Layered growth of Ti_2AlC and Ti_3AlC_2 in combustion synthesis

摘要

In Ti-Al-C system two ternary carbides of Ti_2AlC and Ti_3AlC_2 were prepared by combustion synthesis. Laminated grain morphology and a terraced structure consisting of several parallel laminated layers were observed. On the basis of SEM and TEM results, a layered growth mechanism was proposed to describe the formation of the terraced structure. In this mechanism, the ternary carbide grains will undergo a preferential growth, i.e. each layer grows fast and expands quickly in the basal plane and all the layers are successively stacked along the normal direction identical to the c-axis in the hexagonal structure. This preferential growth characterized by the terraced structure was widely observed in this study and hence may be a common behavior during the growth of Ti_2AlC and Ti_3AlC_2 crystals in combustion synthesis.