Nanofibrous core/nanoporous sheath structured ultra-flexible ceramic aerogels for thermal superinsulation

Thermal superinsulation, arising from nanoporous aerogels with pore sizes < 70 nm, involves ultralow heat conduction with a thermal conductivity lower than that of stationary air (24 mW m^-1 K^-1). However, the inherently weak necklace connection mechanism between building units and the confined deformation space within nanopores result in the intrinsic brittleness of these materials. Additionally, improvements in their mechanical flexibility typically result in compromised thermal insulation performance. To address this limitation, we herein report a core-sheath structure design of La₂Y_0.4TiZr₂O_9.6 ceramic aerogel (CSCA) featuring a nanofibrous core framework for flexible deformation and a nanoporous aerogel sheath for thermal superinsulation. The resulting aerogel demonstrates remarkable mechanical flexibility with a compressive strain of up to 80% , a fracture strain of up to 21.9% and a bending strain of up to 100%, as well as thermal superinsulation with a conductivity of 21.96 mW m^-1 K^-1 at 26 °C and remains stable at working temperatures exceeding 1300 °C. Ultimately, proposed CSCA constitutes a fundamentally new approach in structure design to resolving the formidable mechanical-thermal tradeoff of aerogels, and it offers promising material configuration for further advancements in thermal superinsulation.