Structural Features of Crystalline Anodic Alumina Films

Uchi, Hidenori; Kanno, T.; Alwitt, Robert S.

doi:10.1149/1.1344528

Cited by 76 publications

(49 citation statements)

References 17 publications

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“…Barrier anodic oxide films and porous anodic oxide films on aluminum have been widely investigated by many researchers in the fields of surface finishing [1][2][3], electrolytic capacitor application [4][5][6], and micro-and nano-structure fabrication [7][8][9]. Recently, highly ordered anodic porous alumina with a cell size on the scale of 10-100 nm has been studied for potential use in various ordered-nanostructure applications [10][11][12][13][14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Self-Ordering Behavior of Anodic Porous Alumina via Selenic Acid Anodizing

Kikuchi

Nishinaga

Natsui

et al. 2014

Electrochimica Acta

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The self-ordering behavior of anodic porous alumina that was formed by anodizing in selenic acid electrolyte (H 2 SeO 4 ) at various concentrations and voltages was investigated with SEM and AFM imaging. A high purity aluminum foil was anodized in 0.1-3.0 M selenic acid solutions at 273 K and at constant cell voltages in the range of 37 to 51 V. The regularity of the cell arrangement increased with increasing anodizing voltage and selenic acid concentration under conditions of steady oxide growth without burning. Anodizing at 42-46 V in 3.0 M selenic acid produced highly ordered porous alumina. By selective dissolution of the anodic porous alumina, highly ordered convex nanostructures of aluminum with diameters of 20 nm and heights of 40 nm were exposed at the apexes of each hexagonal dimple array. Highly ordered anodic porous alumina with a cell size of 102 nm from top to bottom can be fabricated by a two-step selenic acid anodizing process, that includes the first anodizing step, the selective oxide dissolution, and the second anodizing step.Key words: Aluminum; Anodizing; Anodic Porous Alumina; Selenic Acid IntroductionBarrier anodic oxide films and porous anodic oxide films on aluminum have been widely investigated by many researchers in the fields of surface finishing [1][2][3], electrolytic capacitor application [4][5][6], and micro-and nano-structure fabrication [7][8][9]. Recently, highly ordered anodic porous alumina with a cell size on the scale of 10-100 nm has been studied for potential use in various ordered-nanostructure applications [10][11][12][13][14][15][16][17][18][19][20][21]. Anodic porous alumina is typically fabricated on an aluminum substrate using electrochemical anodizing (or anodization) [22][23][24][25][26]. In several acidic electrolyte solutions, the porous alumina fabricated by anodizing is self-ordered when prepared at the appropriate electrochemical conditions, including appropriate concentrations, temperatures, and voltages (or electrochemical potentials) [27][28][29][30] [50], and acetylenedicarboxylic (HOOC-C≡C-COOH) [51] acids have also been reported as electrolytes used to fabricate porous alumina that has characteristic nanostructure morphologies.In addition to these acidic electrolytes, alkaline and neutral solutions used for porous alumina fabrication were reported by several research groups. Takahashi et al. reported that a porous anodic oxide film could be formed by anodizing in an H 3 BO 3 /Na 2 B 4 O 7 neutral borate solution at a high temperature [52]. Baron-Wiechec et al. investigated aluminum anodizing in a borax (Na 2 B 4 O 7 ) solution at 333 K and successfully obtained porous alumina [53]. Noguchi et al. investigated the anodizing behavior of aluminum in propylenediamine and choline alkaline solutions containing ammonium fluoride, ammonium tartrate, ammonium carbonate, and ammonium tetraborate, and obtained anodic porous alumina with nanopores that were 10-150 nm in diameter [54]. However, it is difficult to form a highly ordered porous alumina by anodiz...

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Section: Introductionmentioning

confidence: 99%

Self-Ordering Behavior of Anodic Porous Alumina via Selenic Acid Anodizing

Kikuchi

Nishinaga

Natsui

et al. 2014

Electrochimica Acta

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“…[22] However, we found that if the anodization duration is increased, the ions eventually get transported across the barrier layer and generate sub-pores. Figure 4c depicts the anodization time needed to generate sub-pores through a barrier layer thickness of 115 AE 5 nm when using a potential ratio ranging from 0.50 to 0.96 (65-125 V).…”

Section: Resultsmentioning

confidence: 78%

“…All these factors in turn limit the breakdown potential. [22] To establish the influence of these factors in tiered pore formation, we analyzed systematically and quantitatively each parameter. For this purpose, we employed Design of Experiment (DoE) methodology to determine the most significant parameter (main effect) or joint effect for the generation of successive tiered sub-pores.…”

Section: Resultsmentioning

confidence: 99%

Controlled Fabrication of Multitiered Three‐Dimensional Nanostructures in Porous Alumina

Gao

Lam

et al. 2008

Adv Funct Materials

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We present the fabrication of multitiered branched porous anodic alumina (PAA) substrates consisting of an array of pores branching into smaller pores in succeeding tiers. The tiered three‐dimensional structure is realized by sequentially stepping down the anodization potential while etching of the barrier layer is performed after each step. We establish the key processing parameters that define the tiered porous structure through systematically designed experiments. The characterization of the branched PAA structures reveals that, owing to constriction, the ratio of interpore distance to the anodization potential is smaller than that for pristine films. This ratio varies from 1.8 to 1.3 nm V−1 depending on the size of the preceding pores and the succeeding tier anodization potential. Contact angle measurements show that the multitiered branched PAA structures exhibit a marked increased in hydrophilicity over two‐dimensional PAA films.

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“…Aluminum anodizing in neutral solutions results in the formation of a thin dense barrier oxide that can be as thick as 1 µm on the aluminum substrate [4,5]. Barrier oxides have been widely used for electrolytic capacitor applications due to their high dielectric property [6][7][8]. In contrast, aluminum anodizing in acidic solutions including inorganic, carboxylic, cyclic oxocarbonic, and bisphosphonate acid results in the formation of porous oxide that can be as thick as several hundred µm [9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of a novel aluminum surface covered by numerous high-aspect-ratio anodic alumina nanofibers

Nakajima

Kikuchi

Natsui

et al. 2015

Applied Surface Science

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The formation behavior of anodic alumina nanofibers via anodizing in a concentrated pyrophosphoric acid under various conditions was investigated using electrochemical measurements and SEM/TEM observations. Pyrophosphoric acid anodizing at 293 K resulted in the formation of numerous anodic alumina nanofibers on an aluminum substrate through a thin barrier oxide and honeycomb oxide with narrow walls. However, long-term anodizing led to the chemical dissolution of the alumina nanofibers. The density of the anodic alumina nanofibers decreased as the applied voltage increased in the 10 to 75 V range. However, active electrochemical dissolution of the aluminum substrate occurred at a higher voltage of 90 V.Low temperature anodizing at 273 K resulted in the formation of long alumina nanofibers measuring several micrometers in length, even though a long processing time was required due to the low current density during the low temperature anodizing. In contrast, high temperature anodizing easily resulted in the formation and chemical dissolution of alumina nanofibers. The structural nanofeatures of the anodic alumina nanofibers were controlled by choosing of the appropriate electrochemical conditions, and numerous high-aspect-ratio alumina nanofibers (>100) can be successfully fabricated. The anodic alumina nanofibers consisted of a pure amorphous aluminum oxide without anions from the employed electrolyte.

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Structural Features of Crystalline Anodic Alumina Films

Cited by 76 publications

References 17 publications

Self-Ordering Behavior of Anodic Porous Alumina via Selenic Acid Anodizing

Self-Ordering Behavior of Anodic Porous Alumina via Selenic Acid Anodizing

Controlled Fabrication of Multitiered Three‐Dimensional Nanostructures in Porous Alumina

Fabrication of a novel aluminum surface covered by numerous high-aspect-ratio anodic alumina nanofibers

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