Nanoindentation study of the mechanical behavior of TiO2 nanotube arrays.

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