• Journal of the Korean Chemical Society
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• v.41 no.1
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• pp.1-11
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• 1997

Electrode surface reaction on three carbon materials(glassy carbon, synthesized graphite, graphite foil) in 0.5 M K2SO4 electrolyte is investigated by impedance spectroscopy during anodic polarization. The double layer capacitance of the graphite foil electrode is relatively higher than that of other two materials. The change of capacitance parameter C due to chemical adsorption on glassy carbon and synthesized graphite(PVDF graphite) is observed in 0.5 M K2SO4 solution at anodic polarization. In general, the faradic impedance on glassy carbon depends on anodic polarization, and the change of impedance parameter on graphite foil at anodic polarization is not remarkable, because this reaction is controlled by field transport.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.571-583
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• 1996

The electrochemical behavior on electrographite and graphite foil electrode with porous surface in 0.5 M $K_{2}SO_{4}$ solution with 1 mM $[Fe(CN)_{6}]^{3-}/[Fe(CN)_{6}]^{4-}$ have been characterized by impedance spectroscopy. In cyclic voltammograms, relative high current according to structure of porous surface for graphite materials was represented, and indicated hgih double layer capacitance on graphite foil. The faraday-impedance and the change of impedance spectrum on both graphite materials were not remarkable during polarization by reaction of field transport. Chemical adsorption was represented on electrographite and was depended highly at anodic polarization.

• Journal of Sensor Science and Technology
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• v.23 no.4
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• pp.234-237
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• 2014

In this paper, a copper foil-thick grapheme (thin graphite sheet)-copper foil structure is reported to achieve mechanically strong and high thermal conductive layer suitable for heat spreading components. Since graphene provides much higher thermal conductivity than copper, thick graphene embedded copper layer can achieve higher effective thermal conductivity which is proportional to graphene/copper thickness ratio. Since copper is nonreactive with carbon material which is graphene, chromium is used as adhesion layer to achieve copper-thick graphene-copper bonding for graphene embedded copper layer. Both sides of thick graphene were coated with chromium as an adhesion layer followed by copper by sputtering. The copper foil was bonded to sputtered copper layer on thick graphene. Angstrom's method was used to measure the thermal conductivity of fabricated copper-thick graphene-copper structure. The thermal conductivity of the copper-thick graphene-copper structures is measured as $686W/m{\cdot}K$ which is 1.6 times higher than thermal conductivity of pure copper.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.10a
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• pp.173-177
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• 2005

리튬이온 2차전지(Lithium ion battery, LIB)는 기존에 사용되던 전지에 비해 에너지 밀도가 높고 충방전 사이클이 우수하다. 이 때문에 휴대전화와 노트북 등에 수요가 급속하게 증가하고 있으며 1995년 LIB의 생산량은 4천만 개에서 2004년에는 약 8억 개로 20배 이상 증가하였다. 이에 따라 폐LIB도 급속하게 증가하게 되어 전국적인 재활용 시스템의 확보가 필요한 실정이다. 본 연구에서는 폐LIB에 함유되어 있는 유가금속 중에서 리튬코발트옥사이드(이하 $LiCoO_2$)를 회수하기 위하여 분쇄기(orient vertical cutting mill)와 진동 Screen을 사용하여 유기분리막, 금속류(Aluminium foil, Copper foil, case 등) 그리고 전극물질(lithium cobalt oxide와 graphite 등의 혼합 분말)로 분리하였다. 전극물질에서 $LiCoO_2$와 graphite 분리를 위한 전처리 단계로서 $500^{\circ}C$ 정도의 열처리를 하여 $LiCoO_2$의 표면 성질을 변화시켜 부유선별에 의해 $LiCoO_2$와 graphite의 분리가 가능하도록 하였다. 부유선별 실험 결과 93% 이상의 순도를 가지는 $LiCoO_2$를 92% 이상 회수할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.353-358
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• 2013

The current interruption method is considered to be an efficient way of measuring the resistance of a fuel cell. In this study, the ohmic area specific resistances (ASRs) of polymer electrolyte fuel cells with different types of bipolar plates were evaluated using the current interruption method. The ohmic ASRs of both a fuel cell with graphite bipolar plates and a fuel cell with graphite foil-based assembled bipolar plates decreased as the current density increased. On the other hand, with increasing cell temperature, the ohmic ASRs of a fuel cell with graphite bipolar plates were decreased by a reduction in the proton transport resistance through the membrane, and the ohmic ASRs of a fuel cell with graphite foil-based assembled bipolar plates were increased by the differences in thermal expansion between different components of the bipolar plates.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1607-1610
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• 2009

The carbon-coated Si/Cu powder has been prepared by mechanical ball milling and hydrocarbon gas decomposition methods. The phase of Si/Cu powder was analyzed using X-ray diffraction (XRD), dispersive Raman spectroscopy, electron probe microanalysis (EPMA) and transmission electron microscope (TEM). The carbon-coated Si/Cu powders were used as anode active material for lithium-ion batteries. Their electrochemical properties were investigated by charge/discharge test using commercial LiCo$O_2$ cathode and lithium foil electrode, respectively. The surface phase of Si/Cu powders consisted of carbon phase like the carbon nanotubes (CNTs) with a spacing layer of 0.35 nm. The carbon-coated Si/Cu/graphite composite anode exhibited a higher capacity than commercial graphite anode. However, the cyclic efficiency and the capacity retention of the composite anode were lower compared with graphite anode as cycling proceeds. This effect may be attributed to some mass limitations in LiCo$O_2$ cathode materials during the cycling.

• Journal of Korea Foundry Society
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• v.31 no.5
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• pp.288-292
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• 2011

In order to complement the drawbacks of quartz crucible such as fragile-like break and melt-leakage through open slit nozzle, a new PFC system has been developed using a common graphite crucible and plugging system. The u melt is fed on to the rotating a roll through slit nozzle by self-gravity. The new equipment was designed and manufactured successfully. An effort for optimizing all related parameter has been made. Then using the optimized parameters about 10 meters u foil having very thin thickness, which meets the target thickness of 130 ${\mu}m$ and enough width more than 60 mm could be made. The thickness homogeneity set improved, due to the lower eddy flowing of the melt flow the self-gravity feeding system.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.80-80
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• 2010

Graphene has attracted tremendous attention for the last a few years due to it fascinating electrical, mechanical, and chemical properties. Up to now, several methods have been developed exclusively to prepare graphene, which include micromechanical cleavage, polycrystalline Ni employing chemical vapor deposition technique, solvent thermal reaction, thermal desorption of Si from SiC substrates, chemical routes via graphite intercalation compounds or graphite oxide. In particular, polycrystalline Ni foil and conventional chemical vapor deposition system have been widely used for synthesis of large-area graphene. [1-3] In this study, synthesis of mono-layer graphene on a Ni foil, the mixing ratio of hydrocarbon ($CH_4$) gas to hydrogen gas, microwave power, and growth time were systemically optimized. It is possible to synthesize a graphene at relatively lower temperature ($500^{\circ}C$) than those (${\sim}1000^{\circ}C$) of previous results. Also, we could control the number of graphene according to the growth conditions. The structural features such as surface morphology, crystallinity and number of layer were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM), transmission electron microscopy (TEM) and resonant Raman spectroscopy with 514 nm excitation wavelength. We believe that our approach for the synthesis of mono-layer graphene may be potentially useful for the development of many electronic devices.

• Korean Chemical Engineering Research
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• v.58 no.3
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• pp.466-473
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• 2020

Fabric current collector can be a promising electrode material for Capacitive Deionization (CDI) system that can achieve energy-efficient desalination of water. The one of the most attractive feature of the fabric current collector is its high tensile strength, which can be an alternative to the low mechanical strength of the graphite foil electrode. Another advantage is that the textile properties can easily make shapes by simple cutting, and the porosity and inter-fiber space which can assist facile flow of the aqueous medium. The fibers used in this study were made of woven structures using a spinning yarn using conductive LM fiber and carbon fiber, with tensile strength of 319 MPa, about 60 times stronger than graphite foil. The results were analyzed by measuring the salt removal efficiency by changing the viscosity of electrode slurry, adsorption voltage, flow rate of the aqueous medium, and concentration of the aqueous medium. Under the conditions of NaCl 200 mg/L, 20ml/min and adsorption voltage 1.5 V, salt removal efficiency of 43.9% in unit cells and 59.8% in modules stacked with 100 cells were shown, respectively. In unit cells, salt removal efficiency increases as the adsorption voltage increase to 1.3, 1.4 and 1.5 V. However, increasing to 1.6 and 1.7 V reduced salt removal efficiency. However, the 100-cell-stacked module showed a moderate increase in salt removal efficiency even at voltages above 1.5 V. The salt removal rate decreased when the flow rate of the feed was increased, and the salt removal rate decreased when the concentration of the feed was increased. This work shows that fabric current collector can be an alternative of a graphite foil.

• Korean Journal of Materials Research
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• v.31 no.5
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• pp.272-277
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• 2021

Owing to its low cost, easy fabrication process, and good ionic properties, aqueous supercapacitors are under strong consideration as next-generation energy storage devices. However, the limitation of the current collector is its poor electrochemical stability, leading to low energy storage performance. Therefore, a reasonable design of the current collector and the acidic electrolyte is a necessary, as well as interfacial engineering to enhance the electrochemical performance. In the present study, graphite foil, with excellent electrochemical stability and good electrical properties, is suggested as a current collector of aqueous supercapacitors. This strategy results in excellent electrochemical performance, including a high specific capacitance of 215 F g^-1 at a current density of 0.1 A g^-1, a superior high-rate performance (104 F g^-1 at a current density of 20.0 A g^-1), and a remarkable cycling stability of 98 % at a current density of 10.0 A g^-1 after 9,000 cycles. The superior energy storage performance is mainly ascribed to the improved ionic diffusion ability during cycling.