Synthesis of submicrometer HfB2 powder and its densification

This work reported submicrometric HfB2powder synthesis by a new borothermal reduction route using HfO2 and boron as raw materials. The particle size of HfB2 powders by conventional borothermal reduction was ~ 2.1 μm. HfB2 particle coarsening mainly depended on the presence of B2O3 product. To obtain HfB2 powders with small particle size, new borothermal reduction route was developed. This route included the borothermal reduction of HfO2 with boron at 1100 °C, washing by hot water, and the removal of residual B2O3 at 1550 °C, namely, two-step reduction plus intermediate water-washing. Based on the new route, the particle size of HfB2 powders decreased to ~ 0.8 μm. Finally, the hot-pressing densification of the synthesized powders was studied.

► HfB2 powder coarsening depended on by-product B2O3 during borothermal reduction.
► Using conventional borothermal reduction, the particle size of HfB2 powders was ~ 2.1 μm.
► A new borothermal reduction route for fine powders was developed.
► By the new route, the particle size decreased to ~ 0.8 μm.
► Dense HfB2 ceramics was achieved using self-synthesized powders.