As noted, ultra-high temperature ceramics are compounds like carbides, thus to understand surface chemistry of a material like SiC, it is necessary to understand the surface chemistry of hot nano-structured carbon, silicon, SiOx, as well as SiC, itself. For carbon, we studied sublimation kinetics for graphitic NPs, and oxidation kinetics for NPs with graphite, graphene, graphene oxide, diamond, carbon black, and carbon nano-onion initial structure, for TNP from 1200 to 2000 K. Carbon NPs were observed to passivate by isomerization to form surfaces with very low densities of under-coordinated reactive sites, tentatively attributed to nano-onion (fullerene-like) structures. In many cases, this transformation was not smooth, as shown by order of magnitude fluctuations in etching efficiency (EEO2). When passivated, carbon NPs had etching efficiencies (EEO2) roughly three orders of magnitude lower than the initial EEO2 for black carbon NPs.