Porous Si_3N_4 Fabricated Using Benzoic Acid as Pore-Forming Agent

摘要

In this study, porous Si_3N_4 ceramics with interconnected pores were prepared by cold isostatic pressing using benzoic acid as a pore-foring agent. The pore-forming agent of green bodies were sublimation rapidly below 200°C without carbon remained. Mechanical Properties were tested by universal testing machine, and the microstructures of the specimen were observed by scanning electron microscopy (FEI Sirion 200). The resulting shows, many fibrous β-Si_3N_4 grains grown from the internal wall of the round pores, and the porous distribution uniform in the matrix. By changing the content of benzoic acid, the silicon nitride ceramic with different porosity was fabricated. As the acid content decreased from 15wt% to zero, the porosities decreased from 57.6% to 48.0%, flexural strength increased from 36.8MPa to 141.2MPa. Both the grains and suitable interfacial bonding strength contribute to the high fracture strength.