Stable and efficient microwave absorption performances: Design from polydopamine/polyethyleneimine encapsulated FeSiAl flaky composites to frustum of a cone array

The typical microwave absorber usually exhibits the large variations in absorption behavior with absorbing thickness (>10 % for a change in absorber thickness by 10 %). How to obtain broad, strong and stable microwave absorption performances still remains a challenge. In this work, a vertical ball milling technique followed by a co-deposition method in alkaline solution is developed to prepare polydopamine (PDA)/polyethyleneimine (PEI) coated flaky FeSiAl composites, which display broad, strong and stable absorption performances at 2–14 GHz. The obtained PDA/PEI covered FeSiAl flakes exhibited minimal reflection loss (RL) values exceeding −20 dB at 2.5–8.9 mm. When the effective absorption bandwidth (EAB, 4.4–4.88 GHz) and absorption efficiency (RE, 12.11–13.24 dB·GHz/mm) change by 10 %, the corresponding change in absorption thickness can be achieved 28.57 % (2.5–3.5 mm) for EAB and 15.63 % (2.7–3.2 mm) for RE. Phase cancellation and electromagnetic loss contribute to large and stable RL peak intensity and the large loss factor over a wide frequency range lead to broad and stable EAB. Integrated with a macroscale structural design, frustum of a cone structure established by computer simulation technology is beneficial for integrating quarter-wavelength resonance, dielectric loss and magnetic loss, resulting in wide EAB of 12 GHz (covering from 2 to 14 GHz) and strong RL of −62.27 dB at 7.1 GHz. •Flaky FeSiAl@PDA/PEI composites were prepared by a facile two-step method.•The FeSiAl@PDA/PEI flakes exhibited RLm values exceeding −20 dB at 2.5–8.9 mm.•When EAB changes by 10 %, the change in absorption thickness is 28.57 % for EAB.•Phase cancellation and EM loss contribute to large and stable RL peak intensity.•The large loss factor over a wide frequency range lead to broad and stable EAB.