Self-organized porous titanium oxide prepared in Na2SO4/NaF electrolytes

The anodic formation of nanoporous TiO2 on titanium was investigated in Na2SO4 electrolytes containing low concentrations of NaF (0.1–1 wt.%). It was found that under optimized electrolyte conditions and extended polarization, a self-organized nanostructure consisting of porous TiO2 is obtained. The porous structure is arranged in sections of arrays with single pore diameters of typically 100 nm and an average spacing of 150 nm. The pores are open at the top and covered by oxide at the bottom. Compared with earlier work, we show that using a neutral NaF electrolyte significantly thicker porous layers can be obtained than in acidic solutions.