Porous anodic oxides on titanium and on a Ti-W alloy

The growth of a nanoporous anodic oxide on titanium and a Ti-20 at.% W alloy, both deposited by magnetron sputtering, in a glycerol/phosphate electrolyte at 453 K is reported. The oxide formed on titanium is a mixture of amorphous titania and anatase. However, that on the alloy is amorphous only and forms at increased efficiency, about 27%. The amorphous structure is considered to be stabilized by incorporated units of WO₃, which are distributed uniformly throughout the anodic film. The growth of the porous oxides is suggested to be associated with loss of film species at the film/electrolyte interface at the base of pores, with new oxide forming exclusively at the metal/film interface by inward migration of O²⁻ ions.