Special Issue "Nanostructured Anodic Oxides: Fabrication, Characterization and Application"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: 1 July 2020.

Special Issue Editor

Dr. Wojciech J. Stepniowski
Website
Guest Editor
Department of Materials Science and Engineering, Lehigh University, 5 East Packer Avenue, Bethlehem, PA 18015, USA
Department of Advanced Materials & Technologies, Military University of Technology, Kaliskiego 2 Str. 00908 Warsaw, Poland
Interests: anodization; nanostructured anodic oxides; anodic aluminum oxide; anodic oxides on copper; nanofabrication; CO2 reduction reaction

Special Issue Information

Dear Colleagues,

The anodization of metals, especially aluminum, has been widely utilized in corrosion engineering during the last few decades. Anodic alumina provides insulation, compact layering, and corrosion protection. Since 1995, when Masuda and Fukuda from Tokyo Metropolitan University published their groundbreaking paper reporting two-step anodization of aluminum, anodization has become one of the most researched techniques in nanotechnology. Two-step, self-organized anodizing has allowed for the formation of highly ordered, uniform nanopores with morphologies that can be tuned by operating conditions. Such formed material serves as a template for the nanofabrication of nanowires, nanotubes, and nanodots made of a variety of materials.

Today, other metals and alloys, such as titanium, zinc, zirconium, copper, iron, and cobalt, are anodized. Moreover, these nanostructured oxides contribute to emerging applications, such as CO2 reduction, solar cells, sensing, and implant materials.

The forthcoming Special Issue will focus on recent advancements in the field of nanostructured anodic oxides. Topics include, but are not limited to:

  • Fundamental and mechanistic issues of anodizing;
  • Characterization of chemical composition, geometry, and arrangement of anodically grown oxides;
  • Study of the influence of operating conditions of anodizing on oxide growth;
  • New experimental conditions for anodizing;
  • Anodization of new metals and alloys;
  • Study of the properties of anodically grown oxides;
  • Applications of anodically grown oxides.

We invite our colleagues to contribute full papers, reviews, or communications to this Special Issue.

Dr. Wojciech J. Stepniowski
Guest Editor

Manuscript Submission Information

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Keywords

  • anodization
  • self-organization
  • nanotechnology
  • nanopores
  • nanowires
  • nanotubes
  • passivation
  • nanofabrication
  • corrosion
  • electrochemistry

Published Papers (4 papers)

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Research

Open AccessArticle
TiO2 Nanotubes with Pt and Pd Nanoparticles as Catalysts for Electro-Oxidation of Formic Acid
Materials 2020, 13(5), 1195; https://doi.org/10.3390/ma13051195 - 06 Mar 2020
Abstract
In the present work, the magnetron sputtering technique was used to prepare new catalysts of formic acid electrooxidation based on TiO2 nanotubes decorated with Pt (platinum), Pd (palladium) or Pd + Pt nanoparticles. TiO2 nanotubes (TiO2 NTs) with strictly defined [...] Read more.
In the present work, the magnetron sputtering technique was used to prepare new catalysts of formic acid electrooxidation based on TiO2 nanotubes decorated with Pt (platinum), Pd (palladium) or Pd + Pt nanoparticles. TiO2 nanotubes (TiO2 NTs) with strictly defined geometry were produced by anodization of Ti foil and Ti mesh in a mixture of glycerol and water with ammonium fluoride electrolyte. The above mentioned catalytically active metal nanoparticles (NPs) were located mainly on the top of the TiO2 NTs, forming ‘rings’ and agglomerates. A part of metal nanoparticles decorated also TiO2 NTs walls, thus providing sufficient electronic conductivity for electron transportation between the metal nanoparticle rings and Ti current collector. The electrocatalytic activity of the TiO2 NTs/Ti foil, decorated by Pt, Pd and/or Pd + Pt NPs was investigated by cyclic voltammetry (CV) and new Pd/TiO2 NTs/Ti mesh catalyst was additionally tested in a direct formic acid fuel cell (DFAFC). The results so obtained were compared with commercial catalyst—Pd/Vulcan. CV tests have shown for carbon supported catalysts, that the activity of TiO2 NTs decorated with Pd was considerably higher than that one decorated with Pt. Moreover, for TiO2 NTs supported Pd catalyst specific activity (per mg of metal) was higher than that for well dispersed carbon supported commercial catalyst. The tests at DFAFC have revealed also that the maximum of specific power for 0.2 Pd/TiO2 catalyst was 70% higher than that of the commercial one, Pd/Vulcan. Morphological features, and/or peculiarities, as well as surface composition of the resulting catalysts have been studied by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and chemical surface analytical methods (X-ray photoelectron spectroscopy—XPS; Auger electron spectroscopy—AES). Full article
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Open AccessFeature PaperArticle
A Superhydrophilic Aluminum Surface with Fast Water Evaporation Based on Anodic Alumina Bundle Structures via Anodizing in Pyrophosphoric Acid
Materials 2019, 12(21), 3497; https://doi.org/10.3390/ma12213497 - 25 Oct 2019
Abstract
A superhydrophilic aluminum surface with fast water evaporation based on nanostructured aluminum oxide was fabricated via anodizing in pyrophosphoric acid. Anodizing aluminum in pyrophosphoric acid caused the successive formation of a barrier oxide film, a porous oxide film, pyramidal bundle structures with alumina [...] Read more.
A superhydrophilic aluminum surface with fast water evaporation based on nanostructured aluminum oxide was fabricated via anodizing in pyrophosphoric acid. Anodizing aluminum in pyrophosphoric acid caused the successive formation of a barrier oxide film, a porous oxide film, pyramidal bundle structures with alumina nanofibers, and completely bent nanofibers. During the water contact angle measurements at 1 s after the water droplet was placed on the anodized surface, the contact angle rapidly decreased to less than 10°, and superhydrophilic behavior with the lowest contact angle measuring 2.0° was exhibited on the surface covered with the pyramidal bundle structures. As the measurement time of the contact angle decreased to 200–33 ms after the water placement, although the contact angle slightly increased in the initial stage due to the formation of porous alumina, at 33 ms after the water placement, the contact angle was 9.8°, indicating that superhydrophilicity with fast water evaporation was successfully obtained on the surface covered with the pyramidal bundle structures. We found that the shape of the pyramidal bundle structures was maintained in water without separation by in situ high-speed atomic force microscopy measurements. Full article
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Open AccessArticle
Cubic Silver Nanoparticles Fixed on TiO2 Nanotubes as Simple and Efficient Substrates for Surface Enhanced Raman Scattering
Materials 2019, 12(20), 3373; https://doi.org/10.3390/ma12203373 - 16 Oct 2019
Abstract
In this work we show that ordered freestanding titanium oxide nanotubes (TiO2 NT) may be used as substrates for the simple and efficient immobilization of anisotropic plasmonic nanoparticles. This is important because anisotropic plasmonic nanostructures usually give greater spectral enhancement than spherical [...] Read more.
In this work we show that ordered freestanding titanium oxide nanotubes (TiO2 NT) may be used as substrates for the simple and efficient immobilization of anisotropic plasmonic nanoparticles. This is important because anisotropic plasmonic nanostructures usually give greater spectral enhancement than spherical nanoparticles. The size of the pores in a layer of titanium oxide nanotubes can be easily fitted to the size of many silver plasmonic nanoparticles highly active in SERS (surface-enhanced Raman scattering) spectroscopy (for example, silver nanocubes with an edge length of ca. 45 nm), and hence, the plasmonic nanoparticles deposited can be strongly anchored in such a titanium oxide substrate. The tubular morphology of the TiO2 substrate used allows a specific arrangement of the silver plasmonic nanoparticles that may create many so-called SERS hot spots. The SERS activity of a layer of cubic Ag nanoparticles (AgCNPs) deposited on a tubular TiO2 substrate ([email protected]2 NT) is about eight times higher than that of the standard electrochemically nanostructured surface of a silver electrode (produced by oxidation reduction cycling). Furthermore, a super hydrophilic character of the TiO2 nanotubes surface allows for a uniform distribution of AgCNPs, which are deposited from an aqueous suspension. The new [email protected]2 NT hybrid layer ensures a good reproducibility of SERS measurements and exhibits a higher temporal stability of the achievable total SERS enhancement factor—one that is far better than standard SERS silver substrates. To characterize the morphology and chemical composition of such evidently improved SERS platforms thus received, we applied microscopic techniques (SEM, and scanning transmission electron microscopy (STEM)) and surface analytical techniques (Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS)). Full article
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Open AccessArticle
Formation of Nanoporous Mixed Aluminum-Iron Oxides by Self-Organized Anodizing of FeAl3 Intermetallic Alloy
Materials 2019, 12(14), 2299; https://doi.org/10.3390/ma12142299 - 18 Jul 2019
Cited by 1
Abstract
Nanostructured anodic oxide layers on an FeAl3 intermetallic alloy were prepared by two-step anodization in 20 wt% H2SO4 at 0 °C. The voltage range was 10.0–22.5 V with a step of 2.5 V. The structural and morphological characterizations of [...] Read more.
Nanostructured anodic oxide layers on an FeAl3 intermetallic alloy were prepared by two-step anodization in 20 wt% H2SO4 at 0 °C. The voltage range was 10.0–22.5 V with a step of 2.5 V. The structural and morphological characterizations of the received anodic oxide layers were performed by field emission scanning electron microscopy (FE-SEM). Therefore, the formed anodic oxide was found to be highly porous with a high surface area, as indicated by the FE-SEM studies. It has been shown that the morphology of fabricated nanoporous oxide layers is strongly affected by the anodization potential. The oxide growth rate first increased slowly (from 0.010 μm/s for 10 V to 0.02 μm/s for 15 V) and then very rapidly (from 0.04 μm/s for 17.5 V up to 0.13 μm/s for 22.5 V). The same trend was observed for the change in the oxide thickness. Moreover, for all investigated anodizing voltages, the structural features of the anodic oxide layers, such as the pore diameter and interpore distance, increased with increasing anodizing potential. The obtained anodic oxide layer was identified as a crystalline FeAl2O4, Fe2O3 and Al2O3 oxide mixture. Full article
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