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

Abstract 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 -44.18dB with effective absorption bandwidth (EAB) of 0.17∼0.99GHz for 2mm and a board EAB of 0.53∼2.49GHz for only 1mm. Meanwhile, the maximum RL of T-700 can attain -46.36dB with EAB of 0.49∼1.43GHz and the board EAB of 0.89∼2.81GHz 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.