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In order to adapt to the current rapid development of aerospace，automotive，and high-end equipment manufacturing industries，using graphene quantum dots (GQDs) with unique properties as the second phase additive，Ni-based nanocomposite coatings were prepared by supercritical pulse electrodeposition technology.The effect of pulse frequency on the microstructure，corrosion resistance，microhardness，wear resistance and other properties of composite coatings under supercritical conditions was investigated.Results showed that when the pulse frequency was 2 000 Hz under supercritical conditions，the microstructure of the prepared coating was densified and uniform，with better sphericity.XRD results showed that supercritical conditions could change the preferred orientation of crystallization and the appropriate pulse frequency could refine the coating grains and reduce the grain size.At a pulse frequency of 2 000 Hz under supercritical conditions，the properties of the prepared coating were more excellent.Electrochemical experiments showed that it had the largest capacitive arc radius，the highest self-corrosion potential，the lowest corrosion current density，and the largest capacitive modulus，so the coating had the most excellent corrosion resistance.The coating prepared at 2 000 Hz pulse frequency had the highest microhardness，reaching 835.4 HV2 N，and had the best wear resistance with a wear scar cross-sectional area of the coating of 1 582 μm2.The microhardness and wear scar cross-sectional area were 126%，107%，121%and 134%，and 47.6%，57.1%，71.5%and 44.3%of the coatings prepared with pulse frequencies of 100，1 000，3 000 Hz and under room temperature and pressure，respectively.Under supercritical conditions，the graphene quantum dot composite coating prepared at a pulse frequency of 2 000 Hz had excellent corrosion resistance and wear resistance.

The supercritical nickel-graphene composite coating was prepared by supercritical carbon dioxide fluid(SCF-CO2) assisted pulsed composite electrodeposition technique with graphene oxide (GO) as the second phase additive. The effect of pulse duty cycle on the microstructure and mecha-nical properties of the coatings was investigated. The results show that the microstructure of composite coating can be refined significantly by the combination of supercritical carbon dioxide fluid and graphene oxide. The change of the (111) and (200) peaks in the XRD patterns of the composite coating shows that change occurs in preferred orientation during the crystallization process. The change of duty cycle has great influence on the mechanical properties of the coatings. The micro-hardness of the supercritical nickel-graphene composite coating is as high as 756.8HV0.2 and the cross-sectional area of wear scar is 4385μm2 at 50% duty cycle. Compared with the nickel-graphene comp-osite coating prepared under conventional conditions, the microhardness and wear resistance of super-critical nickel-graphene composite coating are increased by 1.6 and 11 times.

Graphene, a two-dimensional carbon material made up of a single atomic layer structure, shows unique physical and chemical properties.Graphene reinforced metal matrix composites have attracted more and more attention due to excellent properties.In this paper,the synthesis methods of graphene reinforced metal matrix composites were reviewed.The research progress of graphene reinforced metal matrix composites in strength,thermal conduction,conductivity and corrosion resistance was comprehensively analyzed.Finally, on the basis of pointing out the importance of the study on interfacial bonding mechanism, the development trend of graphene reinforced metal matrix composites in improving the performance and extending the scope of application was prospected.

Supercritical carbon dioxide (SCF-CO2) nickle-graphene nano composite electrodepositing process was studied to improve the micro-hardness and wear resistance of the composite electrodepositing layer. Four electrodepositing parameters such as supercritical pressure, graphene oxide addition, cathode current density and electrodepositing time were optimized by orthogonal experiment method. The results show that the range value (R) of the graphene oxide additionis 45.385, which means it has the biggest effect on the micro-hardness of composite electrodepositing layer. The optimal addition amount is 0.15 g/L. The cathodic current density has the greatest effect on the wear resistance of the composite electrodepositing layer, with the range value (R) of 9196 and the best cathodic current density of 12 A/dm2. The micro-hardness and wear resistance of the composite electrodepositing layer prepared under the SCF-CO2condition have larger promotion than that of normal condition. [ABSTRACT FROM PUBLISHER]

Composite electrodeposition based on supercritical carbon dioxide fluid (SCF-CO2) was used in preparing Ni-SiC nanocomposites with high micro-hardness. The process parameters were optimized by orthogonal test. The effect of cathodic current density, supercritical fluids pressure, temperature and adding quantity of SiC particles to the micro-hardness and co-deposition rate of the nanocomposites were studied. The results show that the micro-hardness of Ni-SiC nanocomposites is as high as 929.3 HV with the work pressure 13 MPa, temperature 50°C, current density 7 A·dm−2and SiC particles adding amount 10 g·L−1, which is improved 78.57% than that of common composite electrodeposition. Then the surface morphology and energy spectrum of Ni-SiC nanocomposites were analyzed by scanning electron microscope (SEM). The results show that the SiC particles are much uniformly distributed in the nanocomposites and the SiC particles content in which reaches 2.84 (wt%) when working pressure is in 8∼16 MPa. These properties are significantly higher than those of common composite electrodeposition. [ABSTRACT FROM PUBLISHER]

Ni-SiC nanocomposite coating was fabricated on the copper substrate by eletrodeposition technique with the aid of ultrasonic and agitation. The effects of cathodic current density, temperature, stirring rate and surfactants on the micro-hardness and deposition rate of Ni-SiC composite were studied. The optimal process parameters were determined by orthogonal test as follows: cathodic current density 5 A/dm2, suspension amount of SiC 4g/L, temperature 30°, pH 4.0, and stirring rate 200 rpm. The hardness of the films was tested by digital micro hardness tester. The surface morphology and microstructure of the films were inspected by metallographic system. The results show that, with proper ultrasonic and agitation, the surface becomes compacter and smoother, the porosity is decreased and the nickel crystalline is also refined. The hardness of the nano-composite coating is remarkably improved compared with the conventional electroforming coating. [ABSTRACT FROM AUTHOR]