Rare Earth Regenerator Particles With Carbon Surface Oxidation Control
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Solution Overview
Problem
Conventional rare earth regenerator materials in cryogenic cold heads suffer from deterioration and clogging after 20000 to 30000 hours of continuous operation, leading to reduced long-term reliability and increased maintenance costs due to oxidation and helium gas leakage.
Innovation Solution
Development of rare earth regenerator material particles with a controlled carbon content and surface composition, specifically using intermetallic compounds like HoCu2, which are managed in an argon atmosphere or vacuum to prevent oxidation, and optimized for high specific heat capacity and mechanical strength, ensuring prolonged reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rare earth regenerator materials are used in cold heads, then the refrigerating capacity is maintained initially, but the materials deteriorate and breakage occurs after 20000 to 30000 hours of continuous operation
Solution Approach 1:
The patent applies the inert atmosphere principle by managing rare earth regenerator material particles in an argon atmosphere or vacuum environment. This prevents oxidation of the rare earth materials during continuous operation, thereby extending their operational life from 20000-30000 hours to over 40000 hours while maintaining refrigerating capacity and reliability in cold heads used in MRI and NMR apparatus.
2Reliability
If the cold head is designed with high airtightness to prevent helium gas leakage, then helium retention is improved, but maintenance burden increases due to difficulty in replacing regenerator material
Solution Approach 1:
The patent applies segmentation by dividing the regenerator material into discrete particles with controlled size distributions (0.1-0.5mm, 0.5-1.0mm, 1.0-2.0mm). These segmented particles can be individually managed and replaced more easily while maintaining the high airtightness of the cold head system, reducing the maintenance burden associated with helium gas leakage prevention.
3Productivity
If the regenerator material is designed for high refrigerating capacity, then the cold head performance is improved, but the material is more susceptible to oxidation and deterioration over time
Solution Approach 1:
The patent applies composite materials by combining rare earth elements (Ho, Er, Tm, Yb, Lu) with transition metals (Cu, Ni, Co) to create intermetallic compounds with specific stoichiometries (HoCu2, Er3Ni, Tm3Ni, YbCu2, LuCu2). These composite materials provide high refrigerating capacity through optimized specific heat characteristics while the specific compositional ratios enhance resistance to oxidation and deterioration during continuous operation.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the particle size (0.1-2.0mm with specific distribution ranges) and compositional ratios of the rare earth regenerator material particles. These parameter optimizations simultaneously improve refrigerating capacity through enhanced surface area to volume ratio and heat transfer characteristics, while also improving mechanical strength and oxidation resistance.
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 extends the operational life of cryogenic cold heads to over 40000 hours or more by suppressing oxidation and maintaining refrigerating capacity, thereby enhancing the long-term reliability of superconducting magnets and examination apparatus like MRI machines.
Implementation Method 1
Helium gas is passed through this regenerator container, and a specific heat per volume of the regenerator material is utilized to obtain the cryogenic temperature
Implementation Method 2
a peak indicating a carbon component is detected in a surface region by an X-ray photoelectron spectroscopy analysis
Data Source
AI summary
A rare earth regenerator material particle and a regenerator material particle group having a high long-term reliability, and a superconducting magnet, an examination apparatus, a cryopump and the like using the same are provided. A rare earth regenerator material particle contains a rare earth element as a constituent component, and in the particle, a peak indicating a carbon component is detected in a surface region by an X-ray photoelectron spectroscopy analysis.