• Journal of Surface Science and Engineering
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• v.51 no.1
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• pp.11-20
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• 2018

Hydrophobic and Superhydrophobic surfaces are promising technology for the surface finishing of metallic materials due to its water-repellency. Realization of highly water-repellent surface on aluminum and its alloys provides various functionalities for real application fields. In order to realize the hydrophobic/superhydrophobic surfaces on aluminum and its alloys, various technologies have been demonstrated. Especially, traditional anodic oxidation for aluminum has been widely employed for the morphological texturing of surfaces, which is essential to enhance the hydrophobic efficiency. De-wetting superhydrophobic surface on aluminum provides various exceptional properties, such as anti-corrosion, anti-/de-icing, anti-biofouling, drag reduction, self-cleaning and liquid separation. Nevertheless, the durability and stability of superhydrophobic surfaces still remain challenges for their actual applications in engineering systems and industry. In this review, the theoretical/experimental studies and current technical limitations on the hydrophobic and superhydrophobic surface using anodic oxidation of aluminum have been summarized.

• Journal of Electrochemical Science and Technology
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• v.3 no.1
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• pp.35-43
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• 2012

Highly ordered and perforated anodic aluminum oxide membranes were prepared by anodic oxidation and subsequent removal of the barrier layer. By using these homemade anodic aluminum oxide membranes as templates, metal selenide nanowires and nanotubes were synthesized. The structure and composition of these one-dimensional nanomaterials were studied by field emission scanning electron microscopy as well as transmission electron microscopy and energy dispersive X-ray spectroscopy. The growth process of metal selenide inside anodic aluminum oxide channel was traced by investigating the series of samples using scanning electron microscopy after reacting for different times. Straight and dense copper selenide and silver selenide nanowires with a uniform diameter were successfully prepared. In case of nickel selenide, nanotubes were preferentially formed. Phase and crystallinity of the nanostructured materials were also investigated.

• Journal of Surface Science and Engineering
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• v.35 no.3
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• pp.149-157
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• 2002

Spectral emissivity depends on the surface conditions of the materials. The mechanisms that affect the spectral emissivity in anodic oxide films on aluminum were investigated. The aluminum specimens were anodized in a sulfuric acid solution and the thickness of the resulting oxide film formed changed with the anodizing time. FT-IR spectrum analysis identified the anodic oxide film as boehmite ($Al_2$$O_3$.$H_2$O). Both the infrared emisivity and reflectivity of the anodized aluminum were affected by the structure of the anodic oxide film because Al-OH and Al-O-Al have a pronounced absorption band in the infrared region of the spectrum. The presence of an anodic oxide film on aluminum caused a rapid drop in the infrared reflectivity. An aluminum surface in the clean state had an emissivity of approximately 0.2. However, the infrared emissivity rapidly increased to 0.91 as the thickness of the anodic oxide film increased.

• Bulletin of the Korean Chemical Society
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• v.23 no.11
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• pp.1519-1523
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• 2002

A procedure for preparing semiconductor/metal nanowire arrays is described, based on a template method which entails electrochemical deposition into nanometer-wide parallel pores of anodic aluminum oxide films on aluminum. Aligned CdS/Co heterostructured nanowires have been prepared by ac electrodeposition in the anodic aluminum oxide templates. By varying the preparation conditions, a variety of CdS/Co nanowire arrays were fabricated, whose dimensional properties could be adjusted.

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.856-859
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• 2002

To investigate effects of heat treatments including grain size control in substrate aluminum on nanopore arrays in anodic alumina template, aluminum was heat treated at $500^{\circ}C$ for 1h. The heat treated aluminum was anodized by two successive anodization processes in oxalic solution and the nanopore arrays in anodic alumina layer were studied using TEM and FE-SEM. The highly ordered porous alumina templates with 110 nm interpore distance and 40 nm pore diameter have been observed and the pore array of the anodic alumina has a uniform and closely-packed honeycomb structure. In the case of alumina template obtained from heat treated aluminum substrate, the well- ordered nanopore region in anodic alumina increased and became more homogeneous compared with that from non-heattreated one.

• Journal of Surface Science and Engineering
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• v.54 no.2
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• pp.90-95
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• 2021

Surface modification technique enabling the control of condensation provides various benefit in various engineering systems, such as heat transfer, desalination, power plants, and so on. In this study, lubricant oil-impregnation into Teflon-coated nanoporous anodic oxide layer of aluminum to enhance a de-wetting and mobility of water droplet on surface. Due to the surface treatment improving water-repellency, the condensation mode is changed to dropwise, thus the frequency of sliding condensed water droplet on surface is increased. For these reasons, the surface of oil-impregnated Teflon-coated nanoporous anodic aluminum oxide shows significantly enhanced condensation heat transfer compared to bare aluminum surface. In addition, the porosity of anodic aluminum oxide affected the mobility of water droplet even with oil-impregnation and Teflon-coating, indicating that the optimization of porous structure of anodic oxide is required for maximizing the condensation heat transfer.

• Journal of Surface Science and Engineering
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• v.57 no.4
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• pp.254-264
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• 2024

This paper reviews the dielectric breakdown resistance and behavior of anodic oxide films in air environment. It begins with a description of the dielectric breakdown mechanisms of dielectric materials. The paper then introduces different types of dielectric materials and compares them in terms of dielectric strength, thermal conductivity, mechanical strength and cost. Next, the paper summarizes various fabrication methods for dielectric aluminum oxide layers, discussing the advantages and disadvantages of each method. Finally, it provides an overview of current studies on the dielectric breakdown properties of anodic aluminum oxide films formed on different aluminum alloys in various electrolytes.

• Journal of Surface Science and Engineering
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• v.53 no.1
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• pp.36-42
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• 2020

In this study, two novel methods to measure the surface hardness of anodic oxide films on aluminum alloys are reported. The first method is to impregnate oil-based ink into pores in the anodic oxide film and then to clean the ink on the surface using ethanol, resulting in an impregnation of inks only inside of the pores in anodic oxide film. The second method is to coat the anodic oxide film surface with thin Au layer less than 0.1 ?. Both the ink-impregnating method and Au-coating method provided clear indentation marks on the anodic oxide film surface when it was indented using a pyramidal-diamond penetrator. Thus, Vickers hardness of anodic oxide films on aluminium alloy could be measured successfully and precisely from the anodic film surface. In addition, advantages and disadvantages of the ink-impregnating method and Au-coating method for the measurement of surface hardness of anodic oxide films are discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.242-242
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• 2009

Fabrication of Anodic aluminum oxide under DC vias condition has been studied. When bias and time of anodic aluminum oxide process change, the hole distance and diameter size change. Comparison of fabricated AAO between AC vias and DC vias condition has been studied in this experiment. The first and second anodization of one aluminum is done by using DC and AC power supplier. And first and second anodization of another aluminum is done by DC power supplier. The size of the aluminum is $1cm{\times}3cm$, and second anodic aluminum oxide process takes about 45min. It is found that the hexagonal shape appears on the surface of the AAO. AC power source can fabricate aao which have a nano hole array. We can see that the hole on the surface of the AC vias has a better rounded hole than DC vias AAO. we need more data so we can get characteristic about AC power generated AAO.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.349-352
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• 2014

Anodic alumina oxide (AAO), a self-ordered hexagonal array, has various applications in nanofabrication such as the fabrication of nanotemplates and other nanostructures. In order to obtain highly ordered porous alumina membranes, a two-step anodization or prepatterning of aluminum are mainly conducted with straight electric field. Electric field is the main driving force for pore growth during anodization. However, impurities in aluminum can disturb the direction of the electric field. To confirm this, we anodized two different aluminum foil samples with high purity (99.999%) and relatively low purity (99.8%), and compared the differences in the surface morphologies of the respective aluminum oxide membranes produced in different electric fields. Branched pores observed in porous alumina surface which was anodized in low-purity aluminum and the size; dimensions of the pores were found to be usually smaller than those obtained from high-purity aluminum. Moreover, anodization at high voltage proceeds to a significant level of conversion because of the high speed of the directional electric field. Consequently, anodic alumina membrane of a specific morphology, i.e., meshed pore, was produced.