Cactus-like architecture for synergistic microwave absorption and thermal management

As electronic devices evolve toward miniaturization, integration and diversification, developing composites with thermal management and broadband microwave absorption has become critical for addressing electromagnetic compatibility and heat-dissipation challenges. Inspired by the multilevel thorny structure of a cactus, this study proposes a biomimetic 3D network structure via a 'direction-decoupling' design to enhance thermal conductivity and microwave absorption. Boron nitride nanosheets (BNNS) form horizontal thermal pathways, while cobalt-catalysed nitrogen-doped carbon nanotube arrays (Co@NCNTs) are vertically grown in the interlayer for cactus-like heterostructure fillers. Finally, composites are obtained by combining the solid-solid phase-change polyethylene glycol matrix with the directional assembly process. At a mass fraction of 30 wt% for (Co@NCNTs)@BNNS, the composites exhibit the best microwave absorption and thermal conductivity at a thickness of 2.5 mm. The maximum effective absorption bandwidth reaches 6.72 GHz, with in-plane and through-plane thermal conductivity coefficients reaching 2.55 and 0.94 W·m^-1·K^-1, realizing simultaneous improvements in thermal conductivity and microwave-absorption performance. Moreover, density functional theory analysis confirms the interfacial bonding between Co@NCNTs and BNNS systems and verifies the advantages of a unique electronic structure for microwave absorption between Co- and nitrogen-doped carbon nanotubes. This study provides new strategies for integrated thermal-electromagnetic management materials in next-generation high-density electronics.