The effect of growth temperature and iron precursor on the synthesis of high purity carbon nanotubes

Aligned multiwalled carbon nanotubes (MWCNTs) of high purity, low metal content and narrow size distribution were synthesized by chemical vapour deposition of acetylene along with iron-organometallic compounds in the temperature range 650–850 °C. The obtained MWCNTs were characterized by thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy and N2 adsorption. The effect on the carbon nanotube structure of different parameters such as, reaction temperature, nature of the iron catalyst precursor, the reaction mixture flow rate and the relative proportion of metal precursor to carbon source, has been studied. It was found that the outer and inner diameters of the carbon nanotubes were directly proportional to the iron catalyst concentration. Moreover, the wall numbers and the diameters of the carbon nanotubes were related to their apparent specific surface areas.