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precipitation
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In-situ fabrication of nanosheet arrays on copper foil as a new substrate for binder-free high-performance electrochemical supercapacitors
, Article Journal of Electroanalytical Chemistry ; Volume 802 , 2017 , Pages 48-56 ; 15726657 (ISSN) ; Shahrokhian, S ; Sharif University of Technology
Abstract
A facile hydrothermal method and subsequent electroactivation have been developed to fabricate three-dimensional (3D) CuO nanosheet arrays on the copper foil substrate, which can be used directly as a binder-free electrode for supercapacitor applications. Under optimum conditions, by using this facile method, a high capacitance of 125 mF/cm2 at a current density of 0.3 mA/cm2 is obtained. The prepared supercapacitor showed a good rate capability (46.4% capacitance retention, when the current density is increased to more than 30 times) and an excellent cyclability (more than 88% capacitance retention after 3000 cycles). © 2017 Elsevier B.V
Evolution of microstructure of nickel base superalloy at high temperatures
, Article Materials Science and Technology ; Volume 22, Issue 8 , 2006 , Pages 888-898 ; 02670836 (ISSN) ; Nategh, S ; McLean, M ; Sharif University of Technology
2006
Abstract
The evolution of primary and secondary γ′ precipitates in the high γ′ volume fraction Rene 80 Ni based superalloy has been examined during aging at elevated temperatures for periods up to 1750 h. While the increase in average dimension of particles followed the cube rate Lifshitz, Slypzof and Wagner (LSW) law, rt-3-r0 -3=kt, there were significant discrepancies between the experimental and theoretical particle size distributions (PSDs) and inconsistency with the kinetic constants associated with the two populations of particles. These differences are attributed to the influence of elastic coherency strains which have not been considered in conventional capillarity driven coarsening models....
Precipitate strengthening of pyramidal slip in Mg–Zn alloys
, Article Materials Science and Engineering A ; Volume 804 , 2021 ; 09215093 (ISSN) ; Wang, J ; LLorca, J ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The mechanical properties of Mg-4wt.% Zn alloy single crystals along the [0001] orientation were measured through micropillar compression at 23 °C and 100 °C. Basal slip was dominant in the solution treated alloy, while pyramidal slip occurred in the precipitation hardened alloy. Pyramidal dislocations pass the precipitates by forming Orowan loops, leading to homogeneous deformation and to a strong hardening. The predictions of the yield stress based on the Orowan model were in reasonable agreement with the experimental data. The presence of rod-shape precipitates perpendicular to the basal plane leads to a strong reduction in the plastic anisotropy of Mg. © 2020 Elsevier B.V
Precipitate strengthening of pyramidal slip in Mg–Zn alloys
, Article Materials Science and Engineering A ; Volume 804 , 2021 ; 09215093 (ISSN) ; Wang, J ; LLorca, J ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The mechanical properties of Mg-4wt.% Zn alloy single crystals along the [0001] orientation were measured through micropillar compression at 23 °C and 100 °C. Basal slip was dominant in the solution treated alloy, while pyramidal slip occurred in the precipitation hardened alloy. Pyramidal dislocations pass the precipitates by forming Orowan loops, leading to homogeneous deformation and to a strong hardening. The predictions of the yield stress based on the Orowan model were in reasonable agreement with the experimental data. The presence of rod-shape precipitates perpendicular to the basal plane leads to a strong reduction in the plastic anisotropy of Mg. © 2020 Elsevier B.V
Manufacturing And Investigation Of Microstructure, Precipitation Hardening And Tarnishing Of Ag-Cu-Ge Argentium® Alloy
, M.Sc. Thesis Sharif University of Technology ; Abbachi, Parvin (Supervisor) ; Hamdi, Farzad (Supervisor)
Abstract
In this study melting and casting process of Ag-6.3%wt Cu-1.2%wt Ge alloy with NaBH4 additive for grain refining was investigated. ICP and XRF chemical analysis was used for calculating of Boron and Germanium lost in the processing section then an appropriate route for manufacturing of this alloy was suggested. With SEM and EDS chemical analysis which was installed on SEM sample’s microstructures after cold work and heat treatment was investigated. Solidification’s phases were identified with using DTA, XRD and EDS. To introduce a mechanism for increasing of tarnishing resistance in Argentium alloy, XPS analysis were employed. Optical microscope images reveals that casting samples with grain...
Effect of Coprecipitation and Hydrothermal Parameters on the Properties of Ferrofluids Based on Magnetite Nanoparticles as MRI Contrast Agent
, Ph.D. Dissertation Sharif University of Technology ; Madaah Hosseini, Hamid Reza (Supervisor)
Abstract
Ferrofluids are special stable suspensions of magnetic nanoparticles dispersed in liquid phase. These materials have numerous biological applications such as drug delivery, magnetic hyperthermia and magnetic resonance imaging due to their special magnetic properties and fluidity. Particle size and magnetic properties of ferrofluids have an important role in these applications. In this work, magnetite-based ferrofluids have been synthesized via coprecipitation and hydrothermal methods. In the coprecipitation process, cysteine and dextran surfactants have been used as ferrofluid stabilizer and effect of synthesize temperature, time, pH and surfactant concentration have been investigated on...
A novel method for mitigation of asphaltene deposition in the wellstring
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 29, Issue 2 , 2010 , Pages 131-142 ; 10219986 (ISSN) ; Rashtchian, D ; Tohidi, B ; Jamialahmadi, M ; Sharif University of Technology
2010
Abstract
Asphaltene precipitation and deposition is a serious problem in many Iranian fields. The deposited asphaltene results in partial or total blockage of the wellbore and wellstring reducing or completely seizing oil production. This paper studies the asphaltene problem and mitigation methods in wellstring systematically. It presents new approach based on the combination of thermodynamic modeling of asphaltene precipitation with hydrodynamic well modeling. The developed model is capable to determine the asphaltene precipitation and deposition interval through the wellstring. Therefore, it could study the effect of hydrodynamic parameters such as wellhead pressure, well flow-rate and tubing size...
Mercury ion adsorption on AC@Fe3O4-NH2-COOH from saline solutions: Experimental studies and artificial neural network modeling
, Article Korean Journal of Chemical Engineering ; Volume 35, Issue 3 , 2018 , Pages 671-683 ; 02561115 (ISSN) ; Zabihi, M ; Shayegan, J ; Fatehi, M. H ; Sharif University of Technology
Springer New York LLC
2018
Abstract
An efficient, novel functionalized supported magnetic nanoparticle (AC@Fe3O4-NH2-COOH) has been synthesized by co-precipitation method for removal of mercury ions from saline solutions. High dispersed supported magnetic nanoparticles with particle sizes less than 30 nm were formed over activated carbon derived from local walnut shell. Surface characterizations of supported magnetic nanoparticles were evaluated by Boehm test, Brunauer- Emmett-Teller (BET) surface area, X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and X-ray fluorescence (XRF). A three-layer artificial neural network (ANN) code...
Developing a novel colloidal model for predicting asphaltene precipitation from crude oil by alkane dilution
, Article Journal of Molecular Liquids ; Volume 318 , 2020 ; Badizad, M. H ; Dehghanizadeh, M ; Saeedi Dehaghani, A. H ; Sharif University of Technology
Elsevier B.V
2020
Abstract
This research aims to propose a thermodynamic model for predicting asphaltene precipitation upon diluting a crude oil with a paraffinic solvent. To this end, a thorough mathematical formulation was carried out to derive a novel micellization model based on the associative properties of asphaltenic compounds. It was assumed that asphaltenes exist in the oil both as monomeric molecules and aggregated cores; with stabilization latter by attachment of resin on its periphery. The aggregation equilibrium was established by taking into account asphaltene's lyophobic tendency, heat of resin adsorption, and interfacial tension between micelle and oil media which is the main driving factor...
Fractal behaviour of flow of inhomogeneous fluids over smooth inclined surfaces
, Article Journal of Physics Condensed Matter ; Volume 16, Issue 15 , 2004 , Pages 2497-2505 ; 09538984 (ISSN) ; Ghane Motlagh, B ; Baradaran, S ; Shekarian, E ; Rouhani, S ; Sharif University of Technology
2004
Abstract
Patterns formed by the flow of an inhomogeneous fluid (suspension) over a smooth inclined surface were studied. It was observed that fractal patterns form. There exists a threshold angle for the inclination above which global fractal patterns are formed. This angle depends on the particle size of the suspension. We observed that there are two fractal dimensions for these patterns, depending on the area from which the pattern is extracted. If the pattern is taken from the top which only consists of the beginning steps of the pattern forming, one finds two fractal dimensions, i.e. 1.35-1.45 and 1.6-1.7, in which the first one is dominant while, if the entire pattern is taken, then a fractal...
The Effect of Heat Treatment on Microstructure and Mechanical Properties of Directionally Solidified Nickel-based Superalloy GTD-111
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor)
Abstract
The Ni-based superalloy GTD-111 possesses excellent hot corrosion resistance, high stability and strength at elevated temperature; accordingly, the alloy is used in manufacturing of the first stage blades of powerful gas turbines. In this study, effect of withdrawal rate from Bridgman furnace and precipitation hardening on the microstructure and microhardness of this superalloy were investigated. To this end, several experiments were carried out under growth rates of 1, 6 and 10 mm/min using Bridgman process under vacuum. Afterwards, the effects of homogenization treatment, partial dissolution with two different cooling rates (air and water) along with aging on the microstructure were...
Asphaltene Onset Prediction Using CEOS
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Cyrous (Supervisor) ; Jafari Behbahani, Taraneh (Supervisor)
Abstract
One of the main problems associated with the oil production is asphaltene precipitate in the reservoirs. In order to plan for the EOR methods, production scenario, and selection of completion technology, it is necessary to study the initiation of asphaltene precipitation called onset. Since the experimental methods is not only is so expensive and time consuming, the required materials are not available. Consequently, modeling approaches as new methods are proper substitutes for laboratory procedure. These methods need less costs and time and higher accuracy compared to the experimental investigations which are the advantages of these methods. Computational operations for onset determination...
Experimental study of asphaltene precipitation behavior during miscible carbon dioxide injection
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Vol. 36, issue. 14 , July , 2014 , pp. 1523-1530 ; ISSN: 15567036 ; Nakhli, H ; Kharrat, R ; Ghazanfari, M. H ; Aghajani, M ; Sharif University of Technology
Abstract
Many reservoir and production engineers face asphaltene precipitation as a major problem during miscible carbon dioxide flooding projects. Experimental studies regarding asphaltene precipitation are therefore employed to assist in selecting appropriate facilities and proper operation schemes. During this study, a series of high pressure, high temperature experiments are designed and performed to analyze asphaltene precipitation behavior of an Iranian light reservoir crude at reservoir conditions due to natural production and miscible CO2 gas injection. For both sets of experiments, two different temperature levels (including reservoir temperature) are selected to investigate the role of...
Process optimization for mineral carbonation in aqueous phase
, Article International Journal of Mineral Processing ; Vol. 130 , July , 2014 , pp. 20-27 ; ISSN: 03017516 ; Shayegan, J ; Bu, J ; Yeo, T. Y ; Sharratt, P ; Sharif University of Technology
Abstract
Carbon dioxide sequestration by a pH-swing carbonation process was considered in this work. A multi-step aqueous process is described for the fractional precipitation of magnesium carbonate and other minerals in an aqueous system at room temperature and atmospheric pressure. With the aim to achieve higher purity and deliver more valuable mineral products, the process was split into four steps. The first step consists of Mg leaching from the magnesium silicate in a stirred vessel using 1 M HCl at 80 °C, followed by a three step precipitation in reactors in sequence to remove Fe(OH)3, then Fe(OH)2 and other divalent ions, and finally MgCO3 nucleation and growth. Hydrated magnesium carbonate...
Microstructure based modelling of flow behaviour of Al-Mg-Si alloy at different temper conditions
, Article Materials Science and Technology (United Kingdom) ; Volume 29, Issue 8 , 2013 , Pages 968-974 ; 02670836 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
2013
Abstract
A new integrated physically based constitutive model was developed for an age hardenable Al- Mg-Si alloy. The kinetics of precipitation during various stages of aging was modelled. The precipitate features consisted of particle radius and volume fraction obtained from the kinetics model, which was used to compute the alloy yield strength/hardness. A published multiinternal variable workhardening model was improved to take into account the effects of solute solution and precipitates on the alloy hardening capacity after performing different cycles of aging treatment. The flow curves and hardness predicted by the model were in good agreement with the experimental results. The model is able to...
Characterization of PVDF/Nanoclay Nanocomposites Prepared by Melt, Solution, and Co-Precipitation Methods
, Article International Journal of Polymer Analysis and Characterization ; Volume 17, Issue 4 , 2012 , Pages 291-301 ; 1023666X (ISSN) ; Dadbin, S ; Frounchi, M ; Sharif University of Technology
2012
Abstract
Poly (vinylidene fluoride) (PVDF) nanocomposites were prepared via melt, solution, and co-precipitation mixing methods using Cloisite 30B as organoclay. The results from X-ray diffraction patterns display intercalation or exfoliation of nanoclay depending on the nanocomposite preparation method. The solvent cast and co-precipitated samples showed exfoliation, while intercalation was observed in the nanocomposites prepared by melt mixing. Introducing organoclay induced formation of β-crystals in the PVDF nanocomposites as evidenced by XRD and FT-IR. FT-IR analysis indicated that the samples prepared by the co-precipitation method had a higher tendency for β phase formation, while the sample...
Modeling of uranium bioleaching by Acidithiobacillus ferrooxidans
, Article Annals of Nuclear Energy ; Volume 43 , May , 2012 , Pages 13-18 ; 03064549 (ISSN) ; Safdari, J ; Roosta Azad, R ; Zokaei Kadijani, S ; Sharif University of Technology
2012
Abstract
In this paper, a mathematical model for the mesophilic bioleaching of uraninite is developed. The case of constant temperature, pH, and initial ore concentration is considered. The model is validated by comparing the calculated and measured values of uranium extraction, ferric and ferrous iron in solution, and cell concentration. Good fits of the model were obtained, while the values of the parameters were within the range expected. New rate expressions were used for the iron precipitation and uranium leaching rates. The rates of chemical leaching and ferric precipitation are related to the ratio of ferric to ferrous in solution. The fitted parameters can be considered applicable only to...
Changes of γ′ precipitate characteristics in damaged superalloy IN738LC during different stages of rejuvenation heat treatment cycles
, Article Materials Science and Technology ; Volume 28, Issue 2 , Nov , 2012 , Pages 213-219 ; 02670836 (ISSN) ; Nategh, S ; Ekrami, A. A ; Sharif University of Technology
2012
Abstract
The present study investigates the evolution of γ′ precipitate microstructure in a creep damaged IN738LC superalloy during different stages of rejuvenation heat treatment cycles. Dissolution of coarsened γ′ precipitates in the creep damaged alloy occurred during different solution treatments. The precipitates that did not dissolve completely during solution treatment and those formed during subsequent cooling were considered to be as remnant and cooling precipitates respectively. It was found that higher solution treatment temperatures result in lower volume fraction of remnant precipitates and further formation of cooling precipitates. Slower cooling rates after solution treatment gave the...
Influence of double aging on microstructure and yield strength of AEREX ™ 350
, Article Materials Science and Engineering A ; Volume 534 , 2012 , Pages 547-551 ; 09215093 (ISSN) ; Sharif University of Technology
Abstract
Age hardening behavior of selected samples of AEREX ™ 350, a nickel-cobalt based superalloy, was investigated in this article. The relationship between the microstructure and mechanical properties was elucidated using hardness and compression testing methods and optical, scanning and transmission electron microscopy techniques. It was found that the microstructure is sensitive to the temperature of the solution and the aging treatments. This approach may be used to optimize the microstructure of the alloy for different applications
Treatment of oilfield produced water by dissolved air precipitation/solvent sublation
, Article Journal of Petroleum Science and Engineering ; Volume 80, Issue 1 , 2011 , Pages 26-31 ; 09204105 (ISSN) ; Shayegan, J ; Noorjahan, A ; Sharif University of Technology
Abstract
Dissolved air precipitation/solvent sublation (DAP/SS) was used for treatment of simulated and real oilfield produced water to generate very fine bubbles which are necessary for effective separation. In this method micro bubbles produced by saturation of air in a pressurized packed column were released in an atmospheric column leading the bubbles to raise resulting trapped contaminants in the Gibbs layer around them to be removed by a layer of immiscible solvent at the top of column. The method was conducted to solutions including Benzene, Toluene and Chlorobenzene (ClB) as part of BTEX contaminants in produced water, mixture of them as simulated produced water and real oilfield produced...