Simple and efficient synthesis of flexible boron nitride nanosheets/aramid nanofiber composite films with high thermal conductivity and strength

The development of integrated and miniaturized smart electronic devices is accompanied by an increase in the demand for high-strength flexible thermally conductive materials. Existing thermally conductive materials have limitations such as high cost, poor strength, and low efficiency; therefore, there is a demand for preparing flexible and insulating high-strength thermally conductive materials in a convenient and environment-friendly manner. In this study, a bottom-up synthesis of para-aramid nanofibers (ANF) was conducted, and ultra-thin large-scale boron nitride nanosheets (BNNS) were exfoliated by combining lithium-ion intercalation and ball milling. Finally, a composite membrane with a high thermal conductivity and pearl-layered structure was prepared by vacuum-assisted filtration. The BNNS/ANF-30 composite film had excellent mechanical properties, with a tensile strength of up to 40.3 MPa and a thermal conductivity of up to 5.5 W/mK, which are 340 % higher than those of the ANF film. Using the composite film as a substrate can achieve faster heat dissipation, effectively reducing the working temperature of light-emitting diode lights, and has great prospects for applications of thermally conductive materials.