| Densification of Reaction Bonded Silicon Nitride with the Addition of Fine Si Powder - Effects on the Sinterability and Mechanical Properties |
| Sea-Hoon Lee, Chun-Rae Cho, Young-Jo Park, Jae-Woong Ko, Hai-Doo Kim, Hua-Tay Lin1, Paul Becher1 |
Engineering Ceramics Research Group, Korea Institute of Materials Science
1Materials Science and Technology Division, Oak Ridge National Laboratory |
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| ABSTRACT |
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The densification behavior and strength of sintered reaction bonded silicon nitrides (SRBSN) that contain $Lu_2O_3-SiO_2$ additives were improved by the addition of fine Si powder. Dense specimens (relative density: 99.5%) were obtained by gas-pressure sintering (GPS) at $1850^{circ}C$ through the addition of fine Si. In contrast, the densification of conventional specimens did not complete at $1950^{circ}C$. The fine Si decreased the onset temperature of shrinkage and increased the shrinkage rate because the additive helped the compaction of green bodies and induced the formation of fine $Si_3N_4$ particles after nitridation and sintering at and above $1600^{circ}C$. The amount of residual $SiO_2$ within the specimens was not strongly affected by adding fine Si powder because most of the $SiO_2$ layer that had formed on the fine Si particles decomposed during nitridation. The maximum strength and fracture toughness of the specimens were 991 MPa and $8.0MPa{cdot}m^{1/2}$, respectively. |
| Key words:
Reaction bonded silicon nitride, Gas pressure sintering, $Lu_2O_3$, Microstructure |
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