• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.84.2-84.2
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• 2011

In this research, two thin film deposition techniques, Atomic Layer Deposition and Sputtering are carried out for the fabrication of Yittria Stabilized Zirconia electrolyte for thin film Solid Oxide Fuel Cell. Zirconium to Yittrium ratio for both cases is about 1/8. Scanning Electron Microscope(SEM) image shows that the growth rate per hour for Atomic Layer Deposition is faster than for sputtering. X-ray Photo-electron Spectroscopy(XPS) shows that the peaks of both Zirconia and Yittria shift towards higher bending energy for the case of Atomic Layer deposition and thus are more strongly attached to the substrate. Later, Nyquist plot was used to compare the conductivity of Yittria Stabilized Electrolyte for both cases. The conductivity at $300^{\circ}C$ for Atomic Layer Deposited Yittria Stabilized Zirconia is found to be $5{\times}10^{-4}S/cm$ while that for sputtered Yittria Stabilized Zirconia is $2{\times}10^{-5}S/cm$ at the same temperature. The reason for better performance for Atomic Layered YSZ is believed to be the Nano-structured layer fabrication that aids in along the plane conduction as compared to the columnarly structured Sputtered YSZ.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.84.1-84.1
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• 2011

Typical solid oxide fuel cells (SOFCs) have limited applications because they operate at high temperature due to low ionic conductivity of electrolyte. Thin film solid oxide fuel cell with yttria stabilized zirconia (YSZ) electrolyte is developed to decrease operating temperature. Pt/YSZ/Pt thin film SOFC was fabricated on anodic aluminum oxide (AAO). The crystalline structure of YSZ electrolyte by sputter is heavily depends on the roughness of porous Pt layer, which results in pinholes. To deposit YSZ electrolyte without pinholes and electrical shortage, it is necessary to deposit smoother and denser layer between Pt anode layer and YSZ layer by sputter. Atomic Layer Deposition (ALD) technique is used to deposit pre-YSZ layer, and it improved electrolyte quality. 300nm thick Bi-layered YSZ electrolyte was successfully deposited without electrical shortage.

• 한국세라믹학회지
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• 제43권2호
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• pp.85-91
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• 2006

Electron Beam Physical Vapor Deposition (EB-PVD) was applied to fabricate a thin film YSZ electrolyte with large area on the porous NiO-YSZ anode substrate. Microstructural and thermal stability of the as-deposited electrolyte film was investigated via SEM and XRD analysis. In order to obtain an optimized YSZ film with high stability, both temperature and surface roughness of substrate were varied. A structurally homogeneous YSZ film with large area of $12\times12\;cm^2$ and high thermal stability up to $900^{\circ}C$ was fabricated at the substrate temperature of $T_s/T_m$ higher than 0.4. The smoother surface was proved to give the better film quality. Precise control of heating and cooling rate of the anode substrate was necessary to obtain a very dense YSZ electrolyte with high thermal stability, which affords to survive after post heat treatment for fabrication a cathode layer on it as well as after long time operation of solid oxide fuel cell at high temperature.

• 한국자동차공학회논문집
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• 제22권3호
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• pp.210-219
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• 2014

The MPI dual injection engine can enhance the fuel efficiency and engine power. By using one injector per one intake port, MPI dual injection engine has an excellent fuel atomization and targeting injection. As the basic research for the MPI Dual injection engine design, this research was investigated in order to understand the characteristic of the in-cylinder flow and fuel behavior according to engine temperature condition and the fuel type in the MPI dual injection engines. The 3D unsteady CFD simulation for the MPI Dual injection engine was performed using STAR-CD. The engine operating condition was 2,000 rpm/WOT. The parameters for this study were fuel types, fuel temperatures and wall temperatures. As a result, the intake air amount, evaporated fuel in the cylinder and the fuel film on the wall were presented according to parameters that depend on the fuel properties and engine wall temperature. Also, the results were influenced by in-cylinder flow such as the intake flow, back flow and so on.

• 한국자동차공학회논문집
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• 제23권2호
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• pp.221-229
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• 2015

The PFI dual injection engine using one injector per an intake port was developed for solving the DISI engine cost problem. Excellent fuel atomization and targeting of the PFI dual injection engine made enhancement on the fuel efficiency and engine power. In order to develop a PFI dual injection engine, characteristics of the in-cylinder flow and fuel behavior with respect to fuel injection angle and cone angle of the PFI dual injection engine was investigated. Numerical calculation was conducted to analyze 3D unsteady in-cylinder flow and fuel behavior using STAR-CD. The engine operating condition was 2,000rpm at WOT. As a result, the amount of intake air, evaporated fuel and fuel film according to injection angle and cone angle were presented. The results were influenced by interaction between injected fuel and intake port wall.

• 마이크로전자및패키징학회지
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• 제6권1호
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• pp.23-29
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• 1999

전착법(EPD)에 의한 음극지지형 SOFC 단전지용 전해질 제조를 위하여 NiO-YSZ 다공성 기판 위에 극성이 서로 다른 전착용액을 사용하여 안정화 지르코니아 균일막 형성을 위한 전착조건과 막특성을 조사하였다. 알콜계 용액과는 달리 수계 용액에서 정전류, 0.138mA/$\textrm{cm}^2$이상에서 전극반응으로 생성한 기포에 의한 막결함이 생성하였으며 막무게 증가율이 감소하였다. 균일막 형성은 알콜계 용액에서 전극반응없이 안정한 전압특성을 보이는 정전류 0.035 mA/$\textrm{cm}^2$를 10초간 인가하였을 때 얻어졌다.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2454-2465
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• 2023

Film boiling may lead to burnout of the heating element. Even though burnout does not occur, the heating element is subject to deformation because it is not sufficiently strong to withstand external loads. In particular, the ballooning and rupture of a tube under film boiling are important phenomena in the field of nuclear reactor safety. If the tube-type cladding of nuclear fuel ruptures owing to high internal pressure and thermal load, radioactive materials inside the cladding are released to the coolant. Therefore, predicting the ballooning and rupture is important. This study presents numerical simulations to predict the ballooning behavior and rupture time of a horizontal tube at high internal pressure under saturated film boiling. To do so, a multi-step coupled simulation of conjugated film boiling heat transfer and ballooning using creep model is adopted. The numerical methods and models are validated against experimental values. Two different nonuniform heat flux distributions and four different internal pressures are considered. The three-step simulation is enough to obtain a convergent result. However, the single-step simulation also successfully predicts the rupture time. This is because the film boiling heat transfer characteristics are slightly affected by the tube geometry related to creep ballooning.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2003년도 연료전지심포지움 2003논문집
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• pp.83-88
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• 2003

PtRu alloy and $PtRu-WO_3$ nanocomposite thin-film electrodes for methanol electrooxidation were fabricated by means of a sputtering method. The structural and electrochemical properties of well-defined PtRu alloy thin-film electrodes were characterized using X-ray diffraction, Rutherford backscattering spectroscopy. X-ray photoelectron spectroscopy, and electrochemical measurements. The alloy thin-film electrodes were classified as follows: Pt-based and Ru-based alloy structure. Based on structural and electrochemical understanding of the PtRu alloy thin-film electrodes, the well-controlled physical and (electro)chemical properties of $PtRu-WO_3$, showed superior specific current to that of a nanosized PtRu alloy catalyst, The homogeneous dispersion of alloy catalyst and well-formed nanophase structure would lead to an excellent catalytic electrode reaction for high-performance fuel cells. In addition, the enhanced catalytic activity in nanocomposite electrode was found to be closely related to proton transfer in tungsten oxide using in-situ electrochemical transmittance measurement.

• 한국세라믹학회지
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• 제44권10호
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• pp.589-595
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• 2007

Physical properties of sputtered YSZ thin film electrolytes on anode thin film by spray pyrolisis has been investigated to realize the porous electrode and dense electrolyte multilayer structure for micro solid oxide fuel cells. It is shown that for better crystallinity and density, YSZ need to be deposited at an elevated temperature. However, if pure NiO anode was used for high temperature deposition, massive defects such as spalling and delamination were induced due to high thermal expansion mismatch. By changing anode to NiOCGO composite, defects were significantly reduced even at high deposition temperature. Further research on realization of full cells by processing hybridization and cell performance characterization will be performed in near future.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.135-140
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• 2007

막냉각이 적용된 액체로켓엔진의 비추력 최적조건을 분석하였다. 본 연구에서 구한 엔진의 비추력 성능을 문헌에 소개된 가스발생기 사이클 엔진의 개념설계와 비교하여 적절한 정확성을 가지는 것을 확인하였다. 비추력을 극대화할 수 있는 조건으로 최적의 막냉각 유량과 재생냉각 용량의 조합이 제시되었다. 추력이 증가될 경우, 막냉각 유량이 감소하고 연료펌프 차압은 증가한다. 터빈 입구온도 증가에 따라 최적 조건의 막냉각 유량과 연료펌프 차압이 증가한다. 코킹 온도 증가 역시 터빈 입구온도와 정성적으로 동일한 영향을 가진다.