Empirical kinetics for the growth of titania nanotube arrays by potentiostatic anodization in ethylene glycol

The goal of this research was to describe the effects of the main anodization variables on the morphology of the resulting titania nanotube arrays. Four variables were considered in this study: applied voltage, fluoride and water concentrations, and time. The first three variables were studied simultaneously in a central composite design of experiments using SEM measurements of tube length as the response variable. The effect of time was modeled using transferred charge as the response variable. A field assisted oxidation-dissolution growth model was validated over a broad range of experimental conditions under which tube growth can be accurately predicted directly from the current transients using Faraday's laws. The effects of anodization variables were described based on this model and a simple, empirical kinetic expression was obtained and successfully tested against data from other authors with fairly small errors over a broad range of conditions.