Rare-earth cold storage material particles, refrigerator using same, superconducting magnet, inspection device, and cryopump
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Solution Overview
Problem
Conventional rare earth cold accumulating materials, such as Cu and Pb, have a small specific heat at ultralow temperatures, limiting the refrigeration capacity and ability to reach ultralow temperatures in refrigerators, and existing rare earth oxysulfide materials do not effectively utilize their heat exchange potential due to uncontrolled pore sizes.
Innovation Solution
Rare earth cold accumulating material particles with controlled average crystal grain size, porosity, and pore size, specifically between 0.5 to 5 µm, 10 to 50 vol%, and 0.3 to 3 µm respectively, are used to enhance heat exchange and refrigeration capacity by allowing helium gas to penetrate the interior of the sintered body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional metal-based cold accumulating material (Cu, Pb) is used, then the material has good mechanical strength, but the specific heat at ultralow temperatures is remarkably small, preventing sufficient thermal energy storage
Solution Approach 1:
The invention changes the material composition from conventional metals (Cu, Pb) to rare earth intermetallic compounds (Er3Ni, ErNi, HoCu2) that exhibit a local maximum value of volume specific heat in the ultralow temperature region of 20K or lower. This parameter change in material composition enables sufficient thermal energy storage capacity while achieving ultralow temperatures.
2Temperature
If rare earth oxysulfide is used to improve refrigerating capacity, then the specific heat peak temperature is lowered to 5K or lower, but the heat exchange efficiency is reduced due to uncontrolled pore sizes
Solution Approach 1:
The invention utilizes a porous sintered body structure with controlled pore characteristics. The porous structure allows helium gas to penetrate into the interior of the cold accumulating material particles, significantly enhancing heat exchange efficiency while maintaining the low specific heat peak temperature of rare earth oxysulfide materials.
Solution Approach 2:
The invention creates a composite structure combining rare earth oxysulfide particles with a porous sintered body matrix. This composite material integrates the low specific heat peak temperature characteristic of rare earth oxysulfide with the enhanced heat exchange capability provided by the controlled porous structure.
3Productivity
If cold accumulating material is processed into spherical particles for efficient heat exchange, then the charging efficiency is enhanced, but the mechanical strength may be compromised
Solution Approach 1:
The porous sintered body structure provides inherent mechanical strength to the spherical particles while maintaining efficient heat exchange characteristics. The interconnected pore structure distributes stress throughout the particle, preventing catastrophic failure and maintaining structural integrity during operation.
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 configuration improves refrigeration capacity and mechanical strength, enabling the achievement of ultralow temperatures such as 10K or lower, while maintaining long-term reliability and stability in refrigeration systems.
Implementation Method 1
a rare earth cold accumulating material having a large volume specific heat in the ultralow temperature region of 20K or lower wherein the local maximum value is large
Implementation Method 2
the porosity of the sintered body is 10 to 50 vol%; and the average pore size of the sintered body is 0.3 to 3 µm
Data Source
Figure 1~2
Figure 3A~4
Figure 5
AI summary
The present invention provides a rare earth cold accumulating material particle comprising a rare earth oxide or a rare earth oxysulfide, wherein the rare earth cold accumulating material particle is composed of a sintered body; an average crystal grain size of the sintered body is 0.5 to 5 µm; a porosity of the sintered body is 10 to 50 vol.%; and an average pore size of the sintered body is 0.3 to 3 µm. Further, it is preferable that the porosity of the rare earth cold accumulating material particle is 20 to 45 vol.%, and a maximum pore size of the rare earth cold accumulating material particle is 4 µm or less. Due to this structure, there can be provided a rare earth cold accumulating material having a high refrigerating capacity and a high strength.