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Modeling of Dissolution of Sluge from Evaporation Lagoons of Isfahan's UCF Plant
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor) ; Charkhi, Amir (Supervisor) ; Otukesh, Mohammad (Co-Advisor)
Abstract
Uranium conversion process is one of the most important stages in nuclear fuel cycle. The Uranium Conversion Facilities (UFC) of Iran is located in Isfahan. In this plant, the Yellowcake (impure uranium oxide, U3O8) is converted to Uranium hexa-fluoride, UF6. During the process, considerable amounts of uranium-containing liquid waste are generated. This liquid waste was collected in evaporation pools inside the UCF Plant. In the course of time, a thick layer of precipitated salt form in bottom of the pools which are collected and stored in drums inside a building. This solid waste contains uranium at concentration levels much higher than that permitted for land disposal of the waste....
Detailed Kinetic Study of Acid Leaching of Uranium ore and Derivation of a Scalable Mathematical Model for it
, M.Sc. Thesis Sharif University of Technology ; Otukesh, Mohammad (Supervisor) ; Karimi Sabet, Jadad (Supervisor) ; Ghodsinejad, Davood (Co-Supervisor)
Abstract
The leaching process is the first stage in the process of extracting uranium out of the ore. The leaching, based on the used material is divided into two main methods of acidic and alkali leaching. Each of these two techniques have their own pros and cones. It is notable that due to lower costs, and faster kinetics, the acid leaching is the first option of the mines unless the percentage of carbonates (and the other acid-soluble materials) in the ore are too high that makes this process uneconomical because of higher acid consumption. The kinetics of the acid leaching of the uranium depends on various parameters such as acid concentration, the particle size, exposure time and the temperature...
The Effect of Warm Multi -directional Forging on Microstructure and Strength of 2024 Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Kazeminezhad, Mohsen (Supervisor)
Abstract
The 2024 aluminum alloy is deformed by two passes of multi-directional forging at room temperature, 180 oC, 250 oC, 320 oC and 380 oC with initial state of solid solution. Microstructure, mechanical properties and the state of precipitates are investigated via optical and scanning electron microscopies, hardness test, shear punch test and differential scanning calorimetry. Fragmentation and distribution of the precipitates are observed after straining at different temperatures. Dynamic precipitation of GPB zones at room temperature and 180 oC are studied by DSC analysis. The increase of both hardness and strength and the formation of shear bands are related to the presence of GPB zones....
Simulation of Carbonate Matrix Acidizing Using Arbitrary Lagrangian Eulerian (ALE)at Darcy Scale
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Saeed (Supervisor) ; Bazargan, Mohammad (Supervisor)
Abstract
Injection of acid into the carbonate rock dissolves the rock, and the porous medium is constantly changing. As a result, the boundaries between the acid and the porous medium, which are in fact the interface between the solid phase and the liquid phase, are constantly changing. Therefore, on the issue of acid injection into carbonate rock, we are facing dynamic boundary conditions. Also, due to the simultaneous solution of transfer and reaction phenomena, modeling acid injection into carbonate rock faces many challenges.In such problems, the ALE method, which is a combination of the best features of the Lagrangian method and the Eulerian method, offers a very precise solution and is used as...
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...
Hot corrosion behavior and near-surface microstructure of a “low-temperature high-activity Cr-aluminide” coating on inconel 738LC exposed to Na2SO4, Na2SO4 + V2O5 and Na2SO4 + V2O5 + NaCl at 900 °C
, Article Corrosion Science ; Volume 128 , 2017 , Pages 42-53 ; 0010938X (ISSN) ; Ghasemi, B ; Sadrnezhaad, S. K ; Habibollahzadeh, A ; Jafarzadeh, K ; Sharif University of Technology
Abstract
Hot corrosion is a serious problem in gas turbines due to poor quality fuels which contain Na, V, S and Cl. To resolve the problem, Cr-aluminide was coated on IN-738LC superalloy with a two steps pack cementation process. Oxidation behavior and near-surface microstructure of the coating showed consecutive increase in destruction by exposition to Na2SO4, 75Na2SO4 + 25 V2O5 and 70Na2SO4 + 25 V2O5 + 5NaCl (wt.%). Kinetic studies indicated parabolic corrosion rate in salt-less samples due to diffusion. Similar expression for salt-covered samples was assessed for oxide dissolution. Plate-like, broken-plate-like and cauliflower-like morphologies attributed to the corrosion products were observed...
An electrochemical synthesis of reduced graphene oxide/zinc nanocomposite coating through pulse-potential electrodeposition technique and the consequent corrosion resistance
, Article International Journal of Corrosion ; Volume 2018 , 2018 ; 16879325 (ISSN) ; Afshar, A ; Yaghoubinezhad, Y ; Sharif University of Technology
Hindawi Limited
2018
Abstract
Pulse-potential coelectrodeposition of reduced graphene oxide/zinc (rGO-Zn) nanocomposite coating is directly controlled upon a steel substrate from a one-pot aqueous mixture containing [GO-/Zn2+]δ+ nanoclusters. GO nanosheets are synthesized by modified Hummer's approach while Zn cations are produced in the solution and deposited on GO nanosheets using anodic dissolution technique. Eventually, nanoclusters are reduced to rGO-Zn film through an electrochemical process. Chemical composition, surface morphology, and corrosion resistance of the thin film are characterized. Results show that the corrosion resistance of rGO-Zn coating is approximately 10 times more than the bare steel. © 2018 S....
A precipitation-hardening model for non-isothermal ageing of Al-Mg-Si alloys
, Article Computational Materials Science ; Volume 45, Issue 2 , 2009 , Pages 385-387 ; 09270256 (ISSN) ; Bahrami, A ; Mousavi Anijdan, S. H ; Sharif University of Technology
2009
Abstract
An age-hardening model has been developed to predict the evolution of the hardness of Al-Mg-Si alloys during non-isothermal ageing before peak age. The concurrent precipitation and dissolution have been considered in the structural model. Then the structural model has been combined with strengthening model to predict the precipitation-hardening behavior of the alloy AA6061. The results indicate that the developed model can be used as a predictive tool to model the mechanical properties evolution of Al-Mg-Si alloys during non-isothermal heat treatment. © 2008 Elsevier B.V. All rights reserved
Preparation and characterization of porous chitosan–based membrane with enhanced copper ion adsorption performance
, Article Reactive and Functional Polymers ; Volume 154 , 2020 ; Soltanieh, M ; Mousavi, S. M ; Heydarinasab, A ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Since compactness is a disadvantageous characteristic of chitosan-based membranes, two different methods were used to increase the porosity of the chitosan/poly(vinyl alcohol)/polyethyleneimine (CS/PVA/PEI) membrane, and its effect on copper ion adsorption was studied. In the first method, selective dissolution of poly(vinyl pyrrolidone) (PVP) induced porosity and for the second method, a mixed solvent system, which consists of a volatile solvent (acetone), was used to improve the porosity of the membrane. Different percentages of PVP showed inadequate performance, but acetone improved the operation efficiency of adsorption. The membranes were characterized by the analysis of FT-IR, SEM,...
From as-cast to heat treated X-40 superalloy: Effect of cooling rate after partial solution treatment on microstructural evolutions and mechanical properties
, Article Materials Science and Engineering A ; Volume 808 , 2021 ; 09215093 (ISSN) ; Kolagar, A. M ; Pouranvari, M ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
This research study aims at investigating the influence of partial solution treatment and the subsequent cooling strategy on the microstructure and mechanical properties of an as-cast Co–Cr–W superalloy. Three different cooling scenarios were employed to explore the effect of cooling rate on the carbide reprecipitation potential from the solid solution formed during the heat treatment. The partial dissolution/breakdown of the continuous network of the Cr-rich M7C3 carbides during the partial solution treatment cycle along with their transformation to M23C6 carbides and formation of secondary carbides during the cooling stage were taken into account to discuss the obtained hardness values,...
Interaction between refractory crucible materials and the melted NiTi shape-memory alloy
, Article Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science ; Volume 36, Issue 3 , 2005 , Pages 395-403 ; 10735615 (ISSN) ; Badakhshan Raz, S ; Sharif University of Technology
Minerals, Metals and Materials Society
2005
Abstract
Attempts have been made to quantify the amount of contaminants absorbed by liquid metal from commercial ZrO2-, Al2O3-, and SiC-base crucibles used for vacuum melting of Ni-45 wt pet Ti alloy. The molten alloy was held under vacuum for 90 minutes at 1450°C to become homogenized. Reactions between the liquid metal and the crucible were investigated by visual observation, chemical analysis, scanning electron microscopy (SEM) image processing, and X-ray mapping. The relative degree of contamination declined in the following sequence: commercially pure SiC > SiC-5 wt pct Al2O3-5 wt pet SiO2] > slurry cast alumina > recrystallized alumina > zircon type A > oxygen deficient high-purity zirconia....
Improvement of polymer flooding using in-situ releasing of smart nano-scale coated polymer particles in porous media
, Article Energy Exploration and Exploitation ; Volume 30, Issue 6 , 2012 , Pages 915-940 ; 01445987 (ISSN) ; Ramazani, S. A. A ; Sadeghnejad, S ; Sharif University of Technology
2012
Abstract
The main purpose of this paper is modeling and simulation of in-situ releasing of smart nano-sized core-shell particles at the water-oil interface during polymer flooding. During the polymer flooding process, when these nano-particles reach the water-oil interface, migrate to the oil phase and the hydrophobic layer of them dissolves in this phase. After dissolution of this protective nano-sized layer, the hydrophilic core containing a water-soluble ultra high molecular weight polymer diffuses back into the water phase and with dissolving in this phase, dramatically increases viscosity of flooding water in the neighborhood of the water-oil interface. In this study, two different...
AC impedance and cyclic voltammetry studies on PbS semiconducting film prepared by electrodeposition
, Article Journal of Electroanalytical Chemistry ; Volume 661, Issue 1 , 2011 , Pages 265-269 ; 15726657 (ISSN) ; Jafarian, M ; Danaee, I ; Gobal, F ; Mahjani, M. G ; Sharif University of Technology
Abstract
Semiconducting lead sulfide film was deposited on Stainless Steel (SS) electrode by cyclic voltammetry (CV) at room temperature. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry were used to investigate the electrochemical properties of PbS film in Na2SO4 solution. The voltammetric results showed that oxidative dissolution of PbS film occurred at about 0.21 V vs. Ag/AgCl and total film detachment from the surface occurs with increasing potential. It is concluded that the electrode surface was not passivated by sulfur produced from oxidative dissolution of PbS film. Also, cathodic reduction of the film continued to beyond the hydrogen evolution at -1.35 V vs. Ag/AgCl....
Pore Network Modelling of Matrix Acidizing of Carbonate Rocks
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Saeed (Supervisor) ; Masihi, Mohsen (Supervisor)
Abstract
Reactive flow through porous media is a phenomenon of high importance in various study subjects i.e. groundwater, mining, geology, and petroleum reservoirs. In petroleum engineering, a related topic to this phenomenon is the dissolution of the rock matrix due to acidizing. Near_wellbore carbonate rock acidizing has been used for decades in the petroleum industry to enhance the productivity of the well. Optimal injection rate is a key question in such operations. Various models have been used to simulate reactive flow in porous media many of which are continuum-scale that face significant uncertainty regarding the pore-scale nature of the flow, mass transfer, reaction, and subsequent changes...
Microstructural evolution in damaged IN738LC alloy during various steps of rejuvenation heat treatments
, Article Journal of Alloys and Compounds ; Volume 512, Issue 1 , January , 2012 , Pages 340-350 ; 09258388 (ISSN) ; Nategh, S ; Ekrami, A. A ; Sharif University of Technology
2012
Abstract
IN738LC is one of the superior nickel base superalloys utilized at high temperatures in aggressive environments. However, experiencing high temperatures and stresses during service causes microstructure deterioration and degradation of mechanical properties in this alloy. To restore the microstructure and mechanical properties of the degraded alloy, rejuvenation heat treatments can be considered. In this study, the evolution of microstructural features in a creep damaged IN738LC superalloy during different stages of rejuvenation heat treatment cycles was investigated. During solution treatment stage, dissolution of coarsened γ′ precipitates, grain boundary films and transition zone around...
Static recrystallization behavior of AEREX350 superalloy
, Article Materials Science and Engineering A ; Volume 527, Issue 27-28 , October , 2010 , Pages 7313-7317 ; 09215093 (ISSN) ; Asgari, S ; Sharif University of Technology
2010
Abstract
The recrystallization behavior of a commercial nickel-cobalt base superalloy, AEREX 350, is investigated by means of hardness test, X-ray diffraction, and microscopy. It is found that the alloy resists recrystallization up to a high temperature of 1025 °C. Recrystallized grains are readily formed at grain boundaries below this temperature; however, the growth of these new grains is inhibited by Widmanstätten η particles having coherent facets with the nickel matrix (γ). The passage of the recrystallization front results in coherency loss and consequently dissolution of the η platelets. Recrystallization proceeds with a discontinuous precipitation of the η phase behind the moving boundary
The effect of temperature and impeller speed on mechanically Induced Gas Flotation (IGF) performance in separation of Oil from oilfield-produced water
, Article Petroleum Science and Technology ; Volume 28, Issue 14 , 2010 , Pages 1415-1426 ; 10916466 (ISSN) ; Borghei, S. M ; Nadim, F ; Roayaei, E ; Sharif University of Technology
2010
Abstract
The effect of temperature and impeller speed on the performance of induced gas flotation (IGF) systems for the removal of oil from produced water in different ranges (5-300 g/L) of total dissolved solids (TDS) was investigated in a pilot plant study. Furthermore, it was evaluated whether the IGF pilot plant effluent could reach the 15 mg/L outlet oil content as required by Article VI of the Kuwait Convention for Persian Gulf region, before being discharged to the sea. The results showed that oil removal efficiencies up to 90% could be reached at high temperature (80°C) in just one single flotation cell without adding any chemicals. Flotation unit, however, should be followed by at least one...
Aging behavior of a 2024 Al alloy-SiCp composite
, Article Materials and Design ; Volume 31, Issue 5 , May , 2010 , Pages 2368-2374 ; 02641275 (ISSN) ; Seyed Reihani, S.M ; Sharif University of Technology
2010
Abstract
In the present research work the 2024 aluminum alloy was reinforced with SiC particles via powder metallurgy method. The effect of heat treatment conditions on artificial aging kinetics was investigated. The solution treatment of the composite sample and the unreinforced alloy was carried out at 495 °C for 1, 2 and 3 h followed by aging at 191 °C for various aging times between 1 and 10 h. The existence of SiC particles led to increasing the peak hardness of the alloy. The peak hardness of the composite sample took place at shorter times than that of the unreinforced alloy for the samples solution treated for 2 and 3 h, but took place at longer times for the samples solution treated for 1 h....
Nanostructured silver fibers: Facile synthesis based on natural cellulose and application to graphite composite electrode for oxygen reduction
, Article International Journal of Hydrogen Energy ; Volume 35, Issue 8 , 2010 , Pages 3258-3262 ; 03603199 (ISSN) ; Tajabadi, F ; Taghavinia, N ; Sharif University of Technology
Abstract
The development of cheaper electrocatalysts for fuel cells is an important research area. This work proposes a new, simpler and low-cost approach to develop nanostructured silver electrocatalysts by using natural cellulose as a template. Silver was deposited by reduction of Ag complexes on the surface of cellulose fibers, followed by heat removal of the template to create self-standing nanostructured silver fibers (NSSFs). X-Ray diffraction (XRD) showed fcc silver phase and X-Ray photoelectron spectroscopy (XPS) demonstrated that the surface was partially oxidized. The morphology of the fibers consisted of 50 nm nanoparticles as the building blocks, and they possessed a specific surface area...
Pd doped WO3 films prepared by sol-gel process for hydrogen sensing
, Article International Journal of Hydrogen Energy ; Volume 35, Issue 2 , 2010 , Pages 854-860 ; 03603199 (ISSN) ; Iraji zad, A ; Rahimi, F ; Ghasempour, R ; Sharif University of Technology
Abstract
The sol gel method was employed to prepare peroxopolytungstic acid (P-PTA). Palladium chloride salt was dissolved in the sol with different Pd:W molar ratios and coated on Al2O3 substrates by spin coating method. XRD and XPS techniques were used to analyze the crystal structure and chemical composition of the films before and after heat treatment at 500 °C. We observed that Pd can modify the growth kinetic of tungsten trioxide nanoparticles by reducing the crystallite size and as a result can improve hydrogen sensitivity. Resistance-sensing measurements indicated sensitivity of about 2.5 × 104 at room temperature in hydrogen concentration of 0.1% in air. Considering all sensing parameters,...