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A novel approach for preparation of CL-20 nanoparticles by microemulsion method
, Article Journal of Molecular Liquids ; Vol. 193, issue , May , 2014 , pp. 83-86 ; Zarandi, M ; Zarei, M. A ; Soleyman, R ; Zeynali, V ; Sharif University of Technology
Abstract
2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) as one of the high energy cage nitramines has been used in various propellants and explosive formulations. The performance of energetic materials depends on its particle size and shape. Therefore, in this research, microemulsion method has been applied for the preparation of CL-20 nanoparticles via oil in water (O/W) microemulsions. The optimized formulation contains water 45%, n-butyl acetate 20.5%, sodium dodecyl sulfate (SDS, as anionic surfactant) 6.5% and 2-propanol (as co-surfactant) 26.5%. CL-20 nanoparticles that were obtained by microemulsion method are spherical with an average diameter of 25 nm, based on TEM image....
Kinetics of pressure oxidative leaching of molybdenite concentrate by nitric acid
, Article Hydrometallurgy ; Volume 111-112, Issue 1 , January , 2012 , Pages 52-57 ; 0304386X (ISSN) ; Yoozbashizadeh, H ; Mozammel, M ; Sadrnezhaad, S. K ; Sharif University of Technology
2012
Abstract
The current study was carried out to investigate the kinetics of reactions for the pressure oxidative leaching of a molybdenite concentrate in less than one hour. The effects of oxygen pressure, stirring speed, pulp density, acid concentration and temperature on the leaching rate of the molybdenum were studied. It was found that about 85% of molybdenite was oxidized to molybdic oxide precipitate with remaining molybdenum dissolved in the leaching liquor. Analysis of experimental data showed that the reaction is chemically controlled with activation energy of 68.8 kJ/mol. Furthermore SEM images showed no significant boundary diffusion layer and it was noted that the molybdic oxide...
Reagent-free facile synthesis of silver nanoparticles/nanorods hybrid
, Article Proceedings of the IASTED International Conference on Nanotechnology and Applications, NANA 2010, 1 November 2010 through 3 November 2010, Cambridge, MA ; 2010 , Pages 498-501 ; 9780889868625 (ISBN) ; Soleyman, R ; Pourjavadi, A ; Sharif University of Technology
2010
Abstract
Silver nanostructures are very important agents in biomedical research, because of its unique activity against unfavorable processes in bioscience. In the current study, reagent-free facile preparation of silver nanoparticles (average diameter: 72 nm) and silver nanoparticles/ nanorods hybrid was reported via wet chemical synthesis method. Kappa-carrageenan (kC), a hydrophilic biopolymer with sulphate groups on its backbone, as capping agent was used in the reaction medium. Silver nanoparticles and silver nanoparticles/ nanorods formation was confirmed by SEM images. Further investigations were carried out using DLS data and GPC analysis
Air quenching as a reliable technique to obtain colossal dielectric constant with low loss in (In, Nb)-co doped TiO2
, Article Materials Letters ; Volume 267 , May , 2020 ; Mahmoudi, P ; Karimi, A ; Sharif University of Technology
Elsevier B. V
2020
Abstract
In this research, for the first time, the effect of air quenching on the microstructural and electrical properties of (In, Nb) co-doped TiO2 was investigated. The FE-SEM images showed that the air quenching has no effect on microstructure of co-doped TiO2. However, air quenching affected the electrical properties so that the dielectric constant in the frequency of 1 kHz at room temperature sharply enhanced from 21*103 to 26*104 and the dielectric loss surprisingly decreased from 0.6 to 0.1. This incredible improvement in the dielectric properties is attributed to the electron-pined defect dipoles which has been activated through air quenching. © 2020 Elsevier B.V
Effect of NaOH on the structure and corrosion performance of alumina and silica PEO coatings on aluminum
, Article Journal of Materials Engineering and Performance ; Volume 21, Issue 10 , October , 2012 , Pages 2195-2202 ; 10599495 (ISSN) ; Ehteshamzadeh, M ; Mirhosseini, S. M. M ; Sharif University of Technology
Springer
2012
Abstract
The effect of NaOH content of electrolyte on the properties of ceramic coatings, produced in silicate solution, was studied. Morphology, chemical analysis, phase composition, and cross-section of the ceramic coatings were investigated by SEM, EDS, XRD, and OM, respectively. The corrosion resistance and corrosion mechanism were also studied using potentiodynamic polarization and electrochemical impedance spectroscopy in a 3.5% NaCl solution. To study the surface roughness, a brightness SEM image analysis method was used. Results suggested that increasing the NaOH concentration of sediment production size causes thickness and coating roughness to decrease. The lowest corrosion rate belonged to...
Effect of synthesis conditions on performance of a hydrogen selective nano-composite ceramic membrane
, Article International Journal of Hydrogen Energy ; Volume 37, Issue 20 , October , 2012 , Pages 15359-15366 ; 03603199 (ISSN) ; Safekordi, A ; Ganji Babakhani, E ; Zamaniyan, A ; Heidari, M ; Sharif University of Technology
Elsevier
2012
Abstract
A hydrogen-selective nano-composite ceramic membrane was prepared by depositing a dense layer composed of SiO2 and Al2O 3 on top of a graded multilayer substrate using co-current chemical vapor deposition (CVD) method. The multilayer substrate was made by dip-coating a macroporous α-alumina tubular support by a series of boehmite solutions to get a graded structure. Using DLS analysis, it was concluded that decreasing hydrolysis time and increasing acid concentration lead to smaller particle size of boehmite sols. XRD analysis was carried out to investigate the structure of intermediate layer and an optimized calcination temperature of 973 K was obtained. SEM images indicated the formation...
Investigation into characteristics of Portevin-Le Chatelier effect of an Al-Mg Alloy
, Article Journal of Materials Engineering and Performance ; Volume 19, Issue 9 , 2010 , Pages 1264-1267 ; 10599495 (ISSN) ; Sharif University of Technology
Abstract
In this study, the plastic instabilities associated with the Portevin-Le Chatelier (PLC) and their effects on the mechanical properties and the fracture surfaces have been investigated for AA 5083. Tensile tests were performed at various temperatures and strain rates in order to do so. Then, serrated and smooth yielding domains were determined in Ln ε̇-1/T diagram. The stress-strain curves related to the serrated domain show the values of flow stress decreases by increasing the strain rate at a constant temperature. In addition, the plot of critical strain versus imposed strain rate indicates an inverse manner at very low strain rates. It is confirmed that the type of PLC bands alters the...
The effects of annealing phenomena on the energy absorption of roll-bonded Al-steel sheets during wedge tearing
, Article Materials Science and Engineering A ; Volume 527, Issue 27-28 , 2010 , Pages 7329-7333 ; 09215093 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
Abstract
The purpose of this paper is to investigate the effects of annealing phenomena on the energy absorption of Al-steel bilayer sheets, bonded by cold rolling, through wedge tearing. Tearing by wedge is a dissipating energy system that includes three components: cutting, friction and plastic deformation due to bending. In order to find the bonding and annealing effects on energy absorption, the non-bonded bilayer sheets are prepared in the same condition of bonded ones. The results show that energy absorption of bonded sheets is larger than that of non-bonded ones. This is due to different plastic bending moment of bonded and non-bonded bilayer sheets. Whenever the bond is improved by heat...
Dynamic modeling of the formation damage and mud cake deposition using filtration theories coupled with SEM image processing
, Article Journal of Natural Gas Science and Engineering ; Volume 42 , 2017 , Pages 157-168 ; 18755100 (ISSN) ; Salehi, S ; Sharif University of Technology
Elsevier B.V
2017
Abstract
In the present paper, a dynamic modeling is presented for deposition of the mud solid particles over and through the porous sandstones during permeability plugging experiments. Scanning electron microscopy (SEM) coupled with image processing are utilized to find the porosity and pore size distribution of the mud cake. The structure of the porous rock as well as the mud cake are modeled via bundle of the curved tubes approach and deposition probability of the solid particles has been taken into the account through filtration theories. Four different sandstones in addition to four mud samples were utilized to measure and predict the volume of the expelled fluid during the 30 min of filtration...
Stability, size and optical properties of colloidal silver nanoparticles prepared by electrical arc discharge in water
, Article EPJ Applied Physics ; Volume 48, Issue 1 , 2009 , Pages 10601p1-10601p7 ; 12860042 (ISSN) ; Iraji Zad, A ; Ahadian, M. M ; Hormozi Nezhad, M. R ; Sharif University of Technology
2009
Abstract
We have fabricated and characterised colloidal silver nanoparticles by the electrical arc discharge method in DI water. Size and optical properties of the silver nanoparticles were studied versus different arc currents. Optical absorption indicates a plasmonic peak at 392 nm for 10 A which increases to 398 nm for 20 A arc current. This reveals that by raising the arc current the size of the nanoparticles increases. Optical absorption of silver nanoparticles after 3 weeks shows precipitation of them in a water medium. The effect of different surfactant and stabilizer concentrations such as cethyl trimethylammonium bromide (CTAB), polyvinyl pyrrolidone (PVP), sodium citrate, sodium dodecyl...
Comparison of various anodization and annealing conditions of titanium dioxide nanotubular film on MB degradation
, Article EPJ Applied Physics ; Volume 47, Issue 1 , 2009 ; 12860042 (ISSN) ; Iraji Zad, A ; Ahadian, M. M ; Taghavinia, N ; Dolati, A ; Sharif University of Technology
2009
Abstract
In this study the influence of morphology of vertically oriented titanium oxide nanotube arrays (TNTAs) on their photocatalytic activities was investigated. To obtain nanotubes with different morphologies, they were prepared at different anodization voltages. The size of TNTAs were measured using SEM images and also determined based on a non-destructive optical method; We demonstrate how the tubular geometry of the TNTAs can be used to adjust the optical and also the wetting properties of them and how these properties affect the performance of the nanostructure in further applications as a photocatalyst. To investigate their potentials for environmental applications, the photocatalytic...
Rapid and efficient synthesis of colloidal gold nanoparticles by arc discharge method
, Article Applied Physics A: Materials Science and Processing ; Volume 96, Issue 2 , 2009 , Pages 423-428 ; 09478396 (ISSN) ; Iraji zad, A ; Mahdavi, M ; Ahadian, M. M ; Hormozi nezhad, M. R ; Sharif University of Technology
2009
Abstract
We report a simple, inexpensive and one-step synthesis route of colloidal gold nanoparticles using arc discharge between titanium electrodes in HAuCl 4 solution achieving long-time stability. Gold nanoparticles of 8 nm diameter were formed during reduction of HAuCl4 in the plasma discharge zone. The resulting nanoparticles were characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Optical absorption spectroscopy of as prepared samples at 15 A arc current in HAuCl4 solution shows a surface plasmon resonance around 550 nm. It was found that sodium citrate acts as a stabilizer and surface capping agent of the colloidal...
Fabrication of biocompatible titanium scaffolds using space holder technique
, Article Journal of Materials Science: Materials in Medicine ; Volume 23, Issue 10 , 2012 , Pages 2483-2488 ; 09574530 (ISSN) ; Sadrnezhaad, S. K ; Shokrgozar, M. A ; Bonakdar, S ; Sharif University of Technology
Springer
2012
Abstract
Open-pore titanium scaffolds were fabricated by sintering of compressed mixtures of TiH1.924 and urea. Spherical and irregular shaped space holders were used to investigate the effect of pore shape on cellular behavior. After removal of the space holder, the shape of the spacers was replicated to the pores. Average diameter of the pores was in the range of 300-600 lm. SEM images showed that titanium hydride resulted in higher surface roughness and larger micro porosities than pure titanium. In vitro evaluationswere carried out by using MTT assay, measuring alkaline phosphatase activity and alizarin red staining in flow perfusion bioreactor for cell culture. Observations revealed excellent...