Low Resistivity Joints for Superconducting Magnesium Diboride Wires
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Solution Overview
Problem
Existing methods for forming magnesium diboride wires into longer lengths for applications like MRI are hindered by high resistance at connection joints, which prevents the achievement of high operating fields and critical current values, and the introduction of non-superconducting impurities during doping processes.
Innovation Solution
A method involving the use of doped magnesium diboride powders with a second phase coating, such as silicon carbide, to enhance critical current density and upper critical fields, combined with a process for forming persistent joints with low resistivity by preparing wire ends in a mateable configuration and joining them with a conductive cladding and wrapping material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If magnesium diboride wires are joined together to form longer wires for MRI applications, then the wire length is increased, but the resistance at connection joints increases
Solution Approach 1:
The wire ends are prepared in advance by cleaning and oxidizing the surface to create a mateable configuration that ensures low-resistance connection when joined. This preliminary surface treatment prevents high resistance at the joint interface.
Solution Approach 2:
A copper-based intermediate material is introduced at the joint area between the magnesium diboride wire ends. This intermediate material facilitates electrical and mechanical coupling while maintaining low resistance, acting as a mediator that enables persistent joint formation.
2Ease of manufacture
If doping and additive materials are introduced to magnesium diboride powder to improve mechanical properties and drawability, then the wire formability is improved, but non-superconducting impurities are introduced
Solution Approach 1:
Additive materials are introduced locally at specific stages during wire fabrication rather than uniformly throughout the magnesium diboride powder. This localized addition improves mechanical properties and drawability while minimizing the overall amount of non-superconducting impurities in the final product.
Solution Approach 2:
The concentration and type of additive materials are carefully controlled and adjusted during the fabrication process. By optimizing the parameters of additive introduction, the patent achieves improved wire formability while maintaining the superconducting properties of magnesium diboride.
3Power
If magnesium diboride powder is processed into wires for high current carrying applications, then the critical current density is improved, but the upper critical fields and irreversibility fields are reduced
Solution Approach 1:
The patent creates a composite structure where magnesium diboride superconducting filaments are embedded in a copper-based matrix. This composite configuration allows the magnesium diboride to maintain its high critical current density while the copper matrix provides thermal and electrical stability that preserves upper critical fields and irreversibility fields.
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
Enables the formation of longer superconducting wires with minimal resistance at joints, achieving high current carrying capabilities and mechanical strength suitable for MRI applications by ensuring uniform dispersion of additives and preventing non-superconducting impurities.
Implementation Method 1
Typically, magnesium diboride powders are formed by the reaction of elemental magnesium and boron.
Implementation Method 2
affecting the joint area such that the end of the first wire and the end of the second wire are electrically and mechanically coupled through the joint material
Data Source
AI summary
Method for joining wires using low resistivity joints is provided. More specifically, methods of joining one or more wires having superconductive filaments, such as magnesium diboride filaments, are provided. The wires are joined by a low resistivity joint to form wires of a desired length for applications, such in medical imaging applications.