Aluminothermic reduction and nitriding of high silica materials (diatomite and bentonite) minerals

The reduction with aluminium and simultaneous nitriding of SiO2–Al2O3 compounds is a method used to obtain phases of the Si–Al–O–N system. SiAlON phases have important applications as ceramic materials. In this study, high silica minerals as diatomite and bentonite were reacted with Al and N2 up to 1650°C. The products of these reactions depend on several variables such as temperature, time, metallic Al content, etc. The principal techniques employed were XRD, thermal analysis, and EPMA. The reaction sequence indicates that silicon and AlN are intermediate compounds. Final reaction products are Sialons polytypoid and α-Al2O3. Enrichment in alumina is observed due to SiO(g) volatilization.