Carbothermal reduction synthesis of nanocrystalline zirconium carbide and hafnium carbide powders using solution-derived precursors

Zirconium carbide (ZrC) and hafnium carbide (HfC) powders were produced by the carbothermal reduction reaction of carbon and the corresponding metal oxide (ZrO2 and HfO2, respectively). Solution-based processing was used to achieve a fine-scale (i.e., nanometer-level) mixing of the reactants. The reactions were substantially completed at relatively low temperatures (<1500°C) and the resulting products had small average crystallite sizes (∼50–130 nm). However, these products contained some dissolved oxygen in the metal carbide lattice and higher temperatures were required to complete the carbothermal reduction reactions. Dry-pressed compacts prepared using ZrC-based powders with ∼100 nm crystallite size could be pressurelessly sintered to ∼99% relative density at 1950°C.