Showing 7 results for Amiri
M. Chalkosh Amiri,
Volume 14, Issue 1 (1-1994)
Abstract
S. Amiri and S. H. Amirshahi,
Volume 26, Issue 2 (1-2008)
Abstract
The reflectance factors of transparent fibers, free delustering agent, are predicted by geometric as well as Kubelka-Munk models.
Transparent fibers are simulated by a net of glass capillary tubes containing different solutions of dyestuffs. Based on the results, prediction of the reflectance factor of capillary net by geometric model is relatively better than those obtained from Kubelka-Munk model. However, the geometric model suffers from a complex and massive computation process. Generally speaking, the geometric model performs better for dark transparent samples due to the ignorable internal scattering phenomena. On the other hand, the Kubelka-Munk model provides better results for light samples, where the geometric model fails in acceptable prediction.
H. Amiri, S. M. Mirkazemi, A. Beitollahi ,
Volume 34, Issue 2 (Journal of Advanced Materials- Summer 2015)
Abstract
In this investigation, the effect of heat treatment on magnetic properties of glass and nano-structured cobalt-ferrite glass-ceramic was studied. The glass was synthesized in the system of Na2O-Fe2O3-CoO-B2O3-SiO2. Based on DTA results, heat treatment was done at different times and temperatures. X-ray diffraction pattern of glass-ceramic showed the crystallization of CoFe2O4 and some nonmagnetic phases. The highest magnetization of 11.8 emu/g was obtained for the sample heat-treated for 2 hr at 670C in graphite bed. Average crystallite size of CoFe2O4 in this sample was 50 nm. Scanning Electron Microscopy (SEM) confirmed the formation of cobalt ferrite nanoparticles in the glass matrix.
A. Amiri Moghaddam, M. Kalantar,
Volume 36, Issue 1 (Journal of Advanced Materials-Spring 2017)
Abstract
The aim of this investigation is obtaining WC-Co composite powder from WO3 and Co3O4 by in-situ and carbothermic reduction method using activated carbon as a reducing agent. In this study, cobalt and tungsten oxide powders with 17% carbon (30% more than stoichiometric value) were mixed by ball-milling under atmosphere of argon for 20 hours. Differential Thermal Analysis (DTA) and Thermal Gravimetric Analysis (TGA) results on powder mixture show complete reducing of oxides at 1050°C and forming cobalt carbide and tungsten carbide. Compact samples underwent carbothermic reduction at 1050 °C for different times of 1, 2 and 4 hours with protective layer of alumina and carbon powder mixture with ratio of 1:1. Based on X-Ray Diffraction (XRD) analyses, the best holding time in furnace is 4 hours, in which tungsten reduction and carbonization is completed. XRD evaluation of reduced compacted samples in three conditions of atmosphere protective layer of alumina and carbon powder mixture with ratio of 1:1, protective foil of refractory steel and argon, shows that unreduced oxides and extra phases are present in argon atmosphere and protective foil of steel but not in alumina and carbon mixture layer. The measurement results of physical and mechanical properties on the sintered composite sample in heating rate of 5 °C /min to temperature 1500 °C and the holding time of 2 hours under a shielding layer of alumina and carbon shows obtaining the optimal properties (Pr=80%, KIC=8.1 MPa , MHV=15.67GPa) comparable to that of advanced and costly methods.
H. Salehi, P. Amiri, Y. Loveimi Motlagh,
Volume 37, Issue 1 (Journal of Advanced Materials-Spring 2018)
Abstract
In this article, the electronic and optical properties of bulk TiC and its narrow nanowires were investigated using Quantum-Espresso/PWSCF computational package in the framework of density functional theory. According to the results, this compound showed a metallic behavior in the bulk structure, but the small diameters of the nanowires against the bulk structure showed a semiconducting behavior. This deviation became negligible at the higher diameters. In both structures, the electronic results were compatible with the optical calculations of the structure under consideration. Considering the optical results, the structure of bulk TiC had the maximum amount of refractive index value and this amount could be decreased by a reduction in the nanowire diameters. Also, the optical results indicated that by increasing the size of nanowires, the ELLOS value was raised toward the corresponding bulk value
G. R. Faghani, A. R. Khajeh-Amiri,
Volume 38, Issue 4 (Journal of Advanced Materials-Winter 2020)
Abstract
Due to special properties such as low density, high strength and high corrosion resistance Ti-6Al-4V alloy has been used extensively in various industries, especially in the aerospace aspects. However the major problem of this alloy is its poor tribological properties under relatively high loads. In the present study, in order to improve the tribological properties of mentioned alloy, chromium particles were added to Ti-6Al-4V layers in the nitrogen-containing atmosphere during the Tungsten Inert Gas (TIG) welding process. Microstructural investigations using optical microscopy, X-ray diffraction analysis and scanning electron microscopy, proved the formation of TiN, TiCr2 and Cr2N particles in the matrix of hard titanium phase. The hardness of TIG alloyed layer increased to 1000 HV0.3 which was 4 times higher than that of the base alloy. Moreover, the wear rate of TIG alloyed samples with chromium and nitrogen under 30N load and distance of 1000 m was 5.9 times lower than that of the bare Ti-6Al-4V alloy.
H. Salehi, N. Zhulayi Bakhoda, P. Amiri,
Volume 38, Issue 4 (Journal of Advanced Materials-Winter 2020)
Abstract
In this research, the optical properties of tungsten disulfide including dielectric function, the static refractive index, the imaginary part of the dielectric function, optical band gap, energy loss spectrum and its magnetic properties have been studied. Calculations have been done by using Quantum Espresso package which is based on density functional theory and pseudo-potential technique. The static refractive indices of this compound at diffrent x and z directions were calculated 3.66 and 2.55, respectively. The amount of optical band gap, obtained from the imaginary part of dielectric function, was estimated to be 1.45 eV. In addition, bulk plasmon energy, obtained from energy loss spectrum at x and z directions, were obtained to be 17.95 eV and 17.25 eV, respectively.
