Effects of Calcination and Grinding of Starting Kaolin Material on Microstructure and Physical Properties of Cordierite Ceramics.

Abstract

Cordierite sintered bodies were prepared from the mixtures of raw or calcined materials, which were composed of kaolinite, talc and alumina. As many cracks occurred in sintered bodies prepared from mixture of raw materials, the bodies experienced the low thermal expansion coefficients of 1.06-1.39×10-6/°C (25-900°C), and the low bending strengths of 50-70MPa. The cracks were caused by the orientation of cordierite crystals during the sintering process, owing to the orientation of kaolinite in the forming process. On the other hand, in bodies sintered from the mixture of calcined materials, there were no cracks, the thermal expansion coefficients were higher, about 2.0×10-6/°C, and the bending strength was about 120MPa.