| Diamond-like carbon?DLC?films are considered to be the most promising artificial joint surface modified materials because of good wear resistance,chemical inertness and good biocompatibility.However,large residual stress lead to the failure of film-substrate adhesion,limiting its application.The residual stress of the DLC film can be reduced and the film-substrate adhesion can be improved by doping non-carbide metal.Silver-doped DLC?Ag-DLC?films have great potential applications in the surface modification of artificial joints because of their good biocompatibility and antibacterial properties.In this thesis,high power pulsed magnetron sputtering?HPPMS?technology was used to adjust the microstructure of DLC films by adjusting the flow rate of Ar-to-C2H2,the mechanical properties of DLC films were optimized.Ag-DLC thin films were prepared by inlaying Ag rods on graphite targets.The discharge state of target was analyzed by monitoring the target voltage,current and the plasma.The microstructure and mechanical properties of the film were evaluated.Finally,by comparing the wear resistance of DLC films and Ag-DLC films,the different friction mechanisms of DLC films and Ag-DLC films were revealed.The results were shown as followed:?1?The DLC films were prepared by adjusting the flow rate of Ar gas.As the Ar flow rate increases,the deposition rate and the surface roughness of the DLC film decrease.And the compressive stress and hardness of the DLC film increase.?2?The Ag-DLC films were prepared by adjusting the flow rate of Ar gas.As the flow rate of Ar gas increased,the deposition rate of Ag-DLC film decreased gradually,but there was no significant difference in microhardness and wear resistance between each samples.When the flow rate of Ar gas exceeded 20 sccm,the film appeared graphitization and the stress gradually decreased.When the flow rate of C2H2 was 5 sccm,the degree of target poisoning could not be changed by adjusting the flow rate of Ar gas,so the sputtering yield of the target elements did not changed,and the Ag content in the Ag-DLC film remains basically constant?about 50 at.%?.?3?The DLC and Ag-DLC films were prepared by adjusting the ratio of Ar/C2H2.With the increase of C2H2 ratio,the deposition rate of DLC films and Ag-DLC films increased,the content of C-C sp3 bonds decreased,the stress and hardness of films decreased.The Ag content in the Ag-DLC film gradually decreased.The stress,hardness and wear resistance of the DLC films could be enhanced by doping relatively low silver content.In air environment,the wear rate of Ag-DLC film decreased with the increase of Ag content.The wear rate of Ag-DLC film with 2.99 at.%Ag was the lowest which was about 7×10-17 m3/N.m.Ag-rich"rod-shape wear products"with anti-friction effect were found at the wear track of the Ag-DLC film and at the Al2O3 wear spots. |
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