The structural components of a very High Temperature Reactor (VHTR) are exposed to trace amounts of gaseous elements and moisture. These impurities can adversely affect the integrity of the reactor structural components. Among the impurity gases, carbon-bearing gases – methane, carbon monoxide and carbon dioxide – have significant detrimental effects on the protective oxide scales, which grow on nickel-based alloy surfaces, leading to carburization of the alloy.
In this work, we investigate the effect of carburizing gases on the stability of chromium oxide scales using electronic structure simulations. We have utilized Kohn-Sham density functional theory (DFT) as implemented in the Vienna ab initio simulation package (VASP) with the generalized gradient approximation; to describe the strong correlations between the d electrons of chromium, we have utilized the DFT+U approach. The molecular structure of the oxide surface without the gases is first optimized structurally. Fully relaxed carburizing gases are then allowed to be adsorbed on to the surface. We finally employ ab initio molecular dynamics (AIMD) simulations at high temperatures (up to 1200 K) to calculate the structural and dynamic properties of the interface, and to elucidate the mechanisms of thermal stability of the interface region at different temperatures and impurity coverage of the surface.
 Young, D. J. and J. Zhang (2018). "Alloy Corrosion by Hot CO2 Gases." JOM 70 (8): 1493-1501.
 Funk, S., T. Nurkic, B. Hokkanen and U. Burghaus (2007). "CO2 adsorption on Cr(110) and Cr2O3(0001)/Cr(110)." Applied Surface Science 253 (17): 7108-7114.
5:00 PM–7:00 PM Apr 23, 2019 (US - Arizona)
PCC North, 300 Level, Exhibit Hall C-E