Self-ordering Regimes of Porous Alumina:  The 10 Porosity Rule

Nielsch, Kornelius; Choi, Jinsub; Schwirn, Kathrin; Wehrspohn, Ralf B.; Gösele, U.

doi:10.1021/nl025537k

Cited by 998 publications

(978 citation statements)

References 19 publications

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“…Anodic porous alumina, which is fabricated by anodization of aluminum with pore sizes in the range of tens to hundreds of nanometers and arranged in a quasi periodic hexagonal pattern, [1][2][3] has been extensively studied for use as an excellent template material for fabricating nano-structured materials, such as nano-wire arrays, 4 nano-tubes, 5 nano-capacitors, 6 and photonic crystals. 7 In these applications, one usual requirement is that the arrangement of the pore-channels inside the porous alumina should be hexagonally self-ordered, and this means that the growth of the porechannels during aluminum anodization should be a self-ordering process 1, 2 with as infrequent splitting, merging or termination as possible.…”

Section: Introductionmentioning

confidence: 99%

Quantitative characterization of acid concentration and temperature dependent self-ordering conditions of anodic porous alumina

Cheng¹,

Ng²,

Ngan³

2011

AIP Advances

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Acid concentration and temperature dependent self-ordering conditions of anodic porous alumina formed by anodization of aluminum in oxalic acid are quantitatively characterized by a new technique involving the distribution of the angular orientation of the triangles formed by neighboring pore centers, in order to detect the self-ordering domains in each porous pattern. This technique is found to be more sensitive in quantifying ordering of the patterns than the radial distribution function and angle distribution function. Using this technique, the optimal acid concentration which can result in the best self-ordering of the porous alumina under a given temperature is established. The optimal acid concentration is found to be approximately linearly increasing with temperature. The oxide growth rate increases approximately exponentially with acid concentration and also with temperature. The results suggest that anodization conducted at relatively higher temperatures at the corresponding optimal acid concentrations can enable fast production of self-ordered anodic porous alumina for industrial applications.

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Section: Introductionmentioning

confidence: 99%

Quantitative characterization of acid concentration and temperature dependent self-ordering conditions of anodic porous alumina

Cheng¹,

Ng²,

Ngan³

2011

AIP Advances

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“…Porous anodized alumina (PAA) is one of the most exciting nanostructured material which has gained significant attention for applications in gas separation [1], drug delivery [2], bone fixation [3], and a template for nanostructures formation [4,5]. PAA membrane consists of an ordered hexagonal arrangement of cells with a central pore per cell that elongates from top to bottom of the layer, resembling a honeycomb network [6,7].…”

Section: Introductionmentioning

confidence: 99%

Formation of self-ordered porous anodized alumina template for growing tungsten trioxide nanowires

et al. 2014

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Uniform porous anodized aluminum oxide (AAO) membrane has been synthesized by two-step anodization for fabricating tungsten trioxide (WO 3 ) nanowires. Under assayed conditions, uniform porous structure of alumina (Al 2 O 3 ) membrane with long range ordered hexagonal arrangements of nanopores was achieved. The self-assembled template possesses pores of internal diameter of 50 nm and interpore distance (d int ) of 80 nm with a thickness of about 80 lm, i.e., used for fabrication of nanostructures. WO 3 nanowires have been fabricated by simple electroless deposition method inside Al 2 O 3 nanopores. SEM images show tungsten trioxide nanowire with internal diameter of about 50 nm, similar to porous diameter of AAO template. XRD results showed that nanowires exist in cubic crystalline state with minor proportion of monoclinic phase.

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“…38 In this study, the degree of self-assembly and the size and number of nanotubes in ATO were investigated in terms of thickness changes, considering that the diameter of AAO nanotubes is usually determined by the applied potential, and the degree of self-assembly linearly improves up to the diffusion limit length. 39 …”

Section: Introductionmentioning

confidence: 99%

Thickness Dependence of Size and Arrangement in Anodic TiO₂Nanotubes

Kim¹,

Lee²,

Choi³

2011

Bulletin of the Korean Chemical Society

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The degree of self-assembly and the size variation of nanotubular structures in anodic titanium oxide prepared by the anodization of titanium in ethylene glycol containing 0.25 wt % NH4F at 40 V were investigated as a function of anodization time. We found that the degree of self-assembly and the size of the nanotubes were strongly dependent on thickness deviation and thus indirectly on anodization time, as the thickness deviation was caused by the dissolution of the topmost tubular structures at local areas during long anodization. A large deviation in thickness led to a large deviation in the size and number of nanotubes per unit area. The dissolution primarily occurred at the bottoms of the nanotubes (Dbottom) in the initial stage of anodization (up to 6 h), which led to the growth of nanotubes. Dissolution at the tops (Dtop) was accompanied by Dbottom after the formed structures contacted the electrolyte after 12 h, generating the thickness deviation. After extremely long anodization (here, 70 h), Dtop was the dominant mode due to increase in pH, meaning that there was insufficient driving force to overcome the size distribution of nanotubes at the bottom. Thus, the nanotube array became disorder in this regime.

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Self-ordering Regimes of Porous Alumina: The 10 Porosity Rule

Cited by 998 publications

References 19 publications

Quantitative characterization of acid concentration and temperature dependent self-ordering conditions of anodic porous alumina

Quantitative characterization of acid concentration and temperature dependent self-ordering conditions of anodic porous alumina

Formation of self-ordered porous anodized alumina template for growing tungsten trioxide nanowires

Thickness Dependence of Size and Arrangement in Anodic TiO₂Nanotubes

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Self-ordering Regimes of Porous Alumina: The 10 Porosity Rule

Cited by 998 publications

References 19 publications

Quantitative characterization of acid concentration and temperature dependent self-ordering conditions of anodic porous alumina

Quantitative characterization of acid concentration and temperature dependent self-ordering conditions of anodic porous alumina

Formation of self-ordered porous anodized alumina template for growing tungsten trioxide nanowires

Thickness Dependence of Size and Arrangement in Anodic TiO2Nanotubes

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Thickness Dependence of Size and Arrangement in Anodic TiO₂Nanotubes