Essential distinction between one-step anodization and two-step anodization of Ti

Abstract

One-step anodization (OSA) and two-step anodization (TSA) have been widely used to fabricate anodic TiO2 nanotubes (ATNTs). It has been reported that TSA can fabricated more ordered nanotubes, as compared to OSA. However, the essential distinction between OSA and TSA of Ti has never been clarified. Here, constant current anodizations were designed to study the effects of TSA and OSA on the morphology of ATNTs. The significant differences between nanotubular architecture (length, diameter, porosity) of ATNTs fabricated by OSA and TSA were observed and analyzed for the first time. For TSA, the relationship between the nanotube length (y) and anodizing current (x) corresponds to the liner equation y=0.259x-2.3, and the relationship between nanotube outside diameter (Y) and anodizing current (x) corresponds to the linear equation Y=3.352x+65.73. However, no similar linear relationships were found for OSA. The essential distinction between OSA and TSA was clarified by oxygen bubble mould combined with plastic flow model.