• Journal of Surface Science and Engineering
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• v.19 no.3
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• pp.83-91
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• 1986

Codeposited of boron nitride(BN) particle dispersed into electroless nickel-phosphours (Ni-P) and nickel-boron(Ni-B) platings were studied for the purpose of developing the wear resistance and lubricity. BN can be codeposited from electroless nickel plating bath with $NaH_2PO_2$ and $NaBH_4$ as the reducing agents. Most dispersolids were distributed uniformly in the Ni-P and Ni-B matrix. Abrasion loss decreased with increasing amount of codeposits and reached a constant value 2.4 percent by volume percent of BN particle. The wear resistance and the friction coefficient of the heat treated BN composite coatings were improved about three times than that of as-coatings. The BN composite coatings were more wear resistance than hard chromium. Ni-B-BN composite coatings showed lower wear resistance and friction coefficient than Ni-P-BN. The BN content of the deposite was found to be 2.4 v/o for these optium conditions.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.7-11
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• 2010

The reduction of optical losses in mono-crystalline silicon solar cell by surface texturing is a critical step to improve the overall cell efficiency. In this study, we have changed the sub-micrometer structure on the micrometer pyramidal structure by 2-step texturing. The Ag particles were coated on the micrometer pyramid surface in $AgNO_3$ solution, and then the etching with hydrogen fluoride and hydrogen peroxide created even smaller nano-pyramids in these pyramids. As a result, we observed that the changes of size and thickness of nano structure on pyramidal surface were determined by $AgNO_3$ concentration and etching time. Using 2-step texturing, the surface of wafers is etched to resemble the rough surface of a lotus leaf. Lotus surface can reduce average reflectance from 10% to below 3%. This reflectance is less than conventional textured wafer including anti-reflection coating.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.8
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• pp.1044-1048
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• 2008

Bacillus polyfermenticus KJS-2 (Bp2) was isolated from $Bispan^{(R)}$, a commercially available probiotics consisting of more than 4 strains. The objective of this study was to investigate the effect of three-layer coating on the stabilty of Bp2. Bp2 was microencapsulated with sodium alginate using an air atomizer. The Bp2 loaded pellets were also coated with HFP-chitosan and HPMCP for oral delivery system. When compared to the uncoated Bp2, the survival of the three-layer coated Bp2 increased to approximately 63% (p<0.01) in a 30% ethanol solution, 54% (p<0.05) in an artificial gastric juice (pH 2), and 53% (p<0.05) in the bile acid (pH 5). When coated beads were stored at $100^{\circ}C$ and $130^{\circ}C$, Bp2 in coated beads was very stable (p<0.01) compared to uncoated Bp2.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.148-148
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• 2017

Surface modification is a type of mechanical manipulation skills to achieve extensive aims including corrosion control, exterior appearance, abrasion resistance, electrical insulation and electrical conductivity of substrate materials by generating a protective surface using electrical, physical and chemical treatment on the surface of parts made from metallic materials. Such surface modification includes plating, anodizing, chemical conversion treatment, painting, lining, coating and surface hardening; this study conducted cavitation experiment to assess improvement of durability using anodizing. In order to observe surface characteristics with applied current density, the electrolyte temperature, concentration was maintained at constant condition. To prevent hindrance of stable growth of oxide layer due to local temperature increase during the experiment, stirring was maintained at constant speed. In addition, using galvanostatic method, it was maintained at processing time of 40minutes for 10 to $30mA/cm^2$. The cavitation experiment was carried out with an ultra sonic vibratory apparatus using piezo-electric effect with modified ASTM-G32. The peak-to-peak amplitude was $30{\mu}m$ and the distance between the horn tip and specimen was 1mm. The specimen after the experiment was cleaned in an ultrasonic bath, dried in a vacuum oven for more than 24 hours, and weighed with an electric balance. The surface damage morphology was observed with 3D analysis microscope. As a result of the study, differences were observed surface hardness and anti-cavitation characteristics depending on the development of oxide film with the anodizing process time.

• Journal of the Korean Magnetics Society
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• v.24 no.6
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• pp.186-190
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• 2014

To establish the coating conditions for $^{57}Co$, non-radioactive Co ions are dissolved in an acid solution and electroplated on to a copper plate. Then, the thermal diffusion of electroplated Co into a copper matrix was studied to apply a $^{57}Co$ $M{\ddot{o}}ssbauer$ source. Nanocrystalline Co particles were coated on a Cu substrate using DC electro-deposition at a pH of 1.89 to 5 and $20{\sim}30mA/cm^2$. The average grain size was up to 54 nm as the pH increased to 5. The second phase of Co-oxide was formatted as the pH was increased above 4. The diffusion degree was evaluated by mapping using scanning electron microscopy (SEM). The influence of different annealing conditions was investigated. The diffusion depth of Co depends on the annealing temperature and time. The results obtained confirm that the deposited Co diffused almost completely into a copper matrix without substantial loss at an annealing temperature of $900^{\circ}C$ for 2 hours.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.162-162
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• 2014

최근 들어 wearable computing에 대한 수요가 증가하면서 flexible device에 대한 연구가 활발히 진행되고 있다. 하지만, flexible device를 구현하기 위해서는 기판의 damage를 줄이기 위한 저온공정, device life-time 향상을 위한 passivation, 와이어 본딩 등 다양한 문제들이 해결 되어야 한다. 이러한 문제들 중, polymer 기판과 금속간의 접착력을 향상시키기 위해서 많은 연구자들은 기판의 표면에 adhesive layer를 도포하거나 금속잉크의 solvent를 변화시키는 등의 연구를 진행해왔다. 종래의 연구는 기존 device를 대체 할 수 있을 정도의 생산성과 polymer 기판에 대한 열 적인 손상 이 문제가 되었다. 종래의 문제를 해결하기 위하여 저온공정, in-line system이 가능한 준 준 대기압 플라즈마를 사용하였다. 본 연구에서는 금속잉크를 Ink-jet으로 jetting하여 와이어 본딩 하는 과정에서 전도성 ink의 선폭을 유지시키고 접착력을 향상하기 위하여 준 대기압 플라즈마 공정을 이용하여 이러한 문제점을 해결하고자 하였다. Polymer 기판 표면에 roughness를 만들기 위해 대략 수백 nm 크기를 갖는 graphene flake를 spray coating하여 마스크로 사용하고 준 대기압 플라즈마를 이용하여 표면을 식각 함으로써 roughness를 형성시켰다. 준 대기압 플라즈마를 발생시키기 위해 double discharge system에서 6 slm/1.5 slm (He/O2) gas composition을 하부 전극에 흘려보내고 60 kHz, 5 kV 파워를 인가하였다. 동시에 상부 전극에는 30 kHz, 5 kV 파워를 인가하여 110초 동안 표면 식각 공정을 진행하였다. Graphene flake mask가 coating되어 있는 유연기판을 산소 플라즈마 처리 한 후 물에 3초 동안 세척하여 표면에 남아있는 graphene flake를 제거하고 6 slm/0.3 slm (He/SF6)의 유량으로 주파수와 파워 모두 동일 조건으로 110초 동안 표면 처리를 하였다. Figure 1은 표면 개질 과정과 graphene flake를 mask로 사용하여 얻은 roughness 결과를 SEM을 이용하여 관찰한 결과이다. 이와 같이 실험한 결과 ink와 기판간의 접촉면적을 늘려주고 접촉 각을 조절하여 Wenzel model 을 형성 할 수 있는 표면 roughness를 생성하였고 표면의 화학적 결합을 C-F group으로 치환하여 표면의 물과 접촉각 이 $47^{\circ}$에서 $130^{\circ}$로 증가하는 것을 확인하였다.

• Journal of the Korean Ceramic Society
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• v.47 no.4
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• pp.283-289
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• 2010

Physical properties of Plasma electrolytic oxidized 8 different kinds of Al alloys, A-1100, A-2024, A-5052, A-6061, A-6063, A-7075, ACD-7B and ACD-12 were investigated. The electrolyte for PEO was $Na_2SiO_3$ and NaOH and some alkali earthen metal salts system solution. $\eta$-alumina, as well as $\gamma$-alumina, was main crystal phase, which were ever reported. Also, $Al_{4.95}Si_{1.05}O_{9.52}$ was found only in this research. So we can conclude that the process conditions of PEO apparatus and composition and concentration of its electrolyte affects crystal structure and physical properties of PEO layers much more than the compositions of Al alloy.

• Journal of Pharmaceutical Investigation
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• v.38 no.2
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• pp.105-110
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• 2008

Indapamide (4-chloro-N-(2-methyl-1-indolinyl)-3-sulfamoyl-benz-amide) is an oral antihypertensive diuretic agent indicated for the treatment of hypertensive. The diuretic and natriuretic effects are mainly due to the structure of o-chlorobenzenesulfonamide. The objective of this study was to formulate sustained release indapamide granules and assess their formulation variables. Granules were prepared by fluid bed coating method and consist of drug layer and membrane layer. The granules were coated with HPC and ethyl cellulose along with plasticizer dibuthyl sebacate. The release of indapamide depended on the type of Eudragit such as RS and NE 30 D used in the formulation controlled release layer. These results obtained clearly suggest that the sustained release oral delivery system for indapamide could be designed with satisfying drug release profile approved.

• Journal of Animal Science and Technology
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• v.56 no.8
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• pp.29.1-29.6
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• 2014

This study compared the effects of varying lipid content and dietary concentration of a lipid-encapsulated (LE) ZnO product to those of native ZnO and thereby to find insights into optimal lipid coating and dosage of the Zn supplement. A total of 192 21-d-old weanling pigs were allotted to 48 pens, after which each six pens received a ZnO-free basal diet supplemented with 125 ppm ZnO (100 ppm Zn; BASAL), 2,500 ppm Zn as native ZnO (HIGH), or 100 or 200 ppm Zn as LE ZnO (LE-100 or LE-250) containing 8%, 10%, or 12% lipid [LE-8%, LE-10%, or LE-12%, respectively; $2{\times}3$ factorial arrangement within the LE-ZnO diets (LE-ALL)] for 14 d. Forty pigs were killed at the end for histological and biochemical examinations. None of ADG, ADFI, gain:feed, and fecal consistency score differed between the LE-ALL and either of the BASAL and HIGH groups. Hepatic and serum Zn concentrations were greater (p <0.05) in the HIGH vs. LE-ALL group, but did not differ between LE-ALL and BASAL, between LE-100 and -250, or among LE-8%, -10%, and -12% groups. Villus height (VH), crypt depth (CD), and the VH:CD ratio in the duodenum, jejunum, and ileum did not differ between the LE-ALL and either of the BASAL and HIGH groups, except for a greater CD in the duodenum in the LE-ALL vs. HIGH group. Additionally, VH and CD in the duodenum and VH:CD in the jejunum were greater in the LE-250 vs. LE-100 group. Specific activities of sucrase, maltase, and leucine aminopeptidase in these intestinal regions and those of amylase and trypsin in the pancreas were not influenced by the lipid content or dietary concentration of LE ZnO and also did not differ between the LE-ALL and either of the BASAL and HIGH groups, except for a greater pancreatic amylase activity in the former vs. HIGH group. In conclusion, the present results indicate that the LE ZnO, regardless of its lipid percentage or supplementation level examined in this study, has no significant effect on growth performance, fecal consistency, or digestive enzyme activities of weanling pigs under the experimental conditions.

• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1719-1723
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• 2009

The LiFeP$O_4$ powder was synthesized by using the solid state reaction method with Fe($C_2O_4){\cdot}2H_2O,\;(NH_4)_2HPO_4,\;Li_2CO_3$, and chitosan as a carbon precursor material for a cathode of a lithium-ion battery. The chitosan added LiFePO4 powder was calcined at 350 ${^{\circ}C}$ for 5 hours and then 800 ${^{\circ}C}$ for 12 hours for the calcination. Then we calcined again at 800 ${^{\circ}C}$ for 12 hours. We characterized the synthesized compounds via the crystallinity, the valence states of iron ions, and their shapes using TGA, XRD, SEM, TEM, and XPS. We found that the synthesized powders were carbon-coated using TEM images and the iron ion is substituted from 3+ to 2+ through XPS measurements. We observed voltage characteristics and initial charge-discharge characteristics according to the C rate in LiFeP$O_4$ batteries. The obtained initial specific capacity of the chitosan added LiFeP$O_4$ powder is 110 mAh/g, which is much larger than that of LiFeP$O_4$ only powder.