Nanotube Formation and Morphology of Ti-Nb Alloy with Nb Content

In biomedical implants and dental fields, titanium has been widely utilized for excellent corrosion resistance and biocompatibility. However, Ti and its alloys are non-bioactive after being implanted in bone.

Objective: For further improvement in biocompatibility, the nonotube formation and morphology of Ti-Nb alloy with Nb content have been investigated using various experimental methods.

Methods: In this study, for the purpose of improvement in biocompatibility the anodic TiO₂ nanotube on Ti-xwt%Nb alloys were fabricated by electrochemical method in phosphate solution, and the effect of Nb content on the pore size, the morphology and crystallinity of TiO₂ nanotube formed by the anodic oxidation method was investigated. Ti contaning Nb up to 10, 20, 30 and 40wt% was many times melted to improve chemical homogeneity using vacuum furnace and homogenized for 6h at 1000°C in argon atmosphere. Electrochemical experiments were carried out using a direct current voltage source(KJPP-5003, KapJin, Korea). 1M H₃PO₄ with small amount of sodium fluoride ions were used as electrolytes. Microstructural morphology, crystallinity and composition of oxide layer were observed by SEM, XRD, and EDS, respectively.

Results: The structure of alloy was changed from a-phase to b-phase with increase of Nb content. From XRD results, the structure of TiO₂ formed on the Ti-xNb surface was anatase, and peaks of Nb₂O₅ or other Nb oxide were not detected because that Nb atoms were dispersed in TiO₂-based solid solution. On the Ti-xNb alloys, the nanotube morphology depended on the nature of the matrix phase(a or b-phase). In the b-phase, nanotube diameter(55nm) was smaller than that(95nm) of a-phase. The straight nanotubes were obtained in phosphate/sodium fluoride electrolytes and nanopores were formed in the range of between 60nm and 100nm.

Conclusions: As the Nb content increased, porosity size of nanotube decreased. Also, Ti-Nb alloys showed phase transformation of the a-phases into b-phases.(Corresponding Author: hcchoe@chosun.ac.kr)