Ceramics-Silikáty

High-purity SiC-ZrC composite powders were successfully synthesised via a carbothermal reduction method using zirconium silicate (ZrSiO₄), silica sol, and carbon black as the raw materials. The synthesis involved the systematic control of the calcination temperature (1450–1650 °C), holding time (1–4 h), and SiC/ZrC mass ratio (7/3, 5/5, 3/7). The effects of these parameters (SiC/ZrC ratio, calcination temperature, holding time) on the phase composition, weight loss rate, and microstructure of the SiC-ZrC composite powders were thoroughly investigated, and the underlying reaction mechanism was elucidated. The XRD analysis and weight loss measurements revealed that: ZrSiO₄ begins to decompose, generating a small amount of SiC at 1450 °C; the reaction is essentially complete, yielding high-purity SiC and ZrC, by 1500 °C; temperatures of 1550 °C and above further enhance the crystallinity. Elevated temperatures significantly shorten the required reaction time, with the reaction completing within 1 h at 1550 °C, compared to 4 h at 1450 °C. The SEM observations demonstrated that the quantity and size of SiC whiskers are regulated by the calcination temperature, holding time, and SiC/ZrC ratio. Higher temperatures or prolonged holding times increase the whisker diameter, but reduce their number. The formation of the SiC-ZrC composite powder follows a multi-step reaction mechanism: ZrSiO₄ completely decomposes into highly reactive ZrO₂ and SiO₂ at 1500 °C. Subsequently, SiO₂ is converted to SiC via gas-solid or gas-gas reaction pathways, while ZrO₂ is converted to ZrC either through direct carburisation or via an intermediate ZrO (g) species. This study provides both theoretical and experimental foundations for the precise synthesis of SiC-ZrC composite powders with controlled composition and morphology.