Highly stretchable ceramic sponge with excellent relaxation resistance for efficient air purification

Ceramic nanofibrous sponges are attractive for their broad applications in high-temperature air filtration, thermal insulation, sewage treatment, and catalyst support. However, the present ceramic sponges usually show brittle fracture even under tensile stresses. Herein, a ceramic sponge assembled by ultralong and crimped Si₃N₄ nanofiber nanofibers is designed and prepared to achieve temperature-invariant reversible from liquid nitrogen to 1200 °C and large elongations (ductile failure over 100 %) as well as excellent compressive anti-puncturing property. Moreover, the ceramic sponge illustrates a high filtration efficiency of 99.6 % for PM_2.5 and a low-pressure drop of 32 Pa during a long-term test under high-speed gas flow. It can also support photocatalyst g-C₃N₄ nanoparticles, yielding a high efficiency of photodegradation of nitrogen oxide gases. The well-designed ceramic nanofiber sponge with good comprehensive mechanical performances thus shows promising applications in air purification under extreme working conditions.