Study On The Synthesis And Performance Of Medium-range-ordered Nano-structures In Super-lubricating Amorphous Carbon Film

Hydrogenated amorphous carbon?a-C:H?films have attracted enormous attention as new solid lubricating materials due to their extremely high hardness,low friction,wear resistance and chemical inertness.However,the drawbacks,such as poor toughness,low carrying capacity and so on,have limited the service life and reliability of a-C:H films.In this study,we try to resolve these problems by designing and manipulating its medium-range ordered nanostructure.Based on the external-field-induced growth effect existing on the target surface during the unbalanced magnetron sputtering process,which reported by our previous research,the nickel target was chosen as catalyst and the fullerene-like nanostructure was controllably fabricated in the a-C:H films.The deposition parameters,such as ratio of the Ar/CH₄,surface morphology of the target and sputtering current were optimized,and the correlations between the medium-range ordered nanostructure and their mechanical and tribological properties were also investigated.The major conclusions of this study were drawn as follows:1.The appropriate Ar/CH₄ ratio can keep the target surface at the critical poisoning point,which ensures the external-field-induced growth effect can be achieved.Moreover,the catalytic efficiency was greatly improved by the nanonization of target surface.Furthermore,the damage to the precursor was decreased by lowering sputtering power during the sputtering process.By adjusting these deposition parameters,precursor with fully fullerene-onion nanostructure was successfully formed at the target surface.Then,the precursor was sputtered on the substrates forming curved fullerene-like nanostructure and amorphous carbon composite films.The study further validates the correctness of the external-field-induced growth effect and the general applicability of metal catalysts,and it also provides new idea and method to prepare the special medium-range ordered nanostructures in carbon-based films.2.The mechanical and tribological properties of the carbon-based films were greatly improved due to the formation of the fullerene-like structure.The film can retain wear lifetime of 1.5×10⁵ cycles at a high contact stress of 3.2 GPa.The fullerene-like nanostructure extends the planar sp²-coordinated carbon network with exceptional strength into the three dimensions,which results in an enhanced carbon network structure.It is proved that the mechanical properties of the toughness in the a-C:H film can be improved by adjusting the bond space structure,and provides a new idea for the improvement of the performance of carbon-based films.3.Special tribological experiments were designed by using the same pair under different contact modes.When steel ball sliding against a-C:H film coated on the steel disk,it is easy to form transferring film on the matching ball,and super low friction as low as 0.009 is obtained.When the a-C:H film coated on the steel ball sliding against steel disk,it is hard to form transferring film on the steel disk,and the friction coefficient is high?0.362?.It is proved that the formation of the transfer film is a necessary condition for a-C:H film to achieve super-lubrication performance.