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

Abstract

• Fe 3 O 4 @N-doped residual carbon composites were successfully fabricated. • The effective absorption bandwidth reached 4.16 GHz at 1.5 mm thickness. • Strong absorption, broad bandwidth and thin thickness were simultaneously achieved. • The reasons for high-performance microwave absorption are studied. The electromagnetic wave absorption (EMWA) performance of materials is affected by their dielectric and magnetic properties. Here, ferroferric oxide@N-doped residual carbon (Fe 3 O 4 @NRC) composites were successfully fabricated by decorating NRC with Fe 3 O 4 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 Fe 3 O 4 @NRC composites were thoroughly tested via analytical techniques. Notably, both the Fe 3 O 4 @NRC-2 and Fe 3 O 4 @NRC-3 composites exhibited superior EMWA capacity. When 40% mass was added, the value of minimal reflection loss ( RL min ) for Fe 3 O 4 @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 RL min was achieved. The results demonstrated that the EMWA performance of the composites could be adjusted by controlling the content of Fe 3 O 4 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. The effective absorption bandwidth of 4.16 GHz and minimal reflection loss of −37.3 dB at 1.5 mm thickness were achieved for the Fe3O4@NRC composites. The dielectric loss originated from dipole plarization and interfacial polarization, conduction loss were beneficial to the enhancement of optimal impedance matching and suitable attenuation capacity. This work can provide a significant guidance for the resource utilization of coal gasification fine slag in the field of electromagnetic wave absorption.