SYNTHESIS OF CORDIERITE POWDER BY SPRAY-DRYING

Homogeneous multicomponent silicate powders may be prepared when a silicon alkoxide is hydrolyzed in an acidic aqueous solution of metallic salts and the resulting sol rapidly transformed into a powder. By spray-drying a sol of Al and Mg nitrates and TEOS at 200-degrees-C, followed by calcination to 750-degrees-C, a cordierite precursor powder is produced which crystallizes into alpha-cordierite via mu-cordierite, but expands upon heating instead of sintering. If a water-soluble organic polymer is added to the sol before spray-drying, the chemical homogeneity of the powder is improved, the specific surface area greatly increased and the compacted powder densifies before crystallizing.