Large-scale synthesis and characterization of helically coiled carbon nanotubes by use of Fe(CO)5 as floating catalyst precursor

Helically shaped multiwalled carbon nanotubes (HCNTs) (diameter 30-80 nm) were obtained as main products in large quantities by co-pyrolysis of Fe(CO)(5) as floating catalyst precursor and pyridine or toluene as carbon source at temperatures above 1000 degreesC under flow of hydrogen. In contrast, pyrolysis at 700-800 degreesC yielded only carbon-coated Fe nanoparticles. The HCNTs were characterized by electron microscopy, Raman spectroscopy, and wide-angle X-ray diffraction. The growth mechanism of the HCNTs was discussed on the basis of previously reported models.