Multifunctional Melamine Foam Composites Featuring Asymmetric Conductive Networks for Highly Absorptive EMI Shielding and Infrared Stealth
The escalating demand for lightweight, multifunctional stealth materials in modern protective applications necessitates integrated solutions against electromagnetic interference (EMI), infrared (IR) detection, and incendiary threats. This study presents an innovative melamine foam (MF)-based composite featuring an asymmetric dual-nano conductive network, achieving absorption-dominated EMI shielding, IR stealth, and flame retardancy. Inspired by the Salisbury screen, the composite employs MF as an interlayer and flame-retardant thermoplastic polyurethane (TPU) nanofiber membrane as a substrate. The architecture comprises a carbon nanotubes (CNTs)-modified impedance matching nanofiber layer as the top absorber and a silver nanoparticles (AgNPs)-modified nanofiber layer as the highly conductive reflective bottom. Precise control of CNTs content and interlayer thickness enables tunable electromagnetic wave (EMW) absorption, yielding a low reflection coefficient of 0.03 and a high EMI shielding effectiveness of 79.23 dB at a total thickness of 4.40 mm. Even at 1.40 mm, effective absorption-dominated shielding is maintained. The performance remains stable under ultrasonic, compression, and bending tests, demonstrating high durability. The mechanism underlying absorption-dominated EMI shielding at reduced thickness, relying on destructive interference of EMWs enabled by the asymmetric dual-nano conductive network, is thoroughly elucidated. Additionally, the composite exhibits superior IR stealth and self-extinguishing properties. This work offers a feasible strategy for designing high-performance stealth materials with strong potential for personnel and communication equipment protection.