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It has recently been found that the anodizing of FeAl alloys allows the formation of iron-aluminum oxide layers with interesting semiconducting properties. However, the lack of systematic research on different anodizing regimes is hampering their full exploitation in numerous photoelectrochemical-related applications. This study address, for the first time, the systematic effect of the electrolyte composition on the formation of self-ordered oxide films by anodizing on cast Fe3Al alloy. The Fe3Al alloy was anodized in 3 electrolytes with different water-ethylene glycol (EG) ratios (pure water, 25 vol.%-EG, and 50 vol.%-EG solutions) at a constant tartaric-sulfuric acids concentration, different voltages (10–20 V) and treatment times (2–60 min). After anodizing, all anodic oxide layers were annealed at 900 °C to form semiconductive iron-aluminum crystalline phases. Conventional techniques were used to systematically ascertain the morphological (SEM/EDS, XRD, eddy-current measurements) and semiconductive (UV–VIS reflectance spectroscopy) properties of these oxide layers. The results confirmed the formation of homogeneous and self-ordered anodic oxide layers at 10 and 15 V, regardless of the electrolyte composition. Namely, anodic films formed in electrolytes containing EG showed lower pore sizes, growth rates, and film thicknesses than those anodic films formed in the aqueous-based electrolyte. The annealing post-treatment results in different Fe-Al oxides (FexOy, FeAl2O4, etc.) with superior band gap values than those for non-annealed films. [ABSTRACT FROM AUTHOR]

We report fabrication of anodic titanium oxide nanotubes with rippled sidewalls using anodization of titanium foil in an ethanol-based electrolyte containing ammonium fluoride and water. The electrolyte was tested at 40 °C and at potential in the 30–60 V range. The internal diameter of nanotubes grows linearly from 88 nm for 30 V up to 124 nm for 50 V and next drops to 105 nm for 60 V. The thickness of anodic titanium oxide layer exceeds 1 μm. Presence of NH 4 F crystals in electrolyte is favorable for formation of nanotubes. The unusual shape of current curves during anodization was observed. [ABSTRACT FROM AUTHOR]

Titania nanotubes or nanopores self-ordered on electrochemically anodized (EA) titanium have been widely applied towards photocatalysis, solar cells, purification and biomedical implants. As a result, significant research has been focused towards optimizing anodization to fabricate controlled, stable and reproducible nanostructures. Among these, the use of organic-based electrolyte, like ethylene glycol (with NH 4 F and water), to anodize Ti has been widely applied and researched. Interestingly, among the various influencing EA factors, electrolyte aging (repeated EA using non-target Ti, prior to EA of target Ti substrate) has been underexplored, with only few studies aiming to optimize electrolyte aging and its influence on the nanostructures fabricated. Moreover, many research laboratories utilize electrolyte aging in Ti anodization, but this practice is seldom reported. In this extensive and pioneering review, we discuss and detail electrolyte aging in Ti anodization to fabricate controlled nanostructures, and its influence on nanostructure characteristics including morphology, chemistry, stability and application-specific performance. This review will inform future research aimed at optimizing electrolyte aging and Ti anodization to fabricate controlled nanostructures catering to specific application needs. [Display omitted] • Anodization of Ti enables fabrication of TiO 2 nanostructures for varied applications • Electrolyte aging involves repeated use of same electrolyte prior to anodizing target Ti • Aging of organic electrolytes is routinely practised for Ti anodization but seldom reported • This review discusses and details the basics and advances in electrolyte aging • Influence of aging on the characteristics and performance of TiO 2 nanotubes is discussed [ABSTRACT FROM AUTHOR]