• Proceedings of the Korean Ceranic Society Conference
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• 2004.04b
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• pp.45.1-45.1
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• 2004

• Proceedings of the Materials Research Society of Korea Conference
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• 1997.10a
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• pp.170-170
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• 1997

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.04a
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• pp.39-40
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• 2006

• Journal of the Korean Ceramic Society
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• v.43 no.8 s.291
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• pp.472-478
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• 2006

The effect of compositional and processing variables on a nitriding reaction of silicon powder compact and subsequent post sintering of RBSN (Reaction-Bonded Silicon Nitride) was investigated. The addition of a nitriding agent enhanced nitridation rate substantially at low temperatures, while the formation of a liquid phase between the nitriding agent and the sintering additives at a high temperature caused a negative catalyst effect resulting in a decreased nitridation rate. A liquid phase formed by solely an additive, however, was found to have no effect on nitridation for the additive amount used in this research. The original site of a decomposing pore former was loosely filled by a reaction product ($Si_3N_4$), which provided a specimen with nitriding gas passage. For SRBSN (Sintered RBSN) specimens of high porosity, only a marginal dimensional change was measured after post sintering. Its engineering implication for near-net shaping ability is discussed.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.622-627
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• 2016

The effects of the debinding atmosphere on the properties of sintered reaction-bonded $Si_3N_4$ (SRBSN) ceramics prepared by tape casting method were investigated. Si green tape was produced from Si slurry of Si powder, using 11.5 wt% polyvinyl butyral as the organic binder and 35 wt% dioctyl phthalate as the plasticizer. The debinding process was conducted in air and $N_2$ atmospheres at $400^{\circ}C$ for 4 h. The nitridation process of the debinded Si specimens was performed at $1450^{\circ}C$, followed by sintering at $1850^{\circ}C$ and 20 MPa. The results revealed that the debinding atmosphere had a significant effect on $Si_3N_4$ densification and thermal conductivity. Owing to the higher sintered density and larger grain size, the thermal conductivity of $Si_3N_4$ specimens debinded in air was higher than that of the samples debinded in $N_2$. Thus, debinding in air could be suitable for the manufacture of high-performance SRBSN substrates by tape casting.

• Journal of the Korean Ceramic Society
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• v.45 no.11
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• pp.675-680
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• 2008

The effect of pore former content on both porosity and pore structure was investigated for porous sintered reaction-bonded silicon nitrides (SRBSNs). A spherical PMMA with $d_{50}=8{\mu}m$ was employed as a pore-former. Its amount ranged from 0 to 30 part. Porous SRBSNs were fabricated by post-sintering at various temperatures where the porosity was controlled at $12{\sim}52%$. The strong tendency of increasing porosity with PMMA content and decreasing porosity with sintering temperature was observed. Measured pore-channel diameter increased $(0.3{\rightarrow}1.1{\mu}m)$ with both PMMA content and sintering temperature.

• Journal of the Korean Ceramic Society
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• v.44 no.7
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• pp.354-357
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• 2007

The nitriding and post-sintering behavior of silicon powder compact containing sintering additives of 2.3 wt% and 7 wt% were investigated in this study. Regardless of the liquid phase content, elongated large grains of a typical morphology evolved in the post-sintered specimens. Phase analysis revealed a complete phase transformation into ${\beta}-Si_3N_4$ in both porous systems. Oxynitride second phases (mellilite) precipitated in the latter, while those were free in the former containing less amount of liquid phase. The post-sintering condition that yielded a favorable microstructure for a filter application was achieved when the specimens were soaked at $1800^{\circ}C$ for 2 h. It was found that the thermal conductivity of porous $Si_3N_4$ ceramics is dominated by the porosity more than this factor is influenced by the addition of $Al_2O_3$.

• Journal of the Korean Ceramic Society
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• v.50 no.3
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• pp.218-225
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• 2013

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.