Properties of Si₃N₄/SiC Refractory Prepared by Cr₂O₃ Catalyzed Nitridation

With SiC powder and silicon powder as raw materials, in-situ synthesized Cr₂O₃ as catalyst, Si₃N₄/SiC refractory was prepared by catalytic nitridation. The effects of catalyst addition amount and nitridation temperature on the phase composition, micromorphology, physical properties and mechanical properties of the refractory were investigated. The results show that when the nitridation temperature was 1 673 K and the Cr₂O₃ content (mass ratio of Cr₂O₃ to silicon powder) reached 3wt%, the silicon powder was completely nitrided; the refractory was composed of grain-like SiC, whisker-like α-Si₃N₄ and β-Si₃N₄. With increasing content of Cr₂O₃, the amount and length of Si₃N₄ whisky increased; the refractory became densification. With the rise of nitridation temperature, the flexural strength and compressive strength of the refractory increased. When the nitridation temperature was 1 673 K and the Cr₂O₃ content was 3wt%, the flexural strength and compressive strength reached the largest values of 34 MPa and 132 MPa, respectively.