Figure 4.

SEM images of intaglio surfaces after interfacial fracture: (A) Illustration of the failure modes as classified in this study: I, crack propagates within the cement layer; II, crack propagates between the cement and ceramic at the same interface; III, crack starts at one interface and goes to the other across the cement thickness; and IV, crack kinks between the 2 interfaces. (B) For the sol-gel silica infiltration, the coating was not uniform. The high-magnification image shows silica islands where residual cement is still bonded after fracture.