Research Progress on Ternary Layered MAB Phases Ceramics and Their Mechanical and Tribological Properties

MAB phase ceramics, a new class of ternary layered transition metal compounds following MAX phase ceramics are widely concerned attributing to their excellent thermal stability and mechanical properties, such as high temperature resistance, oxidation resistance, high strength and high damage tolerance. The nanolaminar structure of MAB phase ceramics, similar to that of the MAX-phase ceramics, endows them with great application potential in solid lubrication fields, especially for high-temperature lubrication. Moreover, two-dimensional nano-MBenes sheets with graphite- or MoS₂-like nanolaminar structures, obtained from etching MAB phase materials, providing a wide range of candidates for friction reduction and wear-resistant additives for composite materials. Currently, experiments have synthesized over 90 MAX phase and 60 MAB phase materials, including bulk, powder, thin film and single crystal forms. The chemical disorder solid solution at M, A, and X/B sites can further expand the family of MAX and MAB phases. Selective solid solution of binary metals at the M site in MAB phases can also yield quaternary layered transition metal borides with out-of-plane or in-plane chemical ordering. Additionally, multi-element solid solution at the M site can produce high-entropy MAB phases, in which high configurational entropy at the M site plays a crucial role in forming multi-element pure phase MAB phases. In the synthesis of MAB phases, inorganic synthesis methods such as powder metallurgy and precursor conversion are generally used. With the concerted efforts of researchers worldwide, several new highlights have emerged in the study of MAB phases, especially in areas such as accident-tolerant materials, high-temperature structural materials and high-temperature lubricating materials, attracting widespread attention. Therefore, controlling the elemental composition and structural morphology of MAB phases will expand the space for optimizing material performance and practical applications. In this paper, ternary layered MAB phase ceramics and their basic structures and preparation methods were introduced, followed by summarizing the current research status and progress of MAB phase ceramics and their 2D MBenes nanomaterials in mechanicsand tribology, involving MoAlB, Fe₂AlB₂, Mn₂AlB₂ and Cr₂AlB₂ systems. On this basis, furthermore, challenges in current research and future directions were proposed. MAB phase materials are currently in the interest-driven frontier research stage. With the continuous discovery of new structures and new compositions, and the maturation of new synthesis methods, the physical and chemical properties of this layered material family are becoming increasingly well-known to researchers.