• 한국세라믹학회지
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• 제48권1호
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• pp.106-109
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• 2011

In order to fabricate 8YSZ thick film by silk screen printing, YSZ(yttria-stabilized zirconia) commercial powder was used as starting materials. Paste for screen printing was made by mixing 8YSZ powder and organic vehicles. 8YSZ thick film was formed on $Al_2O_3$ substrate. The crystal structure, and microstructure were investigated. Grain size of 8YSZ was increased with increasing calcination temperature and rapid grain growth was shown after calcination at $1300^{\circ}C$. Microstructure showed the mixture of large and small grain size after $1400^{\circ}C$ sintering. Shrinkage rate of 8YSZ thick film sintered at $1400^{\circ}C$ was more than 40%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.185-189
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• 2000

ZnO varistor has many merits as compared with SiC varistor. But, because of leakage current and non-linear coefficient, it has unstable function properties. For the purpose of improvement of ZnO varistor properties, ZnO varistor is studied according to sintering condition and mixing condition. ZnO varistor, $ZnO-Bi_2O_2-Y_2O_3-MnO-Cr_2O_3-Sb_2O_3$ series, is fabricated with $Sb_2O_3$ mol ratio(0.5-4[mol%]) and sintered at $1250[^{\circ}C]$ In accordance with $Sb_2O_3$ mol ratio and sintering temperature, grain size and non-linear coefficient are measured. The specimen, $Sb_2O_3$ mol ratio is 1[mol%], has small grain size. It has best properties because of its liquid phase shape. When $Sb_2O_3$ mol ratio is 1[mol%], grain size is decreased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.273-278
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• 2000

In order to study effects of interface layers between PZT films and electrodes for MFM(Metal-Ferroelectric-Metal) structure capacitors, we have fabricated the capacitors with the Pt/PZT/interface-layer/Pt/$TiO_2/SiO_2/Si$ structure. $PT(PbTiO_3)$ interface layers were formed by sol-gel deposition and PbO, $ZrO_2$ and $TiO_2$ thin layers were deposited by reactive sputtering. $TiO_2$ interface layers result in the finest grains of PZT films compared to $PbO_2$ and $ZrO_2$ layers. On the other hand, PT interface layers result in improved morphology of PZT films and do not significantly change ferroelectric properties. It is also observed that seed layers at the middle and top of PZT films do not give significant effects on grain size but the PT seed layer at the interface between the bottom electrode and the PZT films results in the small grain size.

• Transactions on Electrical and Electronic Materials
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• 제11권6호
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• pp.275-278
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• 2010

We have examined the Ferroelectric properties of $PbZr_{0.4}Ti_{0.6}O_3$ (PZT) grains by monitoring the surface potential through the utilization of Kelvin force microscopy. Hysteretic and time dependent behaviors of small and large grains were compared with each other. The smaller grain yields had smaller values of surface potential. However, the normalized voltage versus surface potential behavior indicates that the smaller grains became saturated earlier with respect to the writing voltages than did the larger grains. On the other hand, the surface potential hysteresis loop obtained from the smaller grains showed a similar shape to what might be obtained from a Zr rich PZT film. In contrast the hysteresis loop of the larger grain looks like that obtained from a Ti-rich film. In addition, the time dependent behaviors of the smaller grains also revealed a better response than the response of larger grains. The overall ferroelectric properties of the smaller grains seem better than corresponding properties for larger grains. The Ti/Zr ratio of the PZT film which was examined in this study was 60/40.

• Journal of Advanced Marine Engineering and Technology
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• 제30권6호
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• pp.709-715
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• 2006

The effects of thermal cycle condition and applied stress on the intergranular corrosion in austenitic 316 type stainless steels were investigated. Specimens were solution-treated at 1100$^{\circ}C$ for one hour and then sensitized in the temperature range of $500{\sim}800^{\circ}C$ by holding $2{\sim}300s$ with a various applied stresses of $0{\sim}8kg/mm^2$. Degree of sensitization. DOS %, was measured through polarization curve by electrochemical DL-EPR test. Microstructural observations were also conducted DOS % increased with an increase of sensitization temperature and/or holding time. Increase of applied stress resulted in increase of DOS % and more corroded surface because of acceleration of intergranular corrosion and fine grain size due to the stress. Cr depleted zone near grain boundary was observed. The amount of depletion was profounded with an increase of sensitization temperature, holding time and applied stress. $M_{23}C_6$ carbides were precipitated discontinuously at grain boundary. However, its amount was relatively small in the thermal cycle condition of 800$^{\circ}C$, 300sec and 4kg/mm$^2$.

• 한국세라믹학회지
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• 제45권12호
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• pp.760-765
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• 2008

In this study, the effects of small amounts (${\leq}3\;mol%$) of Li doping on the sintering characteristics and electrochemical performance of $(ZrO_2)_{0.89}(ScO_{1.5})_{0.1}(CeO_2)_{0.01}$ (ScSZ) were investigated. By adding 3 mol% lithium, the densification temperature of ScSZ was reduced from the conventional temperature of $1400^{\circ}C$ to $1200^{\circ}C$. It was found that Li doping also led to changes in the Zr:Sc ratio at the grain boundaries. Correspondingly, the dispersion of lithium zirconia at the grain boundaries accelerated the growth of ScSZ grains and increased the grain boundary resistance at temperatures below $450^{\circ}C$. At elevated temperatures of $450{\sim}750^{\circ}C$, the electrical conductivity of the ScSZ after doping remained almost unchanged under air and reducing atmospheres. These results suggest that the addition of lithium is promising for use in low temperature co-firing of ScSZ-based components for intermediate temperature solid oxide fuel cells.

• 열처리공학회지
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• 제10권2호
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• pp.81-92
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• 1997

The effect of alloying elements, precipitate size, its distribution, and dislocation substructure resulted from warm rolling or cold rolling in the superplastic Al-Mg alloy system was investigated. One of the major requirements for fine structure superplasticity is that the grain size should be very small. Fine grain structure is controlled by the dislocation substructure and the dynamic recrystallization during hot or warm working. The recovery of Al-Mg base alloys was constrained resulting in relatively high dislocation density when the alloys were warm rolled. In particular, Al-Mg-Zr alloy exhibited the smallest sub-grain size among Al-Mg alloys containing Mn, Cu, Zr as a third element. The Al-Mg-Mn alloy cold rolled 80% after hot rolling showed the maximun strain rate sensitivity exponent, m, of 0.75 under strain rate of $7.1{\times}10^{-4}/s$ at $500^{\circ}C$. The elongation of the alloys was limited in spite of high m values due to large dispersoids containing appreciable amount of Fe impurities.

• 한국임상수의학회지
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• 제34권1호
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• pp.39-42
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• 2017

An 8-month-old, intact male Maltese dog was referred to us because of anorexia, diarrhea, and jaundice. Hematologic examination revealed immune-mediated hemolytic anemia, and abdominal ultrasonography revealed heterogeneous changes in mesenteric fat and coarse echotexture in the splenic parenchyma. Septic peritonitis was diagnosed on the basis of a bacterial culture test of the peritoneal fluid. Exploratory laparotomy and subsequent omental biopsy and splenectomy were performed. On histopathological examination, the omental mass and splenic lesions were diagnosed as grain foreign body granulomas. This report describes a rare case in which a grain foreign body was embedded in the spleen of a dog.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.261-264
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• 2008

고체 연료로 파라핀을 사용하고 산소를 산화제로 사용하는 하이브리드 로켓의 연소 특성에 대해 실험 연구를 진행하였다. 특히 연소실 내부의 압력과 연료 그레인의 형태에 따른 영향을 살펴보았다. 연소 시 산화제의 유입량을 변화시키며 연소실 내부의 압력을 측정하였다. 관찰된 압력변화 범위 내에서 연소실 내부의 압력이 증가할 때 후퇴율도 증가함을 보여주었다. 또한 연료 그레인 형태의 변화에 따라 후퇴율이나 추력 등은 어느 정도 경향성을 보인다. 산화제 유입 부분에 공간을 마련하면 추력이 증가하나 노즐 가까운 곳에 형성한 공간은 추력 상승에 큰 도움이 되지 않는다.

• 대한화학회지
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• 제23권4호
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• pp.217-236
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• 1979

소성변형에 대한 著者들의 이론을 초소성합금(Zn-Al eutectoid, A1-Cu, Pb-Sn, Sn-Bi, Mg-Al eutectics)에 적용하였다. 그 결과 초소성합금의 소성변형은 두 개의 grain boundary流動單位의 平行連結로 나타낼 수 있었다. 이 두 개의 流動單位는 流動式에 나타나는 parameter $X_{gj}/{\alpha}_{gj}$와 ${\beta}_{gj}$(j=1 혹온 2)로 表現할 수 있으며 이들을 實驗的으로 求할 수 있었다. 著者들의 流動式은 實驗과 잘 一致하였다. Strain rate sensitivity 對 -In(strain rate) 곡선을 이론으로 구한 결과 유동단위수만큼의 peak가 ${\beta}_{gj}$(j=1 or 2) 값에 따라 분리되어 나타났고 초소성의 조건도 ${beta}_{gj}$값에 의하여 결정됨을 알았다. ${\beta}_{gj}값의 粒子크기 依存性을 구하였고 온도변화에 따른 ${\beta}_{gj}$값 변화로부터 각 流動單位의 활성화엔탈피, ${\Delta}H_{gj}^{\neq}$도 구하였다. 그 결과 ${\Delta}H_{gj}^{\neq}$는 재료성분원소들의 grain boundary 자체확산에 의한 활성화엔탈피와 같이 나타났고 또 이들은 粒子 크기 증가에 마라 증가함을 보였다