Ambient dried cellulose paper- based sandwich structural composite with broadband, low reflective, and high EMI shielding efficiency

Most reported shielding materials exhibit reflection-dominated shielding mechanisms, which further leads to the secondary electromagnetic radiation contamination. This work reports a low reflective and scalable cellulose paper- based EMI shielding composite (ACMA) with a sandwich structure via assembling of the MXene containing aerogel layer, MXene coated paper (MP) layer, and highly conductive AgNWs/CNF film (AC) layer in a conductivity gradient. The shielding performances and mechanisms of each layer, AC-MP bi-layer, and AC-MP-aerogel tri-layer are investigated. Results show that the AC film could significantly increase the EMI SE of MP but produce super high R coefficient (0.92). The aerogel layer is effective in decreasing the R coefficient, which is correlated with its MXene content and thickness. The ACMA yields an average EMI SE of 71.46 dB and ultralow R coefficient of 0.1 in the X band when the aerogel has a MXene/BC of 90 % and a thickness of 2.6 mm. A large size ACMA is showcased, and it achieves an average EMI SE ranging from 56.82 dB to 75.85 dB in 2–18 GHz and an absorption- dominated shielding mechanism in 8–18 GHz. In addition, the ACMA also demonstrates excellent thermal camouflage property as the aerogel layer contacts the object.