LIU Ya, LI Ruifeng, YE Fei, GUO Lucun

(College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu 210009, China)

Abstract:The various rodlike β-Si3N4 seeds were prepared by pressureless sintering at 1750℃ for 1 hour, 1.5 hours and 2 hours.The effects of seed crystal size on the mechanical properties and microstructure of silicon nitride ceramics were investigated. The experimental results showed that the fracture toughness of silicon nitride was improved significantly with the addition of the seeds, while the relative density and bending strength were decreased slightly. As the length and the aspect ratio of seeds were 4.51μm and 5.71, respectively, the optimum toughening efficiency was obtained. In addition, the fracture toughness initially increased and then decreased with the increasing of seeds amount. 

Key words:silicon nitride; seeds; aspect ratio; mechanical properties; microstructure