Effects of TiC, Si, and Al on Combustion Synthesis of Ti(3)SiC(2)/TiC/Ti(5)Si(3) Composites

The fabrication of Ti(3)SiC(2) 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 Ti(3)SiC(2) 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 Ti(3)SiC(2). All final products were composed of Ti(3)SiC(2), TiC, and Ti(5)Si(3). For the TiC-containing samples of x = 0.5, the weight fraction of Ti(3)SiC(2) 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 Ti(3)SiC(2) grains were in a thin plate-like shape with a thickness of 0.5–1.0 μm and length of about 10 μm. Ti(3)SiC(2) platelets were closely stacked into a layered structure.