Fe/Cu doped black ceramic coating on magnesium alloy by plasma electrolytic oxidation method based on first principles

Abstract

The absorption of visible light by a solid material can correspond to its color. If all visible light is absorbed, the material is black, and the band width of the material defines the wave limit of visible light absorption. Based on this, the transition metal elements Fe and Cu were chosen to dope MgO, and the transition metal elements Fe or Cu were substituted to dope MgO using first-principles simulation. The doped elements' 3d and 4 s levels were introduced to shift the locations of MgO's valence and conduction bands, respectively, lowering the band gap width of MgO. The MgO ceramic coating may respond to light wave wavelength redshifting to 780 nm and entirely absorb visible light; The black MgO ceramic coating was prepared on the surface of AZ31 magnesium alloy utilizing Fe salt and Cu salt as plasma electrolytic oxidation (PEO) electrolyte additions, and the visible light absorption rates were 94.2 % and 94.1 %, respectively. The test findings show that the band gap of the MgO ceramic coating has been lowered from 4.97 eV to 1.58 eV and 1.60 eV, respectively, which is the primary reason for the achievement of strong absorption in all visible light bands. The first principle calculation of the influence of doping elements on the band gap of MgO ceramic coating can serve as a theoretical guidance for selecting coloring elements for the fabrication of black ceramic coating.