Excellent electromagnetic wave absorption and high thermal conductivity enabled by core-shell graphene@diamond heterostructures

Highly integrated and miniaturized electronic systems impose concurrent demands on efficient thermal management and electromagnetic interference suppression. Diamond possesses ultrahigh thermal conductivity, yet its poor impedance matching and limited loss mechanisms result in insufficient electromagnetic wave absorption. Here, we report a structural regulation strategy based on complementary coupling of carbon allotropes to address this issue. A vertically aligned graphene shell is in-situ constructed on artificial diamond particles via liquid-metal-assisted annealing, forming a core-shell graphene@diamond (G@D) heterostructure with tunable interfacial hybridization. The structural evolution from discontinuous graphene domains to a continuous shell establishes a continuous sp² conductive network and heterogeneous interfaces. As a result, both impedance matching and dielectric loss are optimized simultaneously. The optimized material exhibits a minimum reflection loss of −42.89 dB and an effective absorption bandwidth of 4.43 GHz. Mechanistically, the excellent performance is mainly attributed to the synergistic effect of conductive loss, interface polarization and multiple scattering, which is determined by the evolution of interface continuity and the modulation of sp²/sp³ hybridization ratio. Meanwhile, the formation of continuous interfacial thermal pathways effectively suppresses phonon scattering, leading to a high thermal conductivity of 25.99 W m⁻¹ K⁻¹ in the polymer matrix (7.5 times that of the physically mixed system). This work provides a general paradigm for integrating electromagnetic attenuation and thermal transport within a single filler system, offering new opportunities for multifunctional materials in high-power electronics and advanced packaging.