Euigyung Jeong

Agency for Defense Development, Sŏul, Seoul, South Korea

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Publications (24)50.65 Total impact

  • Polymer Korea 05/2015; 39(3):426-432. DOI:10.7317/pk.2015.39.3.426 · 0.43 Impact Factor
  • Min-Jung Jung, Euigyung Jeong, Young-Seak Lee
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    ABSTRACT: The surfaces of multi-walled carbon nanotubes (MWCNTs) were thermally fluorinated at various temperatures to enhance the electrochemical properties of the MWCNTs for use as electric double-layer capacitor (EDLC) electrodes. The fluorine functional groups were added to the surfaces of the MWCNTs via thermal fluorination. The thermal fluorination exposed the Fe catalyst on MWCNTs, and the specific surface area increased due to etching during the fluorination. The specific capacitances of the thermally fluorinated at 100 °C, MWCNT based electrode increased from 57 to 94 F/g at current densities of 0.2 A/g, respectively. This enhancement in capacitance can be attributed to increased polarization of the thermally fluorinated MWCNT surface, which increased the affinity between the electrode surface and the electrolyte ions.
    Applied Surface Science 04/2015; 347. DOI:10.1016/j.apsusc.2015.04.038 · 2.54 Impact Factor
  • Polymer Korea 01/2015; 39(1):114-121. DOI:10.7317/pk.2015.39.1.114 · 0.43 Impact Factor
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    ABSTRACT: The pitch-based high crystallinity cokes are investigated by evaluating its potential as electrode materials for electric double layer capacitors (EDLCs). After activation process, the high crystallinity cokes-based activated carbon (hc-AC) demonstrates great potential for use as an electrode material for EDLCs. The specific capacitance of hc-AC with the carbon to KOH ratio of 1:3 is 276 F g−1, even with a low specific surface area of 983 m2 g−1. These results are comparable to that of the most commonly used material for EDLCs, MSP 20 (256 F g−1), which has a high specific surface area of 1807 m2 g−1.
    Journal of Industrial and Engineering Chemistry 07/2014; 23. DOI:10.1016/j.jiec.2014.07.038 · 2.06 Impact Factor
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    ABSTRACT: To investigate the relationship between textural properties and electrochemical properties, activated carbon nanofibers were manufactured using an electrospinning process followed by chemical activation using KOH or NaOH. The specific surface area of the KOH-activated carbon nanofibers was higher than that of NaOH-activated carbon nanofibers; however, the total pore volume and mesopore volume of the NaOH-activated carbon nanofibers were greater than those of the KOH-activated carbon nanofibers when the same number of moles of KOH and NaOH were used. The specific capacitances increased as the specific surface area and pore volume of the activated carbon nanofibers were increased. However, the specific capacitance obtained at a high scan rate (50 mV/s) and the retained capacitance of the activated carbon nanofibers increased with increasing total pore and mesopore volume, especially for mesopores with diameters of 2–4 nm.
    Journal of Industrial and Engineering Chemistry 07/2013; 19(4):1315–1319. DOI:10.1016/j.jiec.2012.12.034 · 2.06 Impact Factor
  • Euigyung Jeong, Min-Jung Jung, Young-Seak Lee
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    ABSTRACT: In this study, we investigated the role of fluorination in improving the electrochemical properties of activated carbon nanofiber (ACNF) electrodes. The ACNFs were prepared with various textural properties and then fluorinated. The electrochemical properties of the resulting ACNFs were subsequently evaluated to investigate the effect of the fluorination of the prepared ACNFs with various textural properties on the electrochemical properties. The specific capacitances of the ACNF electrodes increased by 15.8–47.3% after fluorination, although the specific surface area and the total pore volume decreased significantly; these results suggest that the introduction of CF functional groups onto the ACNF surface was more important than the induction of changes in the textural properties of the ACNF samples with respect to improving the electrochemical properties of the ACNF electrodes. The retained capacitances of the ACNF electrodes also increased 2–12% after fluorination, although the etching effect of the fluorination significantly collapsed the mesopores; these results suggest that the CF functional groups were electrochemically active even at a high scan rate.
    Journal of Fluorine Chemistry 06/2013; 150:98–103. DOI:10.1016/j.jfluchem.2013.02.017 · 1.95 Impact Factor
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    ABSTRACT: This study investigated the potential of direct fluorination as a multifunctional surface modification method for an aramid fabric. The aramid fabric was fluorinated at temperatures of 30, 90, and 150 °C. As the fluorination temperature increased, the fluorinated aramid fabric became more hydrophobic and oleophobic, with a water contact angle of 129.3° and a diiodomethane contact angle of 108.6° when the fluorination temperature was 150 °C. Thus, the fluorinated fabric could be defined as an omniphobic surface. Both the phenol resin wettability and the impregnation of the fluorinated aramid fabric improved as the fluorination temperature increased, suggesting better interfacial adhesion between the fabric and the polymer matrix. Direct fluorination of an aramid fabric can be an efficient multifunctional surface modification method to achieve omniphobicity in the aramid fabric for the protection, self-cleaning, and improved interfacial adhesion between the fabric and resin for fiber-reinforced polymer composites.
    Journal of Fluorine Chemistry 09/2012; 141:69–75. DOI:10.1016/j.jfluchem.2012.06.010 · 1.95 Impact Factor
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    ABSTRACT: The surface of phenol-based activated carbon (AC) was seriatim amino-fluorinated with solution of ammonium hydroxide and hydrofluoric acid in varying ratio to fabricate electrode materials for use in an electric double-layer capacitor (EDLC). The specific capacitance of the amino-fluorinated AC-based EDLC was measured in a 1 M H(2)SO(4) electrolyte, in which it was observed that the specific capacitances increased from 215 to 389 Fg(-1) and 119 and 250 Fg(-1) with the current densities of 0.1 and 1.0 Ag(-1), respectively, in comparison with those of an untreated AC-based EDLC when the amino-fluorination was optimized via seriatim mixed solution of 7.43 mol L(-1) ammonium hydroxide and 2.06 mol L(-1) hydrofluoric acid. This enhancement of capacitance was attributed to the synergistic effects of an increased electrochemical activity due to the formation of surface N- and F-functional groups and increased, specific surface area, and mesopore volumes, all of which resulted from the amino-fluorination of the electrode material.
    Journal of Colloid and Interface Science 05/2012; 381(1):152-7. DOI:10.1016/j.jcis.2012.05.031 · 3.55 Impact Factor
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    ABSTRACT: To improve the electrochemical performance of an activated carbon (AC)-based electric double-layer capacitor (EDLC), the AC surface, which is used as an electrode, was modified using physicochemical base tuning that uses different concentrations of ammonium hydroxide. The effect of the treatment on the surface and electrochemical properties of the AC electrodes was investigated. The specific capacitance of a 13 vol%-solution-treated sample was increased to 385 F/g at a scan rate of 5 mV/s, which was 17% higher than the value of 328 F/g obtained for the untreated samples. This increase can be attributed to an increase in the mesopore volume ratio due to the etching effect of the reaction between the carbon surfaces and ammonium hydroxide. Moreover, nitrogen functional groups, which were introduced by the treatment, also improved the electrochemical properties of the resulting AC-based electrode. Therefore, a simultaneous etching and nitrogen-introducing method with ammonium hydroxide can easily introduce nitrogen functional groups on the surface of an AC electrode. This method is very effective for preparing AC for use in an EDLC with improved electrochemical properties.
    Journal of Industrial and Engineering Chemistry 03/2012; 18(2). DOI:10.1016/j.jiec.2011.11.055 · 2.06 Impact Factor
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    ABSTRACT: To improve the electrical performance of activated carbon (AC)-based electric double-layer capacitors (EDLCs), the surface of AC was modified with gas phase ammonia treatment at 1073 K with different treatment times to carry out simultaneous etching and N-doping. The effects of the treatment on AC surfaces and their electrochemical properties were investigated. The specific capacitances of samples treated for 22 min were increased to 426 F/g at scan rates of 10 mV/s, which corresponded to a 76.8% increase as compared with 241 F/g of samples measured as received from the manufacturer. The increase is attributed to an increase in the specific surface area and the total pore, micro- and mesopore volumes due to the etching effect of the high-temperature ammonia gas reaction. Moreover, N-functional groups, which were introduced by the treatment, also aided to improve the electrochemical properties of the resulting AC-based electrode. Therefore, the simultaneous etching and N-doping method with ammonia gas at high temperature can easily introduce nitrogen functional groups on the AC surface. In addition, the reaction of nitrogen gas with AC can affect its specific surface area and surface pore structure, which is very effective in preparing AC for EDLCs with improved electrochemical properties.
    Journal of Industrial and Engineering Chemistry 01/2012; 18(1):116–122. DOI:10.1016/j.jiec.2011.11.074 · 2.06 Impact Factor
  • Jinhoon Kim, Euigyung Jeong, Young-Seak Lee
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    ABSTRACT: This study reports the application of illite as a clay filler and direct fluorination as an organophilic modification for clays. Illite was also modified using conventional methods, with reagents such as 3-aminopropyltrimethoxysilane and hexadecyl-trimethoxysilane for comparison of the resultant illite/polypropylene (PP) composites with the fluorinated illite/PP composites. The thermal properties, flame retardancy, and mechanical properties of the resultant composites were also investigated. Fluorination of illite resulted in exfoliation and more thermally stable organophilic modification compared with the conventional silane treatment. When comparing two different silane-treated illite/PP composites with fluorinated illite/PP composites, fluorinated illite had better thermal stability and exfoliation after modification and more improved dispersion in PP matrix. This resulted in improved thermal stability, flame retardancy, and mechanical properties compared with the silane-treated illite/PP composites. The fluorinated illite/PP composite exhibited a 28% increase in thermal stability and a 50% increase in flame retardancy compared with neat PP. Fluorination of illite yielded at least 50% further improvement in the thermal stability and flame retardancy of the resulting illite/PP composites compared with the conventional silane treatments.
    Journal of Materials Science 01/2012; 47(2):1046-1053. DOI:10.1007/s10853-011-5893-x · 2.37 Impact Factor
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    ABSTRACT: The surface of phenol-based activated carbon (AC) was fluorinated at room temperature with different F2:N2 gas mixtures for use as an electrode material in an electric double-layer capacitor (EDLC). The effect of surface fluorination on EDLC electrochemical performance was investigated. The specific capacitance of the fluorinated AC-based EDLC was measured in a 1 M H2SO4 electrolyte, in which it was observed that the specific capacitances increased from 375 and 145 F g−1 to 491 and 212 F g−1 with the scan rates of 2 and 50 mV s−1, respectively, in comparison to those of an unfluorinated AC-based EDLC when the fluorination process was optimized via 0.2 bar partial F2 gas pressure. This enhancement in capacitance can be attributed to the synergistic effect of increased polarization on the AC surface, specific surface area, and micro and mesopore volumes, all of which were induced by the fluorination process. The observed increase in polarization was derived from a highly electronegative fluorine functional group that emerged due to the fluorination process. The increased surface area and pore volume of the AC was derived from the physical function of the fluorine functional group.
    Journal of Fluorine Chemistry 12/2011; 132(12):1127–1133. DOI:10.1016/j.jfluchem.2011.06.046 · 1.95 Impact Factor
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    ABSTRACT: The surface of a phenol-based activated carbons (ACs) used as an electrode in an electric double-layer capacitor (EDLC) was oxyfluorinated at room temperature with different F2:O2 gas mixtures, and the effects of these surface modifications on EDLC electrical performance were investigated. The specific capacitance of the oxyfluorinated AC-based EDLC was measured in a 1 M H2SO4 electrolyte, in which it was observed that the specific capacitances increased from 375 and 145 F g−1 to 391 and 189 F g−1 with the scan rates of 5 and 50 mV s−1, respectively, over compared to those of an untreated AC-based EDLC when the oxyfluorination ratio was at the optimal F2:O2 = 5:5. This was attributed to the synergistic effect of surface chemical compositions and textural properties of the resulting oxyfluorinated AC, which had the highest micropore volume, an optimal mesopore volume, and electrochemically active surface functional groups, such as C–F and quinone CO.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 09/2011; 389(s 1–3):274–280. DOI:10.1016/j.colsurfa.2011.08.013 · 2.35 Impact Factor
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    ABSTRACT: A high-performance NO gas sensor was prepared by inducing thermal fluorination of carbon nanotube semiconductors. Thermal fluorination of multi-walled carbon nanotubes (MWCNTs) was carried out at various temperatures (100 ∼ 1000 °C) to investigate the effects of the reaction temperature. The mechanism of high-performance NO gas sensor electrode was shown to depend on the fluorination temperature in a way that can be divided into three regions, separated at 400 and 1000 °C. In the first temperature region, the induction of fluorine functional groups onto MWCNTs showed the opposite trend in electrical resistance change comparing with traditional p-type MWCNTs. In the second temperature region, the induced fluorine functional groups were attenuated by generated fluorinated carbon gases resulting in the decomposition of MWCNTs and the recovery of traditional p-type gas sensor behavior. In the highest temperature region above 1000 °C, reoriented carbon structure was observed, showing bent nanotubes produced from destruction by fluorination and subsequent reorientation due to the high temperature. The gas sensing responsiveness was significantly improved by the thermal fluorination, which causes electrophilic attraction, creates adsorption sites for target NO gases and improve hydrophobicity for gas sensing stability in humid condition. In conclusion, a high-performance gas sensor was obtained by thermal-fluorination of MWCNTs.
    Carbon 06/2011; 49(7):2235-2244. DOI:10.1016/j.carbon.2011.01.054 · 6.16 Impact Factor
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    ABSTRACT: Oxy-fluorination of carbon preforms with various F2:O2 gas mixtures were examined to improve the mechanical and thermal properties of carbon fiber-reinforced carbon composites (C/C composites). The oxy-fluorination of the preforms introduced functional groups onto the preform surface, which improved their thermal properties. Oxy-fluorination also improved the interfacial adhesion of the C/C composites, resulting in increased flexural strength and anti-oxidation. Two synergistic effects of oxy-fluorination on the carbon preform are suggested. One optimizes interfacial adhesion by forming hard chemical bonds and soft electrophilic bonds between the surface functional groups of the oxy-fluorinated carbon preforms and the functional groups of the carbon precursors. The other improves anti-oxidation of the C/C composites by improving the thermal properties of the carbon preform itself and interfacial adhesion which resulted in reducing pores, voids, and interfacial cracks.
    Journal of Fluorine Chemistry 04/2011; 132(4):291-297. DOI:10.1016/j.jfluchem.2011.02.008 · 1.95 Impact Factor
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    ABSTRACT: To investigate potential use of a layered silicate, illite, for carbon fiber-reinforced (C/C) composites, the C/C composites were prepared at different carbonization temperatures, specifically 1000°C and 1650°C using illite. The physical and chemical changes in the prepared C/C composites that were induced by the addition of illite and anti-oxidation and mechanical properties of the composites were investigated. A carbothermal reaction occurred due to the addition of illite when the composite was prepared at 1650°C, which resulted in the formation of SiC from the illite and carbon. The physical structures of the composites changed due to the increased interfacial adhesion between the reinforcing carbon fibers and the carbon matrix, which resulted increased bulk densities, and decreased porosities. The carbothermal reaction and physical structural changes that were induced by the addition of illite synergistically improved the anti-oxidation properties of the prepared composites, which were observed as a delay in oxidation. In addition, illite filler also improved flexural strength of the composite, due to the increased interfacial adhesion induced by illite addition. Therefore, the application of the layered silicate, illite, for C/C composites can be quite promising.
    Journal of Industrial and Engineering Chemistry 03/2011; 17(2):191-197. DOI:10.1016/j.jiec.2011.02.032 · 2.06 Impact Factor
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    ABSTRACT: This study introduces amino-fluorination, a novel chemical modification method for activated carbon (AC), and investigates the surface and electrochemical properties of the resulting AC. The procedure was modified by controlling the surface reaction with concentrated ammonium hydroxide and diluted hydrofluoric acid or diluted ammonium hydroxide and concentrated hydrofluoric acid. Amino-fluorination of AC with concentrated ammonium hydroxide and diluted hydrofluoric acid significantly increased the specific surface area, total pore volume, mesopore volume, and number of N- and F-containing surface functional groups and decreased the number of O-containing surface functional groups. These changes resulted in improving the specific capacity to 417F/g at a scan rate of 10mVs−1 from the specific capacity of raw AC-based EDLCs (241F/g). On the other hand, amino-fluorination of AC with diluted ammonium hydroxide and concentrated hydrofluoric acid increased the specific surface area, total pore volume, mesopore volume, and number of N-, O-, and F-containing surface functional groups. These changes resulted in the highest specific capacitance for the prepared AC-based EDLCs (485F/g), with a 101% increase compared to the raw-AC-based EDLCs. Therefore, the amino-fluorination of AC is a simple and efficient way to enhance the performance of AC-based EDLCs.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 03/2011; 377(1):243-250. DOI:10.1016/j.colsurfa.2010.12.035 · 2.35 Impact Factor
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    ABSTRACT: In this study, the effects of physicochemical treatments of illite on thermo-mechanical properties and thermal stability of the hybrid illite/epoxy composites were investigated. Illite was chemically modified with octadecylamine (ODA), to become more organophilic and also physically modified by wet ball-milling process, so that the illite dispersion in the epoxy matrix and interfacial adhesion between illite and epoxy resin could be improved. Then, as-received illite and physically and/or chemically modified illites were mixed with epoxy separately to produce hybrid illite/epoxy composites and their thermo-mechanical properties and thermal stability were investigated. Chemical modification was confirmed with FTIR and the aforementioned properties of illite/epoxy composites were characterized with SEM, DMA, and TGA. IR results show that ODA modification of illite was successful and thermo-mechanical properties were enhanced with illite introduction to the epoxy resin, especially when physically and chemically modified illite was added, showing about 100% increase in storage and loss modulus, compared to the pure epoxy. However, thermal stability was not enhanced by forming the illite/epoxy composites, because the composites prepared in this study were intercalated and flocculated illite/epoxy microcomposites.
    Journal of Industrial and Engineering Chemistry 01/2011; 17(1):77-82. DOI:10.1016/j.jiec.2010.10.012 · 2.06 Impact Factor
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    ABSTRACT: In this study, a unique two-step process, i.e., an oxyfluorination-assisted graft polymerization (OAGP), was used to modify the surface properties of low-density polyethylene (LDPE) films. Based on the results of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method, which was performed to estimate the amount of hydroperoxides generated by oxyfluorination, oxyfluorination conditions that maximize the amount of hydroperoxide groups were selected. Hydroperoxides were generated by oxyfluorination to provide active sites for the OAGP of the different monomers. Depending on the type of monomers used, two different graft polymerization behaviors were observed. Hydrophilic methacrylic acid (MA) monomers were graft polymerized onto the oxyfluorinated LDPE (OFPE) surface in a perpendicular direction, forming a spike-shaped morphology. On the other hand, hydrophobic styrene (ST) monomers were graft polymerized parallel to the OFPE surface, forming a valley-shaped morphology. By changing the type of vinyl monomers, two different surfaces could be prepared using the hydroperoxides generated by oxyfluorination. After OAGP with MA monomers, a hydrophilic surface following the Wenzel model was obtained, whereas after OAGP with ST monomers, a hydrophobic surface following the Cassie–Baxter model was obtained. Therefore, the OAGP process may be an efficient method for preparing two different surfaces by changing the monomer used.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 01/2011; 373(1-3):36-41. DOI:10.1016/j.colsurfa.2010.10.008 · 2.35 Impact Factor
  • Source
    Young-Seak Lee, Euigyung Jeong, Ji Sun Im
    Ferroelectrics, 12/2010; , ISBN: 978-953-307-439-9

Publication Stats

108 Citations
50.65 Total Impact Points

Institutions

  • 2014–2015
    • Agency for Defense Development
      Sŏul, Seoul, South Korea
  • 2010–2013
    • Chungnam National University
      • • Department of Fine Chemical Engineering and Applied Chemistry
      • • Department of Chemical Engineering
      Sŏngnam, Gyeonggi Province, South Korea