• Bulletin of the Korean Chemical Society
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• 제30권6호
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• pp.1337-1340
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• 2009

Electrical properties of a fluorinated carbon black (CB)-filled high-density polyethylene (HDPE) polymeric switch were investigated as a function of fluorination pressure at 0.1 ~ 0.4 MPa. From the FT-IR results, the absorption spectra of the fluorinated CB show an absorption band at 1400 ~ 1000 $cm^{-1}\;for\;{\nu}_{C-F}$ and the peak intensity increased with increasing fluorination pressure. Also, the analysis of XPS spectra of the fluorinated CB indicated that fluorine content increased with increasing fluorination pressure. Meanwhile, the surface free energy of the fluorinated CB decreased with increasing fluorination pressure. Consequently, the increase of fluorine contents of CB made a disappearance of negative temperature coefficient (NTC) behavior of the polymeric switch, which was probably due to the reduction of CB reaggregation after melting point of the HDPE, resulted from the decreasing of London dispersive component of the surface free energy for CB particles.

• Structural Engineering and Mechanics
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• 제54권5호
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• pp.987-998
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• 2015

In this paper, free vibrations of a clamped-clamped double-walled carbon nanotube (DWNT) under axial force is studied. By utilizing Euler-Bernoulli beam theory, each layer of DWNT is modeled as a beam. In this analysis, nonlinear form of interlayer van der Waals (vdW) forces and nonlinearities aroused from mid-plane stretching are also considered in the equations of motion. Further, direct application of multiple scales perturbation method is utilized to solve the obtained equations and to analyze free vibrations of the DWNT. Therefore, analytical expressions are found for vibrations of each layer. Linear and nonlinear natural frequencies of the system and vibration amplitude ratios of inner to outer layers are also obtained. Finally, the results are compared with the results obtained by Galerkin method.

• Advances in nano research
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• 제5권2호
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• pp.179-192
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• 2017

The transverse vibration of double walled carbon nanotube (DWCNT) embedded in elastic medium with an initial imperfection is considered. In this paper, Timoshenko beam theory is employed. However the nonlocal theory is used for modeling the nano scale of nanotube. In addition, the governing Equations of motion are obtained utilizing the Hamilton's principle and simply-simply boundary conditions are assumed. Furthermore, the Navier method is used for determining the natural frequencies of DWCNT. Hence, some parameters such as nonlocality, curvature amplitude, Winkler and Pasternak elastic foundations and length of the curved DWCNT are analyzed and discussed. The results show that, the curvature amplitude causes to increase natural frequency. However, nonlocal coefficient and elastic foundations have important role in vibration behavior of DWCNT with imperfection.

• Computers and Concrete
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• 제31권1호
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• pp.1-7
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• 2023

In this paper, Timoshenko-beam model is developed for the vibration of double carbon nanotubes. The resulting frequencies are gained for axial wave mode and length-to-diameter ratios. The natural frequency becomes more prominent for lower length-to-diameter ratios and diminished for higher ratios. The converse behavior is observed for axial wave mode with clamped-clamped and clamped-free boundary conditions. The frequencies of clamped-free are lower than that of clamped-clamped boundary condition. The eigen solution is obtained to extract the frequencies of double walled carbon nanotubes using Galerkin's method through axial deformation function. Computer softer MATLAB is used for formation of frequency values. The frequency data is compared with available literature and found to be in agreement.

• 한국식품영양과학회지
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• 제22권4호
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• pp.392-397
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• 1993

미나리의 해독작용 기전을 구명하기 위하여 미나리n-butanol 추출분획을 실험동물에 전처치한 다음, 간독소인 사염화탄소를 투여하고 급성 간손상의 정도를 확인함과 동시에 조직손상과 관련된 free radical 생성계 및 해독계효소의 활성에 미치는 영향을 검토하였다. 사염화탄소를 투여하였을 때 혈청 ALT활성 및 간조직 과산화지질의 함량이 대조군에 비하여 현저히 증가되었으나, 미나리추출물을 전처치하므로서 증가현상이 유의하게 억제되었다. 한편 미나리추출물 (50mg/kg)을 실험동물에 투여하였을 때, 간조직의 free radical 생성계 효소인 aniline hydroxylase의 활성 및 free radical 해독계 효소인 catalase 및 glutathione S-transferase의 활성과 간조직 glutathione의 함량은 유의한 변동을 나타내지 않았다. 그러나 free radical 생성계 효소의 일종인 간조직 xanthine oxidase의 활성은 미나리추출물의 투여량과 투여기간에 반비례하여 감소되었으며, 50mg/kg 및 5일간 투여군에서 유의한 억제현상을 관찰할 수 있었다. 시험관내에 미나리 추출물의 첨가농도를 증가시켜가면서 간조직 xanthine oxidase의 활성을 측정하였을 때 효소의 활성은 변동이 없었다. 이상의 실험성적들을 종합해 볼 때, 미나리 n-butanol 추출분획은 free radical 생성계 효소인 간조직 xanthine oxidase의 활성을 조절하므로서 사염화탄소에 의한 간손상을 보호해 줄 것으로 사료되어진다.

• Carbon letters
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• 제4권3호
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• pp.117-120
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• 2003

Asbestos is being replaced throughout the world among friction materials because of its carcinogenic nature. This has raised an important issue of heat dissipation in the non-asbestos brake pad materials being developed for automobiles etc. It has been found that two of the components i.e. carbon fibres as reinforcement and graphite powder as friction modifier, in the brake pad material, can playa vital role in this direction. The study reports the influence of these modifications on the thermal properties like coefficient of thermal expansion (CTE) and thermal conductivity along with the mechanical properties of nonasbestos brake pad composite samples developed in the laboratory.

• Bulletin of the Korean Chemical Society
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• 제27권4호
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• pp.581-583
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• 2006

• Carbon letters
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• 제5권3호
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• pp.108-112
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• 2004

Effect of silicon infiltration on the bend and tensile strength of 2D cross-ply carbon-carbon composites are studied. It is observed that bend strength higher than tensile strength in both types of composite is due to the different mode of fracture and loading direction. After silicon infiltrations bend and tensile strength suddenly decreases of carbon-carbon composites. This is due to the fact that, after silicon infiltration, silicon in the immediate vicinity of carbon forms the strong bond between carbon and silicon by formation silicon carbide and un-reacted silicon as free silicon. Therefore, these composites consist of three components carbon, silicon carbide and silicon. Due to mismatch between these three components secondary cracks developed and these cracks propagate from $90^{\circ}$ oriented plies to $0^{\circ}$ oriented plies by damaging the fibers (i.e., in-situ fiber damages). Hence, secondary cracks and in-situ fiber damages are responsible for degradation of mechanical properties of carbon-carbon composites after silicon infiltration which is revealed by microstructure investigation study by scanning electron microscope.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.2195-2201
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• 2010

High concentration of carbon dioxide in subway cabin may cause various adverse effects on the passengers. Because carbon dioxide is produced by breathing of passengers, carbon dioxide concentration at rush-hours is extremely high. In most cases, the ventilation is not that easy for subway cars due to the high concentration of dust in tunnels. In this study, more practical way to control carbon dioxide in subway car was suggested. The decrease of carbon dioxide concentration was observed when the system was applied to a real subway car. The regenerative method for maintenance-free carbon dioxide control system was also suggested.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.488.2-488.2
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• 2014

Carbon-based materials such as carbon nanotubes and graphene have emerged as promising building blocks in applications for nanoelectronics and energy devices due to electrical property, ease of processability, and relatively inert electrochemistry. In recent years, there has been considerable interest in core-shell nanomaterials, in which inorganic nanowires are surrounded by inorganic or organic layers. Especially, carbon encapsulated semiconductor nanowires have been actively investigated by researchers in lithium ion batteries. We report a method to synthesize silicon nanowire (SiNW) core/carbon shell structures by chemical vapor deposition (CVD), using methane (CH4) as a precursor at growth temperature of $1000{\sim}1100^{\circ}C$. Unlike carbon-based materials synthesized via conventional routes, this method is of advantage of metal-catalyst free growth. We characterized these materials with FE-SEM, FE-TEM, and Raman spectroscopy. This would allow us to use these materials for applications ranging from optoelectronics to energy devices such as solar cells and lithium ion batteries.