Fabrication and properties of HfB₂ ceramics based on micron and submicron HfB₂ powders synthesized via carbo/borothermal reduction of HfO₂ with B₄C and carbon

Abstract The two batches of commercially available powders were used as raw materials to synthesize HfB₂ powders. The synthesized HfB₂ powders were heated at 450 C for 10 min in the flow of nitrogen and then quenched into liquid nitrogen. The results indicated the refinement effect of liquid nitrogen quenching on synthesized HfB₂ powders was very obvious. The relative density values of HfB₂ ceramics fabricated using micron and submicron HfB₂ powders were less than 89.5% due to the presence of trace carbonaceous compound and more than 98.1% due to higher driving force for densification, respectively. The microstructure, mechanical properties and thermal shock resistance of HfB₂ ceramics fabricated using micron and submicron HfB₂ powders were investigated in detail. In particular, finite element analysis was used to explore the temperature and thermal stress distribution in the specimen in the course of thermal shock.