Microstructural changes in carbon nanotubes induced by annealing at high pressure

A study of the structural transformation of catalytically grown carbon nanotubes induced by annealing under high pressure is presented in this paper. These changes have been monitored with the atomic details using high resolution electron microscopy. The transformation from carbon nanotube into quasi-spherical onion occurs in several steps: first, the shell of the nanotube collapses, and then tends to form a sphere and subsequently an onion-like structure. The transformation process and the effect of high pressure on microstructural changes are discussed.