Nowadays, the increasingly serious electromagnetic wave (EMW) pollution and electromagnetic interference (EMI) problems urgently require the development of high-performance electromagnetic attenuation (EMA) materials with tunable green low-reflective EMI shielding and efficient EMW absorption properties. Herein, the pepper wood-like Co₃Fe₇@C nanotubes were constructed by a combined strategy of metal chelates derivatization, self-polymerization, and in-situ carbon reduction, composed of magnetic alloys Co₃Fe₇ nanoparticles (size of 7.5 nm) densely embedded in carbon nanotubes. The EMW absorption and EMI shielding capabilities of the samples with different filling ratios were investigated. Benefiting from the synergistic attenuation mechanism provided by the hollow tubular structure and strong magnetic/dielectric components, the Co₃Fe₇@C nanotubes with protrusions on the surface displayed superior EMW absorption performances at extremely low filling ratio (5 wt.%) with a minimum reflection loss (RL_min) of −107.4 dB and an effective absorption bandwidth (EAB) of 11.6 GHz. Notably, the EMI shielding effectiveness of the optimized sample reaches up to 44.94 dB, while the effective absorption efficiency of the samples with filler loading over 15 wt.% is over 90%. Furthermore, the composite with a coating thickness of 2.0 mm also exhibits an ideal radar cross-sectional (RCS) reduction of 21.2 dB m² at 0°. This study provides unique insights into the design and synthesis of high-efficiency EMA materials, and the Co₃Fe₇@C nanotubes are expected to be practically applicable in complex environments.

中文翻译：

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分层胡椒木状 Co3Fe7@C 纳米管，用于宽带微波吸收和高效电磁干扰屏蔽

如今，日益严重的电磁波 （EMW） 污染和电磁干扰 （EMI） 问题迫切需要开发具有可调绿光低反射 EMI 屏蔽和高效 EMW 吸收特性的高性能电磁衰减 （EMA） 材料。本文采用金属螯合物衍生化、自聚合和原位碳还原的组合策略构建了胡椒木状 Co₃Fe₇@C 纳米管，由密集嵌入碳纳米管中的磁性合金 Co₃Fe₇ 纳米颗粒 （尺寸为 7.5 nm） 组成。研究了不同填充率样品的 EMW 吸收和 EMI 屏蔽能力。得益于空心管状结构和强磁性/介电元件提供的协同衰减机制，表面有突起的 Co₃Fe₇@C 纳米管在极低的填充率 （5 wt.%） 下表现出卓越的 EMW 吸收性能，最小反射损耗 （RL_min） 为 -107.4 dB，有效吸收带宽 （EAB） 为 11.6 GHz。值得注意的是， 优化后样品的 EMI 屏蔽效果高达 44.94 dB，而填料负载量超过 15 wt.% 的样品的有效吸收效率超过 90%。此外，涂层厚度为 2.0 mm 的复合材料在 0° 时也表现出 21.2 dB m² 的理想雷达截面 （RCS） 降低。这项研究为高效 EMA 材料的设计和合成提供了独特的见解，预计 Co₃Fe₇@C 纳米管将实际适用于复杂环境。