Multiple reflection and scattering effects of the lotus seedpod-based activated carbon decorated with Co₃O₄ microwave absorbent

The lotus seedpod-based activated carbon (LSAC) is derived from pyrolysis of lotus seedpod as biomass carbon precursor, and Co₃O₄ is then deposited to LSAC by oxidation-precipitation and crystallization process of Co ions from Co(NO₃)₂ solution. The Co₃O₄ particles uniformly decorate on the surface and/or the inner channels of LSAC. The optimal reflection loss (RL) value of LSAC/Co₃O₄-paraffin wax (PW) composite reaches −39.8 dB, and the bandwidth for RL below −10 dB and −20 dB are 10.3 and 3.0 GHz, respectively, much better than that of LSAC-PW composite for the higher magnetic loss. The addition of Co₃O₄ particles in LSAC-PW composite significantly enhance the RL values in various thicknesses. The channels of the LSAC and decorated Co₃O₄ can improve the abilities of multiple scattering, dipole polarization, interface polarization and magnetic loss. This composite provides a promising method to construct high performance absorbers by using biomass carbon to tune the dielectric properties of the ferromagnetic materials.