• Transactions on Electrical and Electronic Materials
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• 제15권6호
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• pp.338-343
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• 2014

A $Fe_3O_4$-graphite nanofiber composite for use as an anode material was successfully synthesized by calcining $Fe_3O_4$ and graphite nanofiber (GNF) together in a $N_2$ atmosphere. Using this $Fe_3O_4$-GNF composite in a lithium ion battery resulted in a higher lithium storage capacity than that obtained using $Fe_3O_4$-graphite ($Fe_3O_4$-G). The $Fe_3O_4$-GNF (10 wt%) electrode exhibited a higher lithium ion diffusion coefficient ($2.29{\times}10^{-9}cm^2s^{-1}$) than did the $Fe_3O_4$-G (10%) ($3.17{\times}10^{-10}cm^2s^{-1}$). At a current density of $100mA\;g^{-1}$, the $Fe_3O_4$-GNF (10 wt%) anode showed a higher reversible capacity ($1,031mAh\;g^{-1}$) than did the $Fe_3O_4$-G (10%) anode ($799mAh\;g^{-1}$). Moreover, the $Fe_3O_4GNF$ electrodes showed good cycling performance without the addition of a conductive material.

• 한국분말재료학회지
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• 제17권4호
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• pp.295-301
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• 2010

Multi shell graphite coated Ag nano particles with core/shell structure were successfully synthesized by pulsed wire evaporation (PWE) method. Ar and $CH_4$ (10 vol.%) gases were mixed in chamber, which played a role of carrier gas and reaction gas, respectively. Graphite layers on the surface of silver nano particles were coated indiscretely. However, the graphite layers are detached, when the particles are heated up to $250^{\circ}C$ in the air atmosphere. In contrast, the graphite coated layer was stable under Ar and $N_2$ atmosphere, though the core/shell structured particles were heated up to $800^{\circ}C$. The presence of graphite coated layer prevent agglomeration of nanoparticles during heat treatment. The dispersion stability of the carbon coated Ag nanoparticles was higher than those of pure Ag nanoparticles.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.85.1-85.1
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• 2011

In this study, Grafoil$^{TM}$ which has comparable electric resistance and chemical stability but is flexible, fragile, and cheap material was adopted as bipolar plates for proton exchange membrane fuel cell(PEMFC) having only one straight line flow channel. Because of its flexibility, pressurizations of cell with various pressures showed different operating characteristics compared to ordinary graphite-used PEMFC. While performances of both cells decreased as these were pressurized, investigation of ohmic and faradaic resistance by electrochemical impedance measurement indicated different tendency of change. Ohmic resistance of graphite-used cell increased with increasing pressure, which is reversed in Grafoil$^{TM}$-used cell. It is speculated that effective chemical reaction area is decreased with increasing pressure in case of graphite-used one, but because of flexible property of Grafoil$^{TM}$, gas diffusion layer in Grafoil$^{TM}$-used cell was well-activated. Different rate of change of faradaic resistances in both cells support this supposition. However, although optimum point of pressurization is found, it is required to investigate other operating conditions because of low performance compared to graphite-used cell.

• 한국결정성장학회지
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• 제6권4호
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• pp.648-662
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• 1996

임피던스 스펙트럼을 이용하여 황산 용액에서 glassy carbon과 인조흑연(PVDF 합성 흑연)의 전극표면에 cyclic 분극을 부하 하였을 경우 전극표면에서 나타나는 표면반응에 대하여 조사하여 . 두 재료 표면에서 산소의 산화 혹은 환원과 관련되거나 또는 탄소재료 표면에 화학흡착된 표면작용기(surface functional group)의 변화와 관련되는 것으로 생각되는 산화환원 피크가 potentio-dynamic곡선에서 나타났다. 이러한 전극 표면에서의 표면작용기의 산화환원은 glassy carbon과 PVDF합성 흑연의 임피던스 스펙트럼에도 커다란 영향을 미치는 것으로 나타났다. 또 glassy carbon과 PVDF합성 흑연에서의 임피던스 파라미터는 분극부하에의해 현저한 변화가 나타났다.가 나타났다.

• Journal of Electrochemical Science and Technology
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• 제9권4호
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• pp.320-329
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• 2018

Natural graphite is obtained from an abandoned open-cast mine and purified by a simple, eco-friendly and affordable beneficiation process including ball milling and flotation process. Both raw graphite (55 wt %) and its concentrate (85 wt %) were electrochemically tested in order to evaluate these materials as anode materials for Li-ion and Na-ion batteries. It was found that both raw and purified graphites exhibit good electrochemical activities with respect to lithium and sodium ions through completely different reaction mechanisms. The encouraging results demonstrated in this work suggest that both raw and graphite concentrates after flotation could be used respectively for stationary and embedded applications. This strategy would help in developing local electrical storage systems with a significantly low environmental footprint.

• 한국전기전자재료학회논문지
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• 제27권4호
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• pp.217-220
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• 2014

Graphite electrodes are used for secondary batteries, fuel cells, and super capacitors. Research is underway to increase the reaction area of graphite electrodes. In this study, we have investigated the growth properties of carbon nanowall (CNW) according to the ingredient of gas. Microwave plasma enhanced chemical vapor deposition (MPECVD) system was used to grow CNW on Si substrate with a variety of the reaction gas. The planar and vertical growth conditions of the grown CNWs according to the ingredient of the gas were characterized by a field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). The electrical characteristics of CNWs were analyzed using a 4-point probe.

• 한국세라믹학회지
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• 제26권4호
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• pp.583-587
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• 1989

Various $\alpha$-silicon carbied and colloidal graphite particles were sintered at 155$0^{\circ}C$ in vacuum atmosphere by reaction bonding sintering method, and the physical properties and microstructural analysis of specimen were investigated. With decreasing particle size, sintered density and 3-point bending strength of materials were increased and 3.2${\mu}{\textrm}{m}$ specimen showed high density and strength, 3.05g/㎤, 40kg/$\textrm{mm}^2$, respectively. The results of X-ray diffractometer and optical micrographs analysis showed that graphite and silicon melt reacted to convert to fine $\beta$-SiC particle and the body was changed to dense material.

• 한국세라믹학회지
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• 제32권9호
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• pp.1027-1032
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• 1995

SiC had been widely applied for mechanical sealing as a sealing material. SiC sintering is commonly made of reaction sintering, presureless sintering, and hot isostatic pressing (HIP) sintering. In this investigation, however, clay bonded sintering was used to avoide any complications of the special sintering methods as mentioned above. In order to prevent harmful SiC oxidation in the clay bonded sintering, clay and frit were used to form the SiC oxidation protecting layer and graphite was added to provide high solid lubricity. As a result, the material with 6% clay (clay 5.4% and frit 0.6%) and 2~4% graphite (45 mesh) sintered at 140$0^{\circ}C$ for 3 hours, showed the following physical properties; porosity 6%, static friction coefficient 0.15, kinematic coefficient 0.1,. and specific wear rate 4.8$\times$10-8 $\textrm{mm}^2$kgf-1. On the other hand, the flexural strength was 900kgf/$\textrm{cm}^2$. This tribological characteristic properties were similar to those of the reaction sintered SiC except the flexural strength.

• 한국세라믹학회지
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• 제31권4호
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• pp.399-406
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• 1994

The SiC/MoSi2 composite material was prepared by infiltration with the mixture of metal Si and MoSi2 into the preform of $\alpha$-SiC and graphite under the vacuum atmosphere of 10-1 torr. The mechanical properties, phases and microstructural characteristics have been investigated by employing an universal testing machine, scanning electron microscope and X-ray diffractometer. With the increase of MoSi2/Si mixing content, the quantity of the residual silicon phase was decreased and the hardness and fracture toughness of composite materials were increased. Also, as the infiltration temperature increased, a lot of fine-grained $\beta$-SiC phases, which were produced from the reaction of graphite and liquid silicon melt, were transformed to $\alpha$-SiC phases.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.642-643
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• 2006

Direct reduction and carburization process was thought one of the best methods to make nano-sized WC powder. The oxide powders were mixed with graphite powder by ball milling in the compositions of WC-5,-10wt%Co. The mixture was heated at the temperatures of $600{\sim}800^{\circ}C$ for 5 hours in Ar. The reaction time of the reduction and carburization was decreased as heating temperatures and cobalt content increased. The mean size of WC/Co composite powders was about 260 nm after the reactions. And the mean size of WC grains in WC/Co composite powders was about 38 nm after the reaction at $800^{\circ}C$ for 5 hours.