salam Ibrahim and Mostafa Abd El-Fattah El-Aasser Copyright © 2014 Ali Abd El-Salam Ibrahim and Mostafa Abd El-Fattah El-Aasser. All rights reserved. Experimental Research on Compression Properties of Cement Asphalt Mortar due to Drying and Wetting Cycle Sun, 14 Dec 2014 00:11:03 +0000 Uniaxial compression test of cement asphalt (CA) mortar specimens, due to drying and wetting cycle of 0, 2, 4 and 8 times, is carried out by using the electronic universal test machine, with the strain rate ranging from 1 × 10−5 s−1 to 1 × 10−2 s−1. The effects of strain rate and drying and wetting cycle time on the compressive strength, elasticity modulus, and stress-strain full curve are investigated. Experimental results show that the strain-stress full curve of CA mortar is affected obviously by strain rate and drying and wetting cycle time. The compressive strength and elasticity modulus increase with the strain rate under the same drying and wetting cycle time. The compressive strength and elasticity modulus decrease with the increase of drying and wetting cycle time in the same strain rate. The lower the strain rate is, the greater the compressive strength and elasticity modulus of CA mortar decrease. When the strain rate is 1 × 10−5 s−1 and drying and wetting cycle time is 8, the largest reduction of average compressive strength of CA mortar is 40.48%, and the largest reduction of elasticity modulus of CA mortar is 35.51%, and the influence of drying and wetting cycle on the compressive strength of CA mortar is greater than its influence on the elasticity modulus. Ping Wang, Hao Xu, Rong Chen, Jingmang Xu, and Xiaohui Zeng Copyright © 2014 Ping Wang et al. All rights reserved. Phytoremediation Potential of Vetiver System Technology for Improving the Quality of Palm Oil Mill Effluent Thu, 11 Dec 2014 08:53:01 +0000 Palm oil mill effluent (POME), a pollutant produced by the palm oil industry, was treated by the Vetiver system technology (VST). This technology was applied for the first time to treat POME in order to decrease biochemical oxygen demand (BOD) and chemical oxygen demand (COD). In this study, two different concentrations of POME (low and high) were treated with Vetiver plants for 2 weeks. The results showed that Vetiver was able to reduce the BOD up to 90% in low concentration POME and 60% in high concentration POME, while control sets (without plant) only was able to reduce 15% of BOD. The COD reduction was 94% in low concentration POME and 39% in high concentration POME, while control just shows reduction of 12%. Morphologically, maximum root and shoot lengths were 70 cm, the number of tillers and leaves was 344 and 86, and biomass production was 4.1 kg m−2. These results showed that VST was effective in reducing BOD and COD in POME. The treatment in low concentration was superior to the high concentration. Furthermore, biomass of plant can be considered as a promising raw material for biofuel production while high amount of biomass was generated in low concentration of POME. Negisa Darajeh, Azni Idris, Paul Truong, Astimar Abdul Aziz, Rosenani Abu Bakar, and Hasfalina Che Man Copyright © 2014 Negisa Darajeh et al. All rights reserved. The Increased Production Efficiency and Optimization Terms of Stationarity by Flat Grinding with Abrasive Circle Surface Thu, 11 Dec 2014 00:10:40 +0000 This scientific work deals with the production area. The paper investigates the problems related to the uneven abrasive effect on the processed surface by flat grinding with the abrasive circle surface, and the analytical expression of pattern distribution of the working abrasive grain within the limits of various technological primitives and inaccuracy of geometric shape have been determined. The ways of stationary provision of the grinding surface have been suggested. This paper also focuses on the economic efficiency of the production. Husseinov Hassan Ahmad, Bagirov Sahib Abbas, Radoslav Kreheľ, and Marek Kočiško Copyright © 2014 Husseinov Hassan Ahmad et al. All rights reserved. Thermal Characteristics of Multilayer Insulation Materials for Flexible Thin-Film Solar Cell Array of Stratospheric Airship Tue, 09 Dec 2014 00:10:26 +0000 Flexible thin-film solar cell is an efficient energy system on the surface of stratospheric airship for utilizing the solar energy. In order to ensure the normal operation of airship platform, the thermal control problem between the flexible thin-film solar cell and the airship envelope should be properly resolved. In this paper, a multilayer insulation material (MLI) is developed first, and low temperature environment test is carried out to verify the insulation effect of MLI. Then, a thermal heat transfer model of flexible thin-film solar cell and MLI is proposed, and the equivalent thermal conductivity coefficients of flexible thin-film solar cell and Nomex honeycomb are calculated based on the environment test and the temperature profile of flexible thin-film solar cell versus each layer of MLI. Finally, FLUENT is used for modeling and simulation analysis on the flexible thin-film solar cell and MLI, and the simulation results agree well with the experimental data, which validate the correctness of the proposed heat transfer model of MLI. In some way, our study can provide helpful support for further engineering applications of flexible thin-film solar cell. Kangwen Sun, Qinzhen Yang, Yang Yang, Shun Wang, Jianming Xu, Qiang Liu, Yong Xie, and Peng Lou Copyright © 2014 Kangwen Sun et al. All rights reserved. Predicting Concrete Compressive Strength and Modulus of Rupture Using Different NDT Techniques Thu, 04 Dec 2014 12:28:47 +0000 Quality tests applied to hydraulic concrete such as compressive, tension, and bending strength are used to guarantee proper characteristics of materials. All these assessments are performed by destructive tests (DTs). The trend is to carry out quality analysis using nondestructive tests (NDTs) as has been widely used for decades. This paper proposes a framework for predicting concrete compressive strength and modulus of rupture by combining data from four NDTs: electrical resistivity, ultrasonic pulse velocity, resonant frequency, and hammer test rebound with DTs data. The model, determined from the multiple linear regression technique, produces accurate indicators predictions and categorizes the importance of each NDT estimate. However, the model is identified from all the possible linear combinations of the available NDT, and it was selected using a cross-validation technique. Furthermore, the generality of the model was assessed by comparing results from additional specimens fabricated afterwards. Wilfrido Martínez-Molina, Andrés Antonio Torres-Acosta, Juan Carlos Jáuregui, Hugo Luis Chávez-García, Elia Mercedes Alonso-Guzmán, Mario Graff, and Juan Carlos Arteaga-Arcos Copyright © 2014 Wilfrido Martínez-Molina et al. All rights reserved. Effect of Liquid Phase Additions on Microstructure and Thermal Properties in Copper and Copper-Diamond Composites Wed, 03 Dec 2014 00:10:21 +0000 This study details a new approach to creating copper-diamond composite materials for thermal management applications by using a two-phase (solid-liquid) approach in powder metallurgy using Field Assisted Sintering Technology (FAST). Silver-copper alloyed powder at eutectic compositions was used as a nonreactive liquid phase while Cu5Si was used as a reactive liquid phase. Microstructure results are reported favorably comparing the additions of a small amount of liquid phase to pure solid state sintering. Additionally, EDX results indicate that the liquid phase material fills gaps at the interface of the matrix and diamond particle resulting in improved microstructure and density. Thermal conductivity results show that liquid phase additions improve the thermal conductivity of composites compared to composites without any liquid phase, but Si additions cause a severe drop in baseline conductivity. A. Rape, X. Liu, A. Kulkarni, and J. Singh Copyright © 2014 A. Rape et al. All rights reserved. Dielectric Behaviour of Zn/Al-NO3 LDHs Filled with Polyvinyl Chloride Composite at Low Microwave Frequencies Wed, 03 Dec 2014 00:10:19 +0000 Recently, researchers have shown great interest in improving the thermal, mechanical, dielectric, and microwave properties of pure polymers through the use of polymer-based composites. The essential properties of polymer-based composites can be modified by varying the amount of Zn/Al-NO3 layered double hydroxide (LDH) added to polyvinyl chloride (PVC). Therefore, by determining the optimal ratio of LDH in the PVC matrix, the dielectric properties of PVC-LDH composites can be improved. An LDH was prepared using the coprecipitation method, while PVC-LDH composites were prepared using tetrahydrofuran (THF) as the solvent. The composites were characterised using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), and room temperature dielectric measurements were investigated using an RF Impedance/Material Analyzer (Agilent 4291). The results confirmed that the prepared composites were pure. Additionally, the presence of LDH in the PVC matrix was verified. The dielectric measurements showed that an increase in the LDH concentration leads to an increase in the dielectric constant and the dielectric loss factor. When used as dielectric filler in the PVC matrix, the LDH improved the dielectric properties of the fabricated composites. The results indicate that these composites show great potential for use as microwave absorbers at low microwave frequencies. Ethar Y. Salih, Zulkifly Abbas, Samer Hasan Hussein Al Ali, and Mohd Zobir Hussein Copyright © 2014 Ethar Y. Salih et al. All rights reserved. Reducing Railway Noise with Porous Sound-Absorbing Concrete Slabs Sun, 30 Nov 2014 07:41:23 +0000 The effect of porous sound-absorbing concrete slabs on railway noise reduction is examined in this paper. First, the acoustical absorption coefficients of porous concrete materials with various aggregate types, gradations, fibre contents, and compaction indexes are measured in the laboratory. The laboratory results show that porous concrete that uses a composite of expanded perlite and slag as aggregate can not only obtain good acoustical absorption properties but also satisfy mechanical requirements. Also, the gradation of the combined aggregate has a significant effect on the acoustic absorption performance of the porous concrete, with an optimal aggregate gradation of 1~3 mm. Furthermore, the fibre content and compaction index affect both the strength and the acoustic absorption property of the porous concrete, with the optimum value of 0.3% and 1.6, respectively. Then, the findings from the laboratory studies are used to make porous sound-absorbing concrete slabs, which are applied in a test section. The measurements indicate that porous sound-absorbing concrete slabs can significantly reduce railway noise at different train speeds and that the amount of the noise reduction changes roughly linearly with speed when the train is traveling at less than 200 km/h. The maximum noise reduction is 4.05 dB at a speed of 200 km/h. Caiyou Zhao, Ping Wang, Li Wang, and Dan Liu Copyright © 2014 Caiyou Zhao et al. All rights reserved. Influence of the Molecular Adhesion Force on the Indentation Depth of a Particle into the Wafer Surface in the CMP Process Tue, 25 Nov 2014 17:20:43 +0000 By theoretical calculation, the external force on the particle conveyed by pad asperities and the molecular adhesion force between particle and wafer are compared and analyzed quantitatively. It is confirmed that the molecular adhesion force between particle and wafer has a great influence on the chemical mechanical polishing (CMP) material removal process. Considering the molecular adhesion force between particle and wafer, a more precise model for the indentation of a particle into the wafer surface is developed in this paper, and the new model is compared with the former model which neglected the molecular adhesion force. Through theoretical analyses, an approach and corresponding critical values are applied to estimate whether the molecular adhesion force in CMP can be neglected. These methods can improve the precision of the material removal model of CMP. Zhou Jianhua, Jiang Jianzhong, and He Xueming Copyright © 2014 Zhou Jianhua et al. All rights reserved. Influence of Grain Size and Texture on the Yield Strength of Mg Alloys Processed by Severe Plastic Deformation Tue, 25 Nov 2014 13:07:33 +0000 Severe plastic deformation (SPD) has been widely employed to refine the grain size of Mg alloys, with the main objective to improve the strength and ductility of Mg alloys, since the well-known Hall-Petch equation suggests that a decreased grain size leads to an increased yield strength. However, the yield strength of Mg alloys processed by SPD is often decreased even though the grain size is effectively reduced. The abnormal flow behavior in Mg alloys processed by SPD has attracted great attention although this mechanism is still unclear, due to its complex and extensive influence factors. In this paper, the relationships between the processing conditions, grain refinement, and mechanical properties of the SPD treated Mg alloys are reviewed, with the emphasis on the effects of grain size and texture on the yield strength. Jinbao Lin, Weijie Ren, Qudong Wang, Lifeng Ma, and Yongjun Chen Copyright © 2014 Jinbao Lin et al. All rights reserved. Temperature Effect on Mechanical Properties and Damage Identification of Concrete Structure Tue, 25 Nov 2014 00:00:00 +0000 Static and dynamic mechanical properties of concrete are affected by temperature effect in practice. Therefore, it is necessary to investigate the corresponding influence law and mechanism. This paper demonstrates the variation of mechanical properties of concrete at temperatures from −20°C to 60°C. Temperature effects on cube compressive strength, splitting tensile strength, prism compressive strength, modulus of elasticity, and frequency are conducted and discussed. The results indicate that static mechanical properties such as compressive strength (cube and prism), splitting tensile strength, and modulus of elasticity have highly linear negative correlation with temperature; this law is also applied to the first order frequency of concrete slab. The coupling effect of temperature and damage on change rate of frequency reveals that temperature effect cannot be ignored in damage identification of structure. Mechanism analysis shows that variation of elastic modulus of concrete caused by temperature is the primary reason for the change of frequency. Yubo Jiao, Hanbing Liu, Xianqiang Wang, Yuwei Zhang, Guobao Luo, and Yafeng Gong Copyright © 2014 Yubo Jiao et al. All rights reserved. Preparation and Characterization of Cetyl Trimethylammonium Intercalated Sericite Mon, 24 Nov 2014 07:02:25 +0000 Intercalated sericite was prepared by intercalation of cetyl trimethylammonium bromide (CTAB) into activated sericite through ion exchange with the following two steps: the activation of sericite by thermal modification, acid activation and sodium modification; the ion exchange intercalation of CTA+ into activated sericite. Effects of reaction time, reaction temperature, CTAB quantity, kinds of medium, and aqueous pH on the intercalation of activated sericite were examined by X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The results indicated that the CTA+ entered sericite interlayers and anchored in the aluminosilicate interlayers through strong electrostatic attraction. The arrangement of CTA+ in sericite interlayers was that alkyl chain of CTA+ mainly tilted at an angle about 60° (paraffin-type bilayer) and 38° (paraffin-type monolayer) with aluminosilicate layers. The largest interlayer space was enlarged from 0.9 nm to 5.2 nm. The intercalated sericite could be used as an excellent layer silicate to prepare clay-polymer nanocomposites. Hao Ding, Yuebo Wang, Yu Liang, and Faxiang Qin Copyright © 2014 Hao Ding et al. All rights reserved. A Study on the Effect of the Boron Potential on the Mechanical Properties of the Borided Layers Obtained by Boron Diffusion at the Surface of AISI 316L Steel Mon, 24 Nov 2014 00:00:00 +0000 The effect of the boron potential on the thickness and the mechanical properties of borided layers was evaluated. The boron potential was established by means of the available atoms of boron contained in a control volume inside a cylinder. The cylinders were manufactured from AISI 316L steel, and the boriding treatment was performed using the powder pack technique at a temperature of 1273 K over an exposure time of 6 h. Four different internal diameters of the cylinders were evaluated (3.17, 4.76, 6.35, and 7.93 mm). The mechanical properties were evaluated using the Berkovich instrumented indentation technique. The results showed a clear influence of the boron potential on the mechanical properties of the layers. The hardness of the layers was stablished in the range of 16.22 to 21.16 GPa. Young’s modulus values were stablished in the range of 255.96 to 341.37 GPa. Also the fracture toughness and brittleness of the layers reflected the influence of the boron potential supplied during the boriding process. Finally, the influence of the boron potential on the constant of parabolic growth (K) was also established as a function of the inner diameter of the cylinders. E. Hernández-Sánchez, Y. M. Domínguez-Galicia, C. Orozco-Álvarez, R. Carrera-Espinoza, H. Herrera-Hernández, and J. C. Velázquez Copyright © 2014 E. Hernández-Sánchez et al. All rights reserved. Preparation of Al-Mg Alloy Electrodes by Using Powder Metallurgy and Their Application for Hydrogen Production Sun, 23 Nov 2014 08:16:14 +0000 The choice of an electrode is the most critical parameter for water electrolysis. In this study, powder metallurgy is used to prepare aluminum-magnesium (Al-Mg) alloy electrodes. In addition to pure Mg and Al electrodes, five Al-Mg alloy electrodes composed of Al-Mg (10 wt%), Al-Mg (25 wt%), Al-Mg (50 wt%), and Al-Mg (75 wt%) were prepared. In water electrolysis experiments, the pure Al electrode exhibited optimal electrolytic efficiency. However, the Al-Mg (25 wt%) alloy was the most efficient when the anticorrosion effect and materials costs were considered. In this study, an ultrasonic field was applied to the electrolysis cell to improve its efficiency. The results revealed that the current increased by approximately 23.1% when placed in a 30 wt% KOH solution under the ultrasonic field. Electrochemical polarization impedance spectroscopy (EIS) was employed to evaluate the effect of the ultrasonic field on the reduction of polarization resistance. The results showed that the concentration impedance in the 30 wt% KOH electrolyte decreased markedly by 44%–51% Ω. Wen-Nong Hsu, Teng-Shih Shih, and Ming-Yuan Lin Copyright © 2014 Wen-Nong Hsu et al. All rights reserved. Estimation of the Pumping Pressure from Concrete Composition Based on the Identified Tribological Parameters Sun, 23 Nov 2014 00:00:00 +0000 A new method is proposed to estimate pumping pressure based on concrete composition without experimental measurements. Previous studies show that the pumping pressure depends on the interface friction between concrete and the wall of the pumping pipes. This friction is determined by the thickness and the rheology of the boundary layer formed at the interface. The latter is mainly formed by water, cement, and fine sand particles which come from concrete. Hence, interface parameters, which are the viscous constant and the interface yield stress, are directly related to concrete composition. In this work, at the first time the interface yield stress model is suggested and validated thanks to an experimental database also carried out in this study with a precision of around 13%. Then, the pressure estimation method is proposed using the two models to calculate the interface parameters. The validation of the method is carried out basing on the comparison with real measurements on the building site. This method enables the calculation of the pumping pressure with a precision of around 15%. Chanh-Trung Mai, El-Hadj Kadri, Tien-Tung Ngo, Abdelhak Kaci, and Mustapha Riche Copyright © 2014 Chanh-Trung Mai et al. All rights reserved. The Impact of Traffic-Induced Bridge Vibration on Rapid Repairing High-Performance Concrete for Bridge Deck Pavement Repairs Wed, 19 Nov 2014 09:29:04 +0000 Based on forced vibration tests for high-performance concrete (HPC), the influence of bridge vibration induced by traveling vehicle on compressive strength and durability of HPC has been studied. It is concluded that 1 d and 2 d compressive strength of HPC decreased significantly, and the maximum reduction rate is 9.1%, while 28 d compressive strength of HPC had a slight lower with a 3% maximal drop under the action of two simple harmonic vibrations with 2 Hz, 3 mm amplitude, and 4 Hz, 3 mm amplitude. Moreover, the vibration had a slight effect on the compressive strength of HPC when the simple harmonic vibration had 4 Hz and 1 mm amplitude; it is indicated that the amplitude exerts a more prominent influence on the earlier compressive strength with the comparison of the frequency. In addition, the impact of simple harmonic vibration on durability of HPC can be ignored; this shows the self-healing function of concrete resulting from later hydration reaction. Thus, the research achievements mentioned above can contribute to learning the laws by which bridge vibration affects the properties of concrete and provide technical support for the design and construction of the bridge deck pavement maintenance. Wei Wang, Shuo Liu, Qizhi Wang, Wei Yuan, Mingzhang Chen, Xiaotian Hao, Shuai Ma, and Xuanyu Liang Copyright © 2014 Wei Wang et al. All rights reserved. Correlation between Electrochemical Impedance Spectroscopy and Structural Properties of Amorphous Tunisian Metanacrite Synthetic Material Mon, 17 Nov 2014 12:27:57 +0000 In the present work, we report the structural and electrochemical properties of metanacrite. Metanacrite is a synthetic material originated by heating (550°C) of a clay mineral (Tunisian nacrite) belonging to the kaolin group. The structure of the amorphous synthetic product was corroborated by X-ray diffraction (disappearing of nacrite peaks) and infrared spectroscopy (disappearing of Al–OH and water bands). The decomposition of the silicate framework was confirmed by transmission electron microscope (TEM). The obtained metanacrite synthetic material was also examined by electrochemical impedance spectroscopy (EIS). Accordingly, the electronic conduction is followed by the correlated barrier hopping (C.B.H.) model. Therefore, by combining ac and dc electrical conductivity, a semiconductor behavior is evidenced. The dependence of the dielectric constant () and dielectric loss () on both temperature and frequency is also discussed. Nouha Jaafar, Hafsia Ben Rhaiem, and Abdessalem Ben Haj Amara Copyright © 2014 Nouha Jaafar et al. All rights reserved. A Novel Sintered Stainless Steel Fiber Felt with Rough Surface Morphologies Thu, 13 Nov 2014 11:23:53 +0000 A novel sintered stainless steel fiber felt (SSSFF) with rough surface morphologies and high strength as well as high porosity is fabricated by solid-state sintering of stainless steel fibers produced by cutting method. The rough surface morphologies are characterized by laminar and jagged structures formed on the surface of stainless steel fibers. The SSSFF with 85% porosity sintered at 1200°C for 60 min exhibits tensile strength of 19 MPa and yield stress of 10.5 MPa. The influence of sintering parameters on surface morphologies and tensile strength is investigated. The experimental results show that the rough surface structures will disappear gradually when sintering temperature is 1300°C or sintering time is excessive, that is, 240 min when sintering temperature is 1200°C. The SSSFF with high porosity presents high tensile strength when sintering temperature ranges from 1100°C to 1200°C and sintering time is from 60 min to 120 min. In addition, the fracture mechanism of the SSSFF is investigated when subjected to uniaxial tensile load. Chaobin Fang, Zhenping Wan, Bin Liu, and Longsheng Lu Copyright © 2014 Chaobin Fang et al. All rights reserved. Macroscopic and Microscopic Mechanisms of Cement-Stabilized Soft Clay Mixed with Seawater by Adding Ultrafine Silica Fume Thu, 13 Nov 2014 00:00:00 +0000 The strength of the cement-stabilized soil can be improved by the use of seawater. Compressive strength test results show that the strength of cement-stabilized soil mixed with seawater is 50% greater than that mixed with freshwater at the 90th day. However, the application is limited because the expansion of the cement-stabilized soil mixed with seawater increases significantly. A kind of ultrafine silica fume was added into the cement-stabilized soil to inhibit swelling of the cement-stabilized soil with seawater. The expansion of cement-stabilized soil mixed with seawater by adding ultrafine silica fume is close to that of cement-stabilized soil mixed with freshwater. With the addition of ultrafine silica fume, the unconfined compressive strength increases by close to 6.5% compared with seawater alone at the 90th day. The mechanisms of adding ultrafine silica fume into the cement-stabilized soil mixed with seawater are revealed by several physical and chemical characterization parameters, such as specific gravity, unbound water content, surface morphology seen with SEM, and crystal products by X-ray diffraction tests. The results show that the crystal growth is an important factor, affecting the strength and expansion of cement-stabilized soil mixed with seawater. Qiang Li, Jie Chen, Qian Shi, and Shihao Zhao Copyright © 2014 Qiang Li et al. All rights reserved. Review of Mechanics and Applications of Auxetic Structures Thu, 13 Nov 2014 00:00:00 +0000 One of the important mechanical properties of materials is Poisson’s ratio, which is positive for most of the materials. However, certain materials exhibit “auxetic” properties; that is, they have a negative Poisson’s ratio. Thus auxetic and non-auxetic materials exhibit different deformation mechanisms. A specific microscopic structure in the auxetic materials is important for maintaining a negative Poisson’s ratio. Based on their distinct nature auxetic materials execute certain unique properties in contrast to other materials, which are reviewed in this paper. Thus auxetic materials have important applications in the biomedical field which are also a part of this review article. Many auxetic materials have been discovered, fabricated, and synthesized which differ on the basis of structure, scale and deformation mechanism. The different types of auxetic materials such as auxetic cellular solids, microscopic auxetic polymers, molecular auxetic materials, and auxetic composites have been reviewed comprehensively in this paper. Modeling of auxetic structures is of considerable importance and needs appropriate stress strain configurations; thus different aspects of auxetic modeling have also been reviewed. Packing parameters and relative densities are of prime importance in this regard. This review would thus help the researchers in determining and deciding the various aspects of auxetic nature for their products. Mariam Mir, Murtaza Najabat Ali, Javaria Sami, and Umar Ansari Copyright © 2014 Mariam Mir et al. All rights reserved. A Study on Load Carrying Capacity of Fly Ash Based Polymer Concrete Columns Strengthened Using Double Layer GFRP Wrapping Wed, 12 Nov 2014 00:00:00 +0000 This paper investigates the suitability of glass fiber reinforced polymer (GFRP) sheets in strengthening of fly ash based polymer members under compression. Experimental results revealed that load carrying capacity of the confined columns increases with GFRP sheets wrapping. Altogether 18 specimens of M30 and G30 grade short columns were fabricated. The G30 specimens were prepared separately in 8 molarity and 12 molarity of sodium hydroxide concentration. Twelve specimens for low calcium fly ash based reinforced polymer concrete and six specimens of ordinary Portland cement reinforced concrete were cast. Three specimens from each molarity fly ash based reinforced polymer concrete and ordinary Portland cement reinforced concrete were wrapped with double layer of GFRP sheets. The load carrying capacity of fly ash based polymer concrete was tested and compared with control specimens. The results show increase in load carrying capacity and ductility index for all strengthened elements. The maximum increase in load carrying capacity was 68.53% and is observed in strengthened G30 specimens. S. Nagan and S. Karthiyaini Copyright © 2014 S. Nagan and S. Karthiyaini. All rights reserved. An Experimental Study on Strength and Durability for Utilization of Fly Ash in Concrete Mix Tue, 11 Nov 2014 12:07:00 +0000 The intention of this study is to discuss the variation of concrete exposed to high sulfate environment of a specific region with respect to strength and durability. Secondly, it is aimed to discuss the possibility of reducing the cement amount in construction of concrete structures. For this purpose, laboratory tests were conducted to investigate compressive strength and sulfate resisting capacity of concrete by using 20% fly ash as mineral additives, waste materials, instead of cement. As a case study the soil samples, received from Siirt Province areas which contain high sulfate rate, have been compared with respect to sulfate standard parameters of TS 12457-4. In such regions contact of underground water seep into hardened concrete substructures poses a risk of concrete deterioration. In order to determine the variation of strength and durability for concrete exposed to such aggressive environment, the samples were rested in a solution of Na2SO4 (150 g/lt) in accordance with ASTM C 1012 for the tests. As a result of this experimental study, it is noted that the use of 20% fly ash, replacement material instead of cement, has no significant effect on compressive strength of concrete over time. Abdulhalim Karaşin and Murat Doğruyol Copyright © 2014 Abdulhalim Karaşin and Murat Doğruyol. All rights reserved.