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Journal of the Electrochemical Society, Vol.159, No.6, E139-E143, 2012
Production of Fine Tungsten Powder by Electrolytic Reduction of Solid CaWO4 in Molten Salt
Direct electrochemical reduction of solid CaWO4 to fine W powder in molten CaCl2-NaCl was studied by cyclic voltammetric measurement and potentiostatic/constant-voltage electrolysis. The effect of electrolysis conditions such as electrolysis time, temperature and voltage on the quality of the product (the residual amount of CaWO4) was systematically investigated. Based on the solubility tests of CaWO4 in the melt in a wide temperature range, an unprecedented strategy on electrolytic extraction of pure tungsten powder was proposed and confirmed, which involves low-temperature and short-duration electrolysis of solid CaWO4 in molten CaCl2-NaCl eutectic salt (1023 K, 10-hour electrolysis) followed by a simple washing process in the same melt at a higher temperature (1123 K, 1-hour washing). The particle size of the as-prepared W powder is less than 200 nm. This process exhibits a high yield and increased energy efficiency for production of fine W powder from CaWO4. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.113206jes] All rights reserved.