MgB2 Monofilament MRI Magnet Joints via Ceramic Paste Sealing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing MRI magnets made from multifilament niobium-titanium (NbTi) wires face issues with flux jumping, leading to high costs and operational challenges, and the splicing of reacted monofilament wires is difficult due to their hard ceramic nature, making them unreliable for commercial manufacturing.
Innovation Solution
The development of a persistent-mode MRI magnet using reacted, monofilamentary MgB2 wires and joints, where the wires are sheared at an acute angle and inserted into a stainless steel billet with a copper plug, allowing for a high-pressure ceramic paste sealing and heat treatment at 700°C, creating a reliable and efficient superconducting joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multifilament NbTi wires are used to prevent flux jumping, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent changes the material parameter from NbTi to MgB2, which has a higher critical temperature and different flux pinning characteristics. This allows the use of monofilament wires instead of multifilament wires while maintaining reliability and preventing flux jumping, thereby reducing device complexity
Solution Approach 2:
The patent uses a simpler monofilament wire structure that is easier and cheaper to manufacture compared to complex multifilament wires. The simplified wire structure reduces manufacturing cost while still achieving the required operational stability through the inherent properties of MgB2 material
2Ease of manufacture
If reacted monofilament wires are spliced, then manufacturing simplicity is improved, but reliability deteriorates due to difficulty in joining hard ceramic wires
Solution Approach 1:
The patent performs preliminary action by applying high pressure and heat treatment at 700°C before final assembly. This pre-treatment softens the ceramic paste, making it pliable for sealing and joining operations, while the subsequent cooling and pressure application creates a strong, reliable joint in the final assembled state
Solution Approach 2:
The patent exploits phase transitions of the ceramic paste material, which transitions from a hard ceramic state to a softer, more workable state under high temperature and pressure conditions during heat treatment. This phase transition enables reliable joining and sealing operations, and the material then transitions back to a strong ceramic state upon cooling, creating durable joints
3Strength
If high heat treatment temperatures are applied to form reacted joints, then joint strength is improved, but manufacturing complexity increases as all magnet materials must withstand high temperatures
Solution Approach 1:
The patent applies local quality by concentrating the high temperature heat treatment (700°C) only in the joint regions where ceramic paste is applied, rather than heating the entire magnet uniformly. This localized treatment strengthens joints while allowing other magnet components to remain at lower temperatures, reducing manufacturing complexity
Solution Approach 2:
The patent uses ceramic paste as an intermediary material that can withstand the high temperature heat treatment process. This intermediary enables the formation of strong joints at high temperatures while protecting other sensitive magnet materials from direct exposure to extreme heat, thereby simplifying the overall manufacturing process
4Ease of manufacture
If unreacted wire joints are used, then ease of assembly is improved, but reliability deteriorates as joints cannot be re-made if defective
Solution Approach 1:
The patent changes the physical state parameter of the ceramic paste from solid/hard to a softened, pliable state during heat treatment at 700°C. This parameter change allows defective joints to be reheated, softened, and reworked, providing reliability and reworkability while maintaining ease of assembly during the softened state
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
This approach eliminates flux jumping, enables the use of monofilament wires, reduces manufacturing risks, and simplifies the assembly process, resulting in higher critical currents and reproducibility, making it feasible to produce cost-effective MRI magnets that can operate above liquid helium temperatures.
Implementation Method 1
heat treatment at 700°C
Implementation Method 2
high-pressure ceramic paste sealing
Implementation Method 3
superconducting magnet
Data Source
AI summary
A superconducting magnet and method for making a superconducting magnet are presented. The superconducting magnet is made by forming a coil from windings of a first wire comprising a reacted MgB2 monofilament, filling a cavity of a stainless steel billet with a Mg+B powder. Monofilament ends of the first wire and a similar second wire are sheared at an acute angle and inserted into the billet. A copper plug configured to partially fill the billet cavity is inserted into the billet cavity. A portion of the billet adjacent to the plug and the wires is sealed with a ceramic paste.