Bioactive Coating On The Surface Of A Zr-based Metallic Glass Prepared By Micro-arc Oxidation And Its Biocompatibility

In this dissertation, Zr46(Cu4.5/5.5Ag1/5.5)46Al8(at%)(hereafter denoted as Zr Cu Al Ag) bulk metallic glass(BMG) was selected as model materials. The micro-arc oxidation(MAO) technique was used for the surface modification of the BMG and bioactive coatings were then formed on the surface of the BMG. The formation mechanism of the bioactive coatings was interpreted via fine tuning MAO process parameters, such as voltage and time. The biocompatiblity of MAOed BMG was assessed in details via electrochemical corrosion, blood compatibility, oral mucosa irritation and in vivo implantation test.Surface modification of Zr Cu Al Ag BMG was performed via MAO. The electrolyte components and concentrations were optimized. The MAO experiments were performed under different voltages. The effect of MAO voltage on the surface morphology and chemical compositions of the obtained coatings was studied. The results indicated that the coatings exhibited a porous microstructure and contained all the elements of the base alloy and the electrolyte. Compared with the as-cast BMG sample, the coatings contained less Cu and Al elements. For the case of 350 V voltage, the Ca/P ratio, and the content of Cu and Al in the obtained coating is ~1.65, and 13.38 %(wt.%) and 2.62 %(wt.%), respectively. The coating consisted of Zr O2, Si O2, Hydroxyapatite(HA) and other unknown phases. The occurrence of HA phase suggested that the MAOed coating has excellent bioactivity. The relationship between the MAO time and the thickness of the obtained coating was established under 350 V MAO voltage. The formation mechanism of MAOed bioactive coating was interpreted.The electrochemical corrosion tests have been carried out on the MAOed Zr Cu Al Ag BMGs under the different voltages. The results indicated that, in 0.9 % Na Cl solution, 0.5 mol/L H2SO4 solution and Phosphate buffered saline(PBS) solution, the MAOed Zr Cu Al Ag BMGs exhibited better corrosion resistance than the as-cast BMG and Ti-6Al-4V alloy, and the MAOed Zr Cu Al Ag BMG has the best corrosion resistance under 350 V MAO voltage. In PBS solution, the MAOed Zr Cu Al Ag BMGs precipitated less toxic Cu and Al elements than the as-cast BMG, indicated that the MAOed Zr Cu Al Ag BMGs have the better biological safety.The blood compatibility tests have been executed on the MAOed Zr Cu Al Ag BMGs under different voltages, the Hemolysis Ratio(HR), Prothrombin Time(PT), Activated Partially Thrombin Time(APTT), In-vitro Kinetic Clotting Time and Platelet Adhesion Quantity test results showed that MAOed Zr Cu Al Ag BMGs exhibited better blood compatibility than the as-cast BMG.The animal oral mucosa stimulation results indicated that the MAOed Zr Cu Al Ag BMGs under different voltages exhibited the stimulation of Grade 0 according to GB/T 16886.4-2005, which verified that the MAOed Zr Cu Al Ag BMGs were suitable for use as biomedical metallic materials. Subcutaneous implantation experiments showed that the subcutaneous tissue cells on the MAOed Zr Cu Al Ag BMGs recover and become normal after 12 weeks, which showed that the MAOed Zr Cu Al Ag BMGs have excellent biocompatibility.