MULLITE SYNTHESIS AND FORMATION FROM KYANITE CONCENTRATES IN DIFFERENT CONDITIONS OF HEAT TREATMENT AND PARTICLE SIZE

The process of mullitization of kyanite concentrate was studied at different conditions of heat treatment (۱۴۰۰– ۱۶۰۰ °C and ۰.۵ – ۳.۵ hours) and particle size of raw materials (۳۸-۳۰۰ ?m). Kyanite concentrate was obtained fromore-dressing of kyanite deposits of Mishidowan-Bafgh region at ۱۰۰ km northeastern part of Yazd. The results ofmicrostructure (shape, distribution and size of the grains) and phase evolution studies by SEM and XRD showed thattotal transformation of kyanite to mullite takes place by heat treatment between ۱۵۰۰ –۱۵۵۰ °C during ۲.۵ hours.. Attemperatures below ۱۵۰۰ °C need-like mullite grains are always produced. At higher temperatures the mullite grainsreveal rounded and platelet morphology. At ۱۵۵۰ °C, the rate of mullitization and densification were improved byincreasing soaking time from ۱h to ۳h and decreasing particle size of materials from ۳۰۰ to ۳۸ m

Keywords:

Kyanite , Kinetic of mullitization , Heat treatments , Densification , Microstructure , Mishidowan-Bafgh deposits