Synthesis Mechanisms of the Combustion Synthesis of IntermetCers Composites
Combustion synthesis techniques have been applied to an equiatomic mixture of Aluminium, Nickel, Titanium and Carbon powders in order to obtain NiAl/TiC composites. Both combustion modes have been used: the Self-propagating High-temperature mode (SHS), in which the reaction propagates through the sample under the form of a heat wave and the Thermal Explosion mode (TES), in which the reaction occurs simultaneously in the complete sample. The reactions have been followed in-situ by time-resolved diffraction, using synchrotron X-rays for the SHS mode and neutrons for the TES mode. Scanning Electron Micrographs and X-ray diffraction patterns of the final product have shown that the same final products were obtained when the mixture was synthesised under both combustion modes: a composite made of small and round TiC particles (~1 micron) embedded into a matrix of larger NiAl grains (5 microns). However, the Time-Resolved Diffraction studies have shown that, even with the same final products, the two combustion modes follow two completely different routes. Thus, for the SHS mode, the reaction is triggered by the formation of Nickel Aluminide and 3 intermediate phases are observed, and for the TES mode, the self-sustained reaction starts with the formation of Titanium Carbide and no intermediate phases have been seen.
C. Curfs et al., "Synthesis Mechanisms of the Combustion Synthesis of IntermetCers Composites ", Advances in Science and Technology, Vol. 45, pp. 1029-1034, 2006