Low-temperature synthesis and sinterability of high-purity submicron TiB₂ powder via microwave-assisted carbothermal reduction

Microwave-assisted carbothermal reduction has been innovatively developed for the low-temperature synthesis of high-purity submicron TiB₂ powders. The thermodynamic research of TiO₂-B₄C-C system and relevant reactions showed that suitable excess addition of B₄C was required to compensate for the boron source evaporation loss. The effect of excess addition of B₄C (0 −15 wt%) and synthesis temperature (1350 −1550 °C) on the phase composition, purity, and morphology of the products have been investigated. Submicron TiB₂ powders (0.75 µm) with high-purity (0.36% residual C and 0.53% O) were successfully synthesized at 1450 °C for 20 min under microwave assistance with TiO₂, excess 5 wt% B₄C, and carbon black. Additionally, the as-synthesized TiB₂ powders after spark plasma sintering at 2000 °C for 15 min showed a relatively higher sinterability, namely increased at 7.7% relative density of sintered ceramic when compared with the commercially available powders owing to the lower O content and submicron-scale size.