Efficient construction of hierarchical polyurethane composite foam for high microwave absorption performance

There is an urgent need to develop high-efficiency microwave absorption materials (MAMs) with excellent comprehensive performance. In this work, a lightweight microwave-absorbing composite was fabricated by synergistically introducing multi-walled carbon nanotubes (MWCNTs) and flaky carbonyl iron (FCI) into a flexible polyurethane foam (PUF) matrix during an in-situ polymerization foaming process. Successful loading of conductive MWCNTs and anisotropic FCI promotes the construction of impedance matching structure and multiple loss mechanisms, providing the material with an efficient MA performance. The results show that the hierarchical PU composite foam of 3*PFC0.5-1.0-1.5 possesses an effective absorption bandwidth (EAB) of 15.7 GHz, which covers 98.1% of tested bands (2–18 GHz). It realizes a broadband effective absorption for electromagnetic waves (EMWs) in S, C, X, and Ku bands. Meantime, it maintains low density and high compressibility. Highly efficient MA and excellent mechanical properties make the composite material show significant application prospects in the fields of 5th generation (5G) communications, military stealth, and smart electronic devices.