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Zhang J, Zhao H, Gong M, Zhang L, Yan Z, Xie K, Fei G, Zhu X, Kong M, Zhang S, Zhang L, Lei Y. Revealing the truncated conical geometry of nanochannels in anodic aluminium oxide membranes. NANOSCALE 2022; 14:5356-5368. [PMID: 35293409 DOI: 10.1039/d2nr01006b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Anodic aluminium oxide (AAO) membranes with self-ordered nanochannels have become promising candidates for applications in the aspects such as structural coloration, photonic crystals, upconversion luminescence and nanofluidic transport. Also, self-ordered AAO membranes have been extensively used for the fabrication of functional nanostructures such as nanowires, nanotubes, nanoparticles, nanorods and nanopillars. Geometries of nanochannels are crucial for the applications of AAO membranes as well as controlling growth (e.g., nucleation, direction and morphology) and in applications (e.g., optics, magnetics, thermoelectrics, biology, medicine, sensing, and energy conversion and storage) of the functional nanostructures fabricated via AAO template-based methods. However, observation of whole nanochannels with nanometer-resolution in thick AAO membranes remains a fundamental challenge, and the nanochannel geometry has not yet been sufficiently elucidated. Here, for the first time, we use depth-profiling transmission electron microscopy to reveal the truncated conical geometry of whole nanochannels of 70 μm in length. Such shape nonuniformity of the nanochannels leads to different reflectance properties of the different depths of the nanochannels along their long axis for one AAO membrane, which suggests that the nonuniformity result in some effects on applications of the nanostructures. Furthermore, we introduce a shape factor to evaluate the shape nonuniformity and demonstrate that the nonuniformity can be remarkably removed by an effective etching method based on a temperature gradient regime.
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Affiliation(s)
- Junxi Zhang
- School of Instrument Science and Opto-electronics Engineering, Anhui Key Laboratory of Advanced Functional Materials and Devices, and Anhui Province Key Laboratory of Measuring Theory and Precision Instrument, Hefei University of Technology, Hefei 230009, China.
| | - Huaping Zhao
- Institute of Physics & IMN MacroNano, Ilmenau University of Technology, Ilmenau 98693, Germany.
| | - Ming Gong
- Laboratory of Engineering and Material Science, University of Science and Technology of China, Hefei 230027, China
| | - Lide Zhang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China
| | - Zhijun Yan
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Kang Xie
- School of Opto-Electronic Engineering, Zaozhuang University, Zaozhuang 277160, Shandong, China
| | - Guangtao Fei
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China
| | - Xiaoguang Zhu
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China
| | - Mingguang Kong
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China
| | - Shuyuan Zhang
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Lin Zhang
- Aston Institute of Photonic Technologies, School of Engineering & Applied Science, Aston University, Birmingham B4 7ET, UK
| | - Yong Lei
- Institute of Physics & IMN MacroNano, Ilmenau University of Technology, Ilmenau 98693, Germany.
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Brudzisz AM, Giziński D, Stępniowski WJ. Incorporation of Ions into Nanostructured Anodic Oxides-Mechanism and Functionalities. Molecules 2021; 26:molecules26216378. [PMID: 34770787 PMCID: PMC8587705 DOI: 10.3390/molecules26216378] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/13/2021] [Accepted: 10/20/2021] [Indexed: 11/17/2022] Open
Abstract
Anodic oxidation of metals leads to the formation of ordered nanoporous or nanotubular oxide layers that contribute to numerous existing and emerging applications. However, there are still numerous fundamental aspects of anodizing that have to be well understood and require deeper understanding. Anodization of metals is accompanied by the inevitable phenomenon of anion incorporation, which is discussed in detail in this review. Additionally, the influence of anion incorporation into anodic alumina and its impact on various properties is elaborated. The literature reports on the impact of the incorporated electrolyte anions on photoluminescence, galvanoluminescence and refractive index of anodic alumina are analyzed. Additionally, the influence of the type and amount of the incorporated anions on the chemical properties of anodic alumina, based on the literature data, was also shown to be important. The role of fluoride anions in d-electronic metal anodizing is shown to be important in the formation of nanostructured morphology. Additionally, the impact of incorporated anionic species, such as ruthenites, and their influence on anodic oxides formation, such as titania, reveals how the phenomenon of anion incorporation can be beneficial.
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Correlation between Defect Density and Corrosion Parameter of Electrochemically Oxidized Aluminum. COATINGS 2019. [DOI: 10.3390/coatings10010020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
It has been recognized that a connection may exist between defects of oxide coating and its corrosion protection. Such a link has not been substantiated. We prepare two coatings of anodized aluminum oxide (AAO) and plasma electrolytic oxidation (PEO), and analyze them with Mott-Schottky plots and potentiodynamic polarization scans. The as-grown and annealed AAO coatings exhibit both p-type and n-type semiconductor behaviors. Polarization resistance of the AAO coating increases from (1.8 ± 1.7) × 108 to (4.3 ± 0.5) × 108 Ω·cm2, while corrosion current decreases from (6.1 ± 3.6) × 10−7 to (2.3 ± 0.9) × 10−7 A·cm−2, as annealing temperature increases from room temperature to 400 °C. The parameter analysis on AAO indicates a positive correlation between corrosion current and donor density, a negative correlation between polarization resistance and donor density. The attempt on correlating corrosion potential gives rise to considerable deviation from a linear fit. The results suggest protection of AAO hinges on its donor density, not acceptor. On the PEO coatings, only the n-type behavior is observed. Intriguingly, the donor density of PEO coating is influenced by the annealing temperature of its pre-anodized layer. The most resistant PEO coating, with pre-anodized and 400 °C annealed AAO, exhibits polarization resistance (2.1 ± 0.4) × 109 Ω·cm2 and corrosion current (1.7 ± 0.4) × 10−8 A·cm−2.
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