Synthesis Of Ceramic-polymer Composite Filmson NiTi Alloy And Their Properties

NiTi alloys are widely used in medical implant,because their elastic modulus are close to human bones,they have unique shape memory effect and superelasticity.Especially,NiTi alloys are widely used in bone plate,such as internal bone plate of femoral medullary,encircling bone plate,patellar fracture plate and so on.The bone plates are used as a device to connect and fix the fracture and maintain the normal healing of the fracture,when contact with bone and body fluid in human body,it will inevitably lead to wear、corrosion and the release of Ni toxic ions,what,s more postoperative infection will bring healing difficulties and prolongs course of treatment,which will affect the long-term use of NiTi alloys in human body.In order to improve the corrosion and wear resistance,suppress the release of Ni ions and improve the bacteriostatic properties to meet the requirements of the plate,enhancing the use security and biocompatibility of biomedical NiTi alloy,Ti（C,N）-Ti O₂ceramic films were prepared by cathodic plasma electrolytic deposition（CPED）,followed by potentiostatic deposition（PD）of polypyrrole（PPy）.XRD,ATR-FTIR,XPS,SEM and EDS were used to characterize the phases,compositions and morphologies of the films,additionally,the friction and wear property,corrosion resistance,Ni²⁺release and antibacterial ability of the films were evaluated.Results showed that the thickness of Ti（C,N）-Ti O₂/PPy composite film prepared by two methods reach 110μm.The porous Ti（C,N）-Ti O₂films that prepared by CPED improve the above mentioned properties of the alloy.The pore of ceramic films provided"riveting"effect for subsequent polymer deposition,and also facilitated the formation of dense PPy films.Compared with ceramic films,the composite film has better frictionl properties,and its friction coefficient and wear rate are only 12.5%and 4%of the matrix,respectively.The PD synthesized PPy films sealed the pores in the inner layer,which reduced the enter channel of corrision media.The corrosion current density was reduced by two orders of magnitude,and improved corrosion resistance.Compared with a monolayer ceramic film,the dual-layered films presented a more noticeable decrease in the average release of Ni²⁺,which was only 1.5%of that of the uncoated alloy.Moreover,when Ag NO₃、CHI and Ag NO₃-CHI were added to the electrolyte that deposited at constant potential,the Ti（C,N）-Ti O₂/PPy-Ag、Ti（C,N）-Ti O₂/PPy-CHI、Ti（C,N）-Ti O₂/PPy-CHI-Ag were obtained respectively.These composite film all showed excellent inhibition effect on Escherichia coli and Staphylococcus aureus.After adding chitosan and Ag NO₃simultaneously,the film showed the best results.For Escherichia coli and Staphylococcus aureus,the bacteriostatic rate increased to 88%and94%that compared with the matrix 22%and 38%。...