Orientation and morphological evolution of catalyst nanoparticles during carbon nanotube growth

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

Research output: Contribution to journalArticlepeer-review

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

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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