• Polymer(Korea)
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• v.34 no.5
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• pp.405-409
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• 2010

New sol-gel precursors having the ability to protect iron against corrosion were synthesized and used to prepare organic-inorganic hybrid coatings based on epoxy. Bisphenol A epoxy was modified with 3-isocyanatopropyltriethoxysilane to improve the compatibility, and water and HCl were used as catalysts for sol-gel process. Various coating formulations were prepared depending on the type of sol-gel precursors and the amount of each ingredient, and cast on iron substrates by dip-coating and thermally cured. Corrosion protection properties of coated iron were studied by a salt spray test and electrochemical impedance spectroscopy under 0.1 M NaCl electrolyte. Hybrid coatings containing anticorrosive functional group exhibited excellent corrosion protection on iron, compared to that of typical hybrid coatings. From electrochemical impedance spectroscopy, the hybrid coatings containing anticorrosive functional group could maintaine the initial impedance after 500 h, while the impedance of hybrid coatings without them started to decrease after 24 h.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1232-1233
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• 2008

딥 코팅 공정을 통하여 콜로이드 $Fe_2O_3$ 나노입자의 단일층을 다공성의 AAO (Anodic Aluminum Oxide) 기판에 형성하였다. 나노입자의 평균 사이즈는 20 nm이고, 각각의 나노입자는 올레익 산(oleic acid) 으로 둘러싸여 옥탄(octane) 용액 안에 분산되어있다. AAO 기판은 알루미늄에 높은 균일성과 고밀도의 기공(pore) 형성을 위해 두 단계 양극산화공정을 통해 제작하였다. AAO 기공의 지름은 ${\sim}$30에서 100 nm 이고, 딥 코팅 공정의 속도는 0.1 mm/sec 로 하여 AAO의 나노기공 안에 나노입자의 단일층을 성공적으로 형성시켰다.

• Journal of Adhesion and Interface
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• v.20 no.2
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• pp.66-70
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• 2019

The surface of hydrophobic polypropylene (PP) fibers (spun-bonded fabric) was treated by an atmospheric plasma treatment method. These pre-treated hydrophilic PP fabrics were dip-coated in the aqueous poly(N-vinyl pyrrolidone) (PVP) solution. PVP layers on the surface of PP fiber were crosslinked by an irradiation of electron beam. The thickness of PVP hydrogels coated on the surface was easily controlled by changing the concentration of PVP in coating solution. The stepwise surface treatment, PVP coating, and hydrogel formation via electron beam irradiation were analyzed by the measurement of contact angle, scanning electron microscopy, and optical microscopy.

• Polymer(Korea)
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• v.35 no.6
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• pp.520-525
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• 2011

Superporous hydrogels (SPHs) with fast swelling and superabsorbent properties are useful materials in various biomedical fields, by improving the swelling properties of conventional hydrogels based on their unique porous structure. In this study, Eudragit polymers were used as coating materials to control the swelling properties of poly(acrylic acid-co-acrylamide) based SPHs by environmental pH. The SPHs were coated with Eudragit L100 and S100 that have different pH characteristics as enteric coating materials by a dip coating method, and their pH dependent swelling behaviors were observed in various pH environments. The swelling of SPHs was inhibited at a low pH range, but significantly enhanced above a characteristic pH of Eudragit polymers. This pH dependent swelling behavior of hydrogels could be modulated by the characteristics of the enteric coating polymers.

• Membrane Journal
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• v.29 no.6
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• pp.362-376
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• 2019

In this study, hydrophilic coating characteristics of PVDF [poly(vinylidene fluoride)] hollow fiber membranes with flower type cross-section prepared by thermally induced phase separation were studied. The hollow fiber used in this study was provided from PureEnvitech Co. Ltd., and the hydrophilic coating experiment was performed with different concentration and number of coating of PEBAX 1657, 2533 and 3533 block copolymer solution using a dip coating method. The hydrophilic coated hollow fiber membrane was characterized to scanning microscope and contact angle measurements to determine the degree of hydrophilization. As a result of SEM characterization, it was confirmed that the thickness of the coating layer increased as the coating concentration increased and the number of coatings increased. Contact angle of surface of hollow fibers decreased as the concentration of the coating solution increased and the number of coatings increased. Gas permeance of oxygen gas was measured for the application of the hydrophilized hollow fiber to Membrane Areated Biofilm Reactor. As a result of gas permeation test, it was confirmed that gas permeance decreased with increasing coating concentration and number of coatings, and the more hydrophilized hollow fiber coated with PEBAX 1657 showed lower gas permeance than those coated with PEBAX 2533 and 3533.

• Clean Technology
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• v.28 no.3
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• pp.218-226
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• 2022

As a result of the recent social transformation towards a hydrogen economy and carbon-neutrality, the demands for hydrogen energy have been increasing rapidly worldwide. As such, eco-friendly hydrogen production technologies that do not produce carbon dioxide (CO₂) emissions are being focused on. Among them, ammonia (NH₃) is an economical hydrogen carrier that can easily produce hydrogen (H₂). In this study, Ru/Al₂O₃ catalyst coated onmetallic monolith for hydrogen production from ammonia was prepared by a dip-coating method using a catalyst slurry mixture composed of Ru/Al₂O₃ catalyst, inorganic binder (alumina sol) and organic binder (methyl cellulose). At the optimized 1:1:0.1 weight ratio of catalyst/inorganic binder/organic binder, the amount of catalyst coated on the metallic monolith after one cycle coating was about 61.6 g L^-1. The uniform thickness (about 42 ㎛) and crystal structure of the catalyst coated on the metallic monolith surface were confirmed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Also, a numerical optimization regression equation for NH3 conversion according to the independent variables of reaction temperature (400-600 ℃) and gas hourly space velocity (1,000-5,000 h^-1) was calculated by response surface methodology (RSM). This model indicated a determination coefficient (R²) of 0.991 and had statistically significant predictors. This regression model could contribute to the commercial process design of hydrogen production by ammonia decomposition.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.403-405
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• 2009

본 연구에서는 염료태양전지의 제작 시 고가의 TCO전극을 사용하지 않고 간단히 광전극을 대체할 수 있는 방법으로 메쉬전극을 이용하는 TCO-less 염료태양전지를 제작하였다. 메쉬전극을 이용한 TCO-less 염료태양전지의 구조는 "Glass / 메쉬전극($TiO_2$를 딥코팅 한 후 염료를 흡착시킴) / 전해질 / 멤브레인 필터 / 상대전극(Pt-coated TCO) / Glass" 로 구성된다. 제작된 샘플의 광전변환 효율은 약 1.5% 였으며 fill factor는 0.55로 나타났다. 향후 계획으로 효율을 향상 시킬 수 있는 방법을 도입하여 광전류밀도와 fill factor를 개선하는 연구를 진행할 예정이다.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1340_1341
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• 2009

In this report, high-resolution metal electrode patterning is demonstrated by using selective surface treatment and dip casting for low-cost printed electronic applications. On hydrophobic octadecyltrichlorosilane treated $SiO_2$ surface, deep UV irradiation was performed through a patterned quartz photomask to selectively control the surface energy of the $SiO_2$ layer. The deep UV irradiated region becomes hydrophilic and by dipping into Ag nano-ink, Ag patterns were formed on the surface. Using this patterning technique, line patterns and dot arrays having less than $10{\mu}m$ pitch were fabricated.

• Journal of the Korean Society of Visualization
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• v.17 no.3
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• pp.39-45
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• 2019

A study on the sloshing flow of highly-viscous fluid in a rectangular box was made by both of theoretical approach and experimental visualization method. Assuming a smallness of external forcing to oscillate the container, it was investigated a linear sloshing flow of highly-viscous fluid utilizing asymptotic analysis by Taylor-series expansion as a small parameter R_e (≪1) in which R_e denotes Reynolds number. The theory predict that, during all cycles of sloshing, a linear shape of free surface will prevail in a bulk zone and it has confirmed in experiment. The relevance of perfect slip boundary condition, adopted in theoretical approach, to the bulk zone flow at the container wall was tested in experiment. It is found that quasi-steady coated thin film, which makes a lubricant layer between bulk flow and solid wall, is generated on the wall and the film makes a role to perfect slip boundary condition.

• Journal of the Korean Ceramic Society
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• v.34 no.1
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• pp.37-44
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• 1997

Barium ferrite thin films on the thermal oxidized Si substrate were prepared by using sol-gel method (dip coating) from the sol of composition ratio of 5.25, designated by mole ratio 2Fe/Ba. The gelation process was largely divided into 4 step, and the sol prepared by reaction for 90 minutes at 8$0^{\circ}C$ was the suit-able for coating. Needle shaped particles formed on the coating layer were placed parallel to substrate and the inclination was increased with film thickness. The easy-direction of magnetization of needle shaped par-ticles was long-axis direction.