Ceramic aerogels are promising lightweight and high-efficient thermal insulators for applications in buildings, industry, and aerospace vehicles but are usually limited by their brittleness and structural collapse at high temperatures. In recent years, fabricating nanostructure-based ultralight materials has been proved to be an effective way to realize the resilience of ceramic aerogels. However, the randomly distributed macroscale pores in these architectures usually lead to low stiffness and reduced thermal insulation performance. Here, to overcome these obstacles, a SiC@SiO2 nanowire aerogel with a nanowire-assembled anisotropic and hierarchical microstructure was prepared by using directional freeze casting and subsequent heat treatment. The aerogel exhibits an ultralow thermal conductivity of ~14 mW/m·K, an exceptional high stiffness (a specific modulus of ~24.7 kN·m/kg), and excellent thermal and chemical stabilities even under heating at 1200°C by a butane blow torch, which makes it an ideal thermally superinsulating material for applications under extreme conditions.

With the prevailing energy challenges and the rapid development of aerospace engineering, high-performance thermal insulators with various functions are attracting more and more attention. Ceramic aerogels are promising candidates for thermal insulators to be applied in harsh environments because of their low thermal conductivity and simultaneously excellent thermal and chemical stabilities. In general, the effective properties of this class of materials depend on both their microstructures and the intrinsic properties of their building blocks. Herein, to enrich the family and broaden the application fields of this class of materials, we prepared ultralight α-Si 3 N 4 nanobelt aerogels (NBAs) with tunable densities ranging from 1.8 to 9.6 mg cm −3 . The α-Si 3 N 4 NBA realized resilient compressibility (with a recoverable strain of 40−80%), fire resistance (1200 °C butane blow torch), thermal insulation (0.029 W m −1 K −1 ), and electronic wave transparency (a dielectric constant of 1−1.04 and a dielectric loss of 0.001−0.004) in one material, which makes it a promising candidate for mechanical energy dissipative, fire-resistant, and electronic wavetransparent thermal insulator to be applied in extreme conditions. The successful preparation of such resilient and multifunctional α-Si 3 N 4 NBAs will open up a new world for the development and widespread applications of ceramic aerogels.

Resilient ceramic aerogels exhibit great potential for applications in harsh environments owing to their unique combination of ultrahigh porosity, lightweight, reversible compressibility, and good thermal and chemical stabilities. However, their applications are severely restricted by the limited size and low yield due to their complicated and time-consuming synthetic procedures. Herein, we developed an efficient method for large-scale production of resilient SiC nanowire aerogels (SiC NWAGs) with tunable densities and desired shapes. The as-synthesized SiC NWAGs displayed excellent high-temperature stability (the maximum working temperature in Ar and air can reach to 1400 and 1000 °C, respectively), outstanding flame-erosion resistance and low thermal conductivity (25 mW m–1 K–1). The easy fabrication of such ceramic aerogel on a large scale will pave the way for the widespread applications of ceramic aerogels.

Ceramic aerogels are attractive candidates for high-temperature thermal insulation, catalysis support, and ultrafiltration materials, but their practical applications are usually limited by brittleness. Recently, reversible compressibility has been realized in flexible nanostructures-based ceramic aerogels. However, these modified aerogels still show fast and brittle fracture under tension. Herein, we demonstrate achieving reversible stretch and crack insensitivity in a highly compressible ceramic aerogel through engineering its microstructure by using curly SiC-SiO x bicrystal nanowire as the building blocks. The aerogel exhibits large-strain reversible stretch (20%) and good resistance to high-speed tensile fatigue test. Even for a prenotched sample, a reversible stretch at 10% strain is achieved, indicating good crack resistance. The aerogel also displays reversible compressibility up to 80% strain, ultralow thermal conductivity of 28.4 mW m–1 K–1, and excellent thermal stability even at temperatures as high as 1200 °C in butane blow torch or as low as −196 °C in liquid nitrogen. Our findings show that the attractive tensile properties arise from the deformation, interaction, and reorientation of the curly nanowires which could reduce stress concentration and suppress crack initiation and growth during tension. This study not only expands the applicability of ceramic aerogels to conditions involving complex dynamic stress under extreme temperature conditions but also benefits the design of other highly stretchable and crack-resistant porous ceramic materials for various applications.

Lightweight electromagnetic (EM) wave absorbers made of ceramics have sparked tremendous interest for applications in EM wave interference protection at high temperatures. However, EM wave absorption by pure ceramics still faces huge challenges due to the lack of efficient EM wave attenuation modes. Inspired by the energy dissipation mechanism during fracture of lobster shells with a soft and stiff multilayered structure, we fabricate a highperformance EM wave absorption ceramic aerogel composed of an alternating multilayered wave transparent Si 3 N 4 (N) layer and wave absorption SiC (C) layer by a simple restack method. The obtained N/C aerogel shows ultralow density (∼8 mg/cm 3 ), broad effective absorption bandwidth (8.4 GHz), strong reflection loss (−45 dB) at room temperature, and excellent EM wave absorption performance at high temperatures up to 1000 °C. The attenuation of EM wave mainly results from a "reflection−absorption−zigzag reflection" process caused by the alternating multilayered structure. The superior absorption performance, especially at high temperatures, makes the N/C aerogel promising for next-generation wave absorption devices served in high-temperature environments.