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YSZ (yttria - stabilized zirconia) 박막을 이용한 센서 셀의 산소 감응
박준용(J. Y. Park),배정운(J. W. Bae),황순원(S. W. Hwang),김기동(K. D. Kim),조영아(Y. A. Cho),전진석(J. S. Jeon),최동수(D. Choi),염근영(G. Y. Yeom) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.4(2)
본 실험에서는 산소 이온 전도체로서 Smol%-YSZ 고체전해질을 RF-magnetron bias sputtering 법을 이용하여 증착하였으며 YSZ 박막을 이용한 산소감응 센서 셀 구조는 SiO₂기판상/Ni-NiO/Pt/YSZ/Pt 다층 박막 구조로 제조하였다. 센서 셀의 정상상태에서의 기전력(electromotive force; EMF)은 산소분압(Po₂ : 1.013×10³ Pa ~ 1.013×10^5 Pa)과 측정온도(300~700℃)를 변화시켜가며 측정하였다. 제작된 셀의 산소 감응 실험결과 500℃에서 가장 우수한 감응특성을 나타내었으나 300℃ 이하에서는 산소 이온 이동의 어려움으로, 700℃ 이상에서는 박막중간의 상호 확산으로 감응특성이 저조하였다. 특히 본 실험에서 제조된 YSZ 산소센서는 500℃ 및 산소분압 1.565×10⁴ Pa 이상의 비교적 높은 산소 분압에서 Nemst equation에 근접한 산소 감응 특성을 나타내었다. 8 mol%-yttria-stabilized zirconia (YSZ) thin films as oxygen ion conductor were deposited by rf-magnetron sputtering, and the oxygen gas sensors with the structure of SiO₂ substrate/Ni-NiO mixed reference layer/Pt/YSZ/Pt were fabricated and their oxygen sensing properties were investigated. The steady-state electromotive force (EMF) values were measured as a function of oxygen partial pressure (PO₂; from 1.013×10³ Pa to 1.013×10^5 Pa) and operating temperature (300℃ to 700℃). The fabricated YSZ oxygen sensor showed the best oxygen sensing properties at 500℃. However, oxygen sensing properties were very low at the temperature lower than 300℃ due to the lack of oxygen ion mobility and at the temperature higher than 700℃ due to intermixing of materials between the layers. Especially, the YSZ sensor operating at 500℃ and oxygen partial pressure above 1.565×10⁴ Pa showed the oxygen sensing properties close to the values predicted by ideal Nemst equation.
배정운(J. W. Bae),강충길(C. G. Kang) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월
In this study, the morphology of the change of primary Al phase in A356 alloy by two kinds of electromagnetic stirrers(vertical and horizontal) were investigated to obtain the globular structure. The effects of the stirring current, the stirring time and the pouring temperature were determined. The greater stirring current and longer stirring time were to get the finer the Al phase. However, over a certain stirring current and stirring time, the primary Al was merged together and was increased. The reason is the degree of breakdown of initial dendrites has been decreased by the collision and coalescence of particles with increasing stirring current and stirring time. The optimum conditions and difference of the two kinds of electromagnetic stirrers have been investigated for rheology forming with controlled solid fraction.
열 유동 현상을 고려한 마그네슘 용탕 직접 압연공정 해석
배정운(J. W. Bae),강충길(C. G. Kang),강석봉(S. B. Kang) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월
The proper parameters in a twin roll strip casting are important to obtain the stabilization of the Mg sheet. What is examined in this paper is the quantitative relationships of the important control parameters such as the roll speed, height of pool region, outlet size of nozzle, solidification profile and the final point of solidification in a twin roll strip casting. Unsteady conservation equations were used for transport phenomena in the pool region of a twin roll strip casting in order to predict a velocity, temperature distributions of fields and a solidification process of molten magnesium. The energy equation of cooling roll is solved simultaneously with the conservation equations of molten magnesium in order to consider the heat transfer through the cooling roll. The finite difference method (2-D) and the finite element method (2-D) are used in the analysis of pool region and cooling roll to reduce computing time and to improve the accuracy of calculation respectively.