Preparation of titanium by electrochemical reduction of titanium dioxide powder in molten SrCl2–KCl

• SrCl2-based molten salt system was used to electrochemical reduction of TiO2 powder via OS process.
• The reduction mechanism and reaction pathway of the oxide powder were explored.
• No apparent growth of the oxide particles’ size during electrolysis process.
• Micro-sized metallic titanium powder with high purity was produced.

SrCl2-based molten salt system, i.e. SrCl2–KCl, was selected to enhance the electrochemical reduction of TiO2 powder via OS process, utilizing both high solubility of SrO and Sr in SrCl2 melt and extremely high oxygen affinity of active metal (Sr). In this study, titanium dioxide particles were reduced in a three-electrode cell consisting of a sinking Mo cathode in molten SrCl2–KCl, and the reduction mechanism and reaction pathway of the oxide powder were explored by using cyclic voltammetry and potentiostatic electrolysis methods. Electrochemical tests showed that with small addition of SrO in the melt TiO2 firstly transformed to SrTiO3, then reduced to Ti–O solid solution and finally converted to metallic titanium; electro-deoxidization of TiO2 powder initiated only at the early stage of electrolysis and electro-metallothermic reduction mechanism dominated the deoxidization reaction pathway. Metallic titanium powder containing 0.58 wt% oxygen with average particle size around 1 μm was produced in the 80 wt% SrCl2-20 wt% KCl bath at 800 °C with 1 wt% SrO added to the melt.