• Carbon letters
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• v.16 no.2
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• pp.132-134
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• 2015

When manufacturing bulk graphite, pores develop within the bulk during the carbonization process due to the volatile components of the fillers and the binders. As a result, the physical properties of bulk graphite are inferior to the theoretical values. Impregnants are impregnated into the pores generated in the carbonization process through pressurization and/or depressurization. The physical properties of bulk graphite that has undergone impregnation and re-carbonization processes are outstanding. In the present study, a green body was manufactured by molding with natural graphite flakes and phenolic resin at 45 MPa. Bulk graphite was manufactured by carbonizing the green body at 700 and it was subsequently impregnated with impregnants having viscosity of 25.0 cP, 10.3 cP, and 5.1 cP, and the samples were re-carbonized at $700^{\circ}C$. The above process was repeated three times. The open porosity of bulk graphite after the final process was 22.25%, 19.86%, and 18.58% in the cases of using the impregnant with viscosity of 25.0 cP, 10.3 cP, and 5.1 cP, respectively.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.57-61
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• 1999

The effect of the microstructure of gray cast iron on friction properties was investigated by using a pad-on-disk type friction tester. Cast iron samples used in this investigation were obtained from "step block" castings, which were designed to produce microstructure with different graphite flake morphologies from different cooling rate and solidification rate. Results of this work showed that the gray cast iron disks with long graphite flakes showed less fading. The rotors containing smaller amounts of ferrite showed higher friction coefficient and better fade resistance than others.an others.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.147-148
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• 2010

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1331-1335
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• 2010

A novel spherical carbon composite material, in which nanosized disordered carbons are dispersed in a soft carbon matrix, has been prepared and investigated for use as a potential anode material for lithium ion batteries. Disordered carbons were synthesized by ball milling natural graphite in air. The composite was prepared by mixing the ball-milled graphite with petroleum pitch powder, pelletizing the mixture, and pyrolyzing the pellets at $1200^{\circ}C$ in an argon flow. The ballmilled graphite consists of distorted nanocrystallites and amorphous phases. In the composite particle, nanosized flakes are uniformly distributed in a soft carbon matrix, as revealed by X-ray diffractometer (XRD) and transmission electron microscopy (TEM) experiments. The composite is compatible with a pure propylene carbonate (PC) electrolyte and shows high rate capability and excellent cycling performance. The electrochemical properties are comparable to those of hard carbon.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.6
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• pp.564-570
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• 2020

Metal hydride is suitable for safe storage of hydrogen. The hydrogen storage kinetics of the metal hydride are highly dependent on its heat transfer characteristics. This study presents a metal hydride-expended graphite composite with improved thermal conductivity and its hydrogen storage kinetics. To improve the heat transfer characteristics, a metal hydride was mixed and compacted with a high thermal conductivity additive. As the hydrogen storage material, AB5 type metal hydride La0.9Ce0.1Ni5 was used. As an additive, flakes-type expended graphite was used. With improved heat transfer characteristics, the metal hydride-expended graphite composite stores hydrogen four times faster than metal hydride powder.

• Journal of Korea Foundry Society
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• v.24 no.6
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• pp.323-330
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• 2004

This study aims to investigate on the effects of the microstructures on the wear characteristics of the different grey cast iron(GC) and spheroidal ductile cast iron(DCI). Wear test using wear tester of pin-on-disc type was carried out under the conditions of load 47.2N , velocity 0.2m/s, distance 4000m. At the GC, Wear rates depend on graphite type and oxide layer formed at wear surface. Weak rosette graphites are easily broken and formed wear debris over 30 ${\mu}m$. This wear debris occurs scuffing at wear surface. As a result of surface deformation, Narrow regions of the matrix between the graphite flakes and the contact surface lead to the failure of the necks. Wear rate for the DCI depended on hardness of matrix more than size of graphite.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.240-246
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• 1999

The effect of microstructure of gray cast iron disk was investigated by using a pad-on-disk type friction tester. Three different rotors with different microstructures were studied in this work. They showed a pearlitic matrix, a ferritic matrix, and a martensitic structure, respectively. All of them have graphite flakes in common. Drag tests at different pressure and speed conditions were carried out to study friction stability, temperature rise during drags. The rotor containing pearlitic matrix showed lower values of friction coefficient, small amount of temperature rise, and less fading. The results showed that gray cast iron disk containing pearlitic matrix has good friction characteristics.

• Korean Journal of Materials Research
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• v.14 no.9
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• pp.664-669
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• 2004

Anodic aluminum oxide (AAO) with pores of various diameter, density, and thickness values was obtained through control of the anodization parameters including voltage, temperature, pore widening time, anodization time, etc. The pore diameter was controlled by a pore widening in an etchant, and alumina templates having stepped nano-channels were fabricated by repetition of anodization and pore widening processes. Stepped carbon nanotubes (CNTs) were then grown on the stepped AAO templates by pyrolysis of acetylene without using the catalyst. High-resolution transmission electron microscopy images revealed that CNTs have a multi-wall structure made of graphite flakes of several nm sizes. The current-voltage characteristic of the sloped and linear CNTs were also examined.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.264.1-264.1
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• 2013

Graphene is a two-dimensional carbon material whose structure is one-atom-thick planar sheet of sp2-bonded carbon atoms densely packed in a honeycomb crystal lattice. It has drawn significant attention with its distinguished structural and electrical properties. Extremely high mobility and a tunable band gap make graphene potentially useful for innovative approaches to electronics. Although mechanical exfoliation of graphite and decomposition of SiC surfaces upon thermal treatment have been the main method for graphene, they have some limitations in quality and scalability of as-produced graphene films. Solutionphase and solvothermal syntheses of graphene achieved a major improvement for processing, however for device fabrication, a reproducible method such as chemical vapor deposition (CVD) growth yielding high quality films of controlled thickness is required. In this research, we synthesized hexagonal graphene flakes on Cu foils by CVD method and controlled its coverage, density and the size of graphene domains by changing reaction parameters. It is important to control these parameters of graphene growth during synthesis in order to achieve tunable properties and optimized device performance.

• Polymer(Korea)
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• v.36 no.3
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• pp.251-261
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• 2012

The nanocomposites containing graphene oxide flakes were prepared in order to improve the mechanical properties of artificial marbles based on poly(methyl methacrylate)(PMMA) matrix. Graphene oxide flakes were prepared from graphite by oxidation with Hummers method followed by exfoliation with thermal treatment. Surface of graphene oxide flakes were modified with oxyfluorination in various oxygene:fluorine compositions to improve the interfacial compatibility. The nanocomposites containing graphenes modified with oxyfluorination in the oxygen content of 50% and higher showed the significant increase in flexural strength, flexural modulus, Rockwell hardness, Barcol hardness, and Izod impact strength. The morphology of fractured surface showed the improved interfacial adhesion between PMMA matrix and the graphenes which were properly treated with oxyfluorination. The mechanical properties of nanocomposite were deteriorated by increasing the content of graphene above 0.07 phr due to the nonuniform dispersion of graphenes.