Preparation of bulk Si3N4 from tape casting and lamination

Si3N4 samples were prepared by tape casting, laminating and hot pressing (HP)/spark plasma sintering (SPS). Initially, the as-received Si3N4 powders were chemically treated to improve the dispersion in aqueous media. After surface treatment, a decrease in zeta potential was observed in the basic region. Rheological measurements showed that 40 vol.% Si3N4 slips exhibited a well deflocculated state in the presence of the sintering additives. After the addition of binder and plasticizer, Si3N4 slurries exhibited a shear thinning behavior. The dried green sheets were smooth and homogeneous on both sides. The Si3N4 samples were densified by HP and SPS. A good homogeneity is observed and no single layers can be distinguished in the fracture surface. The mechanical properties were also studied.