Zirconium oxide (ZrO2) is a widely utilized inorganic material with excellent dielectric, optical, and biocompatible characteristics. The properties and areas of the ZrO2 applications can be further broadened by making the material nanostructured. In this work, anodic ZrO2 nanostructured films were developed and characterized by scanning electron microscopy. The films were prepared by anodizing magnetron-sputtered Al/Zr bilayers in two regimes: galvanostatic/potentiostatic anodizing in (COOH)2 and H2SO4 solutions (anodized films) and that followed by the high-speed reanodizing to a significantly higher anodic voltage (reanodized films). The growth of a porous anodic alumina (PAA) layer followed by PAA-assisted oxidation of the Zr underlayer was achieved. The anodized films consist of arrays of self-organized spatially ordered ZrO2 nanohillocks while the reanodized films comprise arrays of vertically aligned ZrO2 nanorods. The growth of amorphous ZrO2 nanohillocks and nanorods within the alumina pores via migration of Zr4+ cations is a unique situation for anodic films on zirconium, which normally grow crystalline and by O2- anion transport at the oxide/metal interface only. The achievement is a milestone towards understanding the ion transport during the PAA-assisted anodization of valve metals with low cation transport numbers.Keywords: anodizing, zirconium oxide, porous anodic alumina, nanostructure, electron microscopy
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