The role of liquid phase in solid combustion synthesis of Ti3SiC2

A comparison of the experimentally determined phase composition of products of solid combustion and solid–state reactions in the Ti–Si–C system with the expected equilibrium phase composition and adiabatic temperatures attainable with different reactive Ti:Si:C powder mixtures, indicates the conditions necessary for a synthesis of Ti3SiC2. This should be possible only when, during solid combustion, the peak temperatures reach and exceed the melting point of TiC, which is the primarily formed solid product in this system. Otherwise, the impoverishment of the reactants in Ti and C brings about a decomposition of Ti3SiC2 if initially formed. Thc latter behaviour was observed when only solid–state reactions occurred at low heating rates and on solid combustion when the adiabatic, and thus also the peak temperatures under real conditions, were found to be lower than the melting point of TiC. The synthesis of Ti3SiC2 represents a case study of the role of the liquid phase in determining the phase composition of solid combustion products, in addition to the earlier recognised role of the liquid phase in ignition and acceleration of the reaction rates on solid combustion.