Mullitization of andalusite is considered. This phase transition isbased on the mechanism ofpolymorphism(which holds the grain shape)and on the chemistry of solid-phase processes. Mullite is orientedalong C-axis of generating andalusite crystal. Single crystal ofandalusite is transformed into mullitecompound with capillary poresfilled with glass-phase saturated withamorphous silica. Capillariesform the net of tightly bound tubular poreswith 1-μm cross-section that are oriented along C-axis which iscommon both for mullite and parent andalusite. About 80% of theglass-phase is stored in thecapillary pores of mullite. The results obtained are tested inreactions of andalusites of different grain composition with powderalumina and used in production of unshaped refractories havingultra-low cement content and cement-free masses with fine-grainedandalusite and alumina.
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