Self-propagating high-temperature synthesis of Ti₃SiC₂: II. Kinetics of ultra-high-speed reactions from in situ neutron diffraction

In situ neutron diffraction data at 0.9-s time resolution during the self-propagating high-temperature synthesis of Ti₃SiC₂ from stoichiometric 3Ti+SiC+C mixtures have been further analyzed to give the phase quantities during all five stages of the identified reaction [(i) preheating, (ii) α→β phase transformation in Ti, (iii) preignition reactions, (iv) intermediate phase formation, and (v) rapid nucleation and growth of Ti₃SiC₂]. The phase quantities thus determined have been used, in conjunction with temperatures estimated from lattice parameters and thermal expansion data, to determine the kinetic parameters for the nucleation and growth stage using a nonisothermal form of the Avrami kinetic equation. The analysis gave an Avrami exponent, n, close to 3 in agreement with nucleation and the observed two-dimensional growth of Ti₃SiC₂ crystals. An activation energy of ~45 kJ/mol was also estimated