Effects of attrition milling on the decomposition of kyanite (Al2SiO5) and its reaction with (x-alumina (Al2O3) to form stoichiometric mullite (3Al(2)O(3)center dot 2SiO(2)) are reported. Kyanite-alumina mixes were attrition milled for times from 1 h to 12 h. With increasing milling time, the kyanite decomposition was accelerated and secondary mullite formation from the reaction between the rejected silica and the added alumina was enhanced. Milling reduced the decomposition expansion from +15.0% to +0.1 % and the final contraction or densification from +2.5% to -13.7%. During firing complete mullite formation occurred after firing at only 1623 K/1h (135 degrees C/1 h) to produce a dense mullite ceramic with a fine grain size (similar to 1 mu m).

Keywords: kyanite; alumina; mullite; sinterization and attrition milling