Rice husk-based hierarchically porous carbon and magnetic particles composites for highly efficient electromagnetic wave attenuation

A pre-modification method and a post-modification method have been developed to fabricate rice husk-based porous carbon and magnetic particles composite absorbers (RHPC/Fe and RHPC/Co). Magnetic Fe and Co particles were selected to incorporate into rice husk-based porous carbon to make full use of the synergistic effect between dielectric loss and magnetic loss. The structure, morphology, magnetic properties and electromagnetic (EM) wave absorption performance of the synthesized absorbers were investigated in detail. Inside the porous structure, the incident EM wave can be attenuated by means of Debye dipolar relaxation-derived dielectric loss and exchange resonance-derived magnetic loss through multiple scattering and absorption. For RHPC/Fe, at a thickness of 1.4 mm, a reflection loss (RL) value of −21.8 dB was achieved with the effective absorption bandwidth (RL ≤ −10 dB) of 5.6 GHz. For RHPC/Co, an RL value of −40.1 dB was obtained with the effective absorption bandwidth (RL ≤ −10 dB) of 2.7 GHz at a thickness of 1.8 mm. The excellent EM wave dissipation ability of RHPC/Fe and RHPC/Co can be attributed to the good EM impedance matching condition, quarter-wavelength cancellation and strong EM wave attenuation inside the absorber. Consequently, considering the EM wave absorption performance, the RHPC/Fe and RHPC/Co synthesized in this work are promising candidates in the field of EM wave attenuation.