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