Excellent Low‐Frequency Microwave Absorption and High Thermal Conductivity in Polydimethylsiloxane Composites Endowed by Hydrangea‐Like CoNi@BN Heterostructure Fillers
Mukun He, Xiao Zhong, Xinghan Lu, Jinwen Hu, Kunpeng Ruan, Hua Guo, Yali Zhang, Yongqiang Guo, Junwei Gu
Abstract
Abstract The advancement of thin, lightweight, and high‐power electronic devices has increasingly exacerbated issues related to electromagnetic interference and heat accumulation. To address these challenges, a spray‐drying‐sintering process is employed to assemble chain‐like CoNi and flake boron nitride (BN) into hydrangea‐like CoNi@BN heterostructure fillers. These fillers are then composited with polydimethylsiloxane (PDMS) to develop CoNi@BN/PDMS composites, which integrate low‐frequency microwave absorption and thermal conductivity. When the volume fraction of CoNi@BN is 44 vol% and the mass ratio of CoNi to BN is 3:1, the CoNi@BN/PDMS composites exhibit optimal performance in both low‐frequency microwave absorption and thermal conductivity. These composites achieve a minimum reflection loss of −49.9 dB and a low‐frequency effective absorption bandwidth of 2.40 GHz (3.92–6.32 GHz) at a thickness of 4.4 mm, fully covering the n79 band (4.4–5.0 GHz) for 5G communications. Meanwhile, the in‐plane thermal conductivity ( λ ∥ ) of the CoNi@BN/PDMS composites is 7.31 W m −1 K −1 , which is ≈11.4 times of the λ ∥ (0.64 W m −1 K −1 ) for pure PDMS, and 32% higher than that of the (CoNi/BN)/PDMS composites (5.52 W m −1 K −1 ) with the same volume fraction of CoNi and BN obtained through direct mixing.