Density-Tunable Aramid Nanofiber Foams for Flame Retardancy, Joule Heating, and Organic Solvent Absorption

Aramid nanofiber (ANF) based porous materials have been widely applied in thermal insulation, high-efficiency adsorption, and sensing technologies. However, significant volume shrinkage of ANF products during freeze-drying is inevitable due to the organic solvent used in the fabrication. This shrinkage leads to increased density and a reduced performance. In this study, we propose a method for fabricating ANF foam that utilizes Ni foam as an antideformation sacrifice layer to suppress the shrinkage induced by dimethyl sulfoxide (DMSO). The Ni foam is immersed in an ANF-DMSO dispersion, followed by solvent exchange and freeze-drying, during which a thin ANF layer is coated onto the foam skeleton. Subsequently, the ANF foam is obtained by etching the Ni skeleton and drying. The fabricated ANF foam exhibits an ultralow density of 7.98 mg/cm 3 and demonstrates exceptional structural stability. The foam exhibits outstanding mechanical properties and a remarkable load-bearing capacity, withstanding a weight of over 1229 times its own weight without structural damage. Furthermore, the ANF foam showcases superior thermal insulation and flame-retardant properties. It retains the structural characterization of abundant active sites on the surface and within its pores, enabling it to be functionalized with carbon nanotubes (CNT), designed to function as a self-heater and to absorb and degrade organic solvents.