In situ Synthesis of Biomimetic Silica Nanofibrous Aerogels with Temperature-Invariant Superelasticity over One Million Compressions.

Resilient and compressible three-dimensional nanomaterials comprising polymers, carbon, and metals have been prepared in diverse forms. However, the creation of thermostable elastic ceramic aerogels remains an enormous challenge. We demonstrate an in situ synthesis strategy to develop biomimetic silica nanofibrous (SNF) aerogels with superelasticity by integrating flexible electrospun silica nanofibers and rubber-like Si-O-Si bonding networks. The stable bonding structure among nanofibers is in situ constructed along with a fibrous freeze-shaping process. The resultant SNF aerogels exhibit integrated properties of ultralow density (>0.25 mg cm-3 ), temperature-invariant superelasticity up to 1100 °C, and robust fatigue resistance over one million compressions. The ceramic nature also endows the aerogels with fire resistance and ultralow thermal conductivity. The successful synthesis of the SNF aerogels opens new pathways for the design of superelastic ceramic aerogels in a structurally adaptive and scalable form.