• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.115.2-115.2
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• 2016

Al alloys are being used widely for automobile, aerospace and mechanical components because of their high strength ratio to weight. However, still they suffer from abrasion or corrosion owing to insufficient resistances to friction or mechanical impact and chemical attack. Plasma electrolytic oxidation (PEO) method is one of the promising surface treatment methods for Al alloys which can render better hardness than aluminum anodic oxide (AAO) films prepared by conventional anodizing method in acidic solutions. In this presentation, some basic nature of PEO film formation and growth process on Al alloys will be presented based on the experimental results obtained and discussed in view of dielectric breakdown and reformation and the role of various anions in film breakdown and reformation of PEO films.

• Bulletin of the Korean Chemical Society
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• v.30 no.5
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• pp.1131-1134
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• 2009

Preparation of graded materials displaying gradients of desired properties is one of the important issues and less-developed areas in materials chemistry. For the first time we demonstrate facile control of porosity and length in the pores of AAO template in lateral directions by controlled dipping method. To demonstrate the versatility of the proposed method, laterally graded silica nanotubes are also prepared by using the laterally graded AAO templates. The method demonstrated here will open numerous possibilities for obtaining a variety of graded materials with lateral gradients of catalytic, electrochemical, mechanical and optical properties on the nanoscale.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4165-4168
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• 2012

Magnetic fluorescent silica nanotubes were fabricated using reverse micro-emulsions coupled with conventional sol-gel methods. Anodic aluminum oxide templates were used to separate spatially the magnetic and the fluorescent moieties on individual nanotubes and so prevent quenching of the fluorescence. C18 and fluorescent layers were deposited sequentially on silica. Magnetism was then obtained by the introduction of pre-made magnetic nanoparticles inside the nanotubes. The photo- and chemical stabilities of nanotubes were demonstrated through dye release and photobleaching tests. The produced nanotubes did not show fluorescence quenching upon the addition of the nanoparticles, an advantage over conventional spherical fluorescent magnetic nanoparticles. High photostability of nanotubes, magnetism and biocompatiblily make them potentially useful in bioanalysis.

• KSBB Journal
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• v.27 no.1
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• pp.45-50
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• 2012

In this paper, we investigated the effect of nanostructure on the cell behaviors such as adhesion and growth rate. Nanoporous structures with various diameters (30, 40, 45, 50, 60 nm) and 500 nm of the depth were fabricated using the anodizing method. The water contact angle of the surface consisting of nanopores with 30 nm diameter was 40 degree and those were 60~70 degree in cases of nanopores with over 40 nm diameter. Hela cells were cultivated on various nanoporous structure surface to investigate the cell behavior on nanostructure. As a result, Hela cells preferred 30 nm diameter nanoporous surface that has lower water contact angle. This result was confirmed by protein adsorption experiment and scanning electron microscope investigation.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.135-136
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• 2011

본 연구에서는 실리콘 기판위의 형성된 AAO (Anodic Aluminum Oxide)의 barrier layer를 $Cl_2/BCl_3$ gas mixture에서 Neutral Beam Etching (NBE)과 Ion Beam Etching (IBE)로 각각 식각한 후 그 결과를 비교하였다. 이온빔의 경우 나노사이즈의 AAO pore의 charging에 의해 pore 아래쪽의 위치한 barrier layer를 어떤 식각조건에서도 제거하지 못하였다. 하지만, charging effect가 없고, 높은 중성화율을 나타내는 low angle forward reflected 방식의 neutral beam etching (NBE)에서는 $BCl_3$-rich $Cl_2/BCl_3$ gas mixture인 식각조건에서 AAO pore에 휘발성 $BO_xCl_y$를 형성하면서 barrier layer를 제거할 수 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.814-817
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• 2010

AAO thin films prepared by a two-step anodization process have pores that are uniform in diameter, highly ordered, and perfectly vertical with respect to the plane of the nano template. Further, the pore size and interpore distance can be easily controlled by varying the anodizing voltage and acid electrolyte. When metals are electrochemically deposited in the pores, metal nanowires that are highly ordered and uniform in diameter are formed in each pore.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.585-588
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• 2005

The dissolution characteristic of metal shows the different tendency according to the applied electrical potential, the kind of electrolyte and pH value, etc. In the micro electrochemical machining (ECM), unfavorable oxide/passive layer formation and overall corrosion of electrodes must be prevented. The anodic polarization curve of nickel has distinct three dissolution regions, i.e. two active regions and the transpassive dissolution region. In this paper, the stable electrode potentials of workpiece and tool were determined in sulfuric acid and hydrochloric acid solution, respectively. In each solution, different machining property was shown and possible electrochemical reactions were discussed. On the basis of this experiment, the methodology to obtain the proper electrode potential was suggested.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.329-329
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• 2012

알루미늄 합금은 기존에는 경량소재로써 각광을 받아왔지만, 최근에는 다양한 전자 및 기계 부품에서 방열이 크게 대두 됨에 따라 방열 소재로써의 관심이 증가하고 있다. 알루미늄 합금의 고유한 표면처리법인 양극산화에의해 생성되는 산화층의 열전도도에 대한 연구를 실시하였다. 또한, 이들 산화층은 실리이라는 후처리에 의해서 기공구조의 변화가 일어나는데, 이 실링 처리가 열전도도에 미치는 영향에 대해서 확인해 보았다. 양극 산화피막의 미세 기공층이 비어있는 경우에 비해서 실링에 의해서 기공이 산화물 및 수산화물로 채워진 경우 열전도도가 증가하였다. 또한, 산화층의 기공률에 따라서 열전도도가 증가되는 비율의 차이가 발생하였다.

• Journal of the Semiconductor & Display Technology
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• v.20 no.1
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• pp.37-41
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• 2021

We report on the formation of anodic aluminum oxide (AAO) film using sulfuric acid containing cerium salt. When the temperature of the sulfuric acid containing cerium salt changes from 5 ℃ to 20 ℃, the current density and the thickness growth rate increase. The surface morphology of the AAO film change according to the temperature of the electrolytes. And that affected the breakdown voltage and the plasma etch rate. The breakdown voltage per unit thickness was the highest at 15 ℃, and the plasma etch rate was the lowest at 10 ℃ at 2.80 ㎛/h.

• Journal of the Korean institute of surface engineering
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• v.55 no.5
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• pp.292-298
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• 2022

In this study, PEO (plasma electrolytic oxidation) film formation behavior of AZ31 Mg alloy under application of 300 Hz pulse current was studied by the analyses of V-t curve, arc generation behavior, PEO film thickness and morphology of PEO films with treatment time in 0.05 M NaOH + 0.05 M Na₂SiO₃ + 0.1 M NaF solution. PEO films was observed to grow after 10 s of application of pulse current together with generation of micro-arcs. PEO film grew linearly with treatment time at a growth rate of about 5.58 ㎛/min at 200 mA/cm² of pulse current but increasing rate of film formation voltage became lowered largely with increasing treatment time after passing about 250 V, suggesting that resistivity of PEO films during micro-arc generation decreases with increasing film formation voltage at more than 250 V.