• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.160-161
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• 2007

3,3-Dimethyl-1-butene ($C_6H_{12}$) monomer를 이용하여 RF power와 압력에 따라 막을 증착하였다. 증착된 막은 power/pressure (W/Torr)가 증가할수록 비정질 탄소막은 Raman 스펙트럼에서 D peak가 증가하였고, ring 구조의 막을 형성하였다. 또한 ring 구조의 막이 형성됨으로써 hardness와 modulus는 각각 12 GPa과 85 GPa로 선형적으로 증가하는 것으로 나타났다.

• Tribology and Lubricants
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• v.20 no.3
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• pp.125-131
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• 2004

Nano-wear behavior of amorphous carbon films was studied by Atomic Force Microscopy. The a-C films are deposited on Si(100) substrate by DC magnetron sputtering method. The influences of different surface roughness on the nano-wear are investigated. Nano-wear tests were carried out using a very sharp diamond coated tip. Its spring constant was 1.6 N/m and radius of curvature was 110 nm. Normal force used in the wear tests ranged 0 to 400 nN. It was found that surface depression occurred during scratching because of plastic deformation and abrasive wear (cutting St ploughing). Wear depth increased linearly with normal force. Changing the surface roughness variables according to the bias pulse control, the less surface roughness decreased the wear depth. The thickness did not affect the wear resistance.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.662-666
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• 2008

Electrochemical properties of carbon cryogel electrode for the application of composite electrode materials mixed with metal oxide in supercapacitor have been studied. Carbon cryogels were synthesized by sol-gel polycondensation of resorcinol with form aldehyde, followed by a freeze drying, and then pyrolysis in an inert atmosphere. Physical properties of carbon cryogel were characterized by BET, X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that carbon cryogel is amorphous material. The electrochemical properties of carbon cryogel were measured by cyclic voltammetry as a function of concentration of liquid electrolyte, galvanostatic charge-discharge with different scan rates and electrochemical impedance measurements. The result of cyclic voltammetry indicated that the specific capacitance value of a carbon cryogel electrode was approximately 150.2 F/g (at 5 mV/s in 6M KOH electrolyte).

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.124.3-124
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• 1998

• Journal of the Korean Society for Heat Treatment
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• v.31 no.4
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• pp.165-170
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• 2018

W, Fe, and carbon powders were mechanical alloyed to produce $W_{35}Fe_{43}C_{22}$ ternary alloy powders containing nanocrystal W embedded within amorphous matrix. When the powder samples were heated to the primary crystallization temperature of $735^{\circ}C$, most parts of their amorphous region were fully crystallized to [W,Fe]-rich $M_6C$ carbides. Interestingly, a little portion of the carbides changes to stoichiometric line compounds ($M_{12}C$ and $W_6Fe_7$) and a solution phase (Fe-rich bcc), and remaining parts of the crystallites were amorphized again. The resulting microstructure was retained even by cyclic heating between room temperature of $1,200^{\circ}C$, and thus we found that the amorphous structure can be irreversibly formed at above glass transition temperature.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1244_1245
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• 2009

Coating of amorphous nitride thin layers, such as boron nitride (BN) and carbon nitride (CN), has been performed on carbon nanotubes (CNTs) for the purpose of enhancing their electron-emission performances because those nitride films have relatively low work functions and commonly exhibit negative electron affinity behavior. The CNTs were directly grown on metal-tip (tungsten, approximately 500 nm in diameter at the summit part) substrates by inductively coupled plasma-chemical vapor deposition (ICP-CVD). Sharpening of the tungsten tips were carried out by electrochemical etching. Morphologies and microstructures of BN and CN films were analyzed by field-emission scanning electron microscopy (FE-SEM), energy dispersive x-ray (EDX) spectroscopy, and Raman spectroscopy. The electron-emission properties (such as maximum emission currents and turn-on fields) of the BN-coated and CN-coated CNT-emitters were characterized in terms of the thickness of BN and CN layers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.5
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• pp.403-406
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• 2019

We prepared yarned carbon nanotube (CNT) fibers from a CNT forest synthesized on a Si wafer by chemical vapor deposition (CVD). The yarned CNT fibers were thermally annealed to reduce their resistance by removing the amorphous carbonaceous impurities present in the fibers. The resistance of the yarned CNT fiber gradually decreased with an increase in the annealing temperature from $200^{\circ}C$ to $400^{\circ}C$ but increased again above $450^{\circ}C$. We carried out thermogravimetric analysis (TGA) to confirm the burning properties of the amorphous carbonaceous impurities and the crystalline CNTs present in the fibers. The pattern of the mass change of the sample CNT fibers was very similar to that of the resistance change. We conclude that CNT fibers should be thermally annealed at temperatures below $400^{\circ}C$ for reducing and stabilizing their resistance.

• Journal of the Korean institute of surface engineering
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• v.48 no.3
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• pp.87-92
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• 2015

Carbon thin films were deposited on STS 316L sheets by inductively coupled plasma enhanced magnetron sputtering with or without substrate bias voltage. Typical Raman spectrum for amorphous diamond-like carbon (DLC) was obtained, and the interfacial contact resistance (ICR) was measured to show its conductive nature. The electrochemical impedance spectroscopy (EIS) was used to investigate the corrosion mechanism of the carbon coating under the polymer electrolyte membrane fuel cell (PEMFC) condition. According to the pore-corrosion mechanism, the electrolyte penetrates the carbon coating through the pores and reacts with the substrate. As the substrate corrosion proceeds, the pore enlargement occurs and the surface area of the substrate exposed to the electrolyte. Applicability of the carbon coating for the PEMFC bipolar plate was evaluated by potentiodynamic polarization experiments. Finally, an adhesion problem was briefly considered.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04a
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• pp.27-30
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• 2004

Different types of hybrid negative materials on pitch based carbon and natural graphite for lithium ion batteries were studied. Two types of active materials were prepared, that is, pitch based graphite carbon, and pitch based carbon impregnating natural graphite. The specific capacity, capacity recovery in high temperature condition, and other electrochemical properties were achieved for these materials. We found that addition of natural graphite type to the pitch based carbon can significant1y improve the specific capacity and interfacial resistance. However, use of natural graphite will cause a serious capacity loss in the high temperature condition owing to its increasing interface resistance. The specific capacity ranged from 321 to 348 mAh/g and the maximum specific capacity was obtained in the case of pitch based carbon impregnating natural graphite.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1199-1202
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• 2004

리튬이온전지 음극활질용으로 Hybrid of pitch based graphite impregnating natural graphite와 Hybrid of pitch based carbon impregnating natural graphite로 탄소전극을 제작하여 전기화학적인 특성을 연구하였다. Natural graphite에 pitch based graphite나 pitch based carbon의 혼합은 흑연의 이론용량인 372 mAh/g를 초과하는 고용량을 나타내었다. 이것은 극소공동에 리튬종의 삽입과 탈삽입에 의한 것으로 파악된다. 그러나 충 방전이 계속 진행되면서 방전용량이 급격히 저하되는 현상이 관찰되었다. X-선 회절분석 결과로부터 Hybrid of pitch based carbon impregnating natural graphite 탄소전극에는 amorphous carbon이 상대적으로 다량 존재한다는 것을 확인하였고, 이는 리튬의 삽입된 상태의 전위에 분포가 있어 충 방전시에 완만한 전압의 구배를 만들며, 비가역용량을 증가시키는 요인으로 파악되었다.