Effects of excess Si and Al on synthesis of Ti3SiC2 by self-sustaining combustion in the Ti-Si–C-Al system

Fabrication of Ti₃SiC₂ from elemental powder compacts was conducted by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS). Samples were formulated with three atomic ratios of Ti:Si:C = 3:1:2, Ti:Si:C = 3:1.2:2 (with excess Si by 20 mol.%), and Ti:Si:C:Al = 3:1.2:2:0.1 (a Si-rich and Al-added composition). Combustion reaction was highly exothermic and combustion wave velocity (from 4.1 to 8.8 mm/s) and temperature (from 1340 to 1610 °C) increased significantly with sample compact density varied in the range of 45% to 57.5% TMD (theoretical maximum density). In addition to the sample density, excess Si and a small amount of Al contributed greatly to the formation of Ti₃SiC₂. For the powder compacts of 57.5% TMD, the product synthesized from the sample of Ti:Si:C = 3:1:2 was composed of Ti₃SiC₂, TiC, and Ti₅Si₃ at 64 wt.%, 28 wt.%, and 8 wt.%, respectively. The sample with excess Si by 20 mol.% yielded a product with a weight proportion of Ti₃SiC₂:TiC:Ti₅Si₃ = 70:27:3. The product having the highest yield of Ti₃SiC₂ was obtained from the Si-rich/Al-added sample, which produced Ti₃SiC of 83 wt.%, TiC of 13 wt.% and Ti₅Si₃ of 4 wt.%. As-synthesized Ti₃SiC₂ grains were in a thin plate-like shape with 0.5–1.5 µm in thickness and 5–10 µm in length. Ti₃SiC₂ platelets were stacked closely into a layered structure.