Fe3O4/α-Fe decorated porous carbon-based composites with adjustable electromagnetic wave absorption: Impedance matching and loading rate

Abstract

Electromagnetic wave (EMW) pollution is becoming more and more serious, and people pay more attention to the high value-added utilization of forest waste. Here, Fe3O4/α-Fe decorated 3D porous carbon-based composites (CF) are synthesized by in-situ pyrolysis of waste wood impregnated with Fe (acac)3 at relatively low temperature of 700 °C. Among the three obtained absorbers, CF-0.20 which is obtained with Fe (acac)3 concentration of 0.20 g/mL, exhibits the most excellent EMW absorption performance with lowest minimum reflection loss (RL) value of −50.14 dB at a matching frequency of 4.96 GHz. The multiphase induced interface polarization, the conductive network formed by massive accumulation of graphite-like carbon and the resulted dipolar polarization, and the highest relative complex permittivities and permeabilities, are main factors for such excellent EMW absorption behavior. Furthermore, evidences are provided that by changing the filler loading rate, the EM parameters of an absorber can be adjusted, and the enhanced EMW absorption behavior is achieved. For CF-0.15, the perfect matching point is 20% loading rate, 1.55 mm coating thickness at 12.64 GHz. The obtained minimum RL value is as low as −52.65 dB and an effective bandwidth as broad as 14.96 GHz. Our work demonstrates an effective method of high value-added and environmentally friendly utilization of forest waste wood, and verifies the impedance matching effect can be improved by adjusting the filler loading rate, and then excellent EMW absorbers can be obtained.