Ultrahigh concentration and stable dispersion of graphite nanosheet paste as composite nanofillers for thermal management and electromagnetic shielding

Abstract Graphene provides thermal and electrical conductivity to polymer composites, which significantly improves the properties of heat dissipation and electromagnetic interference (EMI) shielding. However, due to the low concentration and stability of graphene dispersion, its industrial application is greatly hindered. In this work, graphite nanosheet (GNS) paste was successfully fabricated from the expanded graphite through wet ball‐milling technology in a one pot process. The ultrahigh GNS concentration is up to 59.4 mg mL−1, and exhibits high stability for 6 months. Furthermore, the average thickness of GNS is less than 10 layers. The GNS paste could mix uniformly with polymer dispersion to obtain large‐area and flexible films by the doctor‐blading process. The composites containing 80 wt% GNS exhibit layered structure, leading to high thermal conductivities with an in‐plane value of 71.18 W m−1 K, far surpassing the pristine polymer material (0.19 W m−1 K), and reveal an efficient total electromagnetic shielding (SEtot≈ 45 dB in the range of 8.2 to 12.4 GHz). This work provides a direct route to prepare composites with high thermal conductivity and EMI shielding from ultrahigh concentration GNS paste