Effect of purification of the electrical conductivity and complex permittivity of multiwall carbon nanotubes

In this work we report on the complex permittivity spectra and electrical c onductivity of both as-fabricated and graphitized multiwall carbon nanotube s (MWNTs). The high-temperature annealing removes the Fe3C catalyst particl es present in the as-fabricated material, enabling the intrinsic MWNT prope rties to be measured. The permittivity spectra of 1 wt % MWNT-polystyrene c omposite films are measured from 75 to 1875 MHz. Comparison of measurements with an appropriate effective medium model shows that the residual catalys t inclusions in the core of the nanotube increase the average electrical co nductivity by approximately a factor of 3.5. (C) 2001 American Institute of Physics.