Abstract
The SiO2-Al2O3-C system with Si/Al ratios corresponding to the compositions of Z=0.5 and Z=1.0 in β-sialon, was heated in flowing nitrogen, and the processes of carbothermal reduction and nitridation were investigated. Al2O3 promoted the reaction of the carbothermal reduction and nitridation. In this system, the SiO4-tetrahedoron near the AlO4-tetrahedoron of amorphous aluminosilicate or mullite, was easily reduced and SiO(g) was formed at low temperature. Then, the unknown product with the chemical composition of Si6AlO6N5 was formed by the reaction in SiO(g)-Al2O3-C-N2(g) system. In the next stage, Si6AlO6N5 was reduced by CO and nitridated by N2(g). β-sialon was formed via these reactions. At temperature above 1550°C, β-sialon was reduced to amorphous Si3N4. Finaly, the amorphous Si3N4 was reduced and carbureted to forming SiC.
