Reaction Pathway of the CaO- and CaCl2-Assisted Aluminothermic Reduction of TiO2 for the Precise Fabrication of Ti2O

The detailed reaction pathway for the aluminothermic reduction of TiO 2 has remained elusive due to its characteristically ultra-fast, combustion-like nature. This study systematically elucidates the reaction pathway of the CaO- and CaCl 2 -assisted aluminothermic reduction of TiO 2 for the precise fabrication of Ti 2 O, employing TG-DSC, high-temperature in-situ XRD, and SEM-EDS. The process involves multiple titanium-bearing intermediates, such as Ti 2 O 3 , TiO, CaTiO 3 , CaTi 2 O 4 , and TiAl 3 . The transient formation of TiAl 3 during the initial rapid-reaction stage deviates from the thermodynamically predicted pathway, attributed to localized over-reduction caused by non-uniform Al distribution and intense exothermic heat. The overall process evolves through three distinct temperature-dependent stages (< 660 °C, 660 °C to 772 °C, > 772 °C). The synergistic roles of CaO and CaCl 2 are essential. CaO acts as a thermodynamic coupling agent to enhance the driving force, while CaCl 2 serves as a kinetic accelerator to facilitate mass transfer, collectively enabling the precise fabrication of Ti 2 O.