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electrolytes
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Effect of Plasma Electrolytic Oxidation on Joining aa 5052-carbon Fiber Aluminium Alloy to Polyprolene in Silicate and Aluminium Electrolyte
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
The purpose of this study is to increase the strength of metal and polymer compound combinations in the direction of this increase, the electrolytic plasma oxidation coating is applied and its effect will be checked to increase bond strength. Also, due to the failure in the polymeric side of the bonding, the effect of adding short fibers of carbon to polypropylene will be checked on the strength of the polymer and bond strength. The effect of current density at coating application, the presence or absence of short carbon fiber in the polymeric field and the formation of initial hole on aluminum alloy on bond strength was studied. For further analysis, the optical and electron microscopic...
Modeling and Simulation of Water Distribution in the Various Layers of Polymer Fuel Cell
, M.Sc. Thesis Sharif University of Technology ; Baghalha, Morteza (Supervisor) ; Khorashe, Farhad (Supervisor)
Abstract
Fossil fuel are energy resources in decline. In recent years, fuel cell have become as a source of energy to replace conventional systems .Among the various types of fuel cells, PEMFCs (proton exchange membrane fuel cells) possess a series of highly advantageous features such as a low-operating temperature, sustained operation at high-current density, low weight, compactness, potential for low cost and volume, long stack life, fast start-ups and suitability for discontinuous operation. Water management is one of the most critical and challenging problems. There is a delicate balance between the membrane hydration and avoiding cathode from flooding. Cathode flooding occurs when the water...
The Investigation of Effective Parameters in Coating on Aluminized Steel by Plasma Electrolytic Oxidation Process
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
Plasma electrolytic oxidation process (PEO) is now recognized as a relatively new method in surface engineering. In this process, formation of micro arcs resulted from electric discharges on the surface of the specimen in the appropriate electrolyte, is used to ionize the gas layer which has enshrouded the specimen. In the present study, ceramic coating on aluminized steel was produced by PEO process and the effects of the influential parameters were comprehensively investigated. For this purpose, coating on the aluminized steel with dimension of 25×30 mm² was produced under different condition of processing time from 1 to 15 minutes, current density from 10 to 20 A/dm², frequency from 50 to...
Prediction of Thermodynamic Parameters in Solutions with Similar Composition to Plasma or Blood
, Ph.D. Dissertation Sharif University of Technology ; Abdekhodaie, Mohammad Jafar (Supervisor) ; Ghotbi, Cyrus (Co-Advisor)
Abstract
Serum osmolality is an important physiological quantity that is directly related to health condition of human body. Glucose, urea, and NaCl are the main components which determine the value of serum osmolality. Besides, calcium and potassium are vital inorganic cations for the body. Thus, it is of high importance to investigate the interactions between these physiological solutes in aqueous solution. Thermodynamic quantities like osmotic and activity coefficients contain enthalpic and entropic information and thus are a direct measure of interactions in these complex systems. Thus, theoretical and experimental methods were applied to investigate these thermodynamic parameters in multi-solute...
Gel-Electrolyte Based Dye-Sensitized Solar Cell Employing Mesoporous Tio2 Beads
, M.Sc. Thesis Sharif University of Technology ; Askarim, Masoud (Supervisor) ; Mohammadi, Mohammad Reza (Co-Supervisor)
Abstract
Nowadays, dye-sensitized solar cells (DSSCs) are highly regarded as a cheap alternative for conventional silicon-based solar cells. Improvements of their efficiency and performance sustainability are two major challenges of their commercialization. Engineering of the photoanode electrode by controlling its thickness, chemical composition, and morphology was proposed as effective method in increasing the light conversion efficiency of the cells. In the present study, mesoporous TiO2 beads with different arrangements including pristine mesoporous beads, mixtures of mesoporous beads with nanoparticles, and in the form of two-layer structure of nanoparticles (as an active layer) and mesoporous...
Formation of Plasma Electrolytic Oxidation Coating on Mg-Ti Coupl Joint with Friction stir Welding Process and Evaluation its Properties
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
Plasma electrolytic oxidation is the novel surface engineering technology that used as the low cost and eco-friendly method for improvement of corrosion resistance and wear resistance of Mg and Ti alloys. The aim of this investigation is firstly joint the Ti and Mg, then optimization of coating process condition of Ti-Mg couple for achieve the best corrosion and wear resistance of coating. For this purpose, initially Ti and Mg were joint together by friction stir welding treatment and then the effect of coating variable such as type of electrolyte, coating voltage, coating time and the concentration of the bath constitute, on the coating properties were investigated, and then the effect of...
Synthesis of Composite Coating with HA Nanoparticles on Ti by AC Plasma Electrolyte Oxidation
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
In this project, a ceramic biocompatible coating was applied on Titanium which is included Hydroxyapatite by AC Plasma Electrolyte Oxidation method. First, coating was performed in 5 different solutions and various duration in 500mA/Cm2 as a current density. Then, by microscopic and macroscopic images and size of porosity and also thickness of coat, 3 solutions were chosen for adding nanoparticles: Solution 1 which includes NaH2PO4 and Ca(CH3COO)2 , Solution 3 which includes Ca(CH3COO)2 and Na-Beta G and Solution 4 which includes Ca(H2PO4)2, HMP, NA2(EDTA) and Ca(CH3COO)2 . Also the time 10 minutes was chose as a appropriate time. The average of the porosities size in solution 1 was about...
Preparation of Composite Coating with ZrO2 Nanoparticles on Aluminum 5052 Alloy Using Plasma Electrolytic Oxidation
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
Plasma Electrolytic Oxidation (PEO) method was used for the preparation of ceramic coatings on Aluminum 5052 substrate in a silicate-based electrolyte containing different concentrations of ZrO2 nanoparticles. Before the addition of nanoparticles into the electrolyte, determining process parameters including current density, coating time, and frequency were examined carefully. After studying corrosion behavior, thickness, and coating morphology in different circumstances, the frequency of 50Hz, the current density of 150mA/cm2, and the coating time of 20 minutes were chosen as the optimum parameters. After that and with the usage of those parameters, ZrO2 nanoparticles were added to the...
Electrochemical Desulfurization of Sample Oil
, Ph.D. Dissertation Sharif University of Technology ; Farhadi, Fatolla (Supervisor) ; Shahrokhi, Mohammad (Co-Supervisor)
Abstract
Since, presence of sulfur compounds in fuels leads to environmental pollution and deacrese of fuel quality, fuel desulfurization should be considered for enhancing the fuel charachteristics. Electrochemical desulfurization was recogonized as one of desulfurization techniques that uses anode and cathode in an electrolytic environment under mild temperature and pressure. In this research, electrochemical desulfurization of crude gas-oil has been studied over electrodes of copper and stainless steel in the presence of NaOH and sulfuric acid. In this research, the effects of operational prameters like stirring rate, temperature, applied potential, sodium hydroxide/sulfuric acid addition as...
An electrochemical study of Au-Ni alloy electrodeposition from cyanide-citrate electrolytes
, Article Journal of Electroanalytical Chemistry ; Volume 577, Issue 1 , 2005 , Pages 1-8 ; 15726657 (ISSN) ; Ghorbani, M ; Ahmadi, M. R ; Sharif University of Technology
Elsevier
2005
Abstract
Cyclic voltammetry, j-t transients and transient time measurements have been used to characterize the Au-Ni alloy deposition and to obtain the nucleation and growth mechanism. The electrodeposition of gold, nickel and gold-nickel alloys was studied in cyanide-citrate electrolytes. The analysis of the voltammograms and j-t transients clearly shows that deposition of the Au and hence, of Au-Ni alloys, is affected by adsorbed cyanide ligands mainly at low overpotentials and a direct reduction occurs at high overpotentials. In this case, the Au deposition is kinetically favored, while the Ni deposition is controlled by the cyanide-citrate adsorbed adlayer. In an alloy electrolyte, the Au and Ni...
Microstructural investigation of hard phases in as-cast Ni-Ti memory alloy
, Article Praktische Metallographie/Practical Metallography ; Volume 42, Issue 9 , 2005 , Pages 454-469 ; 0032678X (ISSN) ; Sadrnezhaad, S. K ; Sharif University of Technology
Carl Hanser Verlag
2005
Abstract
Ti4Ni2O, Ti4Ni2N, TiC and Ti2Ni are brittle compounds usually formed during production and processing of the Ti-Ni SMA alloys. These compounds adversely affect on workability and shape memory properties of the alloy. This paper presents most recent findings related to the morphologies of various inclusions and Ti-Ni phases formed during and after vacuum induction melting and casting of Ti-45wt.% Ni material. Cast samples were mechanically and/or electrolytically polished and etched. Extensive optical and scanning electron microscopic studies were carried out to characterize the composition and microstructure of the as cast Ti-Ni alloys. Results indicated that mechanical polishing followed by...
Application of the simplex simulated annealing technique to nonlinear parameter optimization for the SAFT-VR equation of state
, Article Chemical Engineering Science ; Volume 60, Issue 23 , 2005 , Pages 6607-6621 ; 00092509 (ISSN) ; Ghotbi, C ; Galindo, A ; Sharif University of Technology
Elsevier Ltd
2005
Abstract
A non-equilibrium simplex simulated annealing algorithm is applied as a global optimization method to parameter optimization for an equation of state based on the generalized statistical associating fluid theory incorporating potentials of variable range. The parameters are determined by optimizing the calculated phase behaviour of a number of pure solvents, such as water and alcohols, and aqueous electrolyte solutions. The optimized parameters obtained via the simulated annealing algorithm are compared to those obtained using the simplex method and, for the electrolyte solutions, a gradient-based quasi-Newton method. In the case of the pure solvents, the lowest values of the objective...
A sustainable approach to replace bleed stream in electrical refining of copper
, Article Materials Letters: X ; Volume 16 , 2022 ; 25901508 (ISSN) ; Khayati, G ; Korasani, M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Despite extensive studies on electrorefining to remove impurities from copper production units, bleeding electrolytes is the most popular method for controlling impurities due to low operating costs. A controlled cooled-reheat cycle was used to remove impurities in industrial electrolytes of Khatoon Abad copper company. Phase identification and physical study were done by the XRD, SEM, TEM, and FTIR techniques. The results confirmed the possibility of the removal of 23 wt% Ni, 26 wt% Sb, 2.4 wt% As and convention of 6 wt% of As5+ to As3+ at cooled-reheat cycle. © 2022 The Author(s)
Effects of microhydrophobic porous layer on water distribution in polymer electrolyte membrane fuel cells
, Article Journal of Fuel Cell Science and Technology ; Vol. 11, Issue. 1 , 2014 ; ISSN: 1550-624X ; Roshandel, R ; Sharif University of Technology
Abstract
Performance of polymer electrolyte membrane fuel cells (PEMFC) at high current densities is limited to transport reactants and products. Furthermore, large amounts of water are generated and may be condensed due to the low temperature of the PEMFC. Development of a two-phase flow model is necessary in order to predict water flooding and its effects on the PEMFC performance. In this paper, a multiphase mixture model (M2) is used, accurately, to model two-phase transport in porous media of a PEMFC. The cathode side, which includes channel, gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL), is considered as the computational domain. A multidomain approach has been used...
Characterization of nitrocarburized surface layer on AISI 1020 steel by electrolytic plasma processing in an urea electrolyte
, Article Journal of Materials Research and Technology ; Volume 2, Issue 3 , 2013 , Pages 213-220 ; 22387854 (ISSN) ; Shariat, M.H ; Dehghan, S. A ; Solhjoo, S ; Sharif University of Technology
Elsevier Editora Ltda
2013
Abstract
In this study, electrolytic plasma processing (EPP) was employed for surface nitrocarburizing of AISI 1020 steel in a urea electrolyte, where the substrate samples were connected cathodically to a high-voltage DC current power supply. The structural, mechanical, wear and corrosion properties of the samples treated for 3-5 min were investigated. The results show that the surface layers formed on the samples by this treatment at 220 V have a ferritic nitrocarburizing characteristic which consists of a compound layer and diffusion zone. The surface layers of the treated samples at 240 V consisted of a compound layer, martensitic layer and diffusion zone, respectively, which is a marker of...
MAO-derived hydroxyapatite-TiO 2 nanostructured bio-ceramic films on titanium
, Article Materials Research Bulletin ; Volume 47, Issue 11 , 2012 , Pages 3407-3412 ; 00255408 (ISSN) ; Golestani Fard, F ; Rezaie, H. R ; Mirhosseini, S. M. M ; Ziaee, A ; Sharif University of Technology
2012
Abstract
Micro Arc Oxidation (MAO) process was utilized to fabricate nano bioceramic TiO 2-hydroxyapatite coatings on titanium substrates. Samples were produced in electrolytes contained 1 g/l β-glycerophosphate and 5, 10 and 15 g/l calcium acetate for 3, 6 and 10 min at 350 V. The techniques including XRD, XPS, SEM, FESEM and EDX were employed to study the effect of processing parameters. Hydroxyapatite, anatase, α-tri calcium phosphate and calcium titanate phases as well as 30-60 nm-size crystals were detected in the coating layer. It was also observed that the pore volume would increase by increasing the electrolyte concentration. The growth time was also found to influence the total pore volume....
A comparative study of sequentially layer-deposited and co-deposited Co-Mn oxides as potential redox capacitors
, Article Journal of Solid State Electrochemistry ; Volume 16, Issue 4 , April , 2012 , Pages 1561-1569 ; 14328488 (ISSN) ; Jafarzadeh, S ; Sharif University of Technology
2012
Abstract
Layers of cobalt and manganese oxides were co-deposited or deposited on top of each other or next to each other by potentiostatic method onto stainless steel substrate. Deposition potentials of 1 and -1 V for the anodic and cathodic depositions were employed. Specific capacitance values in the range of 38.5-78 F g -1 were found with cobalt oxide on top of manganese oxide having the lowest and manganese oxide on top of cobalt oxide having the highest capacitances. The usefulness of the electrodes was characterized by cyclic voltammetry, charge-discharge cycling, and electrochemical impedance spectroscopy in 2 M NaOH electrolyte for redox supercapacitor applications. The latter presented the...
A new structure to increase the photostability of CdTe quantum dot sensitized solar cells
, Article Journal of Physics D: Applied Physics ; Volume 44, Issue 4 , January , 2011 ; 00223727 (ISSN) ; Iraji zad, A ; Taghavinia, N ; Molaei, M ; Sharif University of Technology
2011
Abstract
In this paper a new cell structure is introduced to reduce the rate of CdTe corrosion in quantum dot sensitized solar cells (QDSSCs) using I -/I- 3 electrolyte. In this cell, one electrode is a titania nanorod that was sensitized with CdTe quantum dots as the working electrode. A thin gold layer is sputtered on the electrode to act as a protective layer against the I-/I- 3 corrosive electrolyte and to passivate the CdTe surface traps which are the main recombination centres in a QDSSC. In addition, a Schottky barrier formed at the interface of Au and CdTe prevents direct electron recombination from the CdTe conduction band with I- 3 ions. The mechanism of charge transfer and quantum dot...
Effects of alumina nanoparticles concentration on microstructure and corrosion behavior of coatings formed on titanium substrate via PEO process
, Article Ceramics International ; Volume 42, Issue 7 , May , 2016 , Pages 8789–8797 ; 02728842 (ISSN) ; Faghihi Sani, M. A ; Mohammadi, M. R ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Plasma electrolytic oxidation (PEO) process was employed to create ceramic coatings on titanium substrate by using silicate-based electrolytes containing different concentrations of alumina nanoparticles (0, 3, 6, and 10. g/lit). The effect of alumina nanoparticles concentration on the morphology, chemical and phase composition of the PEO coatings was investigated by scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer, respectively.The corrosion behavior of samples was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. SEM, EDS, and XRD analyses illustrated that alumina nanoparticles incorporated into the...
Electrolytic capacitor-less AC-DC LED driver with constant output current and PFC
, Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; 2015 , Pages 107-112 ; 9781479976539 (ISBN) ; Rezazadeh, G ; Zolghadri, M. R ; Noroozi, N ; Sharif University of Technology
Abstract
Recent developments in improving lighting efficiency and cost reduction of LED's have caused them to be a suitable alternative for the current lighting systems. In this paper a novel off-line structure is proposed to drive LED's. The proposed circuit has a high power factor and high efficiency and a long lifetime. To increase the life time of the converter, the proposed circuit doesn't use any electrolytic capacitors in the power stage. The proposed circuit consists of a transition mode (TM) Flyback converter in order to have power factor correction (PFC). A Buck converter is added to the third winding of the Flyback transformer in order to create two paths for the electrical power. DC power...