• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.107-115
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• 1999

Microstructural variation and strengthening effects with lamination methods of alumina fiber-reinforced ${\gamma}$-LiAlO2 matrixes for Molten Carbonate Fuel Cell(MCFC) were studied. The porosities of all matrix laminated by hot-pressing of two green sheets under 1 kg/$\textrm{cm}^2$ at 45$^{\circ}C$ for 1 min and by double-casting which the second layer cast on the first green sheet dried for 3.5h were more than 50%. The strength of the Al2O3 fiber-reinforced matrix prepared by lamination was enhanced by 70% in comparison with the non-laminated matrix (115 gf/$\textrm{mm}^2$) and the strength-directionality due to fiber-orientation also could be removed. The strength of matrixes laminated by triple-casting was higher than that of the double-cast matrix, but triple-cast matrix showed the directionality with the casting direction, and furthermore its porosity was less than 50%. Although the strength of matrixes laminated by double-casting (195 gf/$\textrm{mm}^2$) is slightly less than that of matrixes laminated by hot-pressing (212 gf/$\textrm{mm}^2$), the double-casting method was evaluated to be more efficient laminating process in MCFC matrix processing.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.233-233
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• 2003

용융탄산염형 연료전지의 성능과 수명은 매트릭스의 기계적 강도, 즉 균열발생과 미세구조 변화에 크게 좌우되고 있다. 매트릭스의 강도 증진은 거대입자를 분산 시키거나 A1$_2$O$_3$ 화이버를 분산시켜 이루어지고 있으며, 그 중 $Al_2$O$_3$ 화이버를 사용하는 경우에는 매트릭스 강화효과에 매우 유리하지만 지금까지 사용한 A1$_2$O$_3$ 화이버가 매우 고가이기 때문에 저가의 A1$_2$O$_3$ 화이버 검토가 요구되고 있다. 본 연구에서는 경쟁력 있는 매트릭스 개발을 목적으로 저순도 및 고순도의 상용 A1$_2$O$_3$ 화이버를 첨가한 매트릭스를 제조하여 미세구조와 강도증진 효과 그리고 단위전지 운전성능을 비교분석 하였다. 실험에 사용한 저순도 A1$_2$O$_3$ 화이버의 길이와 직경은 각각 200 $\mu\textrm{m}$ 와 3 $\mu\textrm{m}$ 이었으며, 고순도 A1$_2$O$_3$ 화이버는 3000 $\mu\textrm{m}$ 와 10 $\mu\textrm{m}$ 이었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.675-689
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• 2019

Development of smart construction materials with both self-strain and self-damage sensing capacities is still difficult because of little information about the self-damage sensing source. Herein, we investigate the effects of the matrix strength, fiber geometry, and fiber content on the electrical resistivity of steel-fiber-reinforced cement composites by multi-fiber pullout testing combined with electrical resistivity measurements. The results reveal that the electrical resistivity of steel-fiber-reinforced cement composites clearly decreased during fiber-matrix debonding. A higher fiber-matrix interfacial bonding generally leads to a higher reduction in the electrical resistivity of the composite during fiber debonding due to the change in high electrical resistivity phase at the fiber-matrix interface. Higher matrix strengths, brass-coated steel fibers, and deformed steel fibers generally produced higher interfacial bond strengths and, consequently, a greater reduction in electrical resistivity during fiber debonding.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.2
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• pp.143-149
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• 2012

용융탄산염 연료전지 상용화를 위해서 40,000 시간이상 장기 운전이 가능해야 한다. 장기운전을 위해 크랙 발생이 적고 기계적 강도가 높은 강화 매트릭스의 개발이 절실히 요구되고 있다. 본 연구에서는 $LiAlO_2$에 알루미늄 나노입자를 첨가하여 매트릭스의 기계적 강도를 향상시키는 연구를 수행하였다. 나노 알루미늄 첨가 $LiAlO_2$ 그린 시트를 수소 분위기에서 열처리한 결과, 공기 분위기에서 열처리한 매트릭스에 비해 기계적 강도가 1.5배 증가함을 확인하였다. 이는 환원분위기에서 열처리를 할 경우, 알루미늄의 입자간의 소결으로 인한 neck이 형성 되어 $LiAlO_2$ 입자 간에 다리를 만들어주는 효과가 나타나 매트릭스의 기계적 강도가 크게 증진되었으리라 판단된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.41-50
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• 2014

This study evaluated the bonding property of fiber and flexural behavior of fiber reinforced concrete. Amorphous steel fiber, hooked steel fiber and polyamide fiber was used for evaluation of bonding property and flexural behavior. As a result, the hooked steel fiber was pulled out from matrix when peak stress. However amorphous steel fiber occurred shear failure because bonding strength between fiber and matrix was higher than tensile strength of fiber. Polyamide fibers occurred significantly displacement to peak stress because of elongation of fiber. After that peak stress, fiber was cut off. Amorphous steel fiber reinforced concrete had a greater maximum flexural load compared with hooked steel fiber reinforced concrete because bonding performance between fiber and matrix was high and mixed population of fiber was many. However flexural stress was rapidly reduced in load-deflection curve because of shear failure of fiber. Flexural stress of hooked steel fiber reinforced concrete was slowly reduced because fiber was pulled out from the matrix. In the case of polyamide fiber reinforced concrete, flexural stress was rapidly lowered because of elongation of fiber. However flexural stress was increased again because of bonding property between polyamide fiber and matrix. The pull-out properties of the fiber and matrix has effect on the deformation capacity and flexural strength of fiber reinforced concrete.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.303-313
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• 1997

To enhance the strength and formability of MCFC matrixes, alumina/${\gamma}$-LiAlO2 fiber-reinforced ${\gamma}$-LiAlO2 ma-trixes have been investigated. The MCFC matrixes with the thickness of 500~600 ${\mu}{\textrm}{m}$ were prepared by tape-casting of the slurry containing 10~30wt% fibers, followed by heat-treating up to $650^{\circ}C$. The porosity of fi-ber-reinforced matrixes decreased with the content of fibers, while the appropriate porosity(50~60%) for MCFC matrixes could be attained by adding larger ${\gamma}$-LiAlO2 particles with the diameter of about 50${\mu}{\textrm}{m}$ up to 50 wt%. The optimum length and content of the alumina fiber, both in the alignment of fibers and the enhancement of the strength, were found to be below 250${\mu}{\textrm}{m}$ and 20 wt%, respectively. On the other hand, the strength(156 gf/$\textrm{mm}^2$) of the ${\gamma}$-LiAlO2 matrix reinforced with ${\gamma}$-LiAlO2 fibers prepared in this study was improved by 20~40% in comparison with the alumina-fiber-reinforced matrix. It was also found that the alu-mina-fiber-reinforced matrix was completely corroded in molten carbonates but the ${\gamma}$-LiAlO2 was not.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.1059-1062
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• 2005

본 논문에서 이론적으로 분석하고자 하는 기술포트폴리오 매트릭스는 기술매력성(계속적 개발잠재성, 응용범위, 호환가능성)과 자원강도(지배범위, 잠재성, 반응속도)에 기초한 기술투자 분석 또는 전략적 기술관리를 위한 유용한 의사결정 수단이다. 즉, 기술포트폴리오는 국내기업뿐만 아니라 현지투자기업의 연구개발과 관련된 의사결정을 위하여 활용될 수 있다. 특히, 본 연구에서는 글로벌 기업에 있어서의 본사 및/또는 현지자회사간의 기술포트폴리오 매트릭스를 분석함으로써 글로벌 기업의 기술포트폴리오 관리를 위한 방법을 제시하고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.2
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• pp.35-39
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• 1985

The closed form of the stiffness matrix is derived in terms of closed forms of intergrals for analyses of plane frame members containing linerly tapered members with the cross section of thin-walled tube. The series expansion forms of these are also developed to study the errors in the closed form of the stiffness matrix. The useful limits of the closed form of integrals are defined in terms of the relative taper.

• Korean Journal of Materials Research
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• v.7 no.12
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• pp.1097-1104
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• 1997

인산형 연료전지(PAFC)용 전해질 매트릭스의 표면 거칠기를 감소시켜 분극저항을 줄이고 작업성을 향상시키기 위해 SiC whisker를 사용하여 일반적인 테이프 캐스팅법으로 제조된 매트릭스의 거친 표면을 평탄화 처리하였다. 구형 입자의 분무공정을 이용하여 표면 평탄화 처리(process l)하는 경우와 롤링을 이용하여 표면 평탄화 처리(process 2)하는 두가지 공정을시도하였으며, 두가지 공정 모두 기공율과 인산 함침도를 유지시키면서, 매트릭스의 표면 거칠기를 감소시키고 기공압, 가소성 및 인장강도를 향상시킬 수 있었다. 위와 같이 제조한 매트릭스로 연료전지를 구성하여 교류 임피던스 분석을 한 결과, 표면 평탄화 처리는 매트릭스 표면의 거칠기를 감소시킴으로써 전극과의 접촉시 계면에서의 분극 저항을 감소시켜 전지성능을 향상시키는 것으로 나타났다. process 2는 표면의 거칠기 감소뿐 아니라 표면에서의 인산함침도가 커서 가장 우수한 전지특성을 나타내었으며, process 1은 매트릭스 표면에 불규칙하게 존재하는 거대 기공을 완전히 제거하고 기공압을 크게 향상시킬 수 있기 때문에 대형의 매트릭스 제조를 가능하게 하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.76-85
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• 2017

In this study, to evaluate the mechanical properties of fiber-reinforced cement composites by strain rate, hydraulic rapid loading test system was developed. And compressive and tensile strength of the hooked steel fiber and polyamide fiber reinforced cement composite were evaluated. As a result, the compressive strength, strain capacity and elastic modulus were increased with increasing strain rate. The effect of compressive strength by type and volume fraction of fibers was not significant. The dynamic increase factor(DIF) of the compressive strength was higher than that of the CEB-FIP model code 2010 and showed a trend similar to that of ACI-349. The tensile strength and strain capacity were increased with increasing strain rate. The hooked steel fibers were drawn from the matrix. The tensile strength and strain capacity of hooked steel fiber reinforced cement composites were increased as the strain rate increased. The tensile strength and deformation capacity of the fiber reinforced cement composites were increased. And, hooked steel fibers were drawn from the matrix. On the other hand, because the bonding properties of polyamide fiber and matrix is large, polyamide fiber was cut-off with out pullout from matrix. The strain rate effect on the tensile properties of polyamide fiber reinforced cement composites was found to be strongly affected by the tensile strength of the fibers.