Surface transformation and interactions of iron oxide in glassy lubricant: An ab initio study

Abstract

Density functional theory (DFT) calculation for full coverage (NaPO3)x glass on Fe2O3 (0001) surface, and ab initio molecular dynamics (AIMD) simulation for phosphate and iron/iron oxide clusters at high temperature in hot rolling of steel have been carried out to investigate the transformation of adsorbed oxide surface and the interaction of the oxide compound in the glass network. Among three main interlayer interactions, Fe-Oglass is the most dominant bond in the system with effect of weakening oxide surface topmost Fe-O bond. Osurface-P can be observed under compression conditions and Fe-P direct bonds occur in the combination of elevated temperatures, high exposure of iron and appearance of under-coordinated phosphorus. Fe atoms in Fe-P change their valence state adapting to the synergetic bonding. Na atoms from the glass network also play an important role in promoting the iron oxide deformation by generating O-terminated surfaces and reducing Fe-Osurface stability, even at normal temperatures.