Improved oxidation resistance of SPS sintered Si2BC3N ceramics with disilicides (MoSi2, HfSi2, TaSi2) addition

Although Si2BC3N ceramics have excellent oxidation resistance under high temperature (1000-1400 degrees C) in both dry and moist air, the oxidation resistance under higher temperatures (above 1400 degrees C) are still challenged due to the quick escape of volatile CO, B2O3 and SiO. Generally, the formation of stable and continuous protective layer is critical for improving the oxidation resistance under high temperature. Given the chemical compatibility and the formation of nonvolatile oxides after oxidation, the present work mainly investigated the influences of disilicides addition, including MoSi2, HfSi2 and TaSi2, on the phase composition and oxidation resistance of Si2BC3N ceramics sintered by SPS. The results showed that nano sized disilicides would transform into carbides (MoC, Mo5Si3, and TaC) and oxides (TaO, HfO2) during sintering process. The preferential oxidation of Mo and Hf related phases and the formation of much stable oxidation layer could improve the oxidation resistance significantly, where the oxidation layer thickness was less than 10 mu m after testing at 1600 degrees C for 3 h.