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spatial distributions of metal atoms during carbon swnts formation: measurements and modellingExperiments and modelling have been undertaken to clarify the role of metal catalysts during single-wall carbon nanotube formation. For instance, we wonder whether the metal catalyst is active as an atom, a cluster, a liquid or solid nanoparticle [1]. A reactor has been developed for synthesis by continuous CO2-laser vaporisation of a carbon-nickel-cobalt target in laminar helium flow. The laser induced fluorescence technique [2] is applied for local probing of gaseous Ni, Co and CZ species throughout the hot carbon flow of the target heated up to 3500 K. A rapid depletion of C2 in contrast to the spatial extent of metal atoms is observed in the plume (Fig. 1). This asserts that C2 condenses earlier than Ni and Co atoms.[3, 4]. The depletion is even faster when catalysts are present. It may indicate that an interaction between metal atoms and carbon dimers takes place in the gas as soon as they are expelled from the target surface. Two methods of modelling are used: a spatially I-D calculation developed originally for the arc process [5], and a zero-D time dependent calculation, solving the chemical kinetics along the streamlines [6]. The latter includes Ni cluster formation. The peak of C2 density is calculated close to the target surface where the temperature is the highest. In the hot region, C; is dominant. As the carbon products move away from the target and mix with the ambient helium, they recombine into larger clusters, as demonstrated by the peak of C5 density around 1 mm. The profile of Ni-atom density compares fairly well with the measured one (Fig. 2). The early increase is due to the drop of temperature, and the final decrease beyond 6 mm results from Ni cluster formation at the eutectic temperature (approx.1600 K).
Document ID
20050217224
Document Type
Conference Paper
Authors
Cau, M.
(Office National d'Etudes et de Recherches Aerospatiales Palaiseau, France)
Dorval, N.
(Office National d'Etudes et de Recherches Aerospatiales Palaiseau, France)
Attal-Tretout, B.
(Office National d'Etudes et de Recherches Aerospatiales Palaiseau, France)
Cochon, J. L.
(Office National d'Etudes et de Recherches Aerospatiales Palaiseau, France)
Loiseau, A.
(Office National d'Etudes et de Recherches Aerospatiales Paris, France)
Farhat, S.
(Paris XIII Univ. Villetaneuse, France)
Hinkov, I.
(Paris XIII Univ. Villetaneuse, France)
Scott, C. D.
(NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2004
Subject Category
Metals and Metallic Materials
Meeting Information
8th European Conference on Atomic and Molecular Physics(Rennes)
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.