Low friction of nitrogen-doped diamond-like carbon coating due to acidic liquid film and nitrogen-doped graphite oxide generated by dielectric barrier discharge in ambient air

This study investigated the low friction mechanism of nitrogen-doped tetrahedral amorphous carbon ( ta -CN x ) coatings using in-situ irradiation of dielectric barrier discharge (DBD) in ambient air. When the ta -CN x surface was irradiated with DBD, an acidic liquid film was produced, which was analyzed using liquid chromatography-mass spectrometry (LC/MS) to show that the liquid film contained nitric acid. Additionally, DBD-irradiated surfaces and wear track of low-friction surfaces (surface with friction coefficient reduced to 0.01) were analyzed using Raman, XAFS, and XPS, and the results consistently showed that DBD irradiation produced nitrogen-doped graphite oxide (N-GO) structures. The study conclusively demonstrated that the synergistic effect of the N-GO and the acidic liquid film is crucial for achieving low friction, with each component being indispensable for the effectiveness of the mechanism. This synergy highlights the potential of DBD irradiation as a novel approach for enhancing lubrication in ta -CN x coatings.