Novel low-frequency microwave absorber of Sn-Fe-O multiphase compounds combined with Salvia miltiorrhiza Bunge-derived biochar

Superfluous low-frequency microwave radiation becomes a serious problem gradually at current age, herein, the Sn-Fe-O multiphase compounds were combined with novel biochar by using Salvia miltiorrhiza Bunge's leaves as carbon source, which can realize the recycling of this useless Chinese medicinal waste for economy. Also, the influence of preparation process on the final components, structures and properties in composites have been evaluated, the P2 composite possesses the optimal electromagnetic absorbing property i.e. the maximum reflection loss achieves −45.09 dB at 0.48 GHz with efficient absorbing bandwidth of 0.14–1.16 GHz at the matching thickness of 2 mm, moreover, a broad efficient absorbing bandwidth of 0.86–3 GHz can obtained for only 0.71 mm as well. The outstanding absorption of this sample can be ascribed to the synergistic effect of multiple low-frequency absorption mechanisms such as nature resonance, eddy current, conduction and electron hopping, multi-ply interfacial polarization etc., suggesting its superiority for being applied as a new-type low frequency electromagnetic wave absorber for practical use.