Efficient microwave energy absorption by carbon nanotubes

The absorption of energy from microwave frequency electromagnetic fields by carbon nanotubes is investigated by measuring the heating rate of dispersions of carbon nanotubes in silicone oil. Microwave absorbance of silicone oil is enhanced by 500 times with the addition of as little as 0.04 wt% carbon nanotubes. The removal of residual iron catalyst is found to have little effect on the microwave absorbance; an acid based surface modification however causes the enhancement to be lost, with the performance little better than carbon black. As-synthesized tubes showed a percolation threshold of ∼0.025 wt% for both conductivity and microwave absorbance. The efficient energy absorption is explained by a mechanism of conduction loss in the samples.