• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권8호
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• pp.580-586
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• 1999

Aging characteristics of 13 years service-aged distribution cable terminations which dismounted from 3 regions were investigated by material characterization and electrical test. All dismounted terminations have propagating micro-cracks on the surface of weathershed and chalking fillers from bulk. Elemental analysis of these terminations showed that the carbon was decreased and the oxygen was increased on the surface of weathershed due to a little oxidation reaction. Contact angle of terminations was abnormally increased with time. In the analysis of anti-oxidation ability and chemical structure, there were no differences between new and dismounted terminations. All terminations showed satisfactory results in electrical test. Therefore, itcan be considered that aging is only propagating on the surface of dismounted terminations. Also, it was confirmed that environmental factors such as UV, pollution and salt have an effect on the aging through the observation of polymer composition change.

• 대한금속재료학회지
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• 제50권9호
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• pp.637-643
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• 2012

Recently, because of safety and environmental concerns, there has been a tendency to introduce solid self-lubricating composites for bearing materials. In this paper, we developed Fe-Cr-C-Mn-Cu cast composite alloys as a self-lubricating composite and investigated the effect of carbon on the formation of protective tribofilms during sliding. The wear resistance of these materials was mainly affected by carbon concentrations due to the fact that in particular wear passed from delamination to tribo-oxidation, reducing the wear rate. The improved wear resistance likely resulted from protective tribofilms that formed on the surface during sliding.

• 대한방사성의약품학회지
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• 제4권2호
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• pp.115-120
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• 2018

In recent years, many researchers have attempted to make use of 2D nanoparticles as molecular imaging probes since extensive investigations proved that 2D nanoparticles in the body tends to accumulate certain lesions by enhanced permeability and retention (EPR) effect. For example, graphene and carbon nitride which have high surface area and modifiable properties showed good biocompatibility and targetability when it used as imaging probes. However, poor dispersibility in physiological mediums and its uncontrolled size limited its usage in bio-application. Therefore, oxidation process and mechanical exfoliation have been developed for overcoming these problems. In this paper, we highlight the several major methods to synthesize biocompatible 2D nanomaterials like graphene and carbon nitride especially for molecular imaging study including positron emission tomography (PET).

• Journal of Electrochemical Science and Technology
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• 제8권1호
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• pp.43-52
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• 2017

In this paper, for the first time, the electroanalytical study of Triethylenediamine, TEDA was done on a typically graphene modified carbon paste electrode (Gr/CPE) in pH=10.5 of phosphate buffer solutions (PBS). The surface morphology of the bare and modified electrodes was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electro-oxidation of TEDA was investigated at the surface of modified electrode. The results revealed that the oxidation peak current of TEDA at the surface of Gr/CPE is 2.70 times than that shown at bare-CPE. A linear calibration plot was observed in the range of 1.0 to 202.0 ppm. In this way, the detection limit was found to be 0.18 ppm. The method was then successfully applied to determination of TEDA in aqueous samples obtained from two kinds of activated carbon from the masks of war. On the other hand, density functional theory (DFT) method at B3LYP/6-311++G** level of theory and a conductor-like Polarizable Continuum Model (CPCM) was used to calculate the $pK_a$ values of TEDA. The energies of lowest unoccupied molecular orbital ($E_{LUMO}$) and highest occupied molecular orbital ($E_{HOMO}$), gap energy (${\Delta}E$) and some thermodynamic parameters such as Gibbs free energy of TEDA and its conjugate acid ($HT^+$) were calculated. The results of calculated $pK_a$ were found to be in good agreement with the experimental values.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2529-2534
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• 2012

Poly(3,4-ethylenedioxythiophene) coated Manganese Dioxide (PEDOT/$MnO_2$) composite electrode was fabricated by simply immersing the $MnO_2$ electrode in an acidic aqueous solution containing 3,4-ethylenedioxythiophene (EDOT) monomers. Analysis of open-circuit potential of the $MnO_2$ electrode in the solution indicates the reduction of outer surface of $MnO_2$ to dissolved $Mn^{2+}$ ions and simultaneously oxidation of EDOT monomer to PEDOT on the $MnO_2$ surface to form a PEDOT shell via a galvanic displacement reaction. Analysis of cyclic voltammograms and specific capacitance of the PEDOT/$MnO_2$, conductive carbon added $MnO_2$ and conductive carbon added PEDOT/$MnO_2$ electrodes suggests that the conductive carbon acted mainly to provide a continuous conducting path in the electrode to improve the rate capability and the PEDOT layer on $MnO_2$ acts to increase the active reaction site of $MnO_2$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권4호
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• pp.154-160
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• 2005

We have investigated thermal properties showed by changing the content of carbon black which is the component parts of semiconductive shield in underground power transmission cable. Specimens were made of sheet with the nine of those for measurement. Density of specimens was measured by density meter, and then stress-strain of specimens was measured by TENSOMETER 2000. A speed of measurement was 200[mm/min], ranges of stress and strain were 400(Kgf/$cm^2$) and 600[$\%$]. In addition, tests of stress-strain were progressed by aging specimens at air oven. Finally surface profile was shown in order to looking for protrusion of specimens by using smoothness tester. Density was highly measured according to increasing the content of carbon black from this experimental result, and stress was decreased, while strain was increased according to increasing the content of carbon black. And stress-strain were decreased some after aging because of oxidation reaction of chemical defect. Lastly surface of specimens smoothed generally.

• 한국대기환경학회지
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• 제31권6호
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• pp.538-547
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• 2015

Test activated carbon fiber (ACF) was prepared from Polyacrylonirile (PAN) through oxidation and chemical activation. Immersion of ACF precursors in the aqueous KOH solution enhanced the surface structure, as examined by BET pore analysis. Specific surface area increased greatly from less than $70m^2/g$ to $1226m^2/g$ with 4 M KOH, and total pore volume also rose up to $0.483cm^3/g$. In particular, it was found that micropores favorable for $CO_2$ molecule capture occupied more than 95%. Maximum $CO_2$ adsorption capacity was 3.59 mmol/g at 298 K. Low depth of pores in the present ACF may facilitate the molecules' desorption for its regeneration.

• Carbon letters
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• 제2권3_4호
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• pp.159-164
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• 2001

In this study, the effects of carbon black (CB) content and anodic oxidation treatment with $AgNO_3$ on positive temperature coefficient (PTC) behavior of CB/HDPE nanocomposites were investigated. Also, the addition of elastomer as a toughing agent was studied. The 20~50 wt% of CB, 0~5 wtt% of elastomer, and 1 wt% of $AgNO_3$-filled HDPE nanocomposites were prepared using the internal mixer in 60 rpm at $160{\circ}C$ and the compression-molded at $180{\circ}C$ for 10 min. As a result, the room temperature resistivity and PTC intensity of the composites were dependent, to a large extent, on the content of CB, addition of elastomer, and surface chemical properties that were controlled in the relative arrangements of the carbon black aggregates in a polymeric matrix. Moreover, the composites with relatively low room temperature resistivity and suitable PTC intensity could be achieved by treatment of $AgNO_3$. Consequently, it was noted that PTC effect was due to the deagglomeration or the breakage of the conductive networks caused by thermal expansion or crystalline melting of the polymeric matrix.

• Journal of Electrochemical Science and Technology
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• 제6권4호
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• pp.139-145
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• 2015

Capacitive deionization (CDI) process is a novel approach for desalination of an aqueous salt solution. In the present study, an activated carbon cloth (ACC) is proposed as effective electrode material. Initially the carbon cloth was activated in 1 M and 8 M HNO₃ for 9 hours at room temperature. The untreated and chemically activated carbon cloth (ACC) electrode materials were subjected to BET surface area measurements in order to get information about their specific surface area, average pore size, total pore volume and micropore area. The above materials were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) also. The electrochemical studies for the electrodes were done using cyclic voltammetry (CV) in 0.1 M Na₂SO₄ medium. From the studies, it was found that resistivity of the activated carbon cloth electrodes (treated in 1 M and 8 M HNO₃) was decreased significantly by the chemical oxidation in nitric acid at room temperature and its capacitance was found to be 90 F/g (1 M HNO₃) and 154 F/g (8 M HNO₃) respectively in 0.1 M Na₂SO₄ solution. The capacitive deionization behavior of a single cell CDI with activated carbon cloth electrodes was also studied and reported in this work.

• 한국정밀공학회지
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• 제14권4호
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• pp.30-37
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• 1997

This thesis is concerned with the study on the characteristics of the tool failure occuring at the beginning of cutting in finish machining of hardened steels such as carbon tool steel and alloy tool steel by a ceramic tool (Al$_{2}$O$_{3}$+TiC) with nose radius. In the machining of hardened carbon steel STC3, the wear mechanism on the flank face of the ceramic tool is abrasion wear. The mode of tool failure is developed into catastropic fracture with flaking. It is thought that the fracture caused by FeO and TiO$_{2}$ results from the oxidation of Fe in the workpice and TiC in the ceramic tool and the deposit of Fe formed on the surface of the ceramic tool. In the machining of hardened alloy steel STD11, the wear mechanism on the flank face of the ceramic tool is that abrasion and adhesion wear exist simultaneously. The mode of tool failure at the beginning of cutting features is DOC notch wear. It is thought that the DOC notch wear caused by FeO and TiO$_{2}$results from the oxidation of Fe and TiC in the workpiece and ceramic tool, respectively.