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 °C under flow of hydrogen. In contrast, pyrolysis at 700−800 °C 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.