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Atomically thin hexagonal boron nitride (h‐BN) is an emerging star of 2D materials. It is taken as an optimal substrate for other 2D‐material‐based devices owing to its atomical flatness, absence of dangling bonds, and excellent stability. Specifically, h‐BN is found to be a natural hyperbolic material in the mid‐infrared range, as well as a piezoelectric material. All the unique properties are beneficial for novel applications in optoelectronics and electronics. Currently, most of these applications are merely based on exfoliated h‐BN flakes at their proof‐of‐concept stages. Chemical vapor deposition (CVD) is considered as the most promising approach for producing large‐scale, high‐quality, atomically thin h‐BN films and heterostructures. Herein, CVD synthesis of atomically thin h‐BN is the focus. Also, the growth kinetics are systematically investigated to point out general strategies for controllable and scalable preparation of single‐crystal h‐BN film. Meanwhile, epitaxial growth of 2D materials onto h‐BN and at its edge to construct heterostructures is summarized, emphasizing that the specific orientation of constituent parts in heterostructures can introduce novel properties. Finally, recent applications of atomically thin h‐BN and its heterostructures in optoelectronics and electronics are summarized.

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-Al 2 O 3 and related nacre bioinspired ceramics, Si 3 N 4 and SiAlON, h-BN, MB 2 matrix ultra-high temperature ceramics, MAX phases and their anisotropic properties are presented.

Abstract: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.

Transition metal carbonates (TMCs) with complex composition and robust hybrid structure hold great potential as high-performance electrode materials for lithium-ion batteries (LIBs). However, poor ionic/electronic conductivities and large volume changes of TMCs during lithiation/delithiation processes have hindered their applications. Herein, single-phase MnCo mixed carbonate composites encapsulated by reduced graphene oxide (Mn x Co 1−x CO 3 / RGO), in which Mn and Co species are distributed randomly in one crystal structure, are successfully synthesized through a facial liquid-state method. When evaluated as LIB anodes, the Mn x Co 1−x CO 3 /RGO composites exhibit enhanced electrochemical performance compared with the reference CoCO 3 / RGO and MnCO 3 /RGO. Specifically, the Mn 0.7 Co 0.3 CO 3 /RGO delivers an ultrahigh capacity of 1454 mA h g −1 after 130 cycles at 100 mA g −1 and exhibits an ultralong cycling stability (901 mA h g −1 after 1500 cycles at 2000 mA g −1 ). This is the best lithium storage performance among carbonatebased anodes reported up to date. Such superb performance is attributed to the hybrid structure and enhanced electroconductivity due to the integration of Co and Mn into one crystal structure, which is complemented by electrochemical impedance spectroscopy and density functional theory calculations. The facile synthesis, promising electrochemical results, and scientific understanding of the Mn x Co 1−x CO 3 /RGO provides a design principle and encourages more research on TMCs-based electrodes.