J. Korean Ceram. Soc. > Volume 50(3); 2013 > Article
 Journal of the Korean Ceramic Society 2013;50(3): 218. doi: https://doi.org/10.4191/kcers.2013.50.3.218
 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 Science1Materials Science and Technology Division, Oak Ridge National Laboratory ABSTRACT 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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