酸化タンタルの添加による Yb_2Si_2O_7 粒界相を持つ Mo_5Si_3 粒子強化 Si_3N_4 複合材料の微構造への影響

概要

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Mo_5Si_3 particle reinforced Si_3N_4 composite with crystallized grain boundary phase of Yb_2Si_2O_7 was synthesized in-situ by sintering a green compact that contained Si_3N_4, MoO_3, Ta_2O_5, and Yb_2O_3 powders. The reaction between Si_3N_4, MoO_2, Ta_2O_5, and Yb_2O_3 at high temperature generated the Mo_5Si_3 particles, the complex molybdenum and tantalum silicide particles, and the grain boundary phase of Yb_2Si_2O_7 simultaneously. In the Mo_5Si_3-Yb_2Si_2O_7-Si_3N_4 composite, most of Mo_5Si_3 particles residing at the grain boundary phase, and had an average size of 0.18μm. The addition of Ta_2O_5 promoted the formation of Mo_5Si_3 particle in Si_3N_4 grain and the generation of the Yb_2Si_2O_7 nano-particle in the grain boundary phase. The grain boundary phase and the Si_3N_4 grains were reinforced by the sub-micrometer sized Mo_5Si_3 particles and Yb_2Si_2O_7 nano-particles, which improved the strength of Si_3N_4. The crystallization of grain boundary phase was almost completed by adding the MoO_3, Ta_2O_5, and Yb_2O_3, while a small amount of amorphous phase and the thin amorphous films were detected from the grain boundary pockets, and the interfaces between the Si_3N_4, Yb_2Si_2O_7, and Mo_5Si_3, respectively.
2005-04-01