Synthesis of vertically aligned, double-walled carbon nanotubes from highly active Fe-V-O nanoparticles

Monodispersed Fe-V-O nanoparticles were prepared by a liquid-phase synthesis to be used as catalysts for carbon nanotube (CNT) growth. Vertically aligned, dense CNTs have been grown from the highly active Fe-V-O nanoparticles by chemical vapor deposition. Diameter distribution of CNTs (3.7 ± 0.6 nm) was consistent with that of the original nanoparticles (3.1 ± 0.5 nm), and the value was smaller than those of other reported vertically aligned CNTs from as-prepared nanoparticles. TEM study showed that the CNTs consisted mainly of double-walled CNTs (single: 14%, double: 74%, and triple: 12%). The CNT diameter increased to 4.4 ± 0.8 nm as the growth temperature was increased from 810 to 870 °C. Energy dispersive X-ray spectroscopy of nanoparticles before and after the CNT growth revealed that the V content decreased from 7.2 to 2.7 at.%, suggesting that the segregation of Fe and V played an important role for the high activity of the Fe-V-O nanoparticles.