• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.782-785
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• 2013

Multi-walled carbon nanotubes were synthesized on Ni catalyst using thermal chemical vapor deposition. By introducing ammonia gas during the CNT synthesis process, clean and vertically aligned CNTs without impurities could be prepared. As the ammonia gas increased a partial pressure of hydrogen in the mixed gas during the CNT synthesis process, we could control the CNT synthesis rate appropriately. As the ammonia gas has an etching ability, amorphous carbon species covering the catalyst particles were effectively removed. Therefore catalyst particles could maintain their catalytic state actively during the synthesis process. Finally, we could obtain clean and vertically aligned CNTs by introducing $NH_3$ gas during the CNT synthesis process.

• Korean Journal of Materials Research
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• v.21 no.2
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• pp.89-94
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• 2011

In this work, fabrication and electrochemical analysis of an individual multi-walled carbon nanotube (MWNT) electrode are carried out to confirm the applicability of electrochemical sensing. The reactive ion etching (RIE) process is performed to obtain sensitive MWNT electrodes. In order to characterize the electrochemical properties, an individual MWNT is cut by RIE under oxygen atmosphere into two segments with a small gap: one segment is applied to the working electrode and the other is used as a counter electrode. Electrical contacts are provided by nanolithography to the two MWNT electrodes. Dopamine is specially selected as an analytical molecule for electrochemical detection using the MWNT electrode. Using a quasi-Ag/AgCl reference electrode, which was fabricated by us, the nanoelectrodes are subjected to cyclic voltammetry inside a $2{\mu}L$ droplet of dopamine solution. In the experiment, RIE power is found to be a more effective parameter to cut an individual MWNT and to generate "broken" open state, which shows good electrochemical performance, at the end of the MWNT segments. It is found that the pico-molar level concentration of analytical molecules can be determined by an MWNT electrode. We believe that the MWNT electrode fabricated and treated by RIE has the potential for use in high-sensitivity electrochemical measurement and that the proposed scheme can contribute to device miniaturization.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.1
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• pp.21-25
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• 2004

From the gradual increasing state of charge (GISOC) observations, electrochemical behavior of multi-walled carbon nanotube│(lM LiP $F_{6}$ , EC,DEC,DME 3:5:5 volume ratio)│lithium cells was evaluated using the galvanostatic charge-discharge process. A MWCNT delivers a specific charge capacity of 1,300 mAh/g in a Li cell when cycled up to an end voltage of 0 V (vs. Li/L $i^{＋}$ )at a constant current rate every 10 hours. However, in the present study, the specific discharge capacity obtained is 338 mAh/g, thus amounting to a coulombic efficiency of only 26％. Further, when the MWCNT│Li cells were tested using the GISOC method, two distinguishable linear-fit ranges were observed due to the intercalation/deintercalation of lithium, which were found to have II $E_1$, IIC $s_1$ and II $E_2$of 27.3％, 372 mAh/g, and 25.5％, respectively. Q $c_1$, could be calculated from the data of IIE and IICs of each range by the modified equation "II $C_{sum}$= $\Sigma$( $Q_{C}$- $Q_{D}$)=(II $E_{1}$$^{-1}$ ) $Q_{Dl}$ ＋(II $E_2$$^{-1}$ -1) ( $Q_{D2}$- $Q_{Dl}$ ) ＋ IIC $s_1$= $Q_{Cl}$ - $Q_{Dl}$ ". Results of the GISOC method could be converted to the results of galvanostatic charge-discharge process, irrespective of the state of charge of the cell or battery.ery.y.y.

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2387-2392
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• 2009

A composite film of multi-walled carbon nanotube (MWCNT)/sol-gel-derived zinc oxide(ZnO)/Nafion has been utilized as an efficient immobilization matrix for the construction of a highly sensitive and stable tris(2,2'-bipyridyl) ruthenium(II) (Ru(${bpy)_3}^{2+})$ electrogenerated chemiluminescence (ECL) sensor. The electrochemical and ECL behaviors of Ru(${bpy)_3}^{2+})$ ion-exchanged into the composite film were strongly dependent upon the sol-gel preparation condition, the amount of MWCNT incorporated into the ZnO/Nafion composite film, and the buffer solution pH. The synergistic effect of MWCNTs and ZnO in the composite films increased not only the sensitivity but also the long-term stability of the ECL sensor. The present ECL sensor based on the MWCNT/ZnO/Nafion gave a linear response ($R^2$ = 0.999) for tripropylamine concentration from 500 nM to 1.0 mM with a remarkable detection limit (S/N = 3) of 15 nM. The present ECL sensor showed outstanding long-term stability (94% initial signal retained for 5 weeks). Since the present ECL sensor exhibits large response towards NADH, it could be applied as a transduction platform for the ECL biosensor in which the NADH is produced from the dehydrogenase-based enzymatic reaction in the presence of NA$D^+$ cofactor.

• Carbon letters
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• v.13 no.2
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• pp.126-129
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• 2012

Nanocomposite films were made by a simple solution casting method in which multi-walled carbon nanotubes (MWCNT) and magnetite nanoparticles ($Fe_3O_4$) were used as dopant materials to enhance the electrical conductivity of chitosan nanocomposite films. The films contained fixed CNT concentrations (5, 8, and 10 wt%) and varying $Fe_3O_4$ content. It was determined that a 1:1 ratio of CNT to $Fe_3O_4$ provided optimal conductivity according to dopant material loading. X-ray diffraction patterns for the nanocomposite films, were determined to investigate their chemical and phase composition, revealed that nanoparticle agglomeration occurred at high $Fe_3O_4$ loadings, which hindered the synergistic effect of the doping materials on the conductivity of the films.

• Composites Research
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• v.30 no.2
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• pp.165-168
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• 2017

Coiled polymer actuators fabricated by twisting polymer fishing lines or sewing threads respond to heating and cooling with their contraction and relaxation. However, their actuation speed is highly dependent on the heating and cooling rates. In order to improve the actuation speed, the coiled polymer actuator was coated with polydimethylsiloxane composites. The introduction of multi-walled carbon nanotubes into the polydimethylsiloxane improved the actuation speed by about 13%.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.214.2-214.2
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• 2011

In this work, porous carbon based electrodes are prepared by carbonization using poly(vinylidene fluoride) (PVDF)/carbon nanotube (CNT) composites to further increase the specific capacitance for supercapacitors. Electrode materials investigate the aspects of specific capacitance, pore size distribution and surface area: influence of carbonization temperatures of PVDF/CNT composites. The electrochemical properties are investigated by cyclic voltammetry, impedance spectra, and galvanostatic charge-discharge performance with in $TEABF_4$ (tetraethylammonium tetrafluoroborate)/acetonitrile as non-aqueous electrolyte. From the results, the highest value of specific capacitance of ~101 $F{\cdot}g^{-1}$ is obtained for the samples carbonized at $600^{\circ}C$. Furthermore, pore size of samples control be low 7 nm through carbonization process. It is suggested that micropores significantly contribute to the specific capacitance, resulting from improved charge transfer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.61-61
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• 2008

Nanocomposites of metal (gold and silver) nanoparticles and multi-walled carbon nanotubes (MWNTs) were prepared with the assistance of various stabilizers for metals and MWNTs. Especially common surfactants such as poly(4-vinylpyridine) (PVP), sodium dodecyl sulfate (SDS), poly(sodium 4-styrene sulfonate) (PSS), and poly(diallyldimethylammonium) chloride (PDDA) were used for the sample preparation. Metal/MWNT nanocomposites were structurally characterized in by transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), UV/Vis spectroscopy. In addition, the electrical properties of the nanocomposites were studied by cyclic voltammetry (CV).

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.486-489
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• 2007

Carbon nanotube (CNT) cathodes having a trench structure similar to the structure of the gated triodetype cathode were successfully fabricated by a screenprinting method with multi-walled carbon nanotubes. We observed that a liquid method not only readily removes the organic residues on the CNT films, but also satisfactorily protrudes the CNTs out of the electrode surface. The CNT cathodes prepared by the liquid method showed a turned-on field of $1.4\;V/{\mu}m$. The emission current density of them was about $3.1\;mA/cm^2$ at the electric field of $3\; V/{\mu}m$. The liquid method appears to be a promising surface treatment of CNT cathode for gated triode-type FEDs applications.

• 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.