Super low to high friction of turbostratic graphite under various atmospheric test conditions

Mechanism behind manifestation of high and super low values of friction coefficients in turbostratic graphite during tribology tests carried out under nitrogen and argon exposures is investigated. Super low value in argon environment is attributed to self-organization and superficial mobility of crystallites at contact interface whereas similar tests under nitrogen atmosphere revealed high friction due to accumulation of dangling bonds generated by fractured surfaces. In ambient atmospheric conditions, coefficient of friction is found to systematically decrease with increase in relative humidity. Increase in relative humidity provides passivation of interacting dangling bonds on the sliding surface.