Assembled porous Fe3O4@g-C3N4 hybrid nanocomposites with multiple interface polarization for stable microwave absorption

Magnetic/dielectric composites can offer good electromagnetic impendence. However, the strategy for embodying strong absorbing ability and broad effective absorption band simultaneously is a significant challenge. Therefore, assembled porous Fe3O4@g-C3N4 hybrid nanocomposites have been designed and synthesized, in which porous Fe3O4 nanospheres assembled by ~ 3 nm Fe3O4 nanoparticles are surrounded by g-C3N4. The introduction of g-C3N4 improves dielectric loss ability at 2-18 GHz and magnetic loss ability at 2-10 GHz, and enhances attenuation constant, and increases electromagnetic impedance degree. These merits ensure that assembled porous Fe3O4/g-C3N4 hybrid nanocomposites deliver superior microwave absorption performance, such as effective absorption bandwidth, fE, (reflection loss less − 10 dB) exceeding 5 GHz at 2.0-2.3 mm, the maximal fE of 5.76 GHz and minimal reflection loss of at least − 20 dB with thickness ranging from 2.3 to 10.0 mm, avoiding the sensitivity of absorption properties to absorbing layer thickness. Stable microwave absorbing performance originates from multi-interfacial polarization, multi-reflection, enhanced electromagnetic loss capability, and good electromagnetic impedance. Our study offers a new idea for stable microwave absorber at 2-18 GHz.