Dense Mullite from Attrition‐Milled Kyanite and Aluminum Metal

Dense mullite was produced through the reaction and sintering of an attrition‐milled mixture of kyanite (Al 2 O 3 ·SiO 2 ) and aluminum metal. Kyanite and aluminum were attrition‐milled then slowly heated at 1°3C/min to 1100°3C in air, and rapidly heated to 1600°3C and held for 1 h. During heating, the aluminum metal is oxidized first in the solid state and then as a liquid. The attrition‐milled kyanite decomposes yielding mullite and rejecting silica, which then reacts with the alumina formed from oxidation of the aluminum. Expansion from the aluminum oxidation and kyanite decomposition partially compensates for the normal sintering shrinkage. A dense, fine‐grain‐size mullite results.