How does pore-induced crack change as temperatures decrease from 293 K to 77 K?

The pore-induced cracks in pressureless-sintered SiC ceramics have been investigated at ambient and cryogenic temperatures. The Weibull plots of flexural strength were determined to compare the effects of pore-induced cracks on fracture behavior at 77 K and 293 K. The stress field near crack tip was investigated based on the microstructure of sintered SiC. The measurements of lattice constants of single crystal SiC were carried out by in situ X-ray diffraction. It was found that the effect of defect-induced crack on fracture was diminished at cryogenic temperatures, owing to the decreases of cracks' effective size and increases of propagate resistance. The improved fracture reliability and enhanced flexural strength of SiC ceramics facilitate their applications in space-based reflectors.