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 Ti₅Si₃C_x, 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: Ti₅Si₃C_x reacts with TiC to form Ti₃SiC₂ and TiSi₂ at 1200 °C, while Ti₃SiC₂ and silicon are obtained from the reaction between TiSi₂ and TiC after 1400 °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.