The reactive air brazing (RAB) process of ceramics was developed in the early 2000s because high-temperature electrochemical devices, such as solid oxide fuel cells (SOFCs), gas separators, reformers, and ion transport membrane systems, are increasingly emerging. Accordingly, the reactive air wetting (RAW) and RAB of oxide ceramics have been investigated. Starting from the introduction of the advantages of the RAB process, the thermal expansion coefficients (TECs) of related materials, and the estimation of the TECs of Ag-based composite fillers, the RAW and RAB of ceramics are reviewed by classifying the employed ceramic materials, which mainly include yttria-stabilized zirconia (YSZ), perovskite oxides, Al₂O₃, and nonoxide ceramics. In particular, the RAW and RAB processes, interfacial microstructures, reaction products, and joint reliability (including joint strength, fracture energy, gas tightness, and high-temperature aging resistance) are highlighted for understanding interfacial behavior and joint performance and developing application-oriented brazing technology. Finally, some helpful conclusions are drawn after summarizing the RAB of oxide ceramics. The prospects for RAB of SiC and high-entropy oxide ceramics are proposed after summarizing the RAB of oxide and nonoxide ceramics, and several aspects are proposed for promoting the development and application of RAB technology.

Improving the power factor (PF) of thermoelectric materials is crucial for enhancing output power density and broadening practical applications. The near-room-temperature electrical performance of Mg₃(Sb,Bi)₂-based alloys is hindered due to the presence of Mg vacancies and grain boundary scattering, resulting in lower power factor. Herein, we introduced an excess of Mg into the Mg₃(Sb,Bi)₂ alloy during the hot-pressing process, triggering a liquid phase sintering process, which can effectively fill the Mg vacancies and increase the average grain size to significantly reduce grain boundary scattering. This leads to enhanced room-temperature electrical conductivity (σ) without detrimental effects on the Seebeck coefficient (S), thus yielding a high average PF of ~25.3 μW cm^-1 K^-2 and an average figure of merit (ZT) of ~ 1.03 within the temperature range of 323‒623 K. Moreover, different amounts of W were further added, and density-functional theory (DFT) calculations reveal that W segregation at grain boundaries reduces interfacial potential barriers, leading to an improved S and σ. Consequently, an ultrahigh average PF of ~26.2 μW cm^-1 K^-2 was attained in the W_0.06Mg_3.2Sb_1.5Bi_0.49Te_0.01–4%Mg alloys. Additionally, the mechanical properties (Vickers hardness and fracture toughness) were also enhanced compared with the pristine Mg₃(Sb,Bi)₂ alloy. This dual-modified approach can significantly boost the TE performance and mechanical stability, advancing Mg₃(Sb,Bi)₂-based materials for practical applications.

We firstly performed the reactive air wetting and brazing of Al₂O₃ ceramics using Ag–(0.5‒12)Nb₂O₅ fillers, where Nb₂O₅ can react with liquid Ag and O₂ from air to generate AgNbO₃. The contact angle of the Ag–Nb₂O₅/Al₂O₃ system almost linearly decreases from ~71.6° to 32.5° with the Nb₂O₅ content increasing, and the joint shear strength reaches the maximum of ~65.1 MPa while employing the Ag–4Nb₂O₅ filler, which are mainly related to the formation and distribution of the AgNbO₃ phase at the interface. Moreover, the interfacial bonding and electronic properties of related interfaces were investigated by first-principles calculations. The calculated works of adhesion (W_a) of Ag(111)/Ag–O–AgNbO₃(001) and AgNbO₃(001)/Al₂O₃(100) interfaces are higher than that of the Ag(111)/Al₂O₃(110) interface, indicating good reliability of the Ag/AgNbO₃/Al₂O₃ structure. The relatively large interfacial charge transfer indicates the formation of Ag–Ag, Al–O, and Ag–O bonds in the Ag/AgNbO₃/Al₂O₃ structure, which can contribute to the interfacial bonding.

Two-dimensional nanomaterials (2DNMs) have attracted significant research interest due to their outstanding structural properties, which include unique electrical nanostructures, large surface areas, and high surface reactivity. These adaptable materials have outstanding physicochemical characteristics, making them useful in a variety of applications such as gas-sensing, electronics, energy storage, and catalysis. Extensive research has been conducted in the pursuit of high-performance room-temperature (RT) gas sensors with good selectivity, high sensitivity, long-term stability, and rapid response/recovery kinetics. Metal oxides, transition metal chalcogenides, MXenes, graphene, phosphorene, and boron nitride have all been discovered as 2DNMs with strong potential for gas sensors. This review presents an in-depth analysis of current advances in 2DNM research. It includes synthetic techniques, structural stabilities, gas-sensing mechanisms, critical performance parameters, and factors influencing gas-sensing capabilities of 2DNMs. Furthermore, the present study emphasizes structural engineering and optimization methodologies that improve gas-sensing performance. It also highlights current challenges and outlines future research directions in the domain of tailoring 2DNMs for advanced RT gas sensors. This systematically designed comprehensive review article aims to provide readers with profound insights into gas detection, thereby inspiring the generation of innovative ideas to develop cutting-edge 2DNMs-based gas sensors.

Converting water into hydrogen fuel and oxidizing benzyl alcohol to benzaldehyde simultaneously under visible light illumination is of great significance, but the fast recombination of photogenerated carriers in photocatalysts seriously decreases the conversion efficiency. Herein, a novel dual-functional 0D Cd_0.5Zn_0.5S/2D Ti₃C₂ hybrid was fabricated by a solvothermally in-situ generated assembling method. The Cd_0.5Zn_0.5S nano-spheres with a fluffy surface completely and uniformly covered the ultrathin Ti₃C₂ nanosheets, leading to the increased Schottky barrier (SB) sites due to a large contact area, which could accelerate the electron-hole separation and improve the light utilization. The optimized Cd_0.5Zn_0.5S/Ti₃C₂ hybrid simultaneously presents a hydrogen evolution rate of 5.3 mmol/(g·h) and a benzaldehyde production rate of 29.3 mmol/(g·h), which are ~3.2 and 2 times higher than those of pristine Cd_0.5Zn_0.5S, respectively. Both the multiple experimental measurements and the density functional theory (DFT) calculations further demonstrate the tight connection between Cd_0.5Zn_0.5S and Ti₃C₂, formation of Schottky junction, and efficient photogenerated electron-hole separation. This paper suggests a dual-functional composite catalyst for photocatalytic hydrogen evolution and benzaldehyde production, and provides a new strategy for preventing the photogenerated electrons and holes from recombining by constructing a 0D/2D heterojunction with increased SB sites.

One-dimensional nanofibers can be transformed into hollow structures with larger specific surface area, which contributes to the enhancement of gas adsorption. We firstly fabricated Cu-doped In₂O₃ (Cu-In₂O₃) hollow nanofibers by electrospinning and calcination for detecting H₂S. The experimental results show that the Cu doping concentration besides the operating temperature, gas concentration, and relative humidity can greatly affect the H₂S sensing performance of the In₂O₃-based sensors. In particular, the responses of 6%Cu-In₂O₃ hollow nanofibers are 350.7 and 4201.5 to 50 and 100 ppm H₂S at 250 ℃, which are over 20 and 140 times higher than those of pristine In₂O₃ hollow nanofibers, respectively. Moreover, the corresponding sensor exhibits excellent selectivity and good reproducibility towards H₂S, and the response of 6%Cu-In₂O₃ is still 1.5 to 1 ppm H₂S. Finally, the gas sensing mechanism of Cu-In₂O₃ hollow nanofibers is thoroughly discussed, along with the assistance of first-principles calculations. Both the formation of hollow structure and Cu doping contribute to provide more active sites, and meanwhile a little CuO can form p-n heterojunctions with In₂O₃ and react with H₂S, resulting in significant improvement of gas sensing performance. The Cu-In₂O₃ hollow nanofibers can be tailored for practical application to selectively detect H₂S at lower concentrations.

Silicon carbide (SiC) has been widely concerned for its excellent overall mechanical and physical properties, such as low density, good thermal-shock behavior, high temperature oxidation resistance, and radiation resistance; as a result, the SiC-based materials have been or are being widely used in most advanced fields involving aerospace, aviation, military, and nuclear power. Joining of SiC-based materials (monolithic SiC and SiC_f/SiC composites) can resolve the problems on poor processing performance and difficulty of fabrication of large-sized and complex-shaped components to a certain extent, which are originated from their high inherent brittleness and low impact toughness. Starting from the introduction to SiC-based materials, joining of ceramics, and joint strength characterization, the joining of SiC-based materials is reviewed by classifying the as-received interlayer materials, involving no interlayer, metallic, glass-ceramic, and organic interlayers. In particular, joining processes (involving joining techniques and parameter conditions), joint strength, interfacial microstructures, and/or reaction products are highlighted for understanding interfacial behavior and for supporting development of application-oriented joining techniques.