Effects of TiC, Si, and Al on Combustion Synthesis of Ti₃SiC₂/TiC/Ti₅Si₃ Composites

The fabrication of Ti₃SiC₂ from TiC-containing reactant compacts was investigated by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS). The initial sample composition was formulated based on (3 - x)Ti + ySi + (2 - x)C + xTiC + zAl, with stoichiometric parameters of x from 0 to 0.7, y = 1.0 and 1.2, and z = 0 and 0.1. For all samples studied, combustion was sufficiently exothermic to sustain the reaction in the SHS manner. Due to the dilution effect of TiC, combustion wave velocity and reaction temperature substantially decreased with TiC content. When compared with the TiC-free sample, the TiC-containing sample facilitated the formation of Ti₃SiC₂ and the TiC content of x = 0.5 produced the highest yield. Excess Si (y = 1.2) to compensate for the evaporation loss of Si during combustion and the addition of Al (z = 0.1) to promote the phase conversion were effective in improving the evolution of Ti₃SiC₂. All final products were composed of Ti₃SiC₂, TiC, and Ti₅Si₃. For the TiC-containing samples of x = 0.5, the weight fraction of Ti₃SiC₂ increased from 67 wt.% in the sample without extra Si and Al to 72 wt.% in the Si-rich sample of y = 1.2 and further up to 85 wt.% in the Si-rich/Al-added sample of y = 1.2 and z = 0.1. As-synthesized Ti₃SiC₂ grains were in a thin plate-like shape with a thickness of 0.5-1.0 μm and length of about 10 μm. Ti₃SiC₂ platelets were closely stacked into a layered structure.