Bulk Si₂BC₃N ceramics were reinforced with SiC coated multi-walled carbon nanotubes (MWCNTs). The phase compositions, mechanical properties, and thermal shock resistance, as well as the oxidation resistance of the designed Si₂BC₃N ceramics were comparatively investigated. The results show that nano SiC coating can be formed on MWCNTs through pyrolyzing polysilazane, which improves the oxidation resistance of MWCNTs. A stronger chemical bonding is formed between the SiC coated MWCNTs and SiC particles, contributing to improved flexural strength (532.1 MPa) and fracture toughness (6.66 MPa·m^1/2). Besides, the 2 vol% SiC coated MWCNTs reinforced Si₂BC₃N ceramics maintains much higher residual strength (193.0 MPa) after thermal shock test at 1000 ℃. The enhanced properties should be attributed to: (1) the breaking of MWCNTs and the debonding between MWCNTs and SiC interfaces, which leads to more energy dissipation; (2) the rough surfaces of SiC coated MWCNTs increase the adhesion strength during the "pull out" of MWCNTs.

Multi-walled carbon nanotubes (MWCNTs) reinforced Si₂BC₃N ceramics were prepared through mechanical alloying (MA) and following spark plasma sintering (SPS). The thermal shock resistance of Si₂BC₃N ceramics was evaluated comparatively through ice water quenching test and theoretical prediction. Furthermore, the oxidation resistance of MWCNTs incorporated Si₂BC₃N ceramics was evaluated under high temperature. The results show that the calculated parameters such as the critical thermal shock temperature (R) and the thermal stresses resistance (R_st), as well as the toughness (R′′′′) are improved with addition of 1 vol% MWCNTs. In addition, the crack propagation resistance of 1 vol% MWCNTs incorporated Si₂BC₃N ceramics is obviously improved through generating more tortuous crack propagation paths attributing to the “crack bridging”, “pull-out”, and “crack deflection” mechanisms of MWCNTs. Therefore, the residual strengths of 1 vol% MWCNTs containing specimens remained the highest after the thermal shock tests. Besides, the present work also reveals that the oxidation resistance is more sensitive to relative density than MWCNTs addition.