The electronic theory study of the influence of Pd on the passivation of Ti alloys

Abstract

The electronic structure parameters of Ti alloys, such as density of states, Fermi energy level, environment-sensitive embedding energy etc, have been calculated by recursion method. The larger environment-sensitive embedding energy of Pd in the bulk of Ti alloy than that on the surface of Ti alloy indicates that Pd is apt to segregate on the surface. The negative formation energy of Pd clusters suggests that the distribution of Pd atoms on the surface of Ti alloy is in the form of atom clusters. The range of the local density of states of Pd is narrow, while that of Ti is wide. So a peak appears in the total density of states of Ti alloys between -20 and -15 eV. This peak has a significant effect on the Fermi level. It makes the Fermi energy of the surface Ti alloys with more Pd atoms low. So the microcells form between the area with more Pd atoms and the area with fewer or without Pd atoms on the surface of Ti alloys. Ti dissolves preferentially in the corrosive media. This leads to form a layer of Pd atomic clusters on Ti alloy surface. The Pd atomic layer serves as the electrocatalytic surface, facilitating the passivation of Ti alloys and improving the corrosion resistance.