Flexible, magnetic and sandwich-structural Fe2O3/CNT/Fe2O3 composite film with absorption-dominant EMI shielding performance

Abstract

To mitigate secondary electromagnetic pollution, there is an urgent need to develop absorption-dominant electromagnetic interference (EMI) shielding materials with low density, reduced thickness, lightweight construction, flexibility, exceptional mechanical strength, and superior electrothermal and photothermal properties, particularly for flexible and wearable electronics. In this regard, we designed an absorption-based composite film comprising carbon nanotubes (CNT) and α-Fe₂O₃, featuring a CNT layer sandwiched between two α-Fe₂O₃ layers on the upper and lower surfaces. This composite film was fabricated through an electrodeposition process followed by a thermal annealing procedure to achieve enhanced EMI shielding performance along with improved electrothermal and photothermal properties. The strategically designed sandwich structure allows the rough surface of the upper α-Fe₂O₃ layer to not only improve the impedance mismatch between free space and the composite film, facilitating the penetration of incident electromagnetic (EM) waves into the film and promoting increased EM absorption rather than reflection, but also to enhance electrical conductivity, thereby improving electron mobility and density. Consequently, the average total shielding effectiveness (SE) of the CNT/Fe₁₆-300 composite demonstrates remarkable EMI shielding effectiveness (EMI SE: 56.8 dB). Furthermore, the alteration in the absorption-to-reflection ratio (A/R) signifies a transition in the EMI shielding mechanism from reflection (0.69 for the pristine CNT film) to absorption (1.86 for the CNT/Fe₁₆-300) with the incremental deposition of α-Fe₂O₃ nanoparticles. This work presents a feasible manufacturing approach for developing composite films with a sandwich structure that exhibits absorption-dominant EMI shielding capabilities, contributing to advancements in thermal management and multifunctional electromagnetic shielding applications.