Electrical conductivity and dielectric properties of multiwalled carbon nanotube and alumina composites

Alumina/multiwalled carbon nanotube (MWNT) composites with different MWNT contents ranging from 0.5 to 10 vol % were prepared by spark plasma sintering technique. The dc electrical conductivity and dielectric properties of the composites were investigated and percolation theory was applied to demonstrate the electrical property transition from insulator to conductor. The experimental results have shown that the electrical conductivity increased sharply as the content of MWNTs was close to percolation threshold of 0.79 vol %. In the low frequency range, the dielectric constant reached as high as 5000 when the content of MWNTs was at 1.74 vol % and nearly frequency independent. (c) 2006 American Institute of Physics.