Elemental gradient potential trap strategy for enhancing corrosion resistance of SiC in oxygenated and oxygen-free lead-bismuth corrosion

Abstract

SiC is a promising candidate for producing corrosion-resistant lead–bismuth cladding material for application in lead-cooled fast reactors because of its excellent properties, including high resistance to oxidation and thermal shock, high thermal conductivity, and low thermal expansion in flowing lead–bismuth material. The present study revealed the following. First, the binding behavior of Pb/Bi material on its free surface is mainly influenced by the shell energy; in the bulk, the core energy plays a larger role. Second, at the free surface of SiC, Si atoms partially lose their coordination and accumulate an electron energy of approximately 1.3 eV, leading to a 0.74 % decrease in the length of the Si–C bond, which enhances the local binding strength. By contrast, exposure of the C layer results in a loss of approximately 0.5 eV in the electron energy, which causes a 4.81 % contraction of the length of the Si–C bond. The charge depletion in the Si layer and bond contraction in the C layer contribute synergistically to corrosion resistance. Third, a gradient effect exists between the free surface and the bulk; surface elements tend to repel Pb/Bi, whereas bulk elements can either attract or repel Pb/Bi. Gradient doping at the free surface and in the bulk regions reduces Pb/Bi adsorption on the surface and modulates the Pb/Bi binding energy in the bulk, improving the overall corrosion resistance of SiC. This study provides essential theoretical support for the application of SiC as a cladding material in generation IV lead-cooled fast reactors. The proposed elemental gradient potential trapping (EGPT) strategy enhances the corrosion and irradiation resistance of SiC, thereby improving its overall performance in high-temperature environments where both irradiation and corrosion occur.