Determination of the kinetic pathway in the electrochemical reduction of titanium dioxide in molten calcium chloride

An investigation into the kinetics of the electrochemical reduction of titanium dioxide (TiO2) to titanium metal (Ti) in molten calcium chloride has been performed. Partially reduced samples were prepared by terminating the reduction process after different reaction times and characterised by means of X-ray diffraction analysis. Based on the time-dependent changes of phase composition as well as thermodynamic and kinetic considerations, the reaction path has been derived. The key result is that the reduction proceeds through a number of individual stages some of which involve the formation and decomposition of calcium titanates. Several of the partially reduced samples were examined further through scanning electron microscopy and energy-dispersive X-ray analysis. The results demonstrate that the electrochemical reduction of titanium dioxide to titanium metal is accompanied by substantial changes in the microstructure.