On the iron-catalysed growth of single-walled carbon nanotubes and encapsulated metal particles in the gas phase

The production of single-walled carbon nanotubes (SWNT) by catalytic dispro portionation of carbon monoxide on iron particles in the gas phase was stud ied. The addition of hydrogen to the reactants was found to increase the SW NT yield relative to the competing formation of encapsulated iron particles . Adding acetylene, however, did not result in a significant change of the SWNT growth but gave rise to the formation of unwanted self-pyrolysis produ cts. Iron particles are seen to decorate the SWNT and are shown to be singl e crystalline with several layers of encapsulation by graphitic carbon. All these observations are discussed with respect to the catalytic growth mech anism of SWNT and encapsulated metal particles from CO and hydrocarbon mole cules.