ZnFe2O4 nanospheres decorated residual carbon from coal gasification fine slag as an ultra-thin microwave absorber

Microwave absorbers are commonly utilized in radar stealth and anti-stealth to improve battlefield penetration rates and equipment safety. The ZnFe2O4/residual carbon (ZFO/RC) nanocomposites were fabricated via a hydrothermal synthesis method. The RC was extracted by acid treatment of coal gasification fine slag (CGFS) to eliminate inorganic minerals. The crystal structure, micro-morphology, chemical compositions, and corresponding electromagnetic characteristics of the as-fabricated ZFO/RC composites were investigated. The synthesized nano-micro size ZFO/RC demonstrated excellent electromagnetic wave absorption (EMWA) property. The ZFO/RC-3 composites had exceptional EMWA performance with a minimum reflection loss (RLmin) of −46.33 dB at 13.04 GHz and a maximum effective absorption bandwidth (EAB, RL ≤ -10 dB) that reached 2.96 GHz (11.76–14.72 GHz) at a thickness of 1.48 mm. The EMWA ability of ZFO/RC can be adjusted by controlling the filler loading composites. Benefit from interface polarization, superb impedance matching of the special heterostructure, and conductive loss, the ZFO/RC composites can absorb 99 % of the waves passing through it under ideal conditions. The CST simulation evidently demonstrated that the ZFO/RC-3 composites can notably reduce the radar cross section reduction value under the actual conditions. These composites can serve as possible ultra-thin microwave absorbers with excellent EMWA capability, thus advancing solid waste utilization of residual carbon from entrained-flow CGFS.