Impurity-driven defect generation in porous anodic alumina

Молчан, И. С.; Molchan, Tatsiana V.; Гапоненко, Н. В.; Skeldon, P.; Thompson, G.E.

doi:10.1016/j.elecom.2010.03.008

Cited by 54 publications

(64 citation statements)

References 18 publications

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“…of Ni into a unique 3D anodic aluminum oxide (AAO) template (Figure 1a), [15] obtained by one-step anodization of Al-1060 alloy in ethanol contained H 3 PO 4 electrolyte (Experimental Section). Contrary to the commonly used high purity Al (>99.99%) for 2D AAO formation ( Figure S2, Supporting Information), the impurity elements (e.g., Cu) within the alloy acted as active centers for oxygen evolution to form oxygen filled bubbles at the oxide/ metal interface during anodization.…”

Section: Doi: 101002/adma201600286mentioning

confidence: 99%

Fast and Reversible Actuation of Metallic Muscles Composed of Nickel Nanowire‐Forest

2016

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Surface-charge-induced reversible and millimeter-scale deflection is found in a bilayered Ni cantilever upon cyclic potential triggering. The nanowire-forest structure, in which unidirectional primary nanowires are evenly separated by cross-linking subnanowires, ensures fast ion transport leading to a record-high strain response time ≈0.1 s. The actuation is sustainable beyond 800 cycles; the strain energy is compatible with human skeletal muscles.

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Section: Doi: 101002/adma201600286mentioning

confidence: 99%

Fast and Reversible Actuation of Metallic Muscles Composed of Nickel Nanowire‐Forest

2016

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“…Similar to high-purity Al materials, 6 the thickness of the barrier layer of the PAA films was proportional to the anodizing voltage, increasing by 1.1 nm/V. Here, the variation of periodicity of transverse pores with anodizing voltage can be explained by formation mechanism proposed by Molchan et al 22 Because the defects or the initial branched pores are attributed to the enrichment of Cu impurity at the metal/film interface and the transportation to ridges of cell boundaries, the thickening of barrier layer and the increase of cell size of PAA films at high voltage delayed the rate of supply of Cu to triple points, thus leading to the increment of interspacing of transverse branched pores. Figure 6 shows the microstructures of PAA films formed on the 99.56% pure Al sheet in sulfuric, oxalic, and phosphoric acid solutions over a short period of 30 min.…”

Section: 6mentioning

confidence: 64%

“…Moreover, Skeldon et al recently reported the generation of defects or branched pores on the pore walls of PAA films by anodizing a commercial Al sheet (A1050-99.5%Al) and a Al-0.05%Cu sputtered film in phosphoric electrolytes, and proposed a mechanism that the formation of branched pores was related to the Cu component in Al base materials. 22, 23 Zaraska et al reported the effects of anode surface area on the oxide formation during anodizing of A1050 alloy in oxalic and sulfuric baths. 14,24,25 Chung et al, on the other hand, proposed a hybrid pulsed anodizing method to improve the pore distribution uniformity of nanoporous anodic aluminum oxide on low-purity aluminum foils.…”

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confidence: 99%

Controllable Fabrication of Networked Three-Dimensional Nanoporous Anodic Alumina Films on Low-Purity Al Materials

Kure‐Chu¹,

Osaka²,

Yashiro³

et al. 2014

J. Electrochem. Soc.

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Networked three-dimensional (3D) nanoporous alumina nanostructures-consisting of vertical cylindrical stem pore arrays (170-310 nm in diameter) and periodical transverse branched pores (20-80 nm in diameter) interspaced regularly by 190-220 nm across the vertical pore walls-were controllably fabricated from low purity Al materials (99.0%, 99.3%, and 99.56%) by anodization in a phosphoric acidic solution at 110-190 V. The formation of transverse pores depended predominantly on the purity of the Al base materials and the corrosion resistance of the anodic porous alumina films, which can be mainly attributed to anodic and/or chemical dissolution of impurities such as Fe, Cu, Zn, Mg, and Mn incorporated in the Al base materials. Moreover, the effects of the purity of Al materials on the growth and morphology of porous alumina films in oxalic and sulfuric acid solutions were also investigated by a two-step anodization of Al sheets with different purities, namely 99.0%, 99.3%, 99.56%, and 99.999% Al. The alumina films grew more slowly in all electrolytes with decreasing Al purity, which can be attributed to the lower corrosion resistance of the PAA films containing small quantities of Fe oxides and/or hydroxides produced during anodization. Porous anodic alumina (PAA) films with ordered parallel nanopore arrays obtained from Al anodization [1][2][3][4][5][6] have been widely used as nanotemplates in the past decade, to fabricate various one-dimensional (1D) nanostructures such as nanowires and nanotubes for many applications, including in photocatalysts, 7-10 perpendicular magnetic recording media, 11-14 and electrode catalysts, 15,16 and for solar energy conversion. 17 However, most studies so far have used Al with a purity greater than 99.99% as starting material to produce highly ordered porous structures. From the viewpoint of practical applications, using low-purity Al or Al alloy materials to fabricate nanoporous alumina nanostructures is highly desirable in terms of lowering costs and gaining satisfied mechanical strength.Recently, much effort has been dedicated to fabricating tailored nanoporous alumina films with varying pore diameters gradually or step-wise from high-purity Al foils (e.g., 99.997% Al), by means of changing the anodizing voltages or current densities, the electrolytes, temperature [18][19][20] or by using oscillatory currents, followed by chemical etching.21 However, to the best of our knowledge, there has been no report so far on the fabrication of 3D networked nanoporous alumina films with both vertical and transverse pores, whether from high-or low-purity Al materials. Moreover, Skeldon et al. recently reported the generation of defects or branched pores on the pore walls of PAA films by anodizing a commercial Al sheet (A1050-99.5%Al) and a Al-0.05%Cu sputtered film in phosphoric electrolytes, and proposed a mechanism that the formation of branched pores was related to the Cu component in Al base materials.22,23 Zaraska et al. reported the effects of anode surface area on the oxide formati...

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“…Also, it is known that the ordered regimes of pore arrangement for PAA films depended on many factors such as the crystal size (with or without annealing), 3 the critical anodizing potentials corresponding to the electrolytes, 4 and the purity of Al materials. [37][38][39] Therefore, the pore arrays of multi-tiered PAA films were normally less ordered near the grain boundaries of Al materials. Nevertheless, the present study depicted the possibility to fabricate ordered multilayered PAA nanostructures by stepwise anodization at designed pore interval ratios.…”

Section: Ecs Journal Of Solidmentioning

confidence: 99%

Facile Fabrication of Ordered Multi-Tiered Hierarchical Porous Alumina Nanostructures with Multiple and Fractional Ratios of Pore Interval toward Multifunctional Nanomaterials

Kure‐Chu

Osaka

Yashiro

et al. 2016

ECS J. Solid State Sci. Technol.

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Conventional nanoporous anodic alumina films are composed of one-tiered pore arrays that can only render to one-dimensional (1D) nano-structures if they are used as nano-templates. Hence, three-dimensional (3D) nanoporous alumina films are desirable to dramatically increase the variety of nanostructures by template-fabrication for various potentially enhanced performances. Herein we report a facile approach to fabricate a variety of ordered multi-tiered 3D porous alumina nanostructures with multiple integer (m = 2, 3, 4, 5, 7, 9, and 10) and fractional ratios (n = 1/2 and 1/3) of the pore interval and pore diameter among different tiers on ITO/glass and Al sheets. The multi-tiered nanostructures and the pore interval ratios of the neighboring tiers can be accurately and independently controlled by a tailored multiple stepwise anodization, successively in appropriate acidic electrolytes of sulfuric, oxalic, and/or phosphoric solutions at designed voltages of 15-180 V, corresponding to the multiple or fractional ratios of pore interspacing. Moreover, the multi-tiered hierarchical nanoporous alumina films on ITO/glass substrates exhibited a lower transmittance compared with that of the single-tiered films with ordered cylindrical pores, which can be attributed to the diffusive reflection from the tier interface with different pore intervals. In past decades, porous anodic alumina (PAA) films have attracted considerable attention in both scientific and technical applications owing to the unique geometric structure with ordered hexagonal arrays of cylindrical nano-pores, similar to a nano-scaled honeycomb.1-4 In recent years, PAA nanostructures have been extensively used as a core nanotemplate to fabricate various one-dimensional (1D) functional nanostructures, such as nanowires 5-9 and nanotubes, 10-14 which can be used in a wide variety of applications including DNA and gas sensors, electro-chromic devices, light-emitting diodes, field emitters, super-capacitors, nano-electronic devices, and nano-generators. In order to facilitate the functional integration of nanostructures, template synthesis is evolving towards the fabrication of nanomaterials with increasing geometric complexity, i.e., going from two-dimensional (2D) to three-dimensional (3D) nanostructures. However, a major challenge in obtaining 3D nanostructures is the prior fabrication of ordered 3D nanoporous template with independently controllable size, spacing, position, and shape of the pore arrays as required for various applications.Many studies so far have attempted to fabricate various porous alumina nanostructures with variable pore diameters using tailored anodization methods assisted by chemical dissolution at different operating temperatures. Lee at al. reported first on the fabrication of ordered PAA films with variable pore diameters from 40 to 59 nm by combining mild anodization (MA) with hard anodization (HA) in oxalic acidic electrolytes. 15 This approach was further developed to achieve 3D PAA films with shaped pore geometries in periodic...

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Impurity-driven defect generation in porous anodic alumina

Cited by 54 publications

References 18 publications

Fast and Reversible Actuation of Metallic Muscles Composed of Nickel Nanowire‐Forest

Fast and Reversible Actuation of Metallic Muscles Composed of Nickel Nanowire‐Forest

Controllable Fabrication of Networked Three-Dimensional Nanoporous Anodic Alumina Films on Low-Purity Al Materials

Facile Fabrication of Ordered Multi-Tiered Hierarchical Porous Alumina Nanostructures with Multiple and Fractional Ratios of Pore Interval toward Multifunctional Nanomaterials

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