Synthesis and densification of nano-crystalline hafnium carbide powder

Ultra-fine hafnium carbide powder was synthesized by the carbothermal reduction of HfO2 at 1600 °C using the modified spark plasma sintering (SPS) apparatus. The synthesized powder had a fine particle size of about 125 nm and a low oxygen content of below 0.5 wt%. The purity of the powder was >99.9% excluding Zr, and 99.6% when including Zr impurity. The intermediate reactions and particle growth were minimized due to the low synthesis temperature, fast heating/cooling rate and the effect of current during the modified SPS process. A relatively large amount of HfC powder could be synthesized by the new synthesis method (>175 g/day). HfC ceramics with high relative density (>96%) were obtained after sintering the synthesized powder without sintering additives at 2300 °C for 30 min under 100 MPa pressure by SPS. The average grain size of the obtained specimen was about 6 μm.