High-density NiTiO3/TiO2 nanotubes synthesized through sol–gel method using well-ordered TiO2 membranes as template

Free-standing and well-ordered TiO2 membranes were prepared by two-step anodization in F−-containing ethylene glycol electrolytes at voltage of 60 V. It was found that the ordering of TiO2 membranes was significantly improved after the second anodization process. The initially closed bottom side of TiO2 membranes was opened through chemical etching to obtain two-end opened TiO2 membranes. Using the two-end opened membranes as template, dense NiTiO3/TiO2 nanotubes were successfully prepared for the first time by a sol–gel method. The microstructure and morphologies of the samples were characterized by scanning and the transmission electron microscopy techniques.