The formation of β-sialon in the carbothermal reduction process of montmorillonite-polyacrylonitrile intercalation compounds at 1100°C

Only β-sialon was obtained from n-alkylammonium-montmorillonite-polyacrylonitrile (PAN) intercalation compounds in the carbothermal reduction process at 1100°C in N₂. Very little oxide crystallized during the conversion. However, an amorphous phase was still present after treatment for 6 h. The main constituent metals in montmorillonite (Si, Al, Mg, and Fe) were mostly retained during the treatment. Since similar XRD patterns were obrained from two kinds of intercalation compounds, having different carbon contents, the suppression of the formation of other phases was not subject to the amount of carbon. When a montmorillonite-carbon mixture having a larger amount of carbon was heated at 1150°C for 6 h, oxides were mainly formed. Therefore, the intimate mixing in the 2D structure of the intercalation compounds resulted in a lower threshold temperature for β-sialon formation, at which other phases did not form.