Advances in reactive air wetting and brazing of engineering ceramics

Reactive air brazing (RAB) process of ceramics was developed since the early 2000s because high temperature electrochemical devices were increasingly emerging, such as solid oxide fuel cells (SOFCs), gas separators and reformers, and ion transport membrane system. Accordingly, the reactive air wetting (RAW) and RAB of oxide ceramics were dominantly investigated. Starting from the introduction of advantages of RAB process, thermal expansion coefficients (TECs) of related materials, and estimation of TECs of Ag-based composite fillers, the RAW and RAB of ceramics are reviewed by classifying the employed ceramic materials, mainly involving yttria-stabilized zirconia (YSZ), perovskite oxides, Al₂O₃ and non-oxide ceramics. In particular, the RAW and RAB processes, interfacial microstructures, reaction products, as well as joint reliability (including joint strength, fracture energy, gas tightness and high-temperature aging resistance) are highlighted for understanding interfacial behavior and joint performances 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 put forward after summarizing the RAB of oxide and non-oxide ceramics, and several aspects are proposed for promoting the development and application of RAB technology.