Si₃N₄-SiC_w composites as structural materials for cryogenic application

In an effort to enhance the application in a cryogenic serving environment, the mechanical properties of Si₃N₄-SiC_w composites measured at different temperatures are investigated for the first time. The temperature-dependent increase in flexural strength is accompanied by a substantial increase in fracture toughness with the temperature decrease from 293 K to 77 K. The fracture toughness of Si₃N₄-SiC_w composites measured at 77 K increases obviously, which is ~41% higher than that at 293 K. Also, the effect of residual stress on the toughness and fracture mode is discussed by the theoretical calculation and analysis. At cryogenic temperatures, the toughnening effect of SiC whiskers is increased, and Si₃N₄-SiC_w composites could be a promising material for applications in cryogenic environments.