• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.31-34
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• 2003

Bi-2223 superconducting wires with 55 filaments were fabricated by stacking, drawing process with different heat-treatment histories. Two kinds of powders were prepared. One was pre-annealed at 760-820 $^{\circ}C$ and low oxygen partial pressure, and the other was only calcined state. Before rolling process, round wires were pre-annealed at 760 -820 $^{\circ}C$ and in a low oxygen partial pressure. We confirmed that pre-annealing step was to transform Bi-2212 orthorhombic structure from Bi-2212 tetragonal structure and to reduce the formation of second phases at superconducting wire. However Bi-2223 phases were formed at higher pre-annealing temperature. Bi-2223 conductor was needed frequently annealing at low temperature because pre-annealing at precursor powder brought about decrease in workability. We could achieve highest Je of 6500 A/$\textrm{cm}^2$ at the tape using Bi-2212 orthorhombic phase by introduced slightly overheating at the 1st sintering process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.190-190
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• 2010

The resistance and recovery properties of the YBCO thin-film wire according to the existence and thickness of an insulting layer, and the kinds of stabilization layers, were analyzed at 90 K, 180 K and 250 K. In this study, YBCO thin-film wires with different stabilizing layers and with insulating layers were examined in terms of their various characteristics, such as quenching occurrence, spread, and distribution, based on their resistance increase trends and their recovery from quenching, and the results were qualitatively explained. The results of this study on the characteristics of YBCO thin-film wires' superconducting and normal-conducting phase changes are expected to be useful in designing superconducting power machines and in improving their performance.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1521-1523
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• 2000

NbTi/Cu superconducting wires were jointed inserting the NbTi filaments into Cu/NbTi sleeve and pressing it. When the NbTi filaments were inserted into Cu/NbTi sleeve additional NbTi filaments were inserted together to increase the numbers of filaments in the hole of sleeve. The thickness of sleeves and dimples were changed to get optimal factor for high Ic of joint Critical current of the joint with additional NbTi Filaments and 17mm thickness of dimple was 450 A at 4.2K, 0.5T.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.24-27
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• 2023

Until now, many research activities have been conducted to commercialize high-temperature superconducting (HTS) wires for electric applications. Most of all researchers have focused on enhancing the piece length, critical current density, mechanical strength, and throughput of HTS wires. Recently, HTS magnet for generating high magnetic field shows degraded performance due to the deformation of HTS wire by high electro-magnetic force. The deformation can be derived from widthwise thickness non-uniformity of HTS wire mainly caused by wet processes such as electro-polishing of metal substrate and electro-plating of copper. Gradient sputtering process is designed to improve the thickness uniformity of HTS wire along the width direction. Copper stabilizing layer is deposited on HTS wire covered with specially designed mask. In order to evaluate the thickness uniformity of HTS wire after gradient sputtering process, the thickness distribution across the width is measured by using the optical microscope. The results show that the gradient deposition process is an effective method for improving the thickness uniformity of HTS wire.

• Progress in Superconductivity and Cryogenics
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• v.18 no.2
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• pp.1-4
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• 2016

To observe the superconducting current and structural properties of high critical temperature ($T_c$) superconductors (HTS), we suggest the following imaging methods: Room temperature imaging (RTI) through thermal heating, low-temperature bolometric microscopy (LTBM) and Raman scattering imaging. RTI and LTBM images visualize thermal-electric voltages as different thermal gradients at room temperature (RT) and superconducting current dissipation at near-$T_c$, respectively. Using RTI, we can obtain structural information about the surface uniformity and positions of impurities. LTBM images show the flux flow in two dimensions as a function of the local critical currents. Raman imaging is transformed from Raman survey spectra in particular areas, and the Raman vibration modes can be combined. Raman imaging can quantify the vibration modes of the areas. Therefore, we demonstrate the spatial transport properties of superconducting materials by combining the results. In addition, this enables visualization of the effect of current flow on the distribution of impurities in a uniform superconducting crystalline material. These imaging methods facilitate direct examination of the local properties of superconducting materials and wires.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.570-574
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• 1999

In this paper, by using the electrophoresis, preparation of YBCO superconducting wire deposited on metal Ag base wire was studied with its Properties. YBCO Powder could be prepared by solid state reactions with calcining and sintering processes. Superconducting wire prepared on metal Ag wire used as cathode of deposition base could be also fabricated in the YBCO/acetone-dispersed solution to obtain several tens of re thick films. And then it could be used as superconducting wire for measurement after calcination, sintering and oxygen absorption processes. In the process of film deposition, a catalyst I$_2$added into the suspension solution was very useful for preparing thick film of YBCO, and BaF$_2$ of additive material was also necessary for preparing crack-free wire of YBCO superconductor. As a result, YBCO superconducting wire added 2~3wt.% of BaF$_2$\ulcorner with catalyst, 12 had better deposition condition for uniform and dense YBCO wires, and critical current density, Jc was calculated at the value of 1,458A/$\textrm{cm}^2$(more than 10$^{3}$A/$\textrm{cm}^2$ ,77K, o[T]) of 30${\mu}{\textrm}{m}$ thick sample by 4 point prove method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.2
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• pp.90-93
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• 2018

This aim of this study was to develop a process for creating bulk single-crystal YBaCuO superconductors in a high magnetic field. To support the bulk unidirectional growth of $YBa_2Cu_3O_{7-y}$, $SmBa_2Cu_3O_{7-y}$ seeds were planted inside YBaCuO composites and samples were produced by melting, enabling the growth of two YBaCuO superconductors. Due to the magnetism generated inside the superconductor of the upper sample, the magnetization inside the superconducting single crystals was evenly distributed, the sharpness of the induced magnetic force was improved, and the superconducting magnetization were significantly improved. This approach is widely applicable for the production of superconducting wires and current leads used for DC power breakers.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.104-107
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• 2001

Racetrack coils are used in many areas of superconductivity applications such as generators, motors, maglev, wiggler magnets and so on. Especially now a days a few advanced nations including U.S., Japan are developing high temperature superconducting(HTS) wire which has better performance than low temperature superconducting(LTS) wire. Most of HTS wires such as BSCCO-2223 are manufactured with PIT(Power In Tube) process, so the shape of the wire looks like tape different from LTS wire with round cross-sectional appearance like normal conductors. Generally HTS racetrack coils are composed of a few partial double-pancake colis and then the double-pancakes are jointed each other according to their applications.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.63-66
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• 2003

1 km length of Bi-2223/Ag superconducting wires were fabricated by stacking, drawing process with advanced heat-treatment schedules. Intermediate annealing was carried out to increase the homogeneity and uniformity of the superconducting filaments embedded in the silver matrix. Phase modification from tetragonal to orthorhombic Bi-2212 by pre heat treatment(PHT) was executed to improve the texture and phase transformation of Bi-2223. Drawing stress was measured to Predict the sausaging and stress limit, Rolling parameters such as thickness, width and winding tension were investigated to roll the tape with uniformity. Critical current of 1 km length of superconducting tapes was measured about 50 A continuously after final sintering.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.96-98
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• 2003

Many of research efforts have been focused on the improvement of critical current density Jc of silver-sheathed Bi-2223 tapes for practical applications of material. Bi-2223 superconducting wires with 55 filaments were fabricated by stacking, drawing process with different heat-treatment histories. After rolling process, Bi-2223 tapes were heat-treatment at 780~826$^{\circ}C$ with variable mass flow rate of mixed gas. In this study, the effect of changes in the variable mass flow rate of mixed gas during the heat treatment of Bi-2223/Ag tapes has been investigated. Distinct differences were observed in the Bi-2223 phase and critical current as flow rate of mixed gas. We could achieve proper conditions of mass flow rate of mixed gas for Ag-alloy clad Bi-2223 superconducting tapes.