Ultralight ceramic aerogels with the property combination of recoverable compressibility and excellent high-temperature stability are attractive for use in harsh environments. However, conventional ceramic aerogels are usually constructed by oxide ceramic nanoparticles, and their practical applications have always been limited by the brittle nature of ceramics and volume shrinkage at high temperature. Silicon carbide (SiC) nanowire offers the integrated properties of elasticity and flexibility of one-dimensional (1D) nanomaterials and superior high-temperature thermal and chemical stability of SiC ceramics, which makes it a promising building block for compressible ceramic nanowire aerogels (NWAs). Here, we report the fabrication and properties of a highly porous three-dimensional (3D) SiC NWA assembled by a large number of interweaving 3C-SiC nanowires of 20-50 nm diameter and tens to hundreds of micrometers in length. The SiC NWA possesses ultralow density (∼5 mg cm), excellent mechanical properties of large recoverable compression strain (>70%) and fatigue resistance, refractory property, oxidation and high-temperature resistance, and thermal insulating property (0.026 W m K at room temperature in N). When used as absorbents, the SiC NWAs exhibit an adsorption selectivity of low-viscosity organic solvents with high absorption capacity (130-237 g g). The successful fabrication of such an attractive material may provide promising perspectives to the design and fabrication of other compressible and multifunctional ceramic NWAs.

High-entropy ceramics (HECs) are solid solutions of inorganic compounds with one or more Wyckoff sites shared by equal or near-equal atomic ratios of multi-principal elements. Although in the infant stage, the emerging of this new family of materials has brought new opportunities for material design and property tailoring. Distinct from metals, the diversity in crystal structure and electronic structure of ceramics provides huge space for properties tuning through band structure engineering and phonon engineering. Aside from strengthening, hardening, and low thermal conductivity that have already been found in high-entropy alloys, new properties like colossal dielectric constant, super ionic conductivity, severe anisotropic thermal expansion coefficient, strong electromagnetic wave absorption, etc., have been discovered in HECs. As a response to the rapid development in this nascent field, this article gives a comprehensive review on the structure features, theoretical methods for stability and property prediction, processing routes, novel properties, and prospective applications of HECs. The challenges on processing, characterization, and property predictions are also emphasized. Finally, future directions for new material exploration, novel processing, fundamental understanding, in-depth characterization, and database assessments are given.

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.

We developed an updated nonstationary bias-correction method for a monthly global climate model of temperature and precipitation. The proposed method combines two widely used quantile mapping bias-correction methods to eliminate potential illogical values of the variable. Instead of empirical parameter estimation in the more-common quantile mapping method, our study compared bias-correction performance when parametric or nonparametric procedures were used to estimate the probability distribution. The results showed our proposed bias-correction method to be very effective in reducing the model bias: it removed over 80% and 83% of model bias for surface air temperature and precipitation, respectively, during the validation period. Compared with a widely used method of bias correction (delta change), our proposed technique demonstrates improved correction of the distribution of variables. In addition, nonparametric estimation procedures further reduced the mean absolute errors in temperature and precipitation during the validation period by approximately 2% and 0.4%, respectively, compared with parametric procedures. The proposed method can remove over 40% and 60% of the uncertainty from model temperature and precipitation projections, respectively, at the global land scale.

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.

Dental caries is a highly prevalent oral disease that can lead to severe dental damage and may greatly compromise the quality of life of the affected individuals. Previous studies, including those based on 16S rRNA gene, have revealed that the oral microbiota plays a prominent role in development of the disease. But the approach of those studies was limited in analyzing several key microbiome traits, including species- or strain-level composition and functional profile. Here, we performed metagenomic analyses for a cohort of preschool children with or without caries. Our results showed that caries was associated with extensive microbiota differences at various taxonomic and functional levels. Some caries-associated species had not been previously reported, some of which may have significant clinical implications. A microbiome gene catalogue from children with caries was constructed for the first time. The results demonstrated that caries is associated with alterations of the oral microbiome, including changes in microbial composition and metabolic functional profile.

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.