A novel method of strong and tough Si 3 N 4 ceramic from the particle‐stabilized foam

Abstract The brittleness of Si 3 N 4 ceramics has always limited its wide application. In this paper, Si 3 N 4 ceramics were prepared based on foam. Combining the unique honeycomb structure of the ceramic foams and the self‐toughening mechanism of Si 3 N 4 , the strengthening and toughening of Si 3 N 4 ceramics can be further achieved by adjusting the microstructure of Si 3 N 4 ceramic foams. The powder particles are self‐assembled by particle‐stabilized foaming to form a foam body with a honeycomb structure. It was pretreated at different temperatures (1450–1750°C). The microstructure evolution of foamed ceramics at different pretreatment temperatures and the conversion rate of α‐Si 3 N 4 to β‐Si 3 N 4 at different pretreatment temperatures were explored. Then the foamed ceramics with different microstructures are hot‐press sintered to prepare Si 3 N 4 dense ceramics. The effects of different microstructures of foamed ceramics on the strength and toughness of Si 3 N 4 ceramics were analyzed. The experimental results show that the relative density of Si 3 N 4 ceramics prepared at a particle pretreatment temperature of 1500°C is 97.8%, and its flexural strength and fracture toughness are relatively the highest, which are 1089 ± 60 MPa and 12.9 ± 1.3 MPa m 1/2 , respectively. Compared with the traditional powder hot‐pressing sintering, the improvement is 21% and 33%, respectively. It is shown that this method of preparing Si 3 N 4 ceramics based on foam has the potential to strengthen and toughen Si 3 N 4 ceramics.