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2008, Vol.9, No.4

  • 1.

    Sorption of Chromium Ions from Aqueous Solution onto Chemically Activated Carbons Developed from Maize Cobs

    A. M. Youssef | Th. El-Nabarawy | Mona A. Shouman and 1other persons | 2008, 9(4) | pp.275~282 | number of Cited : 1
    Chemically activated carbons were prepared from maize cobs, using phosphoric acid of variable concentration. The textural parameters of the activated carbons were determined from the nitrogen adsorption isotherms measured at 77 K. The chemistry of the carbon surface was determined by measuring the surface pH, the pHPZC and the concentration of the carbon - oxygen groups of the acid type on the carbon surface. Kinetics of Cr(VI) sorption/reduction was investigated at 303 K. Two processes were investigated in terms of kinetics and equilibrium namely; Cr(VI) removal and chromium sorption were studied at various initial pH (1-7). Removal of Cr(VI) shows a maximum at pH 2.5. At pH <2.5, sorption decreases because of the proton competition with evolved Cr(III) for ion exchange sites. The decrease of sorption at pH >2.5 is due to proton insufficiency and to the decrease of the extent of Cr(VI) reduction. The chemistry of the surface of activated carbon is an important factor in determining its adsorption capacity from aqueous solutions particularly when the sorption process involves ion exchange.
  • 2.

    Controlled Release Behavior of Temperature Responsive Composite Hydrogel Containing Activated Carbon

    Hyung-Il Kim | 윤주미 | Im Ji Sun and 2other persons | 2008, 9(4) | pp.283~288 | number of Cited : 1
    The composites of temperature-sensitive hydrogel and activated carbons were prepared in order to improve both themechanical strength of hydrogel matrix and the loading capacity of drug in a hydrogel drug delivery system. The swelling ofcomposite hydrogel was varied depending on the temperature. Both the swelling and the release behavior of the compositehydrogel were varied depending on the kind of activated carbon. The release behavior showed the high efficiency which isimportant for practical applications.
  • 3.

    Characterization of Heat Reformed Naphtha Cracking Bottom Oil Extracts

    RYU SEUNG KON | Jong Hyun Oh | Jae Young Lee and 2other persons | 2008, 9(4) | pp.289~293 | number of Cited : 6
    Naphtha Cracking Bottom (NCB) oil was heat reformed at various reforming temperature and time, and the volatile extracts were characterized including yields, molecular weight distributions, and representative compounds. The yield of extract increased as the increase of reforming temperature (360 ~ 420˚C) and time (1 ~ 4 hr). Molecular weight of the as-received NCB oil was under 200, and those of extracts were distributed in the range of 100-250, and far smaller than those of precursor pitches of 380-550. Naphtalene-based compounds were more than 70% in the as-received NCB oil, and most of them were isomers of compounds bonding functional groups, such as methyl (CH3-) and ethyl (C2H5-). When the as-received NCB oil was reformed at 360˚C for 1 hr, the most prominent compound was 1,2-Butadien, 3-phenyl- (24.57%), while naphthalene became main component again as increasing the reforming temperature.
  • 4.

    Photo Catalytic Activity of CNT-TiO2 Nano Composite in Degrading Anionic and Cationic Dyes

    Young-Seak Lee | Kim SangJin | Im Ji Sun and 2other persons | 2008, 9(4) | pp.294~297 | number of Cited : 2
    A CNT-TiO2 nano composite was prepared from titanium chloride (TiCl4) via sol-gel process using multi walled carbonnano tube (MWCNT) followed by calcination at 450˚C. Spectral analysis revealed that the formed TiO2 resided on the carbonin anatase form. The effect of adsorption was investigated using aqueous solution of methylene blue and procion blue dye. The photochemical reaction of CNT-TiO2 composite in aqueous suspensions was studied under UV illumination in batchprocess. The reaction was investigated by monitoring the discoloration of the dyes employing UV-Visible spectro-photometerictechnique as a function of irradiation time. The catalyst composites were found to be efficient for the photodegradationof the dye.
  • 5.

    Electromagnetic Interference Shielding Properties of CO2 Activated Carbon Black Filled Polymer Coating Materials

    Myung-Soo Kim | Quanli Hu | 2008, 9(4) | pp.298~302 | number of Cited : 1
    Carbon blacks could be used as the filler for the electromagnetic interference (EMI) shielding. The poly vinyl alcohol (PVA) and polyvinylidene fluoride (PVDF) were used as the matrix for the carbon black fillers. Porous carbon blacks were prepared by CO2 activation. The activation was performed by treating the carbon blacks in CO2 to different degrees of burnoff. During the activation, the enlargement of pore diameters, and development of microporous and mesoporous structures were introduced in the carbon blacks, resulting in an increase of extremely large specific surface areas. The porosity of carbon blacks was an increasing function of the degree of burn-off. The surface area increased from 80 m2/g to 1142 m2/g and the total pore volume increased from 0.14073 cc · g−1 to 0.9343 cc · g−1. Also, the C=O functional group characterized by aldehydes, ketones, carboxylic acids and esters was enhanced during the activation process. The EMI shielding effectiveness (SE) of raw N330 carbon blacks filled with PVA was about 1 dB and those of the activated carbon blacks increased to the values between 6 and 9 dB. The EMI SE of raw N330 carbon blacks filled with PVDF was about 7 dB and the EMI SE increased to the range from 11 to 15 dB by the activation
  • 6.

    PEMFC Operation Connected with Methanol Reformer System

    Yong-gun Shul | Jung-hyun Lee | Sang-sun Park and 4other persons | 2008, 9(4) | pp.303~307 | number of Cited : 0
    The studies on integrated operation of fuel cell with fuel processor are very essential prior to its commercialization. In this study, Polymer Electrolyte Membrane Fuel Cell (PEMFC) was operated with a fuel processor, which is mainly composed of two parts, methanol steam reforming reaction and preferential oxidation (PROX). In fuel processor, ICI 33-5 (CuO 50%, ZnO 33%, Al2O3 8%, BET surface area: 66 m2g−1) catalyst and CuO-CeO2 catalyst were used for methanol steam reforming, preferential oxidation (PROX) respectively. PEMFC was operated by hydrogen fuel generated from fuel processor. The resulting gas from PROX reactor is used to operate PEMFC equipped with our prepared anode and cathode catalyst. PtRu/C catalyst gives more tolerance to CO.
  • 7.

    Studies on the Stabilization of Rayon Fabrics for Preparing Carbon Fabrics: 2. Fast Isothermal Stabilization Processes at High Temperature

    Donghwan Cho | Sung Bong Yoon | Chae Wook Cho and 2other persons | 2008, 9(4) | pp.308~315 | number of Cited : 5
    In the present study, fast isothermal stabilization processes for rayon precursor fabrics were performed at 350˚C and 400˚C within 3 minutes and the chemical and physical characteristics of the stabilized fabrics were investigated. In addition, rayon precursor fabrics were pre-treated with three different phosphorous-based flame retardants and then stabilized. The effect of flame retardants on the chemical composition, thermal shrinkage, weight change, thermal stability and XRD results was examined, comparing with those of the precursor fabrics. The result showed that the stabilization of rayon fabrics was most effective as the stabilization temperature was 350oC, the stabilization time was 3 min, and the pre-treatment with phosphoric acid of 1 vol%. The carbon contents of stabilized rayon fabrics were increased with increasing stabilization temperature and time, whereas the oxygen contents were decreased. Also, it is likely that the pre-treatment with phosphoric acid plays a role in retarding the change of chemical structure of rayon fabric. The XRD result was quite consistent with the result showing the effect of phosphoric acid on the chemical composition, thermal shrinkage and weight reduction of rayon fabric.
  • 8.

    Ablative Properties of 4D Carbon/Carbon Composites by Combustion Test

    Hyeok-Jong Joo | Jong-Min Park | Chong-Jin Ahn | 2008, 9(4) | pp.316~323 | number of Cited : 0
    The factors that influence ablation resistance in fiber composites are properties of the reinforced fiber and matrix, plugging quantity of fiber, geometrical arrangement, crack, pore size, and their distributions. To examine ablation resistance according to distribution of crack and pore size that exist in carbon/carbon composites, this study produced various sizes of unit cells of preforms. They were densified using high pressure impregnation and carbonization process. Reinforced fiber is PAN based carbon fiber and composites were heat-treated up to 2800˚C. The finally acquired density of carbon/carbon composites reached more than 1.932 g/cm3. The ablation test was performed by a solid propellant rocket engine. The erosion rate of samples is below 0.0286 mm/s. In conclusion, in terms of ablation properties, the higher degree of graphitization is, the more fibers that are arranged vertically to the direction of combustion flame are, and the less interface between reinforced fiber bundle and matrix is, the better ablation resistance is shown.
  • 9.

    Carbon Fibers (II): Recent Technical Trends and Market Prospects of Carbon Fibers

    PARK SOOJIN | Min-Kang Seo | Byung-Gak Min | 2008, 9(4) | pp.324~339 | number of Cited : 2
    The principal aims of the review paper are (1) to establish broad overview information, both qualitative and quantitative, relating to the world market for polyacrylonitrile (PAN) or pitch-based carbon fibers; and (2) to generate an effective analysis and break down of consumption by process route and eventual end-use. The review paper also designed specifically to provide subscribers with an accurate, independent, and realistic assessment of the current status and future perspective of the market for carbon fibers in the world. The world market for carbon fibers continues to grow rapidly, fuelled by new industrial end uses, such as sport and leisure goods, aerospace, automotive applications, civil engineering and infrastructure repair, and immerging applications in energy generation. Demands for properties of carbon fibers used in those applications include many things such as strength, toughness, fatigue property, corrosion resistance, heat resistance, etc., and these become to be higher level. On the other hand, demands for manufacturing technologies of carbon fibers become to be difficult with these demands for properties, and these are wide variety such as high efficiencies, high qualities, many functions, labor saving, and low cost. In this review paper, thus, the recent carbon fibers corresponded to these needs, and its latest manufacturing technologies as well as market prospects are described.