Preparation and Characterization of Tungsten Powder by Molten Salt Electrolysis in the Eutectic NaCl-CaCl₂-Na₂WO₄ System

Tungsten powder was prepared in NaCl-CaCl₂-Na₂WO₄ system by molten salt electrolysis method,chemical reactions occurred in electrolysis process,and electrolytic products were analyzed by means of X-ray diffraction (XRD),scanning electron microscopy (SEM),energy spectrum analyzer (EDS) and differential thermal analyzer (DTA).The anodic process and overvoltage were investigated using cyclic voltammetry and residual electromotive force method.The results show that tungsten powder could be synthesized under the conditions of a temperature of 800 ℃,a cell voltage of 2.5 V with graphite electrode,calcium tungstate is active substance in electrolysis process.The anodic reactions are irreversible and the kinetic obstruction of anodic process should be controlled by the anodic chemical polarization.