• 한국주조공학회지
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• 제38권3호
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• pp.60-65
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• 2018

In the present study, the characteristics of Mg inverter cases for hybrid cars are investigated. Concerns over the use of lightweight materials to reduce energy use and to mitigate emission problems are inevitable in the twenty-first century. Magnesium is a promising material for the manufacturing of lightweight parts. Several cases for thermal cooling channels have been designed and simulated, and the effects of materials and coatings on the thermal cooling efficiency have been discussed. The effects of the coating thickness on heat extraction in an Mg inverter housing case using the PEO (plasma electrolyte oxidation) coating method were also discussed. In order to produce an inverter case by the diecasting process, the filling sequence and cooling behavior during the diecasting process were simulated. The optimized process conditions from the simulation result were then used in a trial diecasting experiment.

• Macromolecular Research
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• 제12권5호
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• pp.534-539
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• 2004

Two biopolymers, silk fibroin (SF) and chitosan, were conjugated by tyrosinase (EC 1.14.18.1), a polyphenolic oxidase, to improve their physicochemical properties, such as their thermal properties and morphological stabilities in organic solvents. The crosslinking between SF and chitosan took place mainly through Michael addition reactions. A main reaction between the amino groups in chitosan and o-quinone, the oxidation product of the tyrosyl residue in SF, was confirmed by UV spectroscopy. Measurements of viscosity and light scattering indicated that the crosslinked SF/chitosan conjugate was compact: it had a smaller particle size because of tight bonding forces between the SF and chitosan molecular chains. Thermal decomposition of SF/chitosan conjugates crosslinked by tyrosinase occurred at higher temperatures. The adhesiveness of the SF/chitosan conjugates decreased steadily as the crosslinking reaction progressed. We propose that this new crosslinking method be used for the preparation of silk fibroin/chitosan conjugates using tyrosinase. We expect that SF/chitosan conjugates crosslinked by tyrosinase can be used preferentially in biomedical applications because of its unique properties and non-toxicity.

• Transactions on Electrical and Electronic Materials
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• 제13권1호
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• pp.27-30
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• 2012

This paper proposes a micro gas sensor for measuring $H_2S$ gas. This is based on a $SnO_2$-CuO multi-layer thin film. The sensor has a silicon diaphragm, micro heater, and sensing layers. The micro heater is embedded in the sensing layer in order to increase the temperature to an operating temperature. The $SnO_2$-CuO multi layer film is prepared by the alternating deposition method and thermal oxidation which uses an electron beam evaporator and a thermal furnace. To determine the effect of the number of layers, five sets of films are prepared, each with different number of layers. The sensitivities are measured by applying $H_2S$ gas. It has a concentration of 1 ppm at an operating temperature of $270^{\circ}C$. At the same total thickness, the sensitivity of the sensor with multi sensing layers was improved, compared to the sensor with one sensing layer. The sensitivity of the sensor with five layers to 1 ppm of $H_2S$ gas is approximately 68%. This is approximately 12% more than that of a sensor with one-layer.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.376-376
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• 2012

Semiconductor nanowires (NWs) are future building block for nano-scale devices. Especially, Ge NWs are fascinated material due to the high electrical conductivity with high carrier mobility. It is strong candidate material for post-CMOS technology. However, thermal stability of Ge NWs are poor than conventional semiconductor material such as Si. Especially, when it reduced size as small as nano-scale it will be melted around CMOS process temperature due to the melting point depression. Recently, Graphene have been intensively interested since it has high carrier mobility with single atomic thickness. In addition, it is chemically very stable due to the $sp^2$ hybridization. Graphene films shows good protecting layer for oxidation resistance and corrosion resistance of metal surface using its chemical properties. Recently, we successfully demonstrated CVD growth of monolayer graphene using Ge catalyst. Using our growth method, we synthesized Ge/graphene core/shell (Ge@G) NW and conducted it for highly thermal stability required devices. We confirm the existence of graphene shell and morphology of NWs using SEM, TEM and Raman spectra. SEM and TEM images clearly show very thin graphene shell. We annealed NWs in vacuum at high temperature. Our results indicated that surface melting phenomena of Ge NWs due to the high surface energy from curvature of NWs start around $550^{\circ}C$ which is $270^{\circ}C$ lower than bulk melting point. When we increases annealing temperature, tip of Ge NWs start to make sphere shape in order to reduce its surface energy. On the contrary, Ge@G NWs prevent surface melting of Ge NWs and no Ge spheres generated. Furthermore, we fabricated filed emission devices using pure Ge NWs and Ge@G NWs. Compare with pure Ge NWs, graphene protected Ge NWs show enhancement of reliability. This growth approach serves a thermal stability enhancement of semiconductor NWs.

• 한국식품영양과학회지
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• 제31권1호
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• pp.21-25
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• 2002

당-단백질의 가열반응 시에 생성되는 향기성분의 형성에 지질의 산화생성물이 어떠한 영향을 미치는가를 알아보고자 casein과 glucose(CG) 그리고 지질을 첨가한 사료(CGL)를 6$0^{\circ}C$에서 각각 2, 4주씩 저장한 후에 pressure reactor에 넣어 16$0^{\circ}C$에서 60분 가열 반응시킨 시료에서 향기성분을 추출하였다. Casein, glucose, 지질(CGL) 시료에서 단백질과 환원당의 반응물이 지질의 산화생성물과 반응하여 생성된 함질소 헤테로 고리화합물인 pyrazine, methylpyrazine과 2,5-dimethylpyrazine, 2-ethyl-5-methylpyrazine과 2-acetylpyrrole이 확인되었다. 또한 지질의 가열산화 분해성분인 3-methyll-butanol, heptanal, nonanal, 2-heptanone과 짧은 사슬의 지방산인 heptanoic acid, octanoic 가 검출되었다. 또 다른 화합물로 2-acetylfuran이 검출되었으며 glucose의 분해산물인 5-hdroxymethyl-2-furfural은 aems 시료에서 가장 큰 peak로 그 함량이 현저하게 많았다. 이상의 결과로 보아 시료에 첨가된 지질은 당-단백질 가열반응 시 생성되는 향기성분의 수와 그 함량을 증대시키는 작용을 하였다고 할 수 있다

• Journal of Welding and Joining
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• 제26권4호
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• pp.50-54
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• 2008

In this research, anode for SOFC has been manufactured from two different kinds of feedstock materials through thermal spraying process and the properties of the coatings were characterized and compared. One kind of feedstock was manufactured from spray drying method which includes nano-components of NiO, YSZ (300 nm) and graphite. And the other is manufactured by blending the micron size NiO coated graphite, YSZ and graphite powders as feedstock materials. Microstructure, mechanical properties and electrical conductivity of the coatings as-sprayed, after oxidation and after hydrogen reduction containing nano composite which is prepared from spray-dried powders were evaluated and compared with the same properties of the coatings prepared from blended powder feedstock. The coatings prepared from the spray dried powders has better properties as they provide larger triple phase boundaries for hydrogen oxidation reaction and is expected to have lower polarization loss for SOFC anode applications than that of the coatings prepared from blended feedstock. A maximum electrical conductivity of 651 S/cm at $800^{\circ}C$ was achieved for the coatings from spray dried powders which much more than that of the average value.

• 한국수소및신에너지학회논문집
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• 제24권1호
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• pp.29-35
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• 2013

A dense mixed ionic and electronic conducting ceramic membrane is one of the most promising materials because it can be used for separation of oxygen from the mixture gas. The $ABO_3$ perovskite structure shows high chemical stability at high temperatures under reduction and oxidation atmospheres. $BaCo_{1-x-y}Fe_xZr_yO_{3-{\delta}}$ (BCFZ) was well-known material as high mechanical strength, low thermal conductivity and stability in the high valence state. Glycine Nitrate Process (GNP) is rapid and effective method for powder synthesis using glycine as a fuel and show higher product crystallinity compared to solid state reaction and citrate-EDTA method. BCFZ was fabricated by modified glycine nitrate process. In order to control the burn-up reaction, $NH_4NO_3$ was used as extra nitrate. According to X-Ray Diffraction (XRD) results, BCFZ was single phase regardless of Zr dopants from y=0.1 to 0.3 on B sites. The green compacts were sintered at $1200^{\circ}C$ for 2 hours. Oxygen permeability, methane partial oxidation rate and hydrogen production ability of the membranes were characterized by using Micro Gas Chromatography (Micro GC) under various condition. The high oxygen permeation flux of BCFZ 1-451 was about $1ml{\cdot}cm^{-2}s^{-1}$. Using the humidified Argon gas, BCFZ 1-433 produced hydrogen about $1ml{\cdot}cm^{-2}s^{-1}$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.243.2-243.2
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• 2015

We report a high-performing nanoscale NiO thin film grown by thermal oxidation of sputtered Ni film. The structural, physical, optical and electrical properties of nanoscale NiO were comprehensively investigated. A quality transparent heterojunction (NiO/ZnO) was formed by large-area applicable sputtering deposition method that has an extremely low saturation current of 0.1 nA. Considerable large rectification ratio of more than 1000 was obtained for transparent heterojunction device. Mott-Schottky analyses were applied to develop the interface of NiO and ZnO by establishing energy diagrams. Nanoscale NiO has the accepter carrier concentration of the order of 1018 cm-3. Nanoscale NiO Schottky junction device properties were comprehensively studied using room temperature impedance spectroscopy.

• 한국염색가공학회지
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• 제17권1호
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• pp.38-44
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• 2005

Oxidation method was used to extract S-keratose from wool. Wool was treated with performic acid and soluble fraction(S-keratose) was collected by evaporating the solvent. S-keratose and Nylon 6 were dissolved in formic acid at the ratio of 100/0, 80/20, 50/50, 20/80, and 0/100, and S-keratose/Nylon 6 web of sub-micron size was made by electro-spinning technique. SEM, EA, FT-IR, XRD, and TGA were used to characterize the properties of S-keratose/Nylon 6 solutions and electrospun fibers. As the Nylon 6 content increased, viscosity, conductivity of the electrospinning solution and the diameter of spun fiber increased. Electrospun nonwoven webs have the same S-keratose/Nylon 6 ratios of the spinning solutions. The crystalline structures of S-keratose and Nylon 6 existed separately in the electrospun webs. Thermal stability of the webs increased due to Nylon 6 content.

• 폴리머
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• 제34권6호
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• pp.553-559
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• 2010

The paper describes the preparation and characterization of conductive polyaniline-modified polymers by growing of aniline onto functionalized poly(styrene-co-p-methylstyrene) [P(St-co-MSt)]. For this purpose, P(St-co-MSt) was synthesized via nitroxide mediated radical polymerization (NMRP) and then N-boromosuccinimide was used for introduction of bromine to the benzylic positions of copolymer. Afterwards, 1,4-phenylenediamine was linked to the brominated P(St-co-MSt) and functionalized copolymer $[P(St-co-MSt)-NH_2]$ was prepared. The graft copolymerization of aniline monomers onto functionalized P(St-co-MSt) was initiated by oxidized phenylamine groups after addition of ammonium peroxydisulfate (APS), and p-toluenesulfonic acid-doped PANI was chemically grafted onto P(St-co-MSt) via oxidation polymerization. The obtained terpolymer was studied by FTIR and UV-Vis spectroscopy and its thermal behaviour were examined by DSC and TGA analyses. The conductivity of terpolymer was measured by four-point probe method and electroactivity was measured by cyclic voltammetry (CV). The solubility of P(St-co-MSt)-g-PANI was examined in common organic solvents.