Electrochemical reduction of tungsten (VI) oxide from a eutectic melt CaCl2-NaCl under potentiostatic conditions

Abstract

The paper presents results of the study of the electrochemical reduction of tungsten(VI) oxide in a melt of the eutectic composition 52 mol% CaCl2 and 48 mol% NaCl at a liquid gallium electrode. Scanning electron microscopy and X-ray diffraction methods were used to study the microstructures of the obtained powders. The Rietveld method which is based on diffraction patterns were used to calculate the quantitative content of phases in WO3 reduction products. The thermodynamic properties of the electrolysis process were investigated by voltammetry. It is shown that a necessary condition for the electrochemical reduction of WO3 is electrolysis at potentials higher than the standard electrode potential of decomposition of calcium tungstate, which is formed by the interaction of tungsten oxide with calcium chloride. The reduction can take place by both electrochemical and metallothermic mechanisms depending on the conditions of electrolysis. The reduction product is fine tungsten with a particle crystallite size of up to 1 ?m.