High performance porous Si_3N_4 ceramics prepared by coated pore-forming agent method

摘要

Coated pore-forming agent method (CPFAM) was introduced to improve the pore-forming agent method (PFAM) for the preparation of porous silicon nitride ceramics. Using SEM in combination with measurements of porosity and ftexural strength, it has been found that the flexural strength of the porous silicon nitride ceramics produced with the CPFAM method is significantly higher than those without the coating process: a 100 percent increase in flexural strength for samples with a porosity of 50 percent . The porous silicon nitride ceramics also have a very low dielectric constant, which is ideal for applications in wave-transmitting systems. The enhanced mechanical strength of the silicon nitride made by the CPFAM method is a result of a more uniform distribution of the spherical pores and the formation of a dense layer of rod-like microstructures near the surface of the pores.