In-situ observation of crack propagation in silicon nitride ceramics

Using the four point bending inside scanning electron microscope (SEM), the in-situ visualization of crack propagation in silicon nitride ceramic under monotonic and cyclic loading was performed with notched specimens of prismatic shape. In the monotonic loading experiment the study focused on the visualization of inter-vs. trans-granular crack propagation and on the analysis of the material resistance to cracking in terms of R-curve. In the cyclic loading experiment the test was done under high load regime, sufficient for crack initiation and visible propagation within few cycles.