Thermal Expansion and Microstructure of Cordierite and Minllite Composite

Abstract

Dense two-phase composite bodies of cordierite and mullite with various volume fractions were fabricated by firing at 1450°C. The bending strength of the composites increased with increasing mullite fraction. It was revealed that their linear thermal expasion coefficients are proportional to the volume fraction of the constituent mineral. The expansion coefficients of the composites were investigated referring to Kerner's and Turner's equations, and the reason why Ker-ner's equation was better applicable to the composites was discussed. Stresses due to the difference in expansion coefficients between cordierite and mullite were verified by the X-ray diffraction method. Microcracks surrounding mullite particles formed in the cordierite phase of the composite body. And the shape of those cracks looked as if they had formed in a glassy matrix.