Magnetic biomass porous carbon@Co/CoO nanocomposite for highly efficient microwave absorption

The problems caused by electromagnetic pollution have become increasingly prominent. Developing new ma-terials to absorb or reduce electromagnetic radiation has become a hot spot. Herein, a 3D porous biomass porous carbon@Co/CoO nanocomposites were synthesized by solvent heat and high-temperature calcination. The 3D porous structure makes the effective electronic transitions of biomass porous carbon (BPC) form a conductive network, which increases the conductive loss of the material to the electromagnetic wave. The many defects formed between the Co nanoparticles and the BPC provide an abundance of polarization centers, inducing interfacial polarization relaxation and dipole polarization, leading to dielectric losses. Multiple magnetic loss mechanisms, including natural resonance (low frequency), exchange resonance (high frequency) and eddy current loss, as well as good impedance matching characteristics and large attenuation coefficient, enabling BPC@Co/CoO nanocomposites to exhibit excellent EMW absorption properties. As a results, a minimum reflection loss (RLmin) of-43.09 dB is achieved at a frequency of 14 GHz, with a matched thickness of 2.5 mm and an effective absorption bandwidth of 6.75 GHz (11.25-18 GHz).