Purification of multi-walled carbon nanotubes through microwave heating of nitric acid in a closed vessel

Fu-Hsiang Ko*, Chung Yang Lee, Chu Jung Ko, Tieh Chi Chu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

97 Scopus citations

Abstract

We demonstrate that microwave-assisted heating in 5 mL of nitric acid eliminates impurities, such as amorphous carbon, carbon nanoparticles, and metals, from multi-walled carbon nanotubes (MWNTs). Heating the closed reaction vessel under microwave irradiation at 160 °C for 30 min is a very effective means of purifying the MWNTs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirm that these reaction conditions are beneficial for removing the impurities and ensuring that the MWNTs remain intact. In contrast, a purification temperature of 180 °C provides too strongly oxidizing conditions that destroy the MWNTs. The ratio of the G and D bands in the Raman spectra also confirms that a temperature of 160 °C is optimal. The defect peak that we observed in the differential thermogravimetry (DTG) analysis of the raw material was not present after microwave purification. The presence of metal impurities in the MWNTs can be reduced significantly when using this method.

Original languageEnglish
Pages (from-to)727-733
Number of pages7
JournalCarbon
Volume43
Issue number4
DOIs
StatePublished - 21 Feb 2005

Keywords

  • A. Carbon nanotubes
  • C. Electron microscopy
  • D. Defects
  • Raman spectroscopy

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