A rapid thermal annealing process using a DC vacuum arc discharge system was shown to reduce defects in carbon nanotubes. Multi-walled carbon nanotubes exhibited high-density structural imperfections when deposited via chemical vapor deposition at relatively low temperatures (∼650C). These defects could be thermally annealed to reconstruct the graphitic structure. A vacuum arc discharge system was used to anneal the multi-walled carbon nanotubes through several cycles at high temperatures (∼1800C) followed by rapid cooling. The annealed multi-walled carbon nanotubes were characterized by Raman spectroscopy and transmission electron microscopy. Rapid heating rearranged the imperfect graphitic structure and removed the weakly bonded defects. After eliminating a defect segment, the graphene shell was reconstructed during the cooling process to produce multi-shell perfection. This method effectively reduced multi-walled carbon nanotube defects.

Defect Reduction of Multi-Walled Carbon Nanotubes by Rapid Vacuum Arc Annealing. J.T.H.Tsai, A.A.Tseng: Journal of Experimental Nanoscience, 2009, 4[1], 87-93