Defect reduction of multi-walled carbon nanotubes by rapid vacuum arc annealing

Abstract

A rapid thermal annealing process using a DC vacuum arc discharge system was shown to reduce defects in carbon nanotubes (CNTs). Multi-walled CNTs (MWCNTs) exhibit high-density structural imperfections when deposited via chemical vapour deposition at relatively low temperatures (∼650°C). These defects can be thermally annealed to reconstruct the graphitic structure. A vacuum arc discharge system was used to anneal the MWCNTs through several cycles at high temperatures (∼1800°C) followed by rapid cooling. The annealed MWCNTs were characterised 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 MWCNT defects.