Influence of mixing on mullite formation in porcelain

Various forms of mullite occur in porcelains, Primary mullite forms from de composition of pure clay. Secondary mullite forms from reaction of feldspar and clay and feldpar, clay and quartz. Which of these forms is strongly de pendent on the extent of mixing of the body raw materials. Additionally, in aluminous porcelains tertiary, mullite may precipitate from alumina-rich l iquid obtained by dissolution of alumina filler. The size, shape and compos ition of the mullite crystals is controlled by the fluidity of the local li quid matrix from which they precipitate and grow, which itself is largely d etermined by the extent of mixing of the original powder batch. (C) 2001 El sevier Science Ltd. All rights reserved.