Large-Scale Fabrication of Ordered Nanoporous Alumina Films with Arbitrary Pore Intervals by Critical-Potential Anodization

Chu, Song-Zhu; Wada, Kenji; Inoue, Satoru; Isogai, Masafumi; Katsuta, Y.; Yasumori, Atsuo

doi:10.1149/1.2218822

Cited by 246 publications

(251 citation statements)

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“…18,30 In order to confirm that the morphological defects guided pore initiation is not a special case in this kind of electrolyte, anodization is also conducted in more frequently-used acidic solutions. Figure S3 shows the morphologies of oxide films anodized in 4 wt % citric acid aqueous solution 30 (pH ∼ 1.5) under 300 V and 400 V. The unpolished Al foils still result in PAA films (Figure S3a and c), while BAA films (Figure S3b and d) are obtained on the polished Al foils under the same conditions. The same results are also observed in diluted oxalic acid solutions (0.3 M aqueous solution diluted by ethanol (1:8 in volume)) under 500 V and 600 V as shown in Figure S4a-d. Chu et al have also reported this morphology evolution in malic acid solutions.…”

Section: Resultsmentioning

confidence: 99%

“…The same results are also observed in diluted oxalic acid solutions (0.3 M aqueous solution diluted by ethanol (1:8 in volume)) under 500 V and 600 V as shown in Figure S4a-d. Chu et al have also reported this morphology evolution in malic acid solutions. 30 In their experiments conducted in 2 wt % malic acid with a fixed voltage of 450 V, PAA and BAA are obtained on Al foil with naturally formed grooves and sputtered Al film on FTO/glass substrate with a smooth surface, respectively. They attributed the formation of barrier-type films to the temperature increase caused by the Joule heat produced at the ultrahigh anodizing potential.…”

Section: Resultsmentioning

confidence: 99%

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Morphology Defects Guided Pore Initiation during the Formation of Porous Anodic Alumina

Yang

Huang

Lin

et al. 2014

ACS Appl. Mater. Interfaces

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Aluminum (Al) anodization leads to formation of porous structures with a broad spectrum of applications. Naturally or intentionally created defects on Al surfaces can greatly affect pore initiation. However, there is still a lack of systematic understanding on the defect dependent morphology evolution. In this paper, anodization processes on unpolished, polished, and nanoimprinted Al substrates are investigated under high voltages up to 600 V in various acid solutions. A porous structure is obtained on the unpolished and nanoimprinted Al foils with rough surface texture, whereas a compact film can be rationally obtained on the polished Al foil with a highly smooth surface. The observation of surface roughness dependent oxide film morphology evolution could be originated from the high voltages, which increases the threshold requirement of defect size or density for the pore initiation. Electrostatics simulation results indicate that inhomogeneous electric field and its corresponding localized high current induced by the surface roughness facilitate the initiation of nanopores. In addition, the porous films are utilized as templates to produce polydimethylsiloxane nanocone and submicrowire arrays. The nanoarrays with different aspect ratios present tunable wettability with the contact angles ranging from 144.6°to 56.7°, which hold promising potentials in microfluidic devices and self-cleaning coatings.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Morphology Defects Guided Pore Initiation during the Formation of Porous Anodic Alumina

Yang

Huang

Lin

et al. 2014

ACS Appl. Mater. Interfaces

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“…The diameter of the nanodimples corresponds to the cell size (or interpore distance) of the anodic porous alumina. In general, there is linear relation between the anodizing voltage and the cell size formed by anodizing, and the relation is described as follows [45]: D = 2.5 V (2) where D is the cell size. Figure 6b) shows the change in the cell size, D, with the anodizing voltage, V, measured by anodizing for 60 min at different current densities.…”

Section: Methodsmentioning

confidence: 99%

“…On the other hand, poorly arranged nanoporous structures are formed by chromic acid anodizing due to pore branching. Several carboxylic acids, including oxalic ((COOH) 2 ) [35][36][37][38], malonic (HOOC-CH 2 -COOH) [39][40][41], tartalic (HOOC-(CHOH) 2 -COOH) [42][43][44], citric (HOOC-CH 2 -C(OH)(COOH)-CH 2 -COOH) [45][46][47], malic (HOOC-CH(OH)-CH 2 -COOH) [45,48], glycolic (HOOC-CH 2 OH) [45], formic (HCOOH) [49], and tartronic (HOOC-CH(OH)-COOH) [50] acid have been reported to date for the fabrication of anodic porous alumina. Oxalic and malonic acid anodizing have been reported to give rise to self-ordering behavior under suitable anodizing conditions.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of anodic porous alumina via anodizing in cyclic oxocarbon acids

Kikuchi

Nakajima

Kawashima

et al. 2014

Applied Surface Science

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The growth behavior of anodic porous alumina formed by anodizing in novel electrolyte solutions, the cyclic oxocarbon acids croconic and rhodizonic acid, was investigated for the first time. High-purity aluminum specimens were anodized in 0.1 M croconic and rhodizonic acid solutions at various constant current densities. An anodic porous alumina film with a cell size of 200-450 nm grew uniformly on an aluminum substrate by rhodizonic acid anodizing at 5-40 Am -2 , and a black, burned oxide was formed at higher current density. The cell size of the porous alumina increased with current density and corresponding anodizing voltage. Anodizing in croconic acid at 293 K caused the formation of thin anodic porous alumina films as well as black, thick burned oxides. The uniformity of the porous alumina improved by increasing the temperature of the croconic acid solution, and anodic porous alumina films with a uniform film thickness were successfully obtained. Our experimental results showed that the cyclic oxocarbon acids croconic and rhodizonic acid could be employed as a suitable electrolyte for the formation of anodic porous alumina films.Key words: Aluminum; Anodizing; Anodic Porous Alumina; Croconic Acid; Rhodizonic Acid IntroductionThe anodizing of aluminum in several different acidic solutions causes the formation of anodic porous alumina (i.e., porous anodic oxide film) with characteristic nanofeatures on aluminum substrates. Porous alumina consists of nano-scale hexagonal cells perpendicular to the substrate, and each cell possesses a nanopore at its center [1,2]. These cells are self-ordered by anodizing under appropriate electrochemical conditions, especially under a high electric field [3,4]. When anodic porous alumina is immersed in boiling distilled water after anodizing, the nanopores are filled by hydroxide (pore-sealing) [5,6]. The sealing process causes the formation of a highly crystalline hydroxide layer on the surface of the anodic oxide, and the hydroxide layer is highly dissolution-resistant in acidic and alkaline solutions. Using these characteristic structural and chemical properties, anodic porous alumina has been widely investigated for many applications: antireflection structures [7,8] [50] acid have been reported to date for the fabrication of anodic porous alumina. Oxalic and malonic acid anodizing have been reported to give rise to self-ordering behavior under suitable anodizing conditions. The organic and inorganic electrolytes used to fabricate anodic porous alumina possess low dissociation constant (pKa) in aqueous solution, except for glycolic and formic acid, are diacids or triacids. However, glycolic and formic acid form dimers via hydrogen bonding in aqueous solution and may behave like diacids [52,53]. The nanofeatures of anodic porous alumina, including cell size (i.e., interpore distance) and pore diameter, are limited by these electrolytes during anodizing. Therefore, the discovery of additional electrolytes is very important in expanding the applicability of porous alum...

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“…Cyclic oxocarbonic acids such as squaric [24], croconic, and rhodizonic [25] acid were very recently determined to be suitable organic electrolytes for fabricating porous alumina, although the details of the growth behavior are still unknown. Carboxylic acids can also be employed as suitable electrolytes for fabricating porous alumina, including oxalic [26,27], malonic [28,29], citric [30,31], malic [32], acetylenedicarboxylic [33], tartaric [34,35], tartronic [36], glycolic [37], and formic [38] acid. Because the nanostructural features and chemical properties of anodic porous alumina are determined and limited by the electrolyte used [39], the discovery of a new suitable electrolyte would expand the applicability of porous alumina.…”

Section: Introductionmentioning

confidence: 99%

Growth behavior of anodic oxide formed by aluminum anodizing in glutaric and its derivative acid electrolytes

Nakajima

Kikuchi

Natsui

2014

Applied Surface Science

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The growth behavior of anodic oxide films formed via anodizing in glutaric and its derivative acid solutions was investigated based on the acid dissociation constants of electrolytes. High-purity aluminum foils were anodized in glutaric, ketoglutaric, and acetonedicarboxylic acid solutions under various electrochemical conditions. A thin barrier anodic oxide film grew uniformly on the aluminum substrate by glutaric acid anodizing, and further anodizing caused the film to breakdown due to a high electric field. In contrast, an anodic porous alumina film with a submicrometer-scale cell diameter was successfully formed by ketoglutaric acid anodizing at 293 K. However, the increase and decrease in the temperature of the ketoglutaric acid resulted in non-uniform oxide growth and localized pitting corrosion of the aluminum substrate. An anodic porous alumina film could also be fabricated by acetonedicarboxylic acid anodizing due to the relatively low dissociation constants associated with the acid. Acid dissociation constants are an important factor for the fabrication of anodic porous alumina films.Keywords: Aluminum; Anodizing; Glutaric Acid; Ketoglutaric Acid; Acetonedicarboxylic Acid IntroductionAnodic porous alumina with numerous vertical, nano-scale pores can easily be fabricated via aluminum anodizing in several types of acidic aqueous solutions and has been widely applied in the fields of corrosion protection and electronic applications [1][2][3][4][5][6]. In particular, the development of highly ordered anodic porous alumina, which is fabricated via self-ordering and two-step anodizing under appropriate electrochemical conditions, has expanded the applicability of porous alumina [7]. Accordingly, plasmonic devices [8], antireflection polymer structures[9], optical devices [10], and high-density recording media [11] have been successfully fabricated through the combination of methods for developing highly ordered anodic porous alumina and other nanostructure fabrication techniques.The electrolyte species used for anodic porous alumina fabrication can be specifically classified into the following three groups: inorganic, organic cyclic oxocarbonic, and organic carboxylic acids. It is a well-known experimental fact that anodic porous alumina can be formed by anodizing in these acidic electrolytes, which provide low acid dissociation constants. To date, sulfuric [12][13][14][15][16], selenic [17,18], phosphoric [19,20], and chromic[21] acids have been reported as useful inorganic electrolytes for fabricating anodic porous alumina. The ideal cell arrangement of porous alumina can be achieved via sulfuric, selenic, and phosphoric acid anodizing, whereas poorly ordered porous alumina is fabricated via chromic acid anodizing [22,23]. Cyclic oxocarbonic acids such as squaric [24], croconic, and rhodizonic[25] acid were very recently determined to be suitable organic electrolytes for fabricating porous alumina, although the details of the growth behavior are still unknown. Carboxylic acids can also be employed ...

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Large-Scale Fabrication of Ordered Nanoporous Alumina Films with Arbitrary Pore Intervals by Critical-Potential Anodization

Cited by 246 publications

References 28 publications

Morphology Defects Guided Pore Initiation during the Formation of Porous Anodic Alumina

Morphology Defects Guided Pore Initiation during the Formation of Porous Anodic Alumina

Fabrication of anodic porous alumina via anodizing in cyclic oxocarbon acids

Growth behavior of anodic oxide formed by aluminum anodizing in glutaric and its derivative acid electrolytes

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