Four-Layer Cellulose-Based Composite Films with High Thermal Conductivity and Electromagnetic Absorption Shielding via Vacuum Filtration and Subsequent Spin-Coating

Abstract Driven by the trend toward high integration and power density of modern electronic devices, heat accumulation and electromagnetic interference (EMI) have emerged as pressing issues. In this work, an asymmetric four-layer cellulose-based composite film was fabricated via vacuum filtration and spin-coating. The film is structured with bilateral BN/CMC thermal conductive insulating layers, a middle MXene/CMC conductive reflective layer, and an FeSiAl/CMC magnetic absorption layer, combining high thermal conductivity with absorption-dominated EMI shielding performance. Spin-coating parameters and FeSiAl loading were found to greatly affect film performance. Raising the spin speed from 1500 to 2500 rpm optimizes the orientation of BN and FeSiAl flakes. With FeSiAl content increasing from 100 to 300 phr, thermal conductivity and EMI shielding effectiveness (SE) increase continuously. The optimal performance is obtained at 2000 rpm, 10 s spin time with the addition of 300 phr FeSiAl. The corresponding film exhibits an in-plane thermal conductivity of 10.51 W·m–1·K–1, an EMI SE of 56.2 dB, and an average absorption coefficient of 0.52, well meeting the criteria for absorption-dominated EMI shielding. The film also shows excellent flame retardancy, electrical insulation, and mechanical properties, rendering it highly versatile, thereby providing a strategy for developing flexible thermally conductive EMI shielding composites.