Supercritical Double Pulse Electrodeposition Graphene Composite Coating Preparation And Performance Study

Graphene,with excellent physical and chemical properties,can be used as a reinforcement of metal matrix composites.Electrodeposition method has attracted wide attention due to its advantages in improving the interfacial bonding between the graphene and the matrix without destroying the structure of graphene.At present,most of the electrodeposition processes are carried out under normal conditions using direct current or single pulse current,which may result in agglomeration and uneven distribution of graphene in the matrix.In this paper,supercritical fluids assistant technology and pulse reverse electrodeposition technology were combined to solve the above problems.The research contents of nickel-based graphene(Ni-GO)composites prepared by pulse reverse electroplating under supercritical conditions are shown as follow:1.Study on process of pluse reverse electrodeposition under supercritical condition.Firstly,the influence order of four important parameters of pulse reverse power supply on the microhardness of composite coatings was obtained by orthogonal experiment:forward average current density>forward pulse duty cycle>reverse average current density>reverse pulse duty cycle.On this basis,according to the single factor experiments,the optimal process combination is determined as follow:the average forward current density is 6A/dm~2,the duty cycle of forward pulse is 0.25,the average reverse current density is 1.0A/dm~2,and the duty cycle of reverse pulse is 0.4.2.Study on properties and effects of graphene oxide(GO).The properties of GO nanosheets before and after electrodeposition were analyzed by using SEM,TEM,XRD,Raman spectroscopy and FTIR spectroscopy.The results show that GO nanosheets,which were successfully inserted in the composite coatings,have a complete structure and bond well with nickel matix without interfacial reaction.During the electrodeposition,some functional groups on GO were removed.At the same time,the internal defects and disorder of GO were reduced.Pulse reverse electrodeposition can increase the content of GO in the coating and further reduce the defect and disorder of GO,which is beneficial to the mechanical properties of the composites.3.Study on microstructure and properties of Ni-GO composite coatings.The Ni-GO composite coatings deposited with assist of supercritical fluids were prepared by DC power supply,single pulse power supply and pulse reverse power supply respectively.The surface morphology,crystalline orientation,grain size,microhardness,wear resistance and corrosion resistance of the different coatings were systematically analyzed.The microhardness of the coating prepared with pulse reverse power reaches 930HV,which is higher than the other two kinds of coatings.Meanwhile,the pulse reverse power supply promotes the co-deposition of nickel and GO,the grain refinement in the coating and the preferred orientation of nickel grain towards(111)plane,which make the coatings have more smooth,uniform and compact surface,and show better wear resistance and corrosion resistance.