Single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) synthesized by a catalytic chemical vapor deposition method showed partially incorporated metal catalysts inside the graphene walls. In order to remove the metal catalysts, acid and thermal treatments were successively carried out. The methods for effective catalyst removal in SWCNTs and DWCNTs were examined by means of thermogravimetric analysis, electron microscopy, and electron paramagnetic resonance. The DWCNTs showed distinctly different metal catalyst removal behavior from that of SWCNTs due to the double-wall structure. The acid treatment is less efficient for catalyst removal from DWCNTs, while catalysts in SWCNTs are effectively removed by acid treatment. Additional thermal treatment is quite effective to remove metal catalysts from DWCNTs.
Bibliographical noteFunding Information:
J.-W. Jang acknowledges that this research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 2012R1A1A1041394 ). C.J. Lee acknowledges that this work was supported by the World Class University Project (WCU, R32-2010-000-10082-0 ) funded by the Ministry of Education, Science, and Technology, New & Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded (No. 2010T100100651 ) by the Korea Government Ministry of Knowledge Economy . This work was also supported by the National Research Foundation of Korea ( NRL Program 2012-0006259 and No. 20100-029418 ).
- Doubled-walled carbon nanotubes (DWCNTs)
- Electron paramagnetic resonance (EPR)
- Thermogravimetric analysis (TGA)
ASJC Scopus subject areas
- General Materials Science
- General Physics and Astronomy