Superconductors, Metallurgy of Ductile Alloys

Lee, Peter J.

doi:10.1002/047134608x.w1302

Cited by 9 publications

(15 citation statements)

References 47 publications

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“…Further increasing the milling time up to 40 h, when the powder consists mostly of the β-Nb(Ti) alloy, the T c values remain unchanged at 8. These initial properties for our powder-processed Nb-Ti material look promising, but we note that the T c and B c2 values after 40 h milling (T c = 8.1 K, B c2 (at 4.2 K) = 9.8 T) are lower than those reported for fully processed NbTi wires (T c = 9.2 K, B c2 (at 4.2 K) = 11 T) [1]. Contamination of the powder with oxygen or transition metals from the milling media and structural disorder are possible sources of this reduction, and would have to be explored in future work.…”

Section: Powder Processingmentioning

confidence: 48%

“…The Nb-Ti alloy system has been the dominant commercial superconductor used for magnet windings since the 1960s because of its strength and ductility, high critical current density, and relatively low cost [1]. The main applications of NbTi based magnets are in Magnetic Resonance Imaging, Nuclear Magnetic Resonance, Superconducting Magnetic Energy Storage and particle accelerators [1][2][3]. In all of these applications, a carefully tailored microstructure is needed in the NbTi alloy filaments in order to optimise the critical current carrying capacity in high magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

“…In all of these applications, a carefully tailored microstructure is needed in the NbTi alloy filaments in order to optimise the critical current carrying capacity in high magnetic fields. High purity, a fine grain structure and reasonable ductility are essential requirements in the starting alloy [1,4]. In addition, as in all type II superconductors, achieving high critical current densities in magnetic fields is only possible if flux line motion is inhibited.…”

Section: Introductionmentioning

confidence: 99%

“…In almost all commercial NbTi wires this has been achieved using a starting composition of Nb-47 wt%Ti which has a high ductility and, after thermomechanical processing, results in an optimised combination of high B c2 and T c values, and the correct volume of nanoscale α-Ti to maximise J c values. This thermomechanical processing route is rather complex, involving fabricating large NbTi billets by vacuum arc melting of pure Nb and Ti electrodes, then drawing and annealing under carefully controlled conditions [1]. During the drawing process a high cold work strain is induced, followed by three or more heat treatments in the α + β phase range, each separated by additional cold work [8,9].…”

Section: Introductionmentioning

confidence: 99%

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A new approach to fabricate superconducting NbTi alloys

Mousavi

Hong

Morrison

et al. 2017

Supercond. Sci. Technol.

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Superconducting NbTi alloys have been successfully fabricated by a simple powder processing route involving ball-milling, pressing and annealing. The microstructure and superconducting properties of the NbTi alloys after each processing step have been characterized and compared to the microstructure and performance of NbTi wire manufactured by a conventional thermomechanical process. At the early stages of milling, a lamellar structure of pure Nb and Ti regions is formed, which is gradually refined by further milling leading to the introduction of a high density of microstructural defects. After 20 hrs milling, diffusion of Ti into the Nb generates a matrix of -Nb-50wt%Ti alloy, with a small grain size (50 nm) and high strain (1.8%), containing an even distribution of thin Ti flakes (10-40 nm). In some regions, these Ti flakes contain a supersaturation of Nb as a result of the energetic ball-milling process. The Tc (8.1 K) and Bc2 (9.8 T at 4.2 K) values of this as-milled material are slightly lower than those reported for Nb-47wt%Ti due to the impurity content and lattice disorder. Sintering at 400 ᵒC leads to well consolidated, high density bulk samples, but annealing at temperatures above 600 ᵒC decreases Jc values due to excessive grain growth and strain release. Annealing at lower temperatures results in higher Jc values, a shift of the pinning force density peak towards higher fields and the presence of thermodynamically stable α-Ti precipitates which are effective pinning sites leading to critical current density values comparable with those of commercial NbTi wires.

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Section: Powder Processingmentioning

confidence: 48%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A new approach to fabricate superconducting NbTi alloys

Mousavi

Hong

Morrison

et al. 2017

Supercond. Sci. Technol.

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“…NbTi alloy based thin films with varying composition can be deposited by using a broad variety of techniques that include melting of alloy [23], electrochemical synthesis [24], combustion synthesis [25], ionic plasma cluster method [26] and ball milling with pressing and annealing [27]. Melting of alloy is the conventional method for NbTi fabrication, where an electrode of NbTi is produced from pure Nb and pure Ti and which is melted by an electron beam.…”

Section: Introductionmentioning

confidence: 99%

Diffusion mediated growth of superconducting Nb-Ti composite films by high temperature annealing

Sawle,

Awana,

Sahoo

2023

Phys. Scr.

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The fabrication of superconducting Nb-Ti alloy by high temperature annealing of Nb/Ti bilayer thin films is reported here. During the annealing process, Nb and Ti diffuse into each other and Nb-Ti composite film formation occurs at the interface of the bilayer. Two types of substrates, namely, SiO2/Si and Si3N4/Si are used to grow the bilayers of Nb/Ti by using dc magnetron sputtering. Annealing at temperature about 820C leads the substrates to take part into the diffusion process. The alloying of Nb-Ti and the effect of substrates on the structural properties are studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Ti-rich Nb-Ti phases are present in the XRD while interface studies through XPS confirms the interdiffusion of the two elements Nb and Ti along with the presence of the decomposed elements from the substrates. Appearance of nitride phases in case of Si3N4/Si substrate confirms the substrate’s involvement in the diffusion process. Further low temperature transport measurements are carried out to study the superconducting properties of the Nb-Ti composite films grown on both oxide (SiO2/Si) and nitride (Si3N4/Si) substrates. Nb-Ti composite films offer higher transition temperature (TC) compared to that of pure Nb with similar thickness used in Nb/Ti bilayer films. Higher normal state resistance (RN) with wider transition width for Nb-Ti on nitride substrate in comparison with the oxide substrate indicates a possible role of N atoms in tuning the disorder and hence controlling the transport properties. Finally, the presented method can be used to fabricate superconducting stoichiometric NbTi and NbTiN thin films for future phase slip and superconducting single photon detector-based applications.

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