Theoretical prediction of mechanical and thermodynamic properties of TiMC2 (M = Hf, Mo, Nb and W) ceramics: Very promising excellent TiC - based solid solution materials

Abstract

The mechanical and thermodynamic properties of TiMC2 (M = Hf, Mo, Nb and W) ceramics are investigated by the first-principles method based on density-functional theory (DFT). Meanwhile, the investigation of TiC ceramics is also carried out to verify the reliability of the calculation in this study. The results show that TiMC2 ceramics have good thermodynamic stability and possess the characteristics of advanced ceramic materials. Except for TiHfC2 ceramics, the elastic properties and melting temperature of TiMoC2, TiNbC2 and TiWC2 ceramics are significantly higher than those of TiC ceramics. Especially TiWC2 ceramics, its elastic constant C11 is as high as 732.3GPa, and its melting temperature is as high as 4581 K, which may be the highest melting temperature found in the world. TiMC2 ceramics belong to the brittle materials family, and the ductility of TiHfC2, TiNbC2 and TiWC2 ceramics is only weakly lower than that of TiC ceramics, while the ductility of TiMoC2 ceramics is significantly better than that of TiC ceramics. TiHfC2, TiMoC2, TiNbC2 and TiWC2 ceramics exhibit normal thermal expansion behavior at 0–1590 K, 0–1510 K, 0–1820 K and 0–1950 K, respectively, and the thermal expansion rate follows the order: TiMoC2>TiHfC2>TiWC2>TiNbC2, and TiMC2 ceramics belong to the medium expansion materials. The phonon thermal conductivity of TiC ceramics is always lower than that of TiNbC2 ceramics, but higher than that of TiWC2, TiMoC2 and TiHfC2 ceramics, indicating that the doping of Nb element can increases the phonon thermal conductivity of TiC ceramics, while the doping of Hf, Mo and W elements reduces the phonon thermal conductivity of TiC ceramics. By studying the elastic and thermodynamic properties of TiMC2 (M = Hf, Mo, Nb and W) ceramics, a theoretical reference is provided for its application in many fields.