Engineering Interface and Orientation to Construct BNNS/LM Heterostructures with High Thermal Conductivity and Electrical Insulation for Improved Phonon Transport

Abstract The synergistic optimization of high thermal conductivity and electrical insulation is a key challenge in thermal interface materials (TIMs). Conventional ceramic-based composites are inherently incapable of reconciling the contradictory demands of thermal conduction, electrical insulation, and low brittleness, while liquid metal fillers are plagued by poor interfacial compatibility and the risk of leakage. To address these issues, a synergistic strategy integrating molecular interfacial modification and microstructural alignment is developed to construct boron nitride nanosheets (BNNS)/liquid metal (LM) heterostructures. Using H2O2-assisted chlorosulfonic acid intercalation, h-BN is efficiently exfoliated and hydroxylated. Thiomalic acid (TMA) serves as a bridge, achieving uniform LM anchoring on BNNS and preventing LM leakage at a high loading of 42 wt %. A pressure-induced orientation is further applied to vertically align BNNS/LM hybrids, generating preferentially oriented and interconnected thermally conductive networks. The resulting composite exhibits an out-of-plane thermal conductivity of 17.76 W m–1 K–1, while maintaining good electrical insulation with an electrical resistivity exceeding 6 × 109 Ω m. LED tests show that this material reduces LED chip temperature by 16.7 °C compared to a commercial thermal pad. This cross-scale synergistic strategy provides a material design solution that combines high thermal conductivity and electrical safety for thermal management of high-power-density electronic devices.