Theoretical prediction of mechanical, thermodynamic, and surface oxygen adsorption properties of anti-perovskite Ti3AC (A = Tl and Al) ceramics for thermal barrier coating materials

Abstract

Based on first principles, the mechanical, thermodynamic, and surface oxygen adsorption properties of Ti3AC (A = Tl and Al) ceramics are investigated. The mechanical parameters of Ti3AlC ceramics can well reproduce other theoretical and experimental data. The negative formation enthalpy and lattice dynamics characteristics indicate that Ti3AC ceramics are thermodynamically stable. At 0 K, the mechanical strength of Ti3TlC ceramics is always smaller than that of Ti3AlC ceramics, but its ductility is better than Ti3AlC ceramics. Ti3TlC and Ti3AlC ceramics have normal thermal expansion behavior at 0–1800 K, and belong to high and medium expansion materials, respectively. The thermal expansion coefficient of Ti3TlC ceramics increases with increasing temperature. However, an important discovery is that Ti3AlC ceramics have an inhibitory thermal expansion behavior at high temperatures. At 300–1800 K, the Grüneisen constant of Ti3TlC ceramics is 1.55–1.78 and that of Ti3AlC ceramics is 1.49–1.54. At 0–1800 K, the phonon thermal conductivity of Ti3TlC is always smaller than that of Ti3AlC. At a high temperature of 1800 K, the thermal conductivity of Ti3TlC and Ti3AlC ceramics is 13.42 and 33.27 W m−1 K−1, respectively. The most sensitive adsorption site of O on Ti3TlC (100) ceramic surfaces is at the top site, while the most sensitive adsorption site on Ti3AlC (100) ceramic surfaces is at the hollow site. Moreover, the Debye temperature, melting point, and hardness of Ti3AC ceramics are also investigated.