• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.160-160
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• 2011

In this work, magnesium (Mg) nanoparticles were plated onto the surfaces of multi-walled carbon nanotubes (MWNTs) in order to investigate the effects of their presence on the high pressure hydrogen storage behaviors of the resultant Mg/MWNTs. The structure of Mg/MWNTs was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The pore structure and total pore volumes of Mg/MWNTs were analyzed by $N_2$/77 K adsorption isotherms. The hydrogen storage behaviors of the Mg/MWNTs were investigated by BEL-HP at 298K and 100 bar. From the results, it was found that Mg particles were homogeneously distributed on the MWNT surfaces. The hydrogen storage capacity increased in proportion to the Mg content. It can be concluded that Mg paricles play an important role in hydrogen storage characteristics due to the hydrogen spillover effect.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.1
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• pp.65-69
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• 2010

In this study, we compared two methods(an acid treatment in strong acid reflux and a heat treatment in air atmosphere) for hydrophilic surface treatment of multi-walled carbon nanotubes(MWNT) to enhance the capcity of $RuO_2$/MWNT composite electrode materials for ultracapacitor. Both treatments generated a number of defects on the surface of MWNT by the breakage of $\pi$ bond in graphene layer at which carboxyl groups were introduced. However, the degree of hydrophilicity generated by strong acid treatment was higher than that by heat treatment in air, which was revealed by the quantitative measurement of surface carboxyl groups by using Boehm titration. The increased hydrophilicity save rise to an improved dispersity of $RuO_2$ nanoparticles on MWNT. Finally, the improved dispersity resulted in the capacity enhancement of composite electrode materials for ultracapacitor.

• Fibers and Polymers
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• v.7 no.4
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• pp.323-327
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• 2006

Poly(vinyl alcohol) (PVA)/multi-walled carbon nanotube (MWNT) composite films were prepared by casting a DMSO solution of PVA and MWNTs, whereby the MWNTs were dispersed by sonication. A significant improvement in the mechanical properties of the PVA drawn films was achieved by the addition of a small amount of MWNTs. The initial modulus and the tensile strength of the PVA drawn film increased by 30 % and 45 %, respectively, with the addition of 1 wt% MWNTs, which are close to those calculated from the rule of mixtures, and were strongly dependent upon the orientation of the PVA matrix. The mechanical properties, however, were not improved with a further increase in the MWNT content. The orientation of MWNTs in the composite was not well developed compared to that of the PVA matrix. This result suggests that the improvement of the molecular orientation of the PVA matrix plays a major role in the increase of the mechanical propeties of the drawn PVA/MWNT composite films.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1596-1600
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• 2010

Surface functionalization of multi-walled carbon nanotubes (MWNTs) was carried out by means of acid treatment. The presence of oxygen functional groups on the surface of acid-treated MWNTs was confirmed with the aid of Fourier transform infrared spectroscopy and X-ray spectroscopy. In addition, carboxylic groups generally formed on the surface of acid-treated MWNTs, and the dispersion was increased by the duration of the acid treatment. The zeta-potential indicated the surface charge transfer and the dispersion of MWMTs. Morphological characteristics of acid-treated MWNTs were also observed using a transmission electron microscopy, X-ray diffraction, and Raman analysis, which was revealed the significantly unchanged morphologies of MWNTs by acid treatment. The hydrogen adsorption capacity of the MWNTs was evaluated by means of adsorption isotherms at 77 K/1 atm. The hydrogen storage capacity was dependent upon the acid treatment conditions and the formation of oxygen functional groups on the MWNT surfaces. The latter have an important effect on the hydrogen storage capacity.

• Macromolecular Research
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• v.13 no.3
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• pp.206-211
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• 2005

Multi-walled carbon nanotubes (MWNTs) pre-treated by concentrated mixed acid or oxidized at high temperature were melt mixed with poly(methyl methacrylate) (PMMA) using a twin screw extruder. The morphologies and electrical properties of the MWNT/PMMA composites were investigated. The thermally treated MWNTs (t-MWNTs) were well dispersed, whereas the acid treated MWNTs (a-MWNTs) were highly entangled, forming large-sized clusters. The resulting electrical properties of the composites were analyzed in terms of the carbon nanotube (CNT) dispersion. The experimental percolation threshold was estimated to be $3 wt\%$ of t-MWNTs, but no percolation occurred at similar concentrations in the a-MWNT composites, due to the poor dispersion in the matrix.

• Journal of Sensor Science and Technology
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• v.16 no.5
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• pp.377-383
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• 2007

We describe the fabrication and characterization of a doubly clamped multi-walled carbon nanotube (MWNT). The device was assembled by an application of electric field in solution. The MWNT was clamped on end of metal trench electrodes in solution and deposited with additional platinum (Pt) on edge of electrode for firmly suspending the MWNT by focused ion beam (FIB). The MWNTs range of diameter and length were 100 to 150 nm and 1.5 to $2{\mu}m$, respectively. Electrical characteristics of fabricated devices were measured by I-V curve and impedance analysis. The mechanical deformation was observed by resistivity in high air pressure. Resonant frequency around 6.8 MHz was detected and resistivity was linearly varied according to the magnitude of air pressure. This device could have potential applications in nanoelectronics and various sensors.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.200-203
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• 2007

Carbon nanotubes (CNTs) have attracted an increasing attention due to their superior mechanical properties and potential application in industries. The strength of CNT has been predicted or calculated through several simulation techniques but actual experiments on stress-strain behavior are rare due to its dimensional limit, nanoscale positioning/manipulation, and instrumental resolution. We have attempted to observe straining responses of a multi-walled carbon nanotube (MWNT) with different growth methods by performing an in-situ tensile testing in a scanning electron microscope. Linear deformation and fracture behaviors of MWNT were successfully observed and its force-displacement curve was also measured from the bending stiffness and displacement of the force sensor and manipulator. We also obtained different tensile load of carbon nanotube with different growth methods.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.465-466
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• 2006

A single-wall carbon nanotube (SWCNT) has been studied as a material of Nano-Eletro-Mechanical-System (NEMS) device together with various nanowires. In order for oscillation of a multi-wall carbon nanotube (MWCNT) or a single-walled carbon nanotube (SWCNT) on plane surface, it needs suspension of a CNT across trench electrodes. So we propose fabrication method of a MWCNT resonator using dielectrophoresis and show successful results of suspeneded MWNT. Thin electrodes with large gaps could not suspend small diameter MWNT but thicker electrodes could. Thin MWNT could be suspended only when the electrode gap was reduced.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.3
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• pp.18-21
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• 2008

The study deals with the effects of parameters in the synthesis of carbon nanotubes in liquid nitrogen to find the most appropriate conditions such as electrical voltage and time that give carbon nanotubes with large volume and less proportion of impurity, which is a non-nanotubed carbon. The experiment employed the method of arc-discharge between graphite cathode and anode which are immersed in liquid nitrogen. The electrical DC current of 60A and 70A were applied with the time period ranging from 10 seconds to 25 seconds. It was found that the electrical current of 60A and 13 seconds arc-discharge time allowed the largest volume of carbon nanotubes generation. The longer time leads to more impurities around the carbon nanotubes. By the filtration of CNTs-suspended solution using 0.2 micrometers porous paper filter and the characterization using TEM, the carbon nanotubes synthesized in the study were approximately 25 layers multi-walled nanotubes with the average diameter of 18.2 nanometers.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.2
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• pp.50-54
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• 2005

We report a simple, low cost, and reliable method for assembling a multi-walled nanotube (MWNT) to the end of a metal coated scanning probe microscopy (SPM) tip. By dropping the MWNT solution and applying an electric field between an SPM tip and an electrode, MWNTs which were dispersed into a dielectric solution were directly assembled onto the apex of the SPM tip due to the attraction by the dielectrophoretic force. The effective measurement of a MWNT -attached SPM tip was demonstrated by direct comparison with AFM images of a standard sample with a bare AFM tip.