Influence of various plasma treatment on the properties of carbon nanotubes for composite applications.
ABSTRACT In present work, the effects of hydrogen and oxygen plasma treatments on the structural properties of carbon nanotubes (CNTs) synthesized by catalytic CVD (Chemical Vapor Deposition) have been systematically investigated. Field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy were used to characterize the microstructural changes of the CNTs. The oxygen plasma treatment resulted in that the nanoparticles were appeared at the surface of CNTs. At high r.f. power (300 Watt), the microstructure of CNT was changed from nanotube type to nano particles. Long plasma treatment time changed the CNT morphology dramatically. For hydrogen plasma, however, there was no change in microstructure of CNT From the Raman analysis, the crystallinity of CNT was deteriorated by the plasma treatment, regardless of plasma power, treatment time, and gas types. The CNTs treated in oxygen plasma for 90 min showed excellent dispersion properties in aqueous solution.
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ABSTRACT: A systematic study has been performed in order to find an appropriate medium for solubilization/dispersion of pristine single-walled carbon nanotubes (SWCNTs). Five solvents, all featuring high electron pair donicity (β) and low hydrogen bond parameter (α) have demonstrated the ability to readily form stable dispersions. The best dispersions have been characterized by UV/visible-NIR spectra, ESR spectra, and atomic force microscopy (AFM).The Journal of Physical Chemistry B 08/2000; 104(38). · 3.38 Impact Factor
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ABSTRACT: Li-doped films with controlled stoichiometries were prepared by performing redox reactions between single-wall carbon nanotubes thin films and solutions of organic radical anions. A monotonic upshift of the tangential modes is evidenced for LixC compounds (0<~x<~0.17). A similar doping dependence of the Raman profile is observed for vapor-phase Rb-doped samples. This universal behavior of the doping-induced upshift of the tangential modes is concomitant to a loss of absorption bands in the optical spectra and to a monotonic increase of the conductivity.Physical review. B, Condensed matter 10/2002; 64(24). · 3.66 Impact Factor
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ABSTRACT: An in situ polycondensation approach was applied to functionalize multiwalled carbon nanotubes (MWNTs), resulting in various linear or hyperbranched polycondensed polymers [e.g., polyureas, polyurethanes, and poly(urea-urethane)-bonded carbon nanotubes]. The quantity of the grafted polymer can be easily controlled by the feed ratio of monomers. As a typical example, the polyurea-functionalized MWNTs were measured and characterized in detail. The oxidized MWNTs (MWNT-COOH) were converted into acyl chloride-functionalized MWNTs (MWNT-COCl) by reaction with neat thionyl chloride (SOCl2). MWNT-COCl was reacted with excess 1,6-diaminohexane, affording amino-functionalized MWNTs (MWNT-NH2). In the presence of MWNT-NH2, the polyurea was covalently coated onto the surfaces of the nanotube by in situ polycondensation of diisocyanate [e.g., 4,4'-methylenebis(phenylisocyanate)] and 1,6-diaminohexane, followed by the removal of free polymer via repeated filtering and solvent washing. The coated polyurea content can be controlled to some extent by adjusting the feed ratio of the isocyanato and amino groups. The structure and morphology of the resulting nanocomposites were characterized by FTIR, NMR, Raman, confocal Raman, TEM, EDS, and SEM measurements. The polyurea-coated MWNTs showed interesting self-assembled flat- or flowerlike morphologies in the solid state. The signals corresponding to that of the D and G bands of the carbon nanotubes were strongly attenuated after polyurea was chemically tethered to the MWNT surfaces. Comparative experiments showed that the grafted polymer species and structures have a strong effect on the Raman signals of polymer-functionalized MWNTs.The Journal of Physical Chemistry B 07/2005; 109(24):11925-32. · 3.38 Impact Factor