Coal gasification fine slag residual carbon decorated with hollow-spherical Fe3O4 nanoparticles for microwave absorption

Reasonable design and optimization of the dielectric and magnetic properties of materials are important to achieve excellent electromagnetic wave (EMW) absorption capacities. Residual carbon (RC) derived from coal gasification fine slag-loaded hollow-spherical Fe3O4 nanoparticles (Fe3O4 NPs@RC) was synthesized via hydrothermal strategy. The chemical compositions, morphologies, structures, and electromagnetic parameters of the as-prepared RC and Fe3O4 NPs@RC revealed that the phase components (RC and Fe3O4 phases) and microstructure (hollow spherical and micro/nano blocks) were well modified by modulating the content of Fe3O4. Such modifications result in variations in the hierarchical structure, defects, electromagnetic parameters, and EMW absorption performance. The Fe3O4 NPs@RC composites (S1 and S2) exhibited superior EMW absorption capacity. The binary composite with an additive amount of FeCl3·6H2O of 2.66 g (S2) exhibited the minimum reflection loss (RLmin) of −32.6 dB at 2.0 mm and a broad absorption bandwidth (fe, RL less than −10 dB) of 4.64 GHz at a lower thickness value of 1.65 mm under a filler content of 40%. In addition, the ultra-broad fe reached 14.35 GHz, which contained the entire Ku, X, and C bands by easily regulating the thicknesses from 1.5 mm to 5 mm. A possible EMW absorption mechanism was proposed. This study offers an effective strategy for designing novel coal gasification solid waste-based materials for high-performance absorbers.