1成果简介

　　为同时解决电子设备中的电磁干扰与热量积聚两大关键问题，本文，浙江师范大学王晓娟、童国秀 教授团队在《Carbon》期刊发表名为“Constructing dual networks in tissue-paper-derived carbon nanofiber/Co@C composites toward exceptional microwave absorption and heat conduction”的论文，研究通过简便的浸渍-退火工艺，首次合成了具有双网络结构的卫生纸衍生的碳纤维（CF）@Co@C复合材料，作为先进双功能填料。通过将碳纤维与Co@C泡沫结合，可构建双网络结构、多重异质界面、磁电双损耗机制及电子-声子双热载流子体系，从而增强电磁波吸收与热传导性能。
　　得益于增强的欧姆损耗、极化损耗及多重磁共振效应，实验表明含0.005摩尔Co(NO₃)₂·6H₂O的CF@Co@C复合材料展现出高等效吸收带宽密度(EABW/d=3.55 GHz/mm)与强吸收能力(-50.09 dB)，显著优于碳纤维及其他吸收材料。同时，CF@Co@C/TPU复合薄膜在10 wt%低负载量下展现出高导热性（5.059∼6.544 W/(m·K)），其最高导热值分别是纯TPU薄膜和二维碳纤维/TPU薄膜的1.85倍与1.43倍。此外，通过密度态（DOS）与极化密度态（PDOS）的理论分析揭示了电磁波吸收与热传导的增强机制。面心立方-Co/C、六方密堆积-Co/C与面心立方-Co/六方密堆积-Co之间的多重异质界面，为额外电偶极子提供了内置电场，从而增强了材料的微波吸收能力。二维碳纤维与Co@C泡沫的结合实现了电子与多频声子的协同传热，从而提升了材料导热性能。总体而言，本研究为开发具有磁电双损耗与电子声子双热载体的先进双网络复合材料提供了新颖简易的策略，可应用于电子行业的电磁防护与热管理领域。
　　2图文导读 

　　图1. (a1–a3) The synthesis process of CF@Co@C composites. Characterization of the composites formed at diverse Co(NO3)2·6H2O masses (n, mol): (b1–f1, b2–f2, b3–f3) SEM images, (g1–g4, h1–h5) elemental mapping images, (i1–i3) TEM images, and (i4) SAED pattern. (b1–b3, g1–g4) 0 mol, (c1–c3) 0.0025 mol, (d1–d3, h1–h5, i1–i4) 0.005 mol, (e1–e3) 0.01 mol, and (f1–f3) 0.02 mol.

　　图2. (a) EDX spectra, (b) elemental contents, (c1) survey XPS spectrum and the detailed XPS spectrum of (c2) C 1s, (c3) O 1s, and (c4) Co 2p of the CF@Co@C composites formed at diverse n.

　　图3. (a) XRD patterns, (b1–c1) lattice structures and (b2–c2) DOS of FCC phase Co and HCP phase Co. (d) variations in mean crystallite size (D) and internal stress (γ), and (e) Raman spectra of the CF@Co@C composites formed at diverse n.

　　图4. Texture analysis of the CF@Co@C composites formed at diverse n: (a–e) N2 adsorptive/desorptive isotherms (insets are pore diameter distribution curves) and (f) specific surface area (SBET) and pore diameter.

　　图6. (a) EABW/d, γ, AC%, Co/C, HCP/FCC, SBET, and P (pore size obtained from the BET test) as a function of n. (b) Attenuation modulus, (c) matching modulus (Z), (d) Ohmic loss (εc″), (e) polarization loss (εp″), (f1–f2) Cole–Cole curves (ε′ versus εp″). Microwave absorption mechanism: (g1) Interfacial polarization revealed by calculated charge differences at the interfaces of FCC-Co/C, HCP-Co/C, and FCC-Co/HCP-Co; (g2) Plasma resonance and defect polarization; (g3) magnetic loss and (g4) magnetic coupling revealed by eddy current loss (μ″(μ')-2f-1, Holograms, and the corresponding magnetic lines for the flux distribution maps of CF@Co@C; (g5) Ohmic loss and multi-EMW scattering in dual networks.

　　图7. Characterization and thermal performance of TPU films supported by the CF@Co@C composites: (a1) Photographs, (a2) stress-strain curves and (a3) cyclic stress-strain curves at 30% strain with 20 stretching–release cycles. (b) element distribution images, and heat conductivity (HC) as functions of (c1) filling ratio and (c2)n. (d) A HC comparison[21],[44],[45],[46],[47],[48],[49],[50],[51],[52],[53],[54],[55],[56],[57],[58]. (e) HC, γ, AC%, Co/C ratio, HCP/FCC ratio, SBET, and σ as a function of n. (f) The PDOS of C, HCP-Co, and FCC-Co. Heat transmission mechanism: (g1) phonon scattering in the CF@Co@C composites; (g2) electron and phonon co-transmission in dual networks. (h1–h4) Infrared heat imaging photos and the temperature versus time curves.
　　3小结
　　通过简便的浸渍-退火工艺，成功制备了双网络CF@Co@C复合材料，实现了微波吸收系数(MWAC)与热传导的协同增强。通过调控n值，有效调控了材料缺陷、取向及多异质界面特性。相较于纯二维碳纤维，将Co@C泡沫引入二维碳纤维网络后，因衰减与匹配性能提升，实现了宽带强吸收特性。当n=0.005 mol时获得最佳微波吸收特性，表现出高达3.55 GHz/mm的等效吸收带宽密度(EABW/d)和相对较低的最小反射损耗(RLmin)为-50.09 dB。此外，含10 wt%填料的CF@Co@C/TPU薄膜展现出约6.474 W/(m·K)的高导热性，较纯TPU薄膜和二维碳纤维/TPU薄膜分别提升83%和41%。通过密度态（DOS）、偏密度态（PDOS）及耦合态（CST）理论计算揭示了CF@Co@C复合材料的微波吸收与热传导机制。其增强的热导率和微波吸收系数归功于双网络结构、磁电双重损耗、多重异质界面及电子-声子双热载流子特性。这些特征不仅产生多重散射、多重磁共振及界面极化效应，更显著加速了热传导过程。综上，本研究为构建兼具卓越电磁波吸收与热传导性能的高性能双功能双网络材料提供了明确指导。
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