From molecular precursors to ultra-high temperature ceramics: A novel synthesis of hafnium carbonitride nanoceramics

Hafnium carbonitride (HfC x N 1– x ) ceramics have drawn considerable interest due to their exceptional mechanical and thermophysical properties. Herein, we report a novel single-source precursor with Hf–N bonds as the main chain and fabricate HfC x N 1– x ceramics after pyrolysis of the precursor. The synthesis, ceramic conversion, and microstructural evolution of the single-source precursor as well as the derived HfC x N 1– x ceramics treated under various atmospheres were investigated. The results indicate that in an argon atmosphere, the nitrogen content within HfC x N 1– x decreases with rising temperature. While under a nitrogen atmosphere, the high concentration of N 2 facilitates the rapid conversion of HfO 2 to Hf 7 O 8 N 4 , which subsequently promotes the transformation of the HfC x N 1– x solid solution ceramics. During this process, there is also an inhibitory effect of N 2 on the tendency of HfN into HfC. Moreover, the desired chemical composition of HfC x N 1– x can be regulated by adjusting the N 2 concentration in the heat treatment atmosphere. The present work proposes a novel strategy for the single-source precursor-derived carbonitride ceramics and provides a deep understanding of the preparation and property modulation of HfC x N 1– x ceramics.