Compressible Fe3O4/MWCNTs-coated polymer foams for high-performance and tunable electromagnetic microwave absorption

High-performance microwave absorption materials (MAMs) over gigahertz (2 similar to 18 GHz) with tunable microwave absorption (MA) abilities have become indispensable to fight complex and changeable electromagnetic (EM) environments. Herein, Fe3O4/multiwalled carbon nanotube (MWCNTs)-coated polymer foams with high-performance and tunable MA properties were prepared using a simple dip and centrifuge method. The morphologies of the samples impregnated with resin showed that Fe3O4 /MWCNTs were coated uniformly on the porous polyurethane foams skeleton. Moreover, the polymer foams had superior MA properties, especially the samples with 20 vol% Fe3O4 and 14 vol% MWCNTs possessed 5 GHz effective absorption area (reflection loss (RL) < 10 dB) at 16 mm thickness, which was attributed to the simultaneous effect of impedance characteristic, dielectric loss, magnetic loss, and porous structures. The EM characteristics and RL properties of the prepared polymer foams could be simply tuned by mechanically compressing, and the results indicated that the RL peak value moved towards the high frequency as the compressibility increased.