Synthesis, Structure, Properties and Applications of High-Entropy Borides
High-entropy borides (HEBs) represent an emerging class of high-entropy materials that have garnered significant attention as ultra-high-temperature ceramics (UHTCs). By leveraging the high configuration entropy effect, HEBs stabilize single-phase solid solutions, exhibiting a suite of properties unattainable in traditional binary borides. This review systematically consolidates research progress on HEBs, beginning with theoretical predictions and component design via first-principles methods. It then details typical HEB systems and principal synthesis techniques, including arc melting and spark plasma sintering. The core analysis evaluates the outstanding performance of HEBs, emphasizing exceptional mechanical properties such as ultra-high hardness and excellent fracture toughness, alongside high-temperature friction and wear behavior, and oxidation resistance. Finally, the review outlines application prospects in extreme environments like aerospace and cutting tools, while also addressing current challenges. The paper underscores the potential of HEBs to overcome the hardness-toughness trade-off inherent in conventional ceramics, driven by strong metal-boron hybridization. This comprehensive overview positions HEBs as promising candidates for next-generation thermal and mechanical protection systems, with future research directions focusing on optimizing compositions and processing to tailor properties for specific applications.