Thermodynamic investigation and reaction mechanism of B ₄ C synthesis based on carbothermal reduction

Abstract The reaction mechanism of B ₄ C synthesis as yet remains unclear due to the lack of sufficient thermodynamic investigation, which limits the large‐scale controllable production of B ₄ C ceramic material. In this paper, thermodynamic investigation of B ₄ C synthesized by carbothermal reduction was calculated at atmospheric pressure over a wide temperature range (1500‐2500 K) coupled with the effects of pressure on B ₄ C synthesis. Besides, predominance diagrams for B–C–O system at different temperatures and pressures were further established. Upon thermodynamic results, reaction mechanism was proposed and then verified by the synthesis experiment of B ₄ C at desired temperatures. The thermodynamic investigation indicates that B ₄ C may be synthesized by the reactions of C with liquid B ₂ O ₃ (LS mechanism) or gaseous B ₂ O ₂ (VS mechanism). At low temperature (~1823 K), B ₄ C is polyhedral shape via LS mechanism, while two‐dimensional flake‐like B ₄ C is synthesized by VS mechanism at high temperature (2123 K~). The obtained two types of B ₄ C verify the accuracy of thermodynamic results. This study is instructive for the optimization of temperature, pressure for large‐scale controllable production of B ₄ C ceramic material.