Mechanical properties of fibrous monolithic Si₃N₄ /BN ceramics with different cell boundary thicknesses

Fibrous Si₃N₄/BN monoliths with various cell boundary thickness were fabricated by hot-pressing. The extruded Si₃N₄ polymer was dip-coated with the BN-containing slurry with a different BN concentration. A cell boundary thickness increase up to 42 μm by adjusting the BN concentration from 0 to 25 wt.% in the slurry, and this cell boundary thickness was found to play an important role in determining the fracture behavior of the fibrous monoliths. On increasing cell boundary thickness, the flexural strength decreased, but the apparent work-of-fracture and toughness increased remarkably due to the extensive crack interactions with weak cell boundaries. This is related to the change in stored energy before fracture initiation and in interfacial fracture resistance.