||This research first presents the electrochemical investigations of Fe-, Mg-, Zr-, and Ti-based metallic glasses (MGs) for finding the potential MG-based bio-materials. The simulation body-fluid (SBF) Hanks solution is utilized for testing the corrosion resistance of MGs. In addition, a simple cyclic voltammetry method is used for rapid verification of the potential electrochemical responses. It is found that the Ti- and Zr-based MGs can sustain in the body-fluid, exhibiting the best corrosion resistance and electrochemical stability. The rapid screening process suggests that the Ti65Si15Ta10Zr10 metallic glass has high potential for biomedical applications due to its good electrochemical stability and very low cytotoxicity.|
Secondly, the electrochemical behaviors and the cell toxicity of two newly developed TiZr-based MGs, Ti42Zr40Si15Ta3, Ti40Zr40Si15Cu5, with lower or without unfavorable elements are systematically investigated. The electrochemistry property and biocompatibility of these two MGs are also compared with the controlled sample of pure Ti and the MG with a higher Cu-content, Ti45Cu35Zr20. Results show that the MGs with a low Cu content exhibit low electrochemical response. Both the solid specimens and the mediums after the potential state test for pure Ti, Ti42Zr40Si15Ta3 and Ti40Zr40Si15Cu5 exhibit no significant cytotoxicity in the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test, while the tested medium for Ti45Cu35Zr20 MG shows lower cell viability. The good healing condition and the low C-reactive protein (CRP) index for the implanted New Zealand rabbits in one-month in vivo test also show the satisfactory short-term biocompatibility of the TiZr-based MGs. The electrochemical measurements, in vitro and in vivo experiments confirmed that the developed TiZr-based MGs with lower Cu content (≦ 5%) are promising for biomedical purposes.
Thirdly, the bio-corrosion response of the Cu-free Ti45Zr40Si15 and Cu-containing Ti40Zr40Si15-Cu5 and Ti45Zr25-Cu30 MGs are explored, in terms of open circuit potential, potentiodynamic polarization, electrochemical impedance, as well as cytotoxicity MTT testing. The role of Cu in the Ti-based MGs, tentatively applied for bio-implant, is established and modeled. The presence of nobler Cu will impose two opposite effects. Since the minor positive shift of Ecorr for forming oxide layers is not of a major issue, the negative effect on local pitting and ion release would cause major drawback. The Cu-free Ti45Zr40Si15 and minor-Cu Ti40Zr40Si15-Cu5 metallic glasses exhibits promising performance.
Finally, we examine the nanocrysalline effect on the corrosion behavior of the Zr- and TiZr-based MGs in SBF. The Zr53Cu30Ni9Al8 and Ti42Zr40Si15Ta3 metallic glasses were annealed at temperatures above the glass transition temperature, Tg, with different time periods under the protective argon atmosphere to result in MGs with different degrees of crystalline Zr2Cu and β-Ti nano-phases in the amorphous matrix. Because of the serious galvanic corrosion, the polarization measurements show lower corrosion resistance for the nanocrystallized MGs with reactive Zr2Cu phases. In comparison, the nanocrystallized MGs with corrosion resistant β-Ti phases exhibited more promising corrosion resistance, due to the superior pitting resistance.