Effect of initial compositions on boron carbide synthesis and corresponding growth mechanism

ABSTRACT

The yield of boron carbide (B₄C) synthesised by carbothermal reduction (CTR) is low (40–50%) owing to the inappropriate initial composition. In this paper, thermodynamic equilibrium simulations for effects of initial compositions on B₄C synthesis were performed, while initial compositions on the quality and yield of B₄C synthesised by CTR from B₂O₃-C mixture at atmospheric pressure were systemically investigated. The reaction mechanisms for B₄C synthesis process were thermodynamically analysed. Moreover, growth mechanisms for B₄C particles were speculated based on the thermodynamic and experimental results. The results show that the simulations agree well with experimental results, and optimal initial composition is 1.906 (B₂O₃/C weight ratio). Under optimal condition, B₄C powder prepared at 1973?K is high-quality with well crystallinity, purity of 93.58% and yield of 90.05%. Additionally, the prepared B₄C particles show two types of morphologies, aggregate of small equiaxed particles and needle-like particle, which are formed through different reaction mechanisms, respectively.