Through-hole Anodic Aluminum Oxide Research Articles

Electrochemical Separation of Porous Anodic Aluminum Oxide with Thick Barrier Layers

We investigated an electrochemical separation method for anodic aluminum oxide (AAO) films possessing thicker barrier layers by electrolysis in sodium chloride (NaCl) and ethylene glycol (EG) solution and subsequent fabrication of through-hole AAO membranes by immersion in phosphoric acid (H3PO4) solution. The AAO films with different barrier layer thicknesses were formed on the aluminum surface by anodizing in sulfuric, oxalic, and H3PO4 solutions at up to 130 V. The AAO-covered aluminum specimens were immersed in NaCl/EG solution, and then constant voltage electrolysis at 10 V higher than the anodizing voltage was performed for the separation of AAO from the aluminum surface. Many nanoscale paths were formed throughout the barrier alumina layer in the initial stage of electrolysis, and then the aluminum substrate electrochemically dissolved through these narrow paths during electrolysis. Although the AAO film formed by anodizing at 130 V was partially fractured by electrolysis, the AAO films formed at up to 80 V were uniformly separated from the aluminum surface. As the separated AAO membrane was immersed in H3PO4 aqueous solution after electrolysis, the barrier layer with narrow paths preferentially dissolved into the solution, and a through-hole AAO membrane could be successfully obtained.

High Anti-Reflection Large-Scale Cup-Shaped Nano-Pillar Arrays via Thin Film Anodic Aluminum Oxide Replication.

Surface anti-reflection (AR) with nanometer-scaled texture has shown excellent light trapping performance involving optical devices. In this work, we developed a simple and lithography-free structure replication process to obtain large scale surface cup-shaped nano-pillar (CSNP) arrays for the first time. A method of depositing was used for pattern transfer based on PMMA pre-coated through-hole anodic aluminum oxide (AAO) thin film (~500 nm), and eventually, the uniformity of the transferred nanostructures was guaranteed. From the spectrum (250 nm~2000 nm) dependent measurements, the CSNP nanostructured Si showed excellent AR performance when compared with that of the single-polished Si. Moreover, the CSNP was found to be polarization insensitive and less dependent on incidence angles (≤80°) over the whole spectrum. To further prove the excellent antireflective properties of the CSNP structure, thin film solar cell models were built and studied. The maximum value of Jph for CSNP solar cells shows obvious improvement comparing with that of the cylinder, cone and parabola structured ones. Specifically, in comparison with the optimized Si3N4 thin film solar cell, an increment of 54.64% has been achieved for the CSNP thin film solar cell.

Cost-effective technique to fabricate a tubular through-hole anodic aluminum oxide membrane using one-step anodization

In order to reduce the time required to prepare a tubular through-hole anodic aluminum oxide (AAO) membrane, this study improved the manufacturing processes using one-step anodization. AAO membranes were first prepared by using 6063 commercial aluminum alloy tubes using an external anodizing method. The manufacturing processes for a tubular through-hole AAO membrane include: annealing, physically wet grinding, buff wheel polishing, ultrasonic cleaning, one-step anodizing, aluminum substrate removing, and barrier layer alumina (BLA) etching. The influence of chemical etching time on the nanostructure of AAO membranes was observed by a Field Emission Scanning Electron Microscope (FE-SEM). The results of the fabrication of a tubular through-hole AAO membrane showed that increasing the chemical etching time of the BLA etching process could result in an enhanced nanotube pore size and a reduced AAO membrane thickness, and excessive chemical etching time would collapse the nanotube structure. The tubular through-hole AAO membrane obtained was straight nanotubes with a thickness of 48 μm and an average bottom pore size of 109 nm.

A CO2-gated anodic aluminum oxide based nanocomposite membrane for de-emulsification.

A carbon-dioxide-responsive organic-inorganic nanocomposite membrane based on a through-hole anodic aluminum oxide (AAO) template was constructed. The composite was prepared via a surface-initiated reversible addition-fragmentation chain-transfer (SI-RAFT) polymerization strategy to achieve the grafting of poly(methyl methacrylate-co-2-(diethylamino)ethyl methacrylate) brushes on the AAO membrane. The grafted polymer chain length could be controlled based on the feed ratio between the free chain transfer agent (CTA) and reactive monomer, e.g., methyl methacrylate and 2-(diethylamino)ethyl methacrylate, resulting in a membrane that features adjustable water permeability. Importantly, the membrane pore size and surface wettability could be switched from hydrophobic to hydrophilic upon the introduction of carbon dioxide and nitrogen gases. This allowed for the nanocomposite membrane to be utilized for controlled water flux and oil/water emulsion separation. The simple fabrication methodology as well as sustainable gaseous stimulus will be useful for the construction of future smart membranes.

Preparations of an inorganic-framework proton exchange nanochannel membrane

In this work, a proton exchange membrane composed of straight and aligned proton conducting nanochannels is developed. Preparation of the membrane involves the surface sol-gel method assisted with a through-hole anodic aluminum oxide (AAO) template to form the framework of the PEM nanochannels. A monomolecular layer (SO3H(CH2)3Si(OCH3)3) is subsequently added onto the inner surfaces of the nanochannels to shape a proton-conducting pathway. Straight nanochannels exhibit long range order morphology, contributing to a substantial improvement in the proton mobility and subsequently proton conductivity. In addition, the nanochannel size can be altered by changing the surface sol-gel condition, allowing control of the active species/charge carrier selectivity via pore size exclusion. The proton conductivity of the nanochannel membrane is reported as high as 11.3 mS cm−1 at 70 °C with a low activation energy of 0.21 eV (20.4 kJ mol−1). First-principle calculations reveal that the activation energy for proton transfer is impressively low (0.06 eV and 0.07 eV) with the assistance of water molecules.

Preparation of BST nanotube and its infrared absorption properties

Ba0.6Sr0.4TiO3 (BST) nanotubes are fabricated successfully by sol-sel method with the through-hole anodic aluminum oxide (AAO) template for the first time so far as we know. This fabrication method is easy to realize at low cost because the through-hole AAO template and the BST sol can be acquired easily at low cost, so this is very valuable in the fabrication of other similar nanostructures. First, the steady BST sol is prepared and the well aligned through-hole anodic aluminum oxide template is fabricated by a two-step anodization method; second, the BST sol is introduced into the ordered nanohole arrays of the through-hole AAO template by dipping and spinning; and finally, the samples are fired in air at 650℃ for 1 h to get BST nanotubes. X ray diffraction (XRD) patterns reveal that the BST nanotubes are of cubic perovskite structures, and grow mainly along [110] crystal orientation. Scanning electron microscope (SEM) results show that the thickness and pore size of the through-hole AAO template are about 16 μm and 75 nm, respectively. The length, external and inner diameters of the BST nanotubes are about 16 μm, 75 nm and 50 nm, respectively. Measurements of BST nanotubes give results highly matched with that of the through-hole AAO template. Fourier transform infrared spectroscopy (FTIR) results shows that in the 1350-1650 cm-1 waveband, the composite structure of AAO/BST nanotubes has two obvious absorption peaks which are respectively at 1470 and 1550 cm-1, while the BST film does not have; the absorption property of the composite structure is about two times of the pure through-hole AAO membrane. Finally, the possible reasons of this phenomenon about infrared absorption are discussed.

Fabrication of Anodic Aluminum Oxide Template and Copper Nanowire Surface Fastener

Through-hole anodic aluminum oxide (AAO) was fabricated by two steps anodization method. The pore diameter of the AAO was 40 nm. Cu nanowire array was prepared using the fabricated AAO as a template by electrochemical deposition. The mechanical and electrical performances of Cu nanowire surface fastener (NSF) were realized by the interconnection of Cu nanowire arrays. The shear and normal bonding strengths for the Cu NSF with 40 nm diameter nanowires were 3.38 × 10−3 and 2.46 × 10−3 N/cm2, respectively, and the parasitic resistance of it was approximately 22.5 Ω · cm2.

Performance of through-hole anodic aluminum oxide membrane as a separator for lithium-ion battery

A high porosity through-hole anodic aluminum oxide (AAO) membrane has been prepared by a two-step anodization procedure. The as-prepared AAO membrane is around 60μm thick with a uniform pore size of about 80nm. Moreover, we also found that the AAO membrane not only has a good mechanical strength but also shows better performances on electrolyte infiltration and retention compared with the commercial polymer separator. The LiFePO4/graphite battery using the AAO separator exhibits better cycling stability, rate capability and low-temperature performance than those using the polymer separators. The excellent electrochemical performances can be attributed to good hydrophilic characteristic, high porosity and through-pore structure of the AAO separators used. Therefore, the AAO separator is very promising to be applied in lithium-ion batteries.

Fabrication and wetting characteristics of vertically self-aligned ZnO nanorods formed by anodic aluminum oxide template

The growth of vertically self-aligned ZnO nanorods in an anodic aluminum oxide (AAO) template is investigated, along with their wetting characteristics. The highly ordered through-hole AAO template was pre- pared from an aluminum foil of 99.95% purity in a mixed solution of phos- phoric and oxalic acids at 160 V at 1°C, and the resulting pore diameter and channel length are 250 nm and 2 μm, respectively. The vertically self- aligned ZnO nanorods produced with AAO template show the wetting transition time from hydrophobic to superhydrophilic under UV illumination in 9 min. This fast transition time is attributed to the high surface area to volume ratio of the ZnO nanorods and the adsorption enhancement of water molecules by UV-generated electron-hole pairs. © 2014 Society of

PH sensors based on polypyrrole nanowire arrays

The hydroquinone monosulfonate-doped polypyrrole (PPy-HQS) nanowires were successfully fabricated by potentiostatic electropolymerization of pyrrole (Py) inside the pores of home-made through-hole anodic aluminum oxide (AAO) membranes. The AAO templates with a nominal pore diameter of 80nm were prepared by a two-step anodization process. The potentiostatic electropolymerization of HQS-doped polymer nanowires was carried out in 0.1M NaClO4, or 0.1M LiClO4 or 0.1M citric acid containing 0.05M pyrrole and 0.05M potassium hydroquinone monosulfonate. The synthesized PPy-HQS nanowire arrays were tested as potential potentiometric pH sensors. It was found that pH sensors based on PPy-HQS nanowires exhibited better electrochemical performance toward pH sensing than those based on PPy-HQS thin films. The best potentiometric response to pH changes and a very good stability in time showed the sensor based on the PPy-HQS nanowires polymerized in a 0.1M LiClO4 solution.

The nanoporous structure of anodic aluminum oxide fabricated on the Au/Nb/Si substrate

We have studied the anodization behavior of an Al film evaporated on the Au/Nb/Si substrate and demonstrated an effective approach to fabricate the through-hole anodic aluminum oxide (AAO) template on the conducting substrate. The smoothness of the initial metal films and an appropriate wet etching of the oxide film anodized in the first step were found to be critical factors for successfully anodizing the Al film on Au surface. The barrier layer of the obtained AAO structure presented a convex and thinner characteristic, and the underlying Au surface became porous after the anodization. This phenomenon was similar to the case of anodizing the Al film on an ITO glass substrate and could be explained reasonably by the effect of high pressure O 2 gas impelling and H + etching at the interface of the barrier oxide and the Au layer.