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Malayer, Iran

Souri D.,University of Malayer
European Physical Journal B

xSb 2O 3-40TeO 2-(60 - x) V 2O 5 glasses with 0 ≤ x ≤ 10 (in mol%) have been prepared by rapid- melt quenching method. DSC curves of these ternary glasses have been investigated. The glass transition properties that have been measured and reported in this paper, include the glass transition temperature (T g ), glass transition width (ΔT g ), heat capacity change at glass transition (ΔC P) and fragility (F). Thermal stability, Poisson's ratio, fragility and glass forming tendency of these glasses have been estimated, to determine relationship between chemical composition and the thermal stability or to interpret the structure of glass. In addition, Makishima and Makenzie's theory was applied for determination of Young's modulus, bulk modulus and shear modulus, indicating a strong relation between elastic properties and structure of glass. Generally, results of this work show that glass with x = 0 has the highest shear, bulk and Young's moduli which make it as suitable candidate for the manufacture of strong glass fibers in technological applications; but it should be mentioned that glass with x = 8 has higher handling temperature and super resistance against thermal attack. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg. Source

Rezaei-Sameti M.,University of Malayer
Physica E: Low-Dimensional Systems and Nanostructures

In this work the density functional theory (DFT) calculations are used to investigate the electrical properties of three SiC atoms doped on the representative (4, 4) armchair and (8, 0) zigzag aluminum phosphide nanotubes (AlPNTs). The mouths of nanotubes are capped by hydrogen atoms in order to saturate the dangling bonds of the boundaries and to simulate a longer tube and to decrease calculation time. The structures of all nanotubes were allowed to relax and the chemical shielding (CS) parameters were calculated for the atoms of optimized structures. The results indicated that the band gap energies and NMR parameters detect the effects of doping. The CS parameters also indicated that in both models of (4, 4) armchair and (8, 0) zigzag among all the P and Al atoms, which are directly connected to the Si and C atoms, have the smallest isotropic and anisotropic chemical shielding. © 2011 Elsevier B.V. Source

Rezaei-Sameti M.,University of Malayer
Physica B: Condensed Matter

The electrical properties and NMR parameters of the pristine and Ga-doped structures of two representative (8, 0) zigzag and (4, 4) armchair of boron phosphide nanotubes (BPNTs) have been investigated. The structural geometries of above nanotubes have been allowed to relax by optimization and then the isotropic and anisotropic chemical shielding parameters (CSI and CSA) of 11B and 31P have been calculated based on DFT theory. The results reveal that the influence of Ga-doping was more significant on the geometries of the zigzag model than the armchair one. The difference of band gap energies between the pristine and Ga-doped armchair BPNTs was larger than the zigzag model. Significant differences of NMR parameters of those nuclei directly contributed to the Ga-doping atoms have been observed. © 2012 Elsevier B.V. All rights reserved. Source

In this work, an armchair model of the (4,4) boron phosphide nanotubes (BPNTs) with a 1-nm length and consisting of 32 B and 32 P atoms is considered to study the influence of doping three atoms of aluminum in sites of boron (B 3AlPNTs) and three atoms of nitrogen in sites of phosphors (BP 3NNTs) on the electrostatic structure properties. The mouths of nanotubes are capped by hydrogen atoms in order to saturate the dangling bonds of the boundaries and to decrease the calculation time. The structures of BPNTs, B 3AlPNTs and BP 3NNTs are optimized by performing the level of density functional theory (DFT) using 6-31G basis set. The optimized structures are used for calculating the chemical shielding (CS) tensors and nuclear magnetic resonance parameters such as isotropic chemical shielding (CS I) and anisotropic chemical shielding (CS A). The results reveal that in both models of B 3AlPNTs and BP 3NNTs by doping N atoms the chemical shielding parameters of P and B atoms, which are directly connected to the Al and N atoms decreased and the other sites significantly changed. © 2011 Elsevier B.V. All rights reserved. Source

Souri D.,University of Malayer
Measurement: Journal of the International Measurement Confederation

Glasses with composition (60 - x)V2O5-40TeO 2 - x MoO3 with 20 ≤ x ≤ 60 (in mol%) have been prepared using the usual melt quenching method. The optical absorption spectra of the glasses have been recorded in the wavelength range 300-800 nm. The position of the absorption edge and therefore the optical band gap values were found to be depend on the glass composition. For these glasses, the optical band gap was found to be in the range 2.03-2.86 eV with increasing of MoO 3 concentration. The absorption spectrum fitting method was employed to obtain the energy gap. In this method, only the measurement of the absorbance spectrum of the glass is needed. For each sample, the width of the band tail was determined. Also, the density and glass transition temperature values indicate that the rigidity and packing of the samples increase with increase in MoO3 concentration as a network former. © 2010 Elsevier Ltd. All rights reserved. Source

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