High-performance electromagnetic wave absorbing composites prepared by one-step transformation of Fe3+ mediated egg-box structure of seaweed

Abstract

Composites incorporating ferromagnetic components into a highly porous carbon matrix are promising as electromagnetic wave absorption materials; however, the design of a facile preparation process with scale-up potentiality still remains a practical challenge. Herein, a new kind of three-dimensional (3D) magnetic carbonaceous bead-like (MCB) Fe–SA-X composites has been directly prepared using a Fe³⁺ mediated egg-box structure of renewable sodium alginate as single starting material and a controllable carbonization process; as compared to previous work on carbon-based microwave absorbers, it avoids tedious and time-consuming preparation procedures. It was verified that, according to various characterization results, the atmosphere and temperature for the carbonization of Fe–SA precursors were crucial factors for the formation of the ferromagnetic metal particles and carbon matrix in the porous Fe–SA-X composites. Among the Fe–SA-X composites obtained at different temperatures, Fe–SA-600 obtained at 600 °C exhibited the best performance for electromagnetic wave absorption, for which can be attributed to the synergy of magnetism of Fe₃O₄ nanoparticles and the nano-network of graphitized carbon. The maximum reflection loss (RL) of Fe–SA-600 reached −24 dB, and the effective absorption bandwidth (RL ≤ −10 dB) was 4.80 GHz (13.2–18 GHz) corresponding to an absorber thickness of only 1.5 mm. Such excellent electromagnetic absorption properties could be assigned to the improvement of the impedance match and interfacial polarization and unique porous structures, by which can lead to the effective microwave multi-reflection and scattering. This kind of composite is an attractive candidate for new types of high-performance electromagnetic wave-absorbing materials, meeting for the current requirements of wide-band absorption, high efficiency absorption capability, thin thickness and light weight.