Raman spectroscopic and thermogravimetric studies of high-crystallinity SWNTs synthesized by FH-arc discharge method

In this work, we produced SWNTs by a hydrogen DC arc discharge with evaporation of carbon anode containing 1 at.% Fe catalyst in H2–Ar mixture gas. This was named FH-arc discharge method. In order to refine the experimental conditions for high yields and high qualities, diameter distributions of SWNTs in the pristine materials were studied by Raman spectroscopy as a function of pressure of H2–Ar mixture gas (200–520 Torr) and discharge voltage (28–34 V). Judging from the RBM-frequency regions in the Raman spectra (< 400 cm− 1), as-grown SWNTs of smaller diameters increased while increasing the discharge voltage. On the other hand, with increment of the ambient gas pressure the purity of as-grown SWNTs decreased.