Effect of B ₄ C particle size on TiB ₂ synthesis via microwave‐assisted boro/carbothermal reduction

Abstract Understanding the reaction behavior of B ₄ C feedstocks with varying particle sizes is crucial for the synthesis of fine high‐purity TiB ₂ via microwave‐assisted boro/carbothermal reduction in the TiO ₂ ‒B ₄ C‒C system. The influence of three particle sizes of B ₄ C, that is, 15.8, 2.8, and 0.6 µm on the microstructure, particle size, and purity of synthesized TiB ₂ was investigated. It was found that the morphology and size of TiB ₂ product synthesized with coarse (15.8 µm) and medium (2.8 µm) B ₄ C were independent of the feedstock size. Whereas the resultant TiB ₂ size (0.56 µm) closely matched the initial fine B ₄ C size (0.6 µm). The reduction of B ₄ C particle size significantly enhanced TiB ₂ purity, lowering residual C and O impurities from 0.42% and 1.24% (with 15.8 µm B ₄ C) to 0.23% and 0.48% (with 0.6 µm B ₄ C), respectively. Furthermore, thermodynamic analysis and differential scanning calorimetry revealed distinct reaction pathways: coarse B ₄ C resulted in incomplete contact between TiO ₂ and B ₄ C raw materials led to the formation of TiBO ₃ and Ti ₂ O ₃ intermediates, whereas fine B ₄ C facilitated direct TiB ₂ formation without intermediates. Based on the thermodynamic evaluation and experimental results, the reaction mechanism for synthesis of TiB ₂ from coarse‐ and fine‐grained B ₄ C was also systematically explored and established, respectively.