Interfacial Welding Enabled Hierarchical Silk Nanofibrous Aerogels for Thermal and Electromagnetic Protection in Extreme Environments

Abstract Advanced protective equipment operating in extreme environments urgently demands lightweight materials that integrate thermal insulation and electromagnetic interference (EMI) shielding against severe thermal fluctuations and pervasive radiation. Herein, we report the hierarchical and mechanically robust silk nanofibrous aerogels (SNFAs) produced through a green interfacial-welding strategy. By utilizing waterborne polyurethane as a molecular solder to construct multi-site hydrogen bonding and chain entanglement at the contact nodes of natural silk nanofibrils, discrete building blocks are effectively transformed into an interconnected, load-bearing 3D network that suppresses structural collapse and effectively dissipates localized stress during deformation. Consequently, the SNFAs achieve an ultralow density (4 mg cm−3) and exceptional structural stability (compressive stress of 20.1 kPa at 80% strain). Benefiting from the slender solid pathways that minimize solid-phase heat conduction and the intact cellular walls that suppress gas convection, the aerogels demonstrate outstanding thermal insulation with a low thermal conductivity of 28.5 mW m−1 K−1. Furthermore, the introduction of carbon nanotubes endows the aerogels with efficient electrical transport and interfacial polarization, while the multi-tiered porous framework promotes repeated internal electromagnetic reflections, thereby yielding a remarkable EMI shielding effectiveness (40 dB) and electrical conductivity (139.3 S m−1). Collectively, this study presents an innovative welding approach that uses ductile polymer welding to overcome the fragility of natural nanofibrous assemblies, providing a sustainable and resilient framework for the development of next-generation multifunctional protective gear in extreme environments.