| Titanium alloy has been widely used in dental and orthopedic medical implants in recent years,but titanium alloy itself has poor wear resistance and the surface is not biologically active,so surface modification is needed to further enhance its surface bioactivity and biofunction to improve the implantation effect.Ceramic coatings prepared by plasma electrolytic oxidation surface modification technology have the advantages of strong film-base bonding and good wear and corrosion resistance,thus becoming a research hot spot for improving the surface properties of titanium alloy medical implants.In this paper,the surface modification of Ti-13Nb-13Zr titanium alloy was carried out by plasma electrolytic oxidation technique.Different Ca/P ratio electrolytes（CA20,CA35,CA50）were selected to study their effects on the microscopic morphological structure and properties of HA/Ti O2 composite coatings and to analyze the growth mechanism of HA/Ti O2 ceramic coatings.The results show that the prepared HA/Ti O2 ceramic coating has a typical three-layer structure with a porous honeycomb surface.The physical phase composition is mainly anatase and rutile phases.The electrolyte Ca/P ratio can influence the coatings thickness,surface element content,phase composition and HA formation.The CA35 ceramic coating had the maximum thickness（202μm）and a surface element content Ca/P ratio of 1.98,providing the best wear resistance,corrosion resistance and stability.Compared with the substrate,the friction coefficient of CA35 coating decreased from 0.89 to 0.19,the corrosion potential decreased from-429.17 m V to-243.92 m V,and the corrosion current density decreased from1.010×10-5 A/cm2 to 3.491×10-8 A/cm2.The Ti4+ion precipitation in PBS solution decreased by 77%.The ZIF-8 nanoparticles were successfully deposited on the surface and pore structure of PEO coating by hydrothermal synthesis.The ZIF-8 particles are immobilized in the coating pores and surface by electrostatic force and N-Ti-O bonding.Compared with the Ti-13NB-13Zr,the hydrophilic properties of the ZIF-8/HA/Ti O2 composite ceramic coating showed a significant improvement.The contact angle decreased from 105.99°to 31.36°.ZIF-8 particles can slowly degrade in phosphate buffered solution and show acidic p H sensitivity.The highest concentration of Zn2+ions released by decomposition was 2931.89μg/L,which was lower than the critical value of cytotoxicity（12500μg/L）.After loading ZIF-8 nanoparticles,the ZIF-8/HA/Ti O2 composite ceramic coating made up for the lack of antibacterial properties of Ti-13Nb-13Zr alloy,and the antibacterial rate against Escherichia coli reached 90.75%.The ZIF-8 nanoparticles were loaded in the plasma electrolytic oxide ceramic coating prepared in electrolyte solution with suitable Ca/P ratio.The ZIF-8/HA/Ti O2 biofunctional composite ceramic coating effectively improves the wettability,wear resistance,corrosion resistance and biological activity of the alloy surface,which is expected to provide a new strategy for the design of multifunctional medical titanium alloy implants. |
