Progressive phase changes during the reaction of 'clay-Al-N_2' and 'mullite-Al-N_2' in the Si-Al-O-N system

摘要

The reduction with Al and simultaneous nitriding of alumino-silicate compounds leads to the formation of phases of the Si-Al-O-N system, very important in the ceramic field. Products of these reactions depend on several variables such as temperature, time, metallic Al content, etc. In this work, reactions of Al on clay and mullite were studied. Reaction products are measured quantitatively by XRD. The crystalline phases formed (mullite, α-Al_2O_3, X-phase, β′-sialon, 15R-sialon) are represented as a function of the temperature (range 1300-1650℃; 180 min) and the Al~0 content (range 14-26%). The characterization of the products is completed with surface BET and SEM measurements. The mechanism of the reaction 'clay-Al-N_2' at temperatures lower than 1300℃ was studied; Si and AlN were detected as intermediate products. SiO(g) loss was determined by weight loss and EPMA.