Carbon nanoparticles and carbon films, such as diamond and graphite-like carbons, are making new inroads into lubrication applications. The carbon-based nanoparticles are heat resistant, radiation hard, and durable and provide low coefficient of friction (CoF) with a number of tribocouples. A careful examination of the internal structure of the carbon materials reveals that the nanostructure is highly variable and depends upon the starting material and processing conditions-which is also true of carbon black. The significance with respect to oxidation of the internal structure of carbon is its effect upon reactivity. Graphitic carbon is characterized by layer planes with large in-plane dimensions. The connection between layer plane dimensions and oxidation is due to the anisotropic reactivity of the graphitic segments comprising carbon. Carbon atoms within basal plane sites, surrounded by other carbon atoms, exhibit a far lower oxidative reactivity than those located at the periphery of such segments.
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