Because 1200 and 1300 K are well below Tmelt for silica (~1986 K) and silicon (1683 K), the O2 etching experiments shown above are primarily sensitive to the reactivity of the NP surface layers. We previously studied sublimation and O2 etching of elemental Si NPs, with one experiment on a SiC NP also reported. Because of the many similarities, it is useful to consider etching of pre-heated silica NPs in light of mechanisms developed for silicon oxidative etching, which has been studied both for Si NPs and for well-characterized bulk Si surfaces. This chemistry has been well studied because of the importance of etching vs. oxide growth in semiconductor applications, and because it determines the performance of Si-containing high temperature materials exposed to oxygen.