Ceramics are usually composed of randomly oriented grains and intergranular phases, so their properties are the statistical average along each direction and show isotropy corresponding to the uniform microstructures. Some methods have been developed to achieve directional grain arrangement and preferred orientation growth during ceramic preparation, and then textured ceramics with anisotropic properties are obtained. Texture microstructures give particular properties to ceramics along specific directions, which can effectively expand their application fields. In this review, typical texturing techniques suitable for ceramic materials, such as hot working, magnetic alignment, and templated grain growth (TGG), are discussed. Several typical textured structural ceramics including α-Al₂O₃ and related nacre bioinspired ceramics, Si₃N₄ and SiAlON, h-BN, MB₂ matrix ultra-high temperature ceramics, MAX phases and their anisotropic properties are presented.

The multifunctional metastable SiBOCN system ceramics (including SiBN, SiCN, SiON, SiBC, SiBCN, SiBON, SiBOCN, etc.) are a new type of advanced structure–function integrated materials with unique structure and adjustable dielectric properties for high-temperature applications in thermal protection, communications, precise guidance, and microwave-absorption stealthy. These metastable materials generally require the rational co-design of multiscale structure and chemical composition to achieve desirable dielectric properties which induce interaction with incident electromagnetic wave. Herein, this review presents the latest development of metastable SiBOCN system ceramics, with the intent of summarising key findings, uncovering major trends and providing guidance for future efforts. Major themes in this assessment focus on the main processing routes, basic mechanisms for microwave transmission and absorption, scientific basis for material selection in specific background, principles for multiscale structure design and chemistry optimisation, tunable microwave transparent or absorbing properties, and future challenges and prospects in this active research filed.

In the past twenty years, Si-B-C-N ceramic has attracted wide attention due to its special structure and outstanding properties. The ceramic generally has an amorphous or a nano-crystalline structure, and has excellent structural stability, oxidation resistance, creep resistance and high-temperature mechanical properties, etc. Thus, Si-B-C-N ceramic attracts many researchers and finds potential applications in transportation, aerocraft, energy, information, microelectronics and environment, etc. Much work has been carried out on its raw materials, preparation processes, structural evolution, phase equilibrium and high-temperature properties. In recent years, many researchers focus on its new preparation methods, the preparation of dense ceramic sample with large dimensions, ceramic matrix composites reinforced by carbon fiber or SiC whisker, or components with various applications. Research on Si-B-C-N ceramic will develop our insight into the relationship between structures and properties of ceramics, and will be helpful to the development of novel high-performance ceramics. This paper reviews the preparation processes, general microstructures, mechanical, chemical, electrical and optical properties, and potential applications of Si-B-C-N ceramic, as well as its matrix composites.