Multifilament Nb3Sn Wire With Graded Cu/Nb Ratio for Small Subelements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing Nb3Sn superconducting wire fail to achieve high critical current density (Jc) at small subelement sizes, particularly in the range of 20-60 microns, while maintaining electrical stability and minimizing magnetization and ac losses.
Innovation Solution
A method involving graded local area ratios (LAR) within the subelement, distributed diffusion barriers, and controlled heat treatment processes to optimize the ratio of Nb, Sn, and Cu components, along with optional doping with Ta or Ti, to enhance Sn diffusion and reaction dynamics, resulting in a multifilament Nb3Sn superconducting wire with improved Jc.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fraction of Nb and Sn in the wire cross section is increased to achieve higher critical current density, then the superconducting performance is improved, but the wire becomes more difficult to process and fabricate due to reduced ductility and increased hardness
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of Cu and Nb phases within the wire structure. Specifically, Cu-rich regions are positioned in areas requiring ductility and processing ease, while Nb-rich regions are concentrated in areas where superconducting performance is critical. This spatial differentiation allows different regions of the wire to optimize for their specific functions, resolving the contradiction between high Jc requirements and manufacturability.
Solution Approach 2:
The patent utilizes composite material principles by creating a multi-phase structure combining Cu, Nb, and Nb3Sn in specific configurations. The composite architecture includes Cu matrices providing ductility and processing ease, Nb filaments providing superconducting precursor material, and controlled Nb3Sn formation zones. This composite approach allows the wire to simultaneously achieve high critical current density through optimized superconducting phase distribution while maintaining manufacturability through the ductile Cu matrix structure.
2Reliability
If the amount of Cu in the wire is reduced to increase the fraction of Nb and Sn for higher Jc, then the superconducting critical current density is improved, but the wire becomes harder to process and the reaction temperature control becomes more difficult
Solution Approach 1:
The patent implements local quality by creating Cu-rich interfilamentary regions and Cu-poor core regions within the wire structure. The Cu-rich regions provide ductility and ease of drawing processing, while the Cu-poor regions maximize Nb and Sn content for high non-copper critical current density. This localized compositional variation allows the wire to achieve both high performance and manufacturability simultaneously.
Solution Approach 2:
The patent applies parameter changes by systematically varying the Cu content and distribution throughout the wire cross-section and along the wire length. By controlling Cu concentration parameters in different zones and adjusting the Cu:Nb:Sn ratio parameters, the patent optimizes both the processing characteristics (ductility, drawability) and the superconducting performance (non-copper Jc). This parametric optimization resolves the contradiction between reduced Cu content for high Jc and sufficient Cu for processing ease.
3Reliability
If the subelement size is reduced to increase the number of filaments and improve current distribution, then the electrical stability is improved, but the manufacturing precision and heat treatment uniformity become more difficult to maintain
Solution Approach 1:
The patent applies segmentation by dividing the wire into multiple small subelements, each containing a controlled number of filaments. This segmentation approach improves electrical stability by creating multiple independent current-carrying paths that are less susceptible to localized defects. The segmented structure also facilitates more uniform heat treatment by reducing the thermal diffusion distance. By carefully controlling the number and size of segmented subelements, the patent achieves both improved electrical stability and maintained manufacturing precision.
Solution Approach 2:
The patent resolves the precision challenge by transitioning from controlling a single large subelement dimension to controlling multiple smaller subelement dimensions. The cumulative effect of many small, precisely-controlled subelements achieves the desired fine filament structure while being more manufacturable. This dimensional approach allows standard manufacturing tolerances to be applied to multiple small components rather than requiring extreme precision on a single large component.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves critical current densities of at least 2000 A/mm² at 4.2 K and 12 T, with non-copper critical current densities up to 3000 A/mm² at 4.2 K and 1700 A/mm² at 4.2 K, and 15 Tesla, and 1700 A/mm² at 4.2 K, 1700 A/mm² at 4.2 K, and 1700 A/mm² at 4.2 K, and 4.2 K, 15 Tesla, while maintaining subelement sizes of 20-60 microns.
Implementation Method 1
Cu between the Nb filaments serves as a path for diffusion of Sn, to allow the Sn source to be dispersed throughout the subelements and to all of the Nb filaments
Implementation Method 2
the capability to provide more Nb 3 Sn in the final wires' cross section
Implementation Method 3
converting the Nb and Sn to Nb 3 Sn
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method for producing a multifilament NbsSn superconducting wire comprising: - packing a plurality of Cu encased Nb rods within a matrix which is surrounded by an intervening Nb diffusion barrier and a further matrix on the other side of the barrier remote from the rods, to thereby form a packed subelement for the superconducting wire; wherein through the subelement, the Nb in Cu local area ratio (LAR) is adjusted or graded to provide a higher LAR in or near the center and a lower LAR near the periphery, near to or proximate to the barrier, with LAR=Cu area% / Nb area %, - providing a source of Sn within the subelement; - assembling the subelements in a further matrix and reducing the assemblage to wire form, and - heat treating the final size wire from step d) to form the NbsSn superconducting phase. With the inventive method, the current at small subelement dimensions may be improved.