High Temperature Reaction of Individual Graphite Nanoparticles with N2O: Etching, Passivation, Sublimation, and Comparison to O2

Abstract

High temperature oxidation kinetics, nanoparticles, Graphite, N2O, sublimation ABSTRACT The kinetics sublimation and for reaction of individual graphite nanoparticles (NPs) with N2O were studied over the 1600 to 1900 K temperature range. Reaction with N2O etched the NP surfaces at rates that increased with temperature and were linear with N2O pressure. The etching efficiency was two orders of magnitude lower for N2O compared to O2 at 1600 K, and one order of magnitude lower at 1900 K. The etching and sublimation kinetics were followed over time as the NPs lost up to ~40% of their initial masses. Sublimation gradually slowed over time, as expected because mass tends to be lost from the least stable surface sites, increasing the average stability of the remaining sites. O2 etching also slowed over time, but N2O etching rates initially increased. This observation indicates that N2O dissociative adsorption can occur at surface sites different from those that dominate the kinetics for O2 dissociative adsorption or sublimation. At long reaction times, the NPs passivated against further N2O attack even at 1800 K, indicating transformation of the surface layer to a structure with few under-coordinated reactive sites.