• 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.40 no.3
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• pp.241-248
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• 2003

We controlled the amount of Y$_2$O$_3$additives, 8 mol% and 10 mol%, and the type of carbon pore former, activated carbon and carbon black, to improve the strength of porous NiO-YSZ anode materials for solid oxide fuel ceil. The 3-point flexural strength, porosity and electrical conductivity were evaluated. As a result, the strength of anode materials with the addition of carbon black was markedly improved. The strength of NiO-10 mol%YSZ sintered at relatively higher temperature was higher than that of NiO-8 mol%YSZ materials. The electrical conductivity of NiO-10 mol%YSZ with carbon black was evaluated as much as 10$^2$∼10$^3$S/cm at 700$^{\circ}C$∼1000$^{\circ}C$ in reducing atmosphere.

• Nuclear Engineering and Technology
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• v.34 no.4
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• pp.323-330
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• 2002

Various types of compounds were tested with the aspects of decomposition and formation of residue in a $CO_2$ or 7H$_2$+93$N_2$ atmosphere. The evaporation temperature range of each compound was determined from thermogravimetric curve. Decomposition of dicarbon amide, stearic acid, acrowax and zinc stearate was studied by thermogravimetry in $CO_2$ or in 7H$_2$+93$N_2$ atmosphere. All compounds were decomposed in $CO_2$ atmosphere at lower than 40$0^{\circ}C$, but the residue, ZnO remained for zinc stearate. ZnO did not decompose in $CO_2$ atmosphere up to 130$0^{\circ}C$, but reduced into Zn metal and disappeared in the temperature range of $600^{\circ}C$ to 120$0^{\circ}C$ in 7H$_2$+93$N_2$ atmosphere. The effect of residue, which trapped in closed pores of sintered pellet, on the thermal stability was studied using the resintering test at 1$700^{\circ}C$ in 7H$_2$+93$N_2$ atmosphere. In the case of oxidative sintered pellet with admixing zinc stearate, the cavity formation accompanied with a density drop after resintering is due to the pressure of the Zn gases trapped in the isolated pores.