Dispersant-assisted preparation of ultra-fine HfB2 powder

Hafnium boride (HfB2), as an ultra-high temperature ceramic, has been extensively employed in the aerospace field due to its high melting point and excellent ultrahigh-temperature oxidation resistance. Despite its outstanding performance, the development of the HfB2 for practical applications remained limited by its low-quality production including high oxygen content, large particle size and high agglomeration. In this work, a series of dispersants are adopted for reducing the particle size and suppressing the agglomeration of HfB2 powder during the liquid phase co-precipitation method combined with carbothermal reduction. Based on various characterizations, it is discovered that the presence of dispersants can greatly reduce the particle size and restrain the agglomeration of the HfB2. Specifically, the HfB2 prepared using polyethylene glycol (PEG) demonstrates an ultra-fine particle size down to hundreds of nanometers. To better understand the function of the dispersant, the formation of the HfB2 is unveiled via a combination of multiple characterizations. In detail, the dispersants can cap on the formed HfB2 and restrict their further growth and agglomeration during the reaction through the electrostatic repulsion and steric hindrance of high molecular polymer, thereby greatly improving the quality of HfB2 powder.