Controllable synthesis of single-, double- and triple-walled carbon nanotubes from asphalt

Single-, double- and triple-walled carbon nanotubes (SWNTs, DWNTs and TWNTs) have been controlla- bly synthesized by an arc discharge method using asphalt as carbon source. The morphology and struc- ture of three kinds of products synthesized with Fe as catalyst were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and energy dispersive X-ray spectroscopy (EDX). It was found that different buffer gases strongly affect the number layers in the synthesized nanotubes. In the He gas atmosphere only SWNTs were found to be synthesized by arc discharge in contrast to the case in Ar gas atmosphere in which only TWNTs were formed. In N2 atmosphere both SWNTs and DWNTs were synthesized. Our findings indicate that asphalt is a suitable industrial carbon source for the growth of different type nanotubes.