|Institution:||University of British Columbia|
|Full text PDF:||http://hdl.handle.net/2429/51757|
Biocompatibility is the primary difference distinguishing biomaterials from other engineering materials. Corrosion resistance becomes important since the corrosion rate is strictly related to the ion release of biomaterials. Niobium (Nb) could be one of the potential materials to be used as metallic bio-implants because of its good biocompatibility, magnetic resonance imaging (MRI) compatibility, and cold working performance. The main objective of this work is to develop a mechanistic understanding of electrochemical corrosion response of Nb alloys as bio-implants by electrochemical methods, static immersion tests, and surface analysis techniques. The effect of microstructure and grain orientation on the corrosion behavior and properties of the passive film was also discussed. Surface treatments were carried out to further increase the corrosion resistance and bioactivity of Nb. The results showed that Nb alloys exhibit superior corrosion resistance in the simulated body fluids. Electrochemical impedance spectroscopy (EIS) was used to monitor the thickness and the structure of the passive film. A compact and protective oxide films was formed on all Nb alloys surface and no pitting or transpassive behavior occurred during the static immersion process up to 24 weeks. The existence of bovine serum albumin (BSA), microstructure as well as the surface grain orientation could affect the corrosion behavior of Nb. No pitting or transpassive behavior was observed in the presence of BSA and NaF. Furthermore, Nb nano-porous and nano-dimples were successfully prepared by anodization methods to improve the bioactivity of Nb. The surface roughness induced by the nanostructure play a critical role in the apatite nucleation and growth during the immersion in simulated body fluid, and the chemical composition of the oxide films could also influence the apatite formation to a certain degree. A mechanism of the apatite nucleation and growth on the nano-structure is proposed. In summary, from the view of corrosion resistance, Nb alloys could be possibly used as metallic bio-implants.