Microwave absorption effectiveness of nonwoven support impregnated with carbon black

The microwave properties of nonwoven polyacrylonitrile fabric impregnated with 20, 33 and 50-weight % of conductive carbon black (CB) were investigated at the X-band (8 to 12 GHz). The absorption effectiveness is dependent of filler concentration especially in the lowest frequencies. The nonwoven containing 33% (w/w) of CB presented the best absorption (-22 dBm) and the greatest capability of reducing the radar cross section (RCS) of an aluminium square plate (98%). The sample with 20 and 50% of CB presented performance inferior to the 33% one. In the first case this result was due to the fact that the filler loading was still below the threshold of conductivity. In the second the loading was above the critical concentration where starts the formation of the conductive network which is deleterious for electromagnetic attenuation.