Study on the Process of Si_3N_4 Ceramic with High Properties by Gel-casting

Preparation of ceramic slurry with low viscosity and high solid loading is the key process in gel-casting process.The Si3N4 slurry was prepared using TMAH as dispersant in this paper.The influences of pH value,content of dispersant and sintering additives and solid loading on rheological properties of Si3N4 slurry were studied.Mechanical properties of green body and sintered body prepared by gel-casting were investigated.The results showed that the rheological properties of Si3N4 slurry has the best when pH value is 10.5,and the amount of dispersant solution(respect to Si3N4 solid volume) is 6% and sintering additives(wt%) is 10% respectively.According to the optimized processing parameters,the high solid loading(50%) of Si3N4 slurry with good fluidity have been prepared(viscocity100 mPa·s.Flexural strength of green body is 27 MPa after forming.The Si3N4 samples after sintering have excellent mechanical properties with flexural strength of 730 MPa and fracture toughness of 8.8 MPa· m1/2.