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MO: Molekülphysik
MO 5: Clusters II: Non-Metal Clusters, Fullerenes, Nano-tubes (joint session A and MO)
MO 5.12: Vortrag
Dienstag, 3. April 2001, 18:30–18:45, H1012
The role of liquefaction of catalytic particles in formation of single-wall carbon nanotubes — •Andre Gorbunov1, Oliver Jost1, Wolfgang Pompe1, and Andreas Graff2 — 1University of Technology Dresden, D-01062 Dresden, Germany — 2Institute for Solid State and Materials Research (IFW), D-01069 Dresden, Germany
It is argued that the growth mechanism of single wall carbon nanotubes (SWNTs) is a kind of solid-liquid-solid catalytic graphitization of non-graphitic forms of carbon (predominantly amorphous carbon, condensed at the early stages of the carbon vapor relaxation) catalyzed by molten supersaturated carbon-metal nanoparticles. The activation energy of the SWNT growth near the yield maximum is found to be about 40 kJ/mol, which corresponds to the carbon atom diffusion through the molten catalytic metals. The liquefaction of nanoparticles of the catalytic metals in contact with the amorphous carbon is observed at temperatures far below the equilibrium eutectic one of the corresponding metal-carbon alloys. The acceleration of carbon diffusion in the molten catalytic nanoparticles and the competitive reduction of the free energy difference between the initial and the final carbon phases can qualitatively explain experimentally observed SWNT growth rates of the order of 1 micron/s and the temperature dependencies of the SWNT yield. The melting of the catalytic nanoparticles leads to a pronounced increment of carbon solubility (up to 50 at. which alters the character of the interaction of the precipitated graphitic form of carbon with the catalyst surface and presumably can result in a SWNT nucleation. Possible role of fullerenes in the nucleation of SWNTs is also discussed.
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