• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1183-1189
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• 2002

In order to develope the porous alumina ceramics with high strength, the pore characteristics and compressive strength were investigated in terms of relation to the conditions of spark-plasma sintering and the contents of graphite as a pore precursor. Porous alumina bodies were successfully prepared by spark-plasma sintering and burning out graphite in air. High porous bodies were fabricated by sintering at 1000${\circ}C$ for 3 min under a pressure of 30 MPa, heating rate of 80${\circ}C$/min and on-off pulse type of 12:2. For example, alumina bodies prepared by the addition of 10∼30 vol% graphite showed high porosity of 50∼57%. Also, the open porosity increased with graphite content. The relationship between pore characteristics and graphite contents could be explained by percolation model depending on cluster number and size. Porous alumina bodies prepared by the addition of 10∼30 vol% graphite showed the high compressive strength of 55∼200 MPa. This great improvement in strength was considered to be mainly due to the spark-plasma discharges and the self-heating action between particles.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.4
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• pp.395-404
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• 1994

Ni-graphite composite powders were prepared by reduction of $Ni^{++}$ from ammoniacal nickel sulfate solution on graphite core by hydrogen gas. Effect of reaction factors on the reduction rate and the properties of nickel layer were investigated by SEM, Optical Microscopy, size and chemical analysis. Induction period, a time lag between the injection of hydrogen gas and the start of the reduction, was 20~110 mins and affected by the reaction temperature and stirring speed. The reduction rate of $Ni^{++}$ was $4.5g/{\ell}/min$ at optimum condition and increased with increasing reaction temperature and stirring speed.

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.154-159
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• 2012

Structural volume change occurring on the Si-based anode battery materials during alloying/dealloying with lithium is noticed to be a major drawback responsible for a limited cycle life. Silicon monoxide has been reported to show relatively improved cycling performance compared to Si-containing materials for rechargeable lithium batteries, due to the structural buffering role of in-situ formed $Li_2O$ and lithium silicate during the reaction of silicon monoxide and lithium. Here we report improved cycling ability of interfacially stabilized Si-$SiO_2$-graphite composite anode using silane-based electrolyte additive for rechargeable lithium batteries, which includes low cost silicon dioxide for structural stabilization and graphite for enhanced conductivity.

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.123-127
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• 2010

An assembled-graphite/DSA(Dimensionally Stable Anode) was prepared using graphite powder to increase durability and energy efficiency of redox flow battery and investigated its electrochemical properties in vanadium-based electrolyte. The cyclic voltammetry (CV) was carried out in the voltage range of -0.7V and 1.6V vs. SCE at 5 mV/sec scan rate to analyze vanadium redox reaction. From the CV results, the assembled-graphite/DSA electrode showed a fast couple reaction and good reversibility in 2M $VOSO_4$ + 2.5 M $H_2SO_4$ electrolyte. Therefore, it has been expected that this electrode increases power density as well as energy density of redox flow battery.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.1
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• pp.47-58
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• 2004

Loss factors of A356, Mn-Cu alloy and aluminum matrix composites reinforced with $SiC_p$ and Ni-coated graphite particles at various contents have been investigated using clamped-free cantilever beam method. The loss factors of half-power bandwidth of the specimens were measured over a wide range of frequencies from 50 to 3300Hz. Among the specimens, Al-10%$SiC_p$-10%$C_p$ showed the highest loss factor at the mode I, while Mn-Cu alloy showed the highest loss factors at the modes II and III. Consequently, at the mode I the Al-10%$SiC_p$--10%$C_p$ showed the loss factor of 0.00093, which is 2.64 and 1.58 times higher than those of A356 and Mn-Cu alloy, respectively.

• Composites Research
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• v.33 no.5
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• pp.251-255
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• 2020

In this study, TiC ceramic particulate reinforced steel composites was fabricated using a liquid pressing infiltration process. Studies were conducted on microstructure analysis and basic physical properties such as hardness and corrosion characteristics in salt water environment for comparison with commercial nodular cast iron. As a result of comparison of corrosion characteristics in a salt water environment, both corrosion potential and corrosion current density were lower than that of ductile graphite cast iron. The lower calculated corrosion rate confirms that the TiC-Fe metal composite has superior corrosion resistance than the cast iron.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.1-6
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• 2007

Mercaptopropionic acid(mpa) has been used to make self-assembled monolayer(SAMs) on the surface of graphite electrode incorporating gold nano particles, which are subsequently modified with dopamine(dopa). Such modified electrodes haying types of Gr(Au)/mpa-dopa were employed in the electrocatalytic oxidation of NADH. The responses of such modified electrodes were studied in terms of electron transfer kinetics and reaction procedure in the reaction. The reaction of the surface immobilized dopa with NADH was studied using the rotating disk electrode technique and a value of $5.06{\times}10^5M^{-1}s^{-1}$ was obtained for the second-order rate constant in 0.1 M phosphate buffer(pH=7.0), which was a $EC_{cat}$ and kinetic controlled procedure. But, the modified electrodes were diffusion controlled reaction having $4.64{\times}10^{-4}cm^2s^{-1}$ of the coefficient within $10^{-3}s$ after starting the reaction.

• Polymer(Korea)
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• v.37 no.2
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• pp.162-166
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• 2013

Graphene-coated polymer particles have attracted research interests due to their emerging applications derived from their controlled structure and morphology. To control the properties of graphene oxide (GO)-polystyrene (PS) composite particles, the adsorption time and instantaneous adsorption conditions were investigated by varying their mixing method. Polystyrene particles prepared by emulsion polymerization were modified to have positive surface charge by adsorption of polyethylene imine (PEI) on the surface of PS particles. GO prepared by the chemical exfoliation method had negative surface charge from the oxygenated groups. The adsorption of the negatively charged GOs onto the positively charged PS particles was successfully completed, and it was found that a longer adsorption time and a greater difference in the instantaneous relative concentration led PS-GO particles to have more homogeneously coated surfaces without aggregation.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.554-557
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• 2005

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 for 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. To achieve desired electric properties, specimens made with different mixing ratio, processing pressure and temperature were tested. To increase mechanical strength, one or two layer of woven carbon fabric were added to the original graphite and resin composite. Thus, the composite material is consisted of the three phases: graphite particles, epoxy resin, and carbon fabric. By increasing mixing ratio, fabricated pressure and process temperature, electric conductivity was improved. The results of tensile test showed that the tensile strength of two-phase graphite composite was about 5MPa, and that of three-phase composite was increased to 54MPa.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.105-108
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• 2006

The fuel cell is one of the promising environment-friendly energy sources for the next generation. The fuel cell provides good energy efficiency above 40% without pollution or noise. Different fuel cell types are usually distinguished by the kind of electrolyte. Among these, the proton exchange membrane fuel cell (PEMFC) has advantages of high power density. low operating temperature, relatively quick start-up, and rapid response to varying loads. The bipolar plate is a major component of the PEM fuel cell stack, and it takes a large portion of stack volume, weight and cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding and by machining. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. Flow channels were fabricated by compression molding with design of experiments (DOE) to evaluate moldability. The cost for compression molding of graphite-composite bipolar plate was compared with machining cost to make the same bipolar plate.