An original growth mode of MWCNTs on alumina supported iron catalysts

Régis Philippe, Brigitte Caussat, Andrea Falqui, Yolande Kihn, Philippe Kalck, Serge Bordère, Dominique Plee, Patrice Gaillard, Daniel Bernard, Philippe Serp*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)345-358
Number of pages14
JournalJournal of Catalysis
Volume263
Issue number2
DOIs
StatePublished - Apr 25 2009

Keywords

  • Chemical vapor deposition
  • Iron catalyst
  • Multi-walled carbon nanotubes
  • Thin film
  • Vertically aligned carbon nanotubes

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

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