Search for: crystallization
Total 641 records
Crystal structure of 3-(4-chlorophenyl)-2-[(4-nitrophenyl)imino]-1,3- thiazolan-4-one, C15H10ClN3O3S, Article Zeitschrift fur Kristallographie - New Crystal Structures ; Volume 220, Issue 2 , 2005 , Pages 205-206 ; 14337266 (ISSN) ; Hojabri, L ; Sharif University of Technology
C15H10ClN3O3S, orthorhombic, Pbca (no. 61), a = 11.981(2) Å, b = 14.890(4) Å, c = 17.239(4) Å, V = 3075.4 Å3, Z = 8, Rgt(F) = 0.053, wRref(F2) = 0.123, T = 120 K. © by Oldenbourg Wissenschaftsverlag
Article EPL ; Volume 77, Issue 2 , 2007 ; 02955075 (ISSN) ; Ejtehadi, M. R ; Sharif University of Technology
We present an exact treatment of the pairwise surface interactions of biaxial ellipsoidal bodies and derive the exact explicit expressions for the attractive-repulsive Lennard-Jones(6-12) ellipsoid-substrate interactions. The applicability of the results at nanoscale as a coarse-grained description of molecule-substrate interactions has been studied through presenting parameterizations for a number of small biaxial molecules. The study concludes that the anisotropic coarse-grained potential reproduces the atomistic interactions of ellipsoid-like rigid molecules perfectly, with a negligible error of less than 3%. Copyright © EPLA, 2007
Article Aplications of Photonic Technology, Quebec City, 1 June 2002 through 6 June 2002 ; Volume 4833 , 2002 , Pages 535-541 ; 0277786X (ISSN) ; Momeni, B ; Khorasani, S ; Rashidian, B ; Sharif University of Technology
The electromagnetic interface states formed in a heterostructure composed of two semi-infinite Kronig-Penny photonic crystals were studied. Modified transfer matrices were used for the study to show strong similarity between solid-state physics and electromagnetics. The calculations were limited to TE polarization and the numerical examples for both surface and interface states were given
Article Optoelectronics and Advanced Materials, Rapid Communications ; Volume 11, Issue 3-4 , 2017 , Pages 134-138 ; 18426573 (ISSN) ; Dehghanisanij, M ; Rooholamininejad, H ; Bahrampour, A ; Sharif University of Technology
National Institute of Optoelectronics 2017
In this paper quasi photonic crystal fibers (QPCFs) based on 8-fold and Penrose symmetries are analyzed. The confinement loss of both proposed QPCFs with employing perfect matching layer by finite element method has been calculated. It is shown for both presented structures, the confinement loss is negligible relative to Rayleigh scattering loss. The birefringence of Penrose tile QPCF, is 80 times greater than that of Amnan Beenker quasicrystal fiber. We present numerically the existence of endlessly single mode fiber and zero birefringence QPCFs as advantage of employing novel rotational symmetry. © 2017, National Institute of Optoelectronics. All rights reserved
Development of fcc-Al nanoparticles during crystallization of amorphous Al–Ni alloys containing mischmetal: Microstructure and hardness evaluation [electronic resource], Article Materials Science and Engineering A ; Volume 604, 16 May 2014, Pages 92-97 ; Simchi, A ; Varahram, N ; Park, E. S ; Sharif University of Technology
In the present work, fcc-Al nanoparticle development in Al90−xNi10MMx (MM: Ce mischmetal; x=2, 4) amorphous alloys was studied via non-isothermal differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, and nanoindentation test. Results showed that the crystallization of Al88Ni10MM2 alloy occurred by the precipitation of fcc-Al nanoparticles followed by the crystallization of Al11MM3 and Al3Ni phases. Transmission electron microscopy revealed that the aluminum precipitates had an average size of ~12 nm with a round morphology. Increasing the mischmetal content to 4 at% (Al86Ni10MM4 alloy) caused a three-stage crystallization process with a change in the size...
Molybdenum(VI)-oxodiperoxo complex containing an oxazine ligand: Synthesis, X-ray studies, and catalytic activity, Article Journal of Coordination Chemistry ; Vol. 67, issue. 8 , Jul , 2014 , pp. 1429-1436 ; ISSN: 00958972 ; Bagherzadeh, M ; Atabaki, B ; Derakhshandeh, P. G ; Ellern, A ; Woo, L. K ; Sharif University of Technology
A new mononuclear molybdenum(VI)-oxodiperoxo complex [MoO(O 2)2(phox)] with a simple bidentate ligand, 2-(2′-hydroxyphenyl)-5,6-dihydro-1,3-oxazine (Hphox), has been synthesized and characterized by X-ray structure analysis, elemental analysis, infrared, and 1H NMR spectroscopy. A triclinic space group P-1 was determined by X-ray crystallography from single-crystal data of this complex. The resulting complex functioned as a facile sulfide oxidation catalyst with urea hydrogen peroxide as terminal oxidant at room temperature. The catalyst showed efficient reactivity in oxidation of sulfides giving high yield and selectivity
Article Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry ; Volume 42, Issue 7 , May , 2012 , Pages 958-964 ; 15533174 (ISSN) ; Nemati, A ; Hamnabard, Z ; Baghshahi, S ; Golikand, A. N ; Sharif University of Technology
Effect of NaF on crystallization kinetics, microstructure, and mechanical properties of mica glass ceramics were investigated by the differential thermal analysis (DTA), X-ray diffractometry (XRD), scanning electron microscopy (SEM), and microhardness tests. Non-isothermal DTA experiments showed that the crystallization activation energies of base glasses are changed in the range of 235-246 KJ/mol, while the crystallization activation energies of samples with addition of NaF are changed in the range of 263-367 KJ/mol. The increase of crystallization temperature is helpful for the increase of aspect ratio, and the microstructure of the glass ceramics becomes interconnected, which contributes...
Article Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry ; Volume 42, Issue 3 , 2012 , Pages 420-423 ; 15533174 (ISSN) ; Nemati, A ; Sharif University of Technology
The influence of Zr 2 on the crystallization behavior, microstructure, and machinability of SiO 2-Al 2O 3-MgO-K 2O-B 2O 3-F glasses was investigated. The crystallization of the glass-ceramic was markedly affected by addition of ZrO 2. These glasses crystallize more rapidly. The number of mica crystals increases, whereas the size of the mica crystals decreases drastically. Machining of these glass-ceramics was found to be good, as confirmed by a drilling test using conventional steel tools. Such mechanical properties are attributable to the microstructure of these glass-ceramics. Very fine crystals are homogeneously distributed in glass matrix
Controlled crystallization of LTA zeolitic nanoparticles from a clear solution using organic template, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 30, Issue 2 , 2011 , Pages 9-14 ; 10219986 (ISSN) ; Kazemian, H ; Bastani, D ; Sharif University of Technology
LTA Zeolite nanoparticles was successfully synthesized from clear solution under controlled conditions using hydrothermal method using tetramethyl ammonium hydroxide as a structural directing agent. The as-synthesized LTA zeolite particles were characterized by powder X-ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM), Fourier Transform InfraRed (FT-IR) spectroscopy, Energy Dispersive X-ray (EDX) analysis and surface area measuring technique of Brunauer, Emmett and Teller (BET). XRD patterns and FT-IR spectra were ascertained the formation of pure crystalline phase of 4A (i.e. LTA) zeolite. SEM micrograph was shown particles size in the range of 60 -170 nm with uniform...
Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 30, Issue 2 , 2011 , Pages 1-8 ; 10219986 (ISSN) ; Kazemian, H ; Bastani, D ; Sharif University of Technology
This mini review article, intends to provide the essential information about microemulsion technique as a reliable approach toward the synthesis of zeolitic nano crystallites. The strategy discussed here provides a unique, effective, and potentially general methodology to the preparation of uniform and high purity nano crystallites of template-free zeolitic materials including LTA, faujasite type and other zeolitic-like materials (i.e. zeotype materials). Microemulsion is a reliable approach for controlled synthesis of uniform nano sized zeolitic particulates. On the other hand, the microwave assisted microemulsion technique has the advantages of short reaction time, producing smaller and...
Article Australian Journal of Basic and Applied Sciences ; Volume 5, Issue 7 , 2011 , Pages 1064-1069 ; 19918178 (ISSN) ; Faez, R ; Marjani, A ; Sharif University of Technology
In the present work, a new vertical cavity surface emitting laser (VCSEL) structure employing combined oxide layer and single defect photonic crystal index guiding layer has been investigated for L-band optical fiber application. The basic design goal was to obtain photonic crystal VCSEL (PhC VCSEL) with the high power, high slop efficiency and low threshold that operate at 1.55-1.6μm wavelength single mode region. By using the combination of photonic crystal and oxide layer, we have achieved high power VCSEL that operated fundamental mode. The influence of the hole etching depth of photonic crystal looking for the highest power and the lowest threshold current is also investigated
Utilization of DTA in the determination of a crystallization mechanism in transparent glass-ceramics with a nanocrystalline structure, Article Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry ; Volume 41, Issue 5 , 2011 , Pages 561-570 ; 15533174 (ISSN) ; Nemati, A ; Golikand, A. N ; Hamnabard, Z ; Baghshahi, S ; Sharif University of Technology
Non-isothermal differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used to study the nucleation and crystallization behavior of mica glass-ceramics with LiF as nucleating agent. The models enabled establishing the kinetic parameters for crystal growth of individual phases. The activation energies for crystal growth were found to be in the range of 161-301 KJ/mol, 416-424 KJ/mol, and 583-1011 KJ/mol for base glasses, samples with substitution of Li2O for K2O and samples with addition of LiF, respectively. Formation of transparent glass-ceramics from studied glass-samples has been investigated. Transparency is assumed to occur in the...
Article Materials Research Express ; Volume 2, Issue 5 , April , 2015 ; 20531591 (ISSN) ; Khorasani, S ; Sharif University of Technology
Institute of Physics Publishing 2015
We propose a new method, based on variational principle, for the analysis of photonic crystal (PC) slabs. Most of the methods used today treat PC slabs as three-dimensional (3D) crystal, and this makes these methods very time and/or memory consuming. In our proposed method, we use the Bloch theorem to exp and the field on infinite plane waves, whose amplitudes depend on the component perpendicular to the slab surface. By approximating these amplitudes with appropriate functions, we can find modes of PC slabs almost as fast as we can find modes of two-dimensional crystals. In addition to this advantage, we can also calculate radiation modes with this method, which is not feasible with the 3D...
Article Mathematics and Mechanics of Solids ; Volume 21, Issue 8 , 2016 , Pages 1026-1042 ; 10812865 (ISSN) ; Hajian, M ; Assempour, A ; Sharif University of Technology
SAGE Publications Inc
Ideal orientations are one of the material characteristics of the applied mode of deformation. The transfer of material texture to orientations near specific ideal orientations can improve the mechanical properties of the material. In this paper, we focus on the determination of ideal orientations of BCC crystals under the equibiaxial tension mode of deformation. To do this, an Euler space scanning method based on a crystal plasticity approach is presented. In this method some initial orientations which are evenly spaced in the Euler space are selected and their evolutions into the ideal orientations are tracked. The loading is applied incrementally until all of the lattice spin components...
Preparation, crystal structure, and characterization of a polymeric phenol-bridged potassium compound with 2-bromo-4,6-dinitrophenolate, Article Main Group Chemistry ; Volume 8, Issue 1 , 2009 , Pages 11-19 ; 10241221 (ISSN) ; Boghaei, D.M ; McKee, V ; Sharif University of Technology
A polymeric phenolato-bridged potassium compound, K(2-bromo-4,6 dinitrophenolate) (H2O), was obtained by reaction of methylammonium 2-bromo-4,6-dinitrophenolate and potassium chloride in water. 2-bromo-4,6 dinitrophenolate co-ordinates to the metal ion by phenolic O atom, Br, and O atoms of the nitro groups. K+ ion is eleven-coordinate in the compound. Single-crystal X-ray diffraction for methylammonium 2-bromo-4,6-dinitrophenolate and single-crystal X-ray diffraction, elemental analysis, IR, UV-Vis spectra, and fluorescence emission spectra for the complex have also been determined. Methylammonium 2-bromo-4,6-dinitrophenolate was solved in the monoclinic system, space group P21/c, with the...
M.Sc. Thesis Sharif University of Technology ; Khorasani, Sina
In the recent years, photonic crystal (PhC) devices vastly have been paid attention due to their ignorable loss, very low group velocity, flexibility in shape and dimension.In this thesis a PhC coupled cavity ring known as superresonator is introduced and its properties and applications is studied. Also modes of the structure are extracted through both coupled-resonator model and FDTD method, and two of its application is described and studied. Add-drop filter is one of the essential devices in WDM systems. First, an application of superresonator in designing add-drop filters is explained and a novel filter based on the superresonator is introduced and analyzed by FDTD and coupled mode...
A kinetic study of facile fabrication of MIL-101(Cr) metal-organic framework: effect of synthetic method, Article Inorganica Chimica Acta ; Volume 471 , 2018 , Pages 513-520 ; 00201693 (ISSN) ; Kazemeini, M ; Sharif University of Technology
Elsevier S.A 2018
MIL-101(Cr) metal–organic framework samples were successfully synthesized through the conventional electrical heating (CE), ultrasound (US), and microwave (MW) synthetic methods at three different temperatures and various synthesis times. These were done with the aim of understudying the crystallization kinetics of these complex MIL's structures. The nucleation and crystal growth steps were thus, quantified through measuring the relative crystallinity of the prepared MIL-101(Cr) utilizing the PXRD and FESEM analysis under various synthesis conditions. In addition, the textural properties of the fully crystallized samples measured through the N2 adsorption–desorption isotherms at 77 K. The...
Numerical study on the effects of main BCC rolling texture components on the formability of sheet metals, Article International Journal of Advanced Manufacturing Technology ; Volume 80, Issue 1-4 , March , 2015 , Pages 245-253 ; 02683768 (ISSN) ; Assempour, A ; Sharif University of Technology
Springer-Verlag London Ltd 2015
Crystallographic texture considerably affects the formability of crystalline materials. In this paper, the effects of BCC ideal rolling fibers—including α, ε, η, γ, and ξ fibers—on the sheet formability are numerically studied. The simulations are based on the numerical procedure developed by the authors in  in which a rate dependent crystal plasticity model along with the power law hardening are employed in a user material subroutine to model the behavior of crystalline materials. In order to determine FLD—in a M-K type approach—second-order derivative of sheet thickness variations with respect to time is used as necking criterion. The calculated FLDs of the fibers are compared with each...
Article Journal of Lightwave Technology ; Volume 35, Issue 17 , 2017 , Pages 3734-3742 ; 07338724 (ISSN) ; Khorasani, S ; Sharif University of Technology
Today's standard fabrication processes are just capable of manufacturing slab of photonic and phononic crystals, so an efficient method for analysis of these crystals is indispensable. Plane wave expansion (PWE) as a widely used method in studying photonic and phononic (phoxonic) crystals in full three dimensions is not suitable for slab analysis in its standard form, because of convergence and stability issues. Here, we propose a modification to this method which overcomes these limitations. This improved method can be utilized for calculation of both photonic and phononic modes in phoxonic slabs. While in the standard three-dimensional PWE, Fourier series are used to estimate the field...
Article Bulletin of Materials Science ; Volume 35, Issue 5 , October , 2012 , Pages 853-858 ; 02504707 (ISSN) ; Nemati, A ; Sharif University of Technology
Formation of machinable glass-ceramic in the system MgO-SiO 2-Al2O3-K2O-B2O 3-F with and without addition of MgF2 has been investigated. Crystallization of glass sample was done by controlled thermal heat treatment at nucleation and crystallization temperatures. The results showed that MgF2 in high concentration had a synergistic effect and enhanced the formation of interlockedmica crystals. Non-isothermal DTA experiments showed that the crystallization activation energies of base glasses were changed in the range of 235-405 kJ/mol, while the crystallization activation energies of samples with addition of MgF2 were changed in the range of 548-752 kJ/mol