PILLARED MONTMORILLONITE CLAY AS A RAW-MATERIAL FOR THE SYNTHESIS OF BETA'-SIALON

To control the SiO2/Al2O3 ratio in a starting clay material for the synthesis of beta'-sialon by the carbothermal nitridation process, montmorillonite was pillared with Al2O3. Conversions to sialon of pillared clay (31% Al2O3) and reference unpillared montmorillonite (18% Al2O3) have been compared. Pillared montmorillonite yielded a mixture of beta'-sialon and various oxynitrides and oxycarbides of alumina as intermediate products. Pillared clay transformed faster during annealing than structural components of smectite alone. For the proper thermal treatment and clay/carbon ratio, both pillared and unpillared clays resulted in beta'-sialon solid solutions.