Absorption-based electromagnetic interference shielding composites with sandwich structure by one-step electrodeposition method

The absorption-dominant electromagnetic interference (EMI) shielding materials with light weight, great flexibility, fast heat dissipation and excellent mechanical strength are highly demanded in civil and military applications. In this regard, the absorption-based CNT/Co composite film with sandwich structure (Co/Co-CNT/Co layer) was designed for highly EMI shielding performance and heat dissipation. The existence of Co layers on CNT/Co composite film has suitable impedance matching between film and free space, which can increase EM waves absorption and decrease EM waves reflection. Appropriately incorporating Co nanoparticles into the CNT film can facilitate the interfacial polarization, dipole polarization and dielectric loss derived from conduction loss, thus CNT/Co composite film shows high EMI shielding effectiveness (EMI SE: 49 dB), tensile strength (120 MPa), excellent electrical and thermal conductivity of 61.1 S/cm and 66.8 W/mK respectively. Furthermore, the ratio of absorption (SEA) and total EMI SE (SET) for pristine CNT film is 86.64% and for CNT/Co composite film is 93.31%, and the ratios of A/R for pristine CNT film (0.58) and CNT/Co composite film (1.20) manifest that the EMI shielding mechanism transforms from reflection to absorption. This work offers a novel method to develop the sandwich-structure composites with absorption-dominant EMI shielding performance in the application of advanced multifunctional electromagnetic shielding field.