Synthesis, structure, properties and applications of high-entropy borides

Abstract

High-entropy borides (HEBs), as an emerging branch of high-entropy materials, have become a prominent research frontier in the field of ultra-high-temperature ceramics (UHTCs). The high configuration entropy effect is used to stabilize single-phase solid solution structures, which exhibit comprehensive properties that are difficult to achieve by traditional binary borides. This review aims to systematically summarize the research progress on HEBs, first covering their theoretical predictions and component design based on first-principles methods. Then, some typical systems are described and the main preparation techniques such as arc melting and spark plasma sintering are summarized. The core of this paper is to comprehensively evaluate the outstanding performance characteristics of HEBs, which not only include their exceptional mechanical properties such as ultra-high hardness and excellent fracture toughness, but also delve into their high-temperature friction and wear behavior, as well as their oxidation resistance. Finally, based on their unique performance advantages, the application prospects in extreme working conditions such as aerospace and cutting tools are prospected, and the challenges in this field are pointed out.