Growth of nanotubes on zirconium in glycerol/fluoride electrolytes

The study examines anodic films formed on bulk and sputtered zirconium in ammonium fluoride/glycerol electrolyte with up to 5 vol.% added water, using film cross-sections prepared by focused ion beam and ultramicrotomy. The findings indicate porous films consisting of zirconium fluoride surrounding zirconia-based nanotubes. The fluoride arises due to faster migration of F− ions relative to O2− ions; its dissolution exposes the nanotubes. Ion beam analyses revealed the highest amount of fluorine for films formed in electrolyte with no water addition. 18O tracer indicated that water was the primary source of oxygen in the films, which grew at an efficiency of ∼80%.