High performance and dense Si3N4 ceramic prepared by gelcasting combined with reaction re-sintering method

Abstract

In this study, Si powder was used as raw material, Si3N4 powder as a diluent, Al2O3, MgO, Y2O3, and La2O3 as sintering additives to prepare Si3N4 ceramic with excellent properties using gelcasting and reaction re-sintering method. When the solid content of the slurry is 57.3 %, the viscosity is less than 1 Pa · s during the gelcasting process. After the reaction re-sintering, the sintered body of Si3N4 exhibited a bulk density of 3.15 ± 0.05 g/cm3, a relative density of 96 ± 1 %, open porosity of 5.7 %, bending strength of 610 ± 20 MPa, elastic modulus of 235 ± 10 GPa, thermal conductivity of 48 ± 5 W/(m·K), and a linear shrinkage rate of 12–13 %. These parameters indicate that Si3N4 ceramic possesses outstanding mechanical properties and thermal conductivity.