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Issue 44, 2017
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The double-edged effects of annealing MgO underlayers on the efficient synthesis of single-wall carbon nanotube forests

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Abstract

Recently, the millimetre-scale, highly efficient synthesis of single-wall carbon nanotube (SWCNT) forests from Fe catalysts has been reported through the annealing of the magnesia (MgO) underlayer. Here, we report the double-edged effects of underlayer annealing on the efficiency and structure of the SWCNT forest synthesis through a temperature-dependent examination. Our results showed that the efficiency of the SWCNT forests sharply increased with increased underlayer annealing temperatures from 600 °C up to 900 °C due to a temperature-dependent structural modification, characterized by increased grain size and reduced defects, of the MgO underlayer. Beyond this temperature, the SWCNT fraction also decreased as a result of further structural modification of the MgO underlayer. This exemplifies the double-edged effects of annealing. Specifically, for underlayer annealing below 600 °C, the catalyst subsurface diffusion was found to limit the growth efficiency, and for excessively high underlayer annealing temperatures (>900 °C), catalyst coalescence/ripening led to the formation of double-wall carbon nanotubes. As a result, three distinct regions of synthesis were observed: (i) a “low yield” region below a threshold temperature (∼600 °C); (ii) an “increased yield” region from 600 to 900 °C, and (iii) a “saturation” region above 900 °C. The efficient SWCNT forest synthesis could only occur within a specific annealing temperature window as a result of this double-edged effects of underlayer annealing.

Graphical abstract: The double-edged effects of annealing MgO underlayers on the efficient synthesis of single-wall carbon nanotube forests

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Publication details

The article was received on 31 Aug 2017, accepted on 18 Oct 2017 and first published on 19 Oct 2017


Article type: Paper
DOI: 10.1039/C7NR06478K
Citation: Nanoscale, 2017,9, 17617-17622
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    The double-edged effects of annealing MgO underlayers on the efficient synthesis of single-wall carbon nanotube forests

    T. Tsuji, K. Hata, D. N. Futaba and S. Sakurai, Nanoscale, 2017, 9, 17617
    DOI: 10.1039/C7NR06478K

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