Integration of impedance-gradient and oriented alignment structure in carbon fiber composites enabling thermal management and microwave absorption

Bifunctional materials possessing both high electrical conductivity and thermal conductivity hold promise for integrating electromagnetic wave (EMW) absorption with thermal management capabilities, thereby addressing signal crosstalk and heat accumulation issues in integrated electronic devices. However, the opposing effects of percolation phenomena on thermal conduction and microwave absorption hinder the integration of these properties. Herein, diospyros cauliflora-shaped CF@PDA@Fe₃O₄ (MCF) was synthesized via a solvothermal method. The introduced heterogeneous interfaces enhance EMW absorption while impeding charge transport between adjacent carbon fibers (CFs), thereby suppressing percolation effects. Subsequently, magnetic-field-induced alignment of MCFs constructs thermally conductive pathways along the temperature gradient direction. By streamlining heat transfer routes and reducing filler-matrix interfaces, thermal conductivity is significantly enhanced. When the mass fraction of MCF is 20 wt.%, the composite achieves an effective absorption bandwidth of 4.2 GHz and a minimal reflection loss of −49.77 dB, while its thermal conductivity increases by 400% compared to pure polydimethylsiloxane (PDMS). This study proposes a synergistic strategy to concurrently enhance thermal conductivity and EMW absorption in composites, offering a new pathway for developing electronic packaging materials with efficient heat dissipation and broadband EMW absorption.