Effect of Ta2O5 Addition on Microstructure of Mo5Si3 Particle Reinforced Si3N4 Composite with Grain Boundary Phase of Yb2Si2O7

Abstract

Listen

Translate article

Mo5Si3 particle reinforced Si3N4 composite with crystallized grain boundary phase of Yb2Si2O7 was synthesized in-situ by sintering a green compact that contained Si3N4, MoO3, Ta2O5, and Yb2O3 powders. The reaction between Si3N4, MoO2, Ta2O5, and Yb2O3 at high temperature generated the Mo5Si3 particles, the complex molybdenum and tantalum silicide particles, and the grain boundary phase of Yb2Si2O7 simultaneously. In the Mo5Si3-Yb2Si2O7-Si3N4 composite, most of Mo5Si3 particles residing at the grain boundary phase, and had an average size of 0.18 μm. The addition of Ta2O5 promoted the formation of Mo5Si3 particle in Si3N4 grain and the generation of the Yb2Si2O7 nano-particle in the grain boundary phase. The grain boundary phase and the Si3N4 grains were reinforced by the sub-micrometer sized Mo5Si3 particles and Yb2Si2O7 nano-particles, which improved the strength of Si3N4. The crystallization of grain boundary phase was almost completed by adding the MoO3, Ta2O5, and Yb2O3, while a small amount of amorphous phase and the thin amorphous films were detected from the grain boundary pockets, and the interfaces between the Si3N4, Yb2Si2O7, and Mo5Si3, respectively.