Sandwiched cellulose nanofiber /boron nitride nanosheet /Ti3C2Tx MXene composite film with high electromagnetic shielding and thermal conductivity yet insulation performance

The rapid development of electronic devices has led to widespread demand and research on electronic packaging materials with electromagnetic shielding and thermal conductivity (TC) properties due to the inevitable issues of the electromagnetic radiation and thermal accumulation. However, there exists a huge challenge to simultaneously achieve high electromagnetic shielding and TC as well as the electrical insulation requirement as electromagnetic shielding predominantly relies on electrical conductivity of materials. Multilayer structure can endow composite materials with a variety of properties. Therefore, in this work, we fabricated sandwiched cellulose nanofiber/boron nitride nanosheet/Ti3C2Tx MXene films by using a simple and effective alternating vacuum filtration method, and as a result, the special sandwich structure endows the film with excellent electromagnetic shielding, insulation and TC performance. The composite film has an extremely high electromagnetic shielding effectiveness up to 60.7 dB at 8.2 GHz as well as still maintains good electrical insulation properties due to the presence of the CNF/BNNS layer on the surface. Moreover, when the content of BNNS in the CNF/BNNS layer reaches 70 wt%, the sandwiched film has excellent in-plane TC of 19.97 W m−1 K−1. The sandwiched film with excellent electromagnetic shielding and high TC yet insulation performance has great application value in highly integrated electronic devices.