TIME-TEMPERATURE TRANSFORMATION CURVES FOR KAOLINITE ALPHA-ALUMINA

The C-shaped time-temperature-transformation curves (T-T-T curves) of cristobalite formation and the L-shaped T-T-T curves of alpha-alumina reaction were established for a high-purity kaolinite-alpha-alumina mi xture during heating. The results revealed that cristobalite formation in kaolinite was retarded by the presence of alpha-alumina between 12 50-degrees and 1350-degrees-C and was totally prohibited above 1380-de grees-C due to the reaction of kaolinite with alpha-alumina to form se condary mullite. The reaction of alpha-alumina with kaolinite was init iated at about 1250-degrees-C. It became quite extensive above 1380-de grees-C and was extremely fast at 1600-degrees-C and above, indicating the strong effect of the eutectic liquid formation at approximately 1 587-degrees-C in silica-alumina. The effectiveness of the established T-T-T curves was demonstrated and discussed.