Processes Involved in Reattainment of Steady-State Conditions for the Anodizing of Aluminum Following Formation Voltage Changes

Diggle, John W.; Downie, T. C.; Goulding, Christopher

doi:10.1149/1.2412043

Cited by 19 publications

(12 citation statements)

References 12 publications

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“…It was suggested that the dissolution of AAO in electrolyte is ‘field-assisted’, or strongly dependent on voltage potential [14]. Figure 5 confirms the field-assisted nature of the AAO dissolution, as increasing the acid concentration does not increase aluminum oxide dissolution.…”

Section: Discussionmentioning

confidence: 57%

“…It was also proposed that self-ordering requires a porosity of 10% which is independent of the specific anodization conditions and corresponds to aluminum of about 1.2 [13]. The mechanism by which pores grow is still in debate, but pore formation models have been developed [14–18]. The pore opening of the bottom layer or barrier layer removal is also considered an important step towards making a through-hole porous anodic alumina membrane.…”

Section: Introductionmentioning

confidence: 99%

“…Earlier literature describes thickness as simply a function of total charge passed to the anode [13,14]. However, others have found that thickness varies with anode geometry.…”

Section: Introductionmentioning

confidence: 99%

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Effect of processing parameters on pore structure and thickness of anodic aluminum oxide (AAO) tubular membranes

Belwalkar

Grasing

Geertruyden

et al. 2008

Journal of Membrane Science

227

117

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Nanoporous anodic aluminum oxide (AAO) tubular membranes were fabricated from aluminum alloy tubes in sulfuric and oxalic acid electrolytes using a two-step anodization process. The membranes were investigated for characteristics such as pore size, interpore distance and thickness by varying applied voltage and electrolyte concentration. Morphology of the membranes was examined using light optical and scanning electron microscopy and characterized using ImageJ software. Results showed that membranes having narrow pore size and uniform pore distribution with parallel channel arrays were obtained. The pore sizes were ranging from 14 to 24 nm and the wall thicknesses as high as 76 µm. It was found that the pore size increased in direct proportion with the applied voltage and inversely with the electrolyte concentration while the interpore distance increased linearly with the applied voltage. It was also observed that increase in acid concentration increased tubular membrane wall thickness that improved mechanical handling. By using anodic alumina technology, robust ceramic tubes with uniformly distributed pore-structure and parallel nano-channels of lengths and sizes practical for industrial applications were reliably produced in quantity.

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Section: Discussionmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of processing parameters on pore structure and thickness of anodic aluminum oxide (AAO) tubular membranes

Belwalkar

Grasing

Geertruyden

et al. 2008

Journal of Membrane Science

227

117

View full text Add to dashboard Cite

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“…25,26 In our experiment, when SiO 2 mask was introduced on the Al surface, a considerably thick barrier layer was intentionally formed in the SiO 2 -covered region, where the minimum electric field for ionic migration cannot be achieved. 27 Therefore, the oxidation of Al starts …”

Section: Resultsmentioning

confidence: 99%

Anodizing Behavior of Aluminum Foil Patterned with SiO[sub 2] Mask

Zhao

Jiang

Xie

et al. 2005

J. Electrochem. Soc.

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SiO 2 -patterned anodic aluminum oxide ͑AAO͒ is fabricated on the surface of aluminum ͑Al͒ foil by combining both photolithography and anodizing technique. Tilted pores and ridge-like features on the Al surface are observed under the SiO 2 mask by scanning electron microscopy characterization. A mechanism based on the deflection of electric field due to the existence of SiO 2 barrier on Al surface has been proposed to explain the observed anodizing behavior. Moreover, large-scale ordered metallic Al patterns are also revealed by removing the AAO film and SiO 2 mask.Anodic aluminum oxide ͑AAO͒, a kind of typical self-ordered nanochannel material, has been attracting continuous attention from interdisciplinary researchers due to its many potential technical applications. 1-4 The material, formed by anodizing aluminum ͑Al͒ in appropriate acid solution, is usually composed of many hexagonally arranged cells with cylindrical pores in the center. 5 The porous structure exhibits local ordered close-packed hexagonal arrays with alumina walls. These characters make AAO an ideal template to construct various one-dimensional ͑1D͒ nanoscaled materials including nanotubes and nanowires. [6][7][8][9] Design and realization of patterned porous material provide us many opportunities in practical applications such as in electronic devices, 10,11 photonic crystals, 12 microfluidic devices, 13 et al. Recently, Masuda and co-workers 14,15 reported a series of fabrications of highly ordered AAO structures with different pore shapes by patterning Al foils using nanoindentation technique. In their work, long-range-ordered AAO patterns with nanoscale pore diameter and special pore distance were fabricated by suitable pretexture of Al surfaces before anodizing. Although the research work from Masuda provides a promising approach to prepare large-area ordered AAO template, the fragility of AAO template still remains a big problem toward various applications. In order to address the challenge, Atanassov and co-workers 16,17 developed another method to indirectly pattern Al foil surfaces by using SiO 2 as a protecting mask. SiO 2 can exhibit good adhesion to the Al foil and prevent Al from being anodized by acidic electrolyte. The SiO 2 pattern used in their work was hundreds of micrometers wide and a few micrometers thick. Finally, patterned AAO nanopore arrays with intermittent Al supports were obtained and were supposed to enhance the mechanical strength of AAO template. In addition, they have also observed another phenomenon, the growth of tilted pores underneath the SiO 2 mask, but they did not give a reasonable explanation. In principle, the anodizing mechanism of AAO based on the electrical field distribution at pore tips has been generally accepted to explain the porous oxide growth. 18 Pore growth relies on the equilibrium of two processes. One is oxide dissolution at the oxide/electrolyte interface that was enhanced by electric field, and another is oxide growth at the metal/oxide interface. Further refined models and theories 19-...

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“…When the anodizing potential (U 1 ) is reduced abruptly to the potential (U 2 ), the anodizing current (j) drops to a very small value due to the sudden decrease of the electric field (E), and after a certain period of delay it slowly increases to a steady value dictated by U 2 . This phenomenon has been known as "current recovery" and attributed to the thinning of the barrier layer accompanied by branching of pores [30,141,142]. Since the movements of ions (i.e., Al 3+ and O 2− /OH − ) within the barrier oxide are governed by the electric field, the time required for complete current recovery increases with decreasing the field strength at the moment of potential drop [143,144].…”

Section: Potential Reductionmentioning

confidence: 99%

Structural Engineering of Porous Anodic Aluminum Oxide (AAO) and Applications

Lee

2015

Nanoporous Alumina

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Porous anodic aluminum oxide (AAO) films can be conveniently produced by anodization of aluminum. Porous oxide layer formed on aluminum contains a large number of mutually parallel pores. Each cylindrical nanopore and its surrounding oxide constitute a hexagonal cell aligned normal to the metal surface. Under proper conditions, the oxide cells are self-organized to form a hexagonally close-packed structure. The novel and tunable structural features of porous AAOs have been intensively exploited for templated synthesis of a variety of functional nanostructures and also for fabrication of nanodevices. On the other hand, porous AAOs with modulated pores may provide an additional degree of freedom in templated synthesis. In addition, they can be used as model systems for systematically investigating structure-property relations of nanostructured materials. Based on the anodization techniques developed recently, one can fabricate porous AAOs with tailor-made internal pore structures. This chapter is devoted to conveying the most recent advances in structural engineering of porous AAOs and nanotechnology applications. In order to provide context, a brief description is given of the general structure and fundamental electrochemical processes associated with pore formation. Subsequently, two common anodizing techniques (i.e., mild and hard anodizations) that have been explored for nanotechnology applications are discussed. Next, various nanostructuring approaches for custom-designed porous AAOs are reviewed. The chapter covers the properties of porous AAOs derived from structural engineering and their applications to various nanotechnology researches and finally presents the challenges and future prospects.

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Processes Involved in Reattainment of Steady-State Conditions for the Anodizing of Aluminum Following Formation Voltage Changes

Cited by 19 publications

References 12 publications

Effect of processing parameters on pore structure and thickness of anodic aluminum oxide (AAO) tubular membranes

Effect of processing parameters on pore structure and thickness of anodic aluminum oxide (AAO) tubular membranes

Anodizing Behavior of Aluminum Foil Patterned with SiO[sub 2] Mask

Structural Engineering of Porous Anodic Aluminum Oxide (AAO) and Applications

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