Preparation Of Micro-arc Oxidation Coating On Biomedical Magnesium-zinc Alloy And Its Microstructure And Properties

Biomedical magnesium alloys with biodegradability in body and good biocompatibility gradually have a wide range of applications in vascular stents,orthopedic materials,bone fixation materials and other biomedical materials.But the corrosion rate of biodegradable magnesium alloys is too fast to meet the needs of human implantation.At present,the research focus on biomedical magnesium alloy is concentrated in alloying treatment and surface modification.Alloying requires that the addition of alloying elements to the human body is non-toxic and can improve the performance of the magnesium alloys,so the addition of zinc in the magnesium alloys is gradually concerned.Surface modification technology in biomedical equipment requires good biocompatibility,the coating should effectively improve the corrosion resistance of the alloys and the coating must have a good binding force with equipment.Therefore,it is significance to add alloying elements and surface modification with corrosion resistant coating on the magnesium.In order to study the micro-arc oxidation technology of magnesium-zinc alloys,this object selected pure magnesium,Mg-3Zn and Mg-5Zn as the raw materials.Preparation of phosphate,silicate,calcium and phosphorus containing electrolyte,determined the better micro-arc oxidation test parameters through pre-experiments.Finally,the phosphate,silicate and calcium phosphorus MAO coatings on materials were successfully prepared.The two-dimensional and three-dimensional morphology of the coating were analyzed by SEM and AFM.The EDS,XRD and XPS results showed that the coating composition,elemental content,chemical srate,Ca/P ratio and phase composition.And this object also analyzed the coating roughness,binding force,coating hydrophilicity and coating profile.The results show that the three kinds of coatings have typical micro-arc oxidation structure.The three coatings is thin because of the micro-arc oxidation test parameters,but the calcium and phosphorus elements are successfully introduced into the micro-arc oxidation coating.The roughness of the coatings can induce the deposition of calcium and phosphorus.The hydrophilic results show that the micro-arc oxidation coatings can improve the hydrophilicity.SBF immersion and electrochemical test show that the micro-arc oxidation coatings can improve the corrosion resistance with uncoated samples as control group,especially for the magnesium-zinc alloy.Calcium-phosphorus coating is still covered on the sample surface after immersion 14 days.Comparison of three kinds of coatings about calcium deposition,calcium-phosphorus coating is the best one to induced calcium deposition.After research the Collagen I protein expression in different coatings,the calcium-phosphorus coating was more favorable for promoting the growth and maturation of osteoblasts.This object successfully prepared MAO coating of magnesium-zinc alloy,and the corrosion resistance of the materials were improved.The adhesion of calcium to the coatings were realized after SBF immersion.This method has a large technological improvement compared with the former methods and has good technical feasibility.It will provide experimental reference for the application of Mg-Zn alloy in biomedical biodegradable materials.