Abstract
The effect of calcined kaolin grain size on firing process and physical properties of cordierite ceramics was studied using kaolin, talc and α-alumina as a starting materials. Formation temperature of cordierite crystals from the finest kaolin with average grain size, 0.51μm, was about 50°C lower than that from the most coarse kaolin with average grain size, 2.23μm. The sintering performance was improved by using the fine calcined kaolin powder, because diffusion and reaction progressed in firing process due to the increase of contact area of starting powders. Finer kaolin powders contributed to a decrease in porosity and to a densification of fired bodies, so that the bending strength was increased from 50 to 80MPa with a decrease in kaolin grain size from 2.23 to 0.51μm. The thermal expansion coefficient was constant, 1.6-1.8×10-6/°C (50-900°C), for the fired bodies at 1300 and 1350°C independently of kaolin grain size.
