• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.65-65
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• 2012

카테콜아민의 일종인 노레피네프린을 이용하면 다양한 물질의 표면을 효과적으로 개질시킬 수 있음이 최근 보고되었다. 단순한 표면 개질뿐만 아니라 OH- 작용기의 도입이 가능하다는 장점을 갖는 노레피네프린 코팅법은 산화그래핀 혹은 흑연과 같은 비활성 표면에까지 성공적으로 적용되었으며, 그 결과 생체 적합성을 갖는 기능성 표면이 개발되었다.

• Journal of the Korean Electrochemical Society
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• v.18 no.3
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• pp.130-135
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• 2015

The rate capability and low-temperature characteristics of graphite electrode are investigated after surface treatment with copper phthalocyanine (CuPc) or phthalocyanine (Pc). Uniform coating layers comprising amorphous carbon or copper are generated after the treatment. The rate performance of graphite electrodes is enhanced by the surface treatment, which is more prominent with CuPc. The resistance of the graphite electrode estimated from electrochemical impedance spectroscopy and pulse resistance measurement is the smallest for the CuPc-treated graphite. It is likely that the amorphous carbon layer formed by the decomposition of Pc facilitates $Li^+$ diffusion and the metallic copper derived from CuPc improves the electrical conductivity of the graphite electrode.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1091-1097
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• 2015

Graphite material has been widely used for making the rocket nozzle throat because of its excellent thermal properties. However, when compared with typical structural materials, graphite is relatively weak with respect to both strength and toughness, owing to its quasi-brittle behavior, and gets oxidized at $450^{\circ}C$. Therefore, it is important to evaluate the thermal and mechanical properties of this material for using it in structural applications. This study presents an experimental method to investigate the fracture behavior of ATJ graphite at elevated temperatures. In particular, the effects of major parameters such as temperature, loading, and oxidation conditions on strength and fracture characteristics were investigated. Uniaxial compression and tension tests were conducted in accordance with the ASTM standard at room temperature, $500^{\circ}C$, and $1,000^{\circ}C$. Fractography analysis of the fractured specimens was carried out using an SEM.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.3
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• pp.89-95
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• 2022

In this study, glassy carbon coating was performed on the graphite using a phenolic resin and a curing agent was mixed with ethylene glycol as an additive to form the uniform surface. The phenolic resin was dried and cured under the environments of hot air, then converted into a glassy carbon layer by pyrolysis at 500~1,500℃. FTIR, XRD, SEM analysis, and density/porosity/contact angle measurement were performed for characterization of glassy carbon. The pyrolysis temperature for high-quality glassy carbon was optimized to be about 1,000℃. As the content of the additive increased, the effect of reducing surface defects on the coated surface, reduction of porosity, increase of contact angle, and increase of density were investigated in this study. The method of forming a glassy carbon coating layer through an additive is expected to be applicable to graphite coating and other fields.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.185-185
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• 2016

아크릴계 수지(resin)에 인조 흑연과 탄소나노튜브(carbon nanotube)를 1:1 비율로 혼합한 충전제(filler)와 용제(solvent) 및 기타 첨가제(additives)를 혼합하여 방열도료를 제조하여 수직방향 열전도도를 상온에서 평가하였다. 충전제의 함량을 1, 2, 5 중량 %로 변화시키며 원료들을 준비하여 교반기로 혼합한 뒤 3단 롤 밀(three roll mill)로 분산공정을 진행하여 3 종류의 도료를 제조하였다. 제조한 도료를 가로 11 mm, 세로 11 mm, 두께 0.4 mm의 Al 5052 알루미늄 기판에 스프레이 코팅 방식으로 도포한 후 $150^{\circ}C$에서 30분 동안 열경화 건조 과정을 거쳐 샘플을 제작하였다. 측정 시료의 형상은 대략적으로 Fig. 1과 같다. 열전도도는 식 $k={\alpha}{\cdot}C_p{\cdot}{\rho}$를 사용해서 계산된다. 여기서 k는 열전도도($W/m{\cdot}K$), ${\alpha}$는 열확산계수($mm^2/s$), $C_p$는 비열($J/kg{\cdot}K$), ${\rho}$는 밀도($g/cm^3$)를 나타낸다. 열확산계수는 독일 NETZSCH 사의 Laser Flash Analysis 장비(모델명 LFA 457)를 사용하여 측정하였는데, 기판 뒤쪽에서 레이저를 조사하고 도료층 전면에서 적외선 온도센서를 통해 시간에 따른 온도 상승곡선을 구한 후, 두 물체의 계면에서의 접촉 열저항(contact thermal resistance)을 감안하여 장비에 내장되어 있는 소프트웨어로 열확산계수가 계산된다. 비열은 같은 회사의 DSC(Differential Scanning Calorimetry) 200 F3 장비를 사용해 측정했으며, 밀도는 부피와 질량을 측정한 값을 이용하여 계산하였다. 도료를 도포하지 않은 bare Al plate에 대해서는 쉽게 열확산계수, 비열, 밀도를 측정하여 열전도도를 구할 수 있다. 도료가 코팅된 샘플에 대해서는 도료층을 일부 떼어내 비열을 측정하고, 밀도를 구한 후, 도료층의 열전도도가 2-layer 법으로 장비 내장 소프트웨어로 계산된다, 이때 Al 기판의 열확산계수, 비열, 밀도는 미리 측정한 bare Al plate의 값을 적용하였다. 실험 결과를 Table 1에 정리하였다. 흑연과 탄소나노튜브를 혼합한 충전제를 함유한 아크릴 복합체 박막에서 측정된 열전도도는 보통 고분자 재료의 열전도도 값의 상한 영역에 육박하는 값이며, 충전제 함량이 증가할수록 열전도도가 증가하는 경향을 보이고 있다.

• Composites Research
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• v.34 no.3
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• pp.148-154
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• 2021

Carbon/epoxy composite bipolar plate (BP) is a BP that is likely to replace existing graphite bipolar plate of vanadium redox flow cell (VRFB) due to its high mechanical properties and productivity. Multi-functional carbon/epoxy composite BP requires graphite coating or additional surface treatment to reduce interfacial contact resistance (ICR). However, the expanded graphite coating has the disadvantage of having low durability under VRFB operating conditions, and the surface treatments incur additional costs. In this work, an excessive resin absorption method is developed, which uniformly removes the resin rich area on the surface of the BP to expose carbon fibers by applying polyester fabric. This method not only reduces ICR by exposing carbon fibers to BP surfaces, but also forms a unique ditch pattern that can effectively hold carbon felt electrodes in place. The acidic environmental durability, mechanical properties, and gas permeability of the developed carbon/epoxy composite BP are experimentally verified.

• Resources Recycling
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• v.19 no.1
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• pp.27-32
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• 2010

To improve electronic conductivity of cathodic active materials of lithium ion battery, carbonaceous materials is usually added. New mixing method of abrasive milling has been investigated in mixing of graphite and $LiCoO_2$ powders. It would be expected that uniform mixing of graphite reduces capacity fading of cathode of lithium battery. Abrasion milled $LiCoO_2$ composite showed the best electrochemical performance as a cathode material with 1 wt% of graphite content, 300 rpm of milling speed, and 10 min of milling time. The improvement of the electrochemical performances such as cycleability and charge/discharge capacity retention would be mainly attributed to increase of the electronic conductivity and/or prevention of the active materials by uniform dispersion and coating of graphite on $LiCoO_2$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.279-279
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• 2010

한국형 헬륨 냉각 고체형 증식(Helium Cooled Solid Breeder : HCSB) 시험 블랑켓(Test Blanket Module : TBM)은 삼중수소 증식을 위해서 $Li_2TiO_3$ 및 $Li_4SiO_4$ 페블을 고려하고 있으며, 중성자 반사 재료로는 SiC가 코팅된 흑연 페블을 사용할 예정이다. $Li_2TiO_3$ 및 $Li_4SiO_4$ 페블을 제조하기 위해서는 먼저 각각의 분말 제조가 선행되어야 한다. $Li_2TiO_3$ 분말을 합성하기 위해서는 먼저 Lithium 금속염과 Isopropoxide를 용매 및 폴리머 캐리어로서의 두 가지 기능을 하는 에틸렌글리콜에 첨가한 후 가열하여 완전히 용해시킨 후 혼합 용액을 건조시켜 겔형의 전구체를 제조한다. 이를 하소한 후 결정화시켜 Titanate 분말을 얻는데 이때의 건조, 하소 및 결정화 온도의 조건에 따른 분말의 크기 및 특성이 각각 다르다. 즉 하소 온도가 $600^{\circ}C$ 미만이면 열분해된 폴리머로부터 잔유 탄소가 남게 되고, $700^{\circ}C$를 초과하면 결정화가 시작된다. 이렇게 얻어진 Titanate분말은 지르코니아 볼을 이용하여 약 24 시간 동안 볼 밀링 과정을 통해 입도분포가 좁은 미세한 Titanate 분말로 만들었다. $Li_2TiO_3$ 페블은 위의 과정에서 얻어진 미세분말에 바인더를 이용하여 페블화 시킨 후 $1200^{\circ}C$의 전기로에서 최종 소결한 것이다. 중성자 반사 재료인 흑연페블은 강도가 약하기 때문에 표면에 SiC를 수 ${\mu}m$ 코팅해서 사용할 예정이다. 선행실험으로 건식법을 이용하여 SiC 코팅을 실시했으며, 그 결과를 소개할 것이다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.8-12
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• 2012

Recently, a wide range of industrial production area has a competitive advantage through cost reduction. Moreover with the development of industrial technology, base material and cutting tool help the machining technology. But most of the machining enterprises have not hold the R&D facilities and human resources. This mainly disturbs the industrial development and th increase of production efficiency. Especially in the interrupted machining process, it showed different behavior with continuous machining process. So it needs to research and develop the tool life and tool wear mechanism analysis.

• The Journal of Natural Sciences
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• v.8 no.2
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• pp.137-146
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• 1996

To increase the oxidation-resistance of graphite substrate, we have tried to form SiC film on its surface by Sol-Gel method. TEOS(Tetraethyl orthosilicate) and phenol resin have been used as silicon(Si) and carbon(C) sources, respectively. In order to know the effect of the TEOS Sol concentration on the forming of SiC film, we have taken 5 different $H_2O$/TEOS mol ratios of 2, 4, 6, 8 and 10. And the coating states of SiC on the graphite substrate have been analyzed with X-ray diffractometer and scanning electron microscope (SEM), and we have obtained about 5${\mu}m$, 12${\mu}m$, 7${\mu}m$, 7${\mu}m$ and 2 ${\mu}m$ as the thickness of SiC coating layers, respectively. For also knowing the oxidation resistance the SiC coated graphites at $1600^{\circ}C$ were heated again at $1000^{\circ}C$ under air atmosphere for 1 hr, and as a result we have received the weight losses of 26.17%, 20.97%, 17.28%, 21.73% and 28.13%, respectively.