Ultralight, Elasto-Flexible, and High-Temperature Resistant Ceramic Nanofiber Sponges for Thermal Superinsulation

Advanced ceramic sponge materials that combine sufficient elasticity with splendid high-temperature resistance are urgently needed as thermal insulators in harsh environments. However, the development of ceramics in ultralight and elastic material systems is severely constrained by their brittleness and defect sensitivity. Here, this study reports an elasto-flexible, heat-resisting, and lamellar-structured ceramic sponge based on yttria-stabilized ZrO₂ (YSZ) nanofibers through a scalable solution blow spinning process. The YSZ nanofibers exhibit small grain sizes (≈50 nm at 1300 °C), providing crucial support for the mechanical and thermal properties. The porous 3D sponges formed by in situ deposition of YSZ nanofibers possess ultralight density (≥ 5 mg cm^-3), 80% reversible compressive strains, high fatigue resistance (less than 1.59% permanent degradation after 1000 cycles at 50% strain), and can fully recover from large deformations with near-zero Poisson's ratios. In addition, the YSZ nanofiber sponges exhibit temperature-invariant superelasticity range from -196 to 1300 °C, exceptional bendability, low thermal expansion coefficient (9.26 × 10^-6 °C^-1 at 1300 °C), and excellent thermal insulation with a thermal conductivity as low as 0.028 W m^-1 K^-1. Such rarely integrated properties sharply contrast with those of polymer/carbon materials and traditional ceramic aerogels, making ceramic sponges ideal for many high-end applications.