Multiwalled carbon nanotubes produced by direct current arc discharge in hydrogen gas

Multiwalled carbon nanotubes were produced by direct current (DC) arc discharge in the mixture gas of H2–N2. Raman scattering spectroscopy was used to characterize the MWNTs. Radial breathing mode vibration signals were observed at 272 and 388 cm−1. Tangential mode vibration signal was observed at ≈1582 cm−1, and other intense signals were also observed at ≈1860 cm−1for the MWNTs produced in the gas with the H2 contents exceeding 90%. DC arc discharge in pure D2 was also carried out, by which it was confirmed that the peak position and intensity of the Raman signal at ≈1860 cm−1 were independent of whether the gas was H2 or D2. This suggests that the ≈1860 cm−1 band is not associated with hydrogen-based vibrations.