ECR Ion Irradiation Can Control The Nanostructured Carbon Film And Its Friction Characteristics

With the development of mechanical engineering technology,The machine parts with wear resistance and low friction characteristics were highly required,and nano-surface coating technology is the most simple and direct way to change the surface properties,which can further improve the tribological properties,and maintain the high toughness.As a protective and functional surface,nano-surface coating technology has become a hot research field.Graphene has been proved to be a fantastic solid lubricant material.When the carbon films were embedded with graphene nanocrystals,the nanostructure of graphene nanocrystals would significantly affect on the tribological behavior of the film.Therefore,very low friction could be expected by adjusting the structure of graphene nanocrystals in the film.Based on these backgrounds,The studies on “Controllable Fabrication and Tribological Properties of nanostructured Carbon Films with ECR Ion Irradiation” was carried out in this paper.In this study,the carbon films were prepared by using ion irradiation in electron cyclotron resonance(ECR)plasma with divergent magnetic field.Firstly,the substrate bias voltage,microwave power and working gas pressure were used to control the energy and density of ion irradiation.The plasma was diagnosed with Langmuir probe.The results show the ion irradiation energy increased with the increasing of substrate bias,but the ion irradiation density increased with the increasing of power.Then,carbon films were prepared by adjusting the ion irradiation energy and density.The nanocrystalline size and surface roughness in the carbon films were characterized by Transmission Electron Microscopy(TEM),Raman spectroscopy and Atomic Force Microscopy(AFM).The experimental results show that graphene nanocrystalline was formed in the carbon films with ion irradiation.The increase of the ion irradiation density and the decrease of the ion irradiation energy can cause the grain size of the graphene nanocrystalline in the carbon film to become larger.The surface of the carbon film is smooth and the surface roughness barely changed with the irradiation energy and density,which is about 0.1nm.Finally,the frictional property of carbon films were evaluated by pin-on-disk tribotest.The friction coefficient of the carbon films ranged from 0.07 to 0.13.And the friction coefficient decreased as the grain size of graphene nanocrystalline increases.The graphene nanocrystalline carbon film exhibits good wear resistance,and the wear life is over 10,000 cycles.In order to elucidate the friction mechanism of the graphene nanocrystalline carbon film,the surfaces of the carbon film and the Si3N4 ball sphere were characterized by high resolution metallographic microscope and Raman spectroscopy.It is clarified that the low friction mechanism of graphene nanocrystalline carbon film is ascribed the formation of to a graphene nanocrystalline transfer film with grain size about 3 nm at contact interface,and the decreased of contact area to reduce the interfacial shear strength..