High-Entropy Ceramics Diborides for Hypersonic Applications

High-entropy ceramics diborides (HEBs) is a new series of high-entropy materials (HEMs), with excellent ultra-high temperature stability and ablation resistance. HEBs possess ultra-high melting point, lower thermal conductivity and promoted mechanical properties compared with current ceramics, which can meet the requirement of hypersonic vehicles, especially the local hot spots such as sharp leading edge and combustion chamber. Based on the crystal structure, the designation, the preparation methods and properties of HEBs, the research progress of HEBs is detailed introduced. The quasi-2D hexagonal crystal structure entrusts the excellent properties of HEBs. Through several preparation methods such as spark plasma sintering (SPS) and hot pressing, not only dense bulk materials but porous light coatings can also be processed. Based on the characterization results, HEBs usually own ultra-high hardness and strength, while their toughness is in urge need to promote. Moreover, the porous HEBs structure can efficiently decrease the thermal conductivity, which may play a significant role in the hypersonic applications.