Microwave response of FeCo/carbon nanotubes composites

Complex permittivity and permeability of FeCo/carbon nanotubes (CNTs)-paraffin composites have been investigated at microwave frequencies between 2 and 18 GHz. Percolation threshold PC of about 34 wt. % is determined in the present system by AC conductivity measurements. Microwave absorption of FeCo/CNTs-paraffin composites is enhanced when the mass ratio of the fillers approaches PC. Meanwhile, the maximum absorption shifts to thinner thicknesses and lower frequencies by increasing the filler content. The maximum absorption was found to be -37.5 dB at 11.2 GHz with a layer thickness of 8 mm in the composites with 30 wt. % FeCo/CNTs nanocomposites. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3533254]