SOL-GEL SYNTHESIS OF A MIXTURE FOR PREPARING CORDIERITE

Sol-gel processing was used to prepare an amorphous precursor to cordi erite from pulverized crystal hydrates of magnesium and aluminum chlor ides, sodium metasilicate, and sodium carbonate. Upon dissolution of t he salts in the water of crystallization, they react to form a mixed h ydrogel of magnesium, aluminum, and silicon oxyhydroxides with an admi xture of basic carbonates. The hydrogel is dried, washed to remove sod ium chloride, and roasted to obtain cordierite. Roasting of nondehydra ted xerogel (drying at 100 degrees C) gives mullite as the primary pro duct in the amorphous mixture, whereas roasting of dehydrated xerogel (drying at 400 degrees C) gives spinel.