• Carbon letters
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• v.13 no.3
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• pp.157-160
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• 2012

In this work, iron oxide ($Fe_3O_4$) nanoparticles were deposited on multi-walled carbon nanotubes (MWNTs) by a simple chemical coprecipitation method and $Fe_3O_4$-decorated MWNTs (Fe-MWNTs)/polypyrrole (PPy) nanocomposites (Fe-MWNTs/PPy) were prepared by oxidation polymerization. The effect of the PPy on the electrochemical properties of the Fe-MWNTs was investigated. The structures characteristics and surface properties of MWNTs, Fe-MWNTs, and Fe-MWNTs/PPy were characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The electrochemical performances of MWNTs, Fe-MWNTs, and Fe-MWNTs/PPy were determined by cyclic voltammetry and galvanostatic charge/discharge characteristics in a 1.0 M sodium sulfite electrolyte. The results showed that the Fe-MWNTs/PPy electrode had typical pseudo-capacitive behavior and a specific capacitance significantly greater than that of the Fe-MWNT electrode, indicating an enhanced electrochemical performance of the Fe-MWNTs/PPy due to their high electrical properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.63-63
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• 2007

Carboxylated multi-walled carbon nanotubes (MWNTs) were in detail characterized by XRD, XPS, FTIR, and thermogravimetric measurements. Carboxylic acid groups were functionalized to MWNTs using aqueous acid solutions. The change. of sonication and reflux conditions rarely influenced the degree of carboxylation on MWNTs, but reduced the thermal stability of the resulting carboxylated MWNTs. The characteristic Bragg peaks of pristine and carboxylated MWNTs were analyzed by XRD measurements. After acid treatment the diffraction peaks (100), (101), and (102) of pristine MWNTs disappeared, but the diffraction peak (002) was preserved in the carboxylated MWNTs. The introduction of carboxylic acid groups on MWNTs caused to improve the dispersibility of the resulting carboxylated MWNTs in water.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.10
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• pp.878-882
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• 2007

Carboxylated multi-walled carbon nanotubes (MWNTs) were in detail characterized by XRD, XPS, FTIR, and thermogravimetric measurements. Carboxylic acid groups were functionalized to MWNTs under aqueous acid condition. The changes of sonication and reflux conditions rarely influenced the degree of carboxylation on MWNTs, but decreased the thermal stability of the resultant carboxylated MWNTs. XRD results showed that the diffraction peaks (100), (101), and (102) of pristine MWNTs disappeared after acid treatment, but the diffraction peak (002) was Preserved in the carboxylated MWNTs. The introduction of carboxylic acid groups on MWNTs caused to improve the dispersibility of the resultant carboxylated MWNTs in water.

• Polymer(Korea)
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• v.31 no.5
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• pp.436-441
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• 2007

In this work, the multiwalled carbon nanotubes(MWNTs) were functionalized with sodium dodecylbenzene sulfonate(SDBS) and then MWNTs/Lyocell composite fibers were prepared. The properties of MWNTs, the functionlization on the surface of MWNTs and their dispersion in the cellulose matrix were characterized by TEM, SEM, WAXD and FT-IR. The results showed that SDBS has been coated successfully onto the surface of the MWNTs by functionlization. This can improve effectively the dispersion uniformity of MWNTs in NMMO aqueous solution and is helpful to prepare a spinnable spinning dope. Moreover, the resultant MWNTs/Lyocell composite fibers still have cellulose II crystal structure, and their tensile strength and initial modulus increased with the increasing draw ratio and reached the optimal value with adding 1 wt% MWNTs. The thermal stability of the composite fiber was also improved by the addition of the MWNTs.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.133.1-133.1
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• 2010

In this work, carbon black(CBs)-embed multi-walled carbon nanotubes (MWNTs) as conductive fillers for activated carbon(ACs)-based electrodes for supercapacitor were prepared by chemical reduction of oxidized MWNTs and CBs. The effect of CBs-MWNT composites on electrochemical performances of ACs-based electrodes were investigated as a function of CB-MWNT ratio. It was found that CBs-MWNTs composites were formed by the reduction reaction of the functional groups of oxidized MWNTs and CBs. It was resulted in the conjugation of CBs onto the MWNT having high surface area and aspect ratio, leading to the enhanced electrical properties of MWNTs. The electrochemical performances, such as current density, charge-discharge, and specific capacitance of the ACs/CBs-MWNT electrodes were higher than that of ACs/MWNTs and conventional ACs/CB electrodes, which was attributed to the synergistic effect of CBs-MWNTs as a conductive filler.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.124-128
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• 2009

In this study, the effect of multi-step purification or functionalization on physicochemical properties of multi-walled carbon nanotubes (MWNTs)/epoxy (EP) nanocomposites was investigated. The nanocomposites containing multi-step purified MWNTs showed a stronger influence on $T_g$ and increased in mechanical properties in comparison to nanocomposites containing the same amount of only purified MWNTs. Consequently, the multi-step purification of MWNTs led to an improvement of thermomechanical properties of nanocomposites, resulting from improving the intermolecular interaction of MWNTs in epoxy matrix resins.

• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.401-406
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• 2005

In this work, the effect of chemical treatment of multiwalled carbon nanotubes (MWNTs) on glass transition temperature (Tg), thermal stability, and dynamic viscoelastic behaviors of MWNTs-reinforced epoxy matrix composites has been studied by differencial scanning calorimeter (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) measurements. The MWNTs were chemically treated with 35 wt％ $H_3PO_4$ (A-MWNTs) or 35 wt％ KOH (B-MWNTs) solutions and the changes of surface properties of chemically treated MWNTs were examined by pH, acid and base values, Fourier transfer-infrared spectroscopy (FT-IR), and x-ray photoelectron spectroscopy (XPS) analyses. The chemical treatments based on acid and base reactions led to a significant change of surface characteristics and chemical compositions of the MWNTs, especially A-MWNTs/epoxy composites had higher thermal stability and dynamic viscoelastic properties than those of B-MWNTs and non-treated MWNTs/epoxy composites. These results were probably due to the improvement of interfacial bonding strength, resulting from the acid-base interaction and hydrogen bonding between the epoxy resins and the MWNT fillers.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.355-362
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• 2009

The chemical modification of multi-wall carbon nanotubes (MWNTs) is an emerging area in material science. In the present study, hydroxyl functionalized oxovanadium(IV) Schiff-base; N,N'-bis(4-hydroxysalicylidene)-ethylene-1, 2-diamineoxovanadium(IV), [VO($(OH)_2$-salen)]; has been covalently anchored on modified MWNTs. The new modified MWNTs ([VO($(OH)_2$-salen)]-MWNTs]) have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron (XPS), UV-Vis, Diffuse reflectance (DRS), FT-IR spectroscopy and elemental analysis. The analytical data indicated a composition corresponding to the mononuclear complex of tetradentate Schiff-base ligand. The characterization of the data showed the absence of extraneous complex, retention of MWNTs and covalently anchored on modified MWNTs. Liquid-phase oxidation of cyclohexane with $H_2O_2$ to a mixture of cyclohexanone, cyclohexanol and cyclohexane-1,2-diol in $CH_3$CN have been reported using oxovanadium(IV) Schiff-base complex covalently anchored on modified MWNTs as catalysts. This catalyst is more selective toward cyclohexanol formation.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.214.1-214.1
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• 2011

In this work, the electrochemical properties of the surface treated multi-walled carbon nanotubes (MWNTs) are investigated for supercapacitors. Nitrogen- and oxygen functional groups containing MWNTs are prepared by nitrogen precursors and acidic treatment, respectively. The surface properties of the MWNTs are confirmed by X-ray photoelectron spectroscopy (XPS) and Zeta-potential measurements. The electrochemical properties of the MWNTs are investigated by cyclic voltammetry, impedance spectra, and charge-discharge cycling performance in 1 M $H_2SO_4$ at room temperature. As a result, these functionalized MWNTs lead to an increase in the specific capacitance as compared with the pristine MWNTs. It proposes that the pyridinic and pyridinic-N-oxides nitrogen species influence on the specific capacitance due to their positive charges, and thus an improved electron transfer at high current loads, since they are the most important functional groups affecting capacitive behaviors.

• Transactions on Electrical and Electronic Materials
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• v.4 no.4
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• pp.1-6
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• 2003

Aluminum oxide ($Al_2O_3$) nanotubes and nanorods were fabricated by coating and filling of multiwalled carbon nanotubes (MWNTs) with atomic-layer deposition (ALD). $Al_2O_3$ material was deposited on the MWNTs at a substrate temperature of $300^{\circ}C$ using trimethylaluminum and distilled water. Transmission electron microscopy, high resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and selected area electron diffraction of the deposited MWNTs revealed that amorphous $Al_2O_3$ material coats the MWNTs conformally and that this material fills the inside of the MWNTs. These illustrate that ALD has an excellent capability to coat and fill any three-dimensional shapes of MWNTs conformally without producing any crystallites.