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.

With the booming of modern information technology, electromagnetic wave (EMW) absorption materials are playing more and more crucial roles in applications ranging from wearable smart electronics to national defense security. However, the application of present EMW absorption materials is severely hindered by their drawbacks, such as narrow absorption bandwidth and low absorption intensity. In this work, a series of highly porous and well-interconnected SiC@C nanowire foams (SCNFs) are rationally designed to exhibit modified impedance match and multiscale EMW energy dissipation mechanisms. The SCNF with a density of 108 mg cm–3 realizes a broad absorption bandwidth covering the whole X and Ku bands with an intensity of −52.5 dB. The SCNF with a density of 36 mg cm–3 and a thickness of 9.6 mm exhibits a mechanically controlled absorption band ranging from 2.9 to 18 GHz (covering over 93% of the entire radar band, 2–18 GHz) with a minimum intensity of −46 dB by simply applying a reversible compressive strain from 0 to 66.7%. Moreover, the special microstructure of SCNF also endows it with excellent hydrophobicity, which enables its good self-cleaning property. These encouraging achievements pave the way to the development of the continuous network microstructure of absorbents with a broad-band and tunable EMW absorption property.

Particulate matter (PM), a complex mixture of small particles and liquid droplets floating in air, is a consequence of severe air pollution. [1][2][3] PM is usually classified as PM 2.5 and PM 10 , referring to particle sizes less than 2.5 µm and between 2.5 and 10 µm, respectively. The smaller the PM, the more hazardous it becomes because it can penetrate into human lungs and bronchi, causing many respiratory diseases, including cancer. [4][5][6][7][8] Nowadays, PM has become a cosmopolitan environmental crisis, especially in developing countries. Therefore, managing and reducing PM pollution is urgently needed. [9,10] Particulate matter (PM) is one of the most severe air pollutants and poses a threat to human health. Air filters with high filtration efficiency applied to the source of PM are an effective way to reduce pollution. However, many of the present filtration materials usually fail because of their high pressure drop under high-velocity airflow and poor thermal stability at high temperatures. Herein, a highly porous Si 3 N 4 nanofiber sponge (Si 3 N 4 NFS) assembled by aligned and well-interconnected Si 3 N 4 nanofibers is designed and fabricated via chemical vapor deposition (CVD). The resulting ultralight Si 3 N 4 NFS (2.69 mg cm −3 ) processes temperature-invariant reversible strechability (10% strain) and compressibility (50% strain), which enables its mechanical robustness under high-velocity airflow. The highly porous and aligned microstructure result in a Si 3 N 4 NFS with high filtration efficiency for PM 2.5 (99.97%) and simultaneous low pressure drop (340 Pa, only <0.33% of atmospheric pressure) even under a high gas flow velocity (8.72 m s −1 ) at a high temperature (1000 °C). Furthermore, the Si 3 N 4 NFS air filter exhibits good long-term service ability and recyclability. Such Si 3 N 4 NFS with aligned microstructures for highly efficient gas filters provides new perspectives for the design and preparation of high-performance filtration materials.Air filters applied at the source of PM are thought to be an effective way to reduce air pollution. [11,12] Usually, there are two types of air filters. One is a porous membrane air filter, which usually has small pores to capture PMs. However, once PMs deposit and block the pores, the pressure drop becomes large, and the filter fails. [13] The other is a fibrous air filter, which exhibits a highly porous microstructure that is assembled by micrometer-sized fibers or nanofibers and captures PMs via a series of mechanisms such as physical interception, adhesion, and electrostatic interaction. [14][15][16] Compared with micrometer-sized fibrous air filters, nanofiber-based filters have higher PM trapping efficiency owing to their smaller pores and higher porosity. Nanofibrous air filters also have a low pressure drop because of the similar size of the nanofiber diameter and the average path of air molecules. [11] Ceramic fibrous air filters have recently gained increased attention owing to their prominent chemical and physical stabilities and high-...

Tungsten disulfide (WS2) as one of transition metal dichalcogenides exhibits excellent catalytic activity. However, its catalytic performances in aqueous phase reactions are limited by its hydrophobicity. Here, the natural hydrophilic two-dimensional clay was used to enhance the dispersibility of WS2 in aqueous phase. WS2/montmorillonite (WS2/MMT) composite nanosheets were prepared via hydrothermal synthesis of WS2 on the surface of montmorillonite from WCl6 and CH3CSNH2. The microstructure and morphology show that WS2 nanosheets are assembled parallelly on the montmorillonite with the interface interaction. Through the support of montmorillonite, WS2/MMT possesses higher photocatalytic ability for aqueous phase reactions than WS2, which could be due to the synergistic effect of higher adsorption property, higher hydrophilicity, dispersibility and more catalytic reaction site. The strategy could provide new ideas for obtaining novel hydrophilic photocatalyst with excellent performance.