Effect of Ge on microstructure and mechanical properties of Ti3SiC2/Al2O3 composites

Owing to the good physicochemical compatibility and complementary mechanical properties of Ti3SiC2 and Al2O3, Ti3SiC2/Al2O3 composites are considered as ideal structural materials. However, TiC and TiSi2 typically coexist during the synthesis of Ti3SiC2/Al2O3 composites through an in-situ reaction, which adversely affects the mechanical properties of the resulting composites. In this study, Ti3SiC2/Al2O3 composites were prepared via in situ hot pressing sintering at 1450 degrees C. Ge, which was used as a sintering aid, improved the purity and mechanical properties of the Ti3SiC2/Al2O3 composites. This is because Ge replaced some of the Si atoms to compensate the evaporation loss of Si to form Ti-3(Si1-xGex)C-2, which showed a crystal structure similar to that of Ti3SiC2. Furthermore, the molten Ge accelerated the diffusion reaction of the raw materials, increasing the overall density of the Ti3SiC2/Al2O3 composites. The optimum Ge amount for improving the mechanical properties of the composites was found to be 0.3 mol. The flexural strength, fracture toughness, and microhardness of the composite with the optimum Ge amount were 640.2 MPa, 6.57 MPa m1/2, and 16.21 GPa, respectively. The formation of Ti-3(Si1-xGex)C-2 was confirmed by carrying out X-ray diffraction, energy dispersive spectroscopy, and transmission electron microscopy analyses. A model crystal structure of Ti-3(Si1-xGex)C-2 doped with 0.3 mol Ge was established by calculating the solid solubility of Ge.

Automated summary

In this study, Ti3SiC2/Al2O3 composites were prepared using Ge as a sintering aid, which improved the purity and mechanical properties of the composites. The optimal amount of Ge was found to be 0.3 mol, resulting in composites with high flexural strength, fracture toughness, and microhardness. The formation of Ti-3(Si1-xGex)C-2 was confirmed through various analyses, and a model crystal structure was established with the calculated solid solubility of Ge.