Exploring the structural, mechanical and thermodynamic properties of layered Ta3AlC2-type MAX ceramics for ultrahigh-temperature applications

Abstract

Ta₃AlC₂-type MAX carbides with a layer structure are considered promising candidates for ultrahigh-temperature ceramics due to their unique structure features: the M-C layer contributes high melting point and mechanical strength, while the M-Al layer forms a protective antioxidant layer. However, the dynamical stability and overall properties of these Ta₃AlC₂-type MAX ceramics are unknown. A key challenge, therefore, lies in identifying novel MAX ceramics with excellent comprehensive properties to meet the demands of advancing ultrahigh-temperature industries. To solve these problems, the phase stability, elastic modulus, hardness, elastic anisotropy, and thermodynamic properties of six TM₃AlC₂ ceramics are systematically studied using first-principles calculations. The results reveal that three new TM₃AlC₂ ceramics: V₃AlC₂, Cr₃AlC₂ and Nb₃AlC₂ are firstly predicted. Importantly, the calculated bulk modulus of Ta₃AlC₂ is bigger than that of Cr₂AlC and Mo₂AlC. In particular, V₃AlC₂ exhibits the highest elastic modulus among all the studied TM₃AlC₂ ceramics. Naturally, the high elastic modulus of these carbides is determined by their TM-C-TM-Al layered structure, particularly the cohesive forces between the TM-C layer and TM-Al layer, as reflected by the TM-C bond in TM-C layer and TM-Al bond in TM-Al layer. Finally, the Debye temperature follows the order of V₃AlC₂>Ta₃AlC₂>Cr₃AlC₂>Nb₃AlC₂>Hf₃AlC₂>Zr₃AlC₂. Therefore, this study provides new insight into the structural feature and overall properties of TM₃AlC₂ MAX ceramics and opens up a promising avenue for seeking the novel TM₃AlC₂ MAX ceramics suitable for various ultrahigh temperature industries.