• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.691-696
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• 2011

Organic-inorganic hybrid coating solutions were prepared by using a sol-gel method for transparent film. In this study, colloidal silica (CS) and alkoxy silane such as vinyltrimethoxysilane (VTMS), and [3-(methacryloyloxy)]propyltri methoxy silane (MAPTMS) were used in various conditions such as types of organic silane, weight ratios of CS to silane and reaction times. Coating solutions which were bar coated on the PET (polyethyleneterephthalate) film and cured were investigated on the chemical and physical properties. The pencil hardness and adhesion of coating films were increased with increasing the organic silane content in the coating solution compared to that of PMMA (polymethamethylcrylate) coating solution.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.25-31
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• 2022

By an aid of needle coating, we have fabricated a spherical microlens array using poly(methyl methacrylate) for potential applications in light extraction of organic light-emitting diodes. With an attempt to achieve high-density and high-aspect-ratio microlens arrays, we have investigated the coating behaviors by varying the material parameters such as the solute concentration and wettability of the poly(methyl methacrylate) solution and process parameters such as the dwell time of needle near the substrate, retract distance of needle from the substrate, and coating gap between the needle and substrate. Under the optimized coating conditions, it is demonstrated that high-aspect-ratio microlens arrays can be obtained using a coating solution with high solute concentration and a small amount of a hydrophobic solvent. It is found that the diameter and height of microlens array are decreased with increasing poly(methyl methacrylate) concentration, yet the overall aspect ratio is rather enhanced. By the addition of 5 wt% hexylamine in 35 wt% poly(methyl methacrylate) solution, we have achieved a spherical microlens with the height of 7.7 ㎛ and the width of 94.24 ㎛ (the aspect ratio of 0.082). To estimate the capability of light extraction by the microlens array, we have performed ray tracing simulations and demonstrated that the light extraction efficiency of organic light-emitting diode is expected to be enhanced up to 24%.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2003.11a
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• pp.148-153
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• 2003

The influence of sizing, fiber and pigment type on coating penetration, using commercial paper and two types of handsheets as the base paper which were prepared from thermomechanical pulp(TMP) and hardwood bleached kraft pulp(KP) sized internally with alkyl ketone dimmer(AKD), was studied in terms of characteristics of coating holdout. Laboratory rod draw down coater was used for surface sizing and coating application. Characterization of coating penetration was done by measuring the roughness of the backside of coating layer. The backside of the coating was exposed by dissolving the fibers in a solution of cupriethylenedimine(CED). Data show that internal sizing of base paper is effective and surface sizing is more effective to prevent coating penetration. Comparing between the two types of base papers, backside roughness of coating layer of TMP sheet is much larger and sizing is more effective to reduce coating penetration than those of KP sheet. With regard to pigment type, clay is more effective than calcium carbonate for better coating holdout.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.15 no.3
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• pp.201-222
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• 2011

In the present work, the mathematical model of wire coating in a straight annular die is developed for unsteady second grade fluid in the form of partial differential equation. The Optimal Homotopy Asymptotic Method (OHAM) is applied for obtaining the solution of the model problem. This method provides us a suitable way to control the convergence of the series solution using the auxiliary constants which are optimally determined.

• Bulletin of the Korean Chemical Society
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• v.21 no.8
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• pp.817-822
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• 2000

Crack-free hard coating siIica films were prepared by sol-gel processfrom twokinds of silicon alkoxide (tetra-ethoxysilane and methyltrimethoxysilane) and two kinds of alcohol (methanol and isopropyl alcohol) with an acid catalyst,acetic acid. A silicate framework of the precursor solution was investigated by infrared spectros-copy (IR) in the process of hydrolysis and condensation. Theextent of the condensation in the intermediates was elucidated by gel permeation chromatography (GPC) and 29Si-NMR spectroscopy. The hard coating films werecharacterized by IR,scanning electron microscope (SEM), thermo gravimetric analyzer (TGA) and dif-ferential scanning calroimeter (DSC). The synthetic condition for the crack-free and transparent silica film for-mation was optimized interms of starting materials for the precursor solution as well as preparation method of the silica film.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.34.2-34.2
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• 2009

The ceramic coatings on metallic materials have attracted by many researchers due to the chemical inertness of ceramic materials. In such aspect, SiOC is a promising material tobe used as protective coating layer on metallic materials due to its outstanding thermal stability and chemical inertness. In this research, SiOC coating was carried out onto SuS-316 substrate using Cl free preceramic polymers such aspolyphenylcarbosilane. 20% of polymethylphenylsilane in cyclohexane solution was coated onto metal surface by dip coating method. Thermal oxidation was carried out at $200^{\circ}C$ for crosslink of the preceramic polymer and the sample was pyrolysized at $800^{\circ}C$ under argon to convert the preceramic polymer to amorphous SiOCx state. The microstructure of the SiOCx film after pyrolysis was investigated using FE-SEM. Corrosion resistance of SiOC coated SuS-316 substrate has been investigated using 5% HCl solution at 25, 40, 60 and $80^{\circ}C$ for 7days. The data revealed that the corrosion resistance increased with SiOC coating on SuS-316 substrate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.457-460
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• 2006

Y doped zinc oxide (YZO) thin films were deposited on F doped $SnO_2$ (FTO) glass substrate by sol-gel method using the spin-coating system. A homogeneous and stable solution was prepared by dissolving acetate in the solution added diethanolamine as sol-gel stabilizer. YZO films were obtained after preheated on the hot-plate for 5minute before each coating; the number of coating was 3 times. After the coating of last step, annealing of YZO films performed at $450^{\circ}C$ for 30 minute. In order to confirming of a ultraviolet ray interruption and down-conversion effects, optical properties of YZO films, transmission spectrum and fluorescent spectrum were used. Also, for understanding the obtained results by experiment, the elestronic state of YZO was calculated using the density functional theory The results obtained by experiment were compared with calculated structure. The detail of electronic structure was obtained by the discrete variational Xa (DV-Xa) method, which is a sort of molecular orbital full potential method. The density of state and energy levels of dopant element were shown and discussed in association with optical properties.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.14-17
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• 2007

The slot-die coating & calcination process was adopted to fabricate the long YBCO precursor films on the buffered metal tape for the $2^{nd}$ generation coated conductors. To obtain the smooth and crack-free surface of long YBCO precursor films, the parameters of slot-die coating and the process variables of calcination step must be optimized simultaneously in reel-to-reel method. Among the parameter of slot-die coating process, the viscosities of the precursor solution was controlled from 60cP to 200cP to obtain the thicker films from on single coating. The slot-die gap, the injection rate of precursor solution, the moving speed of buffered metal tape etc. are controlled lot the full coverage and smooth surface of YBCO precursor films. The slot-die coated films are moved through the tube furnace with predetermined heating profiles in humid oxygen ambient The YBCO precursor films was identifed with $Y_2O_3,\;BaF_2$, and CuO phase by XRD and consisted of fine grains of about 20nm size observed by FE-SEM. The YBCO films show the critical current density over $MA/cm^2$ using the precursor films formed by the continuous slot-die coating & calcination process.

• Korean Journal of Materials Research
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• v.13 no.9
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• pp.555-560
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• 2003

Ag-coated Cu particles were prepared by dropping method of coating agent and were evaluated by scanning electron microscope and color difference meter. The shape of Cu particles having obvious crystal plan and edge was changed spherically according to the increase of Ag coating amount. When the Ag coating amount was 50 wt% to Cu particles, the whiteness of Ag-coated Cu particles was almost similar to that of pure Ag particles. Adding $NH_4$OH in reductant solution could increase effectively the whiteness of the Ag-coated particles. The Ag-coated particles having the highest whiteness was obtained when the content of hydrazine in reductant solution was 0.48 M.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.189-189
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• 2015

In this study, the corrosion resistance and adhesion of electrophoretic paint (E-paint) were studied on AZ31 magnesium alloy pretreated in cerium chemical conversion coating solutions with the addition of various ethanol concentrations. It was found that with increasing ethanol concentration from 0 to 90 percent can decrease the formation of $Mg(OH)_2/MgO$ and increase the formation of nano-crystalline cerium oxides on the coating. Both corrosion resistance and adhesion of E-painted AZ31 increased with increasing ethanol concentration. The best E-paint sample was observed on the sample pretreatment in cerium chemical conversion coating solution with the addition of 80 percent of ethanol. This sample showed an excellent adhesion without paint detached after water immersion test for 500 h at $40^{\circ}C$, and only a few blisters observed at the near scratched sites after 1000 h salt-spray test.