Proton Donor-Regulated Mechanically Robust Aramid Nanofiber Aerogel Membranes for High-Temperature Thermal Insulation

High-performance thermal insulators are urgently desired for energy-saving and thermal protection applications. However, the creation of such materials with synchronously ultralow thermal conductivity, lightweight, and mechanically robust properties still faces enormous challenges. Herein, a proton donor-regulated assembly strategy is presented to construct asymmetric aramid nanofiber (ANF) aerogel membranes with a dense skin layer and a high-porous nanofibrous body part. The asymmetric structure originates from the otherness of the structural restoration of deprotonated ANFs and the resulting ANF assembly due to the diversity of available proton concentrations. Befitting from the synergistic effect of the distinct architectures, the resulting aerogel membranes exhibit excellent overall performance in terms of a low thermal conductivity of 0.031 W·m^-1·K^-1, a low density of 19.2 mg·cm^-3, a high porosity of 99.53%, a high tensile strength of 11.8 MPa (16.5 times enhanced), high heat resistance (>500 °C), and high flame retardancy. Furthermore, a blade-scraping process is further proposed to fabricate the aerogel membrane in a continuous and scalable manner, as it is believed to have potential applications in civil and military fields.