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2010, Vol.11, No.4

  • 1.

    Influence of Processing on Morphology, Electrical Conductivity and Flexural Properties of Exfoliated Graphite Nanoplatelets–Polyamide Nanocomposites

    Wanjun Liu | Inhwan Do | Hiroyuki Fukushima and 1other persons | 2010, 11(4) | pp.279~284 | number of Cited : 4
    Graphene is one of the most promising materials for many applications. It can be used in a variety of applications not only as a reinforcement material for polymer to obtain a combination of desirable mechanical, electrical, thermal, and barrier properties in the resulting nanocomposite but also as a component in energy storage, fuel cells, solar cells, sensors, and batteries. Recent research at Michigan State University has shown that it is possible to exfoliate natural graphite into graphite nanoplatelets composed entirely of stacks of graphene. The size of the platelets can be controlled from less than 10 nm in thickness and diameters of any size from sub-micron to 15 microns or greater. In this study we have investigated the influence of melt compounding processing on the physical properties of a polyamide 6 (PA6) nanocomposite reinforced with exfoliated graphite nanoplatelets (xGnP). The morphology, electrical conductivity, and mechanical properties of xGnP-PA6nanocomposite were characterized with electrical microscopy, X-ray diffraction, AC impedance, and mechanical properties. It was found that counter rotation (CNR) twins crew processed xGnP/PA6 nanocomposite had similar mechanical properties with co-rotation (CoR) twin screw processed or with CoR conducted with a screw design modified for nanoparticles (MCoR). Microscopy showed that the CNR processed nanocomposite had better xGnP dispersion than the (CoR) twin screw processed and modified screw (MCoR) processed ones. It was also found that the CNR processed nanocomposite at a given xGnP content showed the lowest graphite X-ray diffraction peak at 26.5o indicating better xGnP dispersion in the nanocomposite. In addition, it was also found that the electrical conductivity of the CNR processed 12 wt.% xGnP-PA6 nanocomposite is more than ten times higher than the CoR and MCoR processed ones. These results indicate that better dispersion of an xGnP-PA6 nanocomposite is attainable in CNR twins crew processing than conventional CoR processing.
  • 2.

    Fabrication and Electrical, Thermal and Morphological Properties of Novel Carbon Nanofiber Web/Unsaturated Polyester Composites

    김성환 | Kwon Oh Hyeong | Donghwan Cho | 2010, 11(4) | pp.285~292 | number of Cited : 0
    Novel unsaturated polyester composites with PAN-based nanofiber, stabilized PAN nanofiber, and carbonized nanofiber webs have been fabricated, respectively, and the effects of the nanofiber web content on their electrical resistivity, the thermal stability, dynamic storage modulus, and fracture surfaces were studied. The result demonstrated that the introduction of just one single layer (which is corresponding to 2 wt.%) of the carbonized nanofiber web to unsaturated polyester resin (UPE) could contribute to reducing markedly the electrical resistivity of the resin reflecting the percolation threshold, to improving the storage modulus, and to increasing the thermal stability above 350oC. The effect on decreasing the resistivity and increasing the modulus was the greatest at the carbonized PAN nanofiber web content of 8 wt.%, particularly showing that the storage modulus was increased about 257~283% in the measuring temperature range of −25oC to 50oC. The result also exhibited that the carbonized PAN nanofibers were distributed uniformly and compactly in the unsaturated polyester, connecting the matrix three-dimensionally through the thickness direction of each specimen. It seemed that such the fiber distribution played a role in reducing the electrical resistivity as well as in improving the dynamic storage modulus.
  • 3.

    New Application of Clay Filler for Carbon/Carbon Composites and Improvement of Filler Effect by Clay Size Reduction

    정의경 | 김진호 | Lee, Young-Seak | 2010, 11(4) | pp.293~297 | number of Cited : 3
    To investigate new potential application of a clay material for C/C composites, illite added C/C composites were prepared with various illite contents. The improvement of filler effect by illite size reduction was also investigated using wet ballmilling by evaluating illite/phenolic resin infiltration using bulk density and porosity measurements, chemical structural changes of the composites using XRD, and thermal oxidation stability in air of the composites using TGA. The size reduction of illite resulted in narrower particle size distribution and improved illite infiltration into carbon preform. And the resultant C/C composites prepared with illite had even more improved thermal oxidation stability in air, showing more increased IDTs up to 100oC, compared to those of the C/C composites with pristine illite, due to the SiC formation through carbothermal reduction between illite and carbon materials. The illite induced delay in oxidation of the illite-C/C composites was also observed and the delayed oxidation behavior was attributed to the layered structure of illite, which improved illite/phenol resin infiltration. Therefore, the potential use of illite as filler to improve oxidation stability of C/C composite can be promising. And the size reduction of illite can improve its effect on the desired properties of illite-C/C composites even more.
  • 4.

    Functionalization of Multi-walled Carbon Nanotube by Treatment with Dry Ozone Gas for the Enhanced Dispersion and Adhesion in Polymeric Composites

    Jung-Hwan Kim | Byung Gil Min | 2010, 11(4) | pp.298~303 | number of Cited : 1
    A method of functionalization of multi-walled carbon nanotube (MWNT) at room temperature using dry ozone gas is described. The resulting MWNT were characterized by Fourier transform infrared, x-ray photoelectron spectroscopy, and scanning electron microscopy. Combined to these analyses and solubility in liquids, it could be concluded that the dry ozone gas exposure introduces polar functional groups such as carboxylic groups to MWNT similar to acidic modification of MWNT. Particularly, the stable dispersion of MWNT in water after ozone treatment above a critical level could be obtained, implying potential bio-application. The hydrophilic functional groups on the MWNT introduced by ozone oxidation were helpful in improving the interaction with functional groups in PA6 such as −NH2 and −CONH- resulting in improved mechanical properties.
  • 5.

    Formation of Isotropic Carbon Matrix in Carbon/Carbon Composites Derived from Pitch

    Chong-Jin Ahn | In-Seo Park | Joo Hyuk-Jong | 2010, 11(4) | pp.304~310 | number of Cited : 1
    To manufacture a carbon/carbon composite the coal tar pitch was used as the matrix precursor and the PAN (polyacrylonitrile)-based carbon fiber was used as the reinforcing material to weave 3-directional preform. For pressure carbonization HIP equipment was used to produce a maximum temperature of 1000oC and a maximum pressure of 100 MPa. The carbonization was induced by altering the dwell temperature between 250oC and 420oC, which is an ideal temperature for the moderate growth of the mesophase nucleus that forms within the molten pitch during the pressure carbonization process. The application of high pressure during the carbonization process inhibits the mesophase growth and leads to the formation of spherical carbon particles that are approximately 30 nm in size. Most particles were spherical, but some particles were irregularly shaped. The spread of the carbon particles was larger on the surface of the carbon fiber than in the interior of the matrix pocket.
  • 6.

    Influence of Glycidyl Methacrylate Grafted Multi-walled Carbon Nanotubes on Viscoelastic Behaviors of Polypropylene Nanocomposites

    Young-Sun Shim | PARK SOOJIN | 2010, 11(4) | pp.311~315 | number of Cited : 3
    In this work, the effect of glycidyl methacrylate grafted multi-walled carbon nanotubes (GMA-MWCNTs) on the viscoelastic behaviors of polypropylene (PP) based nanocomposites was studied. The GMA-MWCNTs/PP was prepared using a bravender at 200oC by melt mixing as a function of GMA-MWCNT content. The viscoelastic behaviors of GMA-MWCNTs/PP nanocomposites were measured by a rheometer. It was found that the GMA-MWCNTs were homogeneously dispersed in the PP matrix. The GMA-MWCNTs/PP nanocomposites showed higher storage modulus, loss modulus, and shear viscosity compared to pure PP nanocomposites and the maximum value was shown at 2.0 wt% GMA-MWCNTs loading. These results were probably attributed to the strong interfacial interaction between the GMA-MWCNT and the PP matrix.
  • 7.

    Molecular Dynamics Simulations of Graphite-Vinylester Nanocomposites and Their Constituents

    H. Alkhateb | A. Al-Ostaz | A. H.-D. Cheng | 2010, 11(4) | pp.316~324 | number of Cited : 0
    The effects of geometrical parameters on mechanical properties of graphite-vinylester nanocomposites and their constituents (matrix, reinforcement and interface) are studied using molecular dynamics (MD) simulations. Young’s modulii of 1.3 TPa and 1.16 TPa are obtained for graphene layer and for graphite layers respectively. Interfacial shear strength resulting from the molecular dynamic (MD) simulations for graphene-vinylester is found to be 256 MPa compared to 126 MPa for graphitevinylester. MD simulations prove that exfoliation improves mechanical properties of graphite nanoplatelet vinylester nanocomposites. Also, the effects of bromination on the mechanical properties of vinylester and interfacial strength of the graphene–brominated vinylester nanocomposites are investigated. MD simulation revealed that, although there is minimal effect of bromination on mechanical properties of pure vinylester, bromination tends to enhance interfacial shear strength between graphite–brominated vinylester/graphene-brominated vinylester in a considerable magnitude.
  • 8.

    Effect of Interphase Modulus and Nanofiller Agglomeration on the Tensile Modulus of Graphite Nanoplatelets and Carbon Nanotube Reinforced Polypropylene Nanocomposites

    Mehdi Karevan | Raghuram V. Pucha | Md A. Bhuiyan and 1other persons | 2010, 11(4) | pp.325~331 | number of Cited : 4
    This study investigates the effect of filler content (wt%), presence of interphase and agglomerates on the effective Young’s modulus of polypropylene (PP) based nanocomposites reinforced with exfoliated graphite nanoplatelets (xGnPTM) and carbon nanotubes (CNTs). The Young’s modulus of the composites is determined using tensile testing based on ASTM D638. The reinforcement/polymer interphase is characterized in terms of width and mechanical properties using atomic force microscopy which is also used to investigate the presence and size of agglomerates. It is found that the interphase has an average width of ~ 30 nm and modulus in the range of 5 to 12 GPa. The Halpin-Tsai micromechanical model is modified to account for the effect of interphase and filler agglomerates and the model predictions for the effective modulus of the composites are compared to the experimental data. The presented results highlight the need of considering various experimentally observed filler characteristics such as agglomerate size and aspect ratio and presence and properties of interphase in the micromechanical models in order to develop better design tools to fabricate multifunctional polymer nanocomposites with engineered properties.
  • 9.

    Photocatalytic Degradation of Quinol and Blue FFS Acid Using TiO2 and Doped TiO2

    Padmini. E. | Prakash Singh K. | Lima Rose Miranda | 2010, 11(4) | pp.332~335 | number of Cited : 1
    The photodegradation of the model compounds Quinol, an aromatic organic compound and Acid blue FFS, an acid dye of chemical class Triphenylmethane was studied by using illumination with UV lamp of light intensity 250W. TiO2 and TiO2 doped with Boron and Nitrogen was used as catalyst. The sol-gel method was followed with titanium isopropoxide as precursor and doping was done using Boron and Nitrogen. In photocatalytic degradation, TiO2 and doped TiO2 dosage, UV illumination time and initial concentration of the compounds were changed and examined in order to determine the optimal experimental conditions. Operational time was optimized for 360 min. The optimum dosage of TiO2 and BN doped TiO2 was obtained to be 2 mgL-1 and 2.5 mgL-1 respectively. Maximum degradation % for quinol and Blue FFS acid dye was 78 and 95 respectively, at the optimum dosage of BN-doped TiO2 catalyst. It was 10 and 4% higher than when undoped TiO2 catalyst was used.
  • 10.

    Acid Treatments of Carbon Nanotubes and Their Application as Pt-Ru/ CNT Anode Catalysts for Proton Exchange Membrane Fuel Cell

    김민식 | Sinmuk Lim | Min Young Song and 3other persons | 2010, 11(4) | pp.336~342 | number of Cited : 5
    Different oxidation treatments on CNTs using diluted 4.0 M H2SO4 solution at room temperature and or at 90oC reflux conditions were investigated to elucidate the physical and chemical changes occurring on the treated CNTs, which might have significant effects on their performance as catalyst supports in PEM fuel cells. Raman spectroscopy, X-ray diffraction and transmission electron microscope analyses were made for the acid treated CNTs to determine the particle size and distribution of the CNT-supported Pt-Ru nanoparticles. These CNT-supported Pt-based nanoparticles were then employed as anode catalysts in PEMFC to investigate their catalytic activity and single-cell performance towards H2 oxidation. Based on PEMFC performance results, refluxed Pt-Ru/CNT catalysts prepared using CNTs treated at 90oC for 0.5 h as anode have shown better catalytic activity and PEMFC polarization performance than those of the commercially available Pt-Ru/C catalyst from ETEK and other Pt-Ru/CNT catalysts developed using raw CNT, thus demonstrating the importance of acid treatment in improving and optimizing the surface properties of catalyst support.
  • 11.

    Performance of Expanded Graphite as Anode Materials for High Power Li-ion Secondary Batteries

    박도연 | Yun-Soo Lim | Myung-Soo Kim | 2010, 11(4) | pp.343~346 | number of Cited : 5
    The various expanded graphites (EGs) was prepared and applied as anode material for high power Li-ion secondary battery (LIB). By changing the processing conditions of EG, a series of EG with different structure were produced, showing the changed electrochemical properties. The charge-discharge test showed that the initial reversible capacity of EG anodes prepared at the suitable conditions was over 400 mAh/g and the charge capacity at 5 C-rate was 83.2 mAh/g. These values demonstrated the much improved electrochemical properties as compared with those for the graphite anode of 360 mAh/g and 19.4 mAh/g, respectively, showing the possibility of EG anode materials for high power LIB.
  • 12.

    A Review on Thermal Conductivity of Polymer Composites Using Carbon-Based Fillers : Carbon Nanotubes and Carbon Fibers

    홍진호 | Park Dong-Wha | SHIM SANG EUN | 2010, 11(4) | pp.347~356 | number of Cited : 8
    Recently, the use of thermal conductive polymeric composites is growing up, where the polymers filled with the thermally conductive fillers effectively dissipate heat generated from electronic components. Therefore, the management of heat is directly related to the lifetime of electronic devices. For the purpose of the improvement of thermal conductivity of composites, fillers with excellent thermally conductive behavior are commonly used. Thermally conductive particles filled polymer composites have advantages due to their easy processibility, low cost, and durability to the corrosion. Especially,carbon-based 1-dimensional nanomaterials such as carbon nanotube (CNT) and carbon nanofiber (CNF) have gained much attention for their excellent thermal conductivity, corrosion resistance and low thermal expansion coefficient than the metals. This paper aims to review the research trends in the improvement of thermal conductivity of the carbon-based materials filled polymer composites.
  • 13.

    Necessity of Development on New Types of Activated Carbons for Advanced Drinking Water Purification Technology

    김지일 | 김영하 | 장동일 and 2other persons | 2010, 11(4) | pp.357~365 | number of Cited : 2
    최근 국내의 산업화 및 공업화가 가속됨에 따라 주요 상수원의 수질이 급속히 나빠지면서 강 하류지역의 수질이 3급수이하로 떨어져 일반적인 정수방법으로는 오염물질의 제거가어렵고, 1989년 이후 중금속, trihalomethanes (THM), 페놀, 벤젠 등 각종 수돗물 유기물질 오염사고가 다발하면서 낙동강을원수로 하는 정수장에서 우선적으로 고도정수시설을 도입하게되었다 [1]. 기존의 정수처리 시설은 응집침전, 여과, 염소처리로 구성되어 있으며, 이를 청정한 원수의 처리를 목적으로 하는 ‘재래식 정수처리 공정(conventional water treatment system;CWTS)’이라고 한다 [1]. 그러나 상수원으로 사용하고 있는 주요하천이나 호수가 각종 생활용수, 공업폐수, 농업용수 등으로질소, 인 성분이 과다하게 증가되어 부영양화를 가속시키고 있으며, 각종 난분해성 물질이나 중금속 성분, 발암성물질 및 농약, 비료성분은 미량으로도 인체에 치명적인 결과를 주기 때문에 기존의 재래식 정수처리 공정만으로는 한계가 있으며, 고도정수처리 시스템의 도입이 필수 불가결한 문제로 대두되고있다 [2-4].