Rare earth cold accumulating material particles, and refrigerator, superconducting magnet, inspection device and cryopump using same
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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 a sintered body composition, specifically controlling average crystal grain size (0.5 to 5 μm), porosity (10 to 50 vol%), and average pore size (0.3 to 3 μm) to enhance heat exchange and refrigerating capacity by allowing He gas to contact the interior pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cold accumulating materials (Cu, Pb) are used, then the material structure is simple and easy to manufacture, but the specific heat at ultralow temperatures is remarkably small, preventing sufficient thermal energy storage and inability to reach ultralow temperatures
Solution Approach 1:
The invention changes the material composition parameters by using rare earth elements (Gd, Dy, Ho, Er, Tm, Yb, Lu) instead of conventional Cu or Pb, which fundamentally alters the specific heat characteristics at ultralow temperatures. This parameter change enables the cold accumulating material to store sufficient thermal energy and achieve temperatures of 4K or lower.
Solution Approach 2:
The invention uses composite rare earth compounds including rare earth metals, rare earth oxides, and rare earth intermetallic compounds. These composite materials combine the advantages of different rare earth elements to achieve high specific heat at ultralow temperatures while maintaining structural stability and mechanical strength.
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 pore size is uncontrolled, preventing effective heat exchange with working medium
Solution Approach 1:
The invention intentionally creates a porous structure in the rare earth cold accumulating material particles with controlled pore sizes of 0.3 to 3 μm. This porous structure increases the surface area for heat exchange with the working medium while maintaining structural integrity, enabling effective thermal energy transfer at ultralow temperatures.
Solution Approach 2:
The invention precisely controls multiple parameters including particle size (100 to 500 μm), pore size (0.3 to 3 μm), and crystal grain size (0.5 to 5 μm) to optimize both the thermal properties and heat exchange efficiency. This multi-parameter control ensures the material achieves both low specific heat peak temperature and effective heat exchange capability.
3Productivity
If cold accumulating material is processed into spherical particles for efficient heat exchange, then the heat exchange efficiency is improved, but the mechanical strength may be reduced
Solution Approach 1:
The invention creates a spherical particle structure with a controlled shell thickness and porous interior. The spherical shape with diameter of 100 to 500 μm provides efficient heat exchange surfaces while the controlled porous structure and crystal grain size (0.5 to 5 μm) maintain sufficient mechanical strength to withstand operational conditions in the refrigerator.
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 controlled composition improves refrigerating capacity and mechanical strength, enabling efficient heat exchange and achieving ultralow temperatures of 10K or lower in refrigerators.
Implementation Method 1
the thermal energy of the working medium is supplied to the cold accumulating material, and the expanded working medium flows in the opposite direction and receives the thermal energy from the cold accumulating material
Implementation Method 2
the cold accumulating material has a large volume specific heat in the ultralow temperature region of 20K or lower wherein the local maximum value is large
Data Source
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 m 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.