Research On Electrochemical Behavior And Haemocompatibility Of Biomedical TiNi Shape Memory Alloy And Cobalt Alloys

The electrochemical property and haemocompatibility of biomedical TiNi shape memory alloy, CoCrNiW, CoCrNiMo and their specimens of ion implantation modification had been investigated in the dissertation. The corrosion rates of three alloys were measured in Tyrode's solution with potentiodynamic linear polarization, fore-point weak polarization, Cao Chunan weak polarization, transient linear polarization and atomic absorption spectroscopy method. It was shown that the corrosion rates of three alloys were very low due to their excellent corrosion resistance. Atomic absorption spectroscopy method, determining directly the concentration of ion in solution, was a direct and proper technique measuring corrosion rates for biomedical materials. By electrochemical technique, physical detection method, the electrochemical behavior, haemocompatibility, and the effect of flowing, aerating and fibrinogen on polarization were studied. Results indicated that three alloys, with extensive passive region and small passive current, exhibited good resistance to general corrosion. According to the hysteresis loop and picture of SEM, TiNi was susceptible to pitting corrosion while cobalt alloys were resistant to it. Flowing solution almost didn't do obvious difference to anodic polarization of cobalt alloys. But pitting potential Eb of TiNi decreased markedly with the increasing of velocity. The aggressiveness of aerated solution accreted by increasing the limit diffusion current density of oxygen. When fibrinogen was added to the solution, it formed complex on alloy surface and its electrochemical transference destroyed the passive oxide film, decreasing the passivation property of alloys. SEM pictures told that the distribution of fibrinogen absorbed on surface was un-successive. The adsorption amount measured by UV rayabsorption was respectively 9.667pg/cm:, 9.56lpg/cm' and l0.628pg/cm2 on TiNi,CoCrNiW and CoCrNiMo. The results of haemocompatibility measurement showedthat TiNi had better haemocompatibility and surface property than CoCrNiW andCoCrNiMo.Aner single and double ion-implantation the electrocheAncal property andhaemocompatibility of alloys were investigated. lt was fOund that the electrochemicalstability was significantly improved, dynamic clotting time was prolonged andhemolysis rate decreased after ion implafltation. All the results poinied out that theanodic polarization property and haemocompatibility were improved by ion plantationand dual implantation was better than single plantation. X-ray diffraction analysis ofalloys after dual implantation revealed that metal carbides, oxids and illtermetallicphases fOrmed on surface. And these phases dispersing on the alloy surface and theamorphous film prevented the dissolving of elements and improved the corrosionresistance and haemocompatibility.