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Total 177 records

    Electrochemical Hydrogen Generation Using Metal Organic Frameworks Derived Catalysts

    , M.Sc. Thesis Sharif University of Technology Koohdareh, Amir Reza (Author) ; Gholami, Mohamad Reza (Supervisor)
    Abstract
    In recent years, the widespread investigation on multi-transition metal oxides that with two or more transition metal oxides, have been increased rapidly for electrochemical application due to low cost, high conductivity and good electrochemical performance other than single metal oxides. In this project, CuCo2O4 nanoparticles were firstly fabricated by decomposing of CuCo-MOF as the template. The as prepared samples were used to synthesis a new nanocomposite of MoS2 and CuCo2O4. The best ratio of the two component were optimized to prepare the best electrocatalyst for Hydrogen evolution reaction (HER). The structure of prepared nanocomposite were investigated by various techniques such as... 

    Design of Doped TiO2 Dye-sensitized Solar Cells with Different Arrangement Modes of Photoanode Electrodes

    , M.Sc. Thesis Sharif University of Technology Vafaei, Maral (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    In this thesis, pure –known as T- and chromium doped titanium dioxide nanoparticles –known as -CTx- with different dopant atomic ratio (0.1 to 5 %at.) were synthesized using a facile, fast and efficient method. FESEM and XRD studies showed no morphologic and structural change via Cr doping of nanoparticles (size in the range of 20-30 nm). However, according to DRS analysis, Cr intrusion in TiO2 crystal structure, drastically reduced band gap energy of pure TiO2 from 3.14 eV to 1.81 eV for CT3 powder and improved absorption range of UV-Vis spectrum. Mott-Schottky plots indicated that, Cr doping, caused reduction in donor density of TiO2 and an upward shift in the conduction band edge.... 

    Probing the Performance of Safflower Plant as a Green Inhibitor with Molybdenum Disulfide on Corrosion Protection Properties of the Epoxy Coating

    , M.Sc. Thesis Sharif University of Technology Nematian, Bahram (Author) ; Ramazani Saadat Abadi, Ahmad (Supervisor) ; Mahdavian Ahadi, Mohammad (Supervisor)
    Abstract
    Today, the process of corrosion and compensation of minor injuries, without the need for tracing or any other physical interference, has become one of the subjects of interest to researchers. Inhibitors have been considered as one of the anti-corrosion agents. In this research, safflower extract as a green inhibitor in sodium chloride corrosive environment was used to evaluate the rate of corrosion of mild steel. Also the MoS2 nanoparticles were used as carrier of this green inhibitore in the epoxy coating to allow the activation of the coating in a scratched state in sodium chloride solution of 3.5%. In the first step, the extract of the safflower was prepared to reach the best part of this... 

    Synthesis, Characterization and Investigation of Electrocatalytic Activity of Nanoparticle/Cerium Oxide Composites in Oxygen Evolution and Reduction Reactions

    , M.Sc. Thesis Sharif University of Technology Moravvej, Heydar (Author) ; Taherinia, Davood (Supervisor)
    Abstract
    The sluggish kinetics of oxygen evolution and reduction on the surface of electrodes is a major problem for the widespread use of devices that are based on sustainable, renewable and clean technologies, such as fuel cells and metal–air batteries. Therefore, the development of efficient and cost–effective materials for the oxygen evolution (OER: Oxygen Evolution Reaction) and reduction reactions (ORR: Oxygen Reduction Reaction) is highly desirable. In recent years, Metal–organic frameworks (MOFs) and their derivatives, have drawn considerable attention as potential catalysts and electrocatalyst due to their high surface area and porous structure. In this study, cerium (IV) oxide was... 

    Synthesis, Characterization and Investigation of Electrocatalytic Activity of Nanoparticle/Cerium Oxide Composites in Oxygen Evolution and Reduction Reactions

    , M.Sc. Thesis Sharif University of Technology Moravvej, Heydar (Author) ; Taherinia, Davood (Supervisor)
    Abstract
    The sluggish kinetics of oxygen evolution and reduction on the surface of electrodes is a major problem for the widespread use of devices that are based on sustainable, renewable and clean technologies, such as fuel cells and metal–air batteries. Therefore, the development of efficient and cost–effective materials for the oxygen evolution (OER: Oxygen Evolution Reaction) and reduction reactions (ORR: Oxygen Reduction Reaction) is highly desirable. In recent years, Metal–organic frameworks (MOFs) and their derivatives, have drawn considerable attention as potential catalysts and electrocatalyst due to their high surface area and porous structure. In this study, cerium (IV) oxide was... 

    Synthesis and Characterization of Supercapacitor Electrodes Based on Graphene and MnO2 Nanostructure

    , M.Sc. Thesis Sharif University of Technology Mardi, Saeed (Author) ; Moshfegh, Alireza (Supervisor) ; Moradlou, Omran (Co-Advisor)
    Abstract
    Supercapacitors represent a new class of energy storage devices that have been attracted many researchers in last few years. Graphene with unique properties such as superior electrical conductivity and large specific surface area is one of the most suitable materials in supercapacitor applications. Besides, metal oxides are being used as active compounds in supercapacitors due to their role in redox reactions. In this research, synthesis and characterization of supercapacitor electrodes based on graphene and MnO2 nanostructured materials was studied under different conditions. For this purpose, Graphene oxide (GO) was synthesized by Hummers’ method and then, it was deposited on a nickel foam... 

    Investigation of Crystallization Behavior and Electrical Properties of Glass-Ceramics in the Li2O-TiO2-P2O5 System

    , M.Sc. Thesis Sharif University of Technology Mohaghegh, Elnaz (Author) ; Nemati, Ali (Supervisor) ; Eftekhari Yekta, Bijan (Supervisor) ; Banijamali, Sara (Co-Advisor)
    Abstract
    During the past two decades, much attention has been paid to rechargeable lithium batteries, because they have high energy density. Glass-ceramics is a category of this material, which may be of great potential as solid electrolytes.. The object of this thesis is preparation of Li2O-TiO2-P2O5 glass, glass-ceramic and investigation their electrical behavior. Prepared Samples were investigated by Differential thermal analysis (DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV-Visible spectroscopy and Electrochemical impedance spectroscopy (EIS). In this study LiTi2(PO4)3 crystals were crystallized in a glass with the composition 45Li2O-25TiO2-30P2O5 (molar ratio). According... 

    Preparation and Characterization of a Lithium Ion Conducting Electrolyte

    , M.Sc. Thesis Sharif University of Technology Toofan, Samin (Author) ; Nemati, Ali (Supervisor)
    Abstract
    In recent years lithium-air batteries captured worldwide attention because of their high energy density. Solid state electrolytes is one of the main components of lithium-air batteries. Lithium almunium titanium phosphate(LATP) is a nasicon type ion conduction which may be of great potential as solid electrolyte. The object of this thesis was the preparation of LATP solid electrolyte which can be used in a lithium-air battery. To reach this goal LATP powder was synthesized using a solution-based method and an appropriate crystallization temperature was selected based on obtained results of X-ray diffraction analysis. In the next step solid electrolytes was prepared under different pressing... 

    Theoretical Determination of the Impedance Response of Some General Multi Step Electrode Processes

    , M.Sc. Thesis Sharif University of Technology Rash Seyedabadi, Hazhar (Author) ; Gobal, Fereydoon (Supervisor)
    Abstract
    Impedance measurement is one of the most efficient electrochemical methods to investigate the mechanism and kinetics of electrode reactions. This method can detect the steps of successive or parallel electron and mass transfer chemical reactions based on measuring the response time constant. The method of showing results, commonly known as Nyquist diagram,which is based on drawing real and imaginary components of the impedance, with respect to each other in different measurement frequencies, is very useful for determining the mechanism of electrode reactions and the kinetic measurements. The main objective of this thesis is totheoretically determine the impedance response of six... 

    Synthesis of Carbon Nanostructure-Metal Nanoparticles Composites and Investigate their Application as a Modifier in Electrochemical Mesurments

    , Ph.D. Dissertation Sharif University of Technology Hosseininassab, Niloufar (Author) ; Shahrokhian, Saeed (Supervisor)
    Abstract
    In the first part, metallic nanoparticles were synthesized on the different carbon nanostructers platform such as nanodiamond and graphene sheet using electrochemical and chemical methods. The prepared composite film were characterized by electron microscopy, spectroscopy and electrochemical techniques. The synthesized nanocomposite were applied as a modifier in order to prepare electrochemical sensors for determination trace amount of important pharmaceutical and biological compounds.In the first work, Nanodiamond-graphite (NDG) decorated with Ag nanoparticles (AgNPs-NDG) was synthesized with chemical method. The surface morphology and the nature of the composite were investigated. The... 

    Investigation of Electrocatalytic Activity of Metal-based Nanocomposites in the Reaction of Carbon Dioxide Reduction

    , M.Sc. Thesis Sharif University of Technology Hatami, Homayoun (Author) ; Bastani, Darioush (Supervisor) ; Taherinia, Davood (Supervisor)
    Abstract
    Emissions of carbon dioxide (CO2) from fossil fuels are a potential issue for the global climate. One way to meet this challenge is to electrochemically convert CO2 molecules to reduced carbon species such as formates, alcohols, hydrocarbons, etc., which is a difficult process due to the poor kinetics of CO2 reduction. Therefore, the use of catalysts, while preventing undesirable side reactions, can also play an important role in reducing CO2. In this study, a two-step synthesis of CuS (1, 5, 12, 24 hr) @ Cu-MOF has been reported as an advanced electrocatalyst for CO2 reduction in neutral pH environments. Bismuth has been used to improve the electrocatalytic properties of the samples. Bi-CuS... 

    Study of Microstructural Changes Associated with Internal Resistance of a Li-ion Battery

    , M.Sc. Thesis Sharif University of Technology Tabean, Saba (Author) ; Asgari, Sirous (Supervisor)
    Abstract
    As one of the main features of Li-Ion batteries, internal resistance severely affects performance and characteristics of these batteries e.g. output power and working voltage. In this study, we tried to understand role of internal resistance on microstructure development and provide a correlative relation between microstructural features and performance of lithium-ion batteries. To catch this target, four types of Li-Ion battery chose, varying cathode type. These batteries were exposed to both normal and severe cycling conditions. Regarding to the key role of current rate on the performance of Li-ion batteries, an extensive research on different types of batteries at various current rates... 

    Electrochemical and Photocatalytic Behaviour of V&S Doped Titania Produced with Plasma Electrolytic Oxidation

    , M.Sc. Thesis Sharif University of Technology Ahmadzadeh, Mohammad (Author) ; Ghorbani, Mohammad (Supervisor)
    Abstract
    Plasma Electrolytic Oxidation is a new and promising method for synthesis of oxide layers and coatings on light metals such as titanium and aluminum. This method is a fast, easy and economicalway to produce TiO2 layers on Ti substrate. Photocatalytic properties of TiO2 can be improved with doping of other elements such as metals and non-metals by expanding its band gap which is in UV area of light spectrum in to visible area.Photocatalytic properties of TiO2 is also dependent on surface area and grain size, oxide layers which has been produced with PEO process has a high surface area due to its porosity. Voltage, electrolyte and additives concentration are among parameters which can affect... 

    Probing the Electrochemical Properties of Gold Electrode Modified with Edge-Functionalized Graphene and its Application

    , M.Sc. Thesis Sharif University of Technology Aghajani, Talin (Author) ; Shahrokhian, Saeed (Supervisor)
    Abstract
    In the present work, edge-functionalaized graphene was used as electrode material and its electrochemical properties were systematically characterized by electrochemical impedance spectroscopy and cyclic voltammetry. Two methods were applied to modify the gold electrode surface. First method was the self assembling process of graphene nanosheets on gold electrode surface. Second method was simply casting specific amounts of graphene suspension on the gold electrode surface. Nyquist plots show decrease of the charge transfer resistance on the electrode surface at both cases. In cyclic voltammetry studies, first electrode shows no significant changes while the second electrode exhibits... 

    Controlled engineering of WS2 nanosheets-CdS nanoparticle heterojunction with enhanced photoelectrochemical activity

    , Article Solar Energy Materials and Solar Cells ; Volume 141 , 2015 , Pages 260-269 ; 09270248 (ISSN) Zirak, M ; Zhao, M ; Moradlou, O ; Samadi, M ; Sarikhani, N ; Wang, Q ; Zhang, H. L ; Moshfegh, A. Z ; Sharif University of Technology
    Elsevier  2015
    Abstract
    Abstract We report the well-controlled preparation of WS2 nanosheets-CdS nanoparticle heterojunction for photoelectrochemical (PEC) water splitting application. The WS2 nanosheets with an average thickness of ~5 nm and lateral dimensions of ~200 nm were synthesized via liquid phase exfoliation of bulk WS2 in water/ethanol solution, followed by deposition onto ITO substrate via electrophoretic method. CdS nanoparticles were grown via facile successive ion layer absorption and reaction (SILAR) method. Using these two well-controlled methods, CdS/WS2/ITO and WS2/CdS/ITO systems were fabricated. The loading of WS2 nanosheets was... 

    Synthesis and elucidation of electrochemical characteristics of nanorods, microsized and nanosized CuO as cathode materials for Zn/CuO alkaline battery

    , Article Journal of Solid State Electrochemistry ; Volume 19, Issue 7 , April , 2015 , Pages 2155-2165 ; 14328488 (ISSN) Zeraatkish, Y ; Jafarian, M ; Gobal, F ; Mahjani, M. G ; Sharif University of Technology
    Springer New York LLC  2015
    Abstract
    Discharge characteristics of nanorods (NRs), microsized and nanosized copper (II) oxide (CuO) particles prepared via thermal decomposition and thermal oxidation routes are examined as cathode materials of a Zn/CuO cell without membrane separators. The electrochemical discharge is examined galvanostatically at a current density of 500 mAg−1 and reveals that the first discharge cycles of all the CuO materials contain one potential plateau; subsequent discharge cycles involve three potential plateaus. Each potential plateau is due to an electrochemical reaction. The first, second, and third potential plateaus are attributed to Cu2O3, CuO, and Cu2O discharges,... 

    Formation of Zn-Ca-Ni tri cation's phosphate coating on steel and study that properties

    , Article TMS 2009 - 138th Annual Meeting and Exhibition, San Francisco, CA, 15 February 2009 through 19 February 2009 ; Volume 1 , 2009 , Pages 615-623 ; 9780873397384 (ISBN) Zarei, M ; Afshar, A ; Sharif University of Technology
    2009
    Abstract
    A new Zinc phosphating bath, which produces coatings at relatively lower temperatures within a reasonable time by using of chemical accelerators has been devised. Improvement of the bath performance by the addition of divalent cations like calcium, nickel has been studied. Bath formulation and operating conditions have been optimized by coating weight determinations. Stable samples of phosphating formulations with and without calcium and nickel salts were prepared and the structure and morphology of the phosphate coatings were determined by using X-ray diffraction (XRD) techniques, scanning electron microscopy. ASTMB117 salt spray test and electrochemical impedance spectroscopy (EIS) were... 

    Impact of chromium doping on physical, optical, electronic and photovoltaic properties of nanoparticle TiO2 photoanodes in dye-sensitized solar cells

    , Article New Journal of Chemistry ; Volume 41, Issue 23 , 2017 , Pages 14516-14527 ; 11440546 (ISSN) Vafaei, M ; Mohammadi, M. R ; Sharif University of Technology
    Royal Society of Chemistry  2017
    Abstract
    Herein, we report the impact of chromium doping on the physical properties, electronic band structure and photovoltaic characteristics of their corresponding devices based on dye-sensitized solar cells (DSCs). Different DSCs with various compositions of the photoanode electrodes are fabricated to study their optical, structural, conduction band edge, donor density, depth of trap states and photoelectrochemical properties using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), Mott-Schottky capacitance analysis, chemical capacitance and electrochemical impedance spectroscopy (EIS) measurements. For such studies, the Cr-doped... 

    Impedance analysis of growth and morphology of electropolymerized polypyrrole nanocomposites [electronic resource]

    , Article Journal of New Materials for Electrochemical Systems ; 2014, Volume 17, Number 2 Torabi, M. (Morteza) ; Sadrnezhaad, S. K ; Sharif University of Technology
    Abstract
    Pure polypyrrole (PPy), PPy/Al2O3 and PPy/SiO2 nanocomposites synthesized galvanostatically using different polymerization charges. Electrochemical impedance measurements of pure polypyrrole revealed that the film thickness affected the impedance responses. The characteristic frequencies vs. film thickness that obtained using Cole-Cole plots showed that electrodeposition mechanism changed from 3D to 1D after nuclei overlapping for pure PPy. Analysis of the nanocomposites impedance spectrums revealed no changes during the film growth, i.e. deposition continues 3D even after nuclei overlapping. Scanning electron microscopy (SEM) confirmed the impedance results and showed that the morphology of... 

    PH-responsive nanostructured polyaniline capsules for self-healing corrosion protection: the influence of capsule concentration

    , Article Scientia Iranica ; Volume 24, Issue 6 , 2017 , Pages 3512-3520 ; 10263098 (ISSN) Tavandashti, N. P ; Ghorbani, M ; Shojaei, A ; Mol, J. M. C ; Terryn, H ; Gonzalez Garcia, Y ; Sharif University of Technology
    Abstract
    Nanostructured hollow polyaniline (PANI) capsules are good candidates for encapsulation of corrosion inhibitors and pH-responsive release when incorporated into organic coatings. In previous studies, the corrosion protection performance of PANI capsules, containing organic inhibitor 2-Mercaptobenzothiazole (MBT), was demonstrated. The present work studies the influence of capsule concentrations (i.e., 0.3, 1, and 2 wt%) on the corrosion protection properties of the coating system. Anti-corrosion properties of different coatings were compared by means of Electrochemical Impedance Spectroscopy (EIS) and Scanning Vibrating Electrode Technique (SVET). MBT loaded PANI capsules in epoxy ester...