Recycling of waste straw in sorghum for preparation of biochar/(Fe,Ni) hybrid aimed at significant electromagnetic absorbing of low-frequency band

Due to the rapid development of wireless electrommunication and electronic techniques in current age, electromagnetic radiation and electromagnetic interference (EMI) have brought serious threat to the normal operation of precision electronic instruments and human health. Herein, the reclaimed straw of sorghum derived biochar/(Fe,Ni) hybrid has been prepared via a facile calcination process. The as-prepared hybrid possesses an outstanding low-frequency electromagnetic absorbing performance i.e. the maximum RL of T-600 can achieve −44.18 dB with effective absorption bandwidth (EAB) of 0.17~0.99 GHz for 2 mm and a board EAB of 0.53~2.49 GHz for only 1 mm. Meanwhile, the maximum RL of T-700 can attain −46.36 dB with EAB of 0.49~1.43 GHz and the board EAB of 0.89~2.81 GHz for the same thickness, which are owing to the cooperative effect of interface polarization, dipole polarization, natural resonance, eddy current and conduction loss, multi-reflection and scatter, better impedance matching and so on. This environmentally-friendly biochar/(Fe,Ni) hybrid can be employed as a novel low-frequency microwave absorbent for its good performance and reclamation of waste straw in sorghum.