Solid State Reactions in the Al-Si-C System

Abstract

The study is aimed to prevent the formation of the aluminium carbide compound Al4C3 that negatively affects Al-Si-C based materials. The reaction products of elementary aluminium, silicon and graphite as well as aluminium with either β-SiC or α-SiC without and with graphite at temperatures 1200°-2500 °C under different atmospheres and reaction times were characterized using powder X-ray diffraction and scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX) analysis. The results of the powder diffraction study show that under the conditions (1450 °C; 8 h; vacuum) the formation of Al4C3 could be prevented. The reaction products at those conditions consist of the ternary compound Al4SiC4 besides SiC and residual carbon. The ternary aluminium silicon carbide Al4SiC4 crystallizes in a hexagonal crystal system with unit cell dimensions a = 327.64(4) pm, b = 2171.2(6) pm and space group P63mc (no. 186). The crystal structure of Al4SiC4 is isostructural with Al5C3N and consists of layers of Al4C3 and SiC.