Unveiling the secrets of the nickel-metal/alumina-ceramic interface during stretching: atomic and electronic insights

It is both great scientific and practical importance to explore the metal-ceramic interface properties at the atomic and electronic levels. In this paper, the bonding properties and failure mechanism of Ni (111)-Al2O3 (0001) interface with 1Al-, 2Al-and O-terminated have been comprehensively investigated by using the first-principles calculations. First, the size order of the three kinds of Ni-Al2O3 interface for work of adhesion (W-ad) is O-terminated (6.59 J/m(2)) > 2Al-terminated (3.26 J/m(2)) > 1Al-terminated (1.25 J/m(2)). In contrast, the O-terminated Ni-Al2O3 interface structure exhibits excellent stability. Second, the result of tensile test show the maximum tensile stress of 1Al-, 2Al- and O-terminated Ni-Al2O3 interface structures are 17.44, 23.10 and 32.59 GPa, respectively. Simultaneously, the critical strain of O-terminated Ni-Al2O3 interface are 2 and 1.5 times larger, respectively, than 1Al- and 2Al-terminated. The results demonstrate that the strength and plasticity of the O-terminated Ni-Al2O3 interface are significantly superior to that of Al-terminated one. Interestingly, the O-terminated Ni-Al2O3 interface structure presents the phenomenon of fluctuation up and down in stress during stretching compared to Al-terminated interface, which is a microscopic manifestation of atomic migration and recombination at the interface. Further investigation reveal that the stretching induces lattice distortion at the O-terminated Ni-Al2O3 interface, thus resulting in a toughening effect. Third, the results of electronic analysis show that the greater the charge density at the interface, the greater the bonding strength. Especially important, the electrons will transfer and redistribute at the interface during stretching process, and the failure will occur at the position where the electrons will be exhausted first. Here, the Al-terminated Ni-Al2O3 structure failure position occurs exactly at the interface and the O-terminated occurs at the non-interface. Therefore, preparing the O-terminated Ni-Al2O3 interface in practical applications will help to extend the service life of the ceramic/metal structure.