Multiscale understanding of structure-dependent loss mechanisms for tunable and efficient electromagnetic wave absorption

MXene (Ti3C2Tx), an extensively investigated 2D material, has considerable potential for applications in electromagnetic wave absorption (EWA). To further enhance the EWA performance of MXene-based materials, magnetic loss components are often incorporated to improve impedance matching, but remain extremely challenging in revealing the composition-morphology-performance correlation. In this work, two types of materials with the same composition were obtained through a facile two-step hydrothermal method, with the one featured Fe3O4 hollow microspheres and large diameter (FCMX), while the other one was composed of nanoscale magnetic particles without a hollow architecture (FCMXR). The incorporation of a carbon source guarantees the fundamental EWA performance of materials, while distinct design strategies for magnetic loss materials enable tailoring of loss mechanisms. The results reveal that the differing magnetic loss behaviors, dictated by Fe3O4 morphology, directly influenced absorption performance. The hollow-structured FCMX generates enhanced scattering and reflections, with natural and exchange resonance dominating its magnetic loss. FCMXR with smaller magnetic particles contribute to increased interfacial polarization loss, whereas eddy current loss predominates in the magnetic dissipation. Furthermore, benefiting from the synergistic effect of strong magnetic-dielectric loss, and excellent impedance matching, both harvest excellent absorbing performance by optimizing the composition ratio, with a minimum reflection loss (RLmin) of -56.2 dB and an effective absorption bandwidth (EAB) of 7.56 GHz, an RLmin of -52.0 dB and an EAB of 2.55 GHz, respectively. The approach of modulating loss mechanisms in MXene-based composites through tailored synthesis strategies innovatively provides pivotal guidance for developing lightweight wave-absorbing materials with superior performance.