Mukun He, Jinwen Hu, Han Yan, Xiao Zhong, Yali Zhang*, Panbo Liu, Jie Kong, Junwei Gu*. Shape Anisotropic Chain-like CoNi/Polydimethylsiloxane Composite Films with Excellent Low-frequency Microwave Absorption and High Thermal Conductivity. Advanced Functional Materials, 2024, 10.1002/adfm.202316691. 2022IF=19.0.（1区材料科学Top期刊）

https://doi.org/10.1002/adfm.202316691

Abstract

The demand for low-frequency microwave absorption materials is becoming more and more urgent. Novel shape anisotropy chain-like CoNi is fabricated using polyvinylpyrrolidone as a shape-directing agent via solvothermal method, which is then mixed with polydimethylsiloxane (PDMS) to prepare corresponding multifunctional chain-like CoNi/PDMS composite films. Shape anisotropy and strong magnetic coupling effect of chain-like CoNi enhance natural resonance and magnetic loss capability. The minimum reflection loss (RLmin) is -50.5 dB and low-frequency effective absorption bandwidth (EAB) is 1.04 GHz (2.64~3.68 GHz) at 3.9 mm for chain-like CoNi. The corresponding 18 vol% chain-like CoNi/PDMS composite films present optimal low-frequency microwave absorption performance with RLmin of -56.7 dB and low-frequency EAB of 1.04 GHz (2.96~4.00 GHz) at 4.1 mm, which is far superior to 18 vol% spherical CoNi/PDMS composite films with RLmin of -9.5 dB. Meantime, the in-plane and inter-planethermal conductivity coefficients of 18 vol% chain-like CoNi/PDMS composite films are 2.05 W/(m·K) and 0.61 W/(m·K), about 1.5 times higher than 18 vol% spherical CoNi/PDMS composite films (1.36 W/(m·K) and 0.42 W/(m·K)), also 220% and 190% higher than pure PDMS (0.64 W/(m·K) and 0.21 W/(m·K)). This composite films with low-frequency microwave absorption and thermal conductivity can broaden applications in 5G communications and flexible electronics.

5G通信和柔性电子技术快速发展带来的低频（S和C波段）电磁干扰和辐射污染问题使其对低频微波吸收材料的需求愈发迫切。本文以聚乙烯吡咯烷酮（PVP）为形状导向剂，通过溶剂热还原法制备形状各向异性的链状CoNi低频微波吸收材料，再将其与聚二甲基硅氧烷（PDMS）基体复合制备多功能CoNi/PDMS复合膜。链状CoNi优异的形状各向异性和强烈的磁耦合效应使其在S和C波段的自然共振增强以及磁损耗能力提升。当链状CoNi低频微波吸收材料厚度为3.9 mm时，其最小反射损耗（RLmin）为-50.5 dB、低频有效吸收带宽（EAB）为1.04 GHz（2.64~3.68 GHz）。当链状CoNi的体积分数为18 vol%时，厚度为4.1 mm的链状CoNi/PDMS复合膜具有最优的低频吸波性能，其RLmin为-56.7 dB、低频EAB为1.04 GHz（2.96~4.00 GHz），远优于相同用量颗粒状CoNi/PDMS复合膜的RLmin（-9.5 dB）。同时，18 vol%链状CoNi/PDMS复合膜的面内导热系数和面间导热系数分别为2.05 W/(m·K)和0.61W/(m·K)，约为18 vol%颗粒状CoNi/PDMS复合膜（1.36 W/(m·K)和0.42 W/(m·K)）的1.5倍，比纯PDMS（0.64 W/(m·K)和0.21 W/(m·K)）高220%和190%。这种兼具优异低频吸波性能和导热性能的多功能PDMS复合膜在5G通讯以及柔性电子设备领域具有广阔的应用前景。

论文亮点

1. 链状CoNi优异的形状各向异性和强烈的磁耦合效应使其在S和C波段的自然共振增强以及磁损耗能力提升。当链状CoNi低频微波吸收材料厚度为3.9 mm时，RLmin为-50.5 dB、低频EAB为1.04 GHz（2.64~3.68 GHz）。

2. 当链状CoNi的体积分数为18 vol%时，厚度为4.1 mm的链状CoNi/PDMS复合膜具有最优的低频吸波性能，其RLmin为-56.7 dB、低频EAB为1.04 GHz（2.96~4.00 GHz），远优于相同用量颗粒状CoNi/PDMS复合膜的RLmin（-9.5 dB）。

3. 18 vol% 链状CoNi/PDMS复合膜的λ∥为2.05 W/(m·K)，分别为18 vol% 颗粒状CoNi/PDMS复合膜（1.36 W/(m·K)）和纯PDMS（0.64 W/(m·K)）的1.5倍和3.2倍。

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