THE PREPARATION OF VARIOUS n-ALKYLAMMONIUMMONTMORILLONITE-POLYACRYLONITRILE INTERCALATION COMPOUNDS AND THEIR CARBOTHERMAL REDUCTION IN N₂

Abstract

Three kinds of n-CH₃ (CH₂) _nNH₃⁺-montmorillonite-polyacrylonitrile intercalation compounds (n=3, 5, 11) were prepared and converted to nitrides to investigate the effect of the amine chain length on carbothermal reduction and the subsequent nitridation. With n=3 and 5, the similar intercalation compounds having the basal spacings of ca. 19 Å were obtained. On the contrary, the intercalation compound with n=11 showed the basal spacing of 27.1 Å and contained the larger amount of the organic materials than the other intercalation compounds. After the decomposition of the n-alkylammonium ions, the basal spacings of the complexes with n=3 and 5 decreased to the value corresponding to the monolayer of carbon, whereas the spacing corresponding to the multilayer of carbon was observed in the complex with n=11. By heating these intercalation compounds in N₂ at 1100-1500°C, β-sialon, A1N, and SiC formed without the crystallization of the oxides. From the intercalation compounds with n=3 and 5, β-sialon formed by the treat-ments above 1100°C. On heating above 1200°C, SiC was obtained. AIN was detected in the products heated above 1300°C. In spite of its greatest organic content, the intercalation compound with n=11 showed the higher threshold temperatures, indicating its lowest reactivity. Therefore, the longer amine chain was disadvantageous for nitrides formation by carbothermal reduction, since the structural conditions in the interlayer space of the intercalation compounds influenced their reactivities to a great extent.