Nanotube growth analysis in the interface between oxide film and titanium alloy substrate using STEM and FE‐SEM

Abstract

ABSTRACTNanotube growth analysis in the interface between oxide film and titanium alloy substrate has been researched using scanning transmission electron microscope and field‐emission scanning electron microscopy (FE‐SEM). The Ti‐35Nb‐xHf (x =3, 7 and 15 wt.%) alloys were prepared using the sponges of Ti, Nb and Hf. The nanotube on the alloy surface was formed in 1.0 M H3PO4 with 0.8 wt.% NaF, using a potentiostat. The nanotube growth analysis on the titanium alloys was investigated using FE‐SEM, energy dispersive spectroscopy (EDS), X‐ray photoelectron spectroscopy and X‐ray diffraction. Microstructures of Ti‐35Nb‐xHf alloys showed an equiaxed structure and the α” phase decreased with Hf content, whereas the β phase increased as Hf content increased. The nanotube surface mainly consisted of Nb and Ti oxide. The peaks of Nb and O elements exhibited higher intensities on the nanotube surface compared with the matrix, whereas peaks of Ti and Hf exhibited lower intensities on the matrix surface from EDS line profile. The shape of nanotube on the Ti‐35Nb‐xHf showed two scales of nanotubes; large (190 nm–220 nm) and small (91 nm–104 nm). The diameter of the nanotubes decreased with increasing the Hf content, whereas the length of the nanotubes increased with increasing Hf content. Copyright © 2012 John Wiley & Sons, Ltd.