Solid State Reactions in the Al‐Si‐C System

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.