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Title: Nitrogen controlled iron catalyst phase during carbon nanotube growth

Close control over the active catalyst phase and hence carbon nanotube structure remains challenging in catalytic chemical vapor deposition since multiple competing active catalyst phases typically co-exist under realistic synthesis conditions. Here, using in-situ X-ray diffractometry, we show that the phase of supported iron catalyst particles can be reliably controlled via the addition of NH{sub 3} during nanotube synthesis. Unlike polydisperse catalyst phase mixtures during H{sub 2} diluted nanotube growth, nitrogen addition controllably leads to phase-pure γ-Fe during pre-treatment and to phase-pure Fe{sub 3}C during growth. We rationalize these findings in the context of ternary Fe-C-N phase diagram calculations and, thus, highlight the use of pre-treatment- and add-gases as a key parameter towards controlled carbon nanotube growth.
Authors:
 [1] ;  [2] ;  [3] ; ; ; ; ;  [1] ; ; ;  [4] ;  [5]
  1. Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom)
  2. (Austria)
  3. Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden (Germany)
  4. Faculty of Physics, University of Vienna, A-1090 Vienna (Austria)
  5. Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom)
Publication Date:
OSTI Identifier:
22351133
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 14; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; AMMONIA; CARBON NANOTUBES; CATALYSTS; CHEMICAL VAPOR DEPOSITION; CRYSTAL GROWTH; GASES; IRON; IRON CARBIDES; MIXTURES; NITROGEN ADDITIONS; PHASE DIAGRAMS; SYNTHESIS; X-RAY DIFFRACTION