• Carbon letters
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• 제28권
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• pp.9-15
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• 2018

In the aerospace field, Carbon/Cork composites have been used for rocket propulsion systems as a light weight structural component with a high bending stiffness and high thermal insulation properties. For the fabrication of a carbon composite with a heat insulation cork part, the bonding properties between them are very important to determine the service life of the Carbon/Cork composite structure. In this study, the changes in the interfacial adhesion and mechanical properties of Carbon/Cork composites under accelerated aging conditions were investigated. The accelerated aging experiments were performed with different temperatures and humidity conditions. The properties of the aged Carbon/Cork composites were evaluated mainly with the interfacial strength. Finally, the lifetime prediction of the Carbon/Cork composites was performed with the long-term property data under accelerated conditions.

• Nuclear Engineering and Technology
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• 제43권3호
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• pp.279-286
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• 2011

The aging degradation and lifetime assessment of a domestic class 1E Ethylene-Propylene-Diene-Monomer (EPDM), which is a popular insulating elastomer for electrical cables in the nuclear power plants, were studied for equipment qualification verification under the Loss of Coolant Accident (LOCA) conditions. The specimens were acceleratively aged, underwent a LOCA environment, as well as tested mechanically, thermo-gravimetrically, and spectroscopically according to the American Society of the Testing of Materials (ASTM) procedures. The tensile test results revealed that the elongation at break gradually decreased with an increasing aging temperature. The lifetime of EPDM aged isothermally at $140^{\circ}C$ was 1,316 hours and reduced to 1,120 hours after experiencing the severe accident test. The activation energies of the elongation reduction were $1.10{\pm}0.196$ eV and $0.93{\pm}0.191$ eV before and after the LOCA condition, respectively. The TGA test results also showed that the activation energy of the aging decomposition decreased from 1.35 eV to 1.02 eV after undergoing the LOCA environment. Although the mechanical property changes were discernibly observed during the aging process, along with the LOCA simulation, the FT-IR analysis showed that the spectroscopic peaks and their intensities did not alter significantly. Therefore, it can be concluded that the degradation of the domestic class 1E EPDM due to aging can be tolerable, even in severe accident conditions such as LOCA, and thus it qualifies as a suitable insulating material for electrical cables in the nuclear power plants.

• 한국임상수의학회지
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• 제24권2호
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• pp.201-207
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• 2007

The teat cup liner compounds with improved physical property were developed using tri-polymer blend of natural rubber(NR), ethylene propylene diene monomer rubber(EPDM) and butyl rubber, and the changes of the physical properties of compounds were measured under various conditions such as standard, thermal, alkaline detergent and acid solutions aging conditions. The hardness of the new teat cup liner compound 1 was 50 and that of the compound 2 was 51 under standard condition. The tensile strength and elongation of the new compound 1 were $154kgf/cm^2$ and 675% under the standard condition, respectively. Also, those of the new compound 2 were 180 kgf/cm and 634% under the same condition. Their hardness were increased about $2{\sim}6%$ and the tensile strength and elongation were decreased about 10% under the $25^{\circ}C$ water and detergent solutions. Even though the new teat cup liner compounds exhibited so much decreased tensile properties under the $105^{\circ}C$ thermal aged condition, they sustained more stable aged physical properties including tensile strength and elongation than those of imported teat cup liner materials. Consequently, the new teat cup liner compounds would give prolonged lift cycle if they are used as a teat cup liner product.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1162-1168
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• 2015

Accelerated thermal aging of chlorosulfonated polyethylene (CSPE) was performed for 0 days, 80.82 days, and 161.63 days at 100℃, which is equivalent to 0 y, 40 y, and 80 y of aging, respectively, at 50℃. After freshwater flooding, the volume electrical resistivity of CSPE was highest after 180 days of drying, and its insulating property recovered when dried for more than 300 days. The dielectric constant of the CSPE was not measured after seawater flooding. The dielectric constant of the accelerated thermally aged CSPE was higher after freshwater flooding than that before seawater flooding. The bright, open pores of CSPE were converted into dark, closed pores after seawater flooding, and the dark, closed pores of the accelerated thermally aged CSPE samples were partly converted into bright, open pores after freshwater flooding. The apparent density of CSPE increased slightly whereas its elongation at break (EAB) decreased until 80 y of accelerated thermal aging before seawater flooding. The peak binding energies of oxygen in the non-accelerated and accelerated thermally aged CSPE for 40 y and 80 y were shifted by more than 1.0 eV after seawater and freshwater flooding. The CH2 content in the non-accelerated and accelerated thermally aged CSPE for 40 y and 80 y after seawater flooding for 5 days was lower than that before seawater flooding whereas atoms such as Cl, O, Pb, Al, Si, Sb, and S that are related to conducting ions such as Na⁺, Cl^-, Mg²⁺, SO4 ^2-, and K⁺ were relatively increased.

• 한국전기전자재료학회논문지
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• 제19권3호
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• pp.280-286
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• 2006

As a way to expand electric capacity in conductor with electric power demand, STACIR/AW (Super Thermal-resistant Aluminum-alloy Conductors Aluminum-clad Invar-Reinforced) conductor which has high electric current and heat resistance characteristics have been developed. STACIR/AW power line is mechanical composite wire composed of steel cores for dip control and aluminum conductors for sending electric current. Recently, to ensure stable operation and prediction of wire life span of STACIR/AW conductor, a heat property of STACIR/AW conductor have been investigated. In the present work, a change of essential property with long term-heat exposure of STACIR/AW conductor and its structure material, INVAR wire and Al conductor, have been investigated. INVAR/AW is approximately $3.2\;{\mu}m/m^{\circ}C$. thermal expansion coefficient of INVAR/AW wire increases with time of heat exposure. the thermal expansion coefficient of INVAR/AW is markedly influenced by heat and mechanical treatment. creep rate(0.242) of STACIR/AW $410\;mm^2$ conductor at room temperature is much higher than that(0.022) at $210\;^{\circ}C$ STACIR/AW $410\;mm^2$ conductor has minimum creep rate at operating temperature. To lower creep rate with increase temperature is more unique characteristics in STACIR/AW. It is expected that STACIR/AW turned its tension to INVAR/AW at the transition temperature. at room temperature, the tension apportionment of INVAR/AW in STACIR/AW is about $50\;\%$. but whole tension of STACIR/AW is placed on the INVAR/AW alone of core metal above transition temperature.

• 한국화재소방학회논문지
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• 제22권2호
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• pp.44-48
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• 2008

본 논문은 몰드변압기용 에폭시수지의 열 열화특성을 고찰하기 위하여, 접촉각, 표면저항률 및 XPS를 측정하였다. 실험결과, 표면에서 재가교를 일으킴에 따라 접촉각은 $200^{\circ}C$까지는 증가하다가 $250^{\circ}C$에서는 열응축이 발생되어 접촉각이 감소하는 경향을 나타내었다. XPS분석을 통하여 산소/탄소 피크치를 조사한 결과, 최초 미처리의 시료에서는 탄소에 대한 산소의 피크치가 더 높게 나타났으나, 열처리 후에는 그와 반대되는 경향을 나타내었다. 이러한 탄소피크의 증가는 $200^{\circ}C$까지 나타났고 그 이상의 온도에서는 다시 감소하였다. 이것은 $200^{\circ}C$까지는 안정된 표면구조를 형성하다가 $250^{\circ}C$에서는 급격한 산화가 발생됨으로써 탄소결합이 파괴되었기 때문이다. 이는 급격한 표면활성화에 따른 친수화로 도전로가 쉽게 형성되었기 때문이다.

• Composites Research
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• 제31권4호
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• pp.122-127
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• 2018

섬유강화고분자복합재료(CFRP, Carbon Fiber Reinforced Plastics)의 경량화는 자동차 및 항공 분야에서 끊임없이 요구되고 있으며, 구조용 폼과 CFRP를 혼합하여 샌드위치 복합재료로 사용되고 있다. 본 연구에서는 열경화성 소재인 에폭시 폼과 폴리우레탄 폼 및 열가소성 소재인 PET 폼과 PVC 폼의 조성 차이에 따른 폼의 형상 및 열 노화를 통해 변화되는 기계적 특성 변화를 관찰하였다. 성형한 에폭시 폼, 폴리우레탄 폼 및 상용화된 PET 폼과 PVC폼을 180도에서 열 노화시켰으며, 30, 60, 120, 180분의 노화시간에 따라 구조용 폼의 변화를 광학 현미경 및 만능시험기로 폼 셀의 형상 및 압축강도를 평가하였다. 궁극적으로 에폭시 폼이 가장 높은 2.6 MPa의 압축강도를 가졌으며, 열 노화 조건에서도 물성저하나 형상의 변화가 거의 발생되지 않았다. 이는 에폭시 폼이 타 구조용 폼에 비해 열 노화 조건에서 후경화되어 강직한 조성을 이루며, 타 구조용 폼과는 다르게 내열 특성이 우수하기 때문에 고온용 구조용 폼으로 적용하기 적합한 소재임을 확인하였다.

• 접착 및 계면
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• 제7권4호
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• pp.39-44
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• 2006

A new kind of silicone-epoxy composite is reported in this research. The silicone-epoxy resin was synthesized by the hydrosilylation of tetramethycyclotetrasiloxane and 4-vinyl-1-cyclohexene 1,2-epoxy with a high reaction yield. It was found that the obtained silicone-epoxy resin shows a high reactive activity to the aluminum complex-silanol catalyst. The resin could be cured under the catalysis of $(Al(acac)_3/Ph_2Si(OH)_2$ at a concentration below 0.1 wt% to give a hard cured resin showing excellent optical clarity, UV resistance and thermal stability. It was also found that the Si-H groups facilitated the curing reaction and the silicone-epoxy resin bearing Si-H group could be cured effectively even if $Ph_2Si(OH)_2h$ was absent. Moreover, the UV resistance and thermal stability were improved significantly by the introduction of Si-H groups. This is possibly due to the reductive property of Si-H groups which can annihilate radical and peroxide effectively. This kind of silicone-containing epoxy composite might have very promising applications as optical resin, optical adhesive and encapsulation materials for electronic devices.

• 한국전기전자재료학회논문지
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• 제19권1호
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• pp.100-106
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• 2006

Today, restricted energy sources, environmental considerations and the high cost of transporting fuel have limited the number and location of available power plant sites. The pressures resulting from these conditions have tended to require the construction of long, high-capacity, high-voltage power lines. it's used to adapt to STACIR/AW(Super Thermal-resistant Aluminum alloy Conductors, aluminum-clad Invar-Reinforced) conductor for coping with these situations. STACIR/AW conductor was formed by the combination of INVAR/AW as the core for low sag and super thermal-resistant aluminum alloy conductor for current capacity increase. increase of temperature by current capacity and long span lines make the susceptible to the deterioration of thermo-mechanical properties(conductivity, tensile strength, E-modulus and twist property et al). In the present work, changes of thermo-mechanical properties with aging have been studied in STACIR/AW $410 mm^2$ conductor with forms of single wire and strand wire.

• 한국응용과학기술학회지
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• 제32권1호
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• pp.127-135
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• 2015

The aim of this study was to investigate the antioxidant activity of thermal treatment yam (Dioscorea batatas DECNE.) in Korea. Thermal treatment yam was extracted by different solvents including 70% methanol, 70% ethanol and chloroform-methanol mixture (CM, 2:1, v/v). Then color property, total phenol content and antioxidant activity were analyzed. Yam possessed high $L^*$ value and $H\limits^{\circ}$ value, which were $54.92{\pm}2.18$ and $73.20{\pm}0.77$, respectively. Thermal treatment yam exhibited great antioxidant activity evaluated by ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt] radical scavenging activity, DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity, reducing power, and ferric reducing antioxidant power. Total phenol contents of various extracts from thermal treatment yam increased in the following order: 70% methanol extract ($63.53{\pm}0.33mg\;CAE/g$), 70% ethanol extract ($69.47{\pm}1.00mg\;CAE/g$) and CM extract ($97.49{\pm}0.66mg\;CAE/g$), respectively. The same trend was also could be found in antioxidant activity assays except for reducing power assay. These results implied that these extracts from thermal treatment yam might be useful to take a good part in prevention of human diseases and aging.