| Medical magnesium alloys have excellent mechanical properties and good cell compatibility,researched widely in the biological materials.But corrosion rate of magnesium and its alloys in biological environment containing chlorine ion is fast,and hydrogen generated affect tissue healing,limiting the clinical application.To improve its corrosion resistance and biocompatibility,medical magnesium alloy surface modification becomes a research hotspot.AZ31 magnesium alloy serve as the research object,preparation of hydroxyapatite coating was used RF magnetron sputtering technology.Improving the bonding strength and corrosion resistance of AZ31,the metal(silver)doped or micro-arc oxidation pretreatment method was employed.The main research contents and the main research results obtained are as follows:1.To study the AZ31 magnesium alloy surface micro-arc oxidation pretreatment magnetron sputtering preparing hydroxyapatite coating corrosion resistance.Objective: by magnetron sputtering in the magnesium alloy surface forming hydroxyapatite coating to improve the corrosion resistance of AZ31 magnesium alloy and biocompatibility.Methods: using micro-arc oxidation method in NaSiO3-KOH solution electrolysis system formed in the micro-arc oxidation film,magnetron sputtering HA coating again.Modification of AZ31 magnesium alloy substrate surface morphology,chemical composition and phase structure were characterized.Adhesion strength of coating was tested by the scratch method,surface contourgraph is used to test the surface roughness.By potentiodynamic polarization curves and EIS impedance spectrum to its corrosion resistance were studied.Results: the successful preparation of AZ31 magnesium alloy surface MAO/HA composite coating.When Micro-arc oxidation current density of 0.5 A/cm2,there were a large number of uniform microporous on the surface,calcium phosphorus ratio was 1.79,the thickness was about 5microns,crystalline was good.Nano scratch experiment showed adhesion of composite coating film is strong,load of 6.91 N,roughness was lower(1.03±0.05 ?m).According to the results of PDP curve,MAO/HA/AZ31 showed the highest corrosion potential(1.4166 V vs.Ag/AgCl)and the lowest corrosion current density(2.92 × 10-8 A/cm2).Compared with the untreated AZ31,corrosion potential of MAO/HA/AZ31 promotes approximately 120 mV,corrosion current density value reduces the 36 times.Conclusion: Compound hydroxyapatite coating of AZ31 magnesium alloy is successfully prepared by micro-arc oxidation pretreatment magnetron sputtering,and significantly improves the film adhesion and corrosion resistance,for extending the application of medical magnesium alloys in biological materials laid a foundation.2.To examine the microstructure,phase composition and corrosion resistance and cytological studies of magnetron sputtering silver-doped hydroxyapatite coating on AZ31 magnesium alloy.Objective: By magnetron sputtering in the magnesium alloy surface preparation of silver-doped hydroxyapatite coating to improve the corrosion resistance of AZ31 magnesium alloy and biocompatibility.Methods: using RF magnetron sputtering method is not mixed with silver HA coating and silver HA coating,using scanning electron microscopy(SEM),X-ray energy spectrum analyzer,X-ray diffraction,and Fourier infrared spectrum analyzer to modification of AZ31 magnesium alloy substrate surface morphology,chemical composition and phase structure were characterized.corrosion resistance were studied by potentiodynamic polarization curves.MC3T3-E1 osteoblast was applied for biocompatibility of HA coating test.Results: silver-doped HA coating was successfully prepared on AZ31 magnesium alloy surface.The distribution of spherical silver particles was uniform density on the surface of HA coating,the calcium phosphorus ratio is 1.94,crystalline is good.Nano indentation experiments show the modulus of elasticity of silver-doped HA coating group was 33.75±2.98 GPa,young's hardness was 2.02±0.89 GPa.PDP curves of silver-doped HA coating in 3.5% NaCl solution showed that silver-doped HA coating group possessed the highest corrosion potential and the lowest corrosion current density.Results determined by MTT experiment show that silver-doped HA coating group has no cytotoxicity and can promote cell proliferation,morphology of MC3T3-E1 osteoblast is dendritic,no nuclear division.Alizarin red staining showed calcified nodules fusion and deep dyeing,ALP activity enhanced compared with the basal group.Conclusion: silver-doped hydroxyapatite coating on AZ31 magnesium alloy is successfully prepared,and significantly improves the modulus of elasticity and young's hardness,corrosion resistance and cell compatibility,laid the foundation for biocompatibility in vivo study. |
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