Formation and deformation of multiwall carbon nanotubes in arc discharge

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