Corrosion of Si, C, and SiC in molten salt

TL;DR

This study investigates the corrosion mechanisms of silicon, carbon, and silicon carbide in molten fluoride salt using ab initio molecular dynamics, revealing dissolution behaviors and proposing suppression strategies for SiC corrosion.

Contribution

It provides new insights into the atomic-level corrosion processes of Si, C, and SiC in molten salt and suggests Be doping as a potential mitigation method.

Findings

Si has a lower dissolution potential than C, indicating easier corrosion.

Dissolved Si forms SiF6^{2-} ions, while C forms neutral CF4 molecules.

A swapping mechanism initiates corrosion, with Si migrating to the surface before dissolving.

Abstract

Corrosion of Si, C, and SiC in fluoride salt has been studied by ab initio molecular dynamics. The standard dissolution potential for Si is found to be smaller (easier to corrode) than that of C. The dissolved Si attracts F- ions and forms SiF62-, whereas the dissolved C species forms neutral CF4 molecules. A swapping mechanism is identified for the initial corrosion stage, where Si first comes to the surface and then is dissolved, leaving behind chain- and ring-like C structures. A strategy to suppress SiC corrosion is also discussed based on Be doping, including avoiding Be2C formation.