Ultrafine hafnium diboride (HfB2) powders
Ultrafine hafnium diboride (HfB2) powders were synthesized by the boro/carborthermal reduction process. Fine-scale mixing of the reactants was achieved by solution-based processing using hafnium oxychloride (HfOCl2·8H2O) and phenolic resin as the precursor of HfO2 and carbon respectively. The heat treatment was completed at a temperature range 1300–1500°C for 1h using spark plasma sintering (SPS) apparatus. The crystallite sizes of the synthesized powders were small (<500 nm) and the oxygen content was low (0.85 wt%). The grain growth of HfB2 could be effectively suppressed using SPS due to the fast heating rate. The effects of temperature and holding time on the synthesis of ultrafine HfB2 powders were discussed.