Research on the electronic properties of TiB2/γ-Fe(1 1 1) and TiB2/Ni(1 1 1) interfaces

In order to explore the interfacial bonding mechanisms of TiB₂/γ-Fe and TiB₂/Ni in the composites, the adhesion work, electronic properties and fracture toughness of the TiB₂(0 0 1)/ γ-Fe(1 1 1) and TiB₂(0 0 1)/Ni(1 1 1) interfaces were investigated using first-principles calculations. The results reveal that the surface energy of the TiB₂ surface at the B-terminated is the smallest and the constructed TiB₂(0 0 1)/ γ-Fe(1 1 1) interface has the largest adhesive energy. The electronic structures of the TiB₂(0 0 1)/γ-Fe(1 1 1) and TiB₂(0 0 1)/Ni(1 1 1) interfaces reveal that bonding at the interfaces is provided by the B-2p orbitals with the Fe-3d and Ni-3d orbitals, respectively, and that the formation of Fe-B and Ni-B covalent/ionic bonds is the main source of bonding and interaction. The bonding and strength of Fe-B in the TiB₂(0 0 1)/γ-Fe(1 1 1) interface is stronger than that in the TiB₂(0 0 1)/Ni(1 1 1) interface, which is due to the higher charge density accumulation of Fe atoms at the TiB₂(0 0 1)/γ-Fe(1 1 1) interface. Using Griffith’s theory, the TiB₂(0 0 1)/γ-Fe(1 1 1) interface is inferred to have the strongest fracture toughness. This study suggests that the chemical bonding stronger Fe-B bonds result in a high bond strength and a more stable interfacial structure at the TiB₂(0 0 1)/ γ-Fe(1 1 1) interface, leading to better resistance to cracking in practice.