Shape Anisotropic Chain‐Like CoNi/Polydimethylsiloxane Composite Films with Excellent Low‐Frequency Microwave Absorption and High Thermal Conductivity

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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 (RL min ) 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 RL min 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 RL min of −9.5 dB. Meantime, the in‐plane and inter‐plane thermal conductivity coefficients of 18 vol% chain‐like CoNi/PDMS composite films are 2.05 and 0.61 W m −1 K −1 , about 1.5 times higher than 18 vol% spherical CoNi/PDMS composite films (1.36 and 0.42 W m −1 K −1 ), also 220% and 190% higher than pure PDMS (0.64 and 0.21 W m −1 K −1 ). This composite films with low‐frequency microwave absorption and thermal conductivity can broaden applications in 5G communications and flexible electronics.
Funding Information
  • National Natural Science Foundation of China (U21A2093)
  • Key Research and Development Projects of Shaanxi Province (2023‐YBGY‐461)

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