Polyaniline-regulated HCM@NZF@PANI composites with enhanced dielectric loss for broadband microwave absorption

Achieving lightweight microwave absorbers with strong attenuation, broad bandwidth and small matching thickness remains challenging for electromagnetic protection. Hollow ceramic microspheres (HCMs) are attractive lightweight supports owing to their low density and hollow structure, but their limited intrinsic dielectric loss and negligible magnetic response restrict microwave attenuation. Although binary hollow microsphere/ferrite or hollow microsphere/conductive-polymer systems can improve electromagnetic response, simultaneously balancing attenuation and impedance matching remains difficult. Herein, hierarchical HCM@NZF@PANI ternary absorbers were constructed by sequentially anchoring Ni–Zn ferrite (NZF) particles and depositing polyaniline (PANI) onto aminated HCMs. In this architecture, HCMs act as lightweight frameworks and scattering centers, NZF introduces auxiliary magnetic response and magnetic/dielectric interfaces, and PANI serves as a dielectric regulation layer. Structural characterizations confirmed rough core–shell microspheres with abundant multiphase interfaces. Increasing PANI content enhanced complex permittivity, dielectric loss tangent and attenuation constant while maintaining favorable impedance matching. HNP-60 delivered the optimal absorption performance, with a minimum reflection loss of −47.55 dB at 16.24 GHz at 1.5 mm and an effective absorption bandwidth of 5.52 GHz covering 11.76–17.28 GHz at 1.7 mm. The enhanced performance arises from multiple scattering, PANI-derived conductive loss, dipole polarization, Maxwell–Wagner interfacial polarization and auxiliary magnetic response. Radar cross-section simulation further verified the echo suppression capability of the coating, demonstrating a feasible interfacial regulation strategy for lightweight, thin and broadband ceramic-based absorbers.