Magnetic-Dielectric Synergistic Cladding of Hollow Fly Ash for Excellent Microwave Absorption Performance

The efficient microwave attenuation mechanism is a primary challenge in the development of microwave absorbing materials (MAMs). The rational design of microstructure and the selection of components are important factors in achieving excellent microwave absorption performance. A dual-coated-layer modified fly ash (FA) core-shell structure microspheres FA@CoNi@PPy with an outer layer of polypyrrole (PPy) and an inner layer of CoNi particles was prepared by a simple surface deposition method. By effectively combining the CoNi metal layer and conductive polymer PPy on hollow FA, the impedance matching performance has been effectively improved, and the microwave absorption efficiency has been notably improved as well. The results indicate that the minimum reflection loss (RL_min) can reach as low as -48.40 dB, and the maximum effective absorption bandwidth (EAB_max) of 6.48 GHz (RL < -10 dB) has been achieved, covering the whole Ku band, with a thickness of 2.25 mm. The enhanced absorption performance of FA@CoNi@PPy is closely related to the magnetic-electric synergy effect, multiple interface polarizations, Debye relaxation processes, electromagnetic resonance, and internal multiple scattering mechanisms among various components. This work innovatively combines magnetic and dielectric properties onto specific microstructure within a single material system, providing a novel perspective for the design of high-performance MAMs.