Porous Fe3O4/C microspheres for efficient broadband electromagnetic wave absorption

Abstract

Porous Fe3O4/C microspheres, which were Fe3O4 nanocrystals (～8 nm) embedded in an open nanostructured carbon network, were successfully synthesized via a facile hydrothermal process. The porous Fe3O4/C microspheres possessed many distinct attributes that facilitate efficient broadband electromagnetic wave absorption (EMWA). EMWs were attenuated through multiple reflections and absorption in the 3D interconnected porous structure of the microspheres; these processes collectively improved the interaction between the EMWs and the absorber. Additionally, the carbon network and embedded Fe3O4 nanoparticles caused significant dielectric losses and magnetic losses, respectively, which also enhanced EMWA. The EMWA characteristics of the microspheres could be precisely tuned via changing the carbon content to achieve optimized impedance matching. Porous Fe3O4/C microspheres with a 71.5 wt% carbon content displayed particularly impressive EMWA properties: a maximum reflection loss (RL) value of − 31.75 across broad band frequencies in the range of 7.76–12.88 GHz (RL < −10 dB) at an absorber thickness of 3.0 mm. These excellent EMWA properties may be attributed to both dielectric loss (carbon) and magnetic loss (Fe3O4). Additionally, the 3D interconnected porous structure of the Fe3O4/C microspheres is especially favorable for impedance matching.