• Carbon letters
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• 제15권1호
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• pp.71-76
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• 2014

Activated carbon nanofibers (ACNF) were prepared from polyacrylonitrile (PAN)-based nanofibers using $CO_2$ activation methods with varying activation process times. The surface and structural characteristics of the ACNF were observed by scanning electron microscopy and X-ray diffraction, respectively. $N_2$ adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller and Dubinin-Radushkevich equations. As experimental results, many holes or cavernous structures were found on the fiber surfaces after the $CO_2$ activation as confirmed by scanning electron microscopy analysis. Specific surface areas and pore volumes of the prepared ACNFs were enhanced within a range of 10 to 30 min of activation times. Performance of the porous PAN-based nanofibers as an electrode for electrical double layer capacitors was evaluated in terms of the activation conditions.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 봄 학술발표회 논문집
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• pp.111-116
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• 1991

In order to discuss the mechanical properties of carbon fiber reinforced polymer impregnated cement composties with silica powder, experimental studies on CFRC were carried out. The types of fiber used which are in CFRC are PAN-based carbon fiber and Pitch-based carbon fiber. To examine the effects of types, length, contents of carbon fibers and matrices, their properties of fresh and hardened CFRC were tested. According to the test results, compressive, tensile flexural strength of polymer impregnated CFRC were remarkably increased more than that of air cured and autoclaved CFRC. Also, polymer impregnated CFRC were considerably effective in improving thoughness, freezing-thaw resistance and loss of shrinkage compared with air cured and autoclaved CFRC.

• 공업화학
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• 제17권5호
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• pp.532-538
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• 2006

탄화 및 활성화 조건을 매개체로 여러 등급의 Polyacrylonitrile (PAN)계 ACF (ACF : Activated Carbon Fiber)를 제조하여 최적의 비표면적을 나타내는 활성화 공정을 알아보았고, 가장 큰 비표면적을 갖는 PAN계 ACF에 대한 표면특성 및 독성가스 등에 대한 흡착특성을 분석하였다. 시험결과 활성화 온도가 증가할수록 비표면적이 증가하고 탄화 온도가 감소할수록 비표면적이 감소하였고, $900^{\circ}C$로 15 min간 탄화한 후 $900^{\circ}C$로 30 min간 활성화 공정을 거친 ACF가 $1204m^2/g$의 가장 높은 비표면적을 나타내었고 요오드 및 테러용 독성가스에 대한 흡착 성능시험 결과 기존의 흡착제보다 우수하였다. 또한 선택적 흡착을 위한 기능성을 부여하기 위하여 기존의 금속염을 침적하는 방법을 대체하여 비교적 안정화된 금속나노입자(Ag, Pt, Cu, Pd)를 제조하여 첨착하였고 이에 대한 표면특성 및 $SO_{2}$에 대한 흡착특성을 분석하였다. 금속나노입자 첨착 ACF에 대한 $SO_{2}$ 흡착성능 시험결과 Ag, Pt, Cu 나노입자를 첨착한 ACF는 무첨착 ACF의 파과시간(326 sec)과 비교 할 때 크게 변함이 없었으나 Pd 나노입자를 첨착한 ACF는 파과시간이 925 sec로 $SO_{2}$ 흡착성능이 매우 우수함을 알 수 있었다.

• Carbon letters
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• 제5권1호
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• pp.12-17
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• 2004

In this study, the oxyfluorination of PAN-based carbon fibers was undertaken at room temperature using fluorine-oxygen mixtures, and the influence of oxyfluorination on properties was investigated. The surface characteristics of the modified fiber were determined by using X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analyzer. The oxyfluorination of carbon fibers was one of the more effective methods to increase surface wettability by the formation of semicovalent C-F bond and C-O bond depending on reaction conditions. When oxygen mole fraction is increased from 0.5 to 0.9, it is probable that attached fluorine atoms at the surface of the fibers reacted with other components. As increased oxyfluorination time and decreased its pressures, semi-covalent peak is increased at 0.5 of oxygen mole fraction. The total surface free energy of oxyfluorinated carbon fibers decreased with increasing oxygen mole fraction over 0.5. These results indicate that the surface of carbon fibers became much more hydrophilic after the short oxyfluorination. The surface free energy of oxyfluorinated carbon fibers progressively decreased after 10 min treatment. The polar components of surface free energies were however, significantly higher for all oxyfluorinated samples than that for the untreated carbon fiber.

• Carbon letters
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• 제26권
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• pp.11-17
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• 2018

Milled carbon fiber (mCF) was prepared by a ball milling process, and X-ray diffraction (XRD) diffractograms were obtained by a $2{\theta}$ continuous scanning analysis to study mCF crystallinity as a function of milling time. The raw material for the mCF was polyacrylonitrile-based carbon fiber (T700). As the milling time increased, the mean particle size of the mCF consistently decreased, reaching $1.826{\mu}m$ at a milling time of 18 h. The XRD analysis showed that, as the milling time increased, the fraction of the crystalline carbon decreased, while the fraction of the amorphous carbon increased. The (002) peak became asymmetric before and after milling as the left side of the peak showed an increasingly gentle slope. For analysis, the asymmetric (002) peak was deconvoluted into two peaks, less-developed crystalline carbon (LDCC) and more-developed crystalline carbon. In both peaks, Lc decreased and $d_{002}$ increased, but no significant change was observed after 6 h of milling time. In addition, the fraction of LDCC increased. As the milling continued, the mCF became more amorphous, possibly due to damage to the crystal lattices by the milling.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.304-307
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• 2015

Carbon nanotubes (CNTs) have been widely accepted and used as the enhancer for polymer nano-composites due to their remarkable mechanical properties. Understandably, the CNT fiber-polymer matrix interface plays a major role in determining the properties of the CNT-polymer nano-composites. Here, using the LCAODFT Lab tool available on the EDISON Nano-Physics site, we performed first-principles density-functional theory calculations to determine the atomic configurations and binding energies of the CNTs in contact with polymers. For the polymer matrixes, we chose poly(acrylonitrile) (PAN), which is one of the most well-known polymer matrixes for the carbon nanofiber nanocomposites. Different chiralities and diameters of pristine CNTs were considered, and several PAN-CNT configurations were prepared based on the atomistic positions and directions of cyano group in PAN. The most favorable configuration of PAN was obtained when the PAN bound parallel to the surface of CNT. Our finding indicates the binding configurations are determined by the direction of the cyano group dominantly rather than the atomistic position of PAN, or the symmetry of CNTs. The result of increasing the length of CNT diameter suggests that PAN is inclinable to align evenly on the surface of relatively large size of CNT with the configuration parallel to the surface. These results obtained in this study will provide the starting point for the design of improved PAN-CNT composites for the next-generation ultra-strong and ultra-light carbon nanofibers.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.40-43
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• 1999

Electrochemical surface treatment of PAN-based carbon fibers in acidic electrolyte has been studied in increasing the surface functional groups on fiber surfaces for the improvement of fiber-matrix adhesion of the resulting composites. According to the FT-IR and XPS measurements, it reveals that the oxygen functional groups on fibers are largely influence on the composite mechanical behaviors, whereas the nitrogen functional groups are not affected in the system. In this work, a good correlation between surface functionality and mechanical properties is established.

• Carbon letters
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• 제9권3호
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• pp.200-202
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• 2008

In order to improve the thermal stability of PAN-based electrospun fibers, AP-PER-MEL and $TiO_2$ were added in to the fibers as additives. The polymer composite with uniformly mixed additional agents was obtained. In case of non-treated sample, the fibers were burn off completely with high rate within $620^{\circ}C$. But in case of treated samples (EF-M and EF-MT), it is sure that the thermal stability was improved by studying TGA data and ISO flammability test about 20 and 30%, respectively. A synergy effect of adding two kinds of agents (AP-PER-MEL and $TiO_2$) into PAN-based electrospun fibers was confirmed. Through SEM images, it is confirmed that the fiber shape can be kept even after addition of agents (AP-PER-MEL and $TiO_2$). Finally the thermal stability of fibers was largely developed with keeping the nature of PAN-based fibers effectively.

• Carbon letters
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• 제11권4호
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• pp.285-292
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• 2010

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 $350^{\circ}C$. 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 $-25^{\circ}C$ to $50^{\circ}C$. 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.

• Carbon letters
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• 제12권1호
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• pp.31-38
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• 2011

This study experimentally investigated dicyclohexylammonium 2-cyanoacrylate (CA) as a potential comonomer for polyacrylonitrile (PAN) based carbon fiber precursors. The P(AN-CA) copolymers with different CA contents (0.19-0.78 mol% in the feed) were polymerized using solution polymerization with 2,2-azobis(isobutyronitrile) as an initiator. The chemical structure and composition of P(AN-CA) copolymers were determined by proton nuclear magnetic resonance and elemental analysis, and the copolymer composition was similar to the feeding ratio of the monomers. The effects of CA comonomer on the thermal properties of its copolymers were characterized differential scanning calorimetry (DSC) in nitrogen and air atmospheres. The DSC curves of P(AN-CA) under nitrogen atmosphere indicated that the initiation temperature for cyclization of nitrile groups was reduced to around $235^{\circ}C$. The heat release and the activation energy for cyclization reactions were decreased in comparison with those of PAN homopolymers. On the other hand, under air atmosphere, the P(AN-CA) with 0.78 mol% CA content showed that the initiation temperature of cyclization was significantly lowered to $160.1^{\circ}C$. The activation energy value showed 116 kJ/mol, that was smaller than that of the copolymers with 0.82 mol% of itaconic acids. The thermal stability of P(AN-CA), evidenced by thermogravimetric analyses in air atmosphere, was found higher than PAN homopolymer and similar to P(AN-IA) copolymers. Therefore, this study successfully demonstrated the great potential of P(AN-CA) copolymers as carbon fiber precursors, taking advantages of the temperature-lowering effects of CA comonomers and higher thermal stability of the CA copolymers for the stabilizing processes.