Preparation of Sn-doped Micro-arc Oxide Coating on Titanium Alloy and its Protective Properties in Simulated Body Fluid Environment
With the dramatic increase in the demand for medical implant materials,the TC4 titanium alloy can be used as a replacement material for bone tissue owing to its excellent biocompatibility and corrosion resistance.However,the TC4 titanium alloy has poor antibacterial properties,and there may be a higher risk of bacterial infection after implantation in the human body.Coatings prepared by micro-arc oxidation technology have excellent binding strength and can reduce the risk of bacterial infection of titanium alloys by doping with antimicrobial elements.To improve the protective properties of the TC4 titanium alloy in simulated body fluids(SBF),a constant-voltage mode was adopted,with a voltage of450 V,frequency of 800 Hz,duty cycle of 6％,and time of 10 min.An Sn-doped micro-arc oxide coating was prepared on a titanium alloy by varying the concentration of Na2SnO3 in the electrolyte.The microscopic morphology and elemental content distribution of the micro-arc oxide coating were studied using a scanning electron microscope with an attached energy dispersive spectrometer,and the phase compositions and compositions of the micro-arc oxide coatings were characterized by X-ray diffraction and X-ray photoelectron spectroscopy.The wear resistance,corrosion resistance,and antibacterial properties of the micro-arc oxide coating in SBF were studied using friction and wear,electrochemical,and antibacterial tests.The results show that the number of pores on the micro-arc oxide coating surface increases after the addition of Na2SnO3.With an increase in the Na2SnO3 concentration,the number of micropores on the surface of the micro-arc oxide coating decreases until they disappear,small particles appear,and the film becomes increasingly dense and uniform.The main components of the micro-arc oxide coatings are TiO2,SiO2,and SnO2.The friction factor of the micro-arc oxide coating without Na2SnO3 is lower than that of TC4.The friction factor of the Sn-doped micro-arc oxide coating in SBF decreases with an increase in the Na2SnO3 concentration,and the width of the wear mark is narrowed.When the concentration of Na2SnO3 is 10 g/L,the Sn-doped micro-arc oxide coating has the smallest friction factor and the narrowest wear mark width of 198.85 μm,which exhibits the best wear resistance,which may be due to the enrichment of small particles and the lubricating effect.However,the micro-arc oxide coating does not improve the corrosion resistance of the TC4 titanium alloy,which may be caused by the presence of micropores and other defects on the surface of the coating and the lower corrosion resistance of SnO2 than that of TiO2.The antibacterial properties of the micro-arc oxide coating improve after the addition of Na2SnO3;the Sn-doped micro-arc oxide coating prepared at a concentration of Na2SnO3 of 10 g/L and the antibacterial properties of the Sn-doped micro-arc oxide coating are the best in SBF.The optical density value decreases from 0.289 to 0.136 in the Staphylococcus aureus solution and from 0.331 to 0.171 in the Escherichia coli solution,because SnO2 could inhibit the growth of bacteria.These results provide experimental support for the application of titanium alloys in the field of biomedicine.
titanium alloymicro-arc oxidationanti-corrosion and wear resistanceantimicrobial
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