Research Of Electrophoretic Deposition Of Graphene Oxide And Its Composite Coating On AZ31 Magnesium Alloy

Biodegradable medical magnesium alloy have a rapid degradation rate in human body nvironment, which limits their clinic applications. Graphene oxide(GO) exibites good biological compatibility and stability, which has a potential application in biomedical field. In the present dissertation, an electrophoretic deposition method was used to preparate graphene oxide and graphene oxide / hydroxyapatite composite coating on AZ31 magnesium alloy. The potential of GO in electrolyte were measured by Zeta potential meter. Fourier transform infrared spectrum,(FT-IR), scanning electron microscope(SEM) and X-ray diffraction(XRD) were used to perform surface morphology observation, structure and composition analysis of the GO and GO/HA film layer. A tensile testing machine was adopted to evaluate the bonding strength between the layer and substrate. Electrochemical mesuremenys and immeision corrosion test was used to evaluate the corrosion resistance of GO and GO/HA films on AZ31 magnesium alloy.In this dissertation, we study the effects of process parameters on the electrophoretic deposition of GO and GO/HA composite coating by controlling the single variable. GO electrophoretic electrolytes were prepared by using organic compounds isopropyl alcohol(butyl alcohol or absolute alcohol) as dispersing agent and inorganic compound calcium nitrate(magnesium nitrate or aluminum nitrate) as dielectric which changes the electric charge of GO from electronegativity to electropositivity. The electrophoretic deposition was performed by DC constant voltage and magnesium alloy as the cathode. A uniform GO film could be obtained on magnesium alloy with porous character. By ddding hydroxyapatite powder into electrophoretic electrolytes, similarly we can obtain graphene oxide/hydroxyapatite composite coating on magnesium alloy with hydroxyapatite particles distributing between graphene oxide sheets.The electrochemical corrosion and immersion corrosion tests in SBF show that the GO and GO/HA composite coating can significantly improve the corrosion resistance of the magnesium alloy. By controlling the composition of the electrophoretic electrolytes and deposition process of the electrophoretic deposition, we could obtain the bonding strength being larger than 24 MPa between the GO(GO/HA composite) coating and the magnesium alloy substrateWe prepared electrophoretic electrolytes, with isopropyl alcohol(0.2g/L) as dispersant, Al(NO3)3(0.2g/L) as dielectric, GO(0.2g/L), the mass ratio of GO/HA being 1:1. Electrophoretic deposition was performed at 150 V for 20 min. It shows that the corrosion resistances of AZ31 with GO coating or GO/HA composite coating is the highest, and the bonding strength between the coatings and the Mg substrates are the best.