N-doped residual carbon from coal gasification fine slag decorated with Fe3O4 nanoparticles for electromagnetic wave absorption

The electromagnetic wave absorption (EMWA) performance of materials is affected by their dielectric and magnetic properties. Here, ferroferric [email protected] residual carbon (Fe3O4@NRC) composites were successfully fabricated by decorating NRC with Fe3O4 nanoparticles via a facile chemical co-precipitation method. The RC was obtained through acid treatment to remove the inorganic minerals in coal gasification fine slag. The structure, composition, thermal stability, morphology, and related EM parameters of the as-fabricated Fe3O4@NRC composites were thoroughly tested via analytical techniques. Notably, both the Fe3O4@NRC-2 and Fe3O4@NRC-3 composites exhibited superior EMWA capacity. When 40% mass was added, the value of minimal reflection loss (RLmin) for Fe3O4@NRC-2 was −37.4 dB, and the effective absorption bandwidth (EAB, RL ≤ −10 dB) reached 4.16 GHz (13.84–18.00 GHz) at a thickness of 1.5 mm. Besides, the value of impedance matching was 1.00 as the RLmin was achieved. The results demonstrated that the EMWA performance of the composites could be adjusted by controlling the content of Fe3O4 nanoparticles. The magnetic/carbon composites exhibited superior EMWA performance, thus promoting the resource utilization of residual carbon in coal gasification fine slag from coal gasification.