Preparation And Properties Of Tantalum Oxide Composite Coating On Ti6Al4V Surface For Medical Application

Ti6Al4V titanium alloy has been the first choice material for medical implants owing to its good comprehensive properties such as biocompatibility,corrosion resistance and mechanical properties.With the increase of service time,the corrosive effect of human body fluids on Ti6Al4V causes it to release toxic metal ions such as Al³⁺,V²⁺and other metal ions,which may lead to adverse reactions of the host and even failure of the implant.Moreover,Ti6Al4V itself does not have antibacterial properties,in case of bacterial infection,the implantation failure would occur,thus causing a great threat to human health.In this paper,based on the problems existing in the clinical application of Ti6Al4V,the multi-functional coating was prepared on the surface of Ti6Al4V by magnetron sputtering.The research on its composition,preparation,characterization,bonding strength,wettability,corrosive behavior and antibacterial properties was carried out systematically.According to the gradient material theory,the design concept of a new multi-functional composite coating was proposed for medical application.The composite coating consists of five layers,the first to fifth layer of which are Ti,TiO₂,Ta_xO_y-TiO₂,Ta_xO_y and ZnO-Ta_xO_y,respectively.The first to third layers are interlayers,which can improve the bonding strength of coating system,the fourth layer of Ta_xO_y film acts as a corrosion resistance,and the outermost layer of ZnO-Ta_xO_y film is antibacterial layer.Ta_x O_y composite coatings?SL,ML-1,ML-2 and ML-3?with different interlayers were prepared on the surface of Ti6Al4V by magnetron sputtering.The coating samples were characterized by SEM,XRD and EDS,and their bonding strength,hardness,elastic modulus,wettability and corrosion resistance were investigated systematically.The results showed that Ta_xO_y thin film has an amorphous structure,and composes three kinds of tantalum suboxides.Moreover,as the number of intermediate layers increases,the hydrophobicity,hardness,elastic modulus,and the adhesion strength of the coating samples increases.The coating adhesion strength of ML-3 is 9.09 times that of SL.In addition,in the simulated body fluid,the corrosion potential of the coating sample increased whereas the corrosion current decreased,and the corrosion resistance was better with the increase of the number of layers in the middle layer.The coating protection ratio of the ML-3 sample was92.43%.The wettability,corrosion resistance and antibacterial properties of Ta_xO_y multilayer coating doped with ZnO were studied in detail.The results show that,with the increase of ZnO doping content from 3.36wt.%to 5.53 wt.%,the water contact angle of the coating surface decreases from 103.12°to 86.9°,and the hydrophilicity of the coating enhanced.The corrosion potential of the composite coating is 203 mV more than that of uncoated Ti6Al4V,and the corrosion current density is5.56?A·cm-2 lower than that of uncoated Ti6Al4V.The composite coating doped with ZnO had obvious inhibitory effect on the growth of Staphylococcus aureus.Moreover,the higher the ZnO doping was,the higher the bactericidal rate was.The bactericidal rate of ZML-200 coating sample was 98.92%.