Influence of curing atmosphere on the pyrolysis mechanism of (Hf_1/2Zr_1/3Ti_1/6)C precursor

This work systematically investigated the effects of curing atmospheres (air vs. nitrogen) on the pyrolysis mechanism of (Hf_1/2Zr_1/3Ti_1/6)C (HZT) liquid precursor. The results indicated that curing in an air atmosphere led to the formation of HfO₂ nanocrystals in the curing products. These nanocrystals served as nucleation sites during the following polymer-to-ceramic process, facilitating the generation of numerous small-sized oxide nanocrystals, which exhibited high reactivity and promoted the carbothermal reduction reaction. Detailed analysis of the Cued-Air samples demonstrated a complex phase evolution: (1) formation of HfO₂, ZrO₂, and TiO₂ nanocrystals at 600°C, (2) solid-solution into (Hf, Zr, Ti)O₂ at 800°C, (3) carbothermal reduction reaction to form Ti-rich Ti(Hf, Zr)C and (Hf, Zr)-rich (Hf, Zr)TiC solid-solution at 800°C–1200°C, (4) diffusion to form a homogeneous HZT solid-solution ceramics at 1400°C–1600°C. The results particularly highlight the crucial role of curing atmosphere in controlling nanocrystal formation and subsequent phase evolution during pyrolysis. This investigation offers valuable theoretical insights and experimental references for understanding curing and pyrolysis process of multi-component solid-solution carbide ceramic precursors.