Boehmite sol is synthesized via sol-gel process using Al 2(SO 4) 3·18H 2O and (CH 2) 6N 4 as starting materials, then adding silica sol into boehmite sol to prepare mullite precursor gels. XRD studies are performed to characterize the gels. It is found that the gel can be transformed into mullite when calcined at 1100℃ and completed at 1300℃. Corundum-mullite firebricks with different additions of the mullite precursor gel are made by mixing, semi-dry pressing and then sintering at 1520℃. Apparent porosity, bulk density, flexural strength and thermal shock resistance are measured. Results show that the mullite gel can improve densification and strength of corundum-mullite firebricks, especially enhance the thermal shock resistance. SEM micrographs show that the gel added can be formed into needlelike and elongated mullite in the matrix, whose micromorphology can enhance the strength and thermal shock resistance of the samples.
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