Preparation of mullite ceramics from bayer electrofilter fines and low kaolinite clay

In this paper are investigated microstructural, phase, physical and mechanical properties of mullite ceramics obtained from clay and Bayer electrofilter fines. Clay and alumina were mixed in such ratio that provides the amount of AlO23 and SiO2 corresponding composition of mullite. One mixture was manually mixed and other was milled three hours in ceramic mill. After isostatic molding and heat treating at 1580°C and 1635°C XRD analysis revealed approximately 60% of mullite and 40% of corundum in first mixture and in second mixture 70% of mullite and 30% of corundum. Two types of mullite were observed in SEM micrographs beside corundum grains and glassy phase. The results of investigation indicate that preparation of mullite ceramics from these raw materials is possible, if clay and alumina are well homogenized and milled before molding.