Ultralight and fire-resistant ceramic nanofibrous aerogels with temperature-invariant superelasticity to 1100°C.

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.

Advanced ceramic aerogel materials with a performance combining sufficient mechanical robustness and splendid high-temperature resistance are urgently needed as thermal insulators in harsh environments. However, the practical applications of ceramic aerogel materials are always limited by poor mechanical performance and degradation under thermal shock. Here, we report the facile creation of lamellar multiarch structured ceramic nanofibrous aerogels that are simultaneously ultrastrong, superelastic, and high temperature resistant by combining ZrO 2 −Al 2 O 3 nanofibers with Al(H 2 PO 4 ) 3 matrices. The resulting ZrO 2 −Al 2 O 3 nanofibrous aerogels exhibit the integrated properties of rapid recovery from a strain of 90%, high compression strength of more than 1100 kPa (at a strain of 90%), high fatigue resistance, and temperature-invariant superelasticity. Moreover, the all-ceramic component feature also provides the ceramic nanofibrous aerogels with high-temperature resistance up to 1300 °C and thermal insulation performance with low thermal conductivity (0.0322 W m −1 K −1 ). These superior performances make the ceramic aerogels ideal for high-temperature thermal insulation materials in extreme conditions. KEYWORDS: electrospinning, ZrO 2 −Al 2 O 3 nanofibrous aerogels, robust mechanical strength, temperature-invariant superelasticity, high-temperature insulation

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.

Ceramic aerogels are attractive candidates for thermal insulation systems in spaceships, missiles, and aircrafts. However, the general lack of mechanical stability in conventional ceramic aerogels presents a major challenge for their practical applications. To date, the creation of mechanically robust ceramic aerogels has not made significant progress. Herein, a universal strategy is presented to fabricate ceramic nanofibrous aerogels with both superior bendability and compressibility, by assembling flexible silica nanofibers with a high length-to-diameter ratio into a highly continuous interwoven cellular structure. The resulting aerogels, with improved structural continuity, exhibit enhanced mechanical properties including large compression and buckling strain recovery (85%), temperature-invariant superelasticity (from −196 °C to 1100 °C), and robust fatigue tolerance up to 100 000 cycles. In parallel, the low thermal conductivity (0.0223 W m −1 K −1), as well as exceptional high-temperature thermal insulation performance enable them to be ideal candidates for thermal insulation in extreme environments. The successful synthesis of this material may shed light on the development of other mechanically robust ceramic aerogels.