Synthesis of Ultrafine Hafnium Diboride Powders Using Solution‐Based Processing and Spark Plasma Sintering

Ultrafine hafnium diboride (HfB 2 ) powders were synthesized by the boro/carborthermal reduction process. Fine‐scale mixing of the reactants was achieved by solution‐based processing using hafnium oxychloride (Hf OC l 2 ·8H 2 O) and phenolic resin as the precursor of HfO 2 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 HfB 2 could be effectively suppressed using SPS due to the fast heating rate. The effects of temperature and holding time on the synthesis of ultrafine HfB 2 powders were discussed.