Self‐Propagating High‐Temperature Synthesis of Ti ₃ SiC ₂ : I, Ultra‐High‐Speed Neutron Diffraction Study of the Reaction Mechanism

Abstract

In situ neutron diffraction at 0.9 s time resolution was used to reveal the reaction mechanism during the self‐propagating high‐temperature synthesis (SHS) of Ti 3 SiC 2 from furnace‐ignited stoichiometric 3Ti + SiC + C mixtures. The diffraction patterns indicate that the SHS proceeded in five stages: (i) preheating of the reactants, (ii) the α→β phase transformation in Ti, (iii) preignition reactions, (iv) the formation of a single solid intermediate phase in <0.9 s, and (v) the rapid nucleation and growth of the product phase Ti 3 SiC 2 . No amorphous contribution to the diffraction patterns from a liquid phase was detected and, as such, it is unlikely that a liquid phase plays a major role in this SHS reaction. The intermediate phase is believed to be a solid solution of Si in TiC such that the overall stoichiometry is ∼3Ti:1Si:2C. Lattice parameters and known thermal expansion data were used to estimate the ignition temperature at 923 ± 10°C (supported by the α→β phase transformation in Ti) and the combustion temperature at 2320 ± 50°C.