The effect of carbon source on the morphology of carbon nanotubes

Carbon nanotubes were prepared by the floating catalyst method using benzene and toluene as the carbon source and ferrocene with a sulfurous compound as the catalyst. The nanotubes were characterized by TEM, which shows that the ratio between benzene and toluene in the carbon source has a significant influence on the morphologies of the carbon nanotubes. Straight nanotubes are predominant with small amount of curled nanotubes when pure benzene is used as carbon source and the amount of curled nanotubes increases with increasing amount of toluene in the carbon source. Branching carbon nanotubes are predominant with small amount of straight carbon nanotubes when pure toluene is used as the source. Based on these results, the effect of the increase of toluene on the morphologies of the carbon nanotubes is discussed and a growth mechanism of the nanotubes is proposed, which indicates that the seeding carbon from the catalytic pyrolysis of toluene is different from that of benzene, causing the differences of carbon concentration on the surface of the catalyst particles, and pentagon and heptagon carbon in the hexagonal lattice of the nanotubes. This leads to the formation of carbon nanotubes with different morphologies.