Effect of water and fluoride content on morphology and barrier layer properties of TiO2 nanotubes grown in ethylene glycol-based electrolytes

• DOI: 10.1007/s10008-013-2212-2
• Publication Date: 2013-08-15T11:52:43Z
• Authors: Próspero Acevedo-...; Luis Lartundo-Rojas; Ignacio González
• Keywords: 02 engineering and technology; 0210 nano-technology; 3. Good health

This paper studies the effect of H2O and NH4F content on morphology and barrier layer properties of TiO2 nanotubes grown by potentiostatic anodization in ethylene glycol-based electrolytes. The increase in these two variables leads to an increase in the chemical attack of the formed oxide. However, each of these variables plays a different role in the formation of TiO2 nanotubes. On the one hand, a higher percentage of H2O in the electrolyte leads to a transition from a nanoporous to a nanotubular structure, as well as to a greater diameter of the tubes and a decrease in their length and barrier layer thickness. In contrast, a higher NH4F concentration decreases nanotube diameter and increases their length modifying barrier layer properties due to insertion of F− ions into the lattice. This diminishes the barrier layer resistance, but increases both the adsorption and the diffusion coefficient of F− ions. The different roles of H2O and NH4F in film formation are also associated with the presence of sub-oxides detected by XPS.