Facile Precursor Synthesis of HfC–SiC Ultra-High-Temperature Ceramic Composite Powder for Potential Hypersonic Applications

Nanosized powder composites of hafnium carbide/silicon carbide (HfC–SiC) were successfully prepared by cross-linking and carbothermic reduction of a precursor. A novel high yield liquid precursor was synthesized by reacting acetylacetone (acac) modified hafnium tetrachloride (HfCl4) with tetraethyl orthosilicate (TEOS) and hydroquinone (HQ). The synthesized materials were investigated by XRD, FT-IR, carbon analyzer, Raman, TG/DTA, SEM, TEM, and EDS analysis. The resulting precursor pyrolyzed at 1500 °C for 3 h in argon converted into nanostructured ultra-high-temperature composite powder (containing both HfC and SiC) with a trace of free carbon. The polymer-to-ceramic transformation was investigated by TG/DTA revealing that carbothermic reduction of HfC and SiC started at 1225 and 1450 °C, respectively, with a total yield of 64% at 1500 °C. XRD revealed the powder composite was composed of HfC and β-SiC with a negligible amount of oxide impurities. SEM and TEM images reveals the Hf, Si, and C were homogeneously distributed in the sample at submicron scale with an average grain size of less than 50 nm for both HfC and SiC. The product of this synthesis approach is a promising precursor composite materials for hypersonic applications.