Search for: valence-state
0.005 seconds

    Synthesis of sodium tungsten oxide nano-thick plates

    , Article Materials Letters ; Volume 82 , September , 2012 , Pages 214-216 ; 0167577X (ISSN) Garavand, N. T ; Mahdavi, S. M ; Irajizad, A ; Ahadi, K ; Sharif University of Technology
    Elsevier  2012
    In this letter a simple procedure to synthesize sodium tungsten oxide nano-thick plates from WO 3 films has been reported. WO 3 films were grown by pulsed-laser deposition method and then heat treated at temperatures up to 560 °C and times up to 120 min. Slide glass was used as both substrate and sodium source simultaneously. XRD analysis revealed presence of an amorphous structure for as-deposited WO 3 films. On the other hand, XRD showed formation of a monoclinic WO 3 structure with annealing in lower temperatures and a triclinic Na 0.5WO 3.25 structure with annealing at higher temperatures. Intensity of the triclinic phase peaks enhanced drastically by rising annealing temperature and... 

    Optical properties and surface morphology of evaporated (WO 3)1-x-(Fe2O3)x thin films

    , Article Thin Solid Films ; Volume 484, Issue 1-2 , 2005 , Pages 124-131 ; 00406090 (ISSN) Moshfegh, A. Z ; Azimirad, R ; Akhavan, O ; Sharif University of Technology
    Thin films of (WO3)1 - x-(Fe2O 3)x composition were deposited by thermal evaporation on glass substrates and then all samples were annealed at 400 °C in air. Optical properties such as transmittance, reflectance, and optical bandgap energy of the "as deposited" and the annealed films were studied using ultraviolet-visible spectrophotometry. It was shown that the annealing process did not substantially change the optical transmittance and reflectance of all the films except the films having x = 0.75. By increasing Fe2O 3 content in the films from x = 0 to x = 0.75, optical bandgap energy decreased from 3.4 to about 1.3 eV and from 3.1 to 2.1 eV for the "as deposited" and the annealed samples,... 

    Effect of chemical substitution on the morphology and optical properties of Bi1-xCaxFeO3 films grown by pulsed-laser deposition

    , Article Journal of Materials Science: Materials in Electronics ; Volume 24, Issue 1 , 2013 , Pages 248-252 ; 09574522 (ISSN) Ahadi, K ; Mahdavi, S. M ; Nemati, A ; Sharif University of Technology
    The morphological characteristics as well the optical properties of Ca-doped BiFeO3 films grown by pulsed-laser deposition technique have been investigated. AFM images revealed that calcium has a radical effect on the surface features of BiFeO3 films. By utilizing spectrophotometer, transmission behaviour of the films was investigated. Local IV characteristics of the films disclosed about three orders of magnitude enhancement concerning electrical conductivity through Ca doping. X-ray photoelectron spectroscopy results revealed that Ca can reduce the valence state of iron in the compound  

    Kinetic studies of glucose electrocatalytic oxidation on GC/Ni electrode

    , Article International Journal of Chemical Kinetics ; Volume 44, Issue 11 , 2012 , Pages 712-721 ; 05388066 (ISSN) Danaee, I ; Jafarian, M ; Forouzandeh, F ; Gobal, F ; Sharif University of Technology
    Nickel-modified glassy carbon electrode (GC/Ni) prepared by galvanostatic deposition was used for the electrocatalytic oxidation of glucose in alkaline solutions where different electrochemical methods were employed. In cyclic voltammetry studies, in the presence of glucose an increase in the peak current of the oxidation of nickel hydroxide is followed by a decrease in the corresponding cathodic current. This suggests that the oxidation of glucose is being catalyzed through mediated electron transfer across the nickel hydroxide layer comprising nickel ions of various valence states. Under the chronoamperometric regime, the reaction followed a Cottrellian behavior and the diffusion... 

    Electrocatalytic oxidation of glucose on Ni and NiCu alloy modified glassy carbon electrode

    , Article Journal of Solid State Electrochemistry ; Volume 13, Issue 8 , 2009 , Pages 1171-1179 ; 14328488 (ISSN) Jafarian, M ; Forouzandeh, F ; Danaee, I ; Gobal, F ; Mahjani, M. G ; Sharif University of Technology
    Nickel and nickel-copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) prepared by galvanostatic deposition were examined for their redox processes and electro-catalytic activities towards the oxidation of glucose in alkaline solutions. The methods of cyclic voltammetry (CV) and chronoamperometry (CA) were employed. The cyclic voltammogram of NiCu alloy demonstrates the formation of β/β crystallographic forms of the nickel oxyhydroxide under prolonged repetitive potential cycling in alkaline solution. It is also observed that the overpotential for O 2 evolution increases for NiCu alloy modified electrode. In CV studies, NiCu alloy modified electrode yields significantly higher...