Engineers developing structural ceramics need materials that remain useful when cracks, heat and chemical exposure act together. MAB phases, a family of layered borides, offer several ways to explore that problem. The review "Progress and prospects in MAB phases: A comprehensive review of structure, synthesis, and multifunctional properties" examines how atomic structures and preparation methods influence their mechanical and functional behavior, and follows routes from MAB parents to two-dimensional borides. It was published online in Journal of Advanced Ceramics on 30 September 2026.
In many well-studied aluminum-containing phases, relatively stiff metal-boron units alternate with aluminum-containing regions that deform more easily. Mechanical tests on Fe2AlB2 have observed non-catastrophic fracture, in which the specimen can continue carrying load after local damage. In selected layered MAB ceramics, layer sliding, crack deflection, delamination and crack bridging can dissipate energy as a fracture advances. Their contributions depend on grain structure, preferred grain orientation and loading conditions.
MoAlB illustrates how chemistry can contribute to repairing damage. In one experiment discussed in the review, water quenching reduced a ceramic specimen's bending strength. After heating in air at 1200 °C for four hours, it recovered about 96% of its initial strength. Microscopy and phase analysis identified alumina growing into the cracks. The same oxidation process also consumes material, and protection can fail if the oxide layer becomes damaged.
The team published their work in Journal of Advanced Ceramics on September 30, 2026.
The field's history extends to early molybdenum-aluminum-boron compounds reported in 1942. In 2013, a magnetocaloric effect near room temperature was found in Fe2AlB2, suggesting a route toward magnetic refrigeration. The unified MAB concept followed in 2015 and helped bring these previously separate compounds into a common research field. Work since then has expanded both the range of structures and the questions researchers ask about their performance.
Aluminum-containing structures now sit alongside hexagonal borides and phases with two metals arranged in ordered positions. The review also includes related 211-type MAX borides as a distinct subfamily. These materials differ in their boron arrangements and layer stacking, so a chemical formula alone cannot explain their behavior. Composition, crystal symmetry and metal ordering together provide a more useful starting point for choosing which materials to synthesize and compare.
Computational studies help identify candidate material systems by comparing their energies with those of other elemental or compound phases and assessing lattice vibrations and elastic response. These candidates still need suitable precursors and processing windows, followed by experimental confirmation of composition and phases. The synthesis method should match the intended product. Hot pressing and spark plasma sintering consolidate ceramics; molten-salt and combustion routes can supply product powders or reaction intermediates; flux growth supplies single crystals, while sputtering produces thin films. A rapid reaction step is only part of the process. Comparisons of efficiency and cost also need to include precursor preparation, washing and subsequent densification.
Removing particular elements from a layered parent can create a very different material. For example, researchers removed aluminum and yttrium from an in-plane ordered Mo/Y-based MAB phase and delaminated the product to obtain monolayer Boridene. This two-dimensional boride has ordered metal vacancies and chemical groups on its surface, providing an experimental example for studying how a thin boride's structure affects surface reactions.
Other treatments can leave residual A elements or reconstruct the framework. For example, high-temperature dealloying of Ti2InB2 produces layered TiB with a rearranged crystal structure. Partial etching of MoAlB can leave local thin layers and regions where different layered structures coexist. Partially etched particles, multilayer materials and isolated monolayers therefore need separate characterization. Residual A elements, secondary phases and surface terminations also influence their properties.
Researchers have investigated MAB-derived materials in energy storage, electrocatalysis, sensors and optoelectronic devices. Accessible surfaces, chemical groups and defects can affect ion adsorption, reaction sites and charge transport. One example uses MoAlB-derived sheets to support individual Pt atoms; its catalytic response belongs to that Pt-containing material. Device configuration and test conditions also affect measured performance. Electrolyte, active-material loading, test rate and the mass or area used for normalization all affect comparisons. A sensor retaining its response indicates how it performs under the test conditions. Assessing long-term chemical stability requires following dissolution, oxidation and structural reconstruction.
Further progress requires better control of composition, phases and microstructure, followed by tests that combine temperature, load and environmental exposure. For two-dimensional derivatives, measurements of layer number, residual elements and surface chemistry should accompany functional testing. Collecting these results with preparation conditions in comparable datasets can guide the next synthesis experiment and help identify materials for device or component evaluation.
About the authors
Yihan Liang is a postdoctoral researcher and assistant researcher at Southwest Jiaotong University. Liang's work focuses on the control of microstructure and properties in rapidly sintered ceramics, as well as rapid ceramic synthesis and fabrication.
Yanchun Zhou is a researcher at Suzhou Laboratory. His work focuses on the structural design, preparation and properties of high-temperature and ultrahigh-temperature ceramics and ceramic composites.
Chunfeng Hu is a professor and doctoral supervisor at Southwest Jiaotong University and a member of the editorial board of Journal of Advanced Ceramics.
Siqi Xiang is a postdoctoral researcher at Tsinghua University, supported by the Shuimu Tsinghua Scholar Program.
Funding
This work was supported by the National Natural Science Foundation of China (52472079), Sichuan Science and Technology Program (2025YFHZ0082, 2026NSFSC1227), and Fundamental Research Funds for the Central Universities (2682025CX095).
DOI LINK: 10.26599/JAC.2026.9221386
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen . JAC's 2025 IF is 14, ranking in Top 1 (1/34, Q1) among all journals in "Materials Science, Ceramics" category, and its 2025 CiteScore is 24.6 (6/133) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
