Nb3Sn Superconducting Wire Grain Refinement
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Solution Overview
Problem
Current superconducting wires based on niobium tin (Nb3Sn) face challenges in achieving high-field critical current density and flux pinning force, with grain sizes typically exceeding 100 nm, limiting their application in high-field magnetic applications.
Innovation Solution
The development of superconducting wires with a metallic matrix and embedded subelements comprising a non-superconducting core, a superconducting Nb3Sn layer stabilized by metal oxide particulates, and a barrier layer, where the Nb3Sn layer is refined through internal oxidation using metal oxide powders to achieve grain sizes between 5 nm and 90 nm, enhancing critical current density and flux pinning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional Nb3Sn superconducting wires are used, then the manufacturing process is relatively simple, but the grain size exceeds 100 nm which limits the high-field critical current density and flux pinning force
Solution Approach 1:
The patent implements a nested multi-layer structure where metal oxide particulates are embedded within the Nb3Sn superconducting layer, which itself is surrounded by a barrier layer, all contained within subelements that are embedded in a metallic matrix. This nesting approach allows the metal oxide particulates to act as grain boundary pinning centers within the Nb3Sn grains, refining the grain size to below 100 nm while maintaining structural integrity and enabling complex functionality through hierarchical organization
Solution Approach 2:
The patent creates a composite superconducting wire structure combining multiple materials: Nb3Sn superconducting phase, metal oxide particulates (such as ZrO2, Al2O3, or TiO2), barrier layers (such as Nb or NbN), and a metallic matrix (such as Cu or Cu alloy). This composite approach allows each material to contribute specific properties - Nb3Sn provides superconductivity, metal oxide particulates provide grain refinement and flux pinning, barrier layers prevent interdiffusion, and the matrix provides mechanical support and stability, collectively achieving fine grain size and high field performance
2Reliability
If grain size is reduced to improve critical current density, then the high-field performance improves, but the manufacturing complexity increases due to the need for internal oxidation processes
Solution Approach 1:
The patent incorporates metal oxide particulates into the wire structure during the manufacturing process before the final heat treatment. These particulates are pre-positioned within the subelements, surrounded by appropriate layers, and configured to release oxygen during the subsequent heat treatment process. This preliminary arrangement ensures that when heat treatment occurs, the oxygen is already in the correct location to oxidize Nb atoms and form fine-grained Nb3Sn, eliminating the need for complex external oxidation control mechanisms
Solution Approach 2:
The patent utilizes the oxidation process, which can be harmful if uncontrolled, as a beneficial mechanism for grain refinement. By incorporating metal oxide particulates that serve as controlled oxygen sources, the oxidation of Nb atoms is directed and localized, converting what could be a damaging uncontrolled oxidation into a controlled grain-refining mechanism. The metal oxide particulates act as oxygen reservoirs that release oxygen in a controlled manner during heat treatment, ensuring fine grain formation without the need for complex external oxygen management
3Reliability
If metal oxide particulates are added to refine grains, then the flux pinning force improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent divides the wire into discrete subelements, each containing a specific number and distribution of metal oxide particulates. This segmentation allows for standardized manufacturing of individual subelements with controlled particulate content, which can then be assembled into the final wire structure. Each subelement acts as an independent unit with its own metal oxide particulates embedded in the Nb3Sn matrix, making the incorporation of particulates a modular process rather than a bulk addition, thereby simplifying quality control and manufacturing consistency
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 refined grain size and internal oxidation method significantly improve the high-field critical current density and flux pinning force, shifting the peak of the flux pinning force vs. field curve, thereby expanding the application range of Nb3Sn conductors to higher magnetic fields.
Implementation Method 1
the Nb3Sn layer is refined through internal oxidation using metal oxide powders to achieve grain sizes between 5 nm and 90 nm
Implementation Method 2
The Nb3Sn grains can have an average grain size of from 5 nm to 90 nm (for example from 15 nm to 30 nm)
Implementation Method 3
Superconductivity is a phenomenon occurring in certain materials below certain temperatures, characterized by zero electrical resistance and expulsion of magnetic fields
Implementation Method 4
The superconducting layer can comprise a plurality of Nb3Sn grains stabilized by metal oxide particulates disposed therein
Data Source
AI summary
Disclosed herein are superconducting wires. The superconducting wires can comprise a metallic matrix and at least one continuous subelement embedded in the matrix. Each subelement can comprise a non-superconducting core, a superconducting layer coaxially disposed around the non-superconducting core, and a barrier layer coaxially disposed around the superconducting layer. The superconducting layer can comprise a plurality of Nb3Sn grains stabilized by metal oxide particulates disposed therein. The Nb3Sn grains can have an average grain size of from 5 nm to 90 nm (for example, from 15 nm to 30 nm). The superconducting wire can have a high-field critical current density (Jc) of at least 5,000 A/mm2 at a temperature of 4.2 K in a magnetic field of 12 T. Also described are superconducting wire precursors that can be heat treated to prepare superconducting wires, as well as methods of making superconducting wires.