Effect of Si₂BC₃N additions on the oxidation of Ta₄HfC₅ ceramics at 900–1100 °C

Si₂BC₃N content held the key on the oxidation scale growth and damage mechanism of Ta₄HfC₅ ceramics oxidized at 900–1100 °C. Si₂BC₃N addition increased the oxidation scale thickness due to the micro-pores generated by BN(C) oxidation constructing oxygen-diffusion channel. However, Ta₄HfC₅-10 wt% Si₂BC₃N showed better oxidation resistance in the Ta₄HfC₅-5–20 wt% Si₂BC₃N ceramics, resulting from the dynamic equilibrium of pores healing and tantalum-hafnium silicate glass generation. Generally, Ta₄HfC₅ tended to oxidize firstly followed by the oxidation of Si₂BC₃N, whereas oxidizing products of Si₂BC₃N like substantial B₂O₃ and few SiO₂ were insufficient to the formation of dense oxide scale at 900–1100 °C.