Cold Isostatic Pressing–Normal Pressure Sintering Behavior of Amorphous Nano-Sized Silicon Nitride Powders

Abstract

The amorphous nano-sized silicon nitride powders were sintered by cold isostatic pressing –normal press sintering method. The sintering additives of Y2O3 and Al2O3 powders with average grain size less than 20nm were prepared by polyacrylamide gel method. Relative density of sintered materials rise and pore size reduce with increasing of cold isostatic pressing. When the pressure is 100MPa, the density is only 48% and average pores size is between 2μm and 20μm which obvious the first particle space. When the pressure is 200MPa, the density is 67% and agglomerated particle size reduce obviously as well as the pores size are between 0.1μm and 1.0μm which appears because of the second particle. Pressed compact with a relative density 74% and average pore size less than 0.5μm reach to a good density state at 300MPa pressure. Sintering material composites with Si2N2O and β-Si3N4 phases, compared with hot press sintering composites, which indicates that increasing of sintering press is conducive to the formation phase Si2N2O. Relative density is above 96% and average pore size is less than 500nm at sintering temperature 1800°C.