BASED ON IT IN THERMAL CYCLING IN A HYDROGEN ATMOSPHERE

The change in chemical analysis of the 3-0.5 mm fraction grains was insignificant while in the grains of the finer than 0.5 mm fraction a decrease in weight share of SiO 2 related to decomposition of silica and an increase in weight share of AI20 ~ are observed (Table i). the presence of metallic silicon and iron in the original sample of mullite is an indication of the presence of a weakly reducing atmosphere in fusion of it. Reduction of the silica-containin g component of the fused mullite during thermal cycling occurs only before formation of the volatile metastable SiO and, therefore, an increase in the quantity of silicon in the mullite grains does not occur.