Carbon filament growth

The rigorous kinetic modeling with the incorporation of the diffusion step allows explaining the deactivation of the carbon filament growth and the influence of the affinity for carbon formation on the nucleation of the filamentous carbon. 

Figure 11 Tip-growth and extrusion mechanisms of carbon filament growth. (Ref. 58. Reproduced by permission of Elsevier)...

Figure 1.6 Schematic representation of (a) the diffusion-precipitation mechanism of carbon filament growth from the gas phase [32], and (b) the carbon-fiber growth mechanism proposed by OberUn et al. [33]. Important details regarding the effects of metal particle size and shape on the chemical reactions occurring at the metal-carbon interface, and thus on the nature and size of the filaments or nanotubes produced, have yet to be sorted out.

In Eq. (2) 6c is the surface coverage of carbon and Xb is the weight fraction of carbon in the segregation layer of Ni (g carbon/g Ni). The concentration of carbon dissolved in Ni at the support side of the particle equals the saturation concentration of filamentous carbon in Ni during steady-state carbon filament growth (CNi,r= C>at) (7, 13). 

Up to now, most of published work has been devoted to studies of mechanisms of carbon filament growth during conversion of carbon-containing compounds over metal catalysts [6,7]. Apparently, the properties of the filaments as adsorbents and supports have been neglected. Only a few studies on this matter may be mentioned [8,9]. The aim of this work is to bridge partially this gap and draw more attention to this promising new type of carbon materials. 

Oberlin, Endo, M and Koyama, T., Filamentous growth of carbon through benzeine decomposition, J. of Crystal Growth, 1976, 32, 335. ... 

Figure 8.4. Transmission electron microscope picture of carbon formation and filament growth on a Si02-supported Ni catalyst after exposure to a CH4 + H2 gas mixture at 1 bar...

This process of filament growth is closely related to the synthesis of single walled carbon nano-tubes. Here the aim is to selectively produce a single layer of carbon in a tube that is as long as possible. Owing to their extreme mechanical strength and interesting electronic behavior these materials have recently attracted substantial interest in materials science. 

A. Oberlin, M. Endo, T. Koyama, Filamentous growth of carbon through benzene decomposition., Journal of Crystal Growth, vol. 32, pp. 335-349,1976. 

Tibbetts, G. G., Devour, M. G. Rodda, E. J. 1987 An adsorption-diffusion isotherm and its application to the growth of carbon filaments on iron catalyst particles. Carbon. 25, No. 3, 367-375. 

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