Coal gangue as an efficient absorber for X-band applications

Coal mining generates coal gangue (CG), whose poses considerable ecological challenges. Therefore, using CG in the preparation of electromagnetic wave (EMW)-absorbing materials has emerged as a promising approach for its high-value utilization. In this study, CG was dried and then ball milled. The microscopic morphology, element composition, elemental chemical state, and thermal stability of CG were characterized by analyses. The EMW absorption performance of CG in the X-band was tested at filling ratios of 10%, 20%, and 40%. The results showed that CG mainly consisted of SiO₂, Al₂O₃, and C. The CG/paraffin absorber exhibited strong reflection loss (RL) at a relatively thin thickness. When the thickness of the CG/paraffin absorber was 4.0 mm, the minimum RL reached − 50.2 dB at 8.8 GHz. The simulation results of the radar cross-section showed that the absorbing coating can reduce EMW scattering on a perfectly conductive substrate, which renders it promising as an excellent EMW-absorbing material.