Three-dimensional (Fe₃O₄/ZnO)@C Double-core@shell porous nanocomposites with enhanced broadband microwave absorption

The synergistic effect of magnetic and dielectric materials makes this kind of composite as an ideal microwave absorber. So far, composite absorbing materials of Fe₃O₄ and carbon have been extensively studied and achieved excellent absorption properties. However, this type of absorber always has the problem of narrow effective absorption band (RL ≤ −10 dB). In this article, we have prepared 3D (Fe₃O₄/ZnO)@C double-core@shell nanocomposites by a clever method. Especially, the electromagnetic parameters and microwave absorption performances of the nanocomposites can be tuned by changing the zinc content. When the molar ratio of Zn to Fe is 1:2, the effective absorption bandwidth of the double-core@shell nanocomposite is 6.4 GHz with 2 mm thickness and 7.11 GHz with 1.9 mm thickness. Besides, when Zn:Fe = 1:1, the double-core@shell nanocomposite achieves a minimum RL value of −40 dB at 15.31 GHz with 2 mm thickness and has a wideband effective absorption of 6.5 GHz and an efficient absorption bandwidth (RL ≤ −20 dB) of 3.4 GHz. The special 3D double-core@shell structure and ingenious introduction of tunable ZnO could improve the microwave absorption performances of the (Fe₃O₄/ZnO)@C nanocomposites, which can be considered as promising absorbing materials.