Synthesis of hollow ZnFe2O4/residual carbon from coal gasification fine slag composites for multiband electromagnetic wave absorption

Electromagnetic wave (EMW) absorbers play an essential role in equipment anti-interference and human health protection. Herein, hollow ZnFe2O4/residual carbon (RC) composites were prepared using a simple hydrothermal method. The absorbing properties of the hollow ZnFe2O4/RC composites can be tuned by adjusting the RC amount. The composites show an apparent double-peak EMW absorption capability in S, C, and Ku bands. The minimum reflection loss (RL) is − 38.99 dB with 4.0 mm thickness, and the effective absorption bandwidth (RL ≤ −10 dB) is 3.20 GHz with 4.1 mm thickness. The hollow ZnFe2O4/RC composites are anticipated to be promising EMW absorbers due to their strong magnetic loss, good impedance match, optimized electrical properties, and efficient microstructure. This work demonstrates the viability of creating highly effective microwave absorbing materials with multiband EMW absorption capacity, which can be utilized to create future EMW absorbers.