Combined influence of an inert gas environment and a mechanical action on a graphite surface

The adsorption and reactivity properties of graphite wear fragments produced in a tribocontact depend on the gaseous environment surrounding the contact which conditions the type of wear (fatigue or abrasive wear) and the surface reactivity. The determination of the specific area of the wear fragments, using a nitrogen adsorption method (Brunauer, Emett and Teller method), permits one to describe the surface structure. We carried out on a pin on disk tribometer located in a vacuum chamber wear experiments on two samples of polycrystalline graphites, under different inert gaseous environments. We observed that the size of wear fragments (and the friction coefficient) mainly depends on the orientation of the crystallites. This mechanical phenomenon principally depends on the nature of the environment and on the nature of the environment and on the normal load. Depending on these conditions, the powder can have different colorations, and its specific area shows variations from 140 m exp 2 g exp -1 to 285 m exp 2 g exp -1 . Wear particles produced under inert environment present many active sites (edge sites) but their reactivity depends on their size and specific area. The most reactive can exhibit pyrophoric properties, when exposed to the ambient air.