Abstract
Sintering behavior of the mixtures of kaolinite and basic magnesium carbonate (BMC) was investigated to obtain dense cordierite ceramics. Kaolinite and BMC were mixed by ball-milling in a molar ratio of nMgO⋅Al2O3⋅2SiO2 (n=0.8-1.4). Particularly fine mixtures were prepared by beads-milling after calcination. During firing of fine mixtures, magnesia disappeared completely by reaction with metakaolin to form amorphous particles below 900°C. Since the amorphous particles were very sinterable, the pressed specimens were densified up to about 90% at 900°C, and then μ-cordierite crystallized at about 940°C. Dense α-cordierite ceramics with relative density of≥95% were obtained at 1300°C from the mixtures of n=1.0-1.4, and the lowest linear thermal expansion coefficient was 2.2×10-6/K in the case of n=1.0, which is close to the composition of cordierite.
