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고상반응에 의하여 제조된 Li<sub>2</sub>ZrO<sub>3</sub>의 이산화탄소 흡수 및 소결 특성
우상국,이시우,유지행,Woo, Sang-Kuk,Lee, Shi-Woo,Yu, Ji-Haeng 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.5
We synthesized lithium zirconate using solid-state reaction and analyzed thermal properties (TG/DTA) of starting materials and the synthesized one. When $Li_2ZrO_3$ powder was exposed to $CO_2$ environment at $500^{\circ}C$, 93% of the theoretical absorption weight was gained within 280 min with fairly high sorption rate. Almost all the absorbed $CO_2$ was generated by heating the sample to $800^{\circ}C$. We also investigated densification behavior of $Li_2ZrO_3$ under $CO_2$ environment. By sintering $Li_2ZrO_3$ at $760^{\circ}C$ using 2-step process, we obtained dense product, composed mainly of $Li_2ZrO_3\;and\;ZrO_2$, with relative density of 92%.
페놀수지 탄화 코팅법을 이용한 섬유강화 복합재료 계면 형성에 관한 연구
김세영,우상국,한인섭,Kim, Se-Young,Woo, Sang-Kuk,Han, In-Sub 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.3
The novel carbon coating process for interlayer of fiber reinforced ceramic composites between fiber and matrix was performed by carbonizing phenolic resin solution that coated on fiber surface in $N_2$ atmosphere at $600^{\circ}C$ to improve the strength and fracture toughness of CMC(ceramic matrix composite). 160 nm carbon layer was coated on fiber surface with 5 vol% of phenolic resin solution. Since the process temperature ($600^{\circ}C$) is lower than chemical vapor deposition($900{\sim}1000^{\circ}C$), the strength and toughness could be preserved. Furthermore the coating thickness uniformity was improved to 8% of deviation along the stacking sequence. Therefore, prevention from fiber degradation during coating process and controlling coating thickness uniformity along the preform depth were achieved by coating with phenolic resin carbonizing method.
Gel-Casting 및 마이크로파 기상반응소결에 의한 질화규소 세라믹 제조에 대한 연구(I) : Gel-Casting에 의한 실리콘 성형체의 제조
배강,우상국,한인섭,서두원,Bai, Kang,Woo, Sang-Kuk,Han, In-Sub,Seo, Doo-Won 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.5
By gel-casting, the silicon-polymer green bodies were prepared for silicon nitride ceramics, sintered by microwave gas phase reaction. Considering the viscosity and the idle time of slurries, we decided the operational conditions of related processes, and the optimum concentrations of raw materials powders, organic monomers, cross-linker, dispersant, initiator, and catalyst. So we could get the machinable green bodies, having about 50 MPa of bending strength without cracks by selecting drying conditions carefully.
액상 Ni/Si/Co 침투에 의한 반응결합 TiC 복합체의 치밀화
한인섭,우상국,배강,홍기석,서두원,정윤중,Han, In-Sub,Woo, Sang-Kuk,Bai, Kang,Hong, Ki-Suk,Seo, Doo-Won,Chung, Yoon-Jung 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.10
The reaction-bonded TiC-Ni/Si/Co composites were prepared by the melt infiltration of Co, Si, and Ni me-tal into the TiC preforms. The miocrostructure reaction composition and mechanical properties were in-vestigated. In the case of the melt infiltrated with Co and Ni TiC grain shape was changed from angular to spherical shape with the average grain size of ∼5$\mu\textrm{m}$. In the case of the melt infiltrated with Co/Si or Ni/Si, Si was reacted with TiC particles and formed SiC particles. The bending strength of both specimens which have atomic ratio of 3 were 710 MPa and 515 MPa respectively. In the case of the melt infiltrated with Ni/Si/Co,. nonstoichiometric TiC was formed and its bending strength decreased to 420 MPa.
기공형성제 함량이 다공질 Mullite-Bonded SiC 세라믹스의 미세구조와 강도에 미치는 영향
최영훈,김영욱,우상국,한인섭,Choi, Young-Hoon,Kim, Young-Wook,Woo, Sang-Kuk,Han, In-Sub 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.6
Porous mullite-bonded SiC (MBSC) ceramics were fabricated at temperatures ranging from 1400 to $1500^{\circ}C$ for 2 h using silicon carbide (SiC), alumina ($Al_2O_3$), strontium oxide (SrO), and poly (methyl methacrylate-coethylene glycol dimethacrylate) (PMMA) microbeads. The effect of template content on porosity, pore morphology, and flexural strength were investigated. The porosity increased with increasing the template content at the same sintering temperature. The flexural strength showed maximum after sintering at $1450^{\circ}C$/2 h for all specimens due to small pores and dense strut. By controlling the template content and sintering temperature, it was possible to produce porous MBSC ceramics with porosities ranging from 30% to 54%. A maximum flexural strength of ~51MPa was obtained at 30% porosity when no template were used and specimens sintered at $1450^{\circ}C$/2 h.
Si:C Ratio가 다공질 Self-Bonded SiC 세라믹스의 기공율과 곡강도에 미치는 영향
임광영,김영욱,우상국,한인섭,Lim, Kwang-Young,Kim, Young-Wook,Woo, Sang-Kuk,Han, In-Sub 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.5
Porous self-bonded silicon carbide (SiC) ceramics were fabricated at temperatures ranging from 1750 to $1850^{\circ}C$ using SiC, silicon (Si), and carbon (C) powders as starting materials. The effect of the Si:C ratio on porosity and strength was investigated as a function of sintering temperature. It was possible to produce self-bonded SiC ceramics with porosities ranging from 36% to 43%. The porous ceramics showed a maximal porosity when the Si:C ratio was 2:1 regardless of the sintering temperature. In contrast, the maximum strength was obtained when the ratio was 5:1.
알루미늄 첨가가 다공질 Self-Bonded SiC 세라믹스의 기공률과 꺾임강도에 미치는 영향
임광영,김영욱,우상국,한인섭,Lim, Kwang-Young,Kim, Young-Wook,Woo, Sang-Kuk,Han, In-Sub 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.5
Porous self-bonded silicon carbide (SBSC) ceramics were fabricated at temperatures ranging from 1750 to $1850^{\circ}C$ using SiC, Si, C as starting materials and Al as an optional sintering additive. The effect of Al addition on the porosity and strength of the porous SBSC ceramics were investigated as functions of sintering temperature and Si:C ratio. The porosity increased with decreasing the Si:C ratio and increasing the sintering temperature. It was possible to fabricate SBSC ceramics with porosities ranging from 37% to 44% by adjusting the Si:C ratio and the sintering temperature. Addition of Al additive promoted densification and necking between SiC grains, resulting in improved strength. Typical flexural strengths of SBSC ceramics with and without Al addition were 44 MPa and 34MPa, respectively.
Dual Phase 전도성 CO<sub>2</sub> 분리막: 메커니즘, 미세구조 및 전기전도도
이시우,유지행,우상국,Lee, Shi-Woo,Yu, Ji-Haeng,Woo, Sang-Kuk 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.8
Novel conductive $CO_2$ membranes composed of dual phases, molten carbonates and electronic conducting ceramics, were investigated. As the microstructure control of electronic conducting ceramic supports is extremely important to keep the molten carbonates stable in the membranes by a capillary force applied by the pore structure of the supports, we have scrutinized the microstructure of the electronic conducting supports utilizing microscopic images and gas permeability measurement. From the evaluation of the electrical conductivities of the molten carbonates and the electronic conducting ceramic supports, we found that the ionic conductivity of the molten carbonates could determine $CO_2$ flux through the dual phase membranes if the surface exchange rate were relatively high enough.
Spin-coating 공정에 의해 제조된 음극 지지형 고체산화물 연료전지
유지행,이희락,우상국,Yu, Ji-Haeng,Lee, Hee-Lak,Woo, Sang-Kuk 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.12
NiO-YSZ anode-supported single cell was prepared by spin-coating YSZ and LSM slurries as electrolyte and cathode, respectively. Dense YSZ electrolyte film was successfully prepared on the porous NiO-YSZ anode substrate by tuning pre-sintering temperature of NiO-YSZ and co-firing temperature. The thickness of YSZ film was controlled by the solid content of slurry and coating cycles. The experimental conditions affecting on the thickness of YSZ film was discussed. Single cells with the active electrode area ${\sim}0.8\;cm^2$ were prepared by spin-coating the cathode layers of LSM-YSZ mixture and LSM consequently as well. The effects of the pre-sintering temperature and thus the microstructure of NiO-YSZ substrate on the current-voltage characteristics of co-fired cell were investigated.
탄소 원료가 다공질 Self-Bonded SiC (SBSC) 세라믹스의 기공율과 곡강도에 미치는 영향
임광영,김영욱,우상국,한인섭,Lim, Kwang-Young,Kim, Young-Wook,Woo, Sang-Kuk,Han, In-Sub 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.7
Porous self-bonded silicon carbide (SBSC) ceramics were fabricated at temperatures ranging from 1700 to $1850^{\circ}C$ using SiC, silicon (Si), and three different carbon (C) sources, including carbon black, phenol resin, and xylene. The effects of the Si:C ratio and carbon source on porosity and strength were investigated as a function of sintering temperature. Porous SBSC ceramics fabricated from phenol resin showed higher porosity than the others. In contrast, porous SBSC ceramics fabricated from carbon black showed better strength than the others. Regardless of the carbon source, the porosity increased with decreasing the Si:C ratio whereas the strength increased with increasing the Si:C ratio.