나노튜브 형성된 Ti-Nb-Zr 합금의 표면 특성

Abstract

Titanium and Ti alloys have been used extensively as bone-implant materials due to their high strength-to-weight ratio, good biocompatibility and excellent corrosion resistance. In this work, we have investigated the surface characteristics of nanotubes formed on Ti-30Nb-xZr (X : 3, 7, 15 wt %) alloys in 1M H3PO4 electrolyte containing 0.8 wt % NaF using various electrochemical methods. The corrosion behaviors were investigated using potentiostat(Model 362, EG＆G Company, U.S.A) in 0.9 % NaCl solution at 36.5 ± 1℃. Microstructural morphology, crystallinity and composition of nanotube oxide layer were observed by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (TF-XRD) and energy-dispersive spectrometer (EDS), respectively.

The results were as follows;

1. The nanotubes formed on the Ti-30Nb-xZr alloy surface were transformed from the anatase to rutile structure of TiO2. 2. Titanium oxide nanotubes were formed with diameter varying from approx. 40～80 ㎚ (small tube) to 160～220 ㎚ (large tube) and length from approx. 3.5 ㎚ (Ti-30Nb-3Zr) to 4.8 ㎚ (Ti-30Nb-15Zr). 3. The composistion of the alloys has a great influence on the two-size-scale structure, and regular assembly structure appeared predominantly with Zr content. 4. The corrosion current density of the nanotube formed Ti-30Nb-xZr alloys are higher than that of non-anodized Ti-30Nb-xZr alloys. But the polarization curves of nanotube formed Ti-30Nb-xZr alloys was shifted to right side and had the widest passive range. 5. Nanotubed Ti-30Nb-xZr alloys have lower polarization resistance than non-nanotubed Ti-30Nb-xZr alloys.