Pore-preserving BN-coated rGO composites for heat spreading and EMI shielding

The increasing use of flexible and wearable electronics requires thermal management materials that can spread localized heat while maintaining mechanical stability and electromagnetic interference (EMI) shielding performance. In this study, a flexible multifunctional heat spreader was fabricated using a reduced graphene oxide aerogel-based composite structure. First, a reduced graphene oxide aerogel was used as a continuous conductive framework for EMI shielding. To stabilize this fragile framework and improve heat transport, a thermoplastic polyurethane/boron nitride coating layer was formed on the aerogel surface without fully blocking the internal pores. The open pores of the coated framework were then filled with a hybrid filler composed of polydopamine-treated boron nitride and reduced graphene oxide aerogel flakes. In this hybrid filler, r educed graphene oxide aerogel flakes provided additional electrically conductive networks for EMI shielding, while polydopamine-treated boron nitride supplied thermally conductive filler components for heat spreading. The polydopamine layer improved the contact between boron nitride and reduced graphene oxide-based components, supporting the formation of a connected filler network. After hot pressing, the optimized composite exhibited an in-plane thermal conductivity of 7.35 W m⁻¹ K⁻¹ and a through-plane thermal conductivity of 1.28 W m⁻¹ K⁻¹. It also achieved an EMI shielding effectiveness of 41.2 dB in the X-band range, along with a tensile strength of 17.5 MPa. These results show that the combined aerogel framework, coating layer, and pore-filling hybrid filler structure is effective for flexible heat spreaders requiring heat dissipation, EMI shielding, and mechanical stability.