Thermodynamic research of the reaction mechanism for TiB₂ synthesized by carbothermal reduction

The reaction mechanism of TiB₂ synthesized by carbothermal reduction is unclear due to a lack of thermodynamic research. In this work, the phase diagrams of TiO₂-B₂O₃-C system were analyzed at a large temperature range (900–1800 °C), illustrating that Ti₄O₇, Ti₃O₅, and TiC were the main intermediate products. According to the Gibbs free energy minimum principle, the synthesis pathways of the main intermediate products and the target product TiB₂ were discussed, respectively. Based on the thermodynamic research, the reaction mechanism of TiO₂-B₂O₃-C system was proposed and verified by experimental research at 900–1500 °C. X-ray-pure TiB₂ powder was synthesized at 1500 °C for 30 min and the possible reaction mechanism could be divided into three stages: TiO₂(anatase)→TiO₂(rutile)→Ti₃O₅, TiC →TiB₂.