PRODUCTION OF BETA'-SIALONS THROUGH CARBON OXIDE NANOCOMPOSITES OBTAINED FROM MONTMORILLONITE AROMATIC-AMMONIUM COMPLEXES

Carbon/oxide nanocomposites were formed by thermal treatment of montmo rillonite/ammonium complexes, in the range 500-1000-degrees-C. Althoug h montmorillonite is decomposed above 700-degrees-C, the lamellar stru cture is maintained up to 1000-degrees-C by the presence of ''intercal ated'' carbon. The amount of carbon in the composites can be adjusted by varying the nature of the organic ammonium cations so as to reach t he computed value given by the theoretical equation for the formation of beta'-SiAlON (19%). Starting from the montmorillonite/safraninium c omplex, the carbon content in the nanocomposite was 17.3%. beta'-SiAlO N was synthesized by heat treatment of this composite to 1350-degrees- C under nitrogen. Since the oxide and the carbon source are intimately mixed on the nanoscale, beta'-SiAlON is even obtained at temperatures as low as 1100-degrees-C. Compared with other processes, the temperat ure for beta'-SiAlON formation can be lower by approximately 300-degre es-C.