• 한국결정성장학회지
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• 제8권4호
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• pp.634-639
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• 1998

$Y_2O_3$와 $Nb_2O_5$가 첨가된 지르코니아에 입자 크기가 다른 두종류의 Al2O3를 부피비로 10~30% 첨가한 복합체를 155$0^{\circ}C$ 온도에서 5시간 소결하여 $250^{\circ}C$ 온도의 공기 분위기하에서 1000시간 혹은 $180^{\circ}C$ 온도의 0.3MPa H2O vapor pressure 분위기하에서 5시간 열처리를 하여 X-ray 회절분석 방법을 이용하여 저온 상안정성을 조사하였다. 복합체 전부 열처리 후에 정방정 상에서 단사정 상으로 상전이가 발생하지 않는 우수한 저온 상안정성이 관찰되었다. 복합체의 상아정성에 Nb 첨가가 $Al_2O_3$의 첨가보다 더 효과적이었다. 2.8$\mu$m 입자크기를 가진 Al2O3를 부피비로 20% 첨가한 복합체에서 최적의 조건이 관찰되었으며 강도와 인성값은 각각 670MPa와 7.1MPam1/2이었다. Al2O3 입자 크기가 2.8$\mu$m에서 0.2$\mu$m로 감소함에 따라 강도는 다소 증가하였으나 파괴인성값은 감소하였다.

• 열처리공학회지
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• 제34권2호
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• pp.53-59
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• 2021

Due to high specific strength and low density, AZ series magnesium alloys have been receiving high interest as a lightweight material. However, their industrial application is limited due to the phenomenon that the strength decreases at elevated temperature by the occurrence of softening effect because of the Mg17Al12 phase decomposition. To solve this problem, many research were conducted to increase the high-temperature strength by forming a thermal stable second-phase component by adding new elements to the AZ magnesium. Especially, adding Ca to AZ magnesium has been reported that Ca forms the new second-phase. However, studies about the analysis of decomposition or precipitation temperature, formation composition, and components to understand the formation behavior of these precipitated phases are still insufficient. Therefore, the effect of Ca addition to AZ61 on the phase change and microstructure of the alloy during annealing was investigated. As a result of analysis of the initial and heat-treated specimen, AZ61 formed α-Mg matrix and precipitated phase of Mg17Al12, and AZX611 formed one more type of precipitated phase, Al2Ca. Also, Al2Ca was thermal stable at high temperatures. And after annealing, the laves phase was decomposed to under 10 ㎛ size and distributed in matrix.

• 한국세라믹학회지
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• 제36권10호
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• pp.1056-1061
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• 1999

Phase formation and oxygen ion conduction of La(Ba)Ga(Mg)O3-$\delta$ system was studied, BaLaGa3O7 and BaLaGaO4 formed as a secondary phase above the solubility limit of Ba2+ in La3+ sites. The oxygen ionic conductivity of La(Ba)Ga(Mg)O3-$\delta$ was 0.1 S/cm 80$0^{\circ}C$ The activation energy of the oxygen ion conduction was dependent on temperature. This value was higher at low temperature than at high temperature.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.300-303
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• 2001

BSCCO thin films are fabricated via a co-deposition process by an ion beam sputtering with an ultra-low growth rate, and sticking coefficients of the respective elements are evaluated. The sticking coefficient of Bi element exhibits a characteristic temperature dependence : almost a constant value of 0.49 below $730^{\circ}C$ and decreases linearly with temperature over $730^{\circ}C$. This temperature dependence can be elucidated from the evaporation and sublimation rates of bismuth oxide, $Bi_{2}O_{3}$, from the film surface. It is considered that the liquid phase of the bismuth oxide plays an important role in the Bi 2212 phase formation in the co-deposition process.

• 한국전기전자재료학회논문지
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• 제13권1호
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• pp.80-84
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• 2000

BSCCO thin films are fabricated via a co-deposition process by an ion beam sputtering with an ultra-low growth rate, and sticking coefficients of the respective elements are evaluated. The sticking coeffi-cient of Bi element exhibits a characteristic temperature dependence : almost a constant value of 0.49 below 73$0^{\circ}C$ and decreases linearly with temperature over 73$0^{\circ}C$. This temperature dependence can be elucidated from the evaporation and sublimation rates of bismuth oxide, Bi\ulcornerO\ulcorner, from the film surface. It is considered that the liquid phase of the bismuth oxide plays an important role in the Bi(2212) phase formation in the co-deposition process.

• 설비공학논문집
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• 제13권11호
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• pp.1097-1105
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• 2001

The purpose of this study is to investigate the propriety of TMA clathrate as a cold storage medium. Particularly, this is to examine the extent of subcooling improvement when the additives are added to the TMA clathrate, because water used cold storage material has low phase change temperature and subcooling. This study has been analysed and compared with TMA 30 wt% clathrate how phase change temperature, subcooling and specific heat in the various concentrations are changed. This results view to be improved phase change temperature and subcooling of TMA 30 wt% as a cold storage medium, when it had some additive. Additional1y, it is found that the additive must be controlled under available solution limit and study for new additive must be lasted to know its effect.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.300-303
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• 2001

BSCCO thin films are fabricated via a co-deposition process by an ion beam sputtering with an ultra-low growth rate, and sticking coefficients of the respective elements are evaluated. The sticking coefficient of Bi element exhibits a characteristic temperature dependence : almost a constant value of 0.49 below 730$^{\circ}C$ and decreases linearly with temperature over 730$^{\circ}C$. This temperature dependence can be elucidated from the evaporation and sublimation rates of bismuth oxide, Bi$_2$O$_3$, from the film surface. It is considered that the liquid phase of the bismuth oxide plays an important role in the Bi 2212 phase formation in the co-deposition process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.213-216
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• 1999

BSCCO thin films are fabricated via a co-deposition process by an ion beam sputtering with an ultra-low growth rate, and sticking coefficients of the respective elements are evaluated. The sticking coefficient of Bi element exhibits a characteristics temperature dependence : almost a constant value of 0.49 below 730$^{\circ}C$ and decreases linearly with temperature over 730$^{\circ}C$. This temperature dependence can be elucidated from the evaporation and sublimation rates of bismuth oxide, Bi$_2$O$_3$ from the film surface. It is considered that the liquid phase of the bismuth oxide plays an important role in the Bi(2212) phase formation in the co-deposition process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.193-197
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• 2000

BSCCO thin films are fabricated via a co-deposition process by an ion beam sputtering with an ultra-low growth rate, and sticking coefficients of the respective elements are evaluated. The sticking coefficient of Bi element exhibits a characteristic temperature dependence : almost a constant value of 0.49 below 73$0^{\circ}C$ and decreases linearly with temperature over 73$0^{\circ}C$. This temperature dependence can be elucidated from the evaporation and sublimation rates of bismuth oxide, Bi$_2$O$_3$, from the film surface. It is considered that the liquid phase of the bismuth oxide plays an important role in the Bi(2212) phase formation in the co-deposition process.

• 한국주조공학회지
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• 제40권2호
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• pp.16-24
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• 2020

The effect of a heat treatment on the microstructure and mechanical properties of Inconel 713C alloy vacuum investment castings were investigated. The microstructure of the as-cast state was observed, showing well-developed dendrite structures and distributed carbide particles and solidified massive precipitates in the grain or grain boundary during solidification, in this case the γ′ phase and MC particles. During a heat treatment, the γ phase matrix was reinforced by solid solution elements, carbide particles from the film morphology precipitated along the grain boundary, and many micro-precipitates of second γ′ phases 0.2 ㎛~2 ㎛ in size were newly formed in the γ phase matrix according to SEM-EDS analysis results. The tensile strength at a high temperature (850℃) decreased slightly becoming comparable with the room-temperature result, while the hardness value of the specimen after the vacuum heat treatment increased by approximately 19%, becoming similar to that of the as-cast condition. However, the impact values at room temperature and low temperature (-196℃) were approximated; this alloy was mostly not affected by an impact at a low temperature. In the observations of the fracture surface morphologies of the specimens after the tensile tests, the fractures at room temperature were a mix of brittle and ductile fractures, and an intergranular fracture in the inter-dendrite structure and some dimples in the matrix were observed, whereas the fractures at high temperatures were ductile fractures, with many dimples arising due to precipitation. It was found that a reinforced matrix and precipitates of carbide and the γ′ phase due to the heat treatment had significant effects, contributing greatly to the excellent mechanical properties.