Investigation of the Calciothermic Reduction of TiO<sub>2</sub> for the Green Production of Ti and TiH<sub>2</sub> Powders

Abstract

To develop an eco-friendly titanium (Ti) production process, the calciothermic reduction of titanium dioxide (TiO<sub>2</sub>) was investigated. The mechanism involved in the reduction of TiO<sub>2</sub> using calcium (Ca) was examined. The influence of a molten salt, calcium chloride (CaCl<sub>2</sub>), on the calciothermic reduction was investigated by conducting experiments at 1123 – 1223 K in an argon (Ar) atmosphere for the duration of 0.5 – 9 h. When CaCl<sub>2</sub> was used as a molten salt, the oxygen (O) concentration in Ti decreased to 0.162 mass% owing to the removal of calcium oxide (CaO) from the surface of the Ti particles. In addition, the use of a CaCl<sub>2</sub> – lithium chloride (LiCl) molten salt decreased the reaction temperature to 1073 K and the O concentration in the obtained Ti reached 0.333 mass%. Furthermore, after the calciothermic reduction of TiO<sub>2</sub> at 1173 K using a perforated crucible, the residual Ca-containing salt was sufficiently separated in-situ from the crucible, and a mixture of Ti and TiH<sub>1.924</sub> was produced via hydrogenation at 1023 K by changing the atmosphere gas from Ar to hydrogen gas (H<sub>2</sub>). The results of this study demonstrate the feasibility of the calciothermic reduction of TiO<sub>2</sub> for the eco-friendly production of Ti and TiH<sub>2</sub> powders.