1 成果简介

　　电磁波吸收材料在隐身技术、电磁干扰防护和信息安全领域具有至关重要的战略价值。随着5G/6G通信、物联网和电子设备的快速发展，电磁环境日趋复杂，对吸波材料提出了"薄、轻、宽、强"的极致要求——厚度薄、密度轻、吸收频带超宽、吸收强度大。然而，现有吸波材料普遍面临带宽与厚度/密度的根本矛盾：实现超宽带吸收往往需要较大的厚度或较高的面密度，难以满足航空航天和可穿戴领域对轻量化的苛刻需求。碳纳米管（CNTs）凭借优异的介电损耗能力、极高比表面积和可调导电性，是极具前景的轻质吸波填料。然而，单一CNT填料的介电常数往往偏高，导致严重的阻抗失配——大部分电磁波在材料表面被反射而非进入内部被吸收。如何调控CNT复合材料的介电色散特性，实现宽频阻抗匹配，是突破带宽瓶颈的关键。芳纶纤维（Aramid Fiber）是一种高性能有机纤维，具有高强高模、耐高温、低密度等优异特性，广泛用于航空航天复合材料。芳纶纤维本身介电常数较低，且可形成低密度的纸基网络结构。将CNT与芳纶纤维复合，有望通过介电色散效应——即不同组分介电常数的梯度分布——实现宽频阻抗匹配和超宽带吸收。 

　　本文，北京大学高鑫 研究员、华南理工大学王宜 教授等在《Nano Lett》期刊发表名为“Carbon Nanotube-Aramid Fiber Enabled Dielectric Dispersion in Paper Composites for Ultrabroadband Lightweight Absorbers”的论文，该研究创新性地提出了CNT-芳纶纤维介电色散策略，通过在芳纶纤维纸基网络中梯度分布CNT，实现介电常数的空间色散调控，构筑了超宽带轻质纸基吸波复合材料。 

　　该工作的核心创新在于：(1) 介电色散设计——利用CNT与芳纶纤维的介电常数差异，通过梯度分布实现介电常数的空间色散，逐层匹配自由空间阻抗，大幅拓宽吸收频带；(2) 纸基轻质结构——芳纶纤维纸作为骨架，提供超低面密度和柔性可加工性；(3) CNT-芳纶协同——CNT提供介电损耗，芳纶纤维调控阻抗匹配和降低密度，二者协同实现超宽带强吸收；(4) 航空级验证——与中航工业合作，验证了材料在航空复合材料结构中的集成可行性。 

　　2图文导读

　　图1. SWCNT-coated aramid fiber-enhanced paper and its application in broadband microwave absorbers. (a) Multiscale structure of the microwave absorber and its electromagnetic wave response mechanism. (b) Photographs of the SAP fabricated at an engineering scale. (c) Reflectance of the SAF-based absorber. (d) Performance comparison with other materials, demonstrating its significant advantages 

　　图2. Multiscale simulation-driven optimization of microwave absorber performance via fiber conductivity and length control. (a) Schematic illustrations of the design strategy for SAFs, SAPs, and the resulting microwave absorbers. (b) Average electric field intensity of single fibers (length = 6 mm) with varying fiber conductivities as a function of microwave frequency. (c) Real part of the complex permittivity for random networks composed of single fibers (length = 6 mm) with different conductivities as a function of frequency (all fiber networks contain 3 wt % fibers). (d) Simulated reflectivity of microwave absorbers containing single-fiber (length = 6 mm) networks with different conductivities. (e) Average electric field intensity of single fibers (σ = 104 S/m) with different lengths as a function of microwave frequency. (f) Real part of the complex permittivity for random fiber networks composed of single fibers (σ = 104 S/m) with varying lengths across the microwave frequency range (all fiber networks contain 3 wt % fibers). (g) Simulated reflectivity of the microwave absorber for single-fiber networks with different lengths (σ = 104 S/m). 

　　图3. Fabrication and characterization of SAFs. (a) Schematic illustration of the continuous wet-processing method used to fabricate SAFs. (b) Optical images showing pristine aramid fibers (AF) and SAFs after multiple SWCNT coating cycles. (c) SEM image of SAF-3, revealing a dense and uniform SWCNT network on the fiber surface. (d) SWCNT mass fraction on SAFs as a function of dip-coating cycles. (e) Electrical conductivity of SAFs increases with the number of coating cycles. (f) Raman spectra of AF, pristine SWCNTs, and SAFs, showing characteristic D, G, and 2D peaks in SAFs, confirming the stable attachment of SWCNTs to the fiber surface. 

　　图4. Electromagnetic property tuning of SAPs with different SAF lengths. (a) Schematic illustration of SAP fabrication via wet papermaking. (b) Optical micrographs showing the uniform dispersion of SAFs with varying lengths in the aramid paper network. (c–e) Frequency-dependent complex permittivity of SAPs with different SAF lengths: (c) real part (ε′), (d) imaginary part (ε″), and (e) dielectric loss tangent (tan δε). (f) Volumetric electrical conductivity as a function of SAF length. (g) Power coefficients (reflection, absorption, and transmission) at 2 GHz. (h) Frequency-dependent electromagnetic attenuation coefficient. 

　　图5. Structural design and microwave absorption performance of SAP-based Jaumann absorbers. (a) Schematic illustration of the SAP-based Jaumann absorber. (b–e) Simulated electromagnetic response of absorbers based on SAPs with different SAF lengths: (b) reflectivity, (c) effective absorption bandwidth (EAB), (d) impedance evolution, and (e) minimum reflectivity in the S band. (f) Volumetric power loss density distribution of multilayer SAP at 2 GHz. (g) Schematic of the gradient absorber composed of three SAP layers (SAP-6 mm, SAP-12 mm, and SAP-9 mm). (h) Experimental setup for reflectivity measurements of the gradient absorber. (i, j) Simulated and measured performance of the gradient absorber: (i) reflectivity curves and (j) effective absorption bandwidth (2–18 GHz). (k) Schematic diagram of radar cross section (RCS) calculation. (l) RCS reduction of the gradient absorber in the S band. 

　　3 小结     

　　综上所述，该工作创新性地提出了CNT-芳纶纤维介电色散策略，通过在芳纶纤维纸基网络中梯度分布CNT，实现了介电常数的空间色散调控，构筑了超宽带轻质纸基吸波复合材料。核心发现与贡献包括： 1. 介电色散新概念——利用CNT与芳纶纤维的介电常数差异，梯度分布实现介电常数空间色散，逐层匹配自由空间阻抗，从根本上解决了宽频阻抗匹配难题； 2. 超宽带轻质突破——CNT-芳纶纸基复合材料的有效吸收带宽覆盖数GHz至数十GHz超宽频段，面密度仅数十至数百g m⁻²，实现了带宽与轻量化的协同突破； 3. 纸基结构优势——芳纶纤维纸提供超低面密度、柔性可加工和大规模生产可行性，避免了传统吸波材料的厚重刚性局限； 4. 航空级验证——与中航工业合作，验证了材料在航空结构-功能一体化复合材料中的集成可行性，推动了从实验室到装备的应用转化。  该工作为超宽带轻质吸波材料设计提供了介电色散新范式，"CNT-芳纶梯度介电色散+纸基轻质结构"策略可拓展至MXene、石墨烯等其他二维材料体系，在隐身技术、电磁防护和6G通信领域具有广阔应用前景。 

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