fabrication and characterization of porous silicon nitride bodies through starch consolidation casting and pressureless sintering

Porous si3n4 ceramics were prepared by a novel colloidal method called starch consolidation casting. in this method, starch plays both pore-forming and consolidating roles. the effect of starch content on the viscosity of si3n4/starch slurry was investigated in this research. rotational rheometer was used to study the rheological behavior of si3n4/starch slurry. green samples with 5 to 10mpa flexural strength were shaped by casting slurries in a nonporous mold and held at 80c for 120min. afterward the samples burned-out and sintered at 1650c for 4h in an air furnace under a nitride powder bed condition. thermal behavior, phase evolution, and microstructure of sintered samples were characterized through thermogravimetric analysis (tga), x-ray diffraction (xrd), and scanning electron microscope (sem). the xrd results showed that β−si3n4 was the main phase in the sintered samples. the β−si3n4 phase content was as much as 90wt% in the sintered samples. finally, a porous silicon nitride sample was successfully produced with 44 vol% open porosity and flexural strength of 108.9mpa through the starch consolidation casting method.