Novel porous Si3N4 ceramics prepared by aqueous gelcasting using Si3N4 poly-hollow microspheres as pore-forming agent

In this paper, novel porous Si3N4 ceramics were prepared by aqueous gelcasting using Si3N4 poly-hollow microspheres as pore-forming agent. The effect of Si3N4 poly-hollow microsphere content on the phase composition, microstructure, shrinkage, porosity and mechanical properties of the prepared porous Si3N4 ceramics were investigated. It is found that there is only β-Si3N4 phase in all the prepared porous Si3N4 ceramics. Meanwhile, the SEM results show that the pores in the porous Si3N4 ceramics distribute uniformly, the added Si3N4 poly-hollow microspheres and the basal body contact closely. With the increase of Si3N4 poly-hollow microsphere content, the shrinkage of the porous Si3N4 ceramics decreases gradually, and the porosity of the porous Si3N4 ceramics decreases firstly and then increases. Furthermore, the flexural strength and fracture toughness of the porous Si3N4 ceramics decrease with the increase of the Si3N4 poly-hollow microsphere content.