Tribo-Electromagnetic Phenomena of Hydrogenated Carbon Films—Tribo-Electrons, -Ions, -Photons, and -Charging

Triboemission of negatively charged particles and positively charged particles, tribo-charging and friction coefficient were measured simultaneously using a frictional system with diamond sliding on hydrogenated carbon films in ambient air. The hydrogen content of the carbon films varied from 0 to 43 at. percent. All the carbon films tested emitted both negatively and positively charged particles during sliding. For films with hydrogen content of from 0 to 15 at. percent, neither tribo-charging nor tribo-photons were observed; beyond 15 at. percent hydrogen content, tribo-charging and tribo-photons were observed. With increasing hydrogen content, the emission intensity of the negatively and positively charged particles, photons and tribo-charging increased. It is concluded that a micro-plasma state is formed at the frictional contacts of diamonds sliding on hydrogenated carbon films.