Fabrication And Tribological Performance Of Graphene Coating Prepared By Electrophoretic Deposition

Graphene,a two-dimensional(2D)material,could be regarded as a monolayer of carbon atoms tightly packed into honeycomb lattice.Moreover,graphene has great potential to be utilized as a solid lubricant at engineering scale due to its low interlayer shear strength revealed by recent studies.Most of the researches on tribological performances of graphene are at nano/micro scale,there are few studies on the application of graphene coating as solid lubricant at macro/engineering scale.Conventional methods for preparing graphene films such as mechanical exfoliation,chemical vapor deposition,are not suitable for depositing graphene coating as macroscopic friction reducing material.Based on that,this paper reports the fabrication and tribological performance of the graphene coating which is utilized as a solid lubricant at engineering scale prepared by electrophoretic deposition(EPD)and mussel adhesive protein is introduced to prepared a composite film to improve the interfacial strength between graphene and substrate.The major contents in this paper can be concluded as follows:(1)Preparation of graphene coating by electrophoretic deposition.Graphene coating was successfully prepared on some common substrates by electrophoretic deposition,such as silicon,cemented carbide,stainless steel,titanium alloy.The influence of the dispersion and modification of graphene nanosheets,deposition parameters and substrates on the coverage rate and morphologies of graphene coating were studied to prepare a uniform and thickness-controllable graphene coating,which could provide theoretical foundation for the preparation of graphene coating as macroscopic friction reducing material.(2)Study on the tribological performance of graphene coating prepared by EPD.To examine the friction and wear performance of these graphene coatings,a series of ball-on-plate reciprocating friction tests on a homemade tribotester are conducted on graphene coatings deposited on silicon wafer.Results showed that graphene coating can efficiently reduce the friction coefficient of different substrates to 0.1.Studies reveals that the influence of surface morphology,coverage rate,thickness,microstructure and substrate of graphene films on its tribological performances.Moreover,the friction reducing mechanism of EPD prepared graphene coating at macro scale is elucidated,which provides a theoretical and experimental basis for regulating the tribological performances of graphene coating as solid lubricant.(3)Preparation and tribological performance of graphene coating based on mussel adhesive protein.In order to improve the interfacial strength between graphene coating and substrate,mussel adhesive protein(MAP)was introduced as the intermediate layer.A layer of mussel adhesive protein was adhered to the substrate by immersing,followed by preparing graphene coating by electrophoretic deposition to obtain a graphene/MAP composite coating.Raman and FTIR were used to characterize the connection mechanism within the composite film.Results of friction tests indicates that MAP can efficiently prolong the lifetime of graphene coating.It is preliminarily verified that graphene coating has broad application prospect as macroscopic solid lubricant.