Hierarchical Cellular Structured Ceramic Nanofibrous Aerogels with Temperature-Invariant Superelasticity for Thermal Insulation

Abstract

Silica aerogels are attractive for thermal insulation due to their low thermal conductivity and good heat resistance performance. However, the fabrication of silica aerogels with temperature-invariant superelasticity and ultralow thermal conductivity has remained extremely challenging. Herein, we designed and synthesized a hierarchical cellular structured silica nanofibrous aerogel by using electrospun SiO₂ nanofibers (SNFs) and SiO₂ nanoparticle aerogels (SNAs) as the matrix and SiO₂ sol as the high-temperature nanoglue. This pathway leads to the intrinsically random deposited SNFs assembling into a fibrous cellular structure, and the SNAs are evenly distributed on the fibrous cell wall. The unique hierarchical cellular structure of the ceramic nanofibrous aerogels endows it with integrated performances of the ultralow density of ∼0.2 mg cm^-3, negative Poisson's ratio, ultralow thermal conductivity (23.27 mW m^-1 K^-1), temperature-invariant superelasticity from -196 to 1100 °C, and editable shapes on a large scale. These favorable multifeatures present the aerogels ideal for thermal insulation in industrial, aerospace, and even extreme environmental conditions.