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Journal of Materials    Follow    
  This is an Open Access Journal Open Access journal
     ISSN (Print) 2314-4866 - ISSN (Online) 2314-4874
     Published by Hindawi Publishing Corporation Homepage  [347 journals]
  • RTV Silicone Membranes as Agents to Confine the Liquid Components in Dye
           Sensitized Solar Cells
    • Abstract: 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.
      PubDate: Wed, 13 Nov 2013 13:05:15 +000
  • Inverse Slip Accompanying Twinning and Detwinning during Cyclic Loading of
           Magnesium Single Crystal
    • Abstract: 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.
      PubDate: Tue, 17 Sep 2013 08:54:54 +000
  • Glass Formation in Ni-Zr-(Al) Alloy Systems
    • Abstract: 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.
      PubDate: Sun, 08 Sep 2013 15:39:52 +000
  • Recent Developments in the X-Ray Reflectivity Analysis for Rough Surfaces
           and Interfaces of Multilayered Thin Film Materials
    • Abstract: 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.
      PubDate: Wed, 31 Jul 2013 11:32:04 +000
  • A.C. Conductivity Investigations on Layered Ceramics
    • Abstract: 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.
      PubDate: Mon, 15 Jul 2013 10:35:55 +000
  • Sago Starch-Mixed Low-Density Polyethylene Biodegradable Polymer:
           Synthesis and Characterization
    • Abstract: 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.
      PubDate: Wed, 10 Jul 2013 09:56:18 +000
  • PLD Grown Polycrystalline Tungsten Disulphide (WS2) Films
    • Abstract: 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.
      PubDate: Tue, 09 Jul 2013 15:36:09 +000
  • Nanostructured TiO2 Doped with Nb as a Novel Support for PEMFC
    • Abstract: 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.
      PubDate: Thu, 30 May 2013 17:48:04 +000
  • Enhanced Performance of Membraneless Sodium Percarbonate Fuel Cells
    • Abstract: 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.
      PubDate: Wed, 22 May 2013 09:03:58 +000
  • Microwave Assisted Synthesis of ZnO Nanoparticles: Effect of Precursor
           Reagents, Temperature, Irradiation Time, and Additives on Nano-ZnO
           Morphology Development
    • Abstract: 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.
      PubDate: Tue, 14 May 2013 13:13:13 +000
  • Direct Current Magnetron Glow Discharge Plasma Characteristics Study for
           Controlled Deposition of Titanium Nitride Thin Film
    • Abstract: 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.
      PubDate: Thu, 09 May 2013 11:40:35 +000
  • Effect of Deposition Time on the Morphological Features and Corrosion
           Resistance of Electroless Ni-High P Coatings on Aluminium
    • Abstract: 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.
      PubDate: Wed, 08 May 2013 15:01:44 +000
  • Dielectric Properties of PbNb2O6 up to 700°C from Impedance
    • Abstract: 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.
      PubDate: Wed, 08 May 2013 09:17:17 +000
  • Effects of ThermoMechanical Coupling in Tribological Surface
           Transformations: A One-Dimensional Modelling Including Irreversible
           Solid-Solid Phase Transformations and Classical Plasticity
    • Abstract: 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.
      PubDate: Sun, 28 Apr 2013 10:41:21 +000
  • Synthesis of Hydroxyapatite Nanoparticles in Presence of a Linear
    • Abstract: 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.
      PubDate: Tue, 23 Apr 2013 15:23:44 +000
  • Absorption and Radiation Transitions in Configuration of Mn-Doped ZnS
           Nanoparticles Synthesized by a Hydrothermal Method
    • Abstract: The Mn-doped ZnS nanoparticles with Mn content of 0–15 mol% were synthesized by a hydrothermal method from the solutions Zn(CH3COO)2 0.1 M, Mn(CH3COO)2 0.01 M, and Na2S2O3 0.1 M at 220°C for 15 h. These nanoparticles presented the cubic structure with average particle size about 16 nm. The yellow-orange photoluminescence (PL) band at 586 nm was attributed to the radiation transition of the electrons in 3d5 unfilled shell of Mn2+ ions [4T1(4G)-6A1(6S)] in ZnS matrix. The photoluminescence excitation (PLE) spectra monitored at the yellow-orange band, the absorption spectra also showed the near band edge absorption of 336–349 nm and the characteristic absorption bands of Mn2+(3d5) ions at 392, 430, 463, 468, 492, and 530 nm. These bands should be attributed to the absorption transitions of 3d5 electrons from the ground state 6A1(6S) to the excited states 4E(4D), 4T2(4D), 4A1(4G)-4E(4G), 4T2(4G), and 4T1(4G) of Mn2+ ions. The intensity of PL band and absorption bands of Mn2+(3d5) ions also increased with the Mn content from 0.1 to 9 mol%, but their peak positions were almost unchanged. The PLE spectra showed clearly the energy level splitting of Mn2+ ions in ZnS crystal field and allowed for the calculation of the splitting width between the excited states 4A1(4G), 4E(4G) about of 229 cm−1 (28.6 meV), and the Racah parameters  cm−1,  cm−1, and the crystal field strength  cm−1. The PL spectra with different excitation wavelengths corresponding to absorption transition bands of the PLE spectra allow for the discussion of the indirect and direct excitation mechanisms of Mn2+(3d5) ions in the ZnS crystal.
      PubDate: Sun, 21 Apr 2013 15:59:39 +000
  • Synthesis, Characterization, and Thermal Decomposition of Pure and
           Dysprosium Doped Yttrium Phosphate System
    • Abstract: Yttrium phosphate and dysprosium doped yttrium phosphate were synthesized from aqueous solutions using rare earth chloride, phosphoric acid, and traces of ammonium hydroxide. The synthesized material was then characterized for their structural investigations using powder X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) supplemented with energy dispersive X-ray analysis (EDAX). The spectroscopic investigations were carried out using Fourier transform infrared (FTIR) spectroscopy. The thermal stability was studied using differential thermogravimetric analysis (DTA), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) techniques. X-ray diffraction analysis reveals that both yttrium phosphate and dysprosium doped yttrium phosphate belong to tetragonal system with lattice parameter  Å,  Å and  Å,  Å, respectively. The stoichiometry of the grown composition was established by energy dispersive X-ray analysis. The EDAX analysis suggests the presence of water molecules. The presence of water molecules along with orthophosphate group and metallic ion group was confirmed by FTIR analysis. Thermogravimetric analysis suggests that decomposition in case of yttrium phosphate takes place in three different stages and the final product stabilizes after 706°C, whereas in case of dysprosium doped yttrium phosphate the decomposition occurs in two different stages, and the final product stabilizes after 519°C.
      PubDate: Thu, 18 Apr 2013 11:16:56 +000
  • Photocatalytic Performance of TiO2 Nanofibers as a Function of Fiber
           Diameter Using TiCl2 as a Precursor
    • Abstract: We focus on the production of TiO2 nanofibers with controllable diameters using a facile electrospinning technique at room temperature. The resulting nanofibers were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible spectroscopy (UV-Vis). The most important electrospinning parameters including potential difference (kV), flow rate (mL/h), and the separation distance between electrodes (cm) were found to have significant influence on the diameter of the produced nanofibers. The photocatalytic performance of TiO2 nanofibers was successfully demonstrated for decolorization of Rhodamine B (Rh.B) under UV light irradiation. It was found that fiber diameter has a crucial influence on the photocatalytic performance of TiO2 nanofibers.
      PubDate: Wed, 17 Apr 2013 14:12:12 +000
  • Porosity Analysis of Plasma Sprayed Coating by Application of Soft
    • Abstract: The present piece of work describes the industrial wastes and low grade ores (fly ash + quartz + ilmenite, as the coating material), deposited on mild steel substrates. In many cases it is found that porosity is an important factor on the coating surface. Knowledge about the extent of these porosity imperfections is critical since they influence a wide range of spray coated properties and behaviors. To decrease the porosity by optimizing necessary operating parameters, artificial neural network (ANN) technique is used. The aim of this investigation is to find out appropriate input vectors in ANN model. ANN experimental results indicate that the projection network has good generalization capability to optimize the porosity.
      PubDate: Mon, 15 Apr 2013 10:42:02 +000
  • Nanoscale Phenomena Occurring during Pyrolysis of Salix viminalis Wood
    • Abstract: Selective utilisation of unique properties of Salix viminalis wood enables preparation of materials of nanotechnologic properties. Thermal decomposition of lignin-cellulose organic matter results in the formation of a nanostructured porous carbon matrix (charcoal). Narrowed pore size distribution (PSD) in the subnanometer range allows to consider the charcoals as carbon molecular sieves (CMSs), which are capable of separating even chemically inert gases like neon, krypton, and nitrogen. High tolerance of Salix viminalis to heavy metal ions enables enriching living plant tissues with metal ions like lanthanum and manganese. Such ions may later form LaMnO3 with parallel transformation of plant tissues (organic matter) to carbon matrix using a heat treatment. In this way, one gets a hybrid material: a porous carbon matrix with uniformly suspended nanocrystallites of LaMoO3. The crystallites are in the catalytically active phase during the conversion of n-butanol to heptanone-4 with high yield and selectivity.
      PubDate: Wed, 10 Apr 2013 11:46:45 +000
  • Flocculation Efficiency of Poly(Acrylamide-Co-Acrylic Acid) Obtained by
           Electron Beam Irradiation
    • Abstract: A correlation between physicochemical characteristics of flocculants obtained by electron beam irradiation and their efficiency for wastewater treatment is presented. For real wastewater treatment, our interest was focused upon total suspended solids, fatty matter, and chemical oxygen demand. Flocculation studies were carried out using a standard jar test. A treatment option based on poly(acrylamide-co-acrylic acid) for wastewater taken from a slaughterhouse plant is presented.
      PubDate: Wed, 10 Apr 2013 10:35:31 +000
  • Nanocomposites of Polyaniline and Cellulose Nanocrystals Prepared in
           Lyotropic Chiral Nematic Liquid Crystals
    • Abstract: Stable lyotropic chiral nematic liquid crystals (N*-LCs) of cellulose nanocrystals (CNs) were prepared via hydrolysis using sulfuric acid. The lyotropic N*-LCs were used as an asymmetric reaction field to synthesize polyaniline (PANI) onto CNs by in situ polymerization. As a primary step, we examined the mesophase transition of the N*-LCs of CNs suspension before and after in situ polymerization of aniline (ANI) by polarizing optical microscopy. The structure of nanocomposites of PANI/CNs was investigated at a microscopic level using Fourier transform infrared spectroscopy and X-ray diffraction. Influence of the CNs-to-ANI ratio on the morphology of the nanocomposites was also investigated at macroscopic level by scanning electron and transmission electron microscopies. It is found that the weight ratio of CNs to aniline in the suspension significantly influenced the size of the PANI particles and interaction between CNs and PANI. Moreover, electrical properties of the obtained PANI/CNs films were studied using standard four-probe technique. It is expected that the lyotropic N*-LCs of CNs might be available for an asymmetric reaction field to produce novel composites of conjugated materials.
      PubDate: Tue, 09 Apr 2013 12:02:48 +000
  • Parameter Optimization in the Synthesis of BZT Ceramics to Achieve Good
           Dielectric Properties
    • Abstract: The powder synthesis of barium zirconate titanate (BZT) (BaZrTiO3) from the mechanochemical activation of BaCO3, ZrO2, and TiO2 was studied. The grinding effect, by using a planetary ball milling, on the crystallization temperature of BZT powders was analyzed. X-ray diffractometry, differential thermal analysis, thermogravimetric analysis, and scanning electronic microscopy (SEM) were used as characterization methods. The crystallization behavior of powders activated by high-energy grinding and the effect of grinding time on the BZT crystallization were analyzed. After grinding by 4 h, the BaZr(0.05)Ti(0.95)O3 sample was almost fully crystallized at . The results of dielectric and ferroelectric properties show that high-energy ball milling is a practical and promising way to prepare BZT ceramics.
      PubDate: Tue, 09 Apr 2013 12:00:45 +000
  • Influence of the Texture and Strain on the Behaviour of Ni53.6Mn27.1Ga19.3
           and Ni54.2Mn29.4Ga16.4 Shape Memory Alloys
    • Abstract: Polycrystalline samples of Ni53.6Mn27.1Ga19.3 and Ni54.2Mn29.4Ga16.4 shape memory alloys were investigated using dilatometry. The longitudinal axes of the samples were perpendicular to the columnar grains. Both alloys showed positive shape memory effects. The martensitic phase transformation occurred without hysteresis in both alloys with transformation temperatures of 174°C for the Ni53.6Mn27.1Ga19.3 alloy and 253°C for the Ni54.2Mn29.4Ga16.4 alloy. The dilatation characteristics for both alloys were determined in three perpendicular directions. The strain associated with the internal stress at the interface between the two martensitic structures and the two grains affected the dilatation characteristics in the y and z directions (perpendicular to the longitudinal axis of the sample). The microstructure was determined for all the directions investigated. To investigate the mechanical history, a round cross-section of the Ni54.2Mn29.4Ga16.4 sample was machined using a milling machine along the longitudinal axis so that both sides of the sample were symmetrical. This sample treatment changed the dilatation characteristics of the martensite and austenite. The study and analysis of the dilatation characteristics of the thermal cycle showed the relaxation of internal stresses and the reorientation of the martensitic variants.
      PubDate: Mon, 08 Apr 2013 09:19:04 +000
  • Studies on Electric and Dielectric Properties of Porous
    • Abstract: Frequency-dependent electric and dielectric properties of the porous Sm0.5Sr0.5CoO3−δ cathode prepared through conventional combustion synthesis technique were studied in the temperature range 298 K–973 K. The crystal symmetry, space group, and unit cell dimensions were confirmed by analyzing XRD pattern. XRD analysis indicates the formation of a single-phase orthorhombic structure with space group Pnma 62. Scanning electron microscopy technique was used to examine the morphology of the sample. Scanning electron microscopy study showed the formation of porous structure with an average grain size about 850 nm. From the electrical study, it is observed that the conduction in Sm0.5Sr0.5CoO3−δ sample takes place through the hopping mechanism and follows the inverse universal power law. The correlated barrier hopping model was employed successfully to explain the mechanism of charge transport in Sm0.5Sr0.5CoO3−δ. Further, the ac conductivity data was used to evaluate the minimum hopping length and apparent activation energy. The minimum hopping length was found to be ~10−4 times smaller than the grain size of Sm0.5Sr0.5CoO3−δ. The peaking behaviour of the real part of dielectric constant with frequency was explained using the Rezlescu model. This study helps to confirm that the charge transportation in Sm0.5Sr0.5CoO3−δ is due to two types of charge carriers.
      PubDate: Mon, 08 Apr 2013 09:01:26 +000
  • On the Prediction of Strength from Hardness for Copper Alloys
    • Abstract: Hardness and strength values of over 55 copper alloys strengthened by solid solution strengthening, precipitation hardening, cold working, and dispersion strengthening were compiled. The yield strength (YS) and ultimate tensile strength (UTS) values of the copper alloys examined ranged between 50 to 1300 MPa and 200 to 1400 MPa, respectively. The compiled values were classified based on strain-hardening potential an indirect method to understand the effect of strain-hardening characteristics. Least squares regression analysis was employed to establish correlations between strength and Vickers hardness values. Strain-hardening potential showed a significant effect on the correlations. In all the cases, a linear relation was obtained for both YS and UTS with hardness for the entire range of values under analysis. Simple empirical equations were proposed to estimate the strength using bulk hardness. The proposed correlations obtained for the entire range of values were verified with experimental values. A good agreement was observed between experimental and predicted values.
      PubDate: Mon, 08 Apr 2013 08:07:41 +000
  • PVA/Polysaccharides Blended Films: Mechanical Properties
    • Abstract: Blends of polyvinyl alcohol (PVA) and angico gum (AG) and/or cashew gum (CG) were used to produce films by casting method. Morphological and mechanical properties of these films were studied and compared to the properties of a commercial collagen membrane of bovine origin (MBO). The films presented thickness varying from 70 to 140 μm (PVA/AG) and 140 to 200 μm (PVA/CG). Macroscopic analysis showed that a PVA/CG film was very similar to MBO regarding the color and transparency. The higher values of tensile strength (TS) and elastic modulus (EM) were observed in the film. On the other hand, PVA/CG and PVA/CG-AG presented the highest value of percentage of elongation (E%). Pearson’s Correlation Analysis revealed a positive correlation between TS and EM and a negative correlation between E% and EM. The PVA/CG film presented mechanical properties very similar to MBO, with the advantage of a higher E% (11.96) than MBO (2.94). The properties of the PVA blended films depended on the polysaccharide added in the blend, as well as the acid used as a catalyst. However, all produced films presented interesting mechanical characteristics which enables several biotechnological applications.
      PubDate: Thu, 04 Apr 2013 16:04:58 +000
  • Growth and Characterization of ULMA Single Crystals Doped with Ammonium
    • Abstract: Single crystals of pure and ammonium chloride-doped urea L-malic acid (ULMA) were grown by slow evaporation technique. Many interesting results on several properties of ammonium chloride impurity added to ULMA single crystals have been observed and studied. The different morphology of ammonium chloride-doped ULMA crystals was noticed and the effect of ammonium chloride doping on the growth, optical, and hardness properties has been investigated. The presence of functional groups has been estimated by FTIR analysis. The lattice parameters of the grown crystals were studied by single crystal X-ray diffraction technique. Powder X-ray diffraction studies confirm the diffraction planes of the grown crystals. The UV-visible spectrum shows the cutoff wavelength at 220 nm. A study on the thermal properties has also been carried out. The NLO property of the grown crystals was confirmed by SHG studies.
      PubDate: Sun, 31 Mar 2013 14:32:24 +000
  • ITO/Poly(Aniline)/Sol-Gel Glass: An Optically Transparent, pH-Responsive
           Substrate for Supported Lipid Bilayers
    • Abstract: Described here is fabrication of a pH-sensitive, optically transparent transducer composed of a planar indium-tin oxide (ITO) electrode overcoated with a poly(aniline) (PANI) thin film and a porous sol-gel layer. Adsorption of the PANI film renders the ITO electrode sensitive to pH, whereas the sol-gel spin-coated layer makes the upper surface compatible with fusion of phospholipid vesicles to form a planar supported lipid bilayer (PSLB). The response to changes in the pH of the buffer contacting the sol-gel/PANI/ITO electrode is pseudo-Nernstian with a slope of 52 mV/pH over a pH range of 4–9. Vesicle fusion forms a laterally continuous PSLB on the upper sol-gel surface that is fluid with a lateral lipid diffusion coefficient of 2.2 μm2/s measured by fluorescence recovery after photobleaching. Due to its lateral continuity and lack of defects, the PSLB blocks the pH response of the underlying electrode to changes in the pH of the overlying buffer. This architecture is simpler to fabricate than previously reported ITO electrodes derivatized for PSLB formation and should be useful for optical monitoring of proton transport across supported membranes derivatized with ionophores and ion channels.
      PubDate: Sat, 30 Mar 2013 14:36:03 +000
  • Studies on Structural, Spectral, and Optical Properties of Organic
           Nonlinear Optical Single Crystal: 2-Amino-4,6-dimethylpyrimidinium
    • Abstract: 2-Amino-4,6-dimethylpyrimidinium p-hydroxybenzoate (ADPHB), a novel organic material, was synthesized, and crystals were grown by slow evaporation solution growth method. The cell parameters and crystalline perfection of the grown crystal were studied by single crystal and powder X-ray diffraction analyses. The presence of various functional groups of the grown crystal was confirmed using Fourier Transform infrared spectral analysis. UV-Visible spectrum shows that ADPHB crystals have high transmittance in the range 305–900 nm. The refractive index and transient photoluminescence properties of the grown crystal were analyzed. The laser induced surface damage threshold, optical birefringence, and second harmonic generation efficiency of the grown crystal were studied.
      PubDate: Thu, 28 Mar 2013 14:16:44 +000
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