Effect of silicon addition on mechanical properties of mullite-SiC composite refractories

摘要

Mullite-SiC composite refractories were prepared using mullite, α-SiC, Si and Al₂O₃ as starting materials via carbonization reaction sintering by buried in coarse coal particles. The phase composition and mechanical properties of the composite refractories were studied. Results showed that main phases in the composite refractories consisted of mullite, α-SiC, β-SiC and a small amount of cristobalite. Both bulk density and flexural strength of the samples increased with the increase of silicon addition. The samples prepared at 1400°C, with 12 mass % of silicon content added in the initial raw materials, had better properties compared with the other samples, with bulk density of 2.28 g/cm3, flexural strength of 32.63 MPa, and retained flexural strength of 35.92 MPa after thermal shock by 5 times water quenching from 1200°C to room temperature. The slight increasing of flexural strength after 5 times thermal shock trials is arose from the protective oxidation of α/β-SiC and the second-sintering of samples.