JP2957294B2 - Cryogenic heat storage material and cryogenic heat storage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the Invention]

[0002]

The present invention relates to a cryogenic heat storage material and
It relates to a cryogenic regenerator filled with the same.

[0003]

2. Description of the Related Art In recent years, superconducting technology has been remarkably developed, and as its application field has expanded, the development of a small, high-performance refrigerator has become indispensable. Such refrigerators are required to be lightweight, small, and have high thermal efficiency. For this reason, research has been actively conducted on new refrigeration methods (magnetic refrigeration) using a thermal cycle (for example, Carnot and Ericsson) using the magnetocaloric effect instead of gas refrigeration, and on improving the performance of gas refrigeration using the Stirling cycle. Have been done.

[0004] In order to improve the performance of a gas refrigerator by a heat cycle such as the above-mentioned Stirling or the like, it is important to improve the regenerator, the compression section and the expansion section. In particular, the heat storage material constituting the heat storage device greatly affects its performance. As such a heat storage material, a material having a high specific heat even at 20 K or less, at which the specific heat of copper or lead is remarkably reduced, has been demanded.

[0005] The regenerator is often incorporated in a refrigerator and used, for example, in a device operating in a Stirling cycle, a device operating in a Villemeier, or a Gifford-McMahon type device. In these devices, the compressed working medium flows unidirectionally through the regenerator and supplies its thermal energy to the packing material, where the expanded working medium flows in the opposite direction and heat energy from the packing material. Receive. As the recuperation effect becomes better in such a process, the thermal efficiency of the working medium cycle becomes better and a lower temperature can be realized.

[0006] By the way, in the low-temperature regenerator, conventionally,
The filling material was constituted by a ball of lead or bronze, or a wire mesh layer of copper or phosphor bronze. However, such a packing material has an excessively low specific heat at a cryogenic temperature of 20 K or less, so that during the above-described operation of the refrigerator, sufficient heat energy is stored in the packing material at each cycle under the cryogenic temperature. And the working medium cannot receive sufficient heat energy from the filling material. As a result, there is a problem in that a refrigerator incorporating such a regenerator having such a filling substance cannot reach extremely low temperatures.

Therefore, in order to improve the recuperation characteristics of the regenerator at extremely low temperatures, the regenerator has a maximum specific heat of 20 K or less,
And its value is sufficiently large in specific heat per unit volume (specific heat of volume), R-Rh intermetallic compound (R: Sm, Gd, Tb, Dy, H
o, Er, Tm, Yb, etc. (see JP-A-51-52378), ErN
It has been proposed to use a rare earth intermetallic compound such as i _1/3 (JP-A-1-310269) as a heat storage material.

[0008]

However, the rare earth intermetallic compounds as described above have the property of being hard and brittle, and it is very difficult to form them into spheres or meshes which are suitable for cold storage materials. Had the problem that it was difficult. Further, since the rare earth intermetallic compound is not necessarily chemically stable, the practical properties such as cold storage efficiency and long-term stability required as a cold storage material are not sufficient.

For this reason, a rare earth intermetallic compound which exhibits an excellent cold storage effect at an extremely low temperature such as liquid nitrogen temperature or lower, but is difficult to process because of its brittleness, is easily processed into a shape suitable for a cold storage material. There was a strong desire to develop a method.

SUMMARY OF THE INVENTION The present invention has been made in order to address such a problem, and has been developed to achieve an extremely low heat storage material containing a rare earth intermetallic compound, which can be easily processed into various shapes.
Provided is a warm heat storage material and a cryogenic heat storage device that can easily and effectively use a rare-earth intermetallic compound exhibiting an excellent cold storage effect as a filler by using such a heat storage material. The purpose is to do so.

[Structure of the Invention]

[0012]

The cryogenic storage according to the present invention is provided.
The heat substance is a smell of heat storage material having a rare earth intermetallic compound.
Of the rare earth element processed into the specified heat storage material shape
A first component comprising a metal, the rare earth intermetallic compound
Coated with a second component containing the other starting metal element
The first component and the second component are separated from their melting points.
The reaction at a low temperature also causes the rare earth metal
Characterized by being composed of a composite material with intercalated compounds precipitated
ing. The cryogenic heat storage device of the present invention is a cryogenic heat storage device filled with a heat storage material having a rare earth intermetallic compound,
The heat storage material includes a first component composed of a single metal of a rare earth element processed into a predetermined heat storage material shape, and a first component including a metal element that is the other starting material of the rare earth intermetallic compound. 2
Wherein the first component and the second component are reacted at a temperature lower than the melting points of the two to form a composite material in which the rare-earth intermetallic compound is precipitated. It is.

In the present invention, the rare earth intermetallic compound used as a part of the heat storage material is, for example, RM _z (R
Is Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, L
a, at least one element selected from the group consisting of rare earth elements such as Ce, Pr, Nd, and Pm, where M is Ni, Co, Cu, Al, Mg, Zn, Si
Represents at least one metal element selected from
Intermetallic compound containing a rare earth metal represented by a number in the range of 0.001 to 9.0), R / Rh intermetallic compound, and the like.

The rare-earth intermetallic compounds as described above, first the rare earth metals or Ranaru first component, alone or second composed of the alloy of the metal which is the other starting material for the rare earth intermetallic compound The first component and the second component are deposited by heat treatment at a temperature lower than the melting points of the two components and at which the rare earth intermetallic compound sufficiently reacts. The first component is:
It should be processed in advance into a shape suitable for the heat storage material, for example, a spherical shape or a mesh shape. Since the rare earth metal itself has plasticity, it can be easily processed into the above-described shape.

[0015] Thus, the processed rare earth metals in advance in a predetermined shape, it is reacted after coating with a metal or an alloy thereof to be reacted, by precipitating a rare earth intermetallic compound having superior cold accumulating effects It is possible to easily obtain rare earth intermetallic compounds having various shapes.

[0016] As a first component in the present invention, single metals of the rare earth elements such as mentioned above is used. rare earth
Metals that have good cold storage effect by itself. Examples of such rare earth elements include Nd, Pr, Er and the like.

When the rare earth metal having the cold storage effect as described above is used as the first component, the second component can be used as a stabilizing layer of the first component. At this time, the rare earth intermetallic compound functions as a bonding layer between the two. That is, by using a rare earth metal as described above, although a sufficient cold storage effect can be obtained by itself, since the rare earth metal is chemically active,
It cannot be easily handled alone in normal temperature air. Therefore, by covering with the second component and precipitating a rare earth intermetallic compound as a bonding layer therebetween,
It can be easily handled. Various metals and alloys can be used as the second component at this time. Also, from such a situation, it is possible to use a heavy rare earth metal or its alloy that is stable in the normal temperature atmosphere as the second component.

In the heat storage material used in the present invention, it is preferable to form a stabilized metal film after precipitating the rare earth intermetallic compound in order to further improve weather resistance. this is,
This is because the rare-earth intermetallic compound itself is not necessarily chemically stable, and the above-mentioned stabilized metal film can improve cold storage efficiency and long-term stability. Examples of the stabilizing metal include Al, Au, Ag, Cu, Ni, Pb, Fe, Cr, Co, Zn,
Examples include Sn and the like and alloys containing them. When a rare earth intermetallic compound is used as the first component, the above-mentioned stabilized metal film becomes the second component. In addition,
As described above, this does not apply to the case where the second component is used as a stabilizing layer or the case where the second component is reacted under the condition that the second component partially remains on the surface.

[0019]

Embodiments of the present invention will be described below.

Example 1 First, a neodymium rod having a diameter of 5 mm was prepared, and the surface of the neodymium rod was covered with a nickel thin plate. At this time, the atomic molar ratio was Nd: Ni = 3: 1. Next, the neodymium rod covered with the above nickel sheet was drawn until the diameter became 50 μm.

Next, the processed wire was knitted into a mesh having an opening diameter of 70 μm, and this was heat-treated in a vacuum furnace at 450 ° C. for 20 hours. By this heat treatment, it was confirmed that an Nd ₃ Ni phase was precipitated between the neodymium phase and the nickel phase.

The mesh material on which the Nd ₃ Ni phase was precipitated in this manner was cut into circular shapes having a diameter of 40 mm and a diameter of 18 mm, respectively, and each of them was plated with copper. In the mesh-like material thus obtained, the Ni layer and the Cu layer exhibit a cold storage effect at 40 K or higher, and the Nd phase and Nd ₃ Ni phase exhibit a cold storage effect at 40 K or lower.

Using the mesh-like material thus obtained, a cryogenic regenerator was constructed as follows, and its characteristics were evaluated. First, using a single-stage GM refrigerator, the heat storage material of the heat storage device was converted from the ordinary Cu mesh to the above-mentioned diameter.
It was replaced with a circular mesh of 40 mm. When the refrigerating capacity of the regenerator thus configured was measured, the regenerative power at 30K was improved from 3W when a Cu mesh was used to 9W. When the Pb mesh was replaced with the above-mentioned circular mesh having a diameter of 18 mm using a two-stage GM refrigerator, 5K
Refrigeration capacity from 0.01W to 0.8W. Furthermore, both maintain the refrigeration temperature even during continuous operation for 10,000 hours,
Improvements in cold storage effect and long-term stability were confirmed.

Example 2 First, spherical neodymium powder having a diameter of 250 μm was prepared by a rotating electrode method (REP). The surface of these Nd spheres was coated with a 2 μm thick nickel layer by electroless plating. Then, these spheres were placed in a vacuum furnace for 4 hours.
Heat treatment was performed at 50 ° C. for 20 hours. By this heat treatment, it was confirmed that an Nd ₃ Ni phase was precipitated between the neodymium phase and the nickel phase.

Using the spheres on which the Nd ₃ Ni phase was precipitated as described above, a cryogenic regenerator was constructed as follows, and its characteristics were evaluated. First, using a two-stage GM refrigerator,
From the ordinary Pb sphere, the heat storage material in the two-stage heat storage
The above Nd ₃ Ni phase was exchanged and filled with the precipitated sphere. When the refrigerating capacity of the regenerator configured in this way was measured, the refrigerating capacity at 5K was 0.01 W when using a Pb sphere.
To 1.1W. In addition, the refrigeration temperature was maintained during continuous operation for 10,000 hours.

On the other hand, as a comparison with the present invention, when a single ball of neodymium was filled in the above two-stage regenerator, the initial performance was 0.9 W, but after the operation for 10,000 hours, the initial performance was 0.9 W.
Performance dropped to 3W.

[0027]

As described above, according to the present invention,
Although it has excellent thermal properties, it is difficult to process spheres and meshes, and it is possible to easily obtain a regenerator material containing a rare earth intermetallic compound as a component, which has been difficult to put into practical use. It is possible to provide a heat storage device having excellent cold storage efficiency and long-term stability.

[0028]

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F25B 9/00

Claims (2)

(57) [Claims] 1. A heat storage material having a rare earth intermetallic compound.
A rare earth element simple metal processed into a predetermined heat storage material shape
A first component comprising the other of the rare earth intermetallic compound
Coating with a second component containing a metal element which is a starting material of
The first component and the second component are lower than the melting points of both.
Reaction at a low temperature,
Characterized by comprising a composite material in which a compound is deposited
Low temperature heat storage substance. 2. A cryogenic heat storage device filled with a heat storage material having a rare earth intermetallic compound, wherein the heat storage material is composed of a single metal of a rare earth element processed into a predetermined heat storage material shape. A second component containing a metal element which is the other starting material of the rare earth intermetallic compound;
Wherein the first component and the second component are reacted at a temperature lower than the melting points of the two to form a composite material in which the rare-earth intermetallic compound is precipitated. Low temperature heat storage.