Influence of ultraviolet laser irradiation on the morphology change in carbon nanotubes

Double-walled carbon nanotubes (DWNTs) are irradiated by ultraviolet laser. Scanning electron microscopy, transmission electron microscopy and Raman spectroscopy are used to detect the morphology change in the DWNTs. It was found that carbon onions and Fe particles formed after laser irradiation. The morphology and component of these particles are dependent on the laser energy input. As laser energy input increased from 10°-107 mW·cm-2/mm, carbon onions keep growing, while size of Fe particles firstly grows and then reduces with the turning point at 103 mW·cm-2/mm.