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  Growth and Termination Dynamics of Multiwalled Carbon Nanotubes at Near Ambient Pressure: An in Situ Transmission Electron Microscopy Study

Huang, X., Farra, R., Schlögl, R., & Willinger, M. G. (2019). Growth and Termination Dynamics of Multiwalled Carbon Nanotubes at Near Ambient Pressure: An in Situ Transmission Electron Microscopy Study. Nano Letters, 19(8), 5380-5387. doi:10.1021/acs.nanolett.9b01888.

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 Creators:
Huang, Xing1, 2, Author              
Farra, Ramzi1, Author              
Schlögl, Robert1, 3, Author              
Willinger, Marc Georg1, 2, Author              
Affiliations:
1Inorganic Chemistry, Fritz Haber Institute, Max Planck Society, ou_24023              
2Scientific Center for Optical and Electron Microscopy, ETH Zürich, 8093 Zürich, Switzerland, ou_persistent22              
3Research Department Schlögl, Max Planck Institute for Chemical Energy Conversion, Max Planck Society, ou_3023874              

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 Abstract: Understanding the growth mechanism of carbon nanotubes (CNTs) has been long pursued since its discovery. With recent integration of in situ techniques into the study of CNT growth, important insights about the growth mechanism of CNT have been generated, which have improved our understanding significantly. However, previous in situ experiments were mainly conducted at low pressures which were far from the practical conditions. Direct information about the growth dynamics under relevant conditions is still absent and thus is highly desirable. In this work, we report atomic-scale observations of multiwalled CNT (MWCNT) growth and termination at near ambient pressure by in situ transmission electron microscopy. On the basis of the real-time imaging, we are able to reveal that the working catalyst is constantly reshaping at its apex during catalyzing CNT growth, whereas at the base the catalyst remains faceted and barely shows any morphological change. The active catalyst is identified as crystalline Fe3C, based on lattice fringes that can be imaged during growth. However, the oscillatory growth behavior of the CNT and the structural dynamics of the apex area strongly indicate that the carbon concentration in the catalyst particle is fluctuating during the course of CNT growth. Extended observations further reveal that the catalyst splitting can occur: whereas the majority of the catalyst stays at the base and continues catalyzing CNT growth, a small portion of it gets trapped inside of the growing nanotube. The catalyst splitting can take place multiple times, leading to shrinkage of both, catalyst size and diameter of CNT, and finally the growth termination of CNT due to the full coverage of the catalyst by carbon layers. Additionally, in situ observations show two more scenarios for the growth termination, that is, out-migration of the catalyst from the growing nanotube induced by (i) Oswald ripening and (ii) weakened adhesion strength between the catalyst and CNT.

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Language(s): eng - English
 Dates: 2019-07-152019-05-082019-08-012019-08-14
 Publication Status: Published in print
 Pages: 8
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 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/acs.nanolett.9b01888
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Title: Nano Letters
  Abbreviation : Nano Lett.
Source Genre: Journal
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Publ. Info: Washington, DC : American Chemical Society
Pages: 8 Volume / Issue: 19 (8) Sequence Number: - Start / End Page: 5380 - 5387 Identifier: ISSN: 1530-6984
CoNE: https://pure.mpg.de/cone/journals/resource/110978984570403