High-Performance MoSi2-20 mol % Mo5Si3 Composite Ceramics: Sintering Preparation, Experimental Characterization, and Theoretical Calculation

Molybdenum disilicide ceramics have become highly promising high-temperature structural materials due to their high melting point and excellent high-temperature oxidation resistance, but their room-temperature brittleness limits their broader application. Therefore, this study aims to improve the physical and mechanical properties of MoSi2 by incorporating reinforcing phases and employing high-temperature and high-pressure sintering methods. High-density MoSi2-20 mol % Mo5Si3 composite ceramic samples were prepared by a sintering process at a constant pressure of 4.5 GPa over the temperature range of 1100–1300 °C. Characterization results showed that the composite ceramic samples exhibited high relative density. Its maximum measured values of Vickers hardness and fracture toughness are 15.358 ± 0.187 GPa and 6.497 ± 0.424 MPa·m1/2, respectively, both superior to most molybdenum silicide-based materials prepared by conventional methods. It also possesses excellent heat/electrical transfer performance. Notably, the sintered samples showed no significant mass gain in an air atmosphere at 1500 °C, exhibiting excellent high-temperature oxidation resistance. The underlying mechanism is revealed by ab initio molecular dynamics simulations. This study provides a new route for preparing high-performance molybdenum silicide-based composite ceramics and lays a theoretical and experimental foundation for their application in extreme environments, such as hot-section components in aerospace engines and missile nozzles.