Improvement of mechanical and tribological performances of carbon nanostructure films by cryogenic treatment

The work presents data on mechanical properties, tribological performances and microstructure changes of hydrogenated amorphous, fullerene-like and graphite-like carbon films (a-C:H, FL-C:H and GL-C:H) after post cryogenic treatment. It is shown that post cryogenic treatment more effectively improves the mechanical and tribological performances of carbon nanostructure films as compared to the a-C:H films. By the combination of Raman and TEM studies, the performance improvement can be attributed to the introduction and enhancement of defects such as pentatomic and heptatomic carbon rings in their carbon structure matrices, which facilitate cross-linking between the graphitic basal planes via sp(3)-hybridized carbons. The results provide an important reference for achieving solid lubrication under the cryogenic environment that is both reliable and presents longevity.