Study The Formation Mechanism Of Porous Titanium Anode Oxidation Nanopores

It is generally agreed that the traditional formation mechanism of porous anodic titania nanotubes (PATNT) is the generation of the pores is due to "acidic field-assisted dissolution"(TiO2+4H++6F-â†'[TiF6]2-+2H2O), the deepening of the holes is caused by the concentration of the electric field which accelerates the acid dissolution of the barrier layer. But the traditional theory cannot give a convincing explanation for hexagonal close packed structure and hemispherical bottom structure of channels.Firstly, We found the existence of the pores in the preparation of oxide flim in fluorine ions free electrolyte, such as H2SO4, H3PO4, which doubts the rationality of the traditional theory; While preparing oxide film in fluorine ions containing electrolyte, the surface pore is not obvious, but nanotubes have been formed below the surface layer, which implies the limitations of traditional theory. In addition, we present Oxygen Bubble Mould Effect based on previous studies of PATNT, but the author doesn’t deny the rationality of the traditional theory, PATNT should be the joint result of acidic corrosion pores and O2evolution. Anodizing current (j) within the oxide included jion and je during anodizing process. The jion was used to form oxide and the je was used to the release of oxygen gas. Furthermore, the samples fabricated on different conditions are characterized by scanning electron microscopy emission (SEM), electrochemical test system and X-ray photoelectron spectroscopy (XPS). With the analysis of SEM images, current-time curves for anodic oxidation and X-ray photoelectron spectroscopy analysis, which confirm the rationality of Oxygen Bubble Mould Effect; two methods are used to prove the novel model indirectly, i.e. changing the pressure and adding the reducing agent. Finally, in order to prepare more highly ordered PATNT, we use two post-treatment methods, which have big effects on PATNT surface morphology and nanotubes structure, and explore a post-treatment method which has the best performance.