• Journal of the Korean institute of surface engineering
• /
• v.53 no.2
• /
• pp.80-86
• /
• 2020

This paper is concerned with type of imperfections present within the anodic oxide films on AA2024 and surface hardness of the anodic film measured after ink-impregnation. The anodic oxide films were formed for 25 min at 40 mA/㎠ and 15±0.5℃ and 300 rpm of magnet stirring rate in 20% sulfuric acid solution. The ink-impregnation allows clear observations of not only the imperfections within the anodic oxide films but also an indentation mark on the oxide film surface made by a pyramidal-diamond penetrator for the hardness measurement. There were observed four different regions in the anodic oxide films on AA2024 and the surface hardness of the anodic oxide films appeared to be crucially dependent on the type of defects, showing 60~100 H_v on the oxide surface region I with large size black defect, 100~140 H_v on the oxide surface region II with large size grey defect, 140~170 H_v on the oxide surface region III with mall size black and/or grey defects and 170~190 H_v on the oxide surface region IV without defects. The pyramidal indentation marks were observed to be distorted in the regions with a large size black and grey defects, while no distortion of the indentation mark was observed in the regions with small size defects and without visible defects.

• Journal of the Korean institute of surface engineering
• /
• v.17 no.2
• /
• pp.29-40
• /
• 1984

The structure of rapidly solidified Al-Si-based alloys and its relationship to subsequent anodic film growth in near neutral and acid solutions have been investigated. Solidification of the alloys proceeds via pre-dendritic nuclei, associated with rugosity of the casting surface, from which cellular-type growth, comprised of aluminium-rich material surrounded by silicon-containing material, emanates. Observation of ultramicrotomed sections of the alloys and their anodic films reveals the local oxidation of the silicon-rich phase and its incorporation into the anodic alumina film, formed in near neutral solutions. Such incorporation occurs but resultant isolation of the silicon-rich phase is not possible for anodizing in phosphoric acid, and a three-dimensional network of the oxidized silicon-containing phase, with continuing development of porous anodic alumina, is observed.

• Transactions on Electrical and Electronic Materials
• /
• v.3 no.4
• /
• pp.27-31
• /
• 2002

Thin film diode with reliable interfacial structure was fabricated by using multi-step anodic oxidation. The thickness of the oxide layer was preciously controlled with anodic voltage. Also, interfacial structure between oxide layer and top electrode was improved by applying post heat-treatment. The thin film diode showed symmetric and stable I-V characteristics after the post heat-treatment.

• Bulletin of the Korean Chemical Society
• /
• v.24 no.7
• /
• pp.975-980
• /
• 2003

The electrochemical properties and the mechanism of formation of anodic oxide films on Mg alloys containing 0-15 mass% Al, when anodized in NaOH solution, were investigated by focusing on the effects of anodizing potential, Al content, and anodizing time. The intensity ratio of Mg(OH)₂ in the XRD analysis decreased with increasing applied potential, while that of MgO increased. Mg(OH)₂ was barely detected at 80 V, while MgO was readily detected. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. The intensity ratio of the β phase increased with aluminum content in Mg-Al alloys. During anodizing, the active dissolution reaction occurred preferentially in β phase until about 4 min, and then the current density increased gradually until 7 min. The dissolution reaction progressed in α phase, which had a lower Al content. In the anodic polarization test in 0.017 mol·$dm^{-3}$ NaCl and 0.1 mol·$dm^{-3}$ Na₂SO₄ at 298 K, the current density of Mg-15 mass% Al alloy anodized for 10 min increased, since the anodic film that forms on the α phase is a non-compacted film. The anodic film on the α phase at 30 min was a compact film as compared with that at 10 min.

• Journal of Advanced Marine Engineering and Technology
• /
• v.28 no.2
• /
• pp.300-308
• /
• 2004

The formation mechanism of anodic oxide films on Mg alloys when anodized in NaOH solution. was investigated by focusing on the effects of anodizing potential. Al content. and anodizing time. Pure Mg and Mg-Al alloys were anodized for 10 min at various potentials in NaOH solutions. $Mg(OH)_2$ was generated by an active dissolution reaction at the surface. and the product was affected by temperature. The intensity ratio of $Mg(OH)_2$ in the XRD analysis decreased with increasing applied potential. while that of MgO increased. The anti-corrosion properties of anodized specimens at each constant potential were better than those of non-anodized specimens. The specimen anodized at an applied potential of 3 V had the best anti-corrosion property. And the intensity ratio of $Mg_{17}Al_{12}$/Mg increased with aluminum content in Mg-Al alloys. During anodizing. the active dissolution reaction occurred preferentially in ${\beta}\;phase(Mg_{17}Al_{12})$ until about 4 mins. and then the current density increased radually until 7 mins. The dissolution reaction progressed in a phase(Mg) which not formed the intermetallic compound. which had a lower Al content. In the anodic polarization test of $0.017\;mol{\cdot}dm^-3$ NaCl and $0.1\;mol{\cdot}dm^-3\;Na_2SO_4$ at 298 K. the current density of Mg-15 mass% Al alloy anodized for 10 mins increased. since the anodic film that forms on the a phase is a non-compacted film. The anodic film on the phase for 30 mins was a compact film as compared with that for 10 mins.

• Journal of the Korean institute of surface engineering
• /
• v.51 no.6
• /
• pp.393-399
• /
• 2018

Formation behavior of aluminum anodic oxide (AAO) films on Al6061 alloy was studied in view of thickness, morphology and defects in the anodic films in 20 vol.% sulfuric acid solution at a constant current density of $40mA/cm^2$, using voltage-time curve, observation of anodized specimen colors and surface and cross-sectional morphologies of anodic films with anodization time. With increasing anodizing time, voltage for film formation increased exponentially after about 12 min and its increasing rate decreased after 25 min, followed by a rapid decrease of the voltage after about 28 min. Surface color of anodized specimen became darker with increasing anodizing time up to about 20 min, while it appeared to be brighter with increasing anodizing time after 20 min. The darkened and brightened surfaces with anodizing time are attributed to an increase in thickness of porous anodic oxide film and a chemical damage of the films due to heat generated by increased resistance of the film, respectively. Cross-sectional observation of AAO films revealed the formation of defects of crack shape at the metal/oxide interface after 15 min which prevents the growth of AAO films. Width and length of the crack-like defect increased with anodizing time up to 25 min of anodizing, and finally the outer part of AAO films was partly dissolved or detached after 30 min of anodizing, resulting in non-uniform surface structures of the AAO films.

• Transactions of the Society of Information Storage Systems
• /
• v.9 no.2
• /
• pp.67-71
• /
• 2013

The fabrication method of plasmonic nanodots on silicon substrate has been developed to improve the efficiency of thin film solar cells. Nanoscale metallic nanodots arrays are fabricated by anodic aluminum oxide (AAO) template mask which can have different structural parameters by varying anodization conditions. In this paper, the structural parameters of gold nanodots, which can be controlled by the diverse structures of AAO template mask, are investigated to enhance the optical properties of a-Si thin film solar cells. It is found that optical properties of the thin film solar cells are improved by finding optimization values of the structural parameters of the gold nanodot array.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.8
• /
• pp.869-874
• /
• 1999

In this paper, electrochemical techniques are used to investigate hydrothermal-electrochemically formation of barium titanate (BT) ceramic films. For comparison, the electrochemical behaviors of anodic titanium oxide films formed in alkaline solution were also investigated both at room temperature and in hydrothermal condition at 150.0 ℃. Film structure and morphology were identified by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Titanium oxide films produced at different potentials exhibit different film morphology. The breakdown of titanium oxide films anodic growth on Ti electrode plays an important roles in the formation of BT films. BT films can grow on anodic oxide/metal substrate interface by short-circuit path, and the dissolution-precipitation processes on the ceramic film/solution interface control the film structure and morphology. Based upon the current experimental results and our previous work, extensively schematic proce-dures are proposed to model the mechanism of ceramic film formation by hydrothermal-electrochemical method.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2003.11a
• /
• pp.227-232
• /
• 2003

Anodizing film was prepared by anodic oxidation of pure aluminum(purity > 99.50) using DC power supply for constant current mode in an electrolytic solution of surface of sulfuric acid. Effects of pre-treatment process such as chemical polishing, acid cleaning, alkali etching before anodic oxidation, were studied to microstructures and surface morphologies. A roughness on surface of anodizing film had to be decreased for amorphous phase by anodic oxidation. A roughness on surface of anodizing film decrease as annealing temperature increased in chemical polishing.

• Journal of the Korean Vacuum Society
• /
• v.15 no.5
• /
• pp.518-526
• /
• 2006

Nanoporous alumina film was fabricated by anodization of an aluminum sheet. Highly ordered nanowellstructured and nanonets-tructured metal films were fabricated by vacuum evaporation of several metals(Al, Sn, and Co) using the anodic nanoporous alumina film as a template. In this experiment, an anodic porous alumina film with the cell size of 100 nm and the pore diameter of 60 nm was used. The resistance heating method was adopted for evaporating a desired metal, and vapor deposition was carried out under the base pressure of torr. It was founded that whether the structure fabricated by vacuum evaporation is nanowell or nanonet is dependent on the amount of deposited material. When an anodic porous alumina film with the cell size of 100 nm and the pore diameter of 60 nm was used, a nanowell-structured film was fabricated when a sufficient amount of metal was suppled to cover the surface pores. On the other hand, nanonet-structured film was fabricated bellow a half the amount of metal required for nanowell-structured film.