Influence of annealing on the structure of nanoporous oxide films on the surface of titanium‒aluminum powder alloy

Abstract

Oxide films obtained during anodization of Ti‒40% Al sintered powder samples in fluorine-containing electrolytes are investigated. With scanning electron microscopy and X-ray phase analysis, it is demonstrated that an X-ray amorphous nanoporous anodic oxide film is formed on the surface of the powder microparticles under optimal anodization conditions. After annealing at T = 1093 K in air and vacuum (10^‒2 Pa), the oxide films are revealed to crystallize with its regular porous structure retained. The composition of the polycrystalline anodic-oxide films annealed in air is a mixture involving TiO₂ (anatase and rutile) and α- and γ-Al₂O₃ phases and Ti₂O₃ and Al₂TiO₅ traces. The vacuum annealing process makes it possible to identify TiO₂, in which anatase is the main phase, α- and γ-Al₂O₃, and Ti₂O₃ and TiO traces. However, rutile is not revealed. The presented results indicate that the application of the anodic nanostructuring of Ti‒40% Al powders is promising for the obtainment of new photocatalytic active nanomaterials.