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

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.