Tailored Multi‐Band Microwave Absorption Performance via Entropy Engineering in Spinel Ferrite/Carbon Nanofiber Composites

The development of electromagnetic microwave absorption (EMA) materials with broad frequency compatibility remains a great challenge, as most of the conventional materials fail to deliver effective microwave attenuation across multiple frequency bands owing to the inferior balance between dielectric and magnetic components. To address this, a novel entropy engineering strategy is presented to fabricate spinel ferrites/carbon composite nanofibers through a combined electrospinning and heat-treatment method as versatile candidates for microwave absorption. Distinct from the traditional spinel oxides, the customized atomic species in MNZCFO/C nanofibers offer superior control over electromagnetic attenuation in specific frequency bands, enabling enhanced multi-band absorption properties. Notably, (Mn_0.05Ni_0.45Zn_0.05Co_0.45)Fe₂O₄/C (MNZCFO/C-3) nanofibers exhibit an optimal reflection loss (RL) value of -54.62 dB with a matching thickness of 2.03 mm and a maximum effective absorption bandwidth (EAB) of 7.28 GHz with low filling ratio of 15 wt.%. Additionally, (Mn_0.25Ni_0.25Zn_0.25Co_0.25)Fe₂O₄/C (MNZCFO/C-2) nanofibers display tunable multi-band absorption characteristics, with effective absorption behaviors shifting across a wide frequency range (3.84-18 GHz). This work presents an innovative strategy for tailoring multi-band EMA materials with flexible and tunable absorption capabilities.