Preparation and Properties of Pulsed Composite Coatings of Supercritical Graphene Quantum Dots

Using graphene quantum dots with unique properties as the second phase additive and utilizing the high diffusion and transfer properties of supercritical fluids, Ni-based nanocomposite coatings were prepared by pulsed electrodeposition technology. The effects of the pulse duty cycle on the microstructure, mechanical properties, and corrosion resistance of composite coatings were investigated. The results showed that the graphene quantum dots are successfully embedded in the coatings, and under supercritical conditions, a suitable pulse duty cycle can improve the surface density and sphericity of the coatings. Raman spectroscopy and carbon-sulfur analyzer test indicated that supercritical conditions can improve the quality and content of graphene quantum dots in the coatings. The graphene quantum dots composite coating prepared when the pulse duty cycle is 0.3 has more excellent mechanical properties. Its microhardness is higher, and it has a smaller friction coefficient and wear scar cross-sectional area. Tafel polarization experiments indicated that under supercritical conditions, the corrosion current density of graphene quantum dots composite coating prepared when the pulse duty cycle is 0.3 is small, which is 1.286 × 10−5 A·cm−2. The 120 h immersion corrosion study showed that no obvious corrosion occurs on the surface. Therefore, its corrosion resistance is more excellent.