Flexible Fe₃Si/SiC ultrathin hybrid fiber mats with designable microwave absorption performance

Flexible Fe₃Si/SiC ultrathin fiber mats have been fabricated by electrospinning and high temperature treatment (1400 °C) using polycarbosilane (PCS) and ferric acetylacetonate (Fe(acac)₃) as precursors. The crystallization degree, flexibility, electrical conductivity, dielectric loss and microwave absorption properties of the hybrid fibers have been dramatically enhanced by the introduction of Fe. Fe₃Si nanoparticles with a diameter around 500 nm are embedded in SiC fibers. As the Fe₃Si content increases from 0 to 6.5 wt%, the related saturation magnetization (M_s) values increase from 0 to 8.4 emu g⁻¹, and the electrical conductivity rises from 7.9 × 10⁻⁸ to 3.1 × 10⁻³ S cm⁻¹. Moreover, the flexibility of Fe₃Si/SiC hybrid fiber mats is greatly improved and remains intact after 500 times 180°-bending testing. Compared with pure SiC fibers, the Fe₃Si/SiC hybrid fibers process higher dielectric and magnetic loss, which would be further advanced as more Fe₃Si phase is introduced. At the optimal Fe₃Si content of 3.8 wt%, the Fe₃Si/SiC fibers/silicon resin composite (5 wt%) exhibits minimal reflection loss (RL) of −22.5 dB at 16.5 GHz and 2.5 mm thickness with a wide effective absorption bandwidth (EAB, RL < −10 dB) of 8.5 GHz. The microwave absorption performance can be further promoted by multi component stacking fiber mat composites which contain both low and high Fe₃Si content layers. Furthermore, the position of the microwave absorption bands can also be simply manipulated by designing the stacking components and structure.