Nanotubular Structure on the Ti-29Nb-5Zr Alloy by Scanning Transmission Electron Microscope.

In this study, we reported the observation of highly ordered nanotubular structure on the Ti-29Nb-5Zr alloy in various potentials and electrolytes by field emission scanning electron microscopy and scanning transmission electron microscope. From the X-ray diffraction results and microstructure analysis, Ti-29Nb-5Zr alloy had β phase. The nanotube morphologies of Ti-29Nb-5Zr alloy were transformed from nano-porous structure to nanotube structure as NaF concentration and voltage increased. Nanotube diameter and layer changed with different concentration of NaF in 1 M H3PO4 at the same voltage. From the X-ray photoelectron spectroscopy results, nanotube was formed by Nb, Zr, and Ti oxide. Also, barrier layer of large tube was about 50 nm thickness, small one was 60 nm thickness. The nanotube size and crystallinity on the β Ti alloy was controlled by fluoride concentration, applied potential, anodization time, and tube layer.