A novel nanostructure fabricated by an improved two-step anodizing technology

Zhu, Xufei; Song, Ye; Yu, Dongliang; Zhang, Chang-Shan; Yao, Wei

doi:10.1016/j.elecom.2013.01.018

Cited by 101 publications

(122 citation statements)

References 33 publications

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“…We have proposed that the formation of oxide film is determined by J ion , and J e gives rise to the evolution of oxygen gas which is responsible to the pore formation. 2,16,17,28 The ionic current (J ion ) and the electric field strength (E) are related through the exponential law 13,19 …”

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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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%

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 detailed description may consult our previous works. [36][37][38]41 The ionic current and the electronic current are interdependent and independent, and they are a couple of driving forces during the formation of TiO 2 nanotubes. [36][37][38][39][40][41] Distributional diagram of the electric currents through three parts of the electrochemical cell (i.e., the electrolyte, the metal anode and the growing oxide) and the formation mechanism of the nanotubes were detailed in our previous works, 38,41 and here, the entire surface layer covered on the nanotube arrays will be mainly focused on.…”

Section: Resultsmentioning

confidence: 99%

“…[34][35][36] The model and conclusion of the papers above were reinforced by our subsequent works. [37][38][39][40][41] In 2012, the theoretical expressions for time dependent ionic current and electronic current were successfully derived from the anodizing processes of aluminum and titanium, 37 many questions proposed by Diggle's and Hebert's groups 7,18,30 could be successfully elucidated in our recent works, [36][37][38][39][40][41] such as, the correlation between dissolution rate and anodizing current, dissolution nature, dissolution balance and constant barrier layer, the correlation between the porous morphology and current-time curve (three stages). The complicated growth kinetics could be also quantitatively explained by the ionic current and the electronic current.…”

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confidence: 99%

“…The complicated growth kinetics could be also quantitatively explained by the ionic current and the electronic current. 4,37,38,41 That is, the ionic current is used to form the barrier oxide and the electronic current is used to give rise to oxygen gas at the critical thickness. The oxygen bubble is the precondition of the oxide flow from the pore base to the pore wall.…”

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Formation Mechanism of Gaps and Ribs Around Anodic TiO₂Nanotubes and Method to Avoid Formation of Ribs

Chong

Gao

et al. 2015

J. Electrochem. Soc.

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Anodic TiO 2 nanotubes (ATNTs) have been studied extensively for many years. However, their mysterious formation mechanism still remains unclear. The formation of gaps and ribs around the nanotubes has not been elucidated. Here, various surface and cross-section morphologies of ATNTs obtained under different anodizing conditions and their evolution process have been investigated in detail. Based on many experimental facts, new explanations for the gaps and ribs are presented. An entire surface layer covered on the nanotubes plays a primary role on the formation of gaps and ribs. The gaps result from the radial distribution of the electric field at the pore bottom. No newly-formed oxide will exist along the gap direction, because the electric filed along the gap is the minimum. The ribs result from the electrolyte entering into the wider gaps among the ATNTs due to the rupture of the entire surface layer. The rings or ribs on the outer wall of ATNTs are formed at the electrolyte/Ti interface due to the discontinuous existence of a small amount of electrolyte within the gap base. The present viewpoint was demonstrated by an original micro-dam, which can block the electrolyte entering into the gaps and avoid the formation of ribs.

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“…The controllable regimes of the pore interspacing and diameters are rather limited to some tens percentage due to the narrow potential ranges used. More recently, Zhu et al 27 and Liu et al 28 reported a newly approach to fabricate two-or four-layered PAA films with increased pore intervals by changing electrolytes and electrolytic parameters (current densities or voltages) for each layer. Nevertheless, the voltage ratios were unintentionally set as designed (e.g., at 25, 40, 108, 195 V) and the ratios of pore interval among the layers (e.g., 1.6, 2.3, 1.9) could not be accurately controlled, thus endowing less-ordered 3D porous alumina nanostructures with mismatched pore channels at the layer interfaces.…”

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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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A novel nanostructure fabricated by an improved two-step anodizing technology

Cited by 101 publications

References 33 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

Formation Mechanism of Gaps and Ribs Around Anodic TiO₂Nanotubes and Method to Avoid Formation of Ribs

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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A novel nanostructure fabricated by an improved two-step anodizing technology

Cited by 101 publications

References 33 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

Formation Mechanism of Gaps and Ribs Around Anodic TiO2Nanotubes and Method to Avoid Formation of Ribs

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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Formation Mechanism of Gaps and Ribs Around Anodic TiO₂Nanotubes and Method to Avoid Formation of Ribs