MULLITE FORMATION BY REACTION SINTERING OF QUARTZ AND ALPHA-AL2O3 - ATEM STUDY

Early stages of mullitization during reaction sintering of quartz and submicron alpha-Al2O3 powders were investigated by means of analytical transmission electron microscopy. The reaction sequence starts by for mation of a transient melt layer on the surface of the quartz grains. The viscous silica melt incorporates some alumina by dissolution of al pha-Al2O3. If the Al2O3 content of the liquid phase exceeds almost-equ al-to4 mol% mullite formation occurs mainly at alpha-Al2O3 grain junct ions. Less frequently, mullite formation inside the bulk of the liquid phase has been detected.