Phase evolution during spark plasma sintering of novel Si₃N₄-doped TiB₂–SiC composite

Spark plasma sintering process was employed to fabricate TiB₂–SiC and novel Si₃N₄-doped TiB₂–SiC ceramic composites at 1900 °C for 7 min under 40 MPa. The microstructural development of TiB₂-based composites was significantly influenced by the addition of SiC as a reinforcement phase and Si₃N₄ as a sintering aid. Thermodynamic assessment, X-ray diffractometry, scanning electron microscopy and energy dispersive spectroscopy disclosed the in-situ formation of TiC, B₄C and SiO₂ in both samples as well as TiN and BN in the Si₃N₄-doped TiB₂–SiC sample through the chemical reactions of SiC and Si₃N₄ additives with the surface oxide impurities of TiB₂ particles (TiO₂ and B₂O₃). The elimination of harmful oxide layers and the in-situ formation various secondary phases had remarkable influences on the sinterability and final microstructure of TiB₂.