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1.
《Applied Superconductivity》1997,5(1-6):163-170
Long lengths of silver-clad (Bi,Pb)2Sr2Ca2Cu3O10 (Bi2223) high-Tc multifilamentary tapes were produced using the powder-in-tube (PIT) technique followed by a thermomechanical process. The relationships between microstructure and electrical, magnetic and mechanical properties of the heat treated tape were evaluated from the critical current density measurements, irreversibility magnetic field determination and mechanical bending tests. Emphasis was stressed on the Jc behavior in magnetic fields at different temperatures. A Jc of 10,000 A/cm2 at 77 K in a zero field for a 10 m tape and 75,000 A/cm2 at 23 K in a field of 3 T for a short tape was achieved. The results obtained showed that Bi2223/Ag high-Tc composite tapes are a potential alternative to conventional low-Tc superconductors in magnetic levitation (MAGLEV) applications. 相似文献
2.
Reinforcing multifilamentary Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/Oy (2223-BSCCO) requires careful evaluation of magnetic losses and, in general, of the quantities related to the hysteresis loop (e.g., coercive field and residual magnetization). In this paper, the results of magnetic quantity measurements performed on superconductive tapes reinforced by both AISI 304 and AISI 316 stainless steel layers are discussed. It is shown that the former kind of steel has power losses higher than the latter. Therefore, from this point of view AISI 316 constitutes a better solution than AISI 304 to reinforce BSCCO-Ag tapes. Comparative measurements performed on the steel layer, the superconductor, and the reinforced tape, separately, allow the different contributions to the total magnetic loss to be singled out. In this way, a relationship between the induced voltages in one single steel layer, in a BSCCO-Ag tape without steel, and in the reinforced structure (BSCCO + 2 steel layers) is derived. 相似文献
3.
High temperature Bi10Ag solders with different amounts of Cu were used to investigate the impacts of Cu on the microstructures, melting characteristics, wettability and shear strength of the Bi-10Ag-xCu (x = 0, 0.5, 1, and 2 wt%) solders. A metastable Cu-rich phase was formed due to the addition of Cu. The Cu has negligible effect on the solidus but it can decrease about 6 °C on the liquidus. Doped with 0.5 wt% of Cu, the solders showed the largest melting range in the DSC curves and improved wettability on Cu substrates. When the Cu addition excesses to 0.5 wt%, it will induce negative effects on wettability of the solders on the substrate. Moreover, the addition of Cu has no significant influence on the strength of the Bi10Ag lap solder joints. The Bi-10Ag-0.5Cu solder joint has higher shear strength than that of Pb5Sn. 相似文献
4.
Pradeep Haldar James G. Hoehn U. Balachandran L. R. Motowidlo 《Journal of Electronic Materials》1993,22(10):1295-1297
The powder-in-tube process has been used to fabricate long lengths of flexible, high-Jc, silver-clad Bi-2223 HTS conductors. By improving thermomechanical processing and precursor powder preparation, we have succeeded
in achieving Jc values of≥4×104 A/cm2 at liquid nitrogen (77K) temperature and >105 A/cm2 at liquid helium (4.2K) and liquid neon (27K) temperatures in short tape samples. Detailed measurements with high applied
magnetic fields are reported. Several long tapes up to 10 m in length have also been fabricated and cowound into small superconducting
pancake coils by the “wind-and react” approach. Transport measurements at 77 and 4.2K for these coils are also reported. 相似文献
5.
6.
Salazar A. Pastor J.Y. LLorca J. 《Applied Superconductivity, IEEE Transactions on》2004,14(3):1941-1947
The mechanical properties and the critical current were studied in three commercial multifilamentary Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10+x//Ag tapes subjected to monotonic and fatigue tension at 77 K in the longitudinal direction. It was found that transport properties were not compromised under monotonic tension if the maximum tensile stress remained below the conventional 0.2% yield strength. This magnitude was reduced by 10% to 20% in the case of fatigue loading, and the service life of the tape was dictated by the mechanical fatigue life. 相似文献
7.
《Applied Superconductivity》1997,5(1-6):157-162
Current-voltage characteristics of Ag-sheathed Bi-2223 monocore tapes have been measured at 77 K in low d.c. magnetic fields. Results have been obtained with the c-axis of the sample both parallel and perpendicular to the applied field, together with the force-free orientation. The current–voltage characteristics have been analysed in terms of their n-value (V∝In), which characterizes the sharpness of the resistive transition and the second differential (d2V/dI2), which shows the distribution in local critical current density values. The second differential has been fitted and analysed using the phenomenological Weibull distribution function, which is based on a weak-link model. The four parameters of this function have been used to investigate the microstructural nature of the sample, in particular, the factors influencing the critical current density and the transport current pathways. The results are consistent with the view that at low fields the critical current density is limited by weak-link grain boundaries and at high fields by intra-granular flux pinning. 相似文献
8.
A. N. Iyer U. Balachandran L. R. Motowidlo J. G. Hoehn P. Haldar 《Journal of Electronic Materials》1994,23(11):1087-1091
Pb0.4Bi1.8Sr2Ca2.2Cu3Ox (Bi-2223) precursor powder was prepared by a solid-state reaction of carbonates and oxides of lead, bismuth, strontium, calcium,
and copper, and the powder was then used to fabricate silver-clad tapes by the powder-in-tube technique. Transport critical
current density (Jc) values>4×104 A/cm2 at 77K and 2×105 A/cm2 at 4.2 and 27K have been achieved in short tape samples. Long lengths of tape were tested by winding them into pancake coils.
Recently, we fabricated a test magnet by stacking ten pancake coils, each containing three 16m lengths of rolled tape, and
tested it at 4.2, 27 and 77K. A maximum generated field of 2.6 T was measured in zero applied field at 4.2K and the test magnet
generated significant self-field in background fields up to 20 T. The results are discussed in this paper. 相似文献
9.
S. Yu. Paranchych L. D. Paranchych V. N. Makogonenko Yu. V. Tanasyuk M. D. Andriichuk V. R. Romanyuk 《Semiconductors》2005,39(6):712-715
CdTe:(V, Ge) single crystals are grown using the Bridgman-Stockbarger method. The impurity concentrations in the melt are NV = 1 × 1019 cm?3 and NGe = 5 × 1018 and 1 × 1019 cm?3. Electrical and galvanomagnetic characteristics are studied in the temperature range 300–400 K. It is found that the equilibrium characteristics are governed by deep levels (ΔE = 0.75–0.95 eV) located close to the midgap. Low-temperature optical absorption spectra indicate that the impurity levels of V and Ge ions in the low-energy region are in different charge states. In addition, the samples are annealed in Cd vapor and then rapidly cooled. This annealing causes the decomposition of various complexes formed during the crystal growth and an increase in both electrical conductivity and charge carrier concentration. 相似文献
10.
Yuan -Liang Wang W. Bian Y. Zhu Y. Fukumoto H. J. Wiesmann M. Suenaga T. R. Thurston K. Merken S. Hong 《Journal of Electronic Materials》1995,24(12):1817-1820
Bi-2223 tapes were manufactured from a fine “two-powder” product produced by using an aerosol spray pyrolysis technique. Critical
current density of 22000 A/ cm2 at 77K and 0 T was achieved. Nondestructive transmission x-ray diffraction study indicated
good alignment of the superconducting grains. The texturing process of the superconducting phase was found to be nearly complete
after the first 24 h of heat treatment for the samples studied. Pressing was found to play little role in the texturing process.
The texturing can be enhanced by Ag-doping. Jc, however, was not found to be improved significantly, presumably due to the reduced effective cross-sectional area. A new
phase, Bi-4435, was identified which may play a significant role in the formation of 2223.
On leave from Northeastern University, Shenyang, P.R.C.
On leave from Kobe Steel Ltd., Kobe, Japan 相似文献
11.
《Applied Superconductivity》1996,4(7-8):291-297
Ag-clad Tl0.75Bi0.25Sr1.6Ba0.4Ca2Cu3Ox tapes were fabricated by a powder-in-tube technique. The starting powders consisted of Bi2Sr2CaCu2Ox plus simple oxides. The tapes were heated in flowing O2 at 835–865 °C for 7.5–10 h. Room-temperature pressing at 1.0–1.5 GPa produced tapes with denser, more phase-pure cores, and transport critical current density Jc at 77 K in self-field that was increased by a factor of ≈2. The maximum Jc value of 6 × 103 A/cm2 was obtained with heating at 840 − 850 °C for ≈ 10 h, with three intermediate pressing steps. The cores of the best tapes were still rather porous and contained significant concentrations of nonsuperconducting phases. 相似文献
12.
From phase diagram, this paper discusses the selecting rules of PZT for a pyroelectric material and the doping Bi material that Zr/Ti is 94/6 is particularly reported. The experiment process and the points for attention are given. The two kinds of the infrared detector using this material, the one being with-substrate and the other without-substrate, are produced and discussed. The characters of the material and the detectors are given in the paper. 相似文献
13.
Mail Tagiyev Farkhad Samedov Sohrap Samedov 《Journal of Infrared, Millimeter and Terahertz Waves》1997,18(9):1813-1820
Thin films of Bi85Sb15 solid solution wich can be used in thermoelectric devices for cooling and stabilizing the temperature of Gann and Impatt diodes have been obtained by extrusion method. They have surface roughness in the range 10–80µm, dielectric lossestan δ ~ 10?3 at 10 GHz, thermal conductivityβ ~ 4x102 W / (M · K). Anisotropy of electroconductivityσ, thermoelectric powerα and Hall coefficientsR H of lead doped extruded Bi85Sb15 samples has been investigated in the temperature range between 77 K and 300 K and in the presence of magnetic fieldH up to ~ 74×104 A/m. It is shown that the value and sign of the anisotropy coefficient essentially depend on heat treatment and impurity concentration. Experimental results are explained taking into account a crystal structure of Bi85Sb15, formation of texture and generation of deformation defects. 相似文献
14.
Crystalline bulk compositions of Bi2 (Se1−xTex)3 system with ( x=0.0–1.00) were prepared using the conventional melting method. The structural properties of bulk samples were studied with the aid of XRD and SEM analysis. Compositional element distribution and elemental ratios were estimated with EDX spectroscopy that attached with SEM. XRD patterns show that the prepared compounds are crystalline materials with single phases of Bi2Se3 and Bi2Te3 and/or a ternary phase. The grain size calculations were performed using the well-known Scherrer equation. The thermal studies analysis was carried out by using DSC. DSC studies revealed that the prepared samples are stable and none decomposable over the temperature range. Physicochemical properties such as compactness, molar volume and the free volume percentage were calculated for the concerned alloys based on the experimentally calculated densities of each compound. The measured parameters showed a strong dependence on the Te content. 相似文献
15.
K. C. Goretta C.-T. Wu M. T. Lanagan R. B. Poeppel J. Schwartz S. Wu 《Journal of Electronic Materials》1993,22(10):1289-1294
Silver-clad tapes with transport Jc values to 105 A/cm2 at T-4.2K were produced by a powder-in-tube process. Moderate reductions per pass and proper tape thicknesses were essential
for producing good conductors. Partial-melt sintering, followed by a solid-state heat treatment, produced microstructures
consisting of large, well-aligned 2212 grains and alkaline-earth cuprate phases. The deleterious effects of these second phases
were minimized by proper heat treatments, but further reductions in the sizes and concentrations of these phases are needed
to improve Jc values substantially. Lithium additions raised Tc, improved flux pinning, and lowered melting points. They offer hope that the presence of alkaline-earth cuprates can be limited
through use of low-temperature heat treatments. 相似文献
16.
17.
S. X. Dou M. Ionescu W. G. Wang H. K. Liu E. Babic I. Kusevic 《Journal of Electronic Materials》1995,24(12):1801-1804
A “sandwich rolling” process was developed to prevent the formation of sausaging and cracks in the longitudinal direction.
The stress-strain state of the tape in “sandwich” rolling is the same as that of uniaxial pressed tape because the deformation
of steel sheets is negligible in comparison to that of Ag-clad tape. Critical current densities of 3.2 × 104 A/cm2 at 77K and 2.7 × 105 A/cm2 at 4.2K and zero field Ag-sheathed Bi-based 2212 tapes have been achieved using a melt and atmosphere-controlled process.
The comparison of pinning potential U0(B) < U(T-0, B) for Bi-2212 tape and Bi-2223 tapes consisting of a different fraction of 2212 phase as well as Bi-2212 and
Bi-2223 thin films shows that for the same fields, the Uo for good quality 2223 tapes is at least 1.3 times that for the best 2212 tape and epitaxial thin films after taking into
account the difference of the Tc between 2223 tape and 2212 tape, indicating that in BSCCO compounds, in addition to anisotropy, the specific pinning centers
such as dislocations, introduced during processing, affect the flux motion at lower B. 相似文献
18.
Van Vo N. Shi Xue Dou Hua Kun Liu 《Applied Superconductivity, IEEE Transactions on》1996,6(2):102-105
High temperature superconducting (HTSC) multifilamentary (MT) Bi(Pb)-2223/Ag tapes with reproducible critical current density of between 15000 and 20000 A/cm2 at 77 K in self field have been achieved using the standard flat-rolling method as the intermediate deformation between sintering periods. Long lengths of Bi(Pb)-2223/Ag MT tapes up to 43 m prepared by the conventional method of powder-in-tube (PIT) have been successfully produced on a laboratory scale. Several coils have been fabricated from sections of the long length tape, using the co-wound wind-and-react (W&R) procedure for the pancake-shaped and the singly-wound W&R as well as R&W procedure for the solenoidal coils. A novel W&R solenoidal coil (reaching ~973 ampere-turns) wound on an alumina ceramic tube generates a DC field of ~19 mT at 77 K and has been fabricated together with five pancake-shaped coils, each generating an average of ~5 mT at 77 K. These are destined for magnet construction with a possible combined calculated field of ~0.04 T at 77 K (with liquid nitrogen as a coolant) 相似文献
19.
20.
采用固相反应法制备了Bi 3+ 、Eu3+ 、Tb3+ 掺杂的Lu3TaO7。测量了样品的X射线衍射谱、激发和发射光谱及荧光衰减曲线。三种离子掺杂的Lu3TaO7均呈现出强的荧光发射,其中Bi3+具有峰位在431 nm处的一强发射宽带,衰减寿命为16.8 μs,Eu 3+ 、Tb 3+ 则表现出稀土离子的特征锐发射峰,衰减寿命分别为1.26 ms和1.20 ms。因此,它们均是具有潜在应用前景的重闪烁体材料。 相似文献