JPS6230829A - Working substance for magnetic refrigeration and its production - Google Patents

Abstract

PURPOSE:To manufacture a working substance for magnetic refrigeration excellent in magnetic refrigerating performance by bringing a melt containing Gd, Tb, Dy, Ho and Er into contact with a Cu or Ag tape under specific conditions to undergo rapid cooling so as to be compounded integrally. CONSTITUTION:An alloy containing 1 or >=2 rare earth elements selected from Gd, Tb, Dy, Ho and Er by about 20-80 atomic % is prepared. The melt of the above alloy is brought into contact with the Cu or Ag tape of a temp. between room temp. and 600 deg.C (preferably 50-600 deg.C) moving in vacuum or in an inert gas atmosphere to undergo rapid cooling. In this way, the amorphous alloy or polyphase microcrystalline aggregate alloy containing rare earth elements and the Cu or Ag tape are compounded integrally so that the working substance for magnetic refrigeration having high magnetic entropy in a temp. region of about 20-300K and also having high thermal conductivity can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic refrigeration working material for a magnetic refrigerator and a method for producing the same.

BACKGROUND OF THE INVENTION In recent years, the range of low-temperature applications has expanded significantly9, and there is a demand for the development of efficient refrigerators.

In conventional refrigeration methods that repeatedly compress and expand gas, the efficiency decreases as the temperature decreases. Therefore, magnetic refrigeration, which is based on a completely new principle, has attracted attention.

Generally, when a magnetic material is inserted into a strong magnetic field and its magnetic spins are aligned, heat is generated. After removing this heat to the outside, the magnetic material is pulled out of the strong magnetic field and the magnetic spin is disturbed, causing heat absorption, which takes heat from the external object to be frozen and freezes it. Magnetic refrigeration uses this principle,
Mechanistically, it corresponds to the compression-expansion of gas in gas refrigeration. At temperatures below 20K (Kelvin), a reverse Carnot cycle can be used, but only 20K (Kelvin).

These magnetic refrigeration methods have many advantages over conventional gas refrigeration methods, such as higher refrigeration efficiency, reduced vibration and noise because they do not require a compressor, smaller size and lighter weight, and computer control. It has certain characteristics. In order to put such an excellent magnetic refrigeration method into practical use, it is essential to develop high-performance magnetic refrigeration materials.

Currently, Gd5GasOus Gd5 (Gdt-
Garnet single crystals such as xAlx)io+z are said to have excellent properties, and magnetic refrigeration tests are being conducted using them.

In the above-mentioned Garnezot system, the Neel temperature of the antiferromagnetic 7 paramagnetic transition is near IK, and this transition can be utilized below 20, but above 20, the change in magnetic entropy due to the external magnetic field becomes small and freezing Capacity is significantly reduced.

In magnetic refrigerators in the temperature range from 20°C to 300°C, it is advantageous to fully utilize the large magnetic entropy change caused by the external magnetic field near the Curie temperature of the ferromagnetic-paramagnetic transition. This magnetic refrigeration working material is required to have a Curie temperature within the working temperature range.

Furthermore, it is required to have a large magnetic moment, a small lattice specific heat, and a high thermal conductivity.

In particular, thermal conductivity is an important factor that determines the operating speed of a magnetic refrigeration cycle, and currently W is a material with excellent properties in this temperature range. i3. c-There is.

OBJECTS OF THE INVENTION The present invention provides a magnetic refrigeration material having a large magnetic entropy, high thermal conductivity, and excellent magnetic refrigeration performance in the temperature range of 20 to 300 degrees Celsius, and a method for producing the same. .

Structure of the Invention In order to achieve the above object, the present inventors conducted research and found that Gd1Tbs DYlH, a rare earth element with a large magnetic moment.
A melt of an alloy containing one or more of O and Er is rapidly cooled with a temperature-controlled Cu or Ag tape in vacuum or an inert gas atmosphere to form an amorphous alloy or a multilayer microcrystalline aggregate. It has been found that when the alloy is integrated with Cu or Ag tape, a working material with excellent magnetic refrigeration performance, which has a high magnetic entropy over a wide temperature range, and also has high thermal conductivity, can be obtained. The present invention was completed based on this knowledge.

The gist of the present invention is as follows: 1) A composite of an amorphous alloy or a multiphase microcrystalline aggregate alloy containing one or more rare earth elements selected from Gdt Tbx D7% HO and Er, and a Cu or Ag tape. A magnetic refrigeration working substance characterized by being integrated.

2) Also, Gd % Tb s Dy % Ho and Er
A melt containing one or more rare earth elements selected from the following is quenched in vacuum or in an inert gas atmosphere by contact with a moving Cu or Ag tape at room temperature to 600°C to form an amorphous material. crystalline alloy or multiphase microcrystalline aggregate alloy, and Cut
The present invention provides a method for producing a magnetic refrigeration material, which is characterized by compositely integrating Agf-111 or Agf-111.

Rare earth elements such as Gd, Tb% D7s Ha and Er have a large magnetic moment, so alloys containing them are excellent as materials for magnetic refrigeration. An alloy containing 20 to 80 atoms of these elements alone or two or more is preferred. If the rare earth element component exceeds 80 atoms, an amorphous alloy or a multiphase microcrystalline aggregated alloy cannot be obtained, but a nearly single-phase crystal structure is obtained, and the refrigeration capacity is significantly reduced. On the other hand, if the amount is less than 20 atoms, the magnetic moment becomes small, so the magnetic entropy decreases rapidly, and the refrigerating ability is no longer exhibited, so it is preferably 20 to 80 atoms.

Depending on the composition, the temperature of the tape may be room temperature, but heating improves its wettability with the melt, which improves its closeness with the alloy, resulting in better thermal conductivity and a more uniform thickness. .

Therefore, it is preferable to set it as 50-600 degreeC.

At 50-400°C, a composite tape in which the amorphous alloy and Cu or Ag tape are integrated is obtained;
At 0° C., a composite tape is obtained in which a Cu or Ag tape is integrated with an alloy consisting of a collection of high-density, multi-phase microcrystals.

In the former composite tape, the Curie temperature can be easily controlled by the composition of the amorphous alloy, and the magnetic entropy is large over a wide temperature range centered on the Curie temperature. It conducts heat, has high thermal conductivity, and has excellent magnetic refrigeration performance, making it a magnetic refrigeration working material with particularly high refrigeration cycle efficiency.

In addition, in the latter composite tape, the Curie temperature of each phase can be controlled to be distributed between 300 and 20 K depending on the composition of the multi-phase microcrystalline aggregate alloy, and the magnetic entropy is large in this temperature range, and the magnetic entropy depends on the temperature. The change is gradual, and heat is conducted through the Cu or Ag tape.
It has high thermal conductivity and excellent magnetic refrigeration performance, making it a magnetic refrigeration material with particularly high refrigeration cycle efficiency.

Note that if the temperature of the tape exceeds 600°C, the crystal grains will become coarse and brittle, which is not preferable.

The thickness of the magnetic refrigeration material, or alloy, can be controlled by the speed of movement of the Cu or Ag tape. The higher the moving speed, the thinner the alloy becomes. The alloy to tape thickness ratio can be selected based on the design specifications of the magnetic refrigerator. Generally, the tape moving speed is 5 to 30 m/s
The thickness is preferably 10 to 10011rn. If it is less than 10 μm, the stability as a composite tape will be insufficient, while if it exceeds 100 μm, eddy current loss will increase and the magnetic refrigeration efficiency will decrease.

Example 1 An ingot with the composition shown in Table 1 prepared in advance by an arc melting method was melted in vacuum by a levitation method, and the melt was rapidly cooled from a fine-hole nozzle onto a Cu cooling body at room temperature to form an amorphous material. An alloy was made.

Next, the melt was passed through a small hole nozzle at room temperature at a speed of 20 m/s.
A composite tape was prepared by rapidly cooling an amorphous alloy having a thickness of approximately 20 μm onto a moving Cu tape having a thickness of 20 μm.

Table 1 Changes in magnetization of the obtained amorphous alloy and composite tape due to temperature were measured in a magnetic field H up to 7.5 T (Tesla),
Magnetic entropy ΔSM, which is the main magnetic refrigeration performance, was determined. Maximum value of magnetic entropy ΔS M maX s
Temperature T m a x sΔSMma indicating ΔSMmax
Temperature range ΔT where 63M shows a value of 60% or more with respect to x
6 (1s and thermal conductivity λ are shown in Table 2.

Table 2 Changes due to temperature at 63M are gradual, and ΔTea is very wide. Also, ΔSMmax s T max , ΔT
u can be easily controlled by changing the type of rare earth element and its content. Comparing the ΔSMmaX% λ of the amorphous alloy and composite tape, ΔSMmax decreases to about 2/3 due to the composite with Cu tape, but
λ becomes significantly higher.

When this amorphous alloy composite tape is used as a magnetic refrigeration material, it exhibits high refrigeration capacity over a wide temperature range, and
This makes it possible to create magnetic refrigerators with high cycle efficiency.

Example 2゜Table 3 An ingot with the fm composition shown in Table 3 prepared in advance by an arc melting method was melted in vacuum by a levitation method, and the melt was passed through a fine hole nozzle onto a Cu cooling body heated to 480°C. A multiphase microcrystalline aggregate alloy was prepared by rapid cooling. next,
The melt was heated to 480°C from the pore nozzle at a speed of 20 m.
quenched on a 20 μm thick Cu tape moving at /s,
A composite tape was prepared by depositing a multiphase microcrystalline aggregate alloy with a thickness of about 20 μm.

ΔSMmax of multiphase microcrystalline aggregate alloys and composite tapes
v Tmax, ΔTao1 and λ are shown in Table 4.

This multi-phase microcrystalline aggregate alloy consists of GdCu (Tc = 90K), GdCu with different Curie temperatures Tc
A1 (Tc = 67K), Gd Alz (Tc = 1
68K), Gd5i (Tc=50K) and DyN
1 (Tc=48K), DyNiA1 (Tc=39K)
,D)'A12 (TO=68K), Dy5iz
(Tc = 17 K), the change due to temperature of 68M is very gradual, and Δ
Tu is wide. Further, Tmax and ΔTso can be easily controlled by changing the type of rare earth element and its content. ΔS of multiphase microcrystalline aggregate alloy and composite tape
Comparing Mmax and λ, 68Mmax decreases to about 2/3 by combining with Cu tape, but
λ becomes significantly higher. When this multiphase microcrystalline aggregated alloy composite tape is used as a magnetic refrigeration working material, a magnetic refrigerator that exhibits high refrigeration capacity over a wide temperature range and has high cycle efficiency becomes possible.

In Example 1.2, when the Cu substrate temperature was heated to 100° C. or higher, it was observed that the uniformity of the thickness of the alloy and the closeness between the alloy and the Cu substrate were improved.

In addition, although the case where Cu tape was used was shown in the Example, the same result was happily obtained when Ag tape was used instead.

The effect of the invention is that the Curie temperature can be easily controlled by the composition of the tape, and the magnetic entropy is large over a wide temperature range centered on the Curie temperature, and the change in magnetic entropy due to temperature is gradual, resulting in a magnetocaloric effect. It is an excellent material for magnetic refrigeration because of its large size and high thermal conductivity.

Therefore, a magnetic refrigerator for generating a low temperature environment from room temperature to 20 degrees is possible. This magnetic refrigerator has higher efficiency than conventional gas refrigerators, and can be made smaller and lighter.

Patent applicant: Ryu Kawa, Director, Research Institute for Metals, Science and Technology Agency −

Claims (1)

[Claims] 1) An amorphous alloy or multiphase microcrystalline aggregate alloy containing one or more rare earth elements selected from Gd, Tb, Dy, Ho, and Er, and Cu or Ag tape. A magnetic refrigeration material characterized by being integrated into a composite material. 2) Moving a melt containing one or more rare earth elements selected from Gd, Tb, Dy, Ho, and Er in a vacuum or in an inert gas atmosphere at room temperature to 600°C
1. A method for producing a magnetic refrigeration material, which comprises contacting and rapidly cooling a Cu or Ag tape to composite and integrate an amorphous alloy or a multiphase microcrystalline aggregate alloy with the Cu or Ag tape.