Phase evolution and thermal stability of novel high-entropy (Mo0.2Nb0.2Ta0.2V0.2W0.2)Si2 ceramics

Owing to the high melting points and high-temperature stability, transition-metal disilicides are potential components for aerospace, automotive, and industrial engineering applications. However, unwanted oxidation known as PEST oxidation severely limits their application owing to the formation of volatile transition metal oxides, especially in the temperature range of 500-1000 degrees C. To overcome this problem, a new class of high-entropy disilicides, (Mo0.2Nb0.2Ta0.2V0.2W0.2)Si-2, was selected by first-principles calculations and then successfully fabricated using a hot-pressing sintering technique. Furthermore, the phase evolution, thermal expansion behavior, thermal conductivity, and oxidation behavior were systematically investigated. Compared with MoSi2, (Mo0.2Nb0.2Ta0.2V0.2W0.2)Si-2 possessed a lower thermal conductivity (10.9-14.7 W.m(-1).K-1) at 25-1000 degrees C, higher thermal expansion coefficients (8.6 +/- 1.3(-6) K-1) at 50-1200 degrees C, and especially an excellent thermal stability at 500-1000 degrees C owing to slow diffusion and selective oxidation. This work provides a strong foundation for the synthesis and application of high-entropy disilicides.

Automated summary

Transition-metal disilicides have high potential for aerospace, automotive, and industrial engineering applications due to their high melting points and high-temperature stability. However, the unwanted PEST oxidation limits their use. A new class of high-entropy disilicides was successfully fabricated and showed lower thermal conductivity, higher thermal expansion coefficients, and excellent thermal stability compared to traditional disilicides. This work lays a strong foundation for the synthesis and application of high-entropy disilicides.