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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 °C (where the density is 85.3%, the flexural strength is 845 MPa, and the fracture toughness is 9.3 MPa·m1/2), 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 β-Si₃N₄ grain distribution more uniform by reducing the porosity.