The activity coefficient of CoO in SiO 2 -saturated MnO-SiO 2 slag was measured using metal-slag-gas equilibrium experiments under controlled oxygen potentials (10 −12 to 10 −10 atm) at 1623 K. The solubility of CoO in the slag increased with increasing oxygen potential and cobalt content in the alloy. The activity coefficient of cobalt oxide, γ CoO , referred to solid CoO, can be described as: γ CoO = 1.65 − 0.14 (wt pct CoO), where (wt pct CoO) represents the mass percent of CoO in the slag.
The conventional carbothermal reduction method for preparing titanium carbide (TiC) from titanium dioxide (TiO 2 ) suffers from high reaction temperature and long processing time, necessitating development of novel reduction processes to reduce energy consumption and improve efficiency. This study utilizing a composite reducing agent of C+H 2 for reducing TiO 2 enables the efficient synthesis of titanium carbide, combining the advantages of both carbon and hydrogen. Herein, we systematically compare titanium carbide synthesis in TiO 2 -C and TiO 2 -C-H₂ systems to elucidate the mechanism of hydrogen enhancement. Thermodynamic calculations compare the preparation processes of titanium carbide in two different systems and reveal the dual role of hydrogen: participation in the reduction reaction and lowering of the oxygen potential. Experimental results demonstrate that the introduction of hydrogen not only significantly increases the carburizing rate from 36.09% to 92.46%, promoting the formation of TiC x O 1-x as the dominant phase, but also doubles the CO content in the exhaust gas compared to the hydrogen-free system. Integrated theoretical-experimental analysis reveals the triple role of hydrogen in accelerating the TiO 2 →TiC x O 1-x transformation through: (1) synergistic reduction with both C and CO, (2) effective lowering oxygen potential of the system, which enhances the thermodynamic driving force to accelerate both the TiO 2 →Ti 2 O 3 reduction and subsequent carbide formation, and (3) increased pore volume generation within the titanium oxide matrix due to the superior diffusivity and reducing capability of hydrogen, thereby facilitating enhanced gas diffusion pathways. This study provides fundamental mechanistic insights into the hydrogen-enhanced carbothermal reduction process for efficient TiC synthesis from TiO₂.
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