The mechanism and kinetics of producing single-crystal powders of titanium carbide via a hydride-calcium method

The mechanism and kinetics of the reduction-carbidization of titanium oxide by calcium hydride and carbide (hydride-calcium method) are studied. This process provides the production of single-crystal powdered titanium carbide. Theoretical analysis and experimental methods is found that the mechanism of the formation of TiC forms is staged and includes two sequential reactions: TiO₂ + 2CaH₂ = Ti + 2CaO + 2H₂↑ and Ti + C = TiC. It is revealed that the formation of titanium carbide proceeds in a calcium melt by the dissolution of titanium and graphite in it with the subsequent crystallization of the TiC particles from the melt. It is noted that the kinetics of the process in the range t = 900?1200°C depends on the temperature and time of isothermal holding. At t > 1100 °C, its abrupt activization is observed. This is due to an increase in the amount of melt based on calcium and the enhancement of the solubility of titanium and carbon in it, which leads to the acceleration of reactions of reduction of titanium oxide to titanium and to the synthesis of titanium carbide. The optimum technological parameters of the process (temperature, time of isothermal holding, and conditions of the calculation of the charge) are determined. It is shown that titanium carbide obtained by this technology is homogeneous and has the content close to stoichiometric one, specifically, TiC_1.0.