Iron oxide/CNT-based artificial nacre for electromagnetic interference shielding

Biological structural materials, despite consisting of limited kinds of compounds, display multifunctionalities due to their complex hierarchical architectures. While some biomimetic strategies have been applied in artificial materials to enhance their mechanical stability, the simultaneous optimization of other functions along with the mechanical properties via biomimetic designs has not been thoroughly investigated. Herein, iron oxide/carbon nanotube (CNT)-based artificial nacre with both improved mechanical and electromagnetic interference (EMI) shielding performance is fabricated via the mineralization of Fe3O4 onto a CNT-incorporated matrix. The micro- and nano-structures of the artificial nacre are similar to those of natural nacre, which in turn improves its mechanical properties. The alternating electromagnetic wave-reflective CNT layers and the wave-absorptive iron oxide layers can improve the multiple reflections of the waves on the surfaces of the reflection layers, which then allows sufficient interactions between the waves and the absorption layers. Consequently, compared with the reflection-dependent EMI-shielding of the non-structured material, the artificial nacre exhibits strong absorption-dependent shielding behavior even with a very low content of wave-absorptive phase. Owing to the high mechanical stability, the shielding effectiveness of the artificial nacre that deeply cut by a blade is still maintained at approximately 70%–96% depending on the incident wave frequency. The present work provides a new way for designing structural materials with concurrently enhanced mechanical and functional properties, and a path to combine structural design and intrinsic properties of specific materials via a biomimetic strategy.