Effect of sintering temperature on the phase composition and microstructure of anorthite-mullite-corundum porous ceramics

The effect of sintering temperature on the phase composition and microstructure of anorthite-mullite-corundum porous ceramics prepared from kaolinite gangue, Al(OH)3 and CaCO3 were studied by SEM, XRD and Factsage 6.2 thermalchemical software calculation. It was found that the contents of anorthite, mullite and corundum in porous ceramics depended little on the sintering temperature, but depended mostly on the chemical composition of specimens. Anorthite and mullite existed in the pseudomorphs of kaolinite gangue which were dense and corundum existed in the Al(OH)3 pseudomorphs with micropores. With elevating sintering temperature from 1300 °C to 1450 °C, the apparent porosity of the specimens changed a little but the size of secondary pores increased because of increase of liquid content, resulting in improvement of sintering and elevation of cold crushing strength of specimens. The size distributions of primary pores were almost the same in the specimens sintered at 1300 °C and 1400 °C. In specimens sintered at 1450 °C, the pores in Al(OH)3 pseudomorphs had a considerable growth because sintering of the Al2O3 crystallites was improved.