Field-activated pressure-assisted combustion synthesis of polycrystalline Ti3SiC2

The simultaneous synthesis and densification of the ternary Ti3SiC2 was investigated by the field-activated, pressure-assisted combustion method. Depending on temperature and time at temperature, relatively pure and nearly fully dense materials can be synthesized by this approach. The optimum conditions to produce this phase were a reaction temperature of 1525 degrees C and a time at temperature of 2 h. The product contained TiC as a second phase at a level of less than or equal to 2 mol%. The resulting ternary phase has typically elongated grains which were about 25 mu m in size. Within a range of applied force of 1-4 N, the microhardness of the product was relatively constant, ranging from 6 to 7 GPa. Investigations on the thermal and chemical stabilities of the ternary were also conducted, Vacuum annealing at temperatures of 1600 and 2000 degrees C resulted in the formation of a surface layer of TiC, while the air annealing at 1000 degrees C resulted in the formation of TiO2. Oxidation studies on the prepared Ti3SiC2 were made at temperatures ranging from 800 to 1100 degrees C. The results suggest a two-mechanism process, one dominating in the approximate range of 800-950 degrees C and the other in the range 950-1100 degrees C with corresponding activation energies of 137.7 and 312.5 kJ mol(-1). The results are explained in terms of two proposed reactions on the basis of microprobe analyses.