Potential and Possibility of Mullite Ceramics Study of Development Possibilities and Potential for Mullite Ceramics

摘要

Mullite is familiar to us as one of the main minerals contained in traditional ceramics such as refractories, porcelain, etc., which are products fabricated by the firing of items prepared from natural raw materials, including clay minerals. In the 1970 decade, high-purity mullite ceramics were produced using chemically pure raw materials". These high-purity mullite ceramics were reported to have mechanical properties that were superior to alumina ceramics at high temperatures, comparing favorably with silicon nitride ceramics2', a typical non-oxide ceramic type, whereby they were expected to be candidates for high temperature materials, for use in oxidizing atmospheres. The sintered mullite bodies, however, usually contain glass as an intergranular phase, which degrades the superior mechanical properties at high temperatures. The origin of the glass phase is based on the heterogeneous nature of the chemical components during the preparation process and the presence of a small amount of chemical impurities. The Al_2O_3-SiO_2 phase diagram, after Klug et al., also shows a liquid phase above 1600°C, even though 3:2 mullite has the stoichiometric composition.