Facile preparation of cotton-derived carbon fibers loaded with hollow Fe₃O₄ and CoFe NPs for significant low-frequency electromagnetic absorption

Nowadays, the fast progress of wireless-communication, radar reconnaissance and electronic technology induces many serious problems such as electromagnetic interference and superfluous electromagnetic radiation. Herein, the cotton-derived CFs@H-Fe₃O₄/CoFe hybrid was prepared via a simple two-stage method of hydrothermal and calcination. For the synergistic effect of magnetic and dielectric loss, the mentioned ternary hybrid possesses outstanding low-frequency microwave absorbing capacity, concretely owing to the better dipole and interface polarization, conduction loss, eddy-current and natural resonance loss, multi-ply scattering and reflection, improved impedance matching etc. The maximal RL values can reach −40.15 dB at 0.71GHz and −40.85 dB at 0.59GHz for the thickness of 3 mm and 3.5 mm respectively, and a board low-frequency EAB of 0.79–2.93GHz can be also achieved at only 1.5 mm thickness. This biomass-based hybrid could be employed as a novel low-frequency microwave absorbent for its good properties and simple preparation process.