• Analytical Science and Technology
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• v.13 no.2
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• pp.200-207
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• 2000

The growth mechanisms of graphite spherulite both in the nodular cast iron and the high pressuretreated Ni-C alloy were investigated by SEM, HRTEM and EELS. The internal microstructure and lattice image of graphite spherulite extracted from Ni-C alloy were compared with those of graphite spherulite extracted from the nodular cast iron. The ratios of $sp^2$ and $sp^3$ bonding in the respective graphite spherulite measured by EELS, are compared each other. The graphite spherulite of Ni-C alloy had little internal defects and much $sp^3$ carbon species compared to that of the nodular cast iron. Present difference in microstructural features and bonding characters indicated that the graphite spheruites in the high pressuretreated Ni-C alloy grew by different mechanism compared with those in the nodular cast iron.

• Analytical Science and Technology
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• v.6 no.2
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• pp.149-156
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• 1993

The formation of the graphite spherulites has been studied experimentally in the Ni-C liquid under high pressure and temperature. In the diamond-stable region the graphite spherulites were formed and grew stably. They were not the polycrystalline particles but the single crystals of the fullerene-type, respectively, grown spirally with much imperfection. And they were proved to be in a mixture state of carbon atoms with $sp^2$- and $sp^3$-bonding by an Auger electron spectroscope and a high resolution transmission electron microscope. As the pressure decreased from the diamond-stable region to the graphite-stable region, the shape of the graphite particles changed gradually from the sphere to the flaky shape. The formation of the graphite spherulites was attributed to the stable existence of the carbon atoms with $sp^3$ bonding in the diamond-stable region. The formation of the large fullerene-type graphite spherulites with much imperfection is well agreed with Kroto's prediction for growth of the giant fullerene.

• Proceedings of the KSEEG Conference
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• 2001.04a
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• pp.308-310
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• 2001

유기물질이 오랜 기간동안 고온 고압하에서 탄화작용을 받아 생성된 천연흑연은 단위구조가 탄소육각망평면(炭素六角網平面)이 평행하게 배열된 층상으로 전기전도도 및 윤할성이 우수하나 소수성이 매우 강하며 표변화학적 특성이 거의 없기 때문에 다른 물질과 표면흡착이 매우 어려운 물질이다. 따라서 본 연구에서는 흑연의 표면특성을 변화시키고자 유기물(ABDM)을 흡착시키고 표면흡착 매커니즘 및 표면특성을 해석하였다. 흑연 입자 표면 위의 ABDM흡착은 두 단계의 서로 다른 게에서 이루어졌다. 첫 번째 단계는 흡착 초기 흑연입자와 ABDM의 표면전위 특성차이에 의한 1차 흡착으로 흑연표면 소수성이 더욱 증가하는 상태이고, 두 번째 단계는 1차 흡착된 ABDM 과 용액중의 ABDM chain 상호간의 steric 작용에 의한 2차 흡착이었다. 2차 흡착이 완료된 흑연입자 표면은 ABDM 이중층을 형성하게 되고 이에 따라 흑연의 표면전위 특성을 변화시킬 수 있었다.

• Composites Research
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• v.19 no.2
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• pp.7-12
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• 2006

Graphite particle/carbon fiber hybrid conductive polymer composites were fabricated by the compression molding technique. Graphite particles were mixed with an epoxy resin to impart the electrical conductivity in the composite materials. In this study, graphite reinforced conductive polymer composites with high filler loadings were manufactured to accomplish high electrical conductivity above 100S/cm. Graphite particles were the main filler to increase the electrical conductivity of composites by direct contact between graphite particles. While high filler loadings are needed to attain good electrical conductivity, the composites becomes brittle. So carbon fiber was added to compensate weakened mechanical property. With increasing the carbon fiber loading ratio, the electrical conductivity gradually decreased because non-conducting regions were generated in the carbon fiber cluster among carbon fibers, while the flexural strength increased. In the case of carbon fiber 20wt.% of the total system, the electrical conductivity decreased 27%, whereas the flexural strength increased 12%.

• Journal of Industrial Technology
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• v.20 no.B
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• pp.3-8
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• 2000

Low cycle fatigue life of spheroidal graphite cast iron is determined by the morphological parameters of internal graphite. The aim of this study is to clarify the effect of the number of nodular grain of spheroidal graphite cast iron on low cycle fatigue life. Two specimens that have identical average nodular grain size by changing nodular grain volume fraction and different number of nodular grain count was tested. In this paper, the parameter governing fatigue life through fatigue test, the number of nodular grain seriously affect fatigue life and nodular grain size is no longer governing parameter of it.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.89-90
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• 2006

The bipolar plate is a major component of the PEM fuel cell stack, which takes a large portion of stack cost. In this study, as alternative materials fur bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. Flow channels were fabricated by compression molding, and design of experiments (DOE) was applied to the tests to evaluate moldability. Results showed that land width and channel depth were two significant factors for moldability, and channel width had little influence on the moldability.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.75-84
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• 1993

Copper coating on graphite powders was carried out by cementation process from copper sulfate solution. Effects of operation variables such as copper ion concentration, stirring speed, reaction time and temperature were investigated to obtain optimum conditions for continuous and uniform copper coating on graphite powders. The activation energy of the copper coating process was found to be 3. 59kcal/mole.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.221-226
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• 1999

Two needle cokes (NC-A and NC-B) that differ in both the texture and impurity content to each other were graphitized at $2000-3000{\circ}C$, and the average particle size, size distribution and surface area were compared after milling. Their anodic properties in Li secondary batteries were also analyzed. Two materials showed a higher degree of graphitization with an increase in the preparation temperature, however, the NC-B series was less graphitized than NC-A due to the presence of impurities and less ordered mosaic texture. The mein particle size of the milled powder was proportional to the degree of graphitization, but the surface area showed the opposite trend. The highly graphitized materials yielded powders of lower uniformity in the size distribution. The discharge capacity of the resulting carbons steadily decreased in the temperature range of 1000 to $2000^{\circ}C$ due to the depletion of carbonaceous interlayers that contain crystal defects. A later increase in the discharge capacity was observed at $>2000^{\circ}C$, which arises from the formation of graphitic interlayers. The milling process gave rise to a sloping discharge curve at >1.0 V, but this was converted to a plateau at <0.25V after a repeated cycling or additional heat-treatment at $1000^{\circ}C$. The discharge at >1.0V likely comes from the disordered surface structure formed during the milling process. The evolution of a plateau at <0.25 V suggests that this disordered structure transforms to a more ordered graphitic one upon a cell cycling or heat-treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.233.2-233.2
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• 2016

Graphite의 순도, 결함, 결정층, 전기저항이 개선을 위하여, 10,000K 이상의 초고온 RF 열플라즈마 처리에 관한 연구를 수행하였다. 방전가스는 Ar을 사용하고, 특성 개선을 위하여 첨가가스로 $H_2$, $CH_4$을 첨가하여 흑연의 열플라즈마 처리에 의한 특성을 고찰하였다. Energy Dispersion Spectroscopy을 이용한 탄소 함량 분석 결과, 75wt% 저급 흑연에 함유된 유무기 불순물은 고온의 플라즈마에 의해 제거되어 99wt% 이상으로 순도가 개선되었고, XRD 및 Raman 분석으로부터 고온 열처리를 통한 탄소원자의 재배열로 흑연의 $sp^2$결함이 감소되고, 결정성이 향상됨을 확인하였다. 또한 열플라즈마로 처리된 흑연입자에 대한 분체저항 측정 결과, $10^{-3}{\Omega}{\cdot}cm$에서 $10{-4}{\Omega}{\cdot}cm$로 감소되었다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.341-342
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• 2002

미세탄소입자는 원소탄소(elemental carbon)와 유기탄소(organic carbon)로 분류할 수 있다. 원소탄소는 불완전연소 과정에 발생하는 검댕(black soot), 원유의 정제과정에 발생하는 흑연(graphite), 자연상태에서 만들어진 다이아몬드의 3가지 형태로 존재한다. 이들 중 대기환경에 영향을 미치는 요소는 검댕입자로서 입경은 l$\mu\textrm{m}$이하이며, 일정한 형태를 지니고 있지 않다. (중략)