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The Origin of Long-Period Lattice Spacings Observed in Iron-Carbide Nanowires Encapsulated by Multiwall Carbon Nanotubes

Published online by Cambridge University Press:  02 July 2013

Filippo S. Boi ,
Gavin Mountjoy ,
Zofia Luklinska ,
Liam Spillane ,
Lisa S. Karlsson ,
Rory M. Wilson ,
Anna Corrias  and
Mark Baxendale
Filippo S. Boi
Affiliation:
School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK
Gavin Mountjoy
Affiliation:
School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK
Zofia Luklinska
Affiliation:
School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK
Liam Spillane
Affiliation:
Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, UK
Lisa S. Karlsson
Affiliation:
Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
Rory M. Wilson
Affiliation:
School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK
Anna Corrias
Affiliation:
Dipartimento di Scienze Chimiche, Università di Cagliari, I-09042 Monserrato Cagliari, Italy
Mark Baxendale*
Affiliation:
School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK
*
*Corresponding author. E-mail: [email protected]
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Abstract

Structures comprising single-crystal, iron-carbon-based nanowires encapsulated by multiwall carbon nanotubes self-organize on inert substrates exposed to the products of ferrocene pyrolysis at high temperature. The most commonly observed encapsulated phases are Fe3C, α-Fe, and γ-Fe. The observation of anomalously long-period lattice spacings in these nanowires has caused confusion since reflections from lattice spacings of ≥0.4 nm are kinematically forbidden for Fe3C, most of the rarely observed, less stable carbides, α-Fe, and γ-Fe. Through high-resolution electron microscopy, selective area electron diffraction, and electron energy loss spectroscopy we demonstrate that the observed long-period lattice spacings of 0.49, 0.66, and 0.44 nm correspond to reflections from the (100), (010), and (001) planes of orthorhombic Fe3C (space group Pnma). Observation of these forbidden reflections results from dynamic scattering of the incident beam as first observed in bulk Fe3C crystals. With small amounts of beam tilt these reflections can have significant intensities for crystals containing glide planes such as Fe3C with space groups Pnma or Pbmn.

Keywords

iron carbidenanowireforbidden reflectionsHRTEM
Type
Materials Applications
Information
Microscopy and Microanalysis , Volume 19 , Issue 5 , October 2013 , pp. 1298 - 1302
Copyright
Copyright © Microscopy Society of America 2013 

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Footnotes

†

Current address: Sandvik AB, Kungsbron 1, Stockholm, Sweden

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