Yolk–shell Fe₃O₄@N-doped carbon nanochains, intended for application as a novel microwave-absorption material, have been constructed by a three-step method. Magnetic-field-induced distillation-precipitation polymerization was used to synthesize nanochains with a one-dimensional (1D) structure. Then, a polypyrrole shell was uniformly applied to the surface of the nanochains through oxidant-directed vapor-phase polymerization, and finally the pyrolysis process was completed. The obtained products were characterized by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and thermogravimetric analyses (TGA) to confirm the compositions. The morphology and microstructure were observed using an optical microscope, scanning electron microscope (SEM), and transmission electron microscope (TEM). The N₂ absorption–desorption isotherms indicate a Brunauer–Emmett–Teller (BET) specific surface area of 74 m²/g and a pore width of 5–30 nm. Investigations of the microwave absorption performance indicate that paraffin-based composites loaded with 20 wt.% yolk–shell Fe₃O₄@N-doped carbon nanochains possess a minimum reflection loss of −63.09 dB (11.91 GHz) and an effective absorption bandwidth of 5.34 GHz at a matching layer thickness of 3.1 mm. In addition, by tailoring the layer thicknesses, the effective absorption frequency bands can be made to cover most of the C, X, and Ku bands. By offering the advantages of stronger absorption, broad absorption bandwidth, low loading, thin layers, and intrinsic light weight, yolk–shell Fe₃O₄@N-doped carbon nanochains will be excellent candidates for practical application to microwave absorption. An analysis of the microwave absorption mechanism reveals that the excellent microwave absorption performance can be explained by the quarter-wavelength cancellation theory, good impedance matching, intense conductive loss, multiple reflections and scatterings, dielectric loss, magnetic loss, and microwave plasma loss.

中文翻译：

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卵黄质Fe 3 O 4 @N掺杂碳纳米链作为高效微波吸收材料的应用

蛋黄壳Fe ₃ O ₄已通过三步法构建了拟用作新型微波吸收材料的N掺杂碳纳米链。磁场诱导的蒸馏-沉淀聚合用于合成具有一维（1D）结构的纳米链。然后，通过氧化剂定向气相聚合将聚吡咯壳均匀地涂覆在纳米链的表面上，最后完成了热解过程。通过X射线衍射（XRD），X射线光电子能谱（XPS）和热重分析（TGA）对所得产物进行表征，以确认组成。使用光学显微镜，扫描电子显微镜（SEM）和透射电子显微镜（TEM）观察形态和微观结构。N ₂吸收-解吸等温线表明，Brunauer-Emmett-Teller（BET）比表面积为74 m ² / g，孔宽度为5-30 nm。对微波吸收性能的研究表明，负载有20 wt。％卵黄壳Fe ₃ O ₄ @N掺杂的碳纳米链的石蜡基复合材料具有-63.09 dB（11.91 GHz）的最小反射损耗和有效的吸收带宽。匹配层厚度为3.1 mm时为5.34 GHz。此外，通过调整层的厚度，可以使有效吸收频带覆盖大多数C，X和Ku频带。通过提供更强的吸收，更宽的吸收带宽，低负荷，薄层和固有的轻质优势，蛋黄壳Fe ₃ O₄ @N掺杂的碳纳米链将是微波吸收实际应用的极佳候选者。对微波吸收机理的分析表明，出色的微波吸收性能可以用四分之一波长抵消理论，良好的阻抗匹配，强烈的导电损耗，多次反射和散射，介电损耗，磁损耗和微波等离子体损耗来解释。