Earticle

The characteristics of Bi2212 round wire was systematically studied depending on different heat treatment conditions. Initial wire was drawn after routine PIT (Powder In Tube) process. The wire was divided into 3 pieces with 10 cm in length and 2.5 mm in diameter, 3 wires were pre-heat treated separately by different heat treatment schedules, heated in air and nitrogen atmosphere and centrifugally melted. Pre-heated wires were annealed at 845 "C for 40 hours in oxygen atmosphere. SEM results indicate that all pre-heated wires showed highly oriented microstructure. However the wire by centrifugally melted process showed higher density and better electric properties as compared with 2 other wires pre-heated in air and nitrogen atmosphere. The critical current of a centrifugally melted wire was about 18 A in 77 K.

The effect of annealing time in Metal Organic Deposition(M0D) method was investigated at reduced total pressure. As the total annealing pressure was reduced, the growth rate of YBCO films increased from 0.14nm/sec at atmospheric pressure to 4.2nm/sec at 1 Torr. For the total pressure of 700, 500, 300, 100, and lTorr, the optimal annealing times of 60, 40, 20, 10, 2minutes were found in our experimental conditions. When the annealing time was short, poor crystallinity or un-reacted phase was obtained. Also, the degradation of YBCO films occurred when exposed longer to the humid ambient at the high annealing temperature. The reduced pressure was found effective to increase the growth rate and to control the pore size of the YBCO films in MOD method. A fast growth of MOD-YBCO films was realized with high critical current density over 1MA/cm2 using reduced pressure annealing. Large pores, usually observed at atmospheric pressure in MOD method, disappeared and also, the number of pores was reduced

Batch type co-evaporation EDDC (Evaporation using Drum in Dual Chambers) system was recently manufactured to fabricate 100m - long SmBCO superconducting coated conductor. As a preliminary study before the fabrication of long tape, short CC samples have been fabricated using the EDDC system and their crystal texture and Ic properties were investigated. 1.2 ㎛-thick SmBCO layers were deposited on CeO2/YSZ/CeO2 buffered Ni-W tapes. Ic of 128A/cm-w and corresponding Jc of 1.1 MA/cm2 at 77K in self-field were obtained for SmBCO CC tape. In-field property of SmBCO CC was confirmed to be better than that of YBCO deposited by PLD.

The effect of the addition of the nano size Y2O3 powder on the microstructurte and superconducting properties of YBCO thin film deposited on LAO single crystalline substrate by TFA-MOD method was studied. Nano size Y2O3 powder was added to the stoichiometric precursor solution with a cation ratio of Y : Ba : Cu = 1 : 2 : 3 prepared using TFA as chelating agent. Precursor solutions with and without Y2O3 addition were coated on LaAlO3(100) single crystalline substrates by dip coating method. Calcination and conversion heat treatments were performed in controlled atmosphere containing moisture Current carrying capacity(Jc) of YBCO film was enhanced about 50 % by Y2O3 doping and it is thought to be due to the better connectivity of YBCO grains and/or the flux pinning by the Y2O3 particles embedded in YBCO grains.

We obtained in-situ MgBz thin films in an one-step process using ESSD (Evaporation Sputtering Simultaneous Deposition) method. In our approach, the Ma evaporator is designed specially. Mg and B are simultaneously evaporated and sputtered, respectively, in the specially designed ESSD chamber. The background pressure was less than 1 x 10-6 Torr. The substrate temperature was kept at 623 K. The film properties were investigated by both electrical resistivity and PPMS. As a result, typical Tc of films was 11 K.

For mechanical and electrical stability and environment protection, Cu and stainless steel stabilizers are laminated to a Ag layer to produce a composite neutral-axis(N-A) architecture in which the YBCO layer is centered between the oxide buffered metallic substrate and stabilizer strip lamination. This architecture allows the wire to meet operational requirements including stresses at cryogenic temperature, winding tensions as well as mechanical bending requirements including thermal and electrical stability under fault current conditions. We have experimentally studied mechanical properties of the laminated stainless steel and Cu stabilizers on YBCO coated conductors. We have laminated YBCO coated conductors by continuous dipping soldering process. We have investigated lamination interface between solder and stabilizer of the YBCO coated conductor. We evaluated bonding properties, tensile / shear bonding strength, and peeling strength laminated YBCO coated conductors.

We propose a replication method to solve the problem of large percent failure in texturing processes of coated conductors. This problem is due to the individual texturing process for each coated conductor that is very long tape having no single defect spot. We tested two different methods of replication process that are based on a well-textured Ni template. First method has structure of Ni/BaO/STO/CeO2/SmBCO/Ag. So BaO layer is dissolved in water that we can separate STO/CeO2/SmBCO/Ag layers. In this processing, the property of STO is conserved but the superconductivity of SmBCO is deteriorated. So we can consider another method. Second method has structure of template (STO)/BaO/STO/Pt/STO. After dissolving BaO then we deposited YBCO. The result of these experiments showed the feasibility of replication

Simplification of the buffer architecture in the fabrication of coated conductors is required because the deposition of multi-layers leads to a longer production time and a higher cost of coated conductors. In this study, a single layered buffer deposition of CeO2 for low cost coated conductors has been tried using thennal evaporation technique. 100nm-thick CeO2 layers deposited by thermal evaporation were found to act as a diffusion layer. 0.4㎛-thick SmBCO superconducting layers were deposited by thermal co-evaporation on the CeO2 buffered Ni-W substrate. Critical current of 55.4 A/cm2 was obtained for the SmBCO coated conductors.

Oxide buffer layers for YBCO coated conductors were fabricated using MOD processing and development of microstructure and texture were investigated. A CeO2, buffer layers were formed on RABiTS tape. Acetate-based precursor solution was employed to synthesize the precursor solution. Subsequently, the precursor solution was stabilized and modified with triethanolamine. CeO2 precursor gel film was coated and annealed in Ar/H2 atmosphere at high temperature. An annealed CeO2 film shows mixed orientation with high (001) texturing. It was shown that (111)texture of CeO2 layers were enhanced by multiple coating. This degradation was attributed to development of microcracks in the multiply coated CeO2 films. Also discussed are the synthesis and the characterization of La2Zr2O7 (LZO) buffer layers on RABiTS tape. A biaxially textured LZO buffer layer was fabricated with MOD processing method using metal alkoxide based precursor solution. It was shown that the LZO film were epitaxially grown on RABiTS tape and crack-free & uniform surface was obtained after annealing in Ar/H2 atmosphere.

This study introduced waste water treatment method by superconducting HGMS(High Gradient Magnetic Separation). HGMS treatment method is high efficient method for various waste water. we have surveyed superconducting magnetic separation technology. We fabricated the prototypes of magnetic matrix filter consisting of stainless steel mesh, which is a core component in the magnetic separation system. In our basic preliminary experiment using HGMS, it was made clear that the fine para-magnetic particles in the wasted water obtained from steelmaking process of POSCO can be separated with high efficiency.

The conduction-cooled HTS SMES is operated in cryogenic and high vacuum condition. Thus, Insulation design at cryogenic temperature and high vacuum is a key and an important element that should be established to accomplish compact design is a big advantage of HTS SMES. However, the behaviors of insulators for cryogenic conditions in vacuum are virtually unknown. Therefore, active research and development of insulation concerning application of the conduction cooled HTS SMES was needed. In this study, the insulation characteristics at experimented high vacuum and cryogenic similar to running condition of SMES system. Also, investigated about insulation character-istics of suitable some materials to insulator for conduction-cooled HTS SMES. As these results, the basis data was obtained for insulation materials selection and insulation design for development of 600kJ class conduction-cooled HTS SMES.

A high temperature supercon-ductor (HTS) has been developed for power applications such as power cables, fault current limiters and superconducting magnetic energy storage devices. For such applications it is required to understand the DC voltage-current characteristic of the HTS, which is important in analyzing AC loss and flux flow loss quantitatively. In this work, we have experimentally investigated influence of several factors. e.g. critical current density, degradation and AC external magnetic field, on the DC voltage-current characteristic. The measured results have been discussed in engineering application point of view.

In this paper, authors developed a real-time simulation algorithm for the power device application of HTS (High Temperature Superconducting)wire by using Real Time Digital Simulator(RTDS) . At present, in order to extend the power capacity of some area where has a serious problem of power quality, especially metropolitan complex city, there are so many problems such as right of way for power line routes, space for downtown substations, and the environmental protection, etc. HTS technology can be useful to overcome this problem. Recently, according to the advanced HTS technology, the power application is being researched well. Simulation is required for safety before installation of HTS power cable, a fabrication model used at the power system simulation. This paper describes a real time digital simulation method for the application of HTS wire to power device. For the simulation analysis, test sample of HTS wire was actually manufactured. And the transient phenomenon of the HTS wire was analysed in the simulated utility power grid. This simulation method is the world first trial in order to obtain much better information for installation of HTS power device into a utility network.

For electric power applications of Bi-2223/Ag superconducting tapes, a transport characteristic is important issue. A transport characteristic is strongly depends on the magnitude and direction of external time-varying magnetic field. To verify a effect of external magnetic field, we manufactured a prototype magnet and obtained transport characteristics with respect to the magnitude , the direction and the frequency of external magnetic field. The data acquired in this paper. will be used as a source for the study of HTS electric power applications which is supposed to carry on.

This paper describes the effect of rotating frequency on the pulse tube of Stirling type pulse tube refrigerator. Various conditions were analyzed by two-dimensional analysis with several dominant non-dimensional parameters. With the additional pressure term influenced by centrifugal force in rotating condition, the linearized conservation equations of mass, momentum, energy of the gas were solved to obtain the first order variables and calculate the enthalpy flow in rectangular coordinates. The rotational effect in pulse tube for the refrigerator's performance were quantitatively evaluated. According to the first order analysis, the enthalpy flow decreases with the rotating speed.