Influence of Water Content on the Growth of Anodic TiO[sub 2] Nanotubes in Fluoride-Containing Ethylene Glycol Electrolytes

The effect of water additions, from , to an ammonium fluoride/ethylene glycol electrolyte on the composition and morphology of titania-based nanotubes was investigated by scanning and transmission electron microscopy, Rutherford backscattering spectroscopy, and nuclear reaction analysis. Further to the presence of units of , the films contained fluorine, carbon, nitrogen, and probably hydrogen species derived from the electrolyte. The compositions of the films appeared to be relatively independent of the water content of the electrolyte. Following a small increase in efficiency of film growth for additions between 0 and water, the efficiency decreased from about 25 to about 10% between water contents of 1 and , respectively, possibly due to a combination of loss of titanium species to the electrolyte and evolution of oxygen. The densities of the nanotube layers were estimated to be in the range of , with an average value of .