Cold storage material, refrigerator, device incorporating superconducting coil, and method of manufacturing cold storage material
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Solution Overview
Problem
Existing cold storage materials for extremely low temperatures face challenges with large magnetization, mechanical strength, and complex manufacturing processes, leading to reliability issues and noise interference in superconducting systems.
Innovation Solution
A granular intermetallic compound with a ThCr2Si2-type structure, produced through rapid cooling and solidification, offering high specific heat and mechanical strength, and a manufacturing method involving blending, melting, and dynamic cooling to form granules with controlled crystallite size and shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If oxide cold storage materials such as GOS are used to achieve large specific heat, then the specific heat characteristic is improved, but the manufacturing process becomes complex and costly
Solution Approach 1:
The invention changes the manufacturing parameters by using rapid solidification technique with cooling rates of 10^3 to 10^6 K/s, which fundamentally alters the crystallization process compared to conventional slow cooling methods. This enables the formation of fine-grained intermetallic compounds directly from melt, eliminating the need for multi-step processes including high-temperature sintering and spherical finishing that are required for oxide materials like GOS
Solution Approach 2:
The invention replaces the mechanical grinding and spherical finishing processes with a metallurgical process. By controlling the solidification rate, the material self-organizes into fine-grained spherical or near-spherical particles during casting, eliminating the need for subsequent mechanical size reduction and shape modification steps
2Use of energy by moving object
If cold storage materials with large magnetization are used, then the specific heat capacity is improved, but magnetic noise increases and reliability decreases
Solution Approach 1:
The invention uses intermetallic compounds with specific compositions (RCu2X2 where R is rare earth element and X is Si or Ge) that create a composite crystal structure. This structure combines the high specific heat capacity contribution from rare earth elements with the low magnetization characteristics of the Cu2X2 matrix, achieving both high energy storage capacity and low magnetic noise
Solution Approach 2:
The invention achieves different local properties within the material structure. The rare earth element sites provide high specific heat capacity while the Cu2X2 matrix regions provide low magnetization. This spatial distribution of different functional qualities within the crystal structure allows simultaneous optimization of both thermal and magnetic properties
3Ease of manufacture
If simple melt-solidification process is used for manufacturing, then the manufacturing complexity is reduced, but the material structure becomes inadequate requiring additional heat treatment
Solution Approach 1:
The invention performs the structural refinement action during the solidification process itself rather than as a subsequent step. By controlling the cooling rate during solidification, the material undergoes equiaxed grain formation and homogeneous phase distribution in advance, eliminating the need for post-solidification heat treatment to achieve uniform structure
4Stability of the object's composition
If high-temperature and long-time heat treatment is applied after melt-solidification, then the material uniformity is improved, but the manufacturing cost and time increase
Solution Approach 1:
The invention skips the conventional heat treatment step entirely by rushing through the solidification process with controlled rapid cooling. This high-rate solidification directly produces the desired fine-grained uniform structure in one step, eliminating the time-consuming intermediate heat treatment stage that would otherwise be required to achieve similar uniformity
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 solution provides a cold storage material with reduced magnetization, enhanced mechanical strength, and improved manufacturability, resulting in high-efficiency refrigeration and reduced magnetic noise, suitable for superconducting coils in MRI systems and other applications.
Implementation Method 1
a process of rapidly cooling and solidifying the molten liquid into granules by injecting the molten liquid into a dynamic cooling medium
Data Source
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AI summary
Provided are a cold storage material which has large specific heat and small magnetization in a very low temperature region and has good manufacturability, and a method of manufacturing the same. Further provided is a refrigerator which is charged with the cold storage material and provides high efficiency and excellent cooling performance. Furthermore, a device incorporating a superconducting coil which is capable of reducing the influence of magnetic noise due to cold storage material is provided. A cold storage material of an embodiment is