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    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)
    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... 

    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
    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... 

    The investigation of the kinetics and mechanism of hydrogen evolution reaction on tin

    , Article International Journal of Hydrogen Energy ; Volume 32, Issue 12 , 2007 , Pages 1755-1761 ; 03603199 (ISSN) Azizi, O ; Jafarian, M ; Gobal, F ; Heli, H ; Mahjani, M. G ; Sharif University of Technology
    The mechanism and kinetics of the hydrogen evolution reaction (HER) on tin electrode in 0.1 M H2SO4 solution were studied using the methods of steady-state polarization and electrochemical impedance spectroscopy. The simulation of the data obtained from these two methods, using nonlinear fitting procedure allowed us to determine the rate constants of Volmer, Heyrovsky and Tafel steps associated with the mentioned reaction. The kinetic results indicate that HER mechanism at low negative potentials is a serial combination of Volmer step and parallel Tafel and Heyrovsky steps. At high negative potentials where the hydrogen coverage reaches its limiting value, a Tafel line with the slope of -... 

    Investigation of Pb/PbS a positive Schottky junction formed on conductive glass in contact with alkaline solution

    , Article Journal of Applied Physics ; Vol. 116, issue. 3 , July , 2014 ; ISSN: 00218979 Heidaripour, A ; Jafarian, M ; Gobal, F ; Mahjani, M. G ; Miandari, S ; Sharif University of Technology
    PbS on Pb thin film (Pb/PbS) was deposited on conductive glass (CG) substrate (CG/Pb/PbS) using electrochemical techniques to investigate the Schottky junction in solution. The CG/Pb/PbS electrode was investigated by different techniques based on thermionic emission theory. Electrochemical cell consisted of the CG/Pb/PbS as a working electrode in an alkaline solution showed character of the Schottky junction. Reduction and oxidation of H2O on the CG/Pb/PbS electrode were enhanced under illumination. Water photo splitting is the main process. Study of linear sweep voltammetry at around open circuit potential (OCP) allowed proposing a model based on the Schottky junction which is charged at... 

    Fabrication of self-organised highly ordered titanium oxide nanotube arrays by anodic oxidation and characterisation

    , Article International Journal of Nanomanufacturing ; Volume 5, Issue 3-4 , 2010 , Pages 297-309 ; 17469392 (ISSN) Mohammadpour, R ; Ahadian, M. M ; Iraji Zad, A ; Taghavinia, N ; Dolati, A. G ; Sharif University of Technology
    Self-organised and vertically oriented titanium oxide nanotube array (TNTA) has been synthesised by potentiostat anodisation of Ti foil in fluoride-based electrolyte. By varying the anodisation voltage from 8 V to 24 V it was possible to gradually change the topologies of nanotubes. The size of TNTAs was measured using SEM images and also determined based on a non-destructive optical method. In addition, photoelectrochemical properties of nanotubular TiO2/Ti electrodes were examined by anodic photocurrent response, potentiodynamic polarisation measurements and electrochemical impedance spectroscopy. A general equivalent circuit model was proposed for photoelectrochemical system consists of... 

    On the pseudocapacitive behavior of nanostructured molybdenum oxide

    , Article Journal of Solid State Electrochemistry ; Volume 14, Issue 4 , 2010 , Pages 643-650 ; 14328488 (ISSN) Farsi, H ; Gobal, F ; Raissi, H ; Moghiminia, S ; Sharif University of Technology
    Nanostructured molybdenum oxide was potentiodynamically deposited onto a stainless steel surface from an aqueous bath by cycling the potential between 0 and -0.75 V vs. Ag/AgCl. The deposit consisted of particulates in the range of 30 to 80 nm. Electrochemical studies under galvanostatic charge/discharge and also impedance spectroscopy revealed capacitive behavior in the potential range of -0.3 to -0.55 V vs. Ag/AgCl with the value of 477 F g-1 at 0.1 mA/cm2. An equivalent circuit comprising of three parallel branches consisting of double-layer capacitance, Warburg impedance, and a constant phase element signifying pseudo-capacitance each coupled with their corresponding resistances was... 

    Reproducible electrochemical analysis of nanostructured Cu2O using a non-aqueous 3-methoxypropionitrile-based electrolyte

    , Article Electrochemistry Communications ; Volume 86 , 2018 , Pages 1-5 ; 13882481 (ISSN) Shooshtari, L ; Iraji zad, A ; Mohammadpour, R ; Sharif University of Technology
    Elsevier Inc  2018
    Cu2O is an attractive material in terms of semiconducting properties and is considered a leading candidate in all-oxide photovoltaics. Electrochemical analysis of Cu2O, including Mott-Schottky (MS) and impedance spectroscopy (IS), provides a wealth of data on charge carriers, Fermi level and interface properties. MS and IS are usually measured in aqueous solutions. However, Cu2O is easily reduced or oxidized to Cu or CuO in aqueous solutions, the layer peels off after the analysis and there is a small voltage window for the tests. In some cases, an anti-corrosive n-type barrier layer is employed on top of the bare Cu2O electrode to make the measurement possible, which could result in... 

    Kinetics and electrocatalytic behavior of nanocrystalline CoNiFe alloy in hydrogen evolution reaction

    , Article International Journal of Hydrogen Energy ; Volume 32, Issue 12 , 2007 , Pages 1686-1693 ; 03603199 (ISSN) Jafarian, M ; Azizi, O ; Gobal, F ; Mahjani, M. G ; Sharif University of Technology
    Electrocatalytic activity of electrodeposited nanocrystalline CoNiFe alloy in hydrogen evolution reaction (HER) was studied in 1 M NaOH solution. The steady-state polarization measurement and electrochemical impedance spectroscopy were used to determine the Tafel slope, the exchange current density and the activation energy. The simulation of the data obtained from these two methods, using a nonlinear fitting procedure, allowed us to determine the surface coverage and the rate constants associated with the mentioned reaction. The ac-impedance spectra measured at various overpotentials in the HER region exhibited three semicircles in the complex plane plots. The high-frequency semicircle was... 

    Impedance spectroscopy study of aluminum electrocrystallization from basic molten salt (AlCl3-NaCl-KCl)

    , Article Electrochimica Acta ; Volume 52, Issue 17 , 2007 , Pages 5437-5443 ; 00134686 (ISSN) Jafarian, M ; Gobal, F ; Danaee, I ; Mahjani, M. G ; Sharif University of Technology
    Aluminum electrocrystallization is studied by means of electrochemical impedance spectroscopy (EIS). A model based on random birth and deterministic growth of monolayers is proposed, in which the edges are assumed to follow a propagation law. The high frequency impedance data show charge transfer reaction of AlCl4- reduction while the low frequency features signifies the growth mode of deposits. The inductive response observed in the course of polycrystalline deposition reflects the activation of electrode area while a capacitive loop appears in regular growth. Parameters of impedance model in this system can be calculated from the fitting of experimental data to the Faradaic impedance... 

    A study of hydrated nanostructured tungsten trioxide as an electroactive material for pseudocapacitors

    , Article Ionics ; Volume 19, Issue 2 , May , 2013 , Pages 287-294 ; 09477047 (ISSN) Farsi, H ; Gobal, F ; Barzgari, Z ; Sharif University of Technology
    Agglomerates of tungsten trioxide in the range of 90 nm to 1 μm are prepared by the acid precipitation method and characterized by XRD as well as scanning electron microscopy. The product when coated with platinum showed pseudocapacitance when in contact with acidic electrolyte in the potential range of 0. 1 to -0. 25 V/SCE. Capacitance in the range of 0. 014 to 0. 039 F cm-2 exhibiting moderate potential dependencies measured through both chronopotentiometry and impedance spectroscopy is presumed to be due to the insertion/de-insertion of protons into the lattice of tungsten trioxide. Equivalent circuit consisting of parallel simulators of mass transfer and capacitor charging... 

    The influence of pulse plating parameters on the electrocodeposition of Ni-TiO2 nanocomposite single layer and multilayer structures on copper substrates

    , Article Surface and Coatings Technology ; Volume 262 , 2015 , Pages 173-183 ; 02578972 (ISSN) Mohajeri, S ; Dolati, A ; Ghorbani, M ; Sharif University of Technology
    Elsevier  2015
    The electrocodeposition of Ni-TiO2 nanocomposite single layers and Ni-TiO2/TiO2 multilayers from a Watts bath containing a TiO2 sol on copper substrates was investigated by different deposition techniques. Compared with direct current (DC) deposition, both pulse plating (PP) and pulse reverse plating (PRP) facilitated higher incorporations of TiO2 nanoparticles. Morphological studies conducted by scanning electron microscopy and field emission scanning electron microscopy revealed that the microstructure of the Ni-TiO2 nanocomposite coatings are affected both by pulse potentials and durations, indicating that higher incorporations of TiO2 nanoparticles refine the microstructure. The results... 

    Effects of zirconia content on characteristics and corrosion behavior of hydroxyapatite/ZrO2 biocomposite coatings codeposited by electrodeposition

    , Article Surface and Coatings Technology ; Volume 262 , January , 2015 , Pages 166-172 ; 02578972 (ISSN) Shojaee, P ; Afshar, A ; Sharif University of Technology
    Elsevier  2015
    HAp and HAp/ZrO2 composite coatings were successfully electrodepesited on 316L stainless steel substrates in the solutions containing ZrO2 particles at different concentrations. The effects of ZrO2 content on characteristics of the coatings were investigated using X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM) and bonding strength test. Polarization and electrochemical impedance spectroscopy measurements were carried out in order to evaluate corrosion behavior of the coatings. In-vitro test in SBF and further SEM observations were performed to examine bioactivity of the coatings. HAp/ZrO2 composite coatings showed better... 

    Development of a nanocellulose composite based voltammetric sensor for vitamin B9 analysis

    , Article Current Nanoscience ; Volume 12, Issue 4 , 2016 , Pages 493-499 ; 15734137 (ISSN) Ghalkhani, M ; Shahrokhian, S ; Sharif University of Technology
    Bentham Science Publishers B.V 
    As a B group vitamins, vitamin B9 is a Water-soluble vitamin which is produced by plants and microorganisms (bacteria and yeasts). Vitamin B9 plays an important role in the production of proteins and nucleic acids in body and also is one of the substances that prevents the development of neural tube defects in the fetus. Methods: Electrochemical behavior of vitamin B9 was studied using a potentiostat/galvanostat SAMA 500, electroanalyzer system, I. R. Iran. A three-electrode system was used, including a glassy carbon working electrode (d = 2.0 mm, purchased from Azar Electrode Co., Urmia, I.R. Iran), an Ag/AgCl (saturated KCl) reference electrode and a Pt wire auxiliary electrode.... 

    Effects of Fe2O3 content on ionic conductivity of Li2O-TiO2-P2O5 glasses and glass-ceramics

    , Article Materials Chemistry and Physics ; Volume 190 , 2017 , Pages 8-16 ; 02540584 (ISSN) Mohaghegh, E ; Nemati, A ; Eftekhari Yekta, B ; Banijamali, S ; Sharif University of Technology
    Elsevier Ltd  2017
    In this study, Li2O-TiO2-P2O5-x(Fe2O3) (x = 0, 2.5, 5 and 7.5 weight part) glass and glass-ceramics were synthesized through conventional melt-quenching method and subsequently heat treatment. Glass samples were studied by UV–visible spectroscopy and crystallized samples were characterized by differential thermal analysis, X-ray diffractometry and field emission scanning electron microscopy. Besides, electrical properties were examined according to the electrochemical impedance spectroscopy techniques. Experimental optical spectra of the Fe2O3-doped glasses revealed strong UV absorption band in the range of 330–370 nm, which were attributed to the presence of Fe3+ ions. The major crystalline... 

    Plastic injection molding dies using hybrid additively manufactured 420/CX stainless steels: electrochemical considerations

    , Article npj Materials Degradation ; Volume 6, Issue 1 , 2022 ; 23972106 (ISSN) Shahriari, A ; Samei, J ; Sanjari, M ; Jahanbakht, M ; Amirkhiz, B. S ; Mohammadi, M ; Sharif University of Technology
    Nature Publishing Group  2022
    This research focused on the corrosion resistance and microstructure of hybrid additively manufactured (HAM) samples of AISI 420/CX (420/CX SS) stainless steels. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott–Schottky analyses as well as the electrochemical noise (EN) technique were used to evaluate the electrochemical behavior of the as-built and heat-treated HAM parts in NaCl solution. The results showed a more protective passive layer formed on the CX SS side. The distribution of Cr-rich M23C6 carbides in matrix of 420 SS side resulted in a lower corrosion resistance compared to the CX SS side. The noise data analysis confirmed an increase in the... 

    Epoxy nanocomposite coating based on calcium zinc phosphate with dual active/barrier corrosion mitigation properties

    , Article Progress in Organic Coatings ; Volume 163 , 2022 ; 03009440 (ISSN) Alibakhshi, E ; Haddadi, S. A ; Motlagh, A. L ; Ghaderi, M ; Ramezanzadeh, B ; Mahdavian, M ; Arjmand, M ; Jalili, M ; Sharif University of Technology
    Elsevier B.V  2022
    In this paper, a high-performance epoxy nanocomposite with dual active/barrier protection ability based on calcium zinc phosphate (CZP) nanopigment was fabricated. Then chemistry, morphology, and anti-corrosion ability of the commercial zinc phosphate (ZP) and CZP pigments were studied. By electrochemical techniques, the inhibition potency of the CZP nanopigment was examined in a NaCl solution on mild steel (MS) substance and compared with that of ZP. Results revealed a higher corrosion inhibition degree of the CZP compared to the ZP. The growth of a protective layer on the metal coupons exposed to the CZP extract was illustrated by X-ray photoelectron spectroscopy (XPS), field emission... 

    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)
    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... 

    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)
    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... 

    Preparation and Characterization of a Lithium Ion Conducting Electrolyte

    , M.Sc. Thesis Sharif University of Technology Toofan, Samin (Author) ; Nemati, Ali (Supervisor)
    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... 

    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)
    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...