Liquefaction of catalyst during carbon single-walled nanotube growth

Two groups of cobalt nanoparticles with spherical and disk shape were used to grow carbon single-walled nanotubes by chemical vapor deposition. To elucidate the synthesis conditions and for comparison purpose, a third group of cobalt catalyst prepared by common wet chemistry was used. After the synthesis, electron-microscopic studies revealed that the disk-shape particles with size less than 20 nm were transformed into spheres. Meanwhile, calorimetric measurements showed that the given synthesis temperature was lower than the melting point of the catalyst nanoparticles. Our result supports a growth concept based on the formation of nanotubes on carbon-induced liquefied metal nanoparticles.