Zirconium oxide nanoarrays via the self-organized anodizing of Al/Zr bilayers on substrates

Abstract

A combination of frontier formation conditions, paradoxical oxide growth, unique ionic transport, a mixed-oxide composition, and phase transition effects resulted in arrays of novel self-assembled zirconium-oxide nanostructures.

Optical Properties of Porous Alumina Assisted Niobia Nanostructured Films–Designing 2-D Photonic Crystals Based on Hexagonally Arranged Nanocolumns

“…The formation voltage of 53 V is a compromise, since it makes it possible to obtain nanocolumns with a sufficient thickness and high degree of ordering, verticality, and reproducibility. In addition, the formation mode of columns at 50–53 V in the oxalic electrolyte is well studied, since it was repeatedly used to obtain nanocolumns of tantalum [ 112 , 122 , 123 , 124 ], niobium [ 117 , 125 ], hafnium [ 126 , 127 ], zirconium [ 128 ].…”

Nanostructured Zirconium‐Oxide Bioceramic Coatings Derived from the Anodized Al/Zr Metal Layers

“…Based on the SEM observations and with reference to previous works on anodizing and re-anodizing of Al layers superimposed on layers of different valve metals including Zr, [15,17,19,36] the growth of nanostructured zirconium-oxide films can be described as follows. The same starting Al/Zr bilayer was used for making all coatings examined in this study (Figure 2a).…”

“…The situation when the zirconium-oxide column-like protrusions grow within the narrow channels such are the alumina nanopores compete with the widening of the column bases due to the migration of O 2− ions. [36] The bases gradually merge since the progress of oxidation exposes more zirconium at the metal/film interface. The final voltage selected for re-anodizing of each film type was expected to make the zirconium-oxide protrusions well-differentiated, separated by a thin layer of zirconium oxide, and of an aspect ratio (length/ diameter) desired for the purpose of the present study, as modeled in the top row of Figure 2c-e. For preparing the flat coating, the Al layer was first dissolved away, then the Zr layer was anodized in the phosphoric acid electrolyte, as depicted in Figure 2b.…”

“…Due to the partial migration of zirconium ions through the outer layer of the alumina cell walls, a small portion of Al 2 O 3 might be present in the oxide nanostructures. [20,36] Other possible impurities in the anodic films are electrolyte-derived species such as anions resulting from dissociation of oxalic, phosphoric, or etidronic acids. [41][42][43] Furthermore, anodic zirconium oxide may include sub-stoichiometric oxides mixing with ZrO 2 at the atomic level.…”

“…The identification of the spectral components in C 1s, Zr 3d, P 2p, and Al 2p energy windows was performed strictly following the procedure described in the previous publication. [36] Figure 2. Modeling of anodic oxide growth during the anodizing/re-anodizing of a) an Al/Zr bilayer sputter-deposited on a SiO 2 /Si wafer: formation of b) a flat ZrO 2 film via aluminum dissolution and zirconium anodizing in 0.1 m phosphoric acid, c) a nanomound film via the PAA-assisted anodizing in 0.6 m oxalic acid followed by PAA dissolution, d) a nanopillar film via the PAA-assisted anodizing in 0.1 m phosphoric acid followed by PAA dissolution, e) a nanostump film via the PAA-assisted anodizing in 0.02 m phosphoric acid followed by PAA dissolution.…”