In previous studies of graphite/graphene and silicon NP sublimation, we also observed sublimation E a values well below the bulk ΔH sub values, particularly during the initial heat ramp, but in repeated ramps, the values increased, approaching the bulk values after the 2 nd or third heat ramp. The increases are believed to reflect an increase in the stability of the surface sites present on the NPs caused by annealing and selective sublimation of less stable low-coordination sites during repeated T NP ramps.