“…1,4,14 Therefore, the research on developing and optimizing direct reduction of metal oxides technology for metal preparation is essential. At present, many metal oxides, such as TiO 2 , 11,15 ZrO 2 , 16 HfO 2 , 17 Nb 2 O 5 , 18 Ta 2 O 5 , 4 Cr 2 O 3 , 19 MoO 3 , 20 and NiO, 21 etc., have been used as raw materials by this method. Meanwhile, various molten salt systems, such as LiCl, LiCl-Li 2 O, CaCl 2 , CaCl 2 -NaCl, and LiCl-KCl-CaCl 2 , have been used as the electrolytes for the electrolytic reduction process.…”