Anodizing-induced cracking in the preparation of TiO₂ nanotube arrays

Understanding structural integrity of physical structures in chemical and electrochemical systems/environments is of practical importance in analyzing and predicting the reliability and lifespan of the physical structures. In this work, we systematically investigate the crack growth in the TiO₂ layers with TiO₂ nanotube arrays during electrochemical anodization of Ti plates without external mechanical loading. There exists the combinational effects of the anodization voltage and the anodization temperature on the crack growth. A simple relationship between the growth rate of the areal crack density, the anodization temperature and the anodization voltage are proposed and supported by the experimental results. The growth rate of the areal density of the surface cracks increases with the increase of the anodization voltage and the anodization temperature. The nominal activation energy is a decreasing function of the anodization voltage, suggesting that increasing the anodization voltage promotes fast growth of the surface cracks in the TiO₂ oxide layer.