Nanoindentation study of the mechanical behavior of TiO2 nanotube arrays

Titanium dioxide (TiO2) nanotube arrays are attracting increasing attention for use in solar cells,\udlithium-ion batteries, and biomedical implants. To take full advantage of their unique physical\udproperties, such arrays need to maintain adequate mechanical integrity in applications. However, the\udmechanical performance of TiO2 nanotube arrays is not well understood. In this work, we investigate\udthe deformation and failure of TiO2 nanotube arrays using the nanoindentation technique. We found\udthat the load–displacement response of the arrays strongly depends on the indentation depth and\udindenter shape. Substrate-independent elastic modulus and hardness can be obtained when the\udindentation depth is less than 2.5% of the array height. The deformation mechanisms of TiO2\udnanotube arrays by Berkovich and conical indenters are closely associated with the densification of\udTiO2 nanotubes under compression. A theoretical model for deformation of the arrays under a largeradius\udconical indenter is also proposed