Microstructural and Magnetic Characterization of ${\hbox{CuNb}}/{\hbox{Nb}}_{3}{\hbox{Sn}}$ Wires With Different Architectures (original) (raw)
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EFFECT OF ANNEALING ON Cu-Nb-Sn SUPERCONDUCTING WIRE
The most common application of superconductors is done in the form of superconducting wire. Among the existing types of superconductors, Cu-Nb-Sn superconductors are the most widely used as a wire, producing a high magnetic field. But the critical temperature (TC) values of its superconductors are low enough so that the resulting magnetic field and its application fields are limited. In this study we investigated the effect of annealing treatment on the Cu-Nb-Sn superconducting wire. Note that the process of annealing on superconducting wire can increase the value of the critical temperature of 8K to 16K. The increase is predicted because of the forming of Nb3Sn compounds, and the Nb3Sn compound becomes more stable. Annealing processes were performed at temperatures ranging from 600°C to 900°C as well as various annealing time from 32 hours to 120 hours. The superconductivity of the samples were analyzed using resistivity measurement by cryogenic system under low temperature condition. The annealing can be performed optimally at the temperature of 600°C for 72 hours. However, the purity of the conductivity properties obtained at the optimal annealing temperature at 450˚C for 72 hours.
Jurnal Sains Materi Indonesia EFFECT OF ANNEALING ON Cu-Nb-Sn SUPERCONDUCTING WIRE
2015
EFFECT OF ANNEALING ON Cu-Nb-Sn SUPERCONDUCTING WIRE. The most common application of superconductors is done in the form of superconducting wire. Among the existing types of superconductors, Cu-Nb-Sn superconductors are the most widely used as a wire, producing a high magnetic field. But the critical temperature (T C) values of its superconductors are low enough so that the resulting magnetic field and its application fields are limited. In this study we investigated the effect of annealing treatment on the Cu-Nb-Sn superconducting wire. Note that the process of annealing on superconducting wire can increase the value of the critical temperature of 8K to 16K. The increase is predicted because of the forming of Nb 3 Sn compounds, and the Nb 3 Sn compound becomes more stable. Annealing processes were performed at temperatures ranging from 873K to 1173K as well as various annealing time from 32 hours to 120 hours. The superconductivity of the samples were analyzed using resistivity mea...
J Mater Sci, 1987
Investigations were made of the superconducting transition temperature, To, the upper critical flux density, Be2, and the critical current density, Jc, of Nb3Sn layers in filamentary wire in a bronze matrix. The lattice parameter, a0, and Tc of Nb3Sn layers in 259-filament wire were determined after removal of the bronze matrix. The microstructure and layer thickness were studied using scanning electron microscopy. The diffusion formation of Nb3Sn phase at 1023 K was studied until the complete reaction of the niobium filaments. It was found that the Nb3Sn layer begins to form in the manufacturing process during the intermediate annealing at 793 K, and that there is a considerable degradation of critical parameters due to the nonstoichiometry of the Nb3Sn phase in layers thinner than 1 #m.
Microstructure development in Nb3Sn(Ti) internal tin superconducting wire
Journal of Materials Science, 2008
The authors have studied the phase formation sequences in a Nb 3 Sn 'internal tin' process superconductor. Heat treatments were performed to convert the starting materials of tin, Ti-Sn, copper and niobium, to bronze and Nb 3 Sn. Specimens were quenched at different points of the heat treatment, followed by metallography to identify the phases present and X-ray microtomography (XMT) to investigate the void volume and distribution. An unexpected observation of the microstructure development was the uphill diffusion of tin during the Cu-Sn reactive diffusion. Some defects likely to affect the superconducting performance of the wires were observed. Microscopy revealed the presence of a Ti-Sn intermetallic compound displacing the niobium filaments, and XMT revealed the formation of long pores in the longitudinal direction. Two types of pore formation mechanism, in addition to Kirkendall pores, are proposed. The phase and microstructure development suggests that low-temperature heat treatment (below 415°C) will have significant influence on optimising the final superconducting properties.
Cryogenics, 1985
Superconducting critical-current densities Jc in fields up to 24 T and at 4.2 and 1.8 K were measured for a number of commercial Nb3Sn wires which were alloyed with Ti. The best values of Jc (for the area excluding the stabilizing copper) at 20 T and at 4.2 and 1.8 K were 78 and 156 A mm-2, respectively. These values are approximately 10 and 4 times greater than values for the best 'pure' Nb3Sn wire for these measurement parameters. In order to achieve these high current densities at H>20 T, it was shown that nonuniformity of the filaments had to be minimized, It was also shown that the grain size of Nb3Sn is not very important in determining Jc at these high magnetic fields, and that achieving high values of critical magnetic field Hc2 is more important than small grain size.
The type-II superconducting properties of heavily deformed Cu-Ag-Nb wires, containing only 4 wt% (4.18 vol.%) of elongated Nb filaments as a separate superconducting phase, were investigated as a function of microstructure, temperature, total wire strain, and external magnetic fields. The microstructure of the wires was examined using optical and electron microscopy. The experimental observation of the proximity effect, i.e. of the penetration of the superconducting state into the normal resistive Cu-Ag matrix leading to bulk-superconductivity, is explained in terms of the experimentally determined topology of the microstructure in conjunction with Ginzburg-Landau theory. The pronounced drop of the critical temperature and of the critical magnetic field with increasing wire strain is explained in terms of the reduced thickness of the ductile Nb filaments which is at large strains of the order of the Ginzburg-Landau correlation length in Nb.
Cryogenics, 1989
Binary and Ti + Mg alloyed NB3Sn wires both containing 19 x 132 and 55 x 588 filaments with diameters ranging between 1 and 5/~m have been produced by the internal Sn diffusion process, starting with cold hydrostatic extrusion. These wires exhibit a regular distribution of Sn cores and Nb filaments through the whole cross-section area. A heat treatment scheme including short preheating and a final reaction at 780°C yields Jc (non-Cu) values of 1.5 x 105 A cm-2 at 10 T for binary Nb3Sn wires. Ti + Mg alloyed Nb3Sn wires reacted according to the same scheme show higher Jc values above 12 T, i.e. 6.1 x 104 A cm-2 at 14 T, 1.8 ix 104 A cm-2 at 18 T. The present Paper includes measurements of Jc at applied fields up to 20 T and Jc as a function of the applied uniaxial strain, ~, at 13.5 T as well as T c after different heat treatments. The analysis was completed by the SEM determination of the A15 grain size with different additives and the measurement of the Sn concentration profiles by means of Auger spectroscopy for filaments located at different matrix regions. The absolute Sn concentration values were determined by EDX. It is found that the simultaneous addition of Ti and Mg to the Sn facilitates Nb3Sn grain growth and leads to finer grains.
High-resolution electron backscatter diffraction (EBSD) technique and DC magnetization were used to characterize a Cu-Nb reinforced bronze route Nb3Sn superconducting multifilamentary wire. The results of DC-magnetization show an extended regime of magnetic reversibility in the operational magnetic field-temperature phase diagram. This observation is discussed in terms of microstructure characteristics of the A15 phase such as grain size, grain boundary misorientation angle distribution, tin gradient across the filaments and residual strain, in connection to the literature.
Manufacture of Nb3Al superconducting wires by the rapid heating and quenching technique
Physica C: Superconductivity, 2003
As a first approach, a wire with a single Nb 3 Al filament has been manufactured to study the rapid heating and quenching parameters. A reel-to-reel continuous rapid quenching apparatus has been designed and fabricated which will be able to produce some hundred meters of wire. The heating temperature is monitored by an infra-red two colours detector. Structural characterization of Nb 3 Al wires has been investigated by means of X-ray diffraction. Due to the absence of stabilizing Cu, superconducting transport properties were estimated by Bean formula as a function of a background magnetic field up to 10 T, while hysteresis losses were measured by vibrating sample magnetometer facility.