After being irradiated by carbon ions with the energy of 40 keV at the fluence of 10~(16)/cm~(-2) , many of multi-walled carbon nanotubes evolved into amorphous carbon nanowires and amorphous nanotubes. In some irradiated nanotubes, it can be found that transition areas of amorphous nanotubes and amorphous nanowires coexist. Moreover, during this evolving process, some crossed nanotubes were welded together, and these welded junctions may have great applications in nanotube/molecular electronics. Meanwhile, the mechanism on the appearance of this phenomenon was also discussed qualitatively.

Key words: CARBON, NANOPHASE MATERIALS, ION BEAMS, IRRADIATION