Experimental and model studies about the lubrication of physisorbed isobutane molecules on hydrogenated diamond-like carbon films

As one amorphous carbon consisting of sp(2) and sp(3) bonding, diamond-like carbon (DLC) films present excellent tribological characteristics. Meanwhile, frictional properties could present great complexity with the varied interaction. In this work, research on the tribological performances of hydrogenated DLC films under the various isobutane conditions, which was similar to some polar fluids, was carried out. The results showed that friction coefficient increased with the isobutane amount. And the wear was constant after a certain amount of isobutane was adsorbed. Combining these experimental results with models, the mechanism has been proposed. It was the isobutane molecules physisorbed on the interface that prevented the hydrogenated DLC films from wear, resulting in the increasing of friction coefficient with gas pressure.