Thermo–electrochemical synergistic reduction of TiO2 to metallic titanium in fluoride molten salts regulated by CaO

This study explores a CaO-regulated thermal–electrochemical synergistic reduction approach for TiO 2 in fluoride-based molten salts, aiming to enhance deoxygenation efficiency and particle densification. At elevated temperatures, CaO reacts with TiO 2 and the NaF–K 2 TiF 6 molten salt to form CaF 2 and reactive intermediate phases, which facilitate the in situ generation of metallic Ca and alter the local redox environment. These transformations promote the complete electrochemical reduction of TiO 2 into metallic titanium through the formation and subsequent reduction of titanium oxyfluoride complexes such as K 2 NaTiOF 5 and TiOF 2 . Cyclic voltammetry reveals that CaO addition induces a negative shift in the Ti(IV)/Ti(III) redox potential, suggesting a modified reduction pathway and increased activation energy. The titanium powders synthesized at 890 °C with current densities ranging from 2.0 to 3.5 A/cm 2 exhibit reduced oxygen content down to 2900 ppm and a dense, near-spherical morphology. Microstructural analyses using FIB–SEM and EDS confirm that CaO incorporation suppresses surface oxidation and promotes particle uniformity. These findings provide mechanistic insight into the synergistic role of CaO in titanium deoxygenation and demonstrate its potential in reducing the oxygen content of titanium powders and improving their compositional uniformity.