Fig. 1. Dependence of the relative modulus on the relative density for typical resilient ceramic aerogel, including α-Si3N4 nanobelt (NB) aerogel [51], SiO2 NF aerogel [48], PAN/SiO2 NF aerogel [47], Al2O3 nanolattice [39] and SiC nanowire aerogel [50].

Fig. 2. Microstructure of the resilient ceramic aerogels. (a) BN foam [38]; (b) BN foam [58]; (c) TiO2 nanofiber (NF) aerogel [45]; (d) SiC nanowire (NW) aerogel [49]; (e) PAN/SiO2 NF aerogel [47]; (f) BN aerogel [44]; (g) Si3N4 NB aerogel [51]; (h) SiO2 NF aerogel [48]; (i) V2O5 NW aerogel [59]; (j) BN/Polymer aerogel [42]; (k) Al2O3 nanolattice [39]; (l) BN aerogel [43].

Fig. 3. Preparation methods of the nanofibers assembled aerogels. (a) Solution blow-spinning method to fabricate ceramic nanofiber sponges [45]; (b) Freeze-drying method to prepare PAN/SiO2 nanofiber aerogels [47]; (c) Instant freezing-drying method to prepare V2O5 nanofiber scaffold with lamellar microstructure [59].

Fig. 4. Sacrificial template method to prepare resilient aerogels. (a) Preparation process of BN foam with randomly distributed microstructure by using a Ni foam as the sacrificial template [38,53]; (b) Preparation of BN aerogel with double-pane-hyperbolic-porous architecture [43]; (c) Preparation of ceramic nanolattice with periodic architecture by using a 3D printing polymer template [39].

Fig. 5. Preparation of SiC nanowires by using chemical vapor deposition method. (a) Schematic diagrams to illustrate the growth of SiC nanowire aerogel [49]; (b) A developed “growth-space assisted” chemical vapor deposition method for the fabrication of SiC nanowire aerogel in large scale [50]; (c) Macroscopic morphology of a piece of the SiC nanowire aerogel prepared by CVD method [49]; (d) Large-size SiC nanowire aerogel in the shape of tube and column prepared by “growth-space assisted” CVD method [50]; (e) SiC nanowire aerogels with complex shapes prepared by “growth-space assisted” CVD method [50].

Fig. 6. Reversible compressibility of resilient ceramic aerogels with randomly distributed microstructures. Compressive stress-strain curves of (a) BN foam, inset showing the TEM image of the hollow-tube-like struts of the foam [38]; (c) PAN/SiO2 NF aerogel [47]; (e) SiC nanowire aerogel [49]; Microstructure evolution of (b) BN foam [38]; (d) PAN/SiO2 NF aerogel [47] and (f) SiC nanowire aerogel during compression [49].

Fig. 7. Reversible compressibility of ceramic aerogels with anisotropic microstructure and 3D periodic microstructure. Compressive stress-strain curves of anisotropic V2O5 nanowire aerogel [59] (a) and Al2O3 nanolattice [39] (c). Microstructure evolution of anisotropic V2O5 nanowire aerogel [59] (b) and Al2O3 nanolattice [39] (d) during compression.

Fig. 8. Characterization of the high-temperature stability of the resilient ceramic aerogels. (a) Compression and recovery work of the SiO2 nanofiber aerogels after treatment at various temperatures for 30 min [48]. (b) XRD patterns of the SiO2 nanofiber aerogels after treatment at 1000, 1200, and 1400 °C for 30 min [48]. (c) Reversible compressibility of the SiO2 nanofiber aerogels under the heating of a butane blow torch [48]. (d) SiC nanowire aerogel under the heating of an alcohol lamp [49]. (e) Macroscopic images of SiC nanowire aerogel before and after isothermal heat treatment at 900 °C in air for 2 h [49]. (f) Compressive stress-strain curve of SiC nanowire aerogel after isothermal heat treatment at 900 °C in air for 2 h [49]. (g) Typical TEM image of a SiC nanowire after isothermal heat treatment at 900 °C in air for 1 h [49]. (h) A piece of Si3N4 nanobelt aerogel being heated under a butane blow torch [51]. (i) XRD patterns of the as-prepared Si3N4 nanobelt aerogel and the aerogels after treatment at 1200 °C and 1300 °C for 30 min [51]. (j) The strain-stress curve of the BN aerogel before and after 500 cycles of sharp thermal shocks. Inset showing the SEM images of the BN aerogel after the first and last thermal shock tests [43]. (k) Thermogravimetric analysis of BN aerogel in air and Ar [43].

Fig. 9. Thermal insulation performance of the resilient ceramic aerogels. (a) High-temperature insulation performance of ZrO2 nanofiber sponge. The ZrO2 sponge effectively protects the fresh petal from withering [45]. (b) Fresh petal protected by a piece of aerogel with a thickness of 10 mm from withering or carbonization under the heating of an alcohol lamp for 10 min [49]. (c) Thermal conductivity of the SiC NWA in N2 at different temperatures [49]. (d) Thermal conductivities of the SiO2 nanofiber aerogels as a function of density [48]. (e) The extra tortuous solid conduction path in double-paned BN aerogel [43]. (f) Thermal conductivity of BN aerogel in vacuum (steady-state thermal measurement) and in air (transient thermal measurement) [43]. (g) Infrared image of the front side subjected to the butane blow torch. Infrared images of the backside during the 30 min heating process: 2 min, 10 min, and 30 min [51].

Fig. 10. Various functions of the resilient ceramic aerogels for applications in environmental protection. (a) Oil and organic solvent absorption properties of the SiC nanowire aerogel [49]. (b) Photocatalytic property of TiO2 nanofiber sponge [45]. (c) The curve of pressure drop of YSZ nanofiber sponge filter depending on air?ow velocity, and the inset displaying the YSZ nanofiber aerogel under the heating of methane flame, indicating the high-temperature stability [46]. (d) Illustration of the test of High-temperature gas filtration property of YSZ nanofiber sponge [46]. (e) Concentration variation of particles before and after filtrating at 750 °C [46]. (f) SEM image of the sponge after filtration. Inset showing the application of the YSZ nanofiber sponge for an automobile exhaust gas filter [46].

Fig. 11. Electromagnetic wave transparent and absorbing performance of resilient ceramic aerogels for aerospace exploration. (a) Dielectric constant and (b) dielectric loss of Si3N4 nanobelt aerogel at temperatures ranging from room temperature to 1200 °C and frequency ranging from 8 to 18 GHz, indicating good high-temperature electromagnetic wave transparency [51]. (c) Reversible compressibility of SiC@C nanowire foam. (d) Electromagnetic wave absorbing frequency of SiC@C nanowire foam as a function of the compressive strain [63].