Mechanism of toughening and strengthening of Si3N4／SiC／ZrO2 nanocomposites

The Si3N4-based nanocomposites reinforced with micro ZrO2 and nano SiC particles were prepared by polarity dispersant and vacuum-sintering technology. The mechanical properties and microstructures were tested. The results show that appropriate amount of micro ZrO2 and nano SiC particles, not only enhance the microhardness, but also block the excessively growth of β-Si3 N4 and β-Si3N4 grains, so they finally all grow up to uniformly pole-shaped grains. This process is similar to the strengthening and toughening mechanism of grain whiskers and makes a remarkable improvement on the toughness. Compared with Si3N4 ceramic, the toughness of Si3N4/SiC/ZrO2 nanocomposites are increased from 6.2 MPa · m1/2 to 11 MPa · m1/2.