How does crack bridging change at cryogenic temperatures?

The crack bridging behaviors of silicon nitride (Si₃N₄) ceramics based on the advancing cracks have been evaluated at cryogenic temperatures in contrast with those happened at ambient temperatures. R-Curve behavior of Si₃N₄ ceramics was determined to compare the cumulative effect of bridging at 77 and 293 K. The detailed changes in crack morphologies and crack opening displacement profiles at different temperatures were investigated. The bridging stress maps around a bridging ligament were recorded by in situ Raman spectroscopy. It was found that the highest tensile stress measured at 77 K (~1.0 GPa) is much higher than that at 293 K (~0.7 GPa). The experimental results suggested that Si₃N₄ ceramics at cryogenic temperatures possessed a higher probability of crack bridging with a higher closing force, which could make them a promising candidate for cryogenic applications.