Study of the Mechanical Properties and Toughening Mechanism of Nano-NbC Particles Toughened Si3N4-Based Ceramics

In this article, nano-NbC particles toughened Si3N4-based ceramics were prepared by injection moulding and their mechanical properties along with toughening mechanism were studied. An increase of nano-NbC content, gradually homogenizes microstructure of the Si3N4-based ceramics along with increase in its density. However, the fracture toughness and flexural strength first increases and then decreases. The Si3N4-based ceramics demonstrate good comprehensive properties at the 15 wt% nano-NbC content and sintering temperature of 1550 degrees C (where the density is 85.3%, the flexural strength is 845 MPa, and the fracture toughness is 9.3 MPa . m(1/2)), Backscattered electron imaging shows that nano-NbC particles can be well dispersed in the Si3N4 ceramic matrix by injection moulding and ceramics are toughened by crack deflection and microcracking effects. It was also found that increasing sintering temperature makes the beta-Si3N4 grain distribution more uniform by reducing the porosity.