Multi-walled carbon nanotubes (MWCNTs) have been produced from ethylene by fluidized bed-catalytic chemical vapor deposition (FB-CCVD) on alumina supported iron catalyst powders. Both catalysts and MWCNTs-catalyst composites have been characterized by XRD, SEM-EDX, TEM, Mössbauer spectroscopy, TGA and nitrogen adsorption measurements at different stages of the process. The fresh catalyst is an alumina/iron oxide powder composed of amorphous iron(III) oxide nanoparticles located inside the porosity of the alumina support and of a micrometric crystalline α-iron(III) oxide surface film. The beginning of the CVD process provokes a brutal reconstruction and simultaneous carburization of the surface film that allows MWCNT nucleation and growth. These MWCNTs grow aligned between the support and the surface catalytic film, leading to a uniform consumption and uprising of the film. When the catalytic film has been consumed, the catalytic particles located inside the alumina porosity are slowly reduced and activated leading to a secondary MWCNT growth regime, which produces a generalized grain fragmentation and entangled MWCNT growth. Based on experimental observations and characterizations, this original two-stage growth mode is discussed and a general growth mechanism is proposed.
An original growth mode of MWCNTs on alumina supported iron catalysts / R. Philippe, B. Caussat, A. Falqui, Y. Kihn, P. Kalck, S. Bordere, D. Plee, P. Gaillard, D. Bernard, P. Serp. - In: JOURNAL OF CATALYSIS. - ISSN 0021-9517. - 263:2(2009 Apr), pp. 345-358. [10.1016/j.jcat.2009.02.027]
An original growth mode of MWCNTs on alumina supported iron catalysts
A. Falqui;
2009
Abstract
Multi-walled carbon nanotubes (MWCNTs) have been produced from ethylene by fluidized bed-catalytic chemical vapor deposition (FB-CCVD) on alumina supported iron catalyst powders. Both catalysts and MWCNTs-catalyst composites have been characterized by XRD, SEM-EDX, TEM, Mössbauer spectroscopy, TGA and nitrogen adsorption measurements at different stages of the process. The fresh catalyst is an alumina/iron oxide powder composed of amorphous iron(III) oxide nanoparticles located inside the porosity of the alumina support and of a micrometric crystalline α-iron(III) oxide surface film. The beginning of the CVD process provokes a brutal reconstruction and simultaneous carburization of the surface film that allows MWCNT nucleation and growth. These MWCNTs grow aligned between the support and the surface catalytic film, leading to a uniform consumption and uprising of the film. When the catalytic film has been consumed, the catalytic particles located inside the alumina porosity are slowly reduced and activated leading to a secondary MWCNT growth regime, which produces a generalized grain fragmentation and entangled MWCNT growth. Based on experimental observations and characterizations, this original two-stage growth mode is discussed and a general growth mechanism is proposed.File | Dimensione | Formato | |
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An original growth mode of MWCNTs on alumina supported iron catalysts J CATAL.pdf
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