• 한국초전도ㆍ저온공학회논문지
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• 제13권4호
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• pp.18-21
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• 2011

In this work, the yttrium oxide($Y_2O_3$) thin films as the buffer layer were prepared by the simple solution coating and reel-to-reel process on an unpolished metal tape substrate. The $Y_2O_3$ thin films were successfully synthesized by the hydrolysis of yttrium acetate. We have studied the improvement of surface roughness with the concentration of solution(0.1 M, 0.4 M, M) and the number of coatings. The planarization by solution coating process is simple in comparison with the existing polishing process, and it is eco-friendly, and has the benefits of low cost process. The thickness of $Y_2O_3$ films was increased with the $Y_2O_3$ concentration in the solution, and the surface became smoother with the number of coating cycles. Using this process, we have achieved 1.2 nm RMS roughness from a starting roughness of over 31 nm on 25 ${\mu}m^2$ area.

• 한국초전도ㆍ저온공학회논문지
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• 제8권4호
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• pp.12-14
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• 2006

YBCO coated conductors have been fabricated by the reel-to-reel processing using TFA-MOD method. In this work, the fluorine-free Y & Cu precursor solution was synthesized to shorten the calcining time by reducing the evolution of HF gas, thus the meter-long YBCO precursor films can be made within few hours by the continuous slot-die coating & calcination step using the F-free Y & Cu precursor solution. The annealing step was followed to make the YBCO films by the reel-to-reel method with the vertical gas flow system onto the moving tape. To increase the growth rate of the YBCO films by enhancing the removal of HF gas, the low total pressure was adopted in the annealing processing. And the water partial pressure and the oxygen partial pressure were varied to optimize the growth conditions of the MOD-YBCO films on the buffered metal tape. FE-SEM and XRD were used to investigate the surface morphologies and the texture of the meter-long YBCO films. The end-to-end critical current $(I_c)$ of 63A/cm-width and the critical current density $(J_c)$of $0.9MA/cm^2$ with the thickness of $0.7{\mu}m$ were obtained in the 0.42m long coated conductor.

• 한국초전도ㆍ저온공학회논문지
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• 제22권3호
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• pp.13-19
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• 2020

This study presents the experiment and simulation results on the magnetic field response and electrical stability behaviors of no-insulation (NI) and metal insulation with stainless steel tape (MI-SS) which wound in form of racetrack type coils. First of all, the structural design of the racetrack type bobbin was shown along with its parameters. Then, the current-voltage tests were carried out to measure the critical current of both test coils. Also, the sudden discharging and charging tests were performed in the steady state to estimate the decay field time and magnetic field response, respectively. Finally, the overcurrent tests were conducted in the transient state to investigate the electrical stability of these test coils. Based on the experimental results, the contact surface resistances were calculated and applied to the field coils (FCs) of 10-MW-class second generation high temperature superconducting generator (2G HTSG) used in wind offshore environment. The charging delay time and electrical stability for NI and MI-SS HTS FCs of 10-MW-class 2G HTSG are analyzed by the equivalent circuit model and the key parameters which were obtained from the electromagnetic finite element analysis results.

• 마이크로전자및패키징학회지
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• 제8권1호
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• pp.53-59
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• 2001

Surfaces of PTFE and PVDF were modified by ion-assisted reaction (IAR) in which 1 keV $Ar^{+}$ ions were irradiated on the surface of the polymer with varying ion dose in an oxygen gas environment, and Cu, Pt, Al and Ag thin films were deposited on the modified polymers. Wettability of the modified polymers was largely improved by the formation of hydrophilic groups due to chemical reaction between polymer surface and the oxygen gas during IAR. The change in wettability in the modified polymers was also related to the change in surface morphology and roughness. Adhesion between metal films and polymers modified by IAR was significantly improved, so that no detachment was possible in the $Scotch^{TM}$ tape test. The increase of adhesion strength between the metal film and the modified PVDF was mainly attributed to the formation of hydrophilic groups, which interacted with the metal film. In the case of the modified PTFE, the enhanced adhesion to metal film could be explained by the change in surface morphology together with the formation of hydrophilic groups. The electrical properties of the metal films on the modified polymers were also investigated.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.339-339
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• 2002

In the RABiTS approach to coated conductor development, successful (both economic and technological) depends on the refinement and optimization of each of three important components: the metal tape substrate, the buffer layer(s), and the HTS layer. Here we will report on the ORNL approach and progress in each of these areas. - Most applications will require metal tapes with low magnetic hysteresis, mechanical strength, and excellent crystalline texture. Some of these requirements are competing. We report on progress in obtaining a good combination of these characteristics on metal alloys of Ni-Cr and Ni-W. - The deposition of appropriate buffer layers is a crucial step. Recently, base research has shown that the presence of a stable sulfur superstructure present on the metal surface is needed for the nucleation and epitaxial growth of vapor-deposited seed buffer layers such as YSZ, CeO$_2$ and SrTiO$_3$. We report on the details and control of this superstructure for nickel tapes, as well as recent results for Cu and Ni-13%Cr. - Processes for deposition of the HTS coating must economically provide large values of the figure-of-merit for conductors, current x length. At ORNL, we have devoted efforts to a precursor/post-annealing approach to YBCO coatings, for which the deposition and reaction steps are separate. We describe motivation for and progress toward developing this approach. - Finally, we address some issues for the implementation of coated conductors in real applications, including the need for texture control and electrical stabilization of the HTS coating.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.976-978
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• 2003

Quench characteristics of HTS tapes, which are applied over-current were investigated. When the applied current exceeds the critical current of HTS tapes, the superconductor of HTS tape comes to be changed into normal conductor so that the current begins to flow through the metal sheath, which is made of good electrical conductor. In this study, the current, corresponds to 10 times $I_c$ was fed to HTS tapes. Using the V-I curves and resistance with temperature variation of HTS tapes, the distribution of the applied current between superconductor and metal sheath was analyzed. As the results, we could acquire the duration and magnitude of current to reach to thermal quench.

• 한국주조공학회지
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• 제14권6호
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• pp.576-589
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• 1994

Water modeling experiments and computer simulation for the predictions of defects of die castings are very important to produce high quality castings with less cost. The relation between the variable air vent system and the characteristics of the fluid flow in the die cavity is studied by using water modeling tests, which give ideas on reasonable designing of die cavity, vent arrangement and gating system. In order to test the water modeling, injection is done by using water containing NaCl. Flow behaviors in cavities are visualized by high speed camera and video tape recorder, and local filling time is measured with electrode sensors. Special attention is paid to the configuration of die cavity. Simulated results by computer are examined and compared with the results of water modeling experiments. There are close correlations between the simulated results and water modeling ones.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2444-2448
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• 2007

The multi channel of DDI which is the core part of the LCD-TV has been propelled. When multi channel in DDI is introduced, it brings a thermal problem because of the increased power. To solve the thermal problem of the DDI it needs to be investigated each at the package level and module level. It is important to extract the junction temperature(Tj) of DDI clearly from the system level. The objective of this research is to construct a compact model. The compact model is to reduce LCD module including DDI. When the compact model is used, it will be able to easily handle the boundary condition and accurately predict the temperature. Consequently, the temperature of DDI can be calculated easily at the system level. Through this research,we also proposed the cooling plan of DDI for a protection of overheating. The cooling plan was utilized in DDI design.

• Applied Science and Convergence Technology
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• 제24권5호
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• pp.162-166
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• 2015

Linear ion beams have been introduced for the ion beam treatments of flexible substrates in roll-to-roll web coating systems. Anode layer linear ion sources (300 mm width) were used to make the linear ion beams. Oxygen ion beams having an ion energy from 200 eV to 800 eV used for the adhesion improvement of Cu thin films on PET substrates. The Cu thin films deposited by a conventional magnetron sputtering on the oxygen ion beam treated PET substrates showed Class 5 adhesion defined by ASTM D3359-97 (tape test). Argon ion beams with 1~3 keV used for the ion beam sputtering deposition process, which aims to control the initial layer before the magnetron sputtering deposition. When the discharge power of the linear ion source is 1.2 kW, static deposition rate of Cu and Ni were 7.4 and $3.5{\AA}/sec$, respectively.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.329-333
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• 1999

The BSCCO 2223 Ag-sheathed tapes were prepared with spray dried precursor powders, which are of different starting condition. The J$_c$ in the short tapes varied from 24 kA/ cm$^2$ to 47 kA/ cm$^2$ at 77K and 0T. The largely improvement of J$_c$ in certain tape, which characterized with the large textured BSCCO 2223 grains, homogeneity of reactant and fewer tracks of second phases in final superconducting matrixes, could be due to optimization in the precursor powder.