Rare earth oxysulfide cold storage medium
Solution Overview
Problem
Existing cold storage materials, such as rare earth intermetallic compounds, have insufficient heat capacity and durability in ultra-low temperature ranges and are prone to breakage under prolonged operation, especially in small refrigerators used for superconducting devices.
Innovation Solution
A rare earth oxysulfide ceramic material represented by R2O2S, with 3 to 12% by weight of Al2O3 added, forms a second phase that suppresses crystal grain growth, enhancing durability and maintaining high heat capacity in the ultra-low temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If rare earth intermetallic compound-based cold storage materials (such as HoCu2 and ErNi) are used to achieve large heat capacity at liquid helium temperature, then heat capacity is improved, but durability and resistance to thermal shock deteriorate, causing breakage after prolonged operation
Solution Approach 1:
The invention uses a composite material system consisting of rare earth oxysulfide ceramic as the base material with alumina (Al2O3) particles dispersed throughout. This composite structure combines the high heat capacity of rare earth oxysulfide at ultra-low temperatures with the exceptional durability and thermal shock resistance of alumina, resolving the contradiction between heat capacity and durability. The alumina particles act as reinforcement that prevents crack propagation and grain breakage during prolonged refrigerator operation.
2Ease of manufacture
If conventional metal cold storage materials (such as Pb) are used, then ease of manufacture is improved, but heat capacity deteriorates rapidly at low temperature of 10 K or less
Solution Approach 1:
The invention changes the material parameter from conventional metals to rare earth oxysulfide ceramic, which fundamentally alters the heat capacity characteristics at ultra-low temperatures. The rare earth oxysulfide maintains high heat capacity down to 4.2 K due to its unique crystal structure and magnetic properties, whereas conventional metals like lead exhibit rapidly decreasing heat capacity below 10 K. This parameter change enables sufficient refrigerating capacity while maintaining manufacturability through ceramic processing techniques.
3Use of energy by moving object
If rare earth oxysulfide ceramic cold storage materials are used to achieve high heat capacity in ultra-low temperature range, then heat capacity is improved, but strength deteriorates, making the material prone to breakage under thermal shock and mechanical vibration
Solution Approach 1:
The invention applies local quality enhancement by dispersing alumina particles throughout the rare earth oxysulfide ceramic matrix. The alumina particles are strategically distributed to provide localized reinforcement at critical points where stress concentration occurs during thermal cycling and vibration. This creates a heterogeneous structure where different regions have different properties: the rare earth oxysulfide provides high heat capacity while the alumina-rich regions provide enhanced strength and crack 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 Al2O3-added rare earth oxysulfide ceramic exhibits high thermal capacity and resistance to thermal shock and mechanical vibration, ensuring long-term operation without grain breakage, even after 10000 hours, while maintaining sufficient cooling performance.
Implementation Method 1
3 to 12% by weight of Al2O3 added, forms a second phase that suppresses crystal grain growth, enhancing durability and maintaining high heat capacity in the ultra-low temperature range
Implementation Method 2
having a high heat capacity in a ultra-low temperature range of 10 K or less, and confirmed that a regenerator using the cold storage material achieves a high refrigerating capacity even in a ultra-low-temperature around 4.2 K
Data Source
AI summary
A cold storage material having a large thermal capacity in a ultra-low temperature range of 10 K or less and being highly durable against thermal shock and mechanical vibration. The cold storage material contains a rare earth oxysulfide ceramic represented by the general formula R2O2S in which R is one or more kinds of rare earth elements selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, and Al2O3 having a specific surface area of 0.3 m2/g to 11 m2/g is added to the cold storage material.