Improving the electromagnetic wave (EMW) absorption performance of continuous SiC fibers is of great significance for the development of structure-function integrated composites. Doping magnetic metal elements into SiC fibers can effectively improve their dielectric/magnetic loss, which is expected to produce SiC fibers with wide frequency EMW absorption. At present, introducing metal into continuous SiC fibers generally has the disadvantages of (1) low metal content and (2) weak EMW absorption ability. In this paper, vinylferrocene (VF) with monofunctional groups was selected as the iron source to introduce Fe atoms into polycarbosilane (PCS) through chemical modification without changes in the molecular framework of PCS, which is beneficial for the melt spinning of the precursors. A series of continuous Fe-SiC fibers were prepared by polymer-derived ceramic approach, and their composition, structure and EMW properties were systematically studied. Besides SiC crystallization, the turbostratic carbon, core–shell structures of Fe₅Si₃@C and Fe₃Si@C were identified for the continuous Fe-SiC fibers. It is worth noting that in the present work, (1) the introduction of Fe catalyzes the formation of turbostratic carbon, which can be observed at a low temperature of 900 °C and (2) the highest Fe content (7.70 wt%) was obtained among all the reported continuous Fe-SiC fibers. The unique microstructure of final Fe-SiC fibers demonstrated outstanding EMW absorbing performance. For the Fe-SiC-2-900 °C fiber, the minimum reflection loss (RL_min) reached −54.63 dB at 10.2 GHz. By adjusting the thickness, the effective absorption bandwidth of Fe-SiC-3-1200 °C can almost cover the X-band. The results indicate that the presented continuous Fe-SiC fibers exhibit excellent EMW absorbing performance.

中文翻译：

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高铁含量 SiC 纤维的制备、微观结构演变和优异的 EMW 吸收性能

提高连续碳化硅纤维的电磁波（EMW）吸收性能对于结构功能一体化复合材料的开发具有重要意义。在碳化硅纤维中掺杂磁性金属元素可以有效改善其介电/磁损耗，有望生产出具有宽频率电磁波吸收的碳化硅纤维。目前，在连续碳化硅纤维中引入金属普遍存在（1）金属含量低和（2）EMW吸收能力弱的缺点。本文选择具有单官能团的乙烯基二茂铁（VF）作为铁源，通过化学改性将 Fe 原子引入聚碳硅烷（PCS）中，PCS 的分子骨架不发生变化，有利于前驱体的熔体纺丝。采用聚合物衍生陶瓷方法制备了一系列连续的Fe-SiC纤维，并对其成分、结构和电磁波性能进行了系统研究。除了 SiC 结晶外，Fe 的乱层碳、核壳结构₅ Si ₃ @C 和 Fe ₃ Si@C 被确定为连续的 Fe-SiC 纤维。值得注意的是，在目前的工作中，（1）Fe 的引入催化了湍层碳的形成，这可以在 900 °C 的低温下观察到，（2）Fe 含量最高（7.70 wt%）是在所有报道的连续 Fe-SiC 纤维中获得。最终 Fe-SiC 纤维的独特微观结构表现出出色的 EMW 吸收性能。对于 Fe-SiC-2-900 °C 光纤，最小反射损耗 (RL _min) 在 10.2 GHz 时达到 −54.63 dB。通过调整厚度，Fe-SiC-3-1200℃的有效吸收带宽几乎可以覆盖X波段。结果表明，所提出的连续 Fe-SiC 纤维表现出优异的 EMW 吸收性能。