原位生成柱状莫来石和SiC晶须对Al2O3–SiC–C耐火材料性能的影响

In-situ Synthesis of Column-like Mullite and SiC Whiskers and its Effect on Al_2O_3–SiC–C Refractory Properties

以煅烧铝矾土、棕刚玉、板状刚玉、鳞片石墨、碳化硅粉为原料,单质Si粉为添加剂,酚醛树脂为结合剂,制备出Al_2O_3–Si C–C耐火材料。研究了不同热处理温度对材料显微结构及性能的影响。结果表明:在埋碳条件下,1 000℃烧成后样品中有柱状莫来石物相生成;1 400℃烧成后柱状莫来石长径比增大,同时还有Si C晶须生成。热处理温度从1 000℃升高到1 400℃时,样品显气孔率和常温耐压强度变化不明显,但常温抗折强度提高54.73%,达到8.17 MPa,载荷位移量增大近20%。3次热震后残余耐压强度保持率从54.36%(200℃烧成后)提高到89.10%(1 400℃烧成后)。原位生成的Si C晶须和发育良好的柱状莫来石显著提高了样品常温抗折强度、断裂韧性和抗热震性。

The Al2O3-SiC-C refractories were prepared with calcined bauxite, brown fused alumina, tabular alumina, flake graphite and silicon carbide as raw materials, Si powder as an additive and phenolic resin as a binder. The effect of calcination temperature on the microstructural evolution and properties of refractories was investigated. The thermodynamic calculation of AI-Si-O-C systems shows that mullite and SiC phases are stable after coking at an elevated temperature. The results indicate that the colunm-like mullite is formed in a coke bed after fired at 1 000℃. When the temperature is 1 400℃ the aspect ratio of the column-like mullite increases. Also, some SiC whiskers are generated in the refractories. It is indicated that the apparent porosity and cold crushing strength both are not changed obviously when the heat treatment temperature increases from 1 000 to 1 400℃. However, the cold modulus of rupture is increased by 54.73% （i.e., 8.17 MPa） and the load displacement is improved by nearly 20%. It is also found that after three thermal shock cycles, the residual strength ratio of samples after cured at 200℃ is 54.36%, and the value increases to 89.10% after fired at 1 400℃. The improvement in the flexural strength, fracture toughness and thermal shock resistance of the refractories could be attributed to the in stiu formation of well-developed column-like mullite and SiC whiskers.