Phase evolution and oxidation resistance of Si3N4/HfB2/HfBxCyN1–x–y ceramic nanocomposites prepared from tailored preceramic polymers

Single-source-precursor derived ceramics exhibit advantages for the preparation of Si-based ceramics with controllable phase composition and adjustable functional/mechanical properties, which has significant potential for (ultra)high temperature ceramic materials. Within the present work, a series of hafnium/boron-containing Si3N4-based ceramics (SiHfBCN) are prepared upon pyrolysis/annealing of the corresponding single-source-precursors in N2 atmosphere at different temperatures ranging from 1000 °C to 1700 °C. The high-temperature (micro)structural evolution with respect to the annealing temperatures and boron concentration was studied using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. The results show that the amorphous SiHfBCN ceramics convert upon crystallization into ceramic nanocomposites consisting of a α-Si3N4 matrix with embedded Si, HfB2, and HfBxCyN1–x–y. The formation and stability of HfBxCyN1–x–y solid solution were discussed in detail. Finally, the oxidation resistance of the obtained α-Si3N4/HfB2/HfBxCyN1–x–y ceramic nanocomposites was investigated by thermal gravimetric analysis in air.