Structural improvement of CVD multi-walled carbon nanotubes by a rapid annealing process

Abstract

Generally, due to structural disorders in multi-walled carbon nanotubes (MWCNTs) synthesized by chemical vapor deposition (CVD), most of their properties are much below the expected values. A novel technique has been developed in this investigation for structural improvement of CVD MWCNTs using a rapid annealing process. Direct observation by transmission electron microscope (TEM) indicates obvious structural changes in the nanotubes after a rapid annealing process between 2000°C and 2800°C, while nanotubes with twisty shells and kinked walls have been observed as the annealing temperature approaches 3000°C. Decrease of ID/IG ratio in Raman spectra, increase of the starting oxidation temperature observed in Thermogravimetric analysis (TGA), as well as increase in electrical conductivity of nanotube powders suggests the reconstruction toward more ordered nanotube structure after a rapid high temperature annealing process.