Development of Bulk Bi2+xSr3-yCa yCu 2O8+delta Superconductors by Partial-Melting Route for Fault Current Limiters Application
01 Jun 2002-Materials Research-ibero-american Journal of Materials (Materials Research)-Vol. 5, Iss: 2, pp 179-186
TL;DR: In this article, the production of bulk Bi2+xSr3-yCayCu 2O8+D (Bi-2212) superconductors for fault current limiter application was developed via a partial-melting route.
Abstract: The production of bulk Bi2+xSr3-yCayCu 2O8+D (Bi-2212) superconductors for fault current limiter application was developed via a partial-melting route. Aiming high Ic (critical current), which is the essential superconducting characteristic for application of this material in the construction of Fault Current Limiters (FCL), the produced blocks have predominance of Bi-2212 phase (83 wt%), which characterizes with high values of zero and onset transport critical temperature of 92K and 97.5K, respectively. A relatively low transition width, DT, from the superconducting to the normal state of 5.5K, revealed a good intergrain connectivity. Consequently, current measurements on the blocks of Bi-2212 show promising Ic values of 230A and 850A for direct and alternate current, respectively. It is expected that further increases in the Ic values will depend on the elimination of an observed amorphous phase and further reduction of amount and grain sizes of secondary phases, still present in the blocks obtained by the proposed partial-melting route. This may be achieved by a further optimization of the partial-melting processing parameters.
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TL;DR: The melting and solidification behavior of Bi2Sr2Ca2Cu3 O10 (Bi-2223) precursors has been studied in this article, where each sample was made by packing a precursor powder into a silver crucible, in order to approximately simulate the situation found in 2223 silver-sheathed tapes.
Abstract: The melting and solidification behavior of Bi2Sr2Ca2Cu3 O10 (Bi-2223) precursors has been studied. Nominal compositions corresponding to excess of liquid, Ca2CuO3 and CuO have been investigated. Each sample was made by packing a precursor powder into a silver crucible, in order to approximately simulate the situation found in 2223 silver-sheathed tapes. The samples were partially melted and then slow-cooled, being quenched from different temperatures and analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDS). The precursors decomposed peritectically during melting, forming liquid and solid phases. Very long plates with compositions falling in the vicinity of the 2223 primary phase field formed upon slow-cooling. The 2223 phase may have been formed and the results suggest that long grains of this phase might be obtained by melting and crystallization if the exact peritectic region and the optimum processing conditions are found.
14 citations
Posted Content•
TL;DR: In this paper, it was shown that Ag does not enter the crystallographic structure of the superconductor and segregates on the grain boundary region and this was confirmed from the temperature dependence of the critical current density and mutual inductance.
Abstract: Bulk LaBa_2Cu_3O_(7-y) samples with different Ag additions were investigated. It was shown that Ag does not enter the crystallographic structure of the superconductor and segregates on the grain boundary region. Current path in these samples occurs through the proximity connected grains and this was confirmed from the temperature dependence of the critical current density and mutual inductance. By using the theory developed for the thin film structures we conclude that growing of the Ag content increased the effective cross section and the normal metal thickness. The first one prevails at low concentration increasing the current. The second dominates at higher concentration leading to saturation or even lowering of the critical current.
4 citations
Dissertation•
11 Mar 2016
TL;DR: In this article, the authors propose a decouplage-based approach for the detection of IRM signals in microscopie IRM, based on the use of champs statiques eleves.
Abstract: En microscopie IRM, la sensibilite de detection est critique pour obtenir des images avec un rapport signal sur bruit suffisant car l’intensite du signal RMN devient extremement faible. Une strategie alternative a l’utilisation de champs statiques eleves consiste a ameliorer les performances des antennes radiofrequences qui detectent le signal d’IRM. Plus particulierement, la strategie dans laquelle s’inscrit ce travail de these vise a exploiter la haute sensibilite des antennes miniatures supraconductrices basees sur le principe des resonateurs monolithiques a ligne de transmission avec comme objectif a terme la mise en reseau de ce type d’antennes. Le developpement d’un tel reseau represente un enjeu instrumental majeur car cela permet de profiter de la haute sensibilite intrinseque des antennes miniatures supraconductrices tout en autorisant l’observation de zones etendues ou en profondeur. Cependant, les caracteristiques geometriques de ces antennes et la nature des materiaux utilises posent des difficultes importantes pour realiser les operations d’accord, d’adaptation, ou decouplage mutuel lors de leur utilisation en IRM. Dans le cadre de cette these, nous avons conduit des travaux abordant ces differentes problematiques et permettant la mise œuvre d’un reseau supraconducteur pour l’imagerie haute resolution a champ clinique.Nous avons developpe en premier lieu un systeme permettant de realiser automatiquement et sans contact l’accord et l’adaptation des antennes miniatures monolithiques. Ce systeme utilise des techniques, basees sur le couplage electrique et magnetique, que nous avons prealablement etudiees en utilisant differentes methodes. Les performances de ce systeme ont ete etudiees et la faisabilite de sa mise en œuvre dans une experience d’IRM a ete etablie.Nous avons aborde en second lieu le probleme de decouplage mutuel des elements constituant un reseau. Pour cela, des techniques de decouplage potentiellement compatibles avec les antennes miniatures supraconductrices ont ete etudiees. En particulier, la technique de decouplage par anneau de blindage a ete investie en profondeur, par simulation numerique et experimentalement, et nous avons developpe un modele analytique d’optimisation du niveau de decouplage accessible par cette technique. Nous avons mis en œuvre et valide cette technique avec des reseaux en cuivre de quatre antennes et des premiers essais ont ete conduits avec un reseau constitue de deux antennes miniatures supraconductrices.
4 citations
Cites background from "Development of Bulk Bi2+xSr3-yCa yC..."
...10 Tension aux bornes d’un fil supraconducteur BSCCO en fonction de l’amplitude de courant, tirée de [46]....
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TL;DR: In this paper, partial melting and solidification of Bi-2212:Ag precursor powder were investigated in situ by XRD in a synchrotron radiation facility and the result of this experiment allowed a design of heat treatment conditions for Bi-212 block processing, including maximum processing temperature, holding time, cooling rate and annealing time.
4 citations
TL;DR: In this paper, the impact of silver addition on granularity of NdFeAsO 0.8 F 0.2 superconductor was investigated and the results showed that limited addition of Ag improves the granular coupling of superconducting grains of NdyFeAs o 0.
Abstract: We report the impact of silver addition on granularity of NdFeAsO 0.8 F 0.2 superconductor. The ac susceptibility and electrical resistivity under magnetic field are measured to study the improvement in weak links of NdFeAsO 0.8 F 0.2 with addition of Ag x ( x = 0.0–0.3). The Ag free NdFeAsO 0.8 F 0.2 compound shows superconductivity at around 51.8 K. Typical two step superconducting transitions due to the inter- and intra-grain contributions, induced from the combined effect of superconducting grains and the inter-granular weak-coupled medium respectively are clearly seen in susceptibility [ χ ( T )] plots. In comparison to the pure NdFeAsO 0.8 F 0.2 compound, the coupling between the superconducting grains is significantly improved for 20 at% silver doped sample, and the same is deteriorated for higher Ag content i.e., for 30 at%Ag sample. The magneto transport measurements ρ ( T ) H of polycrystalline 20 at% Ag doped NdFeAsO 0.8 F 0.2 exhibited the upper critical filed [ H c2 (0)] of up to 334 T, which is slightly higher than the one observed for pure NdFeAsO 0.8 F 0.2 . The flux flow activation energy ( U 0 / k B ) varies from 7143.38 K to 454.77 K with magnetic field ranging from 0 T to 14 T for 20 at% Ag doped NdFeAsO 0.8 F 0.2 . In this investigation, our results show that limited addition of Ag improves the granular coupling of superconducting grains of NdFeAsO 0.8 F 0.2 compound.
3 citations
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TL;DR: In this paper, a pure 110 K phase of the Bi-Pb-Sr-Ca-Cu-O superconductor was obtained by co-decomposition of metal nitrates and a solid reaction under low oxygen pressure.
Abstract: A pure 110 K phase of the Bi-Pb-Sr-Ca-Cu-O superconductor was obtained by co-decomposition of metal nitrates and a solid reaction under low oxygen pressure. The best starting compositions were in the region close to Bi1.84Pb0.34Sr2Ca2Cu3Oy with a little excess of Ca and Cu. In this region, the samples showed the absence of the 80 K and semiconducting phase, and there was no indication of impurities at all. The 110 K phase without stacking faults is stabilized by the addition of Pb, so that the nominal composition close to the ideal one is required at the start. A little excess of Ca and Cu, however, effectively decreases the 80 K phase.
204 citations
TL;DR: In this article, the results of studies of crystal chemistry and phase equilibria are presented to give materials scientists a comprehensive insight into the phase equilibrium and crystal chemistry of these challenging materials.
Abstract: Ten years after the discovery of high-Tc superconductivity in the system Bi-Sr-Ca-Cu-O, the superconducting compounds have been identified, and their structures, crystal chemistry, phase equilibria, and properties have been extensively investigated. In this review, the results of studies of crystal chemistry and phase equilibria are presented to give materials scientists a comprehensive insight into the phase equilibria and crystal chemistry of these challenging materials.
84 citations
TL;DR: The Melt Cast process (MCP) is highly flexible to manufacture BSCCO 2212 bulk parts in a large variety of shapes and dimensions as mentioned in this paper, and it also allows the integration of current contacts during the fabrication process thus leading to HTS parts which can directly be integrated into electrotechnical devices, the ease of mechanical treatment of the material by machining methods offers additional options for the MCP bulk parts.
Abstract: The Melt Cast process (MCP) is highly flexible to manufacture BSCCO 2212 bulk parts in a large variety of shapes and dimensions. MCP also allows the integration of current contacts during the fabrication process thus leading to HTS parts which can directly be integrated into electrotechnical devices, The ease of mechanical treatment of the material by machining methods offers additional options for the MCP bulk parts. Critical current densities of 2.5-4 kA/cm/sup 2/ are obtained in selffield, about 1 kA/cm/sup 2/ are measured in full rods. High DC (6.4 kA) and AC (10 kA) transport currents are obtained in large tubes (O 70 mm, L 200 mm) at 77 K. Different prototypes and a first application, each of low loss hybrid current leads, have been produced as well as functional models for current limiting and for shielding. >
43 citations
TL;DR: In this paper, it was shown that a homogeneous voltage of more than 1 V/cm can be established over the whole length of the sample leading to a substantial limiting of short circuit current.
Abstract: It is demonstrated that melt cast processed (MCP) BSCCO 2212 bulk material is an excellent candidate for resistive superconducting current limiters. For rod shaped samples it could be shown that a homogeneous voltage of more than 1 V/cm can be established over the whole length of the sample leading to a substantial limiting of short circuit current. The require long lengths of superconducting material can be easily obtained by machining the MCP-tubes into (bifilar) coils. The measured critical current density and its homogeneity over these large lengths were determined and proven to be sufficient for the designated application.
36 citations
TL;DR: In this paper, a simple annealing procedure was developed to precipitate Bi 2+ x Sr 2− x CuO 6+ d, Sr 14 Cu 24 O 41− x and Bi 2 Sr 3 O 6 in high-temperature superconducting “Bi 2 Sr 2 CaCu 2 O 8 ” ceramics.
Abstract: From a consideration of the phase equilibrium diagram of the system Bi 2 O 3 SrOCaOCuO, a simple annealing procedure was developed to precipitate Bi 2+ x Sr 2− x CuO 6+ d , Sr 14 Cu 24 O 41− x and Bi 2 Sr 3 O 6 in high-temperature superconducting “Bi 2 Sr 2 CaCu 2 O 8 ” ceramics. The transformation results in a four-fold increase of the critical current density at 0.5 to 1 T, which is believed to reflect the increased pinning properties of these ceramics by second-phase precipitates.
36 citations