Efficient Construction of Hierarchical Polyurethane Composite Foam for High Microwave Absorption Performance

• • The hierarchical PU composite foam (3*PFC 0.5-1.0-1.5) achieves an effective absorption bandwidth (EAB) of 15.7 GHz, covering 98.1% of the 2–18 GHz range, which is critical for broadband EMW suppression in S, C, X, and Ku bands. • • The in-situ polymerization foaming method ensures strong interfacial adhesion between MWCNTs/FCI and the PU matrix, overcoming the weak adhesion and multi-cycle processing limitations of impregnation methods, thereby enhancing durability and stability. • • The composite maintains low density and high compressibility, addressing the weight and flexibility bottlenecks of traditional ferrite-based absorbers, making it suitable for wearable and stealth applications. • • Synergistic incorporation of conductive MWCNTs and anisotropic FCI constructs impedance matching and multiple loss mechanisms (conductive, interfacial, and magnetic), leading to an EAB that covers nearly the entire tested frequency range.