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<正> In this special issue, we present to the readers the current experimental results in theresearch of materials processing, superconducting properties, and industrialapplications. The invited authors in this special issue are prominent researchers in thesuperconductivity community. The readers will be able to find this special issuevaluable and current information in several key areas including thin films, largedomain growth, flux pinning, coated conductors, and MgB_2 synthesis.
2003年03期 241页 [查看摘要][在线阅读][下载 37k] [下载次数：19 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - N.Hari Babu,D.A.Cardwell,C.D.Tarrant,K.R.Schneider
<正> Large grain Y-Ba-Cu-O (YBCO) superconductors doped with various amounts of depleted uranium oxide have been fabricated by top seeded melt growth (TSMG). The effect of depleted UO2 on the large grain microstructure has been studied systematically in samples with and without added Pt. Addition of uranium oxide results in the formation of U-phase particles of dimensions of a few hundred nanometers with an approximately spherical morphology in the superconducting YBa2Cu3O7-δ(Y-123) phase matrix. Addition of Y2O3 to the uranium doped precursor powder, rather than Y-211, yields a significantly finer distribution of second phase particles. The chemical composition of the U-phase particles, found in samples with no Pt addition, has been identified as Y2Ba4CuUOy, which exhibits paramagnetic behaviour. It has been confirmed experimentally that this phase forms during the peritectic solidification process. Magnetic measurements show that U-doped melt processed YBCO exhibits improved critical current densities and
2003年03期 242-250页 [查看摘要][在线阅读][下载 846k] [下载次数：27 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - G.Krabbes,P.Diko,C.Wende,Th.Hopfinger,G.Fuchs
<正> We have investigated the phase equilibria in (RE)BaCuO/Ag systems, the influence of Ag on the processing of (RE)BaCuO/Ag composites and the resulting properties. YBaCuO/Ag composites have been grown by the modified melt crystallization process with YBa2Cu3O7, Y2O3, Pt and Ag2O in the precursor. The improved strength of the YBaCuO/Ag composites compared with the conventional YBaCuO bulk material permitted us to magnetize these materials to achieve trapped fields up to 16 T (at 24 K) in the gap of a mini-magnet. The investigation of the microstructure revealed a remarkable increase of the spacing between micro-cracks especially of those perpendicular to a/b-planes when 12wt%Ag was added. In the case of SmBaCuO/Ag composites, Ag has a strong influence on processing and causes interactions between RE123 seeds and the sample. We show the growth of single-grain SmBaCuO/Ag composites in air and discuss the influence of post-annealing on increasing Tc and Jc. Furthermore, YBaCuO/Ag composites have been shown to
2003年03期 251-265页 [查看摘要][在线阅读][下载 2064k] [下载次数：29 ] |[网刊下载次数：0 ] |[引用频次：3 ] |[阅读次数：0 ] - R.Weinstein,A.Gandini,R.Sawh,D.Parks
<正> The motivation for continuous columnar pinning centers has been to provide maximum Upin. It has been assumed that this provides the best Jc and Bpin. Limitations on Jc and Spin observed for columnar pinning have been attributed to degradation of the order parameter and Tc. We examine columnar pinning by ionic damage and conclude instead that geometrical effects of columnar pinning on percolation path and on the number of pinning centers are the dominant limitations of columnar pinning, leading to a limit of Bpin- 4 T. Evidence suggests that multiple-in-line-defects (MILD) are far better suited to increase Jc and Bpin. The morphology of MILD pinning is reviewed. Ion energy loss per unit distance, Se, is found to be most promising in a regime almost diametrically opposite to that sought to maximize Upin. We expect Jc - 106 A/cm2 and Bpin > 40T from MILD pinning, despite sharply decreased Upin. Experimental confirmation is proposed.
2003年03期 266-279页 [查看摘要][在线阅读][下载 919k] [下载次数：22 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - M.R.Koblischka
<正> Volume pinning forces were determined for a variety of bulk high-Tc superconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various temperature ranges were identified. The Nd-based superconductors and some YBCO crystals exhibited a dominating pinning of the δTc-type (i.e. , small, superconducting pinning sites). In contrast to this, the addition of insulating 211 particles provided pinning of the δ/-type; providing effective pinning in the entire temperature range acting as a "background" pinning mechanism for the peak effect. Due to the small coherence lengths of the high-Tc compounds, effective pinning sites are defects or particles of nanometer size relative to ζ3. Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) revealed that practically all high-Tc compounds were spatially inhomogeneous, which could be caused by oxygen deficiency (YBCO)
2003年03期 280-291页 [查看摘要][在线阅读][下载 673k] [下载次数：36 ] |[网刊下载次数：0 ] |[引用频次：3 ] |[阅读次数：0 ] - E.S.Reddy,G.J.Schmitz
<正> The fabrication of near-net-shaped objects of RE123 superconductors by "infiltration processing" is discussed. Near-net-shape processing involves the infiltration of preshaped porous green bodies of either 211 or yttria phases by liquids containing barium cuprates and copper oxides followed by a controlled peritectic solidification. The process yields poly- and also single-crystalline superconducting objects with a shrinkage of less than half of one percent of the green bodies. The preservation of the initial structure of the green bodies results in fabrication of RE 123 in a wide variety of dimensions and complex shapes. The demonstrated products include bulk components like cylinders, single domain thick films on a variety of substrates, freestanding fabrics and open porous superconducting foams. This paper presents a comprehensive description of the infiltration processing technique and the resulting microstructures of the superconducting bodies. The advantages of this technique and practical applica
2003年03期 292-306页 [查看摘要][在线阅读][下载 1713k] [下载次数：27 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - H.K.Liu,S.H.Zhou,S.Soltanian,J.Horvat,A.V.Pan,M.J.Qin,X.L.Wang,M.Lonescu,S.X.Dou
<正> The discovery of superconductivity in magnesium diboride (MgB2) has opened up a new field in materials science research. It offers a possibility of a new class of high performance superconducting materials for practical applications because of the relatively low cost of fabrication, high critical current densities (Jc) and fields, large coherence length, absence of weak links, higher Tc(TC = 39K) compared with Nb3Sn and Nb-Ti alloys (two or four times that of Nb,,Sn and Nb-Ti alloys). However, the weak flux pinning in the magnetic field remains a major challenge. This paper reports the most interesting results on nanomaterial (SiC and Si) doping in magnesium diboride. The high density of nano-scale defects introduced by doping is responsible for the enhanced pinning. The fabrication method, critical current density, microstructures, flux pinning and cost for magnesium diboride bulks, wires and tapes are also discussed. It is believed that high performance SiC doped MgB2 will have a great potential for m
2003年03期 307-315页 [查看摘要][在线阅读][下载 518k] [下载次数：43 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - 冯勇,阎果,赵勇,吴晓京,周廉,张平祥
<正> We prepared a series of MgB2 bulk samples under different temperatures, holding time and increasing rates in temperature by the solid state reaction. The thermodynamic behavior and phase formation in the Mg-B system were studied by using DTA, XRD and SEM. The results indicate that the formation of the MgB2 phase is very fast and the high increasing rate in temperature is necessary to obtain high quality MgB2. In addition, the effects of the Zr-doping in Mg1-xZrxB2 bulk samples fabricated by the solid state reaction at ambient pressure on phase compositions, microstructure and flux pinning behavior were investigated by using XRD, SQUID magnetometer, SEM and TEM. Critical current density Jc can be significantly enhanced by the Zr-doping and the best data are achieved in Mg0.9Zr0.1B2. For this sample, Jc values are remarkably improved to 1. 83 × 106 A/cm2 in self-field and 5. 51 × 105 A/cm2in 1T at 20K. Also, high quality MgB2/Ta/Cu wires and tapes with and without Ti-doping, MgB2/Fe wires and 18 filamen
2003年03期 316-333页 [查看摘要][在线阅读][下载 1629k] [下载次数：47 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] - C.Villard,C.Peroz
<正> The behavior of YBCO/metal bilayers under transport currents was explored in the framework of fault current limitation (FCL). Properties of the superconducting-normal transition were first studied phenomenologically during sweep current experiments. For current rates higher than 500 A/s, the transition into the normal state was based on non-thermal phenomena and was characterized by a flux creep regime ended by a jump into the normal state. At lower sweep rates, a total diversion of the current in the metallic shunt was observed for temperatures higher than 85K. In this regime, a partial recovery of the superconducting state took place due to a finite thermal resistance between the superconducting and the metallic films. These two properties of partial diversion into the shunt and of fast switching for a quick rise of the current during a default were exploited for current limitation at 77 K. FCL experiments at 50 Hz show that YBCO/Au bilayers limit the current in about 1ms at a value of 2. 5/c by devel
2003年03期 334-341页 [查看摘要][在线阅读][下载 446k] [下载次数：40 ] |[网刊下载次数：0 ] |[引用频次：3 ] |[阅读次数：0 ] - 徐永利,时东陆
<正> The developments of coated conductor technology have been reviewed. It is shown that the critical current density of high-Tc wires can be greatly enhanced by using three-fold approaches: grain alignment, grain boundary doping, and optimization of the grain architecture. Major advances have been made in the last 16 years mainly in three aspects: substrates, buffer layers and the YBCO layer. Cost is still the main concern for scale up, especially for the approach through vapor depositions, such as the PLD method. TFA-MOD or other CSD methods may be the trend to overcome cost and speed consideration during the scale up. However, high reliability and reproducibility will be the new focus for these techniques. Ni-alloy tapes seem to have advantages over pure Ni in terms of mechanical strength and oxidation resistance. Depositing a pure Ni layer on top of Ni-based alloys (such as Ni-Cr and Ni-W alloys) solves the problem of low strength of Ni and poor texture of Ni alloys. The RABiTS and IBAD are the two robu
2003年03期 342-369页 [查看摘要][在线阅读][下载 1970k] [下载次数：80 ] |[网刊下载次数：0 ] |[引用频次：20 ] |[阅读次数：0 ] - J.H.S.Torres,Y.Kopelevich
<正>We show that the second magnetization peak(SMP),i.e.,an increase in the magnetization hysteresis loop width in type-11 superconductors,vanishes for samples smaller than a critical size,We argue that the SMP is not related to the critical current enhancement but can be well explainde within a frameword of the thermomagenetic flux-jump in stability theory,where flux jumps reduce the absolute irreversible magnetization relative to the isothermal critical state value at low enough magnetic fields.The recovering of the isothermal critical sate with increasing field leads to the SMP.The low-field SMP takes place in both low-T.conventional and high*t.unconventional superconductors.Our results show that the rsstoration of the isothermal critical state is rsponsible for the SMP occurrence in both cases.
2003年03期 370-378页 [查看摘要][在线阅读][下载 480k] [下载次数：17 ] |[网刊下载次数：0 ] |[引用频次：0 ] |[阅读次数：0 ] - 信赢
<正>The first TI一based euprate supereonduetor,TI一Ba-Cu一(),was diseovered by 2.2.Sheng and A.M.Hermann仁1〕. TI beeomes supereondueting at 2.38 K.NumerousTI eompounds and alloys are supereondueting.TIMo6Ses has the highest transition temperature of1 2.2 K among all non一euprate Tl eontaining alloyand eompound supereonduetors.Before thediseovery of the euprate supereonduetors,some TIeontaining oxide supereonduetors were found,among whieh TI。.3W()3 has the highest transitiontemPerature,2.14 K. Sinee the diseovery of TI euPratesuPereonduetors,two distinet families have beenidentified.Soon after the diseovery of TI一Ba一Cu-(),supereonduetivity was eonfirmed in TI一Ba一Ca-Cu一()samples.The ehemieal eompositions anderystal struetures of those eompounds were workedout as T12BaZCu()6,T12BaZCaCuZ()。,andT12BaZCaZCu3OI。[2〕.This 15 the first family of TIeuPrate supereonduetors,whieh features two TIatoms in eaeh ehemieal formula.
2003年03期 379-388页 [查看摘要][在线阅读][下载 574k] [下载次数：27 ] |[网刊下载次数：0 ] |[引用频次：1 ] |[阅读次数：0 ] 下载本期数据