ISRN Materials Science The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. The Excellent Mechanical Properties of Cork: A Novel Approach through the Analysis of Contact Stress Wed, 07 May 2014 07:01:28 +0000 In many technological applications of cork, this biomaterial is under strongly localized contact stresses, which largely differ from the homogeneous distribution of stresses of the typical uniaxial compression tests. Indentation tests constitute an excellent form of determining the behavior of the materials under localized stresses. In the present study, the applicability of Hertzian and Brinell indentation tests to the evaluation of the mechanical properties of cork is tested. One of the main conclusions of the study is that the elastic anisotropy of the material is related to the anisotropic structure of the different sections cut from a cork sample, a clear difference between the back tangential section and the other sections being observed. Antonio Díaz-Parralejo, Eduardo M. Cuerda-Correa, Antonio Macías-García, José Sánchez-González, and M. Ángeles Díaz-Díez Copyright © 2014 Antonio Díaz-Parralejo et al. All rights reserved. Microstructure and Mechanical Properties of Vacuum Hot Pressed P/M Short Steel Fiber Reinforced Aluminum Matrix Composites Sun, 04 May 2014 14:05:04 +0000 Commercial purity aluminum powder of irregular shape and ligamental morphology having average particle size of 75 µm was blended with medium carbon steel short fibers having average diameter of 100 µm and maximum length up to 1000 µm. The green compacts of pure aluminum and reinforced compositions were hot-pressed in 10−3 torr vacuum, at 723 K, 773 K, and 823 K for 5, 10, and 15 min durations under 50 MPa axial stress on Gleeble 3800 simulator. Microstructures of the sintered composites have been studied by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The sintered compacts were characterized for densification behavior, hardness, and growth of FexAly reaction interface. Positive densification parameter was achieved for up to 10 wt.% reinforcement fraction. The maximum hardness of 51 Hv was achieved for 10 wt.% at 823 K for 15 min sintering time. The reaction interface was analysed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The reaction interface was found to be composed of Fe3Al, FeAl2, Fe2Al, Fe3Al, Fe4Al, Fe2Al5, and FeAl intermetallics. Growth of the reaction interface was diffusion-controlled which followed a nearly parabolic law with a rate constant of 1.41 × 10−12 m2 s−1 at 823 K. S. Jain, K. Chandra, and V. Agarwala Copyright © 2014 S. Jain et al. All rights reserved. Seismic Behaviour of Exterior Reinforced Concrete Beam-Column Joints in High Performance Concrete Using Metakaolin and Partial Replacement with Quarry Dust Mon, 07 Apr 2014 14:40:23 +0000 Recent earthquakes have demonstrated that most of the reinforced concrete structures were severely damaged; the beam-column joints, being the lateral and vertical load resisting members in reinforced concrete structures, are particularly vulnerable to failures during earthquakes. The existing reinforced concrete beam-column joints are not designed as per code IS13920:1993. Investigation of high performance concrete (HPC) joints with conventional concrete (CC) joints (exterior beam-column) was performed by comparing various reinforcement detailing schemes. Ten specimens were considered in this investigation and the results were compared: four specimens with CC (with and without seismic detailing), four specimens with HPC (with and without seismic detailing), and two specimens with HPC at confinement joint. The test was conducted for lateral load displacement, hysteresis loop, load ratio, percent of initial stiffness versus displacement curve, total energy dissipation, strain in beam main bars, and crack pattern. The results reveal that HPC with seismic detailing will be better compared with other reinforcements details under cyclic loading and reverse cyclic loading. G. R. Vijay Shankar and D. Suji Copyright © 2014 G. R. Vijay shankar and D. Suji. All rights reserved. Flexural Fatigue-Life Assessment and Strength Prediction of Glass Fibre Reinforced Polymer Concrete Composites Thu, 27 Mar 2014 11:51:09 +0000 The paper presents the results of an investigation conducted to assess the fatigue-life and prediction of flexural fatigue strength of polymer concrete composites based on epoxy resin as binder material. Three point flexural fatigue tests were conducted on polymer concrete specimens using MTS servo controlled actuator, to obtain the fatigue lives of the composites at different stress levels. One hundred and thirty-seven specimens of size  mm were tested in flexural fatigue. Forty-three static flexural tests were also conducted to facilitate fatigue testing. It has been observed that the probabilistic distribution of fatigue-life of polymer concrete composite (PCC) and glass fibre reinforced polymer concrete composite (GFRPCC), at a particular stress level, approximately follows the two-parameter Weibull distribution, with statistical corelation coefficient values exceeding 0.90. The fatigue strength prediction model, representing S-N relationship, has been examined and the material coefficients have been obtained for GFRPCC containing 0.5% and 1.0% glass fibres. Design fatigue lives for GFRPCC containing different contents of glass fibres have been estimated for acceptable probabilities of failure and compared with those of PCC. Raman Bedi, S. P. Singh, and Rakesh Chandra Copyright © 2014 Raman Bedi et al. All rights reserved. Stress and Grain Boundary Properties of GaN Films Prepared by Pulsed Laser Deposition Technique Mon, 17 Mar 2014 09:47:16 +0000 Polycrystalline gallium nitride films were successfully deposited on fused silica substrates by ablating a GaN target using pulsed Nd-YAG laser. Microstructural studies indicated an increase in the average crystallite size from ~8 nm to ~70 nm with the increase in substrate temperature from 300 K to 873 K during deposition. The films deposited here were nearly stoichiometric. XPS studies indicated two strong peaks located at ~1116.6 eV and ~395 eV for Ga2p3/2 and a N1s core-level peak, respectively. The films deposited at substrate temperature above 573 K are predominantly zinc blende in nature. PL spectra of the films deposited at higher temperatures were dominated by a strong peak at ~3.2 eV. FTIR spectra indicated a strong and broad absorption peak centered ~520 cm−1 with two shoulders at ~570 cm−1 and 584 cm−1. Characteristic Raman peak at ~531 cm−1 for the A1(TO) mode is observed for all the films. Grain boundary trap states varied between and  m−2, while barrier height at the grain boundaries varied between 12.4 meV and 37.14 meV. Stress in the films decreased with the increase in substrate temperature. D. Ghosh, S. Hussain, B. Ghosh, R. Bhar, and A. K. Pal Copyright © 2014 D. Ghosh et al. All rights reserved. Study of Structural and Phase Transition of Nickel Metal Sun, 09 Mar 2014 06:23:47 +0000 Annealing study of nickel metal in the temperature range 300–1000 K has been carried out using molecular dynamics (MD) simulations. The simulation is done for models containing 104 particles Ni at both crystalline and amorphous states. We obtain the change as a function of annealing time for the potential energy of system, pair radial distribution function (PRDF), and distribution of coordination number (DCN). The calculation shows that the aging slightly reduces the potential energy of system. This result evidences that the amorphous model undergoes different quasiequilibrated states during annealing. The crystalline model undergoes the slow relaxation which reduces the energy of system and eliminates structural defects in crystal lattices. Pham Huu Kien Copyright © 2014 Pham Huu Kien. All rights reserved. Excitation Density Dependence of Optical Oxygen Sensing in Poly(9,9-dioctylfluorene) Waveguides Showing Amplified Spontaneous Emission Tue, 04 Mar 2014 14:12:03 +0000 Reversible oxygen induced emission quenching of both the Spontaneous Emission (SE) and the Amplified Spontaneous Emission (ASE) of poly(9,9-dioctylfluorene) waveguides is demonstrated. We show that ASE shows a stronger quenching than SE, up to about 6.2 times, but also a stronger decrease when the excitation density increases. We conclude that the fast increase of the ASE decay rate is the main process in determining the ASE detection sensitivity, limiting the potentiality of sensitivity improvement of ASE with respect to SE. M. Anni and S. Lattante Copyright © 2014 M. Anni and S. Lattante. All rights reserved. A Study on the Influence of Hot Press Forming Process Parameters on Flexural Property of Glass/PP Based Thermoplastic Composites Using Box-Behnken Experimental Design Tue, 04 Mar 2014 07:19:59 +0000 A thermoplastic composite is produced from polypropylene matrix with glass fibre reinforcement. These types of composite materials are ecofriendly nature due to their reusability after their lifetime. These polymer composites are alternative to heavy metals that are currently being used in many non-structural applications. In spite of being ecofriendly nature, the range of applications is limited due to poor mechanical properties as compared with thermoset matrix composite. Hence an attempt was made in this work to improve the mechanical property such as flexural property of Glass/PP hybrid woven composites by optimizing the parameters during compression moulding, such as mould pressure, mould temperature, and holding time using Box-Behnken experimental design. Each process variables were taken in 3 different levels. Second order polynomial model with quadratic effect was chosen. The optimum combination of process parameters was obtained by using contour diagram. The levels of importance of process parameters on flexural properties were determined by using analysis of variance (ANOVA). The variation of flexural property with cited process parameters was mathematically modelled using the regression analysis. B. Senthil Kumar and Subramanian Balachandar Copyright © 2014 B. Senthil Kumar and Subramanian Balachandar. All rights reserved. Gas Bubbles Expansion and Physical Dependences in Aluminum Electrolysis Cell: From Micro- to Macroscales Using Lattice Boltzmann Method Sun, 23 Feb 2014 16:35:19 +0000 This paper illustrates the results obtained from two-dimensional numerical simulations of multiple gas bubbles growing under buoyancy and electromagnetic forces in a quiescent incompressible fluid. A lattice Boltzmann method for two-phase immiscible fluids with large density difference is proposed. The difficulty in the treatment of large density difference is resolved by using nine-velocity particles. The method can be applied to simulate fluid with the density ratio up to 1000. To show the efficiency of the method, we apply the method to the simulation of bubbles formation, growth, coalescence, and flows. The effects of the density ratio and the initial bubbles configuration on the flow field induced by growing bubbles and on the evolution of bubbles shape during their coalescence are investigated. The interdependencies between gas bubbles and gas rate dissolved in fluid are also simulated. Mouhamadou Diop, Frédérick Gagnon, Li Min, and Mario Fafard Copyright © 2014 Mouhamadou Diop et al. All rights reserved. Fracture Surface Analysis in Thixojoined Tool Steels Sun, 23 Feb 2014 12:48:53 +0000 Thixojoining has been developed for D2 and M2 tool steels. The suitable globular microstructure and excellent bonding quality are obtained through this work. Scanning electron microscopy (SEM) observation along the joint interfaces showed a smooth transition zone with no cracks. In addition, fracture surface of the shear test samples showed that the fracture mode was transgranular. Finally, based on obtained results, this method presented high quality joint with nonequilibrium diffusion interface. A. Kalaki, M. Ketabchi, and Sh. Zangeneh Copyright © 2014 A. Kalaki et al. All rights reserved. Synthesis of High Surface Area Mesoporous Silica Powder Using Anionic Surfactant Wed, 05 Feb 2014 06:34:52 +0000 Over the past several years, synthesized mesoporous nanosilica (SiO2) powders have been developed by many different methods. The methods include precipitation and microemulsion, the Stöber method, chemistry, and technology. In this study, mesoporous silica powders are synthesized by the sol-gel method. The sol-gel method obtains a high purity silica powder; however, the process yields a low percentage. Past syntheses of SiO2 powder precursors are expensive, but this study needs to find a replacement precursor for low cost alternatives. A high surface area was used to form an anion surfactant sodium dodecyl sulfate, which regulates the molar concentration. The particles size variability was changed by the precursor molar ratio of the sodium silicate solution with hydrochloric acid. Sang-wook Ui, In-seok Choi, and Sung-churl Choi Copyright © 2014 Sang-wook Ui et al. All rights reserved. Optical and Magnetic Studies on Cu2O/PANI Nanocomposite Prepared by Chemical Polymerization Method Tue, 21 Jan 2014 00:00:00 +0000 Polyaniline embedded green copper oxide (Cu2O/PANI) nanocomposite has been synthesized through in situ chemical polymerization method in acidic medium at room temperature. The structural, optical, and magnetic properties of Cu2O/PANI nanocomposite were investigated through Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectra (UV-Vis spectra), scanning electron microscopy (SEM), photoluminescence spectra (PL), and vibrating sample magnetometer (VSM). FTIR spectra confirmed the formation of Cu2O/PANI composite through the shifting of vibrational peaks of PANI and green Cu2O nanoparticles at 825, 1142, 1299, 1499, 1573 cm−1 and 695 cm−1 respectively. SEM analysis revealed that many aggregations of well-separated irregular shape of Cu2O nanoparticles with diameter about 15–40 nm exist in the composite matrix. Optical absorbance studies further confirmed the formation of composite through the blue shift of absorption peaks of PANI and diminishing intensity peak of Cu2O. Cu2O/PANI nanocomposite demonstrates semiconducting as well as diamagnetic behavior like PANI and Cu2O nanoparticles. The nanocomposite exhibits high relative photoluminescence intensity in blue as well as green-yellow region of visible spectrum. The optical band gap value from absorption coefficient data is found to be 3.23 eV. K. Gopalakrishnan, C. Ramesh, M. Elango, and M. Thamilselvan Copyright © 2014 K. Gopalakrishnan et al. All rights reserved. Inhibition of Corrosion of Aluminium in Potassium Hydroxide Solution by Pyridine Derivatives Sun, 19 Jan 2014 00:00:00 +0000 The influence of 3-methylpyridine and 3-nitropyridine on the corrosion rate of aluminium in 1 mol L−1 potassium hydroxide solution was investigated using weight loss method. It was observed that both investigated derivatives behave as inhibitors. It was found that the inhibition efficiency increases with increasing inhibitor concentration. The inhibition mechanism is discussed on the basis of adsorption of inhibitor molecules on the metal surface. The inhibitors were adsorbed on the surface according to the Frumkin adsorption isotherm. The effect of temperature on the corrosion inhibition of Al was studied and thermodynamic functions for the dissolution and adsorption processes in the absence and in the presence of the inhibitors were computed and discussed. D. B. Patil and A. R. Sharma Copyright © 2014 D. B. Patil and A. R. Sharma. All rights reserved. Synthesis and Mesomorphic Properties of New Fluorinated Schiff Base Liquid Crystals Thu, 16 Jan 2014 14:03:14 +0000 Two new compounds, 4-alkanoyloxybenzylidene--fluoroaniline and 4-fluorobenzylidene--n-alkanoyloxyaniline comprising a terminal fluorosubstituent were studied. The fluoro substituent contributes to the molecular polarizability, thus affecting intermolecular interactions and hence resulting in smectic mesomorphism. The mesomorphic properties were studied using differential scanning calorimetry and polarizing optical microscopy techniques. The mesomorphic properties of compounds studied are strongly dependent on the orientation of the imine (CH=N) linkage. The former Schiff base exhibited smectic A phase whereas the latter compound did not display any mesophase. Reversed imine linkage has caused depression of mesomorphic property in the compound studied (4-fluorobenzylidene--n-alkanoyloxyaniline). The mesomorphic properties of the present compounds were compared with other structurally related series to establish the chemical structure-mesomorphic property relationship. Sie-Tiong Ha and Teck-Leong Lee Copyright © 2014 Sie-Tiong Ha and Teck-Leong Lee. All rights reserved. Process of Identifying Stress Fields from Strain Fields in the Specimen with a Hole Wed, 30 Oct 2013 17:43:04 +0000 The paper is focused on the process of identifying stress fields from strain fields in the specimen with a hole. The experiment was realized on the specimen with a hole made from anisotropic material. The main attention is paid to the analysis of deformation in the areas of stress (near the hole). That geometry generates a heterogeneous strain field which has been measured during the test using a digital image correlation system. The advantage of using heterogeneous strain fields in the identification procedure is that a complex state of stress-strain can be analyzed at the same time. On the other hand the stress field cannot be directly computed from the test and a suitable identification procedure has to be developed. Here, the virtual fields method (VFM) adapted for plastic strain has been used to identify the hardening behaviour and the anisotropy of the material. The values obtained by the VFM have been compared with the results coming from a standard identification made with uniaxial tensile tests. Michaela Štamborská, Miroslav Kvíčala, and Vratislav Mareš Copyright © 2013 Michaela Štamborská et al. All rights reserved. Role of ZnO in Dc Electrical Conductivity of Lithium Bismuthate Glasses Tue, 29 Oct 2013 15:31:45 +0000 Glasses of various compositions belonging to the Bi2O3-B2O3-ZnO-Li2O quaternary system were prepared using melt quench technique. Dc electric measurements were done on the samples, and activation energies are determined. Arrhenius plots showed straight line behaviour. It is observed that the conductivity of the samples increased with temperature and also with Li2O content, whereas the activation energy decreased with Li2O content. The isothermal plots for constant ZnO and constant Bi2O3 glasses revealed that the conduction in these glasses is due to lithium ions only. The isothermal plots for constant lithium containing glasses varied nonlinearly with two maxima, which is attributed to mixed former effect. The variation is explained based on Anderson-Stuart model. Shashidhar Bale and Syed Rahman Copyright © 2013 Shashidhar Bale and Syed Rahman. All rights reserved. Magnetotransport Behaviour of Nanocrystalline () Sun, 27 Oct 2013 15:52:31 +0000 The nanocrystalline samples of (PSMO) (, 0.50, 0.55, and 0.60) were synthesized by wet-chemical sol-gel route. Structural, magnetic, and magnetotransport properties have been studied systematically. It is found that samples with Sr content and 0.50 show paramagnetic to ferromagnetic (PM-FM) transition at  K with no trace of FM-AFM transition within the temperature range of 77–350 K. However, interestingly a second transition is observed at 273 and 255 K, respectively, for samples and 0.60 correspond to an A-AFM magnetic structure. This indicates that samples and 0.50 are ferromagnetic below , while other samples ( and 0.60) have a mixed phase consisting of FM and A-type AFM phases. Resistivity versus temperature (ρ-T) curve shows that the resistivity of all the samples is much larger than the single crystals of corresponding compositions due to large contribution of grain boundaries in the present nanocrystalline samples. Moreover, the decrease in metallic component at higher Sr concentration is also evidenced by the successive reduction in magnetoresistance (MR) with increasing Sr content from to 0.60. Neelam Maikhuri, Anurag Gaur, Vasudha Aggarwal, Umesh Gaur, and H. K. Singh Copyright © 2013 Neelam Maikhuri et al. All rights reserved. Microstructural and Compositional Characterisation of Chromate Pretreatment on Aluminium Thu, 24 Oct 2013 14:15:41 +0000 Chromate conversion coating developed on aluminium has been examined using SEM/EDX and CTEM/EDX with a view to having further knowledge of its intrinsic surface, plan, and sectional morphologies which will aid the understanding of their roles in improved corrosion and adhesion properties of the underlying substrate. The surface consists of spherical clusters of particulate materials. The sections, however, reveal approximately parallel, linear features which terminate at or close to the metal/coating interface, while plan views show cell-like particulate features. The coating is composed of chromium and aluminium compounds, both, probably hydrated. For a conversion coating to fully replace its chromate counterpart, most of these features may have to be replicated in the nonchromium coating material which should contain nontoxic, leachable corrosion inhibiting species. M. Oki Copyright © 2013 M. Oki. All rights reserved. Structural and Optical Properties of Aluminum Nitride Thin Films Deposited by Pulsed DC Magnetron Sputtering Thu, 03 Oct 2013 18:20:00 +0000 Aluminum nitride thin films were deposited on Si (100) substrate by pulsed DC (asymmetric bipolar) reactive magnetron sputtering under variable nitrogen flow in a gas mixture of argon and nitrogen. The deposited film was characterized by grazing incidence X-ray diffraction (GIXRD), atomic force microscope (AFM), spectroscopic ellipsometry, and secondary ion mass spectroscopy (SIMS). GIXRD results have shown (100) reflection of wurtzite AlN, whereas AFM micrographs have revealed very fine grained microstructure with average roughness in the range 6–8 nm. Spectroscopic ellipsometry measurements have indicated the band gap and refractive index of the film in the range 5.0–5.48 eV and 1.58–1.84, respectively. SIMS measurement has indicated the presence of oxygen in the film. R. K. Choudhary, P. Mishra, A. Biswas, and A. C. Bidaye Copyright © 2013 R. K. Choudhary et al. All rights reserved. Predictability of Inverse Impact Force Location as Affected by Measurement Noise Thu, 03 Oct 2013 18:15:39 +0000 The impact force localization inverse problem is considered through a nonlinear optimization procedure. The objective function is derived in the particular case of elastic structures for which Maxwell-Betti theorem holds. Additional geometric constraints were introduced in order to stabilize optimum search. The solution of the constrained non linear mathematical problem was performed by means of two outstanding evolutionary algorithms that include Genetic Algorithm and Particle Swarm Optimization. Focus was done on the robustness aspect of force impact localization predictability when an additive white noise is assumed to perturbed strain measurement. It was found that the Genetic Algorithm fails to track the exact solution independently from the noise level as an error was systematically present in the solution. On the other hand, the Particle Swarm Optimisation based algorithm performed very well even for noise levels as high as 2% of the measured strain signal. Abdelali El-Bakari, Abdellatif Khamlichi, Rachid Dkiouak, Ali Limam, and Eric Jacquelin Copyright © 2013 Abdelali El-Bakari et al. All rights reserved. Influence of Oxygen on Zinc Oxide Films Fabricated by Ion-Beam Sputter Deposition Thu, 03 Oct 2013 17:20:54 +0000 In this study, zinc oxide films were deposited by an ion-beam sputter deposition in various oxygen partial pressures at room temperature. The films changed the structures from amorphous to polycrystalline with increasing the oxygen partial pressure (). The optimal was found at Torr because the film prepared at the oxygen partial pressure had the lowest resistivity and the highest transparence in the visible light region. The lowest resistivity results from a great number of oxygen vacancy sites formed on the polycrystalline surface as exposed to the atmosphere. Moreover, the film has the highest XRD peak intensity, smallest FWHM diffraction peak, smallest -spacing, and smallest biaxial stress. Jin-Cherng Hsu and Yueh-Sheng Chiang Copyright © 2013 Jin-Cherng Hsu and Yueh-Sheng Chiang. All rights reserved. The Design of UV Absorbing Systems for Horticultural Applications Tue, 24 Sep 2013 09:38:18 +0000 The synthesis and fluorescence behavior of a series of bis(trisilylalkyl)anthracene molecules is described. The photodegradation of these molecules under UV light has been monitored and compared to a commercially available fluorescent optical brightener. There is a relationship between the structure and the rate of photo decay. The materials with more bulky substituents exhibit the greater stability towards UV. For bis(triphenylsilyl)anthracene the photostability appears to be comparable with a commercially available optical brightener, but the molecule may be susceptible to thermal decay. V. Mahendra, F. J. Davis, P. Hadley, and A. Gilbert Copyright © 2013 V. Mahendra et al. All rights reserved. Effect of Deformation and Aging on Properties of Al-4.1%Cu-1.4%Mg Aluminum Alloy Wed, 11 Sep 2013 10:47:58 +0000 Deformation scheme and preheat treatment of Al-4.1%Cu-1.4%Mg aluminum alloy are chosen, homogenizing annealing at 430°C for 1.5 h, cooling to 250°C in furnace at a cooling rate of less than 30°C/h and then cooling to room temperature to make Al-4.1%Cu-1.4%Mg aluminum alloy annealed fully. Heat treatment tests of Al-4.1%Cu-1.4%Mg aluminum alloy mainly consisting of rolling and aging were conducted, and the optimum peak of aging mechanism is 190°C/12 h. Through comparison of microstructure and mechanical properties with different deformation rates and aging mechanisms, effect of deformation rates and aging mechanism on properties of Al-4.1%Cu-1.4%Mg aluminum alloy was analyzed, and the optimum double peak of aging mechanism is 135°C/7 h + 185°C/14 h. Orthogonal experiments were carried out to analyze mechanical and electrical properties of tested materials before and after deformation, and the effect of aging mechanism on Al-4.1%Cu-1.4%Mg Al alloy was analyzed, and the optimum regression of aging mechanism is 190°C/12 h + 240°C/40 min + 190°C/12 h. Aging scheme is closely related to corrosion resistance of Al-4.1%Cu-1.4%Mg aluminum alloy, and three different aging schemes can improve the corrosion resistance. The exfoliation corrosion evaluation results show that the aging effect on exfoliation corrosion ability order is RRA two-step aging peak aging. Hao Wang, Changsheng Li, Jing Li, Xinglong Wei, and Ruibin Mei Copyright © 2013 Hao Wang et al. All rights reserved. On the Failure and Fracture of Polymer Foam Containing Discontinuities Tue, 10 Sep 2013 16:33:37 +0000 An experimental study is performed to investigate the tensile failure and fracture behavior of polymer foam containing discontinuities. PVC corecell foam, series A800 and A1200 is used for the investigation. Unnotched dog-bone specimen and specimens with center hole and edge cracks are tested under uniaxial tensile loading. Series of experiments are conducted at different defect size to width ratios, and the effect of the defect size on the net-section tensile strength of the foam is investigated. A fracture study is also conducted, and the effect of density and loading rate on the fracture behavior of foam is investigated. A minimal notch-strengthening effect is observed in specimens with center hole, and a notch-weakening effect is observed in specimen with edge notches. Furthermore, the fracture toughness increases with the increase in the foam density and decreases with the increase in loading rate. Addis Kidane Copyright © 2013 Addis Kidane. All rights reserved. A Model for the Stability of a TiO2 Dispersion Mon, 26 Aug 2013 15:46:59 +0000 A computational study of a colloidal dispersion stabilized with grafted polymer layers is presented here as a model for white, water-based paints. The interaction model includes repulsive, three-body interactions and attractive van der Waals forces. The electrostatic interactions are also studied. Stability criteria can be established for the dispersion, such as the thickness of the adsorbed polymer layers, and the quality of the solvent. Using implicit solvent molecular dynamics calculations, the spatial distribution of the pigments is obtained through the calculation of the radial distribution functions. The results show that the solvent quality and the thickness of the grafted polymer layer are key variables in the stability of the dispersion. Additionally, a structural phase transition is predicted, which is driven by the pigment concentration in the dispersion. It is argued that the predictions of this work are useful guidelines in the design of paints and coatings of current industrial interest. Armando Gama Goicochea Copyright © 2013 Armando Gama Goicochea. All rights reserved. Fabrication of Hybrid Surface Composite through Friction Stir Processing and Its Impression Creep Behaviour Sun, 25 Aug 2013 09:03:00 +0000 Al-Ni in situ surface composites were fabricated by friction stir processing method. Friction stir processing produced a composite with nickel and NiAl3 as reinforcement particles in aluminium matrix. The particles were fine and were in the submicrometer size range. The separation distance between the particles was very small. Impression creep experiments were conducted on the samples both at friction stir zone and base material zone at various temperatures. Steady state creep rates were estimated, and activation energy for creep was calculated. It is observed that the friction stir zone offered a higher creep resistance compared to the base metal zone. Higher creep resistance is attributed to the dissolution of nickel atoms into aluminium matrix and the presence of fine nickel particles and NiAl3 precipitates. The measured activation energy indicated that the associated creep mechanism is the dislocation creep in the temperature range of 30–150°C, both in friction stir zone and base metal zone. At higher temperatures (150–180°C) the diffusion creep mechanism is suggested. S. Prakrathi, M. Ravikumar, K. R. Udupa, and K. Udaya Bhat Copyright © 2013 S. Prakrathi et al. All rights reserved. Polymer Composites Based on Plasticized PVC and Vulcanized Nitrile Rubber Waste Powder for Irrigation Pipes Mon, 19 Aug 2013 11:15:57 +0000 The paper presents the technique of production and characterization of polymer composites based on plasticized PVC and rubber powder from vulcanized nitrile rubber waste. The new polymer composites have lower hardness, higher elongation at break, a better tensile strength, and better ozone resistance, and the blend suitable for irrigations pipes for agricultural use was selected. The selected polymer composites have a good behavior under accelerated aging, repeated flexion at room temperature and at low temperature (−20°C), a very good behavior for immersion in water, concentrated acid and basis, animal fat, soya, and sun flower oil, proving their suitability for gaskets, hoses, protection equipment, rubber footwear, and so forth. The resulted thermoplastic polymer composites can be processed by injection, extrusion, and compression molding. Maria Daniela Stelescu Copyright © 2013 Maria Daniela Stelescu. All rights reserved. A Review of Neutron Scattering Applications to Nuclear Materials Wed, 07 Aug 2013 07:45:37 +0000 The growing demand for electric energy will require expansion of the amount of nuclear power production in many countries of the world. Research and development in this field will continue to grow to further increase safety and efficiency of nuclear power generation. Neutrons are a unique probe for a wide range of problems related to these efforts, ranging from crystal chemistry of nuclear fuels to engineering diffraction on cladding or structural materials used in nuclear reactors. Increased flux at modern neutron sources combined with advanced sample environments allows nowadays, for example, studies of reaction kinetics at operating temperatures in a nuclear reactor. Neutrons provide unique data to benchmark simulations and modeling of crystal structure evolution and thermomechanical treatment. Advances in neutron detection recently opened up new avenues of materials characterization using neutron imaging with unparalleled opportunities especially for nuclear materials, where heavy elements (e.g., uranium) need to be imaged together with light elements (e.g., hydrogen, oxygen). This paper summarizes applications of neutron scattering techniques for nuclear materials. Directions for future research, extending the trends observed over the past decade, are discussed. Sven C. Vogel Copyright © 2013 Sven C. Vogel. All rights reserved. Optimum Rotation Speed for the Friction Stir Welding of Pure Copper Tue, 06 Aug 2013 11:12:52 +0000 The friction stir welding (FSW) was conducted in the pure copper plates with the thickness of 4 mm in the constant traverse speed of 25 mm/min and five different rotation speeds. Analysis of metallographic images showed that the increasing of the rotation speed results in the increase of grain size in the nugget zone. Vickers hardness tests were conducted on the weld samples and the maximum hardness obtained in rotation speed of 900 rpm. Results of the tensile tests and their comparison with that of the base metal showed that the maximum strength and the minimum elongation are achieved again in this rotation speed. Yield strength and ultimate tensile strength increased with the decrease in grain size in the nugget region, and the yield strength obeyed Hall-Petch relationship. Hence, the hardness values do not follow the relationship. Masoud Jabbari and Cem C. Tutum Copyright © 2013 Masoud Jabbari and Cem C. Tutum. All rights reserved. Development of a New Piezoelectric Actuator with Slits Thu, 25 Jul 2013 11:10:14 +0000 A piezoelectric actuator was developed for fluid pumps in health monitoring systems. We devised a piezoelectric actuator with some slits, which allows the stretching and contracting deformation in in-plane direction and creates large deflection in out-of-plane direction. The static behaviors under uniform electric field have been analyzed by finite element method. And then, the optimum geometry of slits was searched by response surface methodology for unimorph and bimorph actuators to output the largest deflection under various fixed conditions. The computational results indicated that a bimorph actuator with cross-shaped slit under outside-fixed condition has superior performance for fluid pumps. The proposed slit-inserted actuators have been manufactured as an experiment. As a result, it was verified that the developed actuator can amplify the deflection compared with conventional nonslit actuators. Yasutomo Uetsuji, Hiroyuki Kuramae, Kazuyoshi Tsuchiya, and Hidetoshi Sakamoto Copyright © 2013 Yasutomo Uetsuji et al. All rights reserved.