Journal of Materials The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Thermal Transport between Graphene Sheets and SiC Substrate by Molecular-Dynamical Calculation Wed, 23 Apr 2014 13:49:45 +0000 Using nonequilibrium molecular dynamics, we investigate the mechanisms of thermal transport across SiC/graphene sheets. In simulations, 3C-, 4H-, and 6H-SiC are considered separately. Interfacial thermal resistances between Bernal stacking graphene sheets and SiC (Si- or C-terminated) are calculated at the ranges of 100 K~700 K. The results indicate, whether Si-terminated or C-terminated interface, the interfacial thermal resistances of 4H- and 6H-SiC have similar trends over temperatures. Si-terminated interfacial thermal resistances of 3C-SiC are higher than those of 4H- and 6H-SiC in a wide temperature range from 100 K to 600 K. But, for C-rich interface, this range is reduced from 350 K to 500 K. Zan Wang, Kedong Bi, Huawei Guan, and Jiong Wang Copyright © 2014 Zan Wang et al. All rights reserved. Preparation, and Structural and Magnetic Properties of Ca Substituted Magnesium Ferrite with Composition MgCaxFe2−xO4 ( = 0.00, 0.01, 0.03, 0.05, 0.07) Tue, 22 Apr 2014 00:00:00 +0000 Calcium substituted magnesium ferrite with composition MgCaxFe2−xO4 (where = 0.00, 0.01, 0.03, 0.05, 0.07) was prepared by ceramic technique. These compositions were then subjected to detailed study for structural and magnetic properties. X-ray diffraction studies reveal the formation of single phase cubic spinel. The values of lattice constant increase with the increase in calcium concentration from = 0.00 to = 0.03 and then decrease. Scanning electron microscopic (SEM) technique was used to study the morphology of the grown materials. The grain size was calculated using average intercept line method. The elemental composition of pure and calcium substituted magnesium ferrite was obtained from energy dispersive X-ray analysis (EDAX) spectrum. The hysteresis loop confirms the magnetic behaviour of the prepared composition, which is then discussed on the basis of cation distribution. The parameters such as saturation magnetization, coericivity, and retentivity are calculated. The Curie temperature was found to decrease with increasing calcium content. K. K. Bamzai, Gurbinder Kour, Balwinder Kaur, and S. D. Kulkarni Copyright © 2014 K. K. Bamzai et al. All rights reserved. Synthesis and Characterization of LPCVD Polysilicon and Silicon Nitride Thin Films for MEMS Applications Mon, 14 Apr 2014 00:00:00 +0000 Inherent residual stresses during material deposition can have profound effects on the functionality and reliability of fabricated MEMS devices. Residual stress often causes device failure due to curling, buckling, or fracture. Typically, the material properties of thin films used in surface micromachining are not very well controlled during deposition. The residual stress, for example, tends to vary significantly for different deposition conditions; experiments were carried out to study the polysilicon and silicon nitride deposited by Low Pressure Chemical Vapor Deposition (LPCVD) method at wide range of process conditions. High temperature annealing effects on stress in case polysilicon are also reported. The reduced residual stress levels can significantly improve device performance, reliability, and yield as MEMS devices become smaller. N. Sharma, M. Hooda, and S. K. Sharma Copyright © 2014 N. Sharma et al. All rights reserved. A Reconciliation of Packed Column Permeability Data: Column Permeability as a Function of Particle Porosity Tue, 01 Apr 2014 08:00:31 +0000 In his textbook teaching of packed bed permeability, Georges Guiochon uses mobile phase velocity as the fluid velocity term in his elaboration of the Darcy permeability equation. Although this velocity frame makes a lot of sense from a thermodynamic point of view, it is valid only with respect to permeability at a single theoretical boundary condition. In his more recent writings, however, Guiochon has departed from his long-standing mode of discussing permeability in terms of the Darcy equation and has embraced the well-known Kozeny-Blake equation. In this paper, his teaching pertaining to the constant in the Kozeny-Blake equation is examined and, as a result, a new correlation coefficient is identified and defined herein based on the velocity frame used in his teaching. This coefficient correlates pressure drop and fluid velocity as a function of particle porosity. We show that in their experimental protocols, Guiochon et al. have not adhered to a strict material balance of permeability which creates a mismatch of particle porosity and leads to erroneous conclusions regarding the value of the permeability coefficient in the Kozeny-Blake equation. By correcting the experimental data to properly reflect particle porosity we reconcile the experimental results of Guiochon and Giddings, resulting in a permeability reference chart which is presented here for the first time. This reference chart demonstrates that Guiochon’s experimental data, when properly normalized for particle porosity and other related discrepancies, corroborates the value of 267 for the constant in the Kozeny-Blake equation which was derived by Giddings in 1965. Hubert M. Quinn Copyright © 2014 Hubert M. Quinn. All rights reserved. The Construction of the Dupin Cyclides in a Smectic A Polygonal Texture Sun, 30 Mar 2014 11:31:26 +0000 We report experimental observations with optical microscopy of the usual so-called polygonal texture. We have made simulations of the Dupin cyclides in one small region of the sample. Claire Meyer, Brice Jonckheere, and Coline Penaud Copyright © 2014 Claire Meyer et al. All rights reserved. Effect of Sn Addition on Thermal and Optical Properties of    Glass Thu, 27 Mar 2014 16:27:33 +0000 Study of thermal and optical parameters of    glass has been undertaken. Crystallization and glass transition kinetics has been investigated under nonisothermal conditions by DSC technique. Phase separation has been observed in the material and is investigated by taking the XRD of annealed bulk samples. The material possesses good glass forming ability, high value of glass transition temperature about 420 K, and glass stability. Optical band gap and other optical constants such as refractive index and extinction coefficient have been determined. The isoelectronic substitution of Ge with Sn in the glassy system reduces the optical band gap and enhances the thermal properties. Vivek Modgil and V. S. Rangra Copyright © 2014 Vivek Modgil and V. S. Rangra. All rights reserved. Synthesis and Characterization of Aluminum Doped Zinc Oxide Nanostructures via Hydrothermal Route Tue, 25 Mar 2014 00:00:00 +0000 Stable crystalline aluminum doped zinc oxide (AZO) nanopowders were synthesized using hydrothermal treatment processing. Three different aluminum precursors have been used. The Al-precursors were found to affect the morphology of the obtained nanopowders. AZO nanoparticles based on zinc acetate and aluminum nitrate have been prepared with different Al/Zn molar ratios. XRD investigations revealed that all the obtained powders have single phase zincite structure with purity of about 99%. The effect of aluminum doping ratio in AZO nanoparticles (based on Al-nitrate precursor) on structure, phase composition, and particle size has been investigated. The incorporation of Al in ZnO was confirmed by UV-Vis spectroscopy revealing a blue shift due to Burstein-Moss effect. A. Alkahlout, N. Al Dahoudi, I. Grobelsek, M. Jilavi, and P. W. de Oliveira Copyright © 2014 A. Alkahlout et al. All rights reserved. Structural Lightweight Concrete Production by Using Oil Palm Shell Thu, 20 Mar 2014 11:29:54 +0000 Conventional building materials are widely used in a developing country like Malaysia. This type of material is costly. Oil palm shell (OPS) is a type of farming solid waste in the tropical region. This paper aims to investigate strength characteristics and cost analysis of concrete produced using the gradation of OPS 0–50% on conventional coarse aggregate with the mix proportions 1 : 1.65 : 2.45, 1 : 2.5 : 3.3, and 1 : 3.3 : 4.2 by the weight of ordinary Portland cement, river sand, crushed stone, and OPS as a substitution for coarse aggregate. The corresponding w/c ratios were used: 0.45, 0.6, and 0.75, respectively, for the defined mix proportions. Test results indicate that compressive strength of concrete decreased as the percentage of the OPS increased in each mix ratio. Other properties of OPS concrete, namely, modulus of rupture, modulus of elasticity, splitting tensile strength, and density, were also determined and compared to the corresponding properties of conventional concrete. Economic analysis also indicates possible cost reduction of up to 15% due to the use of OPS as coarse aggregate. Finally, it is concluded that the use of OPS has great potential in the production of structural lightweight concrete. Habibur Rahman Sobuz, Noor Md. Sadiqul Hasan, Nafisa Tamanna, and Md. Saiful Islam Copyright © 2014 Habibur Rahman Sobuz et al. All rights reserved. Acid Corrosion Inhibition and Adsorption Behaviour of Ethyl Hydroxyethyl Cellulose on Mild Steel Corrosion Thu, 13 Mar 2014 15:11:57 +0000 The corrosion inhibition of mild steel in 1.0 M H2SO4 solution by ethyl hydroxyethyl cellulose has been studied in relation to the concentration of the additive using weight loss measurement, EIS, polarization, and quantum chemical calculation techniques. The results indicate that EHEC inhibited corrosion reaction in the acid medium and inhibition efficiency increased with EHEC concentration. Further increase in inhibition efficiency is observed in the presence of iodide ions, due to synergistic effect. Impedance results reveal that EHEC is adsorbed on the corroding metal surface. Adsorption followed a modified Langmuir isotherm, with very high negative values of the free energy of adsorption . The polarization data indicate that the inhibitor was of mixed type, with predominant effect on the cathodic partial reaction. The frontier molecular orbitals, HOMO (the highest occupied molecular orbital) and LUMO (the lowest unoccupied molecular orbital) as well as local reactivity of the EHEC molecule, were analyzed theoretically using the density functional theory to explain the adsorption characteristics at a molecular level. The theoretical predictions showed good agreement with experimental results. I. O. Arukalam, I. O. Madu, N. T. Ijomah, C. M. Ewulonu, and G. N. Onyeagoro Copyright © 2014 I. O. Arukalam et al. All rights reserved. Synthesis and Characterization of Optically Active Fractal Seed Mediated Silver Nickel Bimetallic Nanoparticles Tue, 11 Mar 2014 13:41:35 +0000 The synthesis of new seed mediated AgNi allied bimetallic nanocomposites was successfully carried out by the successive reduction of the metal ions in diethylene glycol, ethylene glycol, glycerol, and pentaerythritol solutions, with concomitant precipitation of Ag/Ni bimetal sols. The optical measurement revealed the existence of distinct band edge with surface plasmon resonance (SPR) in the region of 400–425 nm and excitonic emission with maximum peak at 382 nm which were reminiscent of cluster-in-cluster surface enriched bimetallic silver-nickel sols. The morphological characterization by transmission electron microscopy, high resolution transmission electron microscopy, and X-ray diffraction analyses complimented by surface scan using X-ray photoelectron spectroscopy strongly supported the formation of intimately alloyed face-centered silver/nickel nanoclusters. Joseph Adeyemi Adekoya, Enock Olugbenga Dare, Michael Adediran Mesubi, and Neerish Revaprasadu Copyright © 2014 Joseph Adeyemi Adekoya et al. All rights reserved. Fabrication of Thermoelectric Sensor and Cooling Devices Based on Elaborated Bismuth-Telluride Alloy Thin Films Mon, 10 Mar 2014 09:47:45 +0000 The principal motivation of this work is the development and realization of smart cooling and sensors devices based on the elaborated and characterized semiconducting thermoelectric thin film materials. For the first time, the details design of our sensor and the principal results are published. Fabrication and characterization of Bi/Sb/Te (BST) semiconducting thin films have been successfully investigated. The best values of Seebeck coefficient (α(T)) at room temperature for Bi2Te3, and (Bi1−xSbx)2Te3 with x = 0.77 are found to be −220 µV/K and +240 µV/K, respectively. Fabrication and evaluation of performance devices are reported. 2.60°C of cooling of only one Peltier module device for an optimal current of  mA is obtained. The values of temperature measured by infrared camera, by simulation, and those measured by the integrated and external thermocouple are reported. A sensitivity of the sensors of 5 mV Torr−1 mW−1 for the pressure sensor has been found with a response time of about 600 ms. Abdellah Boulouz, Alain Giani, Brice Sorli, Lahcen Koutti, Abdellah Massaq, and Frederique Pascal-Delannoy Copyright © 2014 Abdellah Boulouz et al. All rights reserved. Investigating the Physical Properties of Sintered Alumina in the Presence of MgO Nanopowder Wed, 05 Mar 2014 12:04:32 +0000 Magnesium oxide nanopowder is synthesized using magnesium nitrate hexahydrate and oxalic acid as precursors via the sol-gel method. In order to investigate the effect of magnesia nanopowders on the physical properties of sintered alumina, 0.1, 0.3, and 0.5 wt% of MgO are added to alumina. The prepared specimens were sintered at 1570°C for 4 hours under an inert atmosphere. The morphology and size of nanopowders were characterized by transmission electron microscope (TEM) and scanning electron microscope (SEM). Structural analysis was investigated by means of Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Outcomes show that by increasing the percentage of MgO, spinel phase (MgAl2O4) has been formed in the structure of alumina. During the sintering process, spinel phase diffused through the grain boundaries and pinned the grain boundaries which led to decrease in grain sizes. So, by decreasing the grain size, the physical properties of sintered alumina have improved. Mehran Dadkhah, Abdollah Saboori, and Majid Jafari Copyright © 2014 Mehran Dadkhah et al. All rights reserved. Preparation and Characterization of K-Carrageenan/Nanosilica Biocomposite Film Mon, 03 Mar 2014 15:55:25 +0000 The purpose of this study is to improve the performance properties of K-carrageenan (K-CRG) by utilizing nanosilica (NSI) as the reinforcing agent. The composite films were prepared by solution casting method. NSI was added up to 1.5% in the K-CRG matrix. The prepared films were characterized for mechanical (tensile strength, tensile modulus, and elongation at break), thermal (differential scanning calorimetry, thermogravimetric analysis), barrier (water vapour transmission rate), morphological (scanning electron microscopy), contact angle, and crystallinity properties. Tensile strength, tensile modulus, and crystallinity were found to have increased by 13.8, 15, and 48% whereas water vapour transmission rate was found to have decreased by 48% for 0.5% NSI loaded K-CRG composite films. NSI was found to have formed aggregates for concentrations above 0.5% as confirmed by scanning electron microscopy. Melting temperature, enthalpy of melting, and degradation temperature of K-CRG increased with increase in concentration of NSI in K-CRG. Contact angle also increased with increase in concentration of NSI in K-CRG, indicating the decrease in hydrophilicity of the films improving its water resistance properties. This knowledge of the composite film could make beneficial contributions to the food and pharmaceutical packaging applications. Lokesh R. Rane, Niranjan R. Savadekar, Pravin G. Kadam, and Shashank T. Mhaske Copyright © 2014 Lokesh R. Rane et al. All rights reserved. Influence of Cooling Rate on Microsegregation Behavior of Magnesium Alloys Mon, 03 Mar 2014 09:06:31 +0000 The effect of cooling rate on microstructure and microsegregation of three commercially important magnesium alloys was investigated using Wedge (V-shaped) castings of AZ91D, AM60B, and AE44 alloys. Thermocouples were distributed to measure the cooling rate at six different locations of the wedge casts. Solute redistribution profiles were drawn based on the chemical composition analysis obtained by EDS/WDS analysis. Microstructural and morphological features such as dendrite arm spacing and secondary phase particle size were analyzed using both optical and scanning electron microscopes. Dendritic arm spacing and secondary phase particle size showed an increasing trend with decreasing cooling rate for the three alloys. Area percentage of secondary phase particles decreased with decreasing cooling rate for AE44 alloy. The trend was different for AZ91D and AM60B alloys, for both alloys, area percentage of β-Mg17Al12 increased with decreasing cooling rate up to location 4 and then decreased slightly. The tendency for microsegregation was more severe at slower cooling rates, possibly due to prolonged back diffusion. At slower cooling rate, the minimum concentration of aluminum at the dendritic core was lower compared to faster cooled locations. The segregation deviation parameter and the partition coefficient were calculated from the experimentally obtained data. Md. Imran Khan, Ahmad O. Mostafa, Mohammad Aljarrah, Elhachmi Essadiqi, and Mamoun Medraj Copyright © 2014 Md. Imran Khan et al. All rights reserved. Structural, Linear, and Nonlinear Optical and Mechanical Properties of New Organic L-Serine Crystal Tue, 11 Feb 2014 13:52:42 +0000 Nonlinear optical single crystal of organic amino acid L-Serine (LS) was grown by slow evaporation technique. Solubility study of the compound was measured and metastable zone width was found. Single crystal X-ray diffraction study was carried out for the grown crystal. The linear and nonlinear optical properties of the crystal were confirmed by UV-Vis analysis and powder SHG tester. FT-IR spectrum was recorded and functional groups were analyzed. Vickers’ microhardness studies showed the mechanical strength of the grown crystal. Laser damage threshold value of the crystal was calculated. Photoconductivity studies reveal the conductivity of the crystal. K. Rajesh and P. Praveen Kumar Copyright © 2014 K. Rajesh and P. Praveen Kumar. All rights reserved. RTV Silicone Membranes as Agents to Confine the Liquid Components in Dye Sensitized Solar Cells Wed, 13 Nov 2013 13:05:15 +0000 Selected silicone membranes are investigated in order to find attractive multifunctional materials as liquid confining flexible agents with good heat resistance as well as low affinity towards the chemical specimens commonly used in dye sensitized solar cells (DSSC). In fact, the leakage and/or volatilization of liquid components inside DSSC remains one of the most critical obstacles in the progress of this technology from laboratory scale to large area applications. Dynamic mechanical spectroscopic, differential scanning calorimetric, and thermogravimetric analyses on dry membranes were performed in order to investigate their mechanical properties and their thermal stability. By a further comparative study between the equilibrium uptake and the adsorption-desorption process of a nitrile based solution, useful indications about the ability of these networks to encapsulate the liquid mixture were inferred. Moreover, a rough evaluation of porosity was also carried out, giving results which are in agreement with surface morphology observed by scanning electron microscopy and atomic force microscopy. In the light of the results obtained by the different experimental techniques the confinement capability of these membranes towards the liquid components inside a DSSC is discussed. Antonino Bartolotta, Giuseppe Calogero, Cristina Crupi, and Gaetano Di Marco Copyright © 2013 Antonino Bartolotta et al. All rights reserved. Inverse Slip Accompanying Twinning and Detwinning during Cyclic Loading of Magnesium Single Crystal Tue, 17 Sep 2013 08:54:54 +0000 In situ, observation of twinning and detwinning in magnesium single crystals during tension-compression cyclic loading was made using optical microscopy. A quantitative analysis of plastic strain indicates that twinning and detwinning experience two stages, low and high work hardening de-twinning, and pure re-twinning and fresh twinning combined with retwinning. Slip is always activated. For the first time, inverse slip accompanying with pure retwinning and high work hardening detwinning was experimentally identified, which provides insights in better understanding of the activity of twining, detwinning, and slips. Qin Yu, Jian Wang, and Yanyao Jiang Copyright © 2013 Qin Yu et al. All rights reserved. Glass Formation in Ni-Zr-(Al) Alloy Systems Sun, 08 Sep 2013 15:39:52 +0000 Structural and thermal properties of binary () alloys obtained by melt spinning and copper mold casting methods were investigated. The fully amorphous samples in a bulk form cannot be obtained in the binary Ni-Zr alloys over a wide composition range, though they have and values close to or even higher than those of the binary Cu-Zr bulk metallic glasses (BMGs). The low thermal stability of the supercooled liquid against crystallization and the formation of the equilibrium crystalline phases with a high growth rate are responsible for their low glass-forming abilities (GFAs). Relatively low thermal conductivities of Ni-based alloys are also considered to be another factor to limit their GFAs. The GFA of the binary Ni65.5Zr34.5 alloy alloyed with 4% or 5% Al was enhanced, and a fully glassy rod with a diameter of 0.5 mm was formed. Lanping Huang and Song Li Copyright © 2013 Lanping Huang and Song Li. All rights reserved. Recent Developments in the X-Ray Reflectivity Analysis for Rough Surfaces and Interfaces of Multilayered Thin Film Materials Wed, 31 Jul 2013 11:32:04 +0000 X-ray reflectometry is a powerful tool for investigations on rough surface and interface structures of multilayered thin film materials. The X-ray reflectivity has been calculated based on the Parratt formalism, accounting for the effect of roughness by the theory of Nevot-Croce conventionally. However, in previous studies, the calculations of the X-ray reflectivity often show a strange effect where interference effects would increase at a rough surface. And estimated surface and interface roughnesses from the X-ray reflectivity measurements did not correspond to the TEM image observation results. The strange result had its origin in a used equation due to a serious mistake in which the Fresnel transmission coefficient in the reflectivity equation is increased at a rough interface because of a lack of consideration of diffuse scattering. In this review, a new accurate formalism that corrects this mistake is presented. The new accurate formalism derives an accurate analysis of the X-ray reflectivity from a multilayer surface of thin film materials, taking into account the effect of roughness-induced diffuse scattering. The calculated reflectivity by this accurate reflectivity equation should enable the structure of buried interfaces to be analyzed more accurately. Yoshikazu Fujii Copyright © 2013 Yoshikazu Fujii. All rights reserved. A.C. Conductivity Investigations on Layered Ceramics Mon, 15 Jul 2013 10:35:55 +0000 Frequency and temperature dependence of a.c. electrical conductivity of layered mixed ionic alkali trititanates, Na1.89Li0.10K0.01Ti3O7, Na1.88Li0.10K0.02Ti3O7, Na1.86Li0.10K0.04Ti3O7, and Na1.85Li0.10K0.05Ti3O7, have been investigated over a wide temperature 350 K 725 K and frequency 10 kHz to 1 MHz range. For this, Arrhenius plots are used for a.c. electrical conductivity of these compounds. The obtained conductivity plots have been divided into four distinct regions and discussed the relevant theory. According to slop variation, the conduction mechanisms occurring are different in different temperature regions. At lower temperatures, the hopping electron disorders the surroundings by moving to its neighboring Ti atoms from their equilibrium positions, causing structural defect in the polycrystalline network named small polaron. At higher temperatures, associated/unassociated interlayer ionic conduction occurs along with the alkali ions hopping through the interlayer space and electron hopping (small polaron) conduction through Ti–Ti chains in these layered polar alkali titanates. Rakesh Singh and Shripal Copyright © 2013 Rakesh Singh and Shripal. All rights reserved. Sago Starch-Mixed Low-Density Polyethylene Biodegradable Polymer: Synthesis and Characterization Wed, 10 Jul 2013 09:56:18 +0000 This research focuses on synthesis and characterization of sago starch-mixed LDPE biodegradable polymer. Firstly, the effect of variation of starch content on mechanical property (elongation at break and Young’s modulus) and biodegradability of the polymer was studied. The LDPE was combined with 10%, 30%, 50%, and 70% of sago for this study. Then how the cross-linking with trimethylolpropane triacrylate (TMPTA) and electron beam (EB) irradiation influence the mechanical and thermal properties of the polymer was investigated. In the 2nd study, to avoid overwhelming of data LDPE polymer was incorporated with only 50% of starch. The starch content had direct influence on mechanical property and biodegradability of the polymer. The elongation at break decreased with increase of starch content, while Young’s modulus and mass loss (i.e., degradation) were found to increase with increase of starch content. Increase of cross-linker (TMPTA) and EB doses also resulted in increased Young’s modulus of the polymer. However, both cross-linking and EB irradiation processes rendered lowering of polymer’s melting temperature. In conclusion, starch content and modification processes play significant roles in controlling mechanical, thermal, and degradation properties of the starch-mixed LDPE synthetic polymer, thus providing the opportunity to modulate the polymer properties for tailored applications. Md Enamul Hoque, Tan Jie Ye, Leng Chuan Yong, and KhairulZaman Mohd Dahlan Copyright © 2013 Md Enamul Hoque et al. All rights reserved. PLD Grown Polycrystalline Tungsten Disulphide (WS2) Films Tue, 09 Jul 2013 15:36:09 +0000 Polycrystalline WS2 films were grown by pulsed laser deposition (PLD) system at relatively low temperature. The main objective of this study is to optimize the growth conditions for polycrystalline WS2 films at relatively low temperature to use them for photovoltaics (PVs). Different growth conditions and substrates are used and examined systematically. It is found out that films grown on strontium titanate SrTiO3 (STO) substrate have the best structural properties when compared to other substrates examined in this work. X-ray diffraction and optical characterizations of these films reveal crystallographic growth and very promising optical properties for PVs. Furthermore, it was observed that higher growth temperature (>300°C) has an unfavorable effect on the layers by creating some tungsten metallic droplets. Salman Alfihed, Mohammad Hossain, Abdulaziz Alharbi, Ahmed Alyamani, and Fahhad H. Alharbi Copyright © 2013 Salman Alfihed et al. All rights reserved. Nanostructured TiO2 Doped with Nb as a Novel Support for PEMFC Thu, 30 May 2013 17:48:04 +0000 Nowadays, one of the major issues of the PEMFC concerns the durability. Historically, carbon has been used as a catalyst support in PEMFC; nevertheless, under the environmental conditions of the cell, the carbon is oxidized, leaving the catalyst unsupported. In order to increase the stability and durability of the catalyst in the PEMFC, a novel nanostructured metallic oxide support is proposed. In this work, TiO2 was doped with Nb to obtain a material that combines chemical stability, high surface area, and an adequate electronic conductivity in order to be a successful catalyst support candidate for long-term PEMFC applications. The TiO2-Nb nanostructured catalyst support was physically and electrochemically characterized. According to the results, the TiO2-Nb offers high surface area and good particle dispersion; also, the electrochemical activity and stability of the support were evaluated under high potential conditions, where the TiO2-Nb proved to be much more stable than carbon. Edgar Valenzuela, Victor Ramos-Sanchez, Alejandro Adolfo Lambert Arista, and Oumarou Savadogo Copyright © 2013 Edgar Valenzuela et al. All rights reserved. Enhanced Performance of Membraneless Sodium Percarbonate Fuel Cells Wed, 22 May 2013 09:03:58 +0000 This paper presents the continuous flow operation of membraneless sodium percarbonate fuel cell (MLSPCFC) using acid/alkaline bipolar electrolyte. In the acid/alkaline bipolar electrolyte, percarbonate works both as an oxidant as well as reductant. Sodium percarbonate affords hydrogen peroxide in aqueous medium. The cell converts the energy released by H2O2 decomposition with H+ and OH− ions into electricity and produces water and oxygen. At room temperature, the laminar flow based microfluidic membraneless fuel cell can reach a maximum power density of 28 mW/cm2 with the molar ratio of [Percarbonate]/[NaOH] = 1 as fuel and [Percarbonate]/[H2SO4] = 2 as oxidant. The paper reports for the first time the use of sodium percarbonate as the oxidant and reductant. The developed fuel cell emits no CO2 and features no proton exchange membrane, inexpensive catalysts, and simple planar structure, which enables high design flexibility and easy integration of the microscale fuel cell into actual microfluidic systems and portable power applications. M. Gowdhamamoorthi, A. Arun, S. Kiruthika, and B. Muthukumaran Copyright © 2013 M. Gowdhamamoorthi et al. All rights reserved. Microwave Assisted Synthesis of ZnO Nanoparticles: Effect of Precursor Reagents, Temperature, Irradiation Time, and Additives on Nano-ZnO Morphology Development Tue, 14 May 2013 13:13:13 +0000 The effect of different variables (precursor reagents, temperature, irradiation time, microwave radiation power, and additives addition) on the final morphology of nano-ZnO obtained through the microwave assisted technique has been investigated. The characterization of the samples has been carried out by field emission scanning electron microscopy (FE-SEM) in transmission mode, infrared (FTIR), UV-Vis spectroscopy, and powder X-ray diffraction (XRD). The results showed that all the above-mentioned variables influenced to some extent the shape and/or size of the synthetized nanoparticles. In particular, the addition of an anionic surfactant (sodium di-2-ethylhexyl-sulfosuccinate (AOT)) to the reaction mixture allowed the synthesis of smaller hexagonal prismatic particles (100 nm), which show a significant increase in UV absorption. Gastón P. Barreto, Graciela Morales, and Ma. Luisa López Quintanilla Copyright © 2013 Gastón P. Barreto et al. All rights reserved. Direct Current Magnetron Glow Discharge Plasma Characteristics Study for Controlled Deposition of Titanium Nitride Thin Film Thu, 09 May 2013 11:40:35 +0000 This paper reports on the study of direct current (DC) magnetron glow discharge plasma characteristics in a cylindrical magnetron system in argon-nitrogen. Presence of nitrogen gas makes the plasma environment reactive, and it results in significant changes of the plasma properties—number density, electron temperature, floating potential, and sheath thickness. Applied magnetic field is a parameter which is closely related to proper deposition of thin film. Cylindrical Langmuir probe and Emissive probe are used as diagnostics for the estimation of various plasma parameters indicated earlier. Controlled titanium nitride (TiN) thin film deposition on bell-metal at different argon-nitrogen gases ratio is another important study reported. Sankar Moni Borah Copyright © 2013 Sankar Moni Borah. All rights reserved. Effect of Deposition Time on the Morphological Features and Corrosion Resistance of Electroless Ni-High P Coatings on Aluminium Wed, 08 May 2013 15:01:44 +0000 High phosphorus Ni-P alloy was deposited on aluminium substrate using electroless deposition route. Using zincating bath, the surface was activated before deposition. Deposition time was varied from 15 minutes to 3 hours. Deposit was characterised using scanning electron microscope with energy dispersive spectroscope, X-ray diffraction, and microhardness tester. The corrosion resistance was measured using Tafel extrapolation route. The medium was aqueous 5% HNO3 solution. The analysis showed that the deposit consisted of nodules of submicron and micron scale. The predominant phase in the deposit was nickel along with phosphides of nickel. Compared to substrate material, deposit showed higher hardness. With increase in deposition time, the deposit showed more nobleness in 5% HNO3 solution and nobleness reached a limiting value in 1 hour deposition time. N. Sridhar and K. Udaya Bhat Copyright © 2013 N. Sridhar and K. Udaya Bhat. All rights reserved. Dielectric Properties of PbNb2O6 up to 700°C from Impedance Spectroscopy Wed, 08 May 2013 09:17:17 +0000 Piezoelectric materials have wide band gap and no inversion symmetry. Only the orthorhombic phase of lead metaniobate (PbNb2O6) can be ferroelectric and piezoelectric below Curie temperature, but not the rhombohedral phase. High temperature piezoelectric applications in current decades have revived international interest in orthorhombic PbNb2O6, synthesis of which in pure form is difficult and not well documented. Second problem is that its impedance spectroscopy (IS) data analysis is still incomplete. Present work attempts to fill up these two gaps. Presently found synthesis parameters yield purely orthorhombic PbNb2O6, as checked by X-ray Rietveld analysis and TEM. Present 20 Hz to 5.5 MHz IS from room temperature to 700°C shows its ferroelectric Curie temperature to be one of the highest reported, >574°C for 0.5 kHz and >580°C for 5.5 MHz. Dielectric characteristics and electrical properties (like capacitance, resistance and relaxation time of the equivalent CR circuit, AC and DC conductivities, and related activation energies), as derived here from a complete analysis of the IS data, are more extensive than what has yet been reported in the literature. All the properties show sharp changes across the Curie temperature. The temperature dependence of activation energies corresponding to AC and DC conductivities has been reexamined. Kriti Ranjan Sahu and Udayan De Copyright © 2013 Kriti Ranjan Sahu and Udayan De. All rights reserved. Effects of ThermoMechanical Coupling in Tribological Surface Transformations: A One-Dimensional Modelling Including Irreversible Solid-Solid Phase Transformations and Classical Plasticity Sun, 28 Apr 2013 10:41:21 +0000 Under compressive loads combined with friction, some materials undergo Tribological Surface Transformations (TSTs) on the surface of the loaded parts and in the immediately vicinity, which in the case of metals, are known as irreversible solid-solid phase transformations. During the solid-solid phase transformations occurring under mechanical loads, TRansformation Induced Plasticity (TRIP) processes are generated at much lower stress levels than those associated with the yield strength of the material in classical plasticity. In order to assess the effects of thermomechanical coupling in these TSTs, a one-dimensional modelling based on irreversible solid-solid phase transformations and classical plasticity is presented and discussed. Grégory Antoni Copyright © 2013 Grégory Antoni. All rights reserved. Synthesis of Hydroxyapatite Nanoparticles in Presence of a Linear Polysaccharide Tue, 23 Apr 2013 15:23:44 +0000 Hydroxyapatite nanoparticles compounds were synthesized. Natural hydroxyapatite and a linear polysaccharide (1–3 linked   β-D galactopyranose and 1,4 linked 3,6 anhydro-α-L-galactopyranose) were used as a precursor in its formation. Our purpose was to produce nanoparticles in the presence of a linear polysaccharide with the use of a gelification method. The powder sample was evaluated by scanning tunneling microscope (STM), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction pattern (XRD), differential thermal analysis (DTA), infrared (IR) analysis, and thermal gravimetric analysis (TGA). According to the results, it was found that these nanoparticles can successfully be synthesized using a polysaccharide in a solution. On the other hand, the XRD peak intensity corresponds to hydroxyapatite structure in the range of temperature of 810°C. The influence of the polysaccharide on the evolution of the nanoparticles has been demonstrated. This observation opens up new routes for the fabrication of nanoparticles using polysaccharides network. The synthesized nanoparticles have diameters ranging from 10 nm to 11 nm approximately. The elaboration conditions such as pH and concentration were optimized in this solution. Humberto A. Monreal Romero, José Mora Ruacho, Carlos A. Martínez Pérez, and Perla E. García Casillas Copyright © 2013 Humberto A. Monreal Romero et al. All rights reserved.