Phase evolution and reaction mechanism during synthesis of Ti3SiC2 from Ti-Si-C and Ti-SiC-C systems

The formation mechanism of Ti3SiC2 has been revealed by investigating the phase evolution of Ti-Si-C and Ti-SiC-C systems with elevated temperature through quantitative XRD analysis, microstructure characterization and thermal analysis. It is found that the synthesis process involves two stages: the formation of intermediate phases in stage I and their transformation into Ti3SiC2 in stage II. For both systems, the intermediate phases are Ti5Si3Cx, TiC, and TiSi2. Stage I of the Ti-Si-C system is controlled by reaction rate, while the counterpart of Ti-SiC-C is controlled by atom diffusion. The stages II of the two systems are similar: Ti5Si3Cx reacts with TiC to form Ti3SiC2 and TiSi2 at 1200 degrees C, while Ti3SiC2 and silicon are obtained from the reaction between TiSi2 and TiC after 1400 degrees C. Besides, silicon can evaporate from the system, resulting in residual TiC in the final product. It is confirmed that sufficient diffusion of the elements and maintaining the content of silicon in the system were conducive to the synthesis of Ti3SiC2.