High toughness Si3N4f/BNi fibrous monolithic ceramic: Bionic structure design via the uniaxially aligned Si3N4 fibers with BN interfaces

In this work, bionic structure design was introduced to optimize the mechanical properties of ceramics using Si3N4 fibers and BN interfaces. It was shown that Si3N4f/BNi fibrous monolithic ceramic possessed outstanding fracture toughness with the KIC value of 13.06 MPa·m1/2 while retaining the flexural strength of 603.59 MPa. This indicated that the BN interfaces extended the crack propagation path and improved the fracture toughness of ceramics. Meanwhile, the densification of ceramics was efficiently promoted by the constant application of pressure starting from room temperature during the sintering process, with a density of up to 3.18 g/cm3. An innovative fiber inclusion model was first established to calculate the residual stress, and predict the flexural strength considering residual stress. This work offers new prospects for the synchronous realization of high strength and toughness in Si3N4 ceramics and for predicting the strength of fibrous monolithic ceramics.