• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.182-182
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• 2009

The effect of Re-oxidation on the PTCR properties of Sm-doped barium titanate ceramics was investigated by means of impedance spectroscopy. Electrical properties such as resistance vs. temperature, I-V curve were measured and microstructure was observed with SEM photography. Sample was fabricated with thick film process such as tape casting of green sheet, screen printing of electrode pattern, stacking, firing in reduced atmosphere and re-oxidation, etc. As the temperature of re-oxidation increases, resistance jump as a function of temperature enhances but resistance at room temperature increases. These behavior of resistance as a function of temperature, dependent on the re-oxidation condition, is analyzed with Cole-Cole impedance plot and is shown to be related with the degree of oxidation of grain boundary regardless of grain core during re-oxidation process of sample.

• Transactions of Materials Processing
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• v.16 no.5 s.95
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• pp.396-400
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• 2007

LTCC(Low Temperature Co-fired Ceramic) which offers a good performance to produce multilayer structures with electronic circuits and components has emerged as an attractive technology in the electronic packaging industry. In LTCC module fabrication process, the lamination and the sintering are very important processes and affect the electrical characteristics of the final products because the processes change the permittivity of ceramics and the dimension of the circuit patterns which have influences on electronic properties. This paper discusses the influence of lamination pressure and sintering temperature on the permittivity and the dimensional change of LTCC products. In the present investigation, it is shown that the permittivity increases along with increasing of the lamination pressure and the sintering temperature.

• 한국전기화학회:학술대회논문집
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• 2001.06a
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• pp.231-236
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• 2001

용융탄산염 연료전지용 anode의 creep 현상을 개선하기 위해 $Ni-5wt.\%Al$ green sheet를 사용하여 다양한 소결조건을 적용, $Al_2O_3$를 형성시킨 전극을 제조하고 그 $Al_2O_3$의 형태에 따른 creep 특성에 대해 연구하였다. 소결은 각각 환원분위기, 완전산화-환원분위기, 부분 산화-환원분위기의 서로 다른 분위기에서 진행하였는데, 부분산화-환원분위기로 소결한 경우 Ni-Al 고용체 네트워크를 깨드리지 않고 $A1_2O_3$를 미세한 입자형태로 분산시킬 수 있었다. 그리고, 상기의 방법으로 제조된 anode를 $650^{\circ}C$에서 100psi로 가압하면서 creep test를 실시한 결과 약 $2.3\%$의 변형율을 나타내었다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.5
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• pp.371-380
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• 2008

This study elucidated the floral composition of marine algae and community structure at Hallyeo-haesang National Park, on the southern coast of Korea. In all, 89 species, comprising 10 green, 30 brown and 49 red algae, were identified. The dominant species in terms of importance value were Ulva pertusa, Colpomenia sinuosa, Undaria pinnatifida, Padina arborescens, Hizikia fusiformis, Sargassum sagamianum and Amphiroa dilatata. The vertical distribution of marine vegetation was characterized by Enteromorpha linza - Ulva pertusa - Gelidium divaricatum in the upper intertidal zone, Hizikia fusiformis - Sargassum thunbergii in the middle intertidal zone, and Amphiroa spp. - Hildenbrandtia rubra - Corallina pilulifera in the lower intertidal zone. Functional form group analysis showed that coarsely branched forms comprised 50.3% of the algal community, whereas thick leathery forms, sheet forms and filamentous forms comprised 11.9-13.1%. R/P, C/P and (R+C)/P values were 1.91, 0.74 and 2.64, respectively. A cluster analysis of species occurrence suggested that the number of marine algal species differed greatly among the sampling sites.

• Journal of the Korean institute of surface engineering
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• v.28 no.4
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• pp.243-254
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• 1995

The fabrication process of Cu-base anode for replacing Ni-base anode of molten carbonate fuel cell was investigated. Electrochemical performance and thermal stability of Cu-base anode were also investigated. Green sheet was prepared by mixing Cu and Ni powder with 1.5wt% methylcellulose and 100wt% water. The pore-size distribution of the Cu-base anode sintered at $800^{\circ}C$ for 30min showed almost uniform pore-size ranging from 4 to 20$\mu\textrm{m}$ and it was considered suitable for MCFC anode. Cu-Ni anode containing between 35 to 50wt% Ni exhibited current density of 111mA/$\textrm{cm}^2$ at 100mV overpotential and it was almost the some value for pure Ni anode. The sintering resistance of Cu-Ni increased with an increase of Ni addition. It was considered that the increase of sintering resistance was due to the decrease of diffusion rate of Cu and Ni with increasing the addition of Ni in Cu-Ni alloy.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.601-610
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• 1997

In cofiring of multilayered alumina with tungsten, the change of camber with lamination condition was experimented and the effect of sintering shrinkage of alumina and tungsten was investigated. From the exact measurement of sintering shrinkage of tungsten thick film, as lamination pressure increased, the sintering shrinkage of alumina decreased but that of tungsten thick film was not changed. So it was though that the main factor which induced the sintering shrinkage difference between ceramics and metal with lamination condition was the change of sintering shrinkage of ceramics. In case of high lamination pressure, high green sheet density, the cofired specimen showed low camber due to low shrinkage difference between alumina and tungsten and there was a linear relation between camber and shrinkage difference. It was found that this shrinkage difference could change the thickness of tungsten film and the microstructure within via hole during cofiring.

• Journal of the Korean Ceramic Society
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• v.36 no.5
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• pp.490-496
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• 1999

The sintering behavior of LTCC (low temperature cofired ceramics) chip couplers was investigated in relation with Ag diffusion at the interface of glass ceramic substrate-Ag electrode. Sintering temperature was in the range of 825$^{\circ}C$-975$^{\circ}C$. The commercial green sheet and silver electrode were used. Below 875$^{\circ}C$ the diffusion of the Ag ion into the substrate and the penetration of glassy phases into the electrode occurred due to an increase of fluidity. Thus the lectrode line was severely deformed and damaged. At 975$^{\circ}C$ the transformation of crystalline phases into glassy phases and the melting of the Ag electrode resulted in the diffusion of the considerable amount of Ag ions.

• Ceramist
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• v.21 no.1
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• pp.55-63
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• 2018

Recently, display technology has been focused in regard with with color reproduction, contrast ratio, image resolution and color bit. Among these technologies, the color reproducibliity of White, Red, Green, and Blue is associated with the TV plaform and is expressed as a major technology. Major TV platforms are divided into three categories since 2015, including LCD-based phosphor coverted LED BLU technology, QD sheet technology using nano-sized quantum dots, and OLED technology. In this paper, we describe the color reproducibility definition and background, luminescent materials with wide color gamut, color reproducibility of TV display performance, and discuss about next luminescent materials.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.6
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• pp.271-275
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• 2001

We investigated preparation of 1-3 PZT composites for medical ultrasonic transducer array (briefly UTA) using micro pressing method. The proposed process was using pressing PZT green sheet by PMMA micro mold obtained from X-ray lithography. Microstructures, electriacl and electro-mechanical properties of fabricated composites were analyzed. Dielectric constant at 1kHz and thickness mode electro-mechanical coupling coefficient of $6.2mm{\times}6.2mm{\times}422{\mu}m$ UTA sample were 1754 and 51%, respectively. Microstructures of sintered PZT showed dense and uniform. And PZT phases were well crystallized. Micro pressing method is a mass productive process in case of using injection molded PMMA by batch type LIGA process.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1424-1426
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• 2003

PMN-PZT 적충형 세라믹 액츄에이터 소자를 제작한후 그 열화 특성을 조사하였다. 액츄에이터는 tape casting 방법으로 green sheet를 제작한후, screen printing방법을 이용하여 전극형상을 만들고, lamination과 cutting공정을 통하여 소자를 제작하였다. 작된 소자의 구조적인 특성을 분석하기 위하여 X-ray diffractometer를 사용하였으며, Doppler effect를 사용하는 laser vibrometer를 이용하여 전압에 따른 변위량을 측정하였다. 제작된 소자의 열화 특성을 알아보기 위하여 60 Hz의 triangular 교류 파형을 적충형 세라믹 액츄에이터에 인가하여 열화전과 후의 P-E hysteresis loop의 변화를 살펴보았으며, unipolar AC 전압을 지속적으로 인가하여 소자를 depling 시킴으로써 열화현상을 관찰하였다. 파단면에 대한 SEM 분석을 통하여 소자의 파괴 메카니즘을 알아 보도록 하였다. 이로부터 전기적, 기계적 열화가 소자의 동작에 미치는 영향에 대해서 알아 보았다.