RU2834049C2 - Granular particle used for refrigerating chamber material particle, refrigerating chamber material particle, refrigerating chamber device, refrigerator, cryogenic vacuum pump, superconducting magnet, nuclear magnetic resonance imaging apparatus, nuclear magnetic resonance apparatus, installation for drawing monocrystals with application of magnetic field and helium recondensation device - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in cryogenic engineering. Disclosed is a granular particle used for a particle of material of a refrigerating chamber. Granular particle contains rare-earth oxysulphide containing at least one rare-earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, or a rare-earth oxide containing at least one rare-earth element selected from a group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and carbon having concentration of 0.001 wt.% or more up to 50 wt.% or less. Granular particle has a relative density of 10% or more to 50% or less, wherein relative density of granulated particles is calculated by dividing average density during moulding, obtained for 50 granulated particles, by true density of constituent material. Also disclosed is a refrigerating chamber material particle, a refrigerating chamber, a refrigerator, a cryogenic vacuum pump, a superconducting magnet, apparatus for imaging nuclear magnetic resonance, apparatus based on nuclear magnetic resonance, apparatus for extracting monocrystals with application of a magnetic field and a device for helium recondensation.

EFFECT: invention makes it possible to reduce costs for production of particles of material of refrigerating chamber, to reduce reduction of strength and specific heat capacity of such particles.

21 cl, 8 dwg, 3 tbl, 48 ex

Description

Field of technology to which the invention relates

The embodiments described herein generally relate to a granular particle used for a refrigeration chamber material particle, a refrigeration chamber material particle, a refrigeration chamber device, a refrigerator, a cryogenic vacuum pump, a superconducting magnet, a nuclear magnetic resonance imaging apparatus, a nuclear magnetic resonance-based apparatus, a magnetic field-applied single crystal drawing apparatus, and a helium recondensation apparatus.

State of the art

In recent years, there has been a significant development of superconducting technology, and the development of a small and high-performance cryogenic refrigerator has become necessary with the expansion of its application areas. Such a cryogenic refrigerator should be lightweight, compact and have high thermal efficiency so that it can be practically applied in various fields.

A cryogenic refrigerator comprises a refrigeration chamber filled with a variety of refrigeration chamber materials. For example, cold is generated by heat exchange between the refrigeration chamber material and helium gas passing through the refrigeration chamber. For example, in a nuclear magnetic resonance (MRI) machine using superconductivity or a cryogenic vacuum pump, etc., used in the production of semiconductors, etc., a refrigerator based on the refrigeration cycle of the Gifford-McMahon (GM), Stirling type, or pulse tube type is used.

In addition, a high-efficiency refrigerator is also required for magnetic levitation trains to generate magnetic field strength using a superconducting magnet. In addition, in recent years, high-efficiency refrigerators have also been used in superconducting magnetic energy storage (SMES), magnetic field-based single crystal extraction plant for producing high-quality silicon substrates, etc. In addition, the development and practical application of pulse tube refrigerator, which is expected to have high reliability, is also being actively promoted.

In the superconducting magnet, MRI, etc., as described above, the liquid helium used evaporates, and therefore the supply of liquid helium becomes a problem. In recent years, the problem of helium depletion has become serious, and helium has become difficult to obtain, which has affected the industry.

In order to reduce the consumption of liquid helium and reduce the burden of maintenance such as refilling, helium recondensation devices have been introduced to recondense the evaporated helium, and the need for helium recondensation devices has increased. The helium recondensation device also uses a GM refrigerator or pulse tube refrigerator, which cools helium to a temperature level of 4 K to liquefy helium.

In a refrigerator, a working medium such as compressed helium (helium gas, He) flows in one direction in a refrigeration chamber filled with a refrigeration chamber material, and its thermal energy is transferred to the refrigeration chamber material. Then, the expanded working medium receives thermal energy from the refrigeration chamber material by flowing through the refrigeration chamber in the opposite direction. Since the recuperation effect is enhanced in such a process, the thermal efficiency in the working medium cycle increases, thus achieving a lower temperature. In order to smoothly exchange thermal energy between helium gas and the refrigeration chamber material, it is preferable that the refrigeration chamber material has a high specific thermal conductivity.

Since the volumetric specific heat capacity of the refrigeration chamber material filling the refrigeration chamber is higher, the thermal energy that can be stored in the refrigeration chamber material increases, so that the cooling capacity of the refrigerator increases. Therefore, it is preferable to fill the low-temperature side of the refrigeration chamber with a refrigeration chamber material having a high specific heat capacity at a low temperature, and to fill the high-temperature side of the refrigeration chamber with a refrigeration chamber material having a high specific heat capacity at a high temperature.

The magnetic material of the refrigeration chamber has a high volumetric specific heat capacity in a specific temperature range depending on its composition. Therefore, by combining magnetic materials of the refrigeration chamber with different compositions having different volumetric specific heat capacities, the cooling capacity of the refrigeration chamber increases, and the cooling capacity of the refrigerator improves.

In addition, since the specific thermal conductivity and heat transfer coefficient of the refrigeration chamber material filling the refrigeration chamber are higher, the efficiency of heat transfer is improved and the efficiency of the refrigerator is increased.

In a conventional refrigerator, cooling to 4 K was achieved by using particles of a metallic refrigeration chamber filling material such as lead (Pb), bismuth (Bi), or tin (Sn) to fill the high-temperature side of the refrigeration chamber, and using particles of a metallic-based magnetic refrigeration chamber material such as Er ₃ Ni, ErNi, or HoCu ₂ to fill the low-temperature side with a temperature of 20 K or less of the refrigeration chamber.

In recent years, attempts have been made to improve the cooling capacity of a refrigerator by replacing some of the magnetic particles of a metal-based refrigeration chamber material with ceramic magnetic particles of a refrigeration chamber material having a high specific heat capacity in the temperature range of 2 K to 10 K, such as Gd ₂ O ₂ S, Tb ₂ O ₂ S, Dy ₂ O ₂ S, Ho ₂ O ₂ S, and GdAlO ₃ .

The ceramic magnetic particle material of the refrigeration chamber is produced by a multi-step production process of mixing raw materials and binders, granulating the mixture, degreasing the granule at several hundred degrees, sulfurizing the granule at several hundred degrees, and sintering the granule at one thousand and several hundred degrees. Therefore, if degreasing and sulfurizing can be performed at a lower temperature than the prior art, the production cost and the environmental burden can be reduced.

Literature

Patent literature

Patent Literature 1: JP 2003-73661 A.

Patent Literature 2: JP 2003-213252 A.

Patent Literature 3: WO 2018/025581 A1.

The essence of the invention

Problem solved by the invention

The object of the present invention is to obtain a granular particle used for a refrigeration chamber material particle, suitable for reducing production costs for producing the refrigeration chamber material particle.

Solutions to the problem

A granular particle used for a refrigeration chamber material particle according to an embodiment comprises: a rare earth oxysulfide having in its composition at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, or a rare earth oxide having in its composition at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; and carbon having a concentration of 0.001 mass % or more to 50 mass % or less, wherein the granular particle has a relative density of 10% or more to 50% or less.

Brief description of the drawings

Fig. 1 is a schematic cross-sectional view of a granular particle used for a refrigeration chamber material particle according to the first embodiment.

Fig. 2 is a schematic cross-sectional view of a particle of a refrigerating chamber material according to the second embodiment and a configuration of a main portion of a refrigerating chamber according to the fourth embodiment.

Fig. 3 is a schematic cross-sectional view of the configuration of a cryogenic vacuum pump according to a fifth embodiment.

Fig. 4 is a schematic perspective view of the configuration of a superconducting magnet according to a sixth embodiment.

Fig. 5 is a schematic cross-sectional view of the configuration of a nuclear magnetic resonance imaging apparatus according to a seventh embodiment.

Fig. 6 is a schematic cross-sectional view of the configuration of a nuclear magnetic resonance apparatus according to an eighth embodiment.

Fig. 7 is a schematic perspective view of the configuration of the magnetic field-assisted single crystal drawing apparatus according to the ninth embodiment.

Fig. 8 is a schematic configuration of a helium recondensation device according to a tenth embodiment.

Embodiment(s) of the invention

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same or similar elements, etc. will be designated by the same reference numerals, and the description of the same elements, etc. may be omitted accordingly.

In the present description, cryogenic temperature means, for example, a temperature range in which the phenomenon of superconductivity can be industrially useful. Cryogenic temperature is, for example, a temperature range of 20 K or less.

First variant of implementation

A granular particle used for a refrigeration chamber material particle according to a first embodiment comprises: a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu), or a rare earth oxide containing at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); and carbon having a concentration of 0.001 mass % or more to 50 mass % or less, and the granular particle has a relative density of 10% or more to 50% or less.

Fig. 1 is a schematic cross-sectional view of a granular particle used for a material particle of a refrigerating chamber according to the first embodiment.

The granular particle 101 used for the refrigeration chamber material particle according to the first embodiment is a granular particle for producing particles used for the refrigeration chamber material. For example, the particle used for the refrigeration chamber material is produced by subjecting the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment to a heat treatment for degreasing and a heat treatment for sintering. After the heat treatment for degreasing and before the heat treatment for sintering, the granular particle 101 used for the refrigeration chamber material particle can be subjected to a heat treatment for sulfurization.

As shown in Fig. 1, the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment contains, for example, powder raw materials 101a, a binder 101b and voids 101c. The granular particle 101 used for the refrigeration chamber material particle may contain, for example, a dispersion medium instead of the binder 101b. The granular particle 101 used for the refrigeration chamber material particle may contain, for example, a gelling agent instead of the binder 101b. The powder raw materials 101a may contain, for example, a sintering additive for promoting sintering during the production of the refrigeration chamber material particle.

The granular particle 101 used for the refrigeration chamber material particle is formed by granulating the powder raw materials 101a. The granular particle 101 used for the refrigeration chamber material particle is formed, for example, by bonding a plurality of powder raw materials 101a to each other with a binder 101b.

The granular particle 101 used for the material particle of the refrigeration chamber is, for example, a gel. The granular particle 101 used for the material particle of the refrigeration chamber is formed, for example, by gelling a plurality of powder raw materials 101a, using a gelling agent (gelling solution). For example, the powder raw materials 101a aggregate in a solidified state, losing independent mobility.

In the case where the granular particle 101 used for the refrigeration chamber material particle is a gel, the granular particle 101 used for the refrigeration chamber material particle contains, for example, the powder raw materials 101a and a dispersion medium. The dispersion medium contains, for example, a gelling agent. In the case where the granular particle 101 used for the refrigeration chamber material particle is a gel, the granular particle 101 used for the refrigeration chamber material particle contains, for example, the powder raw materials 101a and a gelling agent. The gelling agent that solidifies after the gelation of the granular particle 101 used for the refrigeration chamber material particle is also referred to as a gelling agent.

The raw material powder 101a contains a rare earth oxysulfide or a rare earth oxide. The rare earth oxysulfide contained in the raw material powder 101a contains at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu). The rare earth oxide contained in the powder raw material 101a contains at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

The rare earth oxysulfide contained in the powder raw material 101a is, for example, gadolinium oxysulfide or holmium oxysulfide. The rare earth oxysulfide contained in the powder raw material 101a is, for example, Gd ₂ O ₂ S, Tb ₂ O ₂ S, Dy ₂ O ₂ S or Ho ₂ O ₂ S.

The rare earth oxide contained in the powder raw material 101a is, for example, gadolinium oxide or holmium oxide. The rare earth oxide contained in the powder raw material 101a is, for example, Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , or Ho ₂ O ₃ .

The powder raw material 101a may contain, for example, a carbonate, oxide, nitride, or carbide containing a group 1 element. The powder raw material 101a contains, for example, a carbonate, oxide, nitride, or carbide containing a group 2 element.

The powder raw material 101a may contain, for example, a carbonate, oxide, nitride or carbide containing an additive element. The additive element is at least one element selected from the group consisting of manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), yttrium (Y) and boron (B).

In the case where the sintering additive is contained in the form of a powder raw material 101a, the sintering additive is, for example, an oxide. The sintering additive is, for example, aluminum oxide (alumina), magnesium oxide, yttrium oxide, zirconium oxide, or boron oxide.

The binder 101b is an organic material. The binder 101b is, for example, a resin. The binder 101b is, for example, polyvinyl alcohol, polyvinyl butyral, carboxymethyl cellulose, acrylic resin or polyethylene glycol.

In the case where the dispersion medium is contained in the granular particle 101 used for the refrigeration chamber material particle, the dispersion medium is an organic substance. The dispersion medium is, for example, alginate. The dispersion medium is, for example, sodium alginate, ammonium alginate, or potassium alginate.

The granular particle 101 used for the refrigeration chamber material particle has a relative density of 10% or more to 50% or less.

For example, when the relative density of the granular particle 101 used for the refrigeration chamber material particle is low, the volume ratio of the powder raw materials 101a in the granular particle 101 used for the refrigeration chamber material particle is relatively small. When the relative density of the granular particle 101 used for the refrigeration chamber material particle is low, the volume ratio of the binder 101b, the dispersion medium, or the voids 101c in the granular particle 101 used for the refrigeration chamber material particle is relatively high.

On the other hand, when the relative density of the granular particle 101 used for the refrigeration chamber material particle is high, the volume ratio of the powder raw materials 101a in the granular particle 101 used for the refrigeration chamber material particle is relatively high. When the relative density of the granular particle 101 used for the refrigeration chamber material particle is high, the volume ratio of the binder 101b, the dispersion medium, or the voids 101c in the granular particle of the granular particle 101 used for the refrigeration chamber material particle is relatively low.

The relative density of the granular particle 101 used for the particle of the material of the refrigeration chamber can be calculated, for example, by dividing the average molding density obtained for 50 granular particles by the true density of the constituent material. The average molding density of 50 granular particles is obtained by dividing the weight of these 50 particles by the volume of these 50 particles. The volume of these 50 particles can be calculated by summing the volumes of the corresponding particles obtained by taking the diameter of the equivalent circle of each particle as the diameter of the particle itself.

In calculating the true density of the granular particle 101 used for the refrigeration chamber material particle, first, the crystallization phase of the powder raw materials 101a of the material constituting the granular particle is identified by means of an X-ray diffraction measurement. Then, the ratio of the powder raw materials 101a constituting the granular particle is obtained from the Rietveld analysis or the inductively coupled plasma atomic emission spectroscopy on the X-ray diffraction pattern. The true density of the granular particle 101 used for the refrigeration chamber material particle can be calculated from the crystallization phase of the powder raw materials 101a and the ratio of the constituents of the powder raw materials 101a.

The granular particle 101 used for the refrigeration chamber material particle has a particle diameter of, for example, 50 μm or more to 7 mm or less. The granular particle 101 used for the refrigeration chamber material particle has an aspect ratio of, for example, 1 or more and 5 or less. The aspect ratio of the dimensions of the granular particle 101 used for the refrigeration chamber material particle is the ratio of the major axis to the minor axis of the granular particle 101 used for the refrigeration chamber material particle. The shape of the granular particle 101 used for the refrigeration chamber material particle is, for example, spherical.

In the description provided, the particle diameter of the granular particle 101 used for the refrigeration chamber material particle is the diameter of the equivalent circle. The diameter of the equivalent circle is the diameter of a perfect circle corresponding to the area of the figure observed in an image such as an optical microscope image or a scanning electron microscope image (SEM image). The particle diameter of the granular particle 101 used for the refrigeration chamber material particle can be obtained, for example, by analyzing an optical microscope image or an SEM image.

The granular particle 101 used for the refrigeration chamber material particle contains carbon. The carbon contained in the granular particle 101 used for the refrigeration chamber material particle has a concentration of 0.001 mass % or more and 50 mass % or less.

Carbon is contained, for example, in the binder 101b or in the dispersion medium. For example, when the relative density of the granular particle 101 used for the refrigeration chamber material particle is low, the carbon concentration is relatively high. For example, when the relative density of the granular particle 101 used for the refrigeration chamber material particle is high, the carbon concentration is relatively low.

The granular particle 101 used for the refrigeration chamber material particle contains, for example, an element of group 1. The element of group 1 is, for example, at least one element selected from the group consisting of lithium (Li), sodium (Na), and potassium (K).

The element of group 1 is contained, for example, in the powder raw materials 101a, the binder 101b, or the dispersion medium. The element of group 1 is obtained, for example, from a helium solution used in the production of the granular particle 101 used for the particle of the refrigeration chamber material.

The element of Group 1 contained in the granular particle 101 used for the refrigerating chamber material particle has a concentration of, for example, 0.001 at% or more to 60 at% or less.

The granular particle 101 used for the refrigeration chamber material particle contains, for example, an element of group 2. The element of group 2 is, for example, at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

The element of group 2 is contained, for example, in the powder raw materials 101a, the binder 101b, or the dispersion medium. The element of group 2 is obtained, for example, from a helium solution used in the production of the granular particle 101 used for the particle of the refrigeration chamber material.

The element of Group 2 contained in the granular particle 101 used for the refrigerating chamber material particle has a concentration of, for example, 0.001 at% or more to 60 at% or less.

The granular particle 101 used for the refrigeration chamber material particle contains, for example, an additive element which is at least one element selected from the group consisting of manganese (Mg), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), yttrium (Y) and boron (B).

The additive element is contained, for example, in the raw material powders 101a, the binder 101b or in the dispersion medium. The additive element is obtained, for example, from a helium solution used in the production of the granulated particle 101 used for the refrigeration chamber material particle.

The additive element contained in the granular particle 101 used for the refrigeration chamber material particle has a concentration of, for example, 0.001 at% or more to 60 at% or less.

Detection of an element contained in the granular particle 101 used for the refrigeration chamber material particle and measurement of the atomic concentration of the element can also be performed, for example, for a solution of the granular particle in a liquid, using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray spectroscopy (WDX) can also be used.

The method for producing the granular particle used for the refrigeration chamber material particle according to the first embodiment is not particularly limited, but, for example, the granular particle can be produced by mixing powder raw materials and a binder using a ball mill, etc., to prepare a raw material mixture, and forming (granulating) the obtained raw material mixture into a granule by a rolling granulation method, a mixing granulation method, an extrusion method, a spraying method, an injection molding method, etc.

In granulation, the strength of granulated particles is increased by adding a binder so that the powder raw materials stick together. For the binder, for example, polyvinyl alcohol, polyvinyl butyrol, carboxymethyl cellulose, acrylic resin or polyethylene glycol can be used. The binder is added in an amount of, for example, 0.01% by weight or more to 40% by weight or less. For example, by increasing the amount of the binder, it is possible to increase the tensile strength even though the relative density is low.

For powder raw materials, oxide or oxysulfide can be used. The type and proportion of oxide or oxysulfide are adjusted according to the target particle composition of the material used for the refrigeration chamber material.

A carbonate, oxide, nitride or carbide containing a group 1 element, a group 2 element or an additive element can be used for a powder raw material. The additive element is at least one element selected from the group consisting of manganese (Mg), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), yttrium (Y) and boron (B). Using a carbonate, oxide, nitride or carbide containing a group 1 element, a group 2 element or an additive element for a powder raw material, it is possible to produce a granular particle for a refrigeration chamber material containing a group 1 element, a group 2 element or an additive element.

The raw material mixture may contain a sintering aid for the powder raw material. The sintering aid may be, for example, aluminum oxide (alumina), magnesium oxide, yttrium oxide, zirconium oxide, or boron oxide.

In rolling granulation, for example, the relative density of the granulated particle used for the refrigeration chamber material can be changed by controlling the rotation speed of the granulator and the diameter of the granulator during granulation. When the rotation speed is slow or the diameter of the granulator is small, the rolling energy decreases, thereby reducing the relative density of the granulated particle used for the refrigeration chamber material.

In the production of a granular particle used for a material of a refrigeration chamber according to the first embodiment, a suspension prepared by adding powder raw materials to an aqueous solution of alginic acid and mixing the powder raw materials with an aqueous solution of alginic acid can be added drop by drop to a gelling solution, and the suspension can be converted into a gel, in order to granulate the suspension into a granular form. This method is a method in which particles are granulated by causing gelation by a crosslinking reaction of polyvalent metal ions contained in the gelling solution.

By changing the ratio between the powder raw materials and the aqueous solution of alginic acid, it is possible to change the relative density of the granular particle used for the refrigeration chamber material particle. The mass ratio of the powder raw materials in the aqueous solution of alginic acid is, for example, from 0.1 or more to 20 or less.

The granular particle used for the refrigeration chamber material particle is solidified in a granular form by solidifying alginate. Therefore, the strength of the granular particle, that is, the solidification strength, changes depending on the amount of alginate contained in the particle or the viscosity of the aqueous solution of alginate. For example, by adjusting the viscosity of the aqueous solution of alginate, the alginate can reliably bind the powder raw materials in a gel, maintain the strength of the granular particle used for the refrigeration chamber material particle, and it is possible to obtain a granular particle used for the refrigeration chamber material particle having a desired shape.

The suspension can be dropped into the gelling solution using, for example, a dropper, burette, pipette, syringe, dispenser, spray nozzle, etc. Hereinafter, the above-described method of granulating particles will be referred to as a solidification method using alginic acid.

According to the solidification method using alginic acid, the particle diameter and the aspect ratio of the granular particle used for the material of the refrigeration chamber can be changed by adjusting the viscosity of the liquid solution, the diameter of the outlet during dripping, or the distance between the tip of the outlet and the liquid level of the solidification solution. The diameter of the outlet is, for example, from 50 μm or more to 3000 μm or less. The distance between the tip of the outlet and the liquid level of the solidification solution is, for example, from 0.1 mm or more to 1000 mm or less.

In case a dispenser is used for dispensing, any of the following devices can be used for the device: air pulse dispenser, plunger dispenser and piezo dispenser.

The spray nozzle in the spray method mainly refers to a continuous type spray nozzle or an on-demand spray nozzle, but any type of spray method can be used. In addition, the on-demand spray nozzle refers to a piezo type spray nozzle, a thermal type spray nozzle, and a valve type spray nozzle, but any type of spray nozzle can be used.

The suspension dropped into the solidifying solution by a dropper, burette, pipette, syringe, dispenser, spray nozzle, etc. thickens while being held in the gelling solution. When the suspension solidifies, a granular particle containing powder raw materials is formed and used for the material of the refrigeration chamber. The time during which the suspension is held in the gelling solution is, for example, 10 minutes or more to 48 hours or less. If the gelling time is short, the solidification will be insufficient, resulting in low strength of the granular particle.

The aqueous solution of alginic acid used in the gelation method using alginic acid is, for example, an aqueous solution of sodium alginate, an aqueous solution of ammonium alginate, or an aqueous solution of potassium alginate. When using an aqueous solution of sodium alginate or an aqueous solution of potassium alginate containing a group 1 element, sodium (Na) or potassium (K) may be contained in the granular particle 101 used for the refrigeration chamber material particle. When using a mixed solution of an aqueous solution of sodium alginate and an aqueous solution of potassium alginate in a liquid solution, sodium (Na) and potassium (K) may be simultaneously contained in the granular particle 101 used for the refrigeration chamber material particle.

In the aqueous solution of alginate, the alginate has a concentration of, for example, 0.1 mass % or more to 5 mass % or less. When the concentration of the aqueous solution of alginate is lower than 0.1 mass %, a gel with sufficient strength cannot be formed, and a granular particle used for a refrigerating chamber material particle cannot be obtained.

As a gelling solution, there can be used, for example, an aqueous solution of calcium lactate, an aqueous solution of calcium chloride, an aqueous solution of manganese (II) chloride, an aqueous solution of magnesium sulfate, an aqueous solution of beryllium sulfate, an aqueous solution of strontium nitrate, an aqueous solution of barium chloride, an aqueous solution of barium hydroxide, an aqueous solution of aluminum chloride, an aqueous solution of aluminum nitrate, an aqueous solution of aluminum lactate, an aqueous solution of iron (II) chloride, an aqueous solution of iron (III) chloride, an aqueous solution of copper (II) chloride, an aqueous solution of nickel (II) chloride, or an aqueous solution of cobalt (II) chloride.

When using an aqueous solution of calcium lactate, an aqueous solution of calcium chloride, an aqueous solution of manganese (II) chloride, an aqueous solution of magnesium sulfate, an aqueous solution of beryllium sulfate, an aqueous solution of strontium nitrate, an aqueous solution of barium chloride, an aqueous solution of barium hydroxide, an aqueous solution of aluminum chloride, an aqueous solution of aluminum nitrate, an aqueous solution of aluminum lactate, an aqueous solution of iron (II) chloride, an aqueous solution of iron (III) chloride, an aqueous solution of copper (II) chloride, an aqueous solution of nickel (II) chloride or an aqueous solution of cobalt (II) chloride as the gelling solution, calcium (Ca), manganese (Mn), magnesium (Mg), beryllium (Be), strontium (Sr), barium (Ba), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni) or cobalt (Co) may be contained in granular particle 101 used for the refrigeration chamber material particle.

In addition, when using an aqueous solution of aluminum chloride, an aqueous solution of aluminum nitrate, an aqueous solution of aluminum lactate, an aqueous solution of iron (II) chloride, an aqueous solution of iron (III) chloride, an aqueous solution of copper (II) chloride, an aqueous solution of nickel (II) chloride or an aqueous solution of cobalt (II) chloride as the gelling solution, aluminum (Al), iron (Fe), copper (Cu), nickel (Ni) or cobalt (Co) may be contained in the granular particle 101 used for the refrigeration chamber material particle.

Since the gelation is caused by the crosslinking reaction of the polyvalent metal ions contained in the gelling solution, in the case where an aqueous solution containing a group 1 element is used to obtain the suspension, and an aqueous solution containing an element that forms polyvalent metal ions in an aqueous solution is used for the gelling solution, the amount of the group 1 element contained in the particle and the amount of the element that forms polyvalent metal ions in the aqueous solution can be adjusted by adjusting the time that the particle, granulated by dropwise introduction of the suspension into the gelling solution, is kept in the gelling solution.

An element that forms polyvalent ions in an aqueous solution is, for example, calcium (Ca), manganese (Mn), magnesium (Mg), beryllium (Be), strontium (Sr), barium (Ba), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni) or cobalt (Co).

When using as a gelling solution a mixture of at least two kinds of aqueous solutions containing different metal elements selected from the group consisting of an aqueous solution of calcium lactate, an aqueous solution of calcium chloride, an aqueous solution of manganese (II) chloride, an aqueous solution of magnesium sulfate, an aqueous solution of beryllium sulfate, an aqueous solution of strontium nitrate, an aqueous solution of barium chloride, an aqueous solution of barium hydroxide, an aqueous solution of aluminum chloride, an aqueous solution of aluminum nitrate, an aqueous solution of aluminum lactate, an aqueous solution of iron (II) chloride, an aqueous solution of iron (III) chloride, an aqueous solution of copper (II) chloride, an aqueous solution of nickel (II) chloride and an aqueous solution of cobalt (II) chloride, two or more kinds of elements that form polyvalent ions in aqueous solutions can be contained in the granular particle 101 used for the particle of the material of the refrigeration chamber.

Next, the function and effect of the granular particle used for the material particle of the refrigerating chamber according to the first embodiment will be described.

The refrigeration chamber material particle is produced by subjecting the granular particle used for the refrigeration chamber material particle to a degreasing heat treatment and a sintering heat treatment. For example, in the case where the granular particle used for the refrigeration chamber material particle contains oxide powder raw materials, the granular particle used for the refrigeration chamber material particle may be subjected to a sulfurization heat treatment after the degreasing heat treatment and before the sintering heat treatment.

When degreasing the granular particle used for the refrigeration chamber material particle, some amount of the organic component contained in the binder or dispersion medium may be removed. For example, in the case where the powder raw material is an oxide, if the degreasing is insufficient, the oxide is not sufficiently sulfurized, and as a result, the required amount of oxysulfide cannot be obtained.

In addition, if the granular particle used for the refrigeration chamber material particle is not sufficiently degreased and the organic component remains in large quantities, the sintering reaction is also inhibited. When the sintering reaction is inhibited, the density of the refrigeration chamber material particles after sintering decreases. When the density of the refrigeration chamber material particles decreases, the strength of the material particles used for the refrigeration chamber material particles decreases, and there is a risk that the refrigeration chamber material particle will be destroyed when used in a refrigerator. In addition, when the sintering reaction is suppressed, the specific heat capacity of the refrigeration chamber material particles after sintering decreases. When the specific heat capacity of the refrigeration chamber material particles decreases, the performance of the refrigerator deteriorates.

On the other hand, if the granular particle used for the refrigeration chamber material particle is degreased too much, the organic component required to ensure strength will disappear. Therefore, the strength of the granular particle after degreasing may decrease, and the granular particle may crack or split.

The granular particle 101 used for the refrigeration chamber material particle according to the first embodiment has a relative density of 10% or more to 50% or less.

By setting the relative density of the granular particles 101 used for the refrigeration chamber material particles to 50% or less, it is easy to remove the organic component contained in the binder or in the dispersion medium during the heat treatment for degreasing. As a result, for example, the temperature of the heat treatment for degreasing can be lowered or the time of the heat treatment for degreasing can be reduced. Further, for example, the temperature of the heat treatment for sulfurization can be lowered or the time of the heat treatment for sulfurization can be reduced. Further, for example, the temperature of the heat treatment for sintering can be lowered or the time of the heat treatment for sintering can be reduced. Therefore, for the granular particles 101 used for the refrigeration chamber material particles according to the first embodiment, the heat treatment temperatures and the heat treatment time can be reduced, thereby reducing the manufacturing cost of the refrigeration chamber material particle.

From the viewpoint of reducing the heat treatment temperature for degreasing, sulfurizing or sintering or from the viewpoint of reducing the heat treatment time for degreasing, sulfurizing or sintering, the relative density of the granular particle 101 used for the refrigeration chamber material particle is preferably 45% or less, and more preferably 40% or less.

When the relative density of the granular particle used for the refrigeration chamber material particle is, for example, less than 10%, the void ratio in the refrigeration chamber material particle increases and the strength of the granular particle used for the refrigeration chamber material particle decreases. When the strength of the granular particle used for the refrigeration chamber material particle decreases, the granular particle used for the refrigeration chamber material particle is difficult to process.

When the relative density of the granular particle used for the refrigeration chamber material particle is less than 10%, the organic component may be excessively removed during the heat treatment for degreasing. When the organic component is excessively removed, the strength and specific heat capacity of the refrigeration chamber material particle decrease.

When the relative density of the granular particles used for the refrigeration chamber material particles is, for example, less than 10%, the relative density of the particles used for the refrigeration chamber material decreases and the specific heat capacity of the refrigeration chamber material particles decreases. It is believed that this is because the number of contact points between the powder raw materials decreases and the sinterability of the refrigeration chamber material particles decreases.

By setting the relative density of the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment to 10% or more, the strength of the granular particle 101 used for the refrigeration chamber material particle is maintained and the processing of the granular particle used for the refrigeration chamber material particle is facilitated.

In addition, by setting the relative density of the granular particle 101 used for the refrigeration chamber material particle to 10% or more, the excessive removal of the organic component during the heat treatment for degreasing is reduced. As a result, the decrease in strength and the decrease in specific heat capacity of the obtained refrigeration chamber material particles are reduced.

In addition, by setting the relative density of the granular particle 101 used for the refrigeration chamber material particle to 10% or more, the sinterability of the obtained refrigeration chamber material particle is increased and the specific heat capacity of the refrigeration chamber material particle is increased.

From the viewpoint of maintaining the strength of the granular particle 101 used for the refrigeration chamber material particle, the relative density of the granular particle 101 used for the refrigeration chamber material particle is preferably 15% or more, and more preferably 20% or more. Further, from the viewpoint of reducing excessive removal of the organic component during the heat treatment for degreasing, the relative density of the granular particle 101 used for the refrigeration chamber material particle is preferably 15% or more, and more preferably 20% or more. From the viewpoint of improving the sinterability of the obtained refrigeration chamber material particle, the relative density of the granular particle 101 used for the refrigeration chamber material particle is preferably 15% or more, and more preferably 20% or more.

The granular particle 101 used for the refrigeration chamber material particles according to the first embodiment contains carbon in a concentration of 0.001 mass % or more to 50 mass % or less.

When the carbon concentration in the granular particle used for the refrigeration chamber material particle is high, the strength of the granular particle used for the refrigeration chamber material particle increases. For example, when the carbon concentration in the granular particle used for the refrigeration chamber material particle is less than 0.001 mass%, the strength of the granular particle used for the refrigeration chamber material particle decreases, and the granular particle used for the refrigeration chamber material particle is difficult to process.

On the other hand, when the carbon concentration of the granular particle used for the refrigeration chamber material particle is high, the specific thermal conductivity of the refrigeration chamber material particle obtained from the granular particle used for the refrigeration chamber material particle decreases. This is because carbon in an excessive amount remains at the boundary of the crystal grains of the obtained refrigeration chamber material particle.

When the carbon concentration of the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment is 0.001 mass % or more, the strength of the granular particle used for the refrigeration chamber material particle is improved. From the viewpoint of improving the strength of the granular particle used for the refrigeration chamber material particle, the carbon concentration of the granular particle 101 used for the refrigeration chamber material particle is preferably 0.01 mass % or more, and more preferably 0.1 mass % or more.

When the carbon concentration of the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment is 50 mass % or less, the thermal conductivity of the obtained refrigeration chamber material particle increases. From the viewpoint of increasing the thermal conductivity of the obtained refrigeration chamber material particle, the carbon concentration of the granular particle 101 used for the refrigeration chamber material particle is preferably 10 mass % or less, and more preferably 5 mass % or less.

The granular particle 101 used for the refrigeration chamber material particle according to the first embodiment preferably contains a group 1 element having a concentration of 0.001 at% or more to 60 at% or less. Since the granular particle 101 used for the refrigeration chamber material particle contains the group 1 element in the above-mentioned concentration range, the sinterability of the obtained refrigeration chamber material particle can be improved. As a result, for example, the strength and specific heat capacity of the obtained refrigeration chamber material particle are increased.

From the viewpoint of improving the sinterability of the obtained refrigeration chamber material particle, the concentration of the element of Group 1 contained in the granular particle 101 used for the refrigeration chamber material particle is more preferably from 0.01 at% or more to 30 at% or less, and still more preferably from 0.1 at% or more to 10 at% or less.

The granular particle 101 used for the refrigeration chamber material particle according to the first embodiment preferably contains a group 2 element having a concentration of 0.001 at% or more to 60 at% or less. Since the granular particle 101 used for the refrigeration chamber material particle contains a group 2 element in the above concentration range, the sinterability of the obtained granular particle 101 used for the refrigeration chamber material particle can be improved. As a result, for example, the strength and specific heat capacity of the obtained refrigeration chamber material particle are increased.

From the viewpoint of improving the sinterability of the obtained refrigeration chamber material particle, the concentration of the Group 2 element contained in the granular particle 101 used for the refrigeration chamber material particle is more preferably 0.01 at% or more to 30 at% or less, and still more preferably 0.1 at% or more to 10 at% or less.

The granular particle 101 used for the refrigeration chamber material particle according to the first embodiment preferably contains an additive element having a concentration of 0.001 at% or more to 60 at% or less, wherein the additive element is at least one element selected from the group consisting of manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), yttrium (Y) and boron (B). Since the granular particle 101 used for the refrigeration chamber material particle contains the additive element in the above concentration range, the sinterability of the obtained refrigeration chamber material particle can be improved. As a result, for example, the strength and specific heat capacity of the obtained refrigeration chamber material particle are increased.

From the viewpoint of improving the sinterability of the produced refrigeration chamber material particles, the concentration of the additive element contained in the granular particle 101 used for the refrigeration chamber material particle is more preferably from 0.01 at% or more to 30 at% or less, and still more preferably from 0.1 at% or more to 10 at% or less.

The granular particle 101 used for the refrigeration chamber material particle according to the first embodiment preferably contains aluminum oxide (alumina), magnesium oxide, yttrium oxide, zirconium oxide, or boron oxide. The oxide functions as a sintering additive. Since the granular particle 101 used for the refrigeration chamber material particle contains the above-described oxide, the sinterability of the obtained refrigeration chamber material particle can be improved.

As described above, according to the first embodiment, it is possible to provide a granular particle used for a refrigeration chamber material particle suitable for reducing the production cost of the refrigeration chamber material particle.

Second embodiment

A refrigeration chamber material particle according to the second embodiment is obtained by sintering a granular particle used for the refrigeration chamber material particle according to the first embodiment.

The refrigeration chamber material particle according to the second embodiment has a particle diameter of, for example, 50 μm or more to 5 mm or less. The refrigeration chamber material particle has an aspect ratio of, for example, 1 or more to 5 or less. The aspect ratio of the refrigeration chamber material particle is the ratio of the major axis to the minor axis of the refrigeration chamber material particle. The shape of the refrigeration chamber material particle is, for example, spherical. The refrigeration chamber material particle according to the second embodiment has a relative density of, for example, 90% or more. The relative density of the refrigeration chamber material particle according to the second embodiment is preferably 93% or more. The relative density of the refrigeration chamber material particle according to the second embodiment is preferably 95% or more.

A refrigeration chamber material particle according to the second embodiment is a refrigeration chamber material particle obtained from the granular particle used for the refrigeration chamber material particle according to the first embodiment. The refrigeration chamber material particle according to the second embodiment contains a rare earth oxysulfide or a rare earth oxide. The rare earth oxysulfide contained in the refrigeration chamber material particle contains at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu). In addition, the rare earth oxide contained in the particle of the refrigeration chamber material contains at least one rare earth element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), thulium (Tm), ytterbium (Yb) and lutetium (Lu).

The maximum value of the volumetric specific heat capacity of a particle of the material of the refrigeration chamber according to the second embodiment, in a temperature range of 2 K or more to 10 K or less, is, for example, 0.5 J/(cm ³ ⋅ K) or more.

The particle of the refrigeration chamber material according to the second embodiment contains, for example, a rare earth oxysulfide represented by the general formula R _2±0.1 O ₂ S _1±0.1 (where R denotes at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu).

In the rare earth oxysulfide represented by the above general formula, the maximum value of the volumetric specific heat capacity and the temperature corresponding to the maximum value of the volumetric specific heat capacity vary depending on the selected rare earth element. Therefore, the specific heat capacity characteristic of the rare earth oxysulfide can be adjusted by appropriately adjusting the proportion of the rare earth element. The rare earth element is, for example, at least one element selected from the group consisting of Gd, Tb, Dy, Ho and Er. The rare earth element may contain, for example, two or more kinds of rare earth elements.

The particle of the refrigeration chamber material according to the second embodiment contains, for example, a rare earth oxide represented by the general formula R _1±0.1 M _1±0.1 O _3±0.1 (where R denotes at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and M denotes at least one element selected from the group consisting of Al, Cr, Mn and Fe.).

In the rare earth oxide represented by the above general formula, the maximum value of the volumetric specific heat capacity and the temperature corresponding to the maximum value of the volumetric specific heat capacity vary depending on the selected rare earth element. Therefore, the specific heat capacity characteristic of the rare earth oxide can be adjusted by appropriately adjusting the proportion of the rare earth element. The rare earth element is, for example, at least one element selected from the group consisting of Gd, Tb, Dy, Ho and Er. The rare earth element may contain, for example, two or more kinds of rare earth elements.

The refrigeration chamber material particle according to the second embodiment contains, for example, at least one element selected from the group consisting of aluminum (Al), magnesium (Mg), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), and yttrium (Y). The element is, for example, an element obtained from a sintering additive contained in the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment.

The refrigeration chamber material particle according to the second embodiment contains, for example, boron (B). Boron (B) is obtained, for example, from a sintering additive contained in the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment.

The particle of the material of the refrigeration chamber according to the second embodiment contains a substance obtained from the sintering additive in the form of an oxide, the granular particle 101 for the particle of the material for the refrigeration chamber according to the first embodiment. The oxide is, for example, aluminum oxide (alumina), magnesium oxide, yttrium oxide, zirconium oxide or boron oxide.

The particle of the refrigeration chamber material according to the second embodiment contains, for example, from 0.01 at.% or more to 20 at.% or less of at least one element selected from the group consisting of aluminum (Al), magnesium (Mg), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), yttrium (Y) and boron (B).

The element which is a sintering additive does not exhibit specific heat capacity. Therefore, when the amount of the added element exceeds 20 at.% in the refrigerating chamber material particle, the volumetric specific heat capacity as its amount in the refrigerating chamber material particle decreases, resulting in a decrease in the performance of the refrigerating chamber of the refrigerating chamber device and a decrease in the cooling capacity of the refrigerating chamber.

The refrigeration chamber material particle according to the second embodiment has a volumetric specific heat capacity of, for example, 0.5 J/(cm ³ ⋅ K) or more in a temperature range of 2.5 K or more to 10 K or less. In addition, the refrigeration chamber material particle according to the second embodiment has a volumetric specific heat capacity of, for example, 0.55 J/(cm ³ ⋅ K) or more in a temperature range of 2 K or more to 8 K or less. In addition, the refrigeration chamber material particle according to the second embodiment has a volumetric specific heat capacity of, for example, 0.6 J/(cm ³ ⋅ K) or more in a temperature range of 4 K or more to 7 K or less.

The maximum value of the volumetric specific heat capacity of the refrigeration chamber material particle according to the second embodiment in the temperature range of 2 K or more to 10 K or less is, for example, 0.5 J/(cm ³ ⋅ K) or more. As a result, the refrigeration chamber material particle according to the second embodiment has a high volumetric specific heat capacity. Since the refrigeration chamber material particle according to the second embodiment has a high volumetric specific heat capacity, the refrigeration chamber filled with the refrigeration chamber material particle according to the second embodiment has high performance, and the refrigerator using the refrigeration chamber material particle according to the second embodiment exhibits high cooling performance.

The refrigeration chamber material particle according to the second embodiment has a particle diameter of, for example, 50 μm or more to 5 mm or less. The particle size of the refrigeration chamber material particle is preferably 1 mm or less, and more preferably 500 μm or less. When the particle size used for the refrigeration chamber material particle is larger than the above-mentioned lower limit value, the packing density of the refrigeration chamber material particles in the refrigeration chamber is low, which results in a reduction in the pressure loss of the working medium such as helium and an improvement in the cooling performance of the refrigerator. On the other hand, when the particle size used for the refrigeration chamber material particle is smaller than the above-mentioned upper limit value, the distance from the surface of the refrigeration chamber material particle to the central portion of the particle is small, which facilitates the execution of heat transfer between the working medium and the refrigeration chamber material particle and the central portion of the refrigeration chamber material, resulting in an improvement in the cooling performance of the refrigerator.

The particle diameter of the granular particle used for the refrigeration chamber material particle is the diameter of the equivalent circle. The diameter of the equivalent circle is the diameter of the ideal circle corresponding to the area of the figure observed in an image such as an optical microscope image or a scanning electron microscope (SEM) image. The particle diameter of the granular particle used for the refrigeration chamber material particle can be obtained, for example, by analyzing an optical microscope image or an SEM image.

The refrigeration chamber material particle according to the second embodiment has a relative density of, for example, 90% or more. The relative density of the refrigeration chamber material particle according to the second embodiment is preferably 93% or more. The relative density of the refrigeration chamber material particle according to the second embodiment is more preferably 95% or more.

The relative density of a particle of the refrigeration chamber material according to the second embodiment can be calculated by dividing the average density after sintering obtained for 50 particles of the refrigeration chamber material by the true density of the constituent material. The average density after sintering of these 50 particles is determined by dividing the weight of 50 particles of the refrigeration chamber material by the volume of 50 particles of the refrigeration chamber material. The volume of these 50 particles can be calculated by summing the volumes of the corresponding particles obtained by taking the diameter of the equivalent circle of each particle as the diameter of the particle itself.

The crystal structure of the rare earth oxysulfide contained in the particle of the refrigeration chamber material according to the second embodiment is, for example, of the _Ce2O2S type, and its space group is P-3m. The crystal structure can be confirmed by powder X-ray diffraction measurement, observation of a backscattered electron diffraction image using a scanning electron microscope, transmission electron microscopy _, etc.

The crystal structure of the rare earth oxide contained in the particle of the refrigeration chamber material according to the second embodiment is, for example, a perovskite type and its space group is, for example, Pnma. In addition, the space group is, for example, a Pm - 3m group. The crystal structure and the space group can be confirmed by X-ray powder diffraction measurement, observation of a backscatter diffraction electron image using a scanning electron microscope, transmission electron microscopy, and the like.

The refrigeration chamber material particle according to the second embodiment is obtained by subjecting the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment to a heat treatment for degreasing and a heat treatment for sintering. For example, in the case where the granular particle used for the refrigeration chamber material contains oxide powders of raw materials, the granular particle used for the refrigeration chamber material may be subjected to a heat treatment for sulfurization after the heat treatment for degreasing and before the heat treatment for sintering.

The heat treatment for degreasing is carried out, for example, in an air atmosphere. The temperature of the heat treatment for degreasing is, for example, 400°C or more to 700°C or less. The time of the heat treatment for degreasing is, for example, 30 minutes or more to 6 hours or less.

In the case where the oxide is used in the form of a powder raw material 101a of a granular particle 101 used for a refrigeration chamber material particle to obtain a refrigeration chamber material particle containing an oxysulfide, the granular particle 101 used for the refrigeration chamber material particle is subjected to sulfurization. In this case, the heat treatment is performed in a sulfurization atmosphere. The sulfurization atmosphere contains, for example, a gas containing sulfur atoms having a negative oxidation number, such as hydrogen sulfide (H ₂ S), carbon sulfide (CS ₂ ), or methanethiol (CH ₃ SH). The temperature of the heat treatment for sulfurization is, for example, 400°C or more to 600°C or less. The time of the heat treatment for sulfurization is, for example, 1 hour or more to 5 hours or less.

The heat treatment for sintering the degreased granular particle or the obtained oxysulfide is carried out, for example, in an inert gas atmosphere. The heat treatment temperature is, for example, 1100°C or more to 2000°C or less. The heat treatment temperature is, for example, 1200°C or more to 1800°C or less. The heat treatment time is, for example, 1 hour or more to 48 hours or less.

When the granular particle 101 used for the refrigeration chamber material particle contains a group 1 element, a group 2 element, or an additive element, the sintering temperature can be lowered by the sintering promotion effect, thereby shortening the sintering time. The additive element is at least one element selected from the group consisting of manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr), yttrium (Y), and boron (B).

The heat treatment for sintering the granular particle 101 used for the refrigeration chamber material particle containing the group 1 element, the group 2 element, or the additive element is performed, for example, in an inert gas atmosphere. The temperature of the heat treatment for sintering is, for example, 1000°C or more to 2000°C or less. The temperature of the heat treatment for sintering is, for example, 1100°C or more to 1700°C or less. The time of the heat treatment for sintering is, for example, 1 hour or more to 48 hours or less.

The refrigeration chamber material particle according to the second embodiment is obtained by sintering the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment. Therefore, for example, the heat treatment temperature for degreasing can be lowered or the heat treatment time for degreasing can be shortened. In addition, for example, the heat treatment temperature for sulfurization can be lowered or the heat treatment time for sulfurization can be shortened. In addition, for example, the heat treatment temperature for sintering can be lowered or the heat treatment time for sintering can be shortened. Therefore, the production cost of the refrigeration chamber material particle according to the second embodiment is reduced.

In addition, the refrigeration chamber material particle according to the second embodiment is obtained by sintering the granular particle 101 used for the refrigeration chamber material particle according to the first embodiment. Therefore, for example, the organic component is sufficiently removed, the amount of residual carbon contained in the refrigeration chamber material particle is reduced, thereby increasing the specific thermal conductivity of the refrigeration chamber material particle. Therefore, the performance of the refrigerator using the refrigeration chamber material particle according to the second embodiment is improved.

The refrigeration chamber material particle according to the second embodiment preferably has an aspect ratio of, for example, 1 or more to 5 or less. The aspect ratio of the refrigeration chamber material particle is more preferably, for example, 1 or more to 2 or less. When the aspect ratio of the refrigeration chamber material particle is less than the above-mentioned upper limit value, when the refrigeration chamber material particles fill the refrigeration chamber, the voids are uniform, which improves the cooling performance of the refrigerator.

As described above, according to the second embodiment, it is possible to provide a refrigeration chamber material particle capable of reducing production costs.

Third embodiment

A refrigeration chamber according to a third embodiment is a refrigeration chamber filled with a plurality of refrigeration chamber material particles according to a second embodiment. In the refrigeration chamber according to the third embodiment, for example, when the perimeter of the projection image of each of the plurality of filling refrigeration chamber material particles according to the second embodiment is denoted as L and the actual area of the projection image is denoted as A, for the proportion of the refrigeration chamber material particles having a roundness R of 0.5 or less, wherein the roundness R is represented by the formula 4πA/L ² , it is 5% or less.

The roundness R can be obtained by processing the images of the shapes of a plurality of particles of the refrigeration chamber material using an optical microscope. A particle of the refrigeration chamber material having a roundness R of 0.5 or less is a shape with irregularities on the surface, etc. When a plurality of particles of the refrigeration chamber material contain such particles of the refrigeration chamber material in an amount exceeding 5% of the number of particles filling the refrigeration chamber, the porosity formed by the particles of the refrigeration chamber material in the refrigeration chamber is uneven and the filling rate is unstable. Therefore, the performance of the refrigeration chamber deteriorates when the working medium flows in the refrigeration chamber or when the particles of the refrigeration chamber material move or break by being subjected to the stress applied to the particles of the refrigeration chamber material during the filling of the particles of the refrigeration chamber material or during the operation of the refrigeration chamber, creating fine particles that cause clogging of voids, thereby reducing the cooling performance and the long-term reliability of the refrigerator. The proportion of the refrigeration chamber material particles having a roundness R of 0.5 or less is preferably 2% or less, and more preferably 0%.

Fourth embodiment

The refrigerator according to the fourth embodiment is a refrigerator comprising a refrigerating chamber according to the third embodiment filled with a plurality of particles of a refrigerating chamber material according to the second embodiment. Hereinafter, explanations covering the explanations given in the second embodiment and the third embodiment will be partially omitted.

Fig. 2 is a schematic cross-sectional view of a particle of a refrigeration chamber material according to the second embodiment and a configuration of a main part of a refrigerator according to the fourth embodiment. Fig. 2 is a schematic cross-sectional view of a configuration of a main part of a GM refrigerator, which is an example of a refrigerator according to the fourth embodiment, including a refrigeration chamber according to the third embodiment filled with a plurality of particles of a refrigeration chamber material according to the second embodiment. The refrigerator according to the fourth embodiment is a cryogenic refrigerator 100 with a two-stage refrigeration chamber used for cooling a superconducting device and the like. The refrigeration chamber filled with a plurality of particles of a refrigeration chamber material according to the second embodiment may be a Stirling type refrigerator or a pulse tube type refrigerator, as well as a GM refrigerator.

A cryogenic refrigerator 100 with a refrigeration chamber (refrigerator) comprises a first cylinder 111, a second cylinder 112, a vacuum chamber 113, a first refrigeration chamber 114, a second refrigeration chamber 115 (refrigeration chamber), a first sealing ring 116, a second sealing ring 117, a first refrigeration chamber material 118, a second refrigeration chamber material 119 (a particle of the refrigeration chamber material), a first expansion chamber 120, a second expansion chamber 121, a first refrigeration stage 122, a second refrigeration stage 123 and a compressor 124.

The cryogenic refrigerator 100 with a refrigeration chamber comprises a vacuum chamber 113, in which a first cylinder 111 of a large diameter and a second cylinder 112 of a small diameter are installed, coaxially connected to the first cylinder 111. The first refrigeration chamber 114 is located in the first cylinder 111 so as to be able to reciprocate. In the second cylinder 112, a second refrigeration chamber 115 is located, which is an example of a refrigeration chamber corresponding to the third embodiment, so as to be able to reciprocate.

The first sealing ring 116 is located between the first cylinder 111 and the first refrigeration chamber 114. The second sealing ring 117 is located between the second cylinder 112 and the second refrigeration chamber 115.

The first refrigeration chamber 114 is filled with a first refrigeration chamber material 118, such as a copper mesh. The second refrigeration chamber 115 is filled with a plurality of particles of the refrigeration chamber material according to the second embodiment, in the form of a second refrigeration chamber material 119.

The second refrigeration chamber 115 can be divided by a metal mesh material and contain a plurality of layers filled with the refrigeration chamber material. In the case where the second refrigeration chamber 115 is divided into a plurality of filled layers, at least one filled layer is filled with a group of particles of the refrigeration chamber material containing a plurality of particles of the refrigeration chamber material corresponding to the second embodiment and is combined, for example, with at least one group of particles of the refrigeration chamber material selected from a group of lead particles for the refrigeration chamber material, a group of bismuth particles for the refrigeration chamber material, a group of tin particles for the refrigeration chamber material, a group of holmium copper particles for the refrigeration chamber material, a group of erbium nickel particles for the refrigeration chamber material, a group of erbium cobalt particles for the refrigeration chamber material and a group of gadolinium aluminum oxide particles for the refrigeration chamber material.

When combining the materials of the refrigeration chamber, the materials of the refrigeration chamber are combined in such a way that the peak temperature of the specific heat capacity is successively lowered, wherein the material of the refrigeration chamber having a higher peak temperature of the specific heat capacity is defined as the material of the first group of particles of the material of the refrigeration chamber, and the material of the refrigeration chamber having a lower peak temperature of the specific heat capacity is defined as the material of the second group of particles of the material of the refrigeration chamber.

In the case where the second refrigerating chamber 115 is a two-layer type device, examples of the combination comprise a combination in which a group of holmium copper particles of the refrigerating chamber material is used for the first group of particles of the refrigerating chamber material, and a group of particles of the refrigerating chamber material according to the second embodiment is used for the second group of particles of the refrigerating chamber material. Further, in the case where the second refrigerating chamber 115 is a three-layer type device, examples of the combination comprise a combination in which at least one group of particles of the refrigerating chamber material selected from a group of lead particles of the refrigerating chamber material, a group of bismuth particles of the refrigerating chamber material, and a group of tin particles of the refrigerating chamber material is used for the first group of particles of the refrigerating chamber material, and a group of holmium copper particles of the refrigerating chamber material is used for the second group of particles of the refrigerating chamber material, and a group of particles of the refrigerating chamber material according to the second embodiment is used for the third group of particles of the refrigerating chamber material.

The holmium copper particles for the material of the refrigeration chamber are preferably, for example, HoCu ₂ or HoCu. The erbium nickel particles for the material of the refrigeration chamber are preferably, for example, ErNi or Er ₃ Ni.

Each first refrigeration chamber 114 and second refrigeration chamber 115 has a passage through the working medium, provided in the space in the first material 118 of the refrigeration chamber or in the second material 119 of the refrigeration chamber. The working medium is gaseous helium.

The first expansion chamber 120 is located between the first refrigeration chamber 114 and the second refrigeration chamber 115. The second expansion chamber 121 is located between the second refrigeration chamber 115 and the wall of the distal end of the second cylinder 112. The first refrigeration stage 122 is located at the bottom of the first expansion chamber 120. The second refrigeration stage 123, having a lower temperature than the first refrigeration stage 122, is formed at the bottom of the second expansion chamber 121.

The high-pressure working medium is supplied from the compressor 124 to the above-described cryogenic refrigerator 100 with a two-stage refrigeration chamber. The supplied working medium passes through the first material 118 of the refrigeration chamber, filling the first refrigeration chamber 114, and enters the first expansion chamber 120. Then the working medium passes through the second material 119 of the refrigeration chamber, fills the second refrigeration chamber 115 and enters the second expansion chamber 121.

In this case, the working medium is cooled, transferring thermal energy to the first material 118 of the refrigeration chamber and the second material 119 of the refrigeration chamber. The working medium passing through the first material 118 of the refrigeration chamber and the second material 119 of the refrigeration chamber expands in the first expansion chamber 120 and in the second expansion chamber 121 to create cold. Then the first refrigeration stage 122 and the second refrigeration stage 123 are cooled.

The expanded working medium passes in the opposite direction through the first material 118 of the refrigeration chamber and the second material 119 of the refrigeration chamber. The working medium is discharged after receiving thermal energy from the first material 118 of the refrigeration chamber and the second material 119 of the refrigeration chamber. By increasing the recuperation effect by such a process, the cryogenic refrigerator 100 with such a refrigeration chamber is designed in such a way that the thermal efficiency in the working medium cycle is improved, thus achieving a lower temperature.

For the refrigeration chamber contained in the refrigerator according to the fourth embodiment, the second refrigeration chamber 115 is filled with a plurality of particles of the refrigeration chamber material according to the second embodiment as the second refrigeration chamber material 119. At least a part of the second refrigeration chamber material 119 are particles of the refrigeration chamber material according to the second embodiment.

With respect to the plurality of refrigeration chamber material particles according to the second embodiment, if the perimeter of the projection image of each of the refrigeration chamber material particles is denoted as L and the actual area of the projection image is denoted as A, it is preferable that the proportion of the refrigeration chamber material particles having a roundness R of 0.5 or less and a roundness R represented by the formula 4πA/L ² is 5% or less.

In order to increase the cooling capacity of the refrigeration chamber of the refrigerator, it is preferable to increase the volumetric specific heat capacity of the refrigeration chamber material and to increase the specific thermal conductivity and heat transfer coefficient of the refrigeration chamber material. The refrigerator according to the fourth embodiment comprises a refrigeration chamber material or particles of the refrigeration chamber material that maintain the volumetric specific heat capacity with increased specific thermal conductivity and heat transfer coefficient.

By using the refrigerator according to the fourth embodiment in a magnetic levitation train, the long-term reliability of the magnetic levitation train can be increased.

As described above, according to the fourth embodiment, a refrigerator having excellent characteristics can be realized by using particles used for a material of a refrigerating chamber having excellent characteristics.

Fifth embodiment

The cryogenic vacuum pump according to the fifth embodiment comprises a refrigerator according to the fourth embodiment. Hereinafter, the explanations that coincide with the fourth embodiment will be partially omitted.

Fig. 3 is a schematic cross-sectional view of the structure of a cryogenic vacuum pump according to a fifth embodiment. The cryogenic vacuum pump according to the fifth embodiment is a cryogenic vacuum pump 500 containing a cryogenic refrigerator 100 of a refrigerating chamber according to a fourth embodiment.

The cryogenic vacuum pump 500 comprises a cryopanel 501 that condenses or absorbs gas molecules, a cryogenic refrigerator 100 of the refrigeration chamber that cools the cryopanel 501 to a predetermined cryogenic temperature, a screen 503 located between the cryopanel 501 and the cryogenic refrigerator 100 of the refrigeration chamber, a partition 504 located in the inlet opening, and a ring 505 that changes the rate of release of argon, nitrogen, hydrogen, etc.

According to the fifth embodiment, a cryogenic vacuum pump having excellent performance can be realized by using a refrigerator having excellent performance. In addition, by using the cryogenic vacuum pump according to the fifth embodiment in a semiconductor manufacturing apparatus and the like, the long-term reliability of the semiconductor manufacturing apparatus can be improved and the number of maintenance cycles of the semiconductor manufacturing apparatus can be reduced. As a result, this contributes to improving the quality of the semiconductors to be manufactured and reducing the manufacturing cost.

Sixth embodiment

The superconducting magnet according to the sixth embodiment comprises a refrigerator according to the fourth embodiment. Hereinafter, the explanations that coincide with the fourth embodiment will be partially omitted.

Fig. 4 is a schematic perspective view of the structure of a superconducting magnet according to a sixth embodiment. The superconducting magnet according to the sixth embodiment, for example, the superconducting magnet 600 for a magnetic levitation train, comprises a cryogenic refrigerator 100 of a refrigeration chamber according to a fourth embodiment.

A superconducting magnet 600 for a magnetic levitation train comprises a superconducting coil 601, a tank 602 with liquid helium 602 for cooling the superconducting coil 601, a tank 603 with liquid nitrogen for preventing evaporation of the liquid helium, a laminated heat-insulating material 605, power supply terminals 606, a DC switch 607 and a cryogenic refrigerator 100 of a refrigeration chamber.

According to the fifth embodiment, a superconducting magnet having excellent characteristics can be realized by using a refrigerator having excellent characteristics.

Seventh embodiment

The nuclear magnetic resonance imaging device according to the seventh embodiment comprises a refrigerator according to the fourth embodiment. Hereinafter, the explanations that coincide with the fourth embodiment will be partially omitted.

Fig. 5 is a schematic cross-sectional view of a nuclear magnetic resonance imaging apparatus according to a seventh embodiment. The nuclear magnetic resonance imaging (MRI) apparatus according to the seventh embodiment is a nuclear magnetic resonance imaging apparatus 700 comprising a cryogenic refrigerator 100 with a refrigerating chamber according to the fourth embodiment.

The nuclear magnetic resonance imaging device 700 comprises a superconducting static magnetic field generating coil 701 that applies a spatially uniform and temporally stable static magnetic field to a human body, a correction coil that corrects the non-uniformity of the generated magnetic field, although not shown, a gradient magnetic field coil 702 that directs a magnetic field gradient to a measurement region, a radio wave transmitting/receiving probe 703, a cryostat 705 and a radiation adiabatic screen 706. In addition, a cryogenic refrigerator 100 of a refrigeration chamber is used to cool the coil 701 that generates a superconducting static magnetic field.

According to a seventh embodiment, a nuclear magnetic resonance imaging apparatus having excellent performance can be realized by using a refrigerator having excellent performance.

Eighth embodiment

The nuclear magnetic resonance apparatus according to the eighth embodiment comprises the refrigerator according to the fourth embodiment. Hereinafter, the explanations that coincide with the fourth embodiment will be partially omitted.

Fig. 6 is a schematic cross-sectional view of the structure of a nuclear magnetic resonance apparatus according to an eighth embodiment. The nuclear magnetic resonance (NMR) apparatus according to the eighth embodiment is a nuclear magnetic resonance apparatus 800 containing a cryogenic refrigerator 100 according to a fourth embodiment.

The nuclear magnetic resonance apparatus 800 comprises a superconducting coil 802 that generates a static magnetic field, which applies a magnetic field to a sample, such as organic matter, placed in a sampling tube 801, a high-frequency generator 803 that applies radio waves to the sampling tube 801 in a magnetic field, and an amplifier 804 that amplifies an induced current created in a coil, which is not shown, around the sampling tube 801. In addition, the nuclear magnetic resonance apparatus 800 comprises a cryogenic refrigerator 100 of a refrigeration chamber, which cools the superconducting coil 802 that generates a static magnetic field.

According to the eighth embodiment, a nuclear magnetic resonance apparatus having excellent characteristics can be realized by using a refrigerator having excellent characteristics.

Ninth embodiment

The apparatus for drawing single crystals using a magnetic field according to the ninth embodiment comprises a refrigerator according to the fourth embodiment. Hereinafter, the explanations that coincide with the fourth embodiment will be partially omitted.

Fig. 7 is a schematic perspective view of a magnetic field-applied single crystal drawing apparatus according to a ninth embodiment. The magnetic field-applied single crystal drawing apparatus according to the ninth embodiment is a magnetic field-applied single crystal drawing apparatus 900, comprising a cryogenic refrigerator 100 according to a fourth embodiment.

The apparatus 900 for drawing a single crystal based on the application of a magnetic field comprises a single crystal drawing unit 901 having a melting crucible, a heater, a single crystal drawing mechanism, etc., a superconducting coil 902 that applies a static magnetic field to the melt of the raw material, a lifter 903 of the single crystal drawing unit 901, power supply terminals 905, a heat shield plate 906 and a helium tank 907. In addition, a cryogenic refrigerator 100 of a refrigeration chamber is used to cool the superconducting coil 902.

According to the ninth embodiment, the single crystal drawing apparatus based on the application of a magnetic field, having excellent characteristics, can be realized by using a refrigeration chamber having excellent characteristics.

Tenth embodiment

The helium recondensation device according to the tenth embodiment comprises a refrigerator according to the fourth embodiment. Hereinafter, the explanations that coincide with the fourth embodiment will be partially omitted.

Fig. 8 schematically shows the configuration of the helium recondensation device according to the tenth embodiment. The helium recondensation device according to the tenth embodiment is a helium recondensation device 1000 comprising a cryogenic refrigerator 100 of a refrigerating chamber according to the fourth embodiment.

The helium recondensation device 1000 comprises a cryogenic refrigerator 100, an evaporation tube 1001 and a condenser tube 1002.

The helium recondensation device 1000 can recondense gaseous helium into liquid helium, which evaporates from a device using liquid helium or a device with liquid helium. The device using liquid helium can be a superconducting magnet, a nuclear magnetic resonance (NMR) device, a nuclear magnetic resonance imaging (MRI) device, or a physical property measurement (PPM) system. The device using liquid helium can be contained in a device using a superconducting magnet, such as a magnetic property measurement system, etc.

Gaseous helium is supplied from a liquid helium device, not shown in the helium recondensation device 1000, through an evaporation tube 1001. Gaseous helium is cooled to a temperature of 4 K, equal to or lower than the liquefaction temperature of helium by a cryogenic refrigerator 100 of the refrigeration chamber. The condensed and liquefied liquid helium is returned to the liquid helium device through a condenser tube 1002.

According to the tenth embodiment, a helium recondensation device having excellent performance can be realized by using a refrigeration chamber having excellent performance.

EXAMPLES

Hereinafter, examples of granular particles used for the refrigeration chamber material particle according to the first embodiment and the refrigeration chamber material particle according to the second embodiment, comparative examples and evaluation results thereof will be described.

Example 1

The _{Gd2O3 powders} were mixed and pulverized in a ball mill for 24 hours to prepare a raw material mixture. Then, the obtained raw material mixture was dried and further granulated using a drum granulator to prepare granulated particles having a diameter of 0.4-0.6 mm used for the refrigeration chamber material particle. In this case, polyvinyl alcohol is used as a binder, added in an amount of 1.2 mass % relative to the raw material powder. The carbon concentration in the granulated particle used for the refrigeration chamber material particle was 0.99 mass %. The relative density of the granulated particle used for the refrigeration chamber material particle was 34%.

In order to evaluate the strength of the granular particle used for the refrigeration chamber material particle, a cylindrical container with a diameter of 15 mm and a height of 5 mm was filled with the granular particles. In this case, the granular particles used for the refrigeration chamber material particle were filled in an amount sufficient to ensure that the granular particles used for the refrigeration chamber material particle were arranged in the cylindrical container so as to prevent the granular particle used for the refrigeration chamber material particle from moving freely. A single vibration with an amplitude of 2 mm and a maximum acceleration of 200 m/ ^s2 was applied to the container 1× ¹⁰³ times. As a result, the proportion of crushed granular particles used for the refrigeration chamber material particle was less than 0.1 mass%.

The granular particle used for the refrigeration chamber material particle was degreased at 600°C for 2 hours in an air atmosphere. The degreased granular particle used for the refrigeration chamber material particle had a carbon concentration of 0.51 mass% and a relative density of 40%. The granular particle used for the refrigeration chamber material particle was subjected to a heat treatment at 600°C for 2 hours in an atmosphere containing hydrogen sulfide ( _H2S ) to sulfurize the granular particles. Thereafter, the granular particle used for the refrigeration chamber material particle was subjected to a heat treatment at 1300°C for 12 hours in an inert gas atmosphere to sinter the granular particle used for the refrigeration chamber material particle, thereby creating the refrigeration chamber material particle.

The main component of the refrigeration chamber material particle in Example 1 is gadolinium oxysulfide.

In the following examples and comparative examples, the time for mixing the powder raw materials, the heat treatment mode for degreasing, the heat treatment mode for sulfurizing, the heat treatment mode for sintering, etc. are adjusted to be suitable modes.

Example 2

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 1 except that a mixture of Gd ₂ O ₃ powder and Na ₂ CO ₃ powder was used as the powder raw materials.

Example 3

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 2 except that K ₂ CO ₃ powder was used instead of Na ₂ CO ₃ powder.

Example 4

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 2 except that CaCO ₃ powder was used instead of Na ₂ CO ₃ powder.

Example 5

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 2 except that MgCO ₃ powder was used instead of Na ₂ CO ₃ powder.

Example 6

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 2 except that SrCO ₃ powder was used instead of Na ₂ CO ₃ powder.

Example 7

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 2 except that CaCO ₃ powder was used in addition to the Na ₂ CO ₃ powder.

Example 8

A granular particle used for the refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 7 except that MgCO ₃ powder was used instead of CaCO ₃ powder.

Example 9

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 7 except that SrCO ₃ powders were used instead of CaCO ₃ powder.

Example 10

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 1 except that Ho ₂ O ₃ powder was used instead of Gd ₂ O ₃ powder.

Example 11

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 2 except that K ₂ CO ₃ powders were used in addition to the Na ₂ CO ₃ powders.

Example 12

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 2 except that K ₂ CO ₃ and CaCO ₃ powders were used in addition to the Na ₂ CO ₃ powder.

Examples 13-15

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 2, except that the weight of the Na ₂ CO ₃ powder was changed.

Examples 16-18

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 7 except that the weight of the CaCO ₃ powder was changed.

Example 19

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 2 except that some amount of Gd ₂ O ₃ powder was replaced with Ho ₂ O ₃ .

Example 20

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 1 except that Gd ₂ O ₂ S powders were used instead of Gd ₂ O ₃ powders and sulfurization was not performed.

Example 21

The suspension was prepared by adding _{Gd2O3 powder} to an aqueous solution of sodium alginate and mixing them for 24 hours. The mass ratio of the powder raw materials added to the aqueous solution of alginate was 0.5. The prepared suspension was added dropwise to an aqueous solution of calcium lactate as a gelling solution. A syringe was used to add the liquid solution dropwise.

The syringe had a diameter of 510 μm, and the distance from the end of the syringe to the liquid level of the aqueous solution of calcium lactate was 100 mm. The suspension, added dropwise by the syringe, was kept in the gelling solution for 5 hours.

After that, the gel-like granular particle used for the refrigeration chamber material particle was washed with clean water. After washing, the granular particle used for the refrigeration chamber material particle was dried. The granular particle used for the material of the refrigeration chamber material particle had a sodium concentration of 0.83 at% and a carbon concentration of 0.5 mass%. The granular particle used for the material of the refrigeration chamber material particle had a relative density of 27%. After drying, the granular particle used for the refrigeration chamber material particle was degreased, sulfurized and sintered.

The granular particle used for the refrigeration chamber material particle was degreased at 500°C for 2 hours in an air atmosphere. After the degreasing, the granular particle used for the refrigeration chamber material particle had a sodium concentration of 1.0 at%, a carbon concentration of 0.25 mass%, and a relative density of 30%. After the degreasing, the granular particle used for the refrigeration chamber material particle was subjected to a heat treatment at 600°C for 2 hours in an atmosphere containing hydrogen sulfide ( _H2S ) to sulfurize the granular particle used for the refrigeration chamber material particle. The granular particle used for the refrigeration chamber material particle was subjected to a heat treatment at 1300°C for 12 hours in an inert gas atmosphere to sinter the granular particle used for the refrigeration chamber material particle, thereby producing the refrigeration chamber material particle.

The main component of the refrigeration chamber material particle in Example 21 is gadolinium oxysulfide. The sodium concentration in the refrigeration chamber material particle in Example 21 was 1.1 at.%.

Examples 22-24

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21, except that the relative density of the granular particle used for the refrigeration chamber material particle was changed by changing the ratio of the powder raw materials and the sodium alginate aqueous solution, and sodium and calcium were removed by changing the duration and number of washings.

Examples 25 and 26

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21, except that the concentration of carbon contained in the granular particle used for the refrigeration chamber material particle was changed by changing the concentration of the sodium alginate aqueous solution and the washing time was adjusted.

Example 27

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21 except that an aqueous solution of magnesium chloride was used instead of an aqueous solution of calcium lactate.

Example 28

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21 except that an aqueous solution of strontium chloride was used instead of an aqueous solution of calcium lactate.

Example 29

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 21, except that an air-pulse dispenser was used instead of a syringe for the method of dripping the liquid solution. The diameter of the nozzle was 510 μm, and the distance from the nozzle tip to the liquid level of the aqueous calcium lactate solution was 100 mm.

Example 30

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were produced in the same manner as in Example 21, except that a piezo dispenser was used instead of a syringe for the liquid dripping method. The diameter of the nozzle was 510 μm, and the distance from the nozzle tip to the liquid level of the aqueous calcium lactate solution was 100 mm.

Example 31

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21, except that a continuous type spray nozzle was used for the liquid solution dripping method instead of a syringe.

Examples 32-37

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle in Examples 32 to 37 differ in the particle diameter or the aspect ratio of the granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle in Example 21. When the granular particles used for the refrigeration chamber material particle were produced according to Examples 32 to 37, the diameter of the syringe and the distance from the tip of the syringe to the surface of the gelling solution were changed compared with the same syringe diameter and distance when the granular particle used for the refrigeration chamber material particle was produced in Example 21.

Example 38

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21 except that the relative density was set to 11% by changing the ratio between the powder raw materials and the sodium alginate aqueous solution, and by changing the holding time, the washing duration, and the number of washings, only calcium was removed.

Example 39

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21 except that the relative density was set to 11% by changing the ratio between the powder raw material and the aqueous sodium alginate solution, and by changing the holding time, the washing duration, and the number of washings, only sodium was removed.

Example 40

A granular particle used for a refrigeration chamber material particle and a _{refrigeration chamber material particle were produced in the same manner as in Example 22, except that Al2O3 powder was also used for the raw material powder. The Al2O3 powder was added} so that the refrigeration chamber material particle contained 15 at.% Al.

Example 41

A granular particle used for a refrigeration chamber material particle and a _{refrigeration} chamber material particle were produced in the same manner as in Example 38, except that _Al2O3 powder was also used for the raw material powder. _{The Al2O3} powder was added so that the refrigeration chamber material particle contained 15 at% Al.

Example 42

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example ₂₁ except that the relative density was set to 11% by changing the ratio between the powder raw material and the aqueous sodium alginate solution, and _{Al2O3 powder} was also used for the powder raw material. The _Al2O3 powder was added so that the refrigeration chamber material particle contained 15 at% of Al.

Example 43

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21 except that the relative density was set to 11% by changing the ratio between the powder raw material and the aqueous sodium alginate solution, and an aqueous aluminum chloride solution was used instead of the aqueous calcium lactate solution. The aqueous aluminum chloride solution was used such that Al was contained in the refrigeration chamber material particle in an amount of 0.01 at%.

Example 44

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21 except that the relative density was set to 11% by changing the ratio between the powder raw material and the sodium alginate aqueous solution, and an aluminum chloride aqueous solution was used to add to the calcium lactate aqueous solution. The aluminum chloride aqueous solution was used such that Al was contained in an amount of 0.01 at% in the refrigeration chamber material particle.

Example 45

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21 except that the relative density was set to 11% by changing the ratio between the powder raw material and the sodium alginate aqueous solution, and an aluminum chloride aqueous solution was used to add to the calcium lactate aqueous solution. The aluminum chloride aqueous solution was added so that Al was contained in the refrigeration chamber material particle in an amount of 20 at%.

Example 46

A granular particle used for _a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 1 except that _Gd2O3 and _{Al2O3 powders} were used for the powder raw materials and heat treatment was not performed in an atmosphere containing hydrogen sulfide ( _H2S ). The main component of the refrigeration chamber material particle is _GdAlO3 .

Example 47

A granular particle used for _a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 2 except that _Gd2O3 and _Al2O3 powders were used for the powder raw materials and heat treatment was not performed in an atmosphere containing hydrogen sulfide _H2S . The main _component is _GdAlO3 .

Example 48

A granular particle used for a refrigeration chamber material particle and a refrigeration chamber material particle were produced in the same manner as in Example 21 except that _Gd2O3 and _Al2O3 powders were used for the powder raw materials and heat treatment was _not performed in an atmosphere containing hydrogen sulfide _H2S . The main _component is _GdAlO3 .

Comparative example 1

The granular particle used for the refrigeration chamber material particle in Comparative Example 1 is different from the granular particle used for the refrigeration chamber material particle in Example 21 in that the relative density is 9%, which is smaller than that in Example 21. When the granular particle used for the refrigeration chamber material particle was manufactured in Comparative Example 1, the amount of the powder raw material was reduced compared with the amount of the material when the granular particle used for the refrigeration chamber material particle was manufactured in Example 21.

Comparative example 2

The granular particle used for the refrigeration chamber material particle in Comparative Example 2 is different from the granular particle used for the refrigeration chamber material particle in Example 21 in that the relative density is 51%, which is larger than that in Example 21. When the granular particle used for the refrigeration chamber material particle was manufactured in Comparative Example 2, the weight of the powder raw material was increased compared with when the granular particle used for the refrigeration chamber material particle was manufactured in Example 21.

Comparative example 3

The granular particle used for the refrigeration chamber material particle in Comparative Example 3 is different from the granular particle used for the refrigeration chamber material particle in Example 21 in that the carbon concentration is 0.0004 mass%, which is smaller than that in Example 21. When the granular particle used for the refrigeration chamber material particle was produced in Comparative Example 3, the concentration of the sodium alginate aqueous solution was reduced compared with when the granular particle used for the refrigeration chamber material particle was produced in Example 21.

Comparative example 4

The granular particle used for the refrigeration chamber material particle in Comparative Example 4 is different from the granular particle used for the refrigeration chamber material particle in Example 21 in that the carbon concentration is 51 mass %, which is larger than that in Example 21. When the granular particle used for the refrigeration chamber material particle was produced in Comparative Example 4, the concentration of the sodium alginate aqueous solution was increased compared with that when the granular particle used for the refrigeration chamber material particle was produced in Example 21.

Comparative example 5

The granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle in Comparative Example 5 are different from those in Example 41 in that Al contained in the refrigeration chamber material particle is 65 at%, which is larger than that in Example 41. When the granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were manufactured in Comparative Example 5, the weight of the Al ₂ O ₃ powder was increased compared with that when the granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle were manufactured in Example 41.

For the granular particle used for the refrigeration chamber material particle and the refrigeration chamber material particle corresponding to each of the examples and comparative examples, the strength of the granular particle used for the refrigeration chamber material particle and the relative density and specific heat capacity of the refrigeration chamber material particle were measured. The results are shown in Table 1, Table 2 and Table 3. In Table 1, the granular particle used for the refrigeration chamber material particle is referred to as a “granular particle”, and the refrigeration chamber material particle made from the granular particles used for the refrigeration chamber material particle is referred to as a “refrigeration chamber material particle”.

In Comparative Example 1, when the relative density of the granular particle used for the refrigeration chamber material particle is less than 10%, the granular particle cannot be restored into a spherical particle. It is considered that this is because, when the relative density is less than 10%, the proportion of voids contained in the granular particle used for the refrigeration chamber material particle is large, and accordingly, the strength of the granular particle used for the refrigeration chamber material particle is significantly reduced.

In comparative example 2, when the relative density of the granular particle used for the refrigeration chamber material particle exceeds 50%, the relative density of the obtained refrigeration chamber material particle decreases and the specific heat capacity of the obtained refrigeration chamber material particle also decreases significantly. It is considered that this is because, when the relative density of the granular particle used for the refrigeration chamber material particle exceeds 50%, the organic component contained in the granular particle used for the refrigeration chamber material particle is insufficiently removed and, accordingly, the sinterability of the refrigeration chamber material particle deteriorates.

According to the results of Comparative Example 3, when the carbon concentration in the granular particle used for the refrigeration chamber material particle is less than 0.001 mass%, the strength of the granular particle used for the refrigeration chamber material particle decreases. Therefore, the granular particle used for the refrigeration chamber material particle is easily destroyed when handled, and their production yield is significantly reduced.

According to the result of Comparative Example 4, when the carbon concentration in the granular particle used for the refrigeration chamber material particle exceeds 50 mass%, the relative density of the refrigeration chamber material particle after sintering significantly decreases, and the specific heat capacity of the refrigeration chamber material particle after sintering also significantly decreases. This is believed to be because the organic component contained in the granular particle has not been sufficiently removed, a large amount of carbon remains, and accordingly, the sinterability of the refrigeration chamber material particle deteriorates.

From Examples 22 to 24, it can be seen that the relative density of the refrigeration chamber material particle increases and the specific heat capacity of the refrigeration chamber material particle also increases in the case where the granular particle does not contain the Group 1 element or the Group 2 element and has a relative density of 15% or more to 50% or less, compared with the case where the granular particle has a relative density of 10% or more to 15% or less. This is believed to be because when the relative density is too low, the number of contact points between the powder raw materials decreases and the sinterability of the refrigeration chamber material particle decreases.

As can be seen from Examples 38 and 39, in the case where the granular particle contains a Group 1 element or a Group 2 element, the relative density of the refrigeration chamber material particle increases and the specific heat capacity of the refrigeration chamber material particle also increases, even when the granular particle has a relative density of 10% or more to 15% or less. This is believed to be due to the effect of promoting sintering of the Group 1 element and the Group 2 element.

In Examples 40 to 45, it can be seen that even when the granular particle has a relative density of 10% or more to 15% or less, if the granular particle contains a sintering aid, the relative density of the sintered particles increases. This is believed to be due to the sintering promoting effect given by the sintering aid. In the case where the granular particle has a relative density of less than 10%, even when the granular particle contains a sintering aid, the relative density of the refrigeration chamber material particle decreases and the specific heat capacity of the refrigeration chamber material particle also decreases.

According to the results of Comparative Example 5, it can be seen that in the case where the atomic concentration of the additive element obtained from the sintering additive is so large that it exceeds 60 at.%, the specific heat capacity of the refrigeration chamber material particle decreases.

According to Examples 46 to 48, it can be seen that without heat treatment in a hydrogen sulfide atmosphere, even when the main component of the refrigeration chamber material particle is GdAlO ₃ , if the granular particle used for the refrigeration chamber material particle has a relative density of 10% or more to 50% or less, the same effect as in the case where the main component is gadolinium oxysulfide is present.

The above examples confirm the results shown by the granular particle used for the refrigeration chamber material particle according to the first embodiment and the refrigeration chamber material particle according to the second embodiment.

Although an air-pulse dispenser or piezo dispenser has been described as an example of a dispenser, a plunger dispenser may also be used.

Although a continuous type spray nozzle has been described as an example of a spray nozzle, a required type of spray nozzle may be used.

Although some embodiments of the present invention have been described herein, these embodiments are illustrative and are not intended to limit the scope of the invention. These new embodiments may be embodied in various other forms and various eliminations, substitutions and changes may be made without departing from the spirit of the invention. For example, a component of one embodiment may be replaced or changed by a component of another embodiment. These embodiments and their modifications fall within the scope and spirit of the invention and fall within the scope of the equivalent of the invention as set forth in the claims.

List of reference positions

100 Cryogenic refrigerator with refrigeration chamber (refrigerator);

101 Granular particle used for refrigerating chamber material particle;

115 Second refrigeration chamber (refrigeration chamber);

119 Second refrigeration chamber material (particle of refrigeration chamber material);

500 Cryogenic vacuum pump;

600 Superconducting magnet;

700 Nuclear Magnetic Resonance Imaging Device;

800 Nuclear magnetic resonance device;

900 Device for extracting single crystals using a magnetic field;

1000 Helium recondensation device.

Claims (24)

1. A granular particle used for a refrigeration chamber material particle, wherein said granular particle comprises a rare earth oxysulfide comprising at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, or a rare earth oxide comprising at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and carbon having a concentration of from 0.001 wt.% or more to 50 wt.% or less, wherein the granular particle has a relative density of 10% or more to 50% or less, wherein the relative density of the granular particle is calculated by dividing the average molding density obtained for 50 granular particles by the true density of the constituent material. 2. The granular particle used for the refrigeration chamber material particle according to claim 1, wherein said granular particle has a particle diameter of 50 μm or more to 7 mm or less. 3. The granular particle used for the refrigeration chamber material particle according to claim 1 or 2, wherein the granular particle has an aspect ratio of 1 or more to 5 or less. 4. The granular particle used for the refrigeration chamber material particle according to any one of claims 1 to 3, further containing a Group 1 element having a concentration of 0.001 at% or more to 60 at% or less. 5. The granular particle used for the refrigeration chamber material particle according to claim 4, wherein the element of group 1 is at least one element selected from the group consisting of Li, Na and K. 6. The granular particle used for the refrigeration chamber material particle according to any one of claims 1 to 5, further containing a Group 2 element having a concentration of 0.001 at% or more to 60 at% or less. 7. The granular particle used for the refrigeration chamber material particle according to claim 6, wherein the group 2 element is at least one element selected from the group consisting of Mg, Ca, Sr and Ba. 8. The granular particle used for the refrigeration chamber material particle according to any one of claims 1 to 7, further containing an additive element having a concentration of 0.001 at% or more to 60 at% or less, wherein the additive element is at least one element selected from the group consisting of Mn, Al, Fe, Cu, Ni, Co, Zr, Y and B. 9. A granular particle used for a refrigeration chamber material particle according to any one of claims 1 to 8, wherein the granular particle is a gel. 10. A particle of a refrigeration chamber material obtained by sintering a granular particle used for a particle of a refrigeration chamber material according to any one of claims 1 to 9. 11. A particle of a refrigeration chamber material according to claim 10, in which the maximum value of the volumetric specific heat capacity in the temperature range from 2 K or more to 10 K or less is equal to 0.5 J/( ^cm3 ⋅K) or more. 12. A particle of a refrigeration chamber material according to claim 10 or 11, wherein the particle of the refrigeration chamber material has a particle diameter of from 50 μm or more to 5 mm or less. 13. A particle of a refrigeration chamber material according to any one of paragraphs. 10-12, which has an aspect ratio of sizes from 1 or more to 5 or less. 14. A refrigeration chamber filled with a plurality of particles of refrigeration chamber material according to any one of paragraphs 10-13. 15. A refrigerator containing a refrigeration chamber according to item 14. 16. A cryogenic vacuum pump comprising a refrigerator according to claim 15. 17. A superconducting magnet comprising a refrigerator according to claim 15. 18. A nuclear magnetic resonance imaging system comprising a refrigerator according to claim 15. 19. A nuclear magnetic resonance based installation comprising a refrigerator according to claim 15. 20. An installation for extracting single crystals with the application of a magnetic field, comprising a refrigerator according to item 15. 21. A helium recondensation device comprising a refrigerator according to claim 15.