First-Principles Study Of Ni/Al₂O₃ Interface

When we study the subjects of ceramic brazing, diffusion bonding and wetting, we frequently encountered the structure of metal/ceramic interface. But because of the complexity the interface of solid-solid, the study of solid-solid interface to microscopic mechanism is of great difficulty. The paper use the first principles to study the interface of Ni/Al2O3, which is often realized in the field of metal-ceramic interface structure. the matching relations of Ni/Al2O3 interface, stability, the interface bonding strength and electronic structure of interface atoms will be researched, to understand the bonding mechanism in the welding process and provide theoretical basis to solve related problemsFirst we calculate the Ni block, α-Al2O3 and their surface electronic structural characteristics and stability, etc. Results show that Ni block is metal crystal, among several low index surfaces Ni(111) surface is the most stable. O and Al in the α-Al2O3 is combined by ionic bonds, among all the surface of α-Al2O3(0001) Al-monolayer surface has the least surface energy.State density analysis shows that the surface effect is mainly caused by the outermost atomic, smaller influence on inner atoms.Second studied several different matching of Ni(111)/α-Al2O3(0001) interface model, the results show that the M2 interface structure is not stable, oxygen terminal interface can the larger absolute value of interface dissociation energy and interface adsorption energy than aluminum terminal interface, and M1(O) interface structure is the most stable. The analysis of M1(O) charge density difference realize that a large number of electronic transfer from Al around to O around, and form ionic bonds, making the interface with high strength.According to the interface state density diagram analysis for the effect of interface to atoms around the interface, inner atoms is less affected by the interface, and electron transfer occurs mainly between atoms near the interface.In α-Al2O3(0001) surface we make dewetting experiments with two kinds of thickness of the nickel film(2nm and 30nm), then there is nearly spherical polyhedron Ni single crystal. and as nickel film is thicker, the diameter of Ni single crystal is larger. TEM analysis indicates that the actual combination of interface is Ni(111)/ α-Al2O3(0001), and the interface matching is [11?0]Ni‖[21?1?0]Al2O3 which meets well with the theoretical computing results.