A CHEMICAL AND ELECTROCHEMICAL STUDY OF TITANIUM IONS IN THE MOLTEN EQUIMOLAR CACL2-DEGREES-C(NACL MIXTURE AT 550)

The chemical and electrochemical properties of solutions of titanium c hlorides in the fused CaCl2 + NaCl equimolar mixture were studied at 5 50 degrees C using different working electrodes. We determined the sta bility range of the various oxidation states of titanium and calculate d the standard potentials of the Ti(III)/Ti(II) and Ti(II)/Ti(0) redox couples, the solubility products of the titanium oxides, the kinetic parameters of the electrochemical systems at the different electrodes and the diffusion coefficients of the electroactive species. We have a lso studied the titanium electrodeposition process by potential step m easurements which indicated instantaneous nucleation of titanium at tu ngsten substrates. All these data allowed us to build-up the potential -pO(2-) diagram which summarizes the properties of Ti-O compounds in t he melt studied and can be used (together with the E-pO(2-) diagram of chlorinating gaseous mixtures) to predict operating conditions for th e process of industrial production of metallic titanium from molten sa lt systems. (C) 1997 Elsevier Science S.A. All rights reserved.