Synthesis and growth mechanism of carbon nanotubes and nanofibers from ethanol flames.

The ethanol flame was successfully used to synthesize highly graphitic hollow-cored carbon nanotubes (CNTs) and novel disorder solid-cored carbon nanofibers (CNFs). Their morphologies were characterized by using scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. It was found that the mixture of CNTs and CNFs were grown on Ni-contained substrates, whereas only the CNFs were produced on carbon steel and low alloy steel substrates. It has been established that Ni and its compounds play a key role in CNTs growth and Fe and its compounds in CNFs growth. The models of 'hollow-cored mechanism' and 'solid-cored mechanism' were proposed to explain the present CNTs and CNFs formations, based on the theory that 'Fe has a strong affinity for carbon and Ni has a weak affinity for carbon'. It is expected that the present ethanol flame may provide a much simpler and more economic approach for mass-production of CNTs and CNFs by using large flame or multi-flames.