The Influence of Fluoride Anion on the Equilibrium between Titanium Ions and Electrodeposition of Titanium in Molten Fluoride-Chloride Salt

摘要

NaCl-KCl-TiCLt was prepared via using titanium sponge to reduce titanium tetrachloride in a NaCl-KCl melt under a negative pressure at 1023 K. The relationship between titanium valence states and [F]/[Ti] molar ratios was investigated with successive adding potassium fluoride in the pre-prepared NaCl-KCl~TiCl_x. It was found that the average valence of titanium ions tended to be stable around 3.0 when [F]/[Ti] molar ratio was greater than 1.80. The equilibrium redox potentials, E_(Ti~3)+/Ti~(2+), E_(Ti~(4+)/Ti~(3+)), E_(Ti~(3+)/Ti and E_(Ti~(2+)/Ti), were also calculated through the obtained concentration of equilibrium titanium ions with different molar ratios of [F]/[Ti]. Meanwhile, the influence of the fluoride anion on over-potential and characteristics of titanium electrodeposition were investigated through changing the molar ratio of [F]/[Ti]. The results showed that, with the increasing of [F]/[Ti] molar ratios, the grain size of electrodeposition products became smaller, while the over-potential was higher.