Carbon nanotube formation from milled iron-phthalocyanine

Organometallics supply carbon and metal catalyst needed for carbon nanotube synthesis. It is shown that experiments involving prior milling of iron-phthalocyanine (FePc, FeC32H16N8) before pyrolysis at 800 oC in argon produces carbon nanotubes with diameters ranging from 5 to 15 nm. Under the same conditions, the diameters of nanotubes produced from non-milled FePc range from 20 to more than 50 nm. Milling decreases the onset of sublimation of FePc from about 450 to 200 oC and also reduces the activation energy barrier of sublimation at 360 oC from 287 to 193 kJ/mol. This appears to be due to changes in molecular packing of the phthalocyanine precursor. It is suggested that the decrease in nanotube diameter is due to greater homogeneity in the gas phase on pyrolysis after milling, which leads to more systematic capture of carbon species during the catalytic growth of the carbon nanotubes.