• Title, Summary, Keyword: Carbon

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Growth of nickel-catalyzed carbon nanofibers using MPCVD method and their electrical properties

  • Kim, Sung-Hoon
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.14 no.1
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    • pp.1-5
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    • 2004
  • Carbon nanofilaments were formed on silicon substrate via microwave plasma-enhanced chemical vapor deposition method. The structure of carbon nanofilaments was identified as the carbon nanofibers. The extent of carbon nanofibers growth and the diameters of carbon nanofibers increased with increasing the total pressure. The growth direction of carbon nanofibers was horizontal to the substrate. Laterally grown carbon nanofibers showed the semiconductor electrical characteristics.

Carbon Materials as Catalysts

  • Lim, Seong-Yop;Jung, Doo-Hwan;Yoon, Seong-Ho;Mochida, Isao
    • Carbon letters
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    • v.9 no.1
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    • pp.47-60
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    • 2008
  • Understanding the exact structure and surface characteristics of carbon materials is very important for design, synthesis, and utilization of the best carbon form with particular functions and high performance for practical applications such as selective adsorption adsorbents, energy storage materials, catalysts or catalyst supports, etc. This review paper focuses on carbon surface properties and the interaction between gaseous or liquid substances and carbon surface. Catalytic functions of carbon materials are reviewed including recent progress in synthesis and applications of nano-carbons.

Studies on ILSS and Acoustic Emission Properties of Carbon-Carbon Composites

  • Park, Soo-Jin
    • Carbon letters
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    • v.1 no.2
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    • pp.60-63
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    • 2000
  • In this work, the carbon fibers-reinforced carbon matrix composites made with different carbon char yields of phenolic resin matrix have been characterized by mechanical flexural tests for acoustic emission properties. The composites had been fabricated in the form of two-dimensional polyacrylonitrile based carbon fibers during the carbonization process. It was found that the composites made with the carbon char yield-rich of resin matrix result in better mechanical interfacial properties, i.e., the interlaminar shear strength (ILSS) of the composites. The data obtained from the acoustic emission monitored appeared to show that the composites made with carbon char yield-rich were also more ductile. From the acoustic emission results, the primary composite failure was largely depended on the debonding at interfaces between fibers and matrix. The interlaminar shear strengths of the composites were correlated with the acoustic emission results.

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Pressure Effects on the Morphology Development of C/C Composites During Carbonization

  • Joo, Hyeok-Jong;Ryu, Seung-Hee;Ha, Hun-Seung
    • Carbon letters
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    • v.1 no.3_4
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    • pp.158-164
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    • 2001
  • It is well known that the fabrication process of carbon/carbon composites is very complex. Above all, the carbonization process have major effect on the morphology development of carbon matrix. Carbon/carbon composites of 4-directional fiber preform were fabricated using the coal tar based pitch as a matrix precursor in this study. According to carbonization pressure of 1 bar, 100 bar, 600 bar, and 900 bar, morphological changes of cokes and matrix of composites were discussed. As the carbonization pressure increased to 600 bar, the flow pattern morphology of bulk mesophse was well developed. On the contrary, mosaic pattern morphology was found in case of 900 bar of carbonization pressure. It is confirmed that the carbonization pressure have profound effect on the degree of graphitization and crystal size of carbon matrix. Even in the highly densified carbon/carbon composites, large voids were still found in the matrix pocket region.

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Modification of C/C Composite Bipolar Plate by Addition of Electro-Conductive Carbon Black

  • Ryu, Seung-Kon;Hwang, Taek-Sung;Lee, Seung-Goo;Lee, Sun-A;Kim, Chang-Soo
    • Carbon letters
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    • v.2 no.3_4
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    • pp.165-169
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    • 2001
  • Modification of C/C composite bipolar plate for improving electrical conductivity was carried out by addition of electroconductive carbon black (EC-CB). Carbon black was carefully mixed to methanol-containing phenolic resin, impregnated into 2D-carbon fabrics, hot pressed and then carbonized to obtain composite plate. Inclusion of electro-conductive carbon black enhanced the electrical conductivity of the C/C composites by increasing the conduction path. Addition of 10 vol% carbon black increased the electrical conductivity from 5.5/${\Omega}cm$ to 32/${\Omega}cm$ and reduced the crack formation by filling effect, resulting in the increase of flexural properties of composite plate. However, at carbon black content over 10 vol%, flexural properties decreased by delaminating role of excess carbon black at the interface in C/C composites.

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Influence of Carbon Black as a Conductor on Electrode Characteristics for Lithium Secondary Battery

  • Yoon, Se-Rah;Lee, Joong-Kee;Ju, Jae-Beck;Cho, Byung-Won;Park, Dal-Keun
    • Carbon letters
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    • v.3 no.1
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    • pp.17-24
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    • 2002
  • The electrochemical behavior of the $LiCoO_2$ electrode, containing carbon black as a conductor, depends upon the nature and characteristics of carbon black. In this study, six different kinds of carbon blacks were employed to investigate the relationship between the properties of carbon blacks and electrochemical characteristics of the electrode. The larger amount of surface oxygen functional groups brought the lower electrical conductivity for the carbon blacks. The electrical conductivity of carbon blacks was closely related to the impurities such as ash and volatile content. The rate capability and cyclability of the electrode were improved with the higher conductivity of carbon blacks used. So, it can be concluded that high conductive carbon black plays an important role as a conductor for high rate of charge-discharge capability and initial efficiency.

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Study on the Fabrication and the Properties of C/C Composite from Clutter Chopped Carbon Fiber by Warmer-Molding Technology

  • Chen, Jianxun;Huang, Qizhong
    • Carbon letters
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    • v.7 no.4
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    • pp.241-244
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    • 2006
  • Carbon/Carbon composite was been manufactured by the technology of warmer-molding process of clutter chopped carbon fiber, using phenolic resin as an adhesive. The degree of graphitization, the microstructure and the friction properties were studied. The results show that the clutter chopped carbon fiber fully scatter in the Carbon/Carbon composite and the degree of graphitization of phenolic resin can reach up to 86.2%, this matrix carbon can form the continuous and stable graphitic thin film on the friction surface during braking process so that the composite has fine friction properties and low wear rate.

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Carbon Assimilation and Respiration of Daphnia magna with Varying Algal Food Quality

  • Park, Sang-Kyu;Goldman Charles R.
    • Journal of Ecology and Environment
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    • v.29 no.5
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    • pp.433-438
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    • 2006
  • To elucidate the mechanisms by which algal food quality affect Daphnia growths, we measured carbon incorporation rates and respiration rates of Daphnia magna with Cryptomonad Rhodomonas minuta, green algae Scenedesmus acutus and cyanobacteria Synechococcus sp. with varying physiological states as food. Carbon assimilation rates were high with R. minuta and S. acutus and low with Synechococcus sp. showing a similar pattern to the growth rate pattern. There was no clear difference among respiration rates of three algal species. Carbon assimilation rates and respiration rates of D. magna appeared to be independent on Molar C:P ratios in algal foods. Carbon growth efficiencies (incorporated carbon per assimilated carbon amount) were lower when D. magna fed with Synechococcus sp. than fed with R. minuta or S. acutus. Analysis of variance results show that carbon assimilation rates which were sum of incorporation and respiration rates and carbon growth efficiencies were only dependant on species affiliation. Overall, our results showed that algal species with varying ${\omega}3$ polyunsaturated fatty acid content led different carbon incorporation rates and overall carbon assimilation rates of D. magna.

Relationship Between Exothermic Heat and Carbon Contents of Pitch-based Carbon Fiber

  • Lee, Jae-Young;Oh, Jong-Hyun;Yang, Xiao Ping;Ryu, Seung-Kon
    • Carbon letters
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    • v.10 no.3
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    • pp.202-207
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    • 2009
  • Pitch-based carbon fiber tows were prepared from naphtha cracking bottom oil by reforming and carbonization. The relationship between exothermic heat and carbon contents of the fiber was investigated by changing the carbonization conditions. The carbon contents and the crystallinities of isotropic pitch-based carbon fibers were 86.8~93.8 wt% and 33.7~40.1%, respectively, which were linearly proportional to the increase of carbonization temperature from 700 to $1000^{\circ}C$. The exothermic heat (temperature increase) of fiber tows was measured in a short time, which was also linearly proportional to the increase of carbon contents due to the increase of crystallinity, even though the crystallinity was low. Therefore, the carbon contents or carbonization degree of fibers can rapidly and indirectly be estimated by measuring the surface temperature increase of fibers.

A Study on the Metrial Charcterisitics of Material Quality and Milling of Axle Materials for a Automobile (자동차 차축 소재의 금속적 특징 및 밀링 절삭 특성 연구)

  • 채왕석
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.6 no.1
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    • pp.77-83
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    • 1997
  • In this paper, we have studied internal quality including chemical compositions, microscopic structure and nonmetalic inclusion of test materials. We have analyzed dynamic characteristics of cutting force of milling including tensile strength value, hardness etc. Test materials are used in the tempered carbon steel and the non-tempered carbon steel. The obtained results are as follows: 1. In analyzing internal quality, the tempered carbon steel have typical martensite structure and the non-tempered carbon steel have ferrite + pearlite structure. 2. Yield strength, tensile strength and hardness value are in the non-tempered carbon steel but elongation is maximum value in the tempered carbon steel. 3. Cutting force is smaller non-tempered carbon steel than tempered carbon steel when feed speed and depth on cut is constant. 4. Cutting force is smaller non-tempered carbon steel than tempered carbon steel when cutting speed and depth of cut is constant.

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