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Seo M.-K.,Jeonju Institute of Machinery and Carbon Composites | Kuk Y.-S.,Jeonju Institute of Machinery and Carbon Composites | Kuk Y.-S.,Chonbuk National University | Park S.-J.,Inha University
Journal of Nanoscience and Nanotechnology | Year: 2013

In this work, electrochemical properties of a bilayer electrode system prepared from an electrically conducting polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), PEDOT-PSS coated carbon nanofibers (CNFs), have been investigated. The CNFs were used as supports for the deposition of PEDOT-PSS by a dip-coating technique to yield a bilayer electrode system. Electrodes prepared by such a method were used in supercapacitors operating in acidic (1 M H2SO4) electrolytes. The capacitance values were estimated by voltammetry and galvanostatic techniques with a three-electrode cell configuration. Due to the CNF's graphitic structure and the presence of exterior walls with numerous edges, a high specific surface area and easily accessible electrode/electrolyte interface were obtained, thus yielding good capacitance in the bilayer active materials. The capacitance for PEDOT-PSS coated CNF bilayer electrodes ranged from 80 to 180 F/g and the fabricated materials showed good cycling performance with high stability in aqueous electrolytes. This was probably due to enhanced access to the CNFs, leading to the generation of a double layer and, ultimately, higher values of the capacitance. Copyright © 2013 American Scientific Publishers. Source

Yim Y.-J.,Chonbuk National University | Seo M.-K.,Jeonju Institute of Machinery and Carbon Composites | Kim H.-Y.,Chonbuk National University | Park S.-J.,Inha University
Polymer (Korea) | Year: 2012

In this work, the effect of multi-walled carbon nanotube (MWCNT) on electromagnetic interference shielding effectiveness (EMI SE) and mechanical properties of MWCNT-reinforced polypropylene (PP) nanocomposites were investigated with varying MWCNT content from 1 to 10 wt%. Electric resistance was tested using a 4-point-probe electric resistivity tester. The EMI SE of the nanocomposites was evaluated by means of the reflection and adsorption methods. The mechanical properties of the nanocomposites were studied through the critical stress intensity factor (K IC) measurement. The morphologies were observed by scanning electron microscopy (SEM). From the results, it was found that the EMI SE was enhanced with increasing MWCNT content, which played a key factor to determine the EMI SE. The K IC value was increased with increasing MWCNT content, whereas the value decreased above 5 wt% MWCNT content. This was probably considered that the MWCNT entangled with each other in PP due to an excess of MWCNT. Source

Kim B.-J.,Jeonju Institute of Machinery and Carbon Composites | Choi W.-K.,Jeonju Institute of Machinery and Carbon Composites | Um M.-K.,Korea Institute of Materials Science | Park S.-J.,Inha University
Surface and Coatings Technology | Year: 2011

In this work, nickel/carbon hybrid fibers were prepared by the electrolytic plating on carbon fibers in order to improve electric conductivity of the carbon fibers; the effects of nickel content and coating thickness on the electric conductivity of the fibers were studied. The structural properties and surface morphologies of the hybrid fibers were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The electric conductivity of the fibers was measured using a 4-point probe method. As for experimental results, it was observed that the electric conductivity of the nickel/carbon hybrid fibers was dramatically increased in the presence of metallic nickel particles, with the best result in the condition of over 0.75 μm of the thickness due to the minimization of the inner pores. © 2010 Elsevier B.V. Source

Kim B.-J.,Jeonju Institute of Machinery and Carbon Composites | Byun J.-H.,Korea Institute of Machinery and Materials | Park S.-J.,Inha University
Bulletin of the Korean Chemical Society | Year: 2010

In this work, mechanical and electrical properties of graphenes (GP)/carbon nanotubes (CNTs) co-reinforced high density polyethylene (HDPE) matrix composites were studied. The microstructure, morphologies, and electric properties of the composites were evaluated by XRD, TEM, and 4-probe methods, respectively. It was found that the electric resistivity of 0.5 wt %-GP/HDPE was immeasurable, and 2.0 wt %-CNTs/HDPE showed high resistivity (6.02 × 104 Ω·cm). Meanwhile, GP (0.5 wt %)/CNTs (2.0 wt %)/HDPE showed excellent low resistivity (3.1 × 102 Ω·cm). This result indicates that the co-reinforcement systems can dramatically decrease electric resistivity of the carbon/polymer nanocomposites. Source

Kim B.-J.,Jeonju Institute of Machinery and Carbon Composites | Park S.-J.,Inha University
International Journal of Hydrogen Energy | Year: 2011

Nickel/graphite hybrid materials were prepared by mixed acid treatment of graphite flakes, following metal nanoparticle deposition. The textural properties were studied by BET surface area measurement and t-plot methods with N2/77 K adsorption isotherms. The hydrogen storage characteristics of the nickel/graphite at 298 K and 10 MPa were studied using a pressure-composition-temperature apparatus. The pore structure of the materials was studied as a function of processing conditions. In the optimum material, the hydrogen storage capacity was as high as 4.48 wt.%. The total amount of storage was not proportional to the specific surface area or metal content of the adsorbate. A dipole-induced model on nickel/carbon surfaces is proposed for the hydrogen storage mechanism. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. Source

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