Core–sheath FeCo@vertically aligned carbon fiber arrays for integrated ultrahigh through-plane thermal conductivity and absorption-dominant electromagnetic interference shielding

The coupled problems of heat dissipation and electromagnetic compatibility issues need to be addressed urgently in highly miniaturized and integrated electronic devices. Herein, polydimethylsiloxane (PDMS) composites featuring core-sheath FeCo@vertically aligned carbon fiber (VACF) arrays were prepared via magnetic field-assisted vertical alignment, combined with in situ high-temperature growth and infiltration processes. Within the composite, the VACF arrays provide efficient phonon transport pathways in the through-plane direction, while the magnetic FeCo alloy shells function to isolate the VACF arrays, optimizing impedance matching and enhancing electromagnetic wave absorption loss. By regulating the FeCo alloy content, the through-plane thermal conductivity and total electromagnetic interference (EMI) shielding effectiveness of the composite reached 42.03 W (mK)^-1 and 41.6 dB, respectively, while the reflection effectiveness was only 1.5 dB. This work demonstrates that the FeCo@VACF/PDMS composite can simultaneously achieve ultrahigh through-plane thermal conductivity and absorption-dominant EMI shielding, providing a novel approach for designing high-performance, multifunctional thermal interface materials.