Morphological evolution during reaction sintering of Ti, SiC and C powder blend

A powder blend of Ti, SiC and C at a molar ratio of Ti:SiC:C = 3:1:1 was compacted into cylinder and sintered in vacuum for the synthesis of Ti3SiC2. The microstructure of synthesized Ti3SiC2 showed unique morphology. Variation in phase and microstructural morphology with temperature during sintering was investigated by X-ray diffraction analysis and a scanning electron microscope equipped with an energy dispersive X-ray analyzer in order to elucidate reaction mechanism. Two kinds of powder blends, Ti/Si and Ti/C, were also compacted and sintered to confirm the effect of diffusion of Si and C atoms into Ti particles on the morphological change of Ti particles. As a result, we proposed the progress of synthesis as follows: (1) Si and C atoms start to diffuse into Ti particles from SiC and C particles over 1023 K, (2) the diffusion of Si and C atoms is enhanced rapidly over α/β phase transition temperature of Ti, which results in the formation of shell structure having ruffled surface composed of Ti5Si3 and TiC on Ti particle surfaces, (3) the shell grows and joins together with neighbor ones and pure Ti core in Ti particles reduces in size, (4) Ti3SiC2 is formed by the reaction of Ti5Si3 with TiC over 1623 K, (5) finally, Ti3SiC2 with TiC is synthesized over 1823 K. The joined shell structure having ruffled surface formed during sintering remained after the formation of Ti3SiC2, which resulted in the formation of the unique morphology.