| Magnesium alloy is expected to be an ideal biomedical implant material due to its good comprehensive mechanical properties,biocompatibility,and biodegradability.However,magnesium alloy is easily corroded in the physiological environment,resulting in a rapid decrease in mechanical properties and cannot provide long-term effective mechanical support,which seriously affect the growth and healing of bone tissue.Moreover,potential bacterial infections at the initial stage of implantation is also one of the reasons for the failure of implantation.Therefore,in this study,the surface modification of AZ31 magnesium alloy was performed to improve the corrosion resistance and antibacterial properties,thereby meeting the requirements of biological implant materials.In this work,the hydroxyapatite coating was prepared on the surface of an alkali heat-treated magnesium alloy by hydrothermal method,and then the superhydrophobic composite coating of hydroxyapatite/stearic acid was obtained by stearic acid immersion treatment method.The effects of hydrothermal parameters and stearic acid treatment conditions on the morphology,structure,composition,and wettability of the coating surface were studied.The immersion experiment in simulated body fluid（SBF）was used to study the corrosion resistance,in vitro degradation process and the ability of inducing mineralization of the sample,and the anti-bacterial adhesion performance of the coated magnesium alloy surface was studied by bacteria experiment.The experimental results showed that the hydroxyapatite coating prepared by hydrothermal method in the hydrothermal solution at p H of 8.5 and 120℃.Then superhydrophobic composite coating was prepared after soaking in 0.1 M stearic acid ethanol solution at 100℃.The prepared composite coating had the excellent superhydrophobic properties,and the contact angle was 152.52±1.06°.Meanwhile,the composite coating coated magnesium alloy exhibited excellent electrochemical performance,the corrosion current density was 0.165±0.015μA cm-2,and the polarization resistance value was 301.100±28.500 kΩcm2.The immersion experiment in vitro showed that the composite coating coated magnesium alloy had the long-term corrosion resistance.The sample still maintained a complete macroscopic appearance after immersion for 21 days,the corrosion rate was always below 0.500 mm/y,and the p H value of the simulated body fluid maintained in the range of 7.20-7.70.During the immersion process in vitro,the superhydrophobic coating can realize the transition from superhydrophobicity to hydrophilicity,and rapidly induced the formation of mineralized apatite,indicating that the composite coating coated magnesium alloy had good biological activity.Bacterial experiments confirmed that the superhydrophobic composite coating had excellent anti-bacterial adhesion properties. |
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