Wheat flour-derived nanoporous carbon@ZnFe2O4 hierarchical composite as an outstanding microwave absorber

Thin and lightweight absorbers with strong absorption capacity are future development directions in the field of electromagnetic wave (EMW) absorption. Based on two microwave-absorbing mechanisms, the three-dimensional (3D) porous carbon materials derived from wheat flour were prepared via pyrolysis carbonization. Then, ZnFe2O4 nanospheres were synthesized and distributed on the surface of carbon skeleton by simple solvothermal method. Results showed that microwave absorption performance was significantly improved due to synergistic effects between ZnFe2O4 nanospheres and carbon matrix. With absorber thickness of only 1.8 mm and low filler loading of 20 wt%, the minimum reflection loss could reach as low as -54.1 dB at 14.1 GHz. The widest effective absorption bandwidth ranged from 9.2 GHz to 15.0 GHz (5.8 GHz) with a thickness of 2.5 mm when the filler loading was 10 wt%, covering 36% of entire measured bandwidth. As an absorber, 3D porous carbon@ZnFe2O4 composite exhibited ideal microwave absorption properties because of synergistic effects between dielectric and magnetic loss, well-matched impedance, interfacial polarization, Debye relaxation process as well as multiple reflection and scattering. Considering excellent EMW absorption performance, the porous carbon@ZnFe2O4 composite fabricated by a simple method can provide a new inspiration for designing structure and composition of lightweight microwave absorbers. (C) 2020 Elsevier Ltd. All rights reserved.