Characterization of TiO2 nanotubes produced by anodization in ethylene glycol-H2O electrolyte

Abstract

The formation of self-organized TiO2 nanotubes has been widely studied in the past decade due to their promising potential applications, such as photocatalysts, gas sensors, solar cells and biomaterials. Among the fabrication routes to produce nanotubes, anodization was generally preferred due to its simplicity. This method consists in applying a voltage between titanium and an inert cathode (generally platinum) immersed in an electrolyte containing fluorides. TiO2 nanotubes are formed by the simultaneous anodic reaction and chemical dissolution due to the fluoride species. In this work, the formation of TiO2 nanotubes was investigated in stirred ethylene glycol-H2O electrolyte (90-10 v/v) containing NH4F at room temperature. In order to study the effect of NH4F concentration, voltage and anodization time, and to reduce the number of experiments, a design of experiments (dOE) based on a 2k factorial design with four replicates at the center point was used. ANOVA was used to evaluate the effects of the factors of control and their interactions on the percentage of the titanium surface coated by nanotubes (R response). For the analysis of the oxide films, a field emission scanning electron microscope was used. ANOVA showed that the NH4F concentration is the most significant factor for R response. The best condition according to the response surface analysis is the center point (1%NH4F, 20V, 2h).