Flexible and insulating silicone rubber composites with sandwich structure for thermal management and electromagnetic interference shielding

High integration development of electronics requires materials possessing excellent thermal conductivity, electromagnetic interference (EMI) shielding, and electrical insulation. In this work, Fe₂O₃ particles are deposited on carbon fibers (CF) and then utilized as fillers (CF@Fe₂O₃) in boron nitride/silicone rubber (BN/SR) to fabricate sandwich structured CF@Fe₂O₃/(BN/SR) composites, herein, BN/SR as top & substrate layer, and CF@Fe₂O₃ as middle layer. Orientation of BN in CF@Fe₂O₃/(BN/SR) composites realizes excellent in-plane thermal conductivity coefficient (λ_∥), and the core-sheath structure of CF@Fe₂O₃ achieves good EMI shielding performance by the “absorption-reflection (transmittance)-reabsorption” process of electromagnetic waves, insulation modification of CF and the sandwich structure strengthen the electrical insulation. When the amount of BN and CF@Fe₂O₃ are 20.6 wt% and 45.5 wt%, respectively, the λ_∥, EMI shielding effectiveness, volume resistance and breakdown strength of CF@Fe₂O₃/(BN/SR) composites reach 3.86 W/(m·K), 37.7 dB, 6.2 × 10¹⁴ Ω cm and 26.8 kV/mm, respectively, which are all higher than those of commonly fabricated CF/(BN/SR) composites with same amount of BN and CF (3.83 W/(m·K), 19.4 dB, 8.6 × 10¹³ Ω cm and 21.4 kV/mm). CF@Fe₂O₃/(BN/SR) composites possess better cooling effect (5.6 °C) than that of commercial silicon grease (QM850) on the testing platform of computer's central processing unit, whose functions are more abundant and have wide application prospects in electronics.