Synthesis And Characterization Of Bioactive Modification TiO₂Film On Tribology And Biological Properties

Due to the excellent mechanical compatibility and biocompatibility of medical titaniumalloy, it has a broad application prospect in hard tissue replacement and repairment field. Butmedical titanium alloy belongs to biological inert materials. And the combination with bone isa kind of mechanical lock after implantation in the human body, whose surface will be directcontact with blood, organization or cell in long-term. And the interaction between them willmake their functions and properties affected. Toxic, inflammation or blood clots reactionsmay take place. Therefore, it is essential to control and improve the surface properties ofmedical titanium alloy. In order to shorten the medical titanium implant bone integration time,improve the wear resistance, corrosion resistance and biological activity of titanium baseimplants, and guarantee the success of the implant operation to immediate or initial fast andbone tissue together in purpose, all kinds of surface modification technology is widely appliedto improve the implant material surface configuration and surface biological activit y.Micro-arc oxidation （MAO） surface modification method can prepare good biocompatibilityand hardly stripped surface film, which is considered to be the most effective surfacetreatment techniques in promoting the combination of bone and implant. The activationtreatment of implant surface and porous structure design can induce bone ingrowth, which canalso increase the interface bonding strength and speed up the bone repair process, so as toimprove the treatment effect. But the surface porous structures also provide a hotbed forbacterial growth and postoperative infection.This paper designed the surface modification method from the perspective of bionics onpure titanium surface. In order to prepare an antibacterial and biological film, micro-arcoxidation was chosen as the foundation, combined with alkali heat treatment and ionimplantation surface modified composite processing method. The phase analysis （XRD andFTIR） and microscopic characterization method （SEM with EDS） were used to study thecharacteristics of the titanium surface film. Mineralization behavior of the surface film in thesimulated body fluid （SBF） was evaluated by the stability, abrasion resistance, antibacterialability and the biological activities. The biocompatibility of the film was also analyzed.The effects of micro-arc oxidation process parameters on the film surface morphology,organization and thickness were stydied. And the different parameters on the material surfacehydrophilic hydrophobic nature were also stuied by using the orthogonal experiment method.Research results show that the surface hydrophilicity has the relationship with the pore sizeand the distribution state of on porous surface, which can achieve the best fit by adjusting the parameters. The influence of reaction parameters on hydrophilic property has the relationshipas follow: duty ratio> reaction time> temperature> pH> pulse voltage.In the present the study of MAO film containing Ca and P, further processing is neededto form ceramic film containing hydroxyapatite. In order to optimize the process and improvethe biological activity of MAO film, the film prepared by micro-arc oxidation combined withalkali heat treatment was studied. The structure, element distribution and mineralization in thesimulated body fluid （SBF） were studied. Results show that the two-step method can obtain afilm containing lots of Ti-OH group, Ca and P element. Ti-OH group is essential for inducingthe hydroxyl apatite formation in SBF. Compared with direct micro-arc oxidation method, thecomplex treatment film containing Ca and P has good biological activity.In order to improve the film abrasion resistance, the film prepared by micro-arcoxidation combined with N ion implantation was stuied. The effects of abrasion resistance,electrochemical properties and biological activity characterized on the film were stuied. Theresults show that the obtained nitriding layer and oxide layer increased the surface hardness.And ion bombardment effect will produce defects on the film surface, which will increase thesurface roughness. When choosing the right implation dosage, the matching of hardness andsurface roughness can achieve the best. The surface will have the best wear resistanceproperties. When the number of defects and uniform film-forming performance achieve thebest match, the surface has the best corrosion resistance. N ion implantation possessessaturation dosage. Exceeding this dosage, the relative content of elements dosage in the filmdoes not increase. Surface defects will increase due to the mechanical effect of ionbombardment which will lead to lower wear resistance and corrosion resistance. Under thecondition of dry and wet friction, when the implanation dosage is1017ions/cm2, the samplehas the least friction factor. The implantation dosage has great influence on the corrosionpotential. When the implantation dosage is1017ions/cm2, the corrosion potential of thesample is the highest, which has the best corrosion resistance. Biomimetic mineralizationsolution was used to examine the bioactivity of film on the pure titanium prepared by N ionimplantation and micro-arc oxidation combined with N ion implantation. After24h, acalcium phosphate phase received both on the two sample surface, which shows that the twomethods have good biological activity. These methods can induce phosphate deposits on thesurface of the sample.In order to obtain a biological and antibacterial function film, the effects of micro-arcoxidation combined with Ag ion implantation on the antibacterial, corrosion resistance and itsbiological activity of the film was studied. Results show that the corrosion potential of micro-arc oxidation combined Ag ion implantation film was higher than that of pure titaniumspecimen in the SBF, which suggests a better corrosion resistance by complex method. Agexists in the form of Ag nanoparticles in the film. When the Ag ion implantation dosagereaching10¹⁷ions/cm², the ion implanted micro-arc oxidation film has obvious antibacterialeffect on the staphylococcus aureus, whose antibacterial rate was95.8%and has the bestcorrosion resistance at the same time. When the implantation dosage reached2×10¹⁸ions/cm²,the antibacterial rate got100%.Using cell culture methods to evaluate the biocompatibility of porous films prepared byMAO, MAO combined with alkali heat treatment, MAO combined with N ion implantationand MAO combined with Ag ion implantation. Cell compatibility test results show that theattachment of cell on the complex porous film is good. In this experiment the introduction ofAg ions did not reduce the cell growth activity. The film has antibacterial ability, at the sametime, does not have obvious inhibitory effect on cell growth. It also owns good biologicalcompatibility. Compared with directly MAO treatment, composite processing methods arebetter for osteoblast growth and show a better cell compatibility.