In-situ Growth Mechanism And Tribological Properties Of Amorphous Carbon-based Coatings On Polymer Materials

Polymer materials are widely used contributes to their excellent toughness,corrosion-resistance and biocompatibility.However,some inherent drawbacks such as low hardness and poor wearresistance,cannot be ignored,greatly limiting the industrial applications of polymer materials in some particular domains.Researches showed that the hardness and tribological properties of polymer materials can be effectively improved by growing a layer of amorphous carbon-based coating on the surface.However,the growth of amorphous carbon-based coatings on polymers is confronted with the challenge of poor adhesive strength.Although there are some researches on the application of amorphous carbon-based coatings on polymer materials,but few on the growth mechanism,adhesive mechanism and tribological mechanism.In this paper,the plasma-induced insitu growth method was first proposed for the preparation of amorphous carbon-based coatings on polymer materials,the in-situ growth mechanism,adhesive mechanism and tribological mechanism of amorphous carbon-based coatings on polymer materials were analyzed and presented.(1)Amorphous carbon(a-C)coatings with different thickness were in-situ grown on the surface of ethylene-propylene copolymer(EPC)substrates via the continuous treatment of carbon plasma for different times.Results showed that with the continuous carbon plasma treatment,complicated chemical reactions occurred on the surface of EPC substrates,which induced an in-situ transformation from organic carbon structures to inorganic carbon structures on the substrates surface,resulting the formation of in-situ transition layer of the crosslinked network structures including organic polymer carbonaceous chains and inorganic amorphous carbonaceous chains.The a-C coating in-situ grown on polymer substrate composing of the in-situ transition layer and the pure a-C layer epitaxial grown upon the in-situ transition layer.The in-situ growth mechanism of a-C coating on polymer substrates was analyzed and presented.(2)The indentation,scratch,and tribological tests of the a-C coatings on EPC substrates were performed.Results showed that the a-C coatings exhibit reliable adhesive strength on the surface of EPC substrates,and the tribological properties of EPC substrates significantly improved with the continuous treatment of carbon plasma.Furthermore,the possible tribological mechanism of a-C coatings on polymer substrates were analyzed and presented.(3)Pure a-C coating,chromium-doped composite amorphous carbon(a-C/Cr)coating and silicon-doped composite amorphous carbon(a-C/Si)coating were in-situ grown on the Polycarbonate(PC)substrates.Results showed that hardness and tribological properties of the substrates were significantly improved by in-situ growing amorphous carbon-based coatings on the surface.The tribological tests were performed under two different normal loads,the tribological mechanism of the pure a-C coating and the doped composite amorphous carbon-based coatings were analyzed by the Raman characterization of the wear tracks before and after the tribological tests.