Orientation and morphological evolution of catalyst nanoparticles during carbon nanotube growth

Michael J. Behr, K. Andre Mkhoyan, Eray S. Aydil

Research output: Contribution to journalArticle

Abstract

We examined the structure, morphology, and orientation of catalyst nanoparticles used for seeding and growing multiwall carbon nanotubes (MWCNTs) by plasma enhanced chemical vapor deposition in CH4/H2 gas mixtures. Iron catalyst nanocrystals are converted to Fe3C in CH4/H2 plasmas and the MWCNTs grow from Fe3C nanocrystals. Initially faceted and equiaxed catalyst nanocrystals are distorted and elongated significantly once a tubular CNT structure is formed around the catalyst particles. Eventually, catalysts deform into elongated tear-drop shapes. Once this morphology forms, CNT structures produced are straight and have uniform diameters. Surprisingly, the Fe3C nanocrystals located inside the base of well-graphitized nanotubes do not exhibit a preferred orientation relative to the nanotube axis. Catalyst nanocrystals in a variety of orientations relative to the nanotube axis still produce well-graphitized nanotubes with similar diameters and structures.

Original languageEnglish (US)
Pages (from-to)5087-5094
Number of pages8
JournalACS Nano
Volume4
Issue number9
DOIs
StatePublished - Sep 28 2010

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Keywords

  • carbon nanotubes
  • nanotube orientation
  • plasma enhanced chemical vapor deposition

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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