Browsing by Author "Shipochka M."

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    STRUCTURE AND CATALYTIC ABILITY OF Sn-Co POWDERS TO OXYGEN REDUCTION REACTION IN A MODEL METAL-AIR BATTERY
    (2022-01-01) Ignatova K.; Popov I.; Shipochka M.
    Composition, microstructure, current efficiency and catalytic ability of Sn-Co powders, deposited by constant and pulse potential modes are investigated. SEM, EDS, XPS, XRD and BET methods were applied. It is shown that at higher potentials in stationary mode and at higher pulse frequencies in pulse mode (500-1000 Hz), Sn-Co powders with maximum specific surface area (21 - 23 m2 g-1) and cobalt content (56 wt. % in stationary and 75.5 wt. % in pulse mode) are obtained. XRD and XPS analysis showed that the powders obtained in both modes represent a mixture of amorphous and microcrystalline phases of tetragonal β-Sn, α-Co with hexagonal, hcp lattice, as well as phases of CoO, SnO2 and impurity phase of SnF2 only in stationary mode. It was found that the catalytic ability of Sn-Co powders to the oxygen reduction reaction, ORR in a model Metal-Air battery is better than that of the reference Ag catalyst at low current densities. It increases with an increase in the cobalt content and with an increase in the dispersity of the powders
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    XPS characterization of TiO2 layers deposited on quartz plates
    (2008-03-01) Stefanov P.; Shipochka M.; Stefchev P.; Raicheva Z.; Lazarova V.; Spassov L.
    TiO2 layers for gas sensing applications were obtained by Liquid Phase Deposition (LPD). The layers were deposited on gold-coated piezoelectric quartz crystals. The surface structure, morphology and chemical properties were analysed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). SEM showed that the layers were porous and composed of uniform crystalline grains. XPS indicated them to be non-stoichiometric. © 2008 IOP Publishing Ltd.