The double-edged effects of annealing MgO underlayers on the efficient synthesis of single-wall carbon nanotube forests. Issue 44 (8th November 2017)

• Record Type: Journal Article
• Authors: Tsuji, Takashi; Hata, Kenji; Futaba, Don N.; Sakurai, Shunsuke
• Is Part Of: Nanoscale. Volume 9:Issue 44(2017)
• Page Start: 17617
• Page End: 17622
• Publication Date: 2017-11-08
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/c7nr06478k
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : We demonstrated the profound relationship between the temperature of pre-annealing MgO underlayers and the synthesis of SWCNT forests. 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.