Formation and deformation of multiwall carbon nanotubes in arc discharge

Running arcs under both vacuum and low pressure and a jumping are under vac uum were generated with a pure graphite cathode for 1-3 s upon applying a m agnetic field. For the running arcs under both vacuum and low pressure, mul tiwall carbon nanotubes (MWNTs) were observed only at the cathode spot crat ers where the arcs were extinguished by switching the power off. At the cra ter where the cathode spot had run over, nanotubes were hardly observed. Fo r the jumping are in vacuum that was self-extinguished, only a few nanotube s were observed at the cathode spot craters. No nanotubes were observed on the surface outside the cathode spot crater for all arcs. These results rev ealed that the nanotubes arc formed, as well as destroyed, by the cathode s pot. The process of nanotube formation and deformation is discussed, taking into account the cathode spot activity and electron emission.