A PRS model for accurate prediction of the optimal solid oxide cathode structure for the preparation of metals in molten chlorides

A theoretical model correlating the precursor porosity, P (in volume percentage), the metal-to-oxide molar volume ratio, R, and the cathode volume shrinkage S (in volume fraction, experimentally determined) (the PRS model) with the deoxidation speed of the solid metal oxide cathode in molten chlorides has been developed, allowing accurate prediction of the optimal cathode porosity by a simple equation, P-opt = 3R+S-1/3R x 100%. Tests of this equation in practices suggest P-opt to be an intrinsic parameter to the oxide. For example, the predicted values of P-opt for the electrolysis of TiO2 and Ta2O5 cathodes are about 67% and 25% respectively, and a cathode porosity far away from P-opt would suppress the deoxidation seriously. The established model has been well verified by the electrolysis of the oxides of Si, Ti and Ta. (C) 2012 Elsevier B.V. All rights reserved.