Structure evolutions of the polymer derived medium-/high-entropy metal carbides

Ceramic powders with low oxygen content are highly demanded in monolithic ceramics. In this work, a series of medium-/high-entropy ceramic (HEC) particles, including (Zr 0.25 Ta 0.25 Nb 0.25 Ti 0.25 )C, (Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 W 0.2 )C, (Zr 1/6 Ta 1/6 Nb 1/6 Ti 1/6 W 1/6 Hf 1/6 )C (Zr 1/7 Ta 1/7 Nb 1/7 Ti 1/7 W 1/7 Hf 1/7 V 1/7 )C, and (Zr 1/8 Ta 1/8 Nb 1/8 Ti 1/8 W 1/8 Hf 1/8 V 1/8 Mo 1/8 )C, were successfully fabricated by the polymer-derived ceramic (PDC) route. The structure evolutions of the precursor demonstrated that HEC particles obtained at 1800 °C possessed a single phase and rock-salt structure. All the samples had the similar microstructures (hillock structure) and a low oxygen impurity content (less than 2.00 wt%). The results also demonstrated that the as-obtained HEC particles had a disordered distribution of elements from nanoscale to microscale. This work proved a new method to fabricate the HEC powders with low oxygen impurity content and the HEC precursors for further obtaining the nanofibers or ceramic matrix composites .