RU2818411C1 - Cold preservation material, cold preservation material particle, granular particle, cold preservation device, refrigerator, cryopump, superconducting magnet, apparatus for imaging nuclear magnetic resonance, apparatus for nuclear magnetic resonance, apparatus for drawing monocrystal with application of magnetic field and device for re-condensation of helium - Google Patents

Abstract

FIELD: refrigerating equipment.

SUBSTANCE: application describes a material for cold preservation in one of the embodiments of the invention, which includes a rare-earth oxysulphide 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 an element of the first group in amount of 0.001 at % or more and 10 at % or less, in which the maximum value of the volumetric specific heat capacity in the temperature range from 2 to 10 K is 0.5 J/(cm³·K) or more.

EFFECT: increased volumetric specific heat and high heat conductivity of the material for preservation of cold.

19 cl, 7 dwg, 4 tbl

Description

Field of technology to which the invention relates

Embodiments of the present invention relate to a cold preservation material, a cold preservation material particle, a granular particle, a cold preservation device, a refrigerator, a cryopump, a superconducting magnet, a nuclear magnetic resonance imaging apparatus, a nuclear magnetic resonance apparatus, a single crystal pulling apparatus with an application magnetic field and a device for re-condensation of helium.

Prior Art

In recent years, there has been significant development in superconducting technology, and the development of a small, high-performance cryogenic refrigerator has become necessary as its applications have expanded. Such a cryogenic refrigerator must be lightweight, compact and have high thermal efficiency so that it can find practical applications in various fields.

The cold preservation device of a cryogenic refrigerator houses a variety of cold preservation materials. For example, cold is generated by heat exchange between the cold preservation material and helium gas passing through the cold preservation device. For example, in a superconducting MRI machine, or in a cryopump used in a semiconductor manufacturing apparatus, or the like, a refrigerator using a refrigeration cycle such as a Gifford-McMahon (GM) system, a Stirling system, or a pulse tube system is used.

In addition, a high-performance refrigerator is also necessary for the magnetic levitation train to generate magnetic force using a superconducting magnet. Moreover, in recent years, high-performance refrigerator has also been used in superconducting magnetic energy storage (SMES), single crystal magnetic field pulling apparatus to produce high-quality silicon wafers and the like. In addition, the development and practical application of the pulsed tubular refrigerator, which is expected to have high reliability, is being actively promoted.

Moreover, in the superconducting magnet, MRI machine and the like described above, the liquid helium used evaporates and helium supply becomes a problem. In recent years, the problem of helium depletion has become serious, and a complex helium availability situation has emerged, affecting the industry.

In order to reduce the consumption of liquid helium and reduce the cost of its use, such as its supply, a helium recondensation device for recondensing evaporated helium has been put into practical use, and the demand for such a helium recondensation device has increased. To liquefy helium, the helium recondenser also uses a GM refrigerator or pulse tube refrigerator, which reduces the temperature to 4K levels.

In such a refrigerator, a working fluid such as compressed helium (He) gas flows in one direction in a refrigeration device in which a cold-preserving material is housed, and thermal energy therefrom is supplied to the cold-preserving material. The expanded working fluid then flows in the opposite direction in the cold storage device and receives thermal energy from the cold storage material. Since the recovery effect in such a process is improved, the thermal efficiency in the working fluid cycle is improved, and a lower temperature can be realized.

Since the specific heat per unit volume of the cold storage material contained in the cold storage device is higher, the thermal energy that can be stored in the cold storage material is increased, so that the cooling performance of the refrigerator is improved. Therefore, on the low temperature side of the cold storage device, it is desirable to use a cold storage material having a high specific heat capacity at a low temperature, and on the high temperature side, a cold storage material having a high specific heat capacity at a high temperature.

Magnetic cold storage material has a high volumetric specific heat capacity over a certain temperature range depending on its composition. Therefore, by combining magnetic cold preservation materials having different compositions and exhibiting high volumetric specific heat in the target temperature range, it is possible to enhance and improve the cold retention ability and improve the cooling performance of the refrigerator.

In the cold preservation material used in the cold preservation device, the higher the thermal conductivity and heat transfer coefficient of the cold preservation material, the higher the thermal energy transfer efficiency, and the higher the operating efficiency of the refrigerator.

In conventional refrigerators, metal particles of cold preservation material such as lead (Pb), bismuth (Bi) and tin (Sn) are combined on the high temperature side with particles of magnetic metal-based cold preservation material such as Er ₃ Ni, ErNi and HoCu ₂ , on the low temperature side of 20 K or less to realize cooling to a temperature of 4 K.

In recent years, attempts have been made to improve the cooling performance of a refrigerator by replacing some metal-based magnetic cold preservation material particles with ceramic magnetic cold preservation material particles 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 , which have high specific heat in the temperature range from 2 K to 10 K.

As the application of the above refrigerator in various refrigeration systems is explored, further improvement in the refrigeration performance of the refrigerator is required since it is necessary to stably cool a large refrigerated object.

Citation list

Patent literature

Patent Literature 1: JP 2003-73661 A.

Patent Literature 2: JP 2003-213252 A.

Patent Literature 3: WO 2018/025581 A.

Patent Literature 4: Japan Patent No. 5010071.

Summary of the invention

The problem solved by the invention

The objective of the present invention is to create a material for maintaining cold, having a high volumetric specific heat and high thermal conductivity.

Ways to solve the problem

The cold storage material in one embodiment of the invention includes a rare earth oxysulfide 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, and an element of the first group in an amount of 0.001 atomic% or more and 10 atomic% or less, in which the maximum value of the volumetric specific heat in the temperature range of 2 K or more and 10 K or less is 0, 5 J/(cm ³ ⋅K) or more.

Brief description of drawings

In fig. 1 is a schematic cross-sectional view of the configuration of a main part of a cold storage material particle according to a second embodiment of the invention and a refrigerator according to a fourth embodiment of the invention.

In fig. 2 is a cross-sectional view illustrating a schematic configuration of a cryopump according to a fifth embodiment of the invention.

In fig. 3 is a perspective view illustrating a schematic configuration of a superconducting magnet according to a sixth embodiment of the invention.

In fig. 4 is a cross-sectional view illustrating a schematic configuration of a nuclear magnetic resonance imaging apparatus according to a seventh embodiment of the invention.

In fig. 5 is a cross-sectional view illustrating a schematic configuration of a nuclear magnetic resonance apparatus of the eighth embodiment of the invention.

In fig. 6 is a perspective view illustrating a schematic configuration of a single crystal drawing apparatus using a magnetic field in accordance with the ninth embodiment of the invention.

In fig. 7 is a diagram illustrating the configuration of a helium recondensation apparatus according to a tenth embodiment of the invention.

Embodiment(s) of the invention

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

As used herein, 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 embodiment of the invention

The cold storage material of the first embodiment includes 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 ), and an element of the first group constituting 0.001 atomic% or more and 10 atomic% or less, in which the maximum value of the volumetric specific heat in the temperature range of 2 K or more and 10 K or less is 0.5 J/(cm ³ ⋅K ) or more.

The cold storage material of the first embodiment of the invention has, for example, a volumetric specific heat of 0.5 J/(cm ³ ⋅K) or more in the temperature range of 2.5 K or more and 10 K or less. The cold storage material of the first embodiment of the invention has, for example, a volumetric specific heat of 0.55 J/(cm ³ ⋅K) or more in the temperature range of 2 K or more and 8 K or less. The cold storage material of the first embodiment of the invention has, for example, a volumetric specific heat of 0.6 J/(cm ³ ⋅K) or more in the temperature range of 4 K or more and 7 K or less.

The rare earth oxysulfide contained in the cold preservation material of the first embodiment of the invention is represented, for example, by the general formula R _{2 ± 0.1} O ₂ S _{1 ± 0.1} (where R represents 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 indicating the maximum value of the volumetric specific heat capacity differ depending on the selected rare earth element. Therefore, the specific heat capacity characteristics can be adjusted by appropriately adjusting the proportion of rare earth element.

The rare earth element is, for example, at least one rare earth element selected from the group consisting of Gd, Tb, Dy, Ho and Er. The rare earth oxysulfide contained in the cold storage material of the first embodiment may contain, for example, two or more kinds of rare earth elements.

Rare earth oxysulfide is, for example, crystalline.

The cold preservation material of the first embodiment of the invention contains a rare earth metal oxysulfide as a main component. Among the substances contained in the cold storage material of the first embodiment of the invention, for example, the volume ratio of rare earth metal oxysulfide is the largest. Among the substances contained in the cold preservation material of the first embodiment of the invention, for example, the molar ratio of rare earth metal oxysulfide is the largest.

The cold storage material of the first embodiment of the invention contains 0.001 atomic% or more and 10 atomic% or less as a whole of a Group 1 element. The first group element is at least one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and francium (Fr). The first group element is, for example, at least one element selected from the group consisting of Li, Na and K. The cold preservation material may contain, for example, two or more kinds of elements of the first group.

An element of the first group, contained in a material for maintaining cold, is present, for example, in a crystal of rare earth metal oxysulfide. The element of the first group, contained in the material for maintaining cold, is present, for example, at the crystal grain boundary of rare earth oxysulfide. The first group element contained in the cold preservation material exists, for example, on the inner surface of the wall of a void present in the cold preservation material. The element of the first group, contained in the material for maintaining cold, is present, for example, in crystalline grains of rare earth oxysulfide. The first group element contained in the cold preservation material is present, for example, in crystal grains other than rare earth oxysulfide contained in the cold preservation material.

The cold storage material of the first embodiment of the invention contains a total of, for example, 0 atomic% or more and 10 atomic% or less of a second group element in addition to the first group element. Moreover, the cold storage material of the first embodiment of the invention contains a total of, for example, 0.001 atomic% or more and 10 atomic% or less of a second group element in addition to the first group element.

The second group element is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). The element of the second group is, for example, at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba).

The cold preservation material may contain, for example, two or more types of elements of the second group. The cold preservation material may not contain the second element.

The element of the second group, contained in the material for maintaining cold, is present, for example, in a crystal of rare earth metal oxysulfide. The second group element contained in the cold preservation material is present, for example, at the crystal grain boundary of rare earth oxysulfide. The second group element contained in the storage material is present, for example, on the inner surface of the wall of a void in the cold storage material. The element of the second group, contained in the material for maintaining cold, is present, for example, in crystalline grains of rare earth oxysulfide. The second group element contained in the cold preservation material is present, for example, in crystal grains other than rare earth metal oxysulfide contained in the cold preservation material.

The cold storage material of the first embodiment of the invention contains, for example, a substance derived from a sintering aid used in the production of the cold storage material. The sintering aid is, for example, aluminum oxide (alumina), magnesium oxide, yttrium oxide, zirconium oxide or boron oxide.

The cold storage material of the first embodiment contains, for example, 0.01 atomic% or more and 20 atomic% or less of at least one element selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu) , nickel (Ni), cobalt (Co), zirconium (Zr) and boron (B). At least one element selected from the group consisting of Al, Fe, Cu, Ni, Co, Zr and B is, for example, an element obtained from a sintering aid material.

It should be noted that detecting the element contained in the cold storage material of the first embodiment of the invention and measuring the atomic concentration of the element can also be performed, for example, by dissolving the cold storage material in a liquid and using inductively coupled plasma (ICP) atomic emission spectroscopy AES). Energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray spectroscopy (WDX) can also be used.

The crystal structure of the rare earth oxysulfide contained in the cold storage material of the first embodiment, for example, is of the type Ce ₂ O ₂ S, and its space group is P 3m. The crystal structure can be confirmed by measuring X-ray diffraction of the powder, observing an electron backscatter diffraction image with a scanning electron microscope, observing with a transmission electron microscope, or the like.

The method for producing the cold preservation material of the first embodiment is not particularly limited, but, for example, the cold preservation material can be obtained by mixing raw material powders using a ball mill or the like to obtain a raw material mixture, and molding and sintering the resulting raw material mixture. Rare earth metal oxide or rare earth metal oxysulfide can be used as raw material powder. The type and ratio of rare earth oxide or rare earth oxysulfide are adjusted according to the target cold preservation material composition.

When using a carbonate containing an element of the first group, an oxide containing an element of the first group, a nitride containing an element of the first group, or a carbide containing an element of the first group in the raw material powder, the element of the first group may be included in the material for maintaining cold. When using a carbonate containing an element of the second group, an oxide containing an element of the second group, a nitride containing an element of the second group, or a carbide containing an element of the second group in the raw material powder, the element of the second group may be included in the material for maintaining cold.

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

When rare earth oxide is used as the raw material powder, the molded body is subjected to sulfonation. In this case, heat treatment is carried out in a sulfurization atmosphere. The sulfurization atmosphere is, for example, a gas containing a sulfur atom with a negative oxidation number, such as hydrogen sulfide (H ₂ S), carbon sulfide (CS ₂ ) or methanethiol (CH ₃ SH). The heat treatment temperature is, for example, 400°C or more and 700°C or less. The heat treatment time is, for example, 1 hour or more and 8 hours or less.

Heat treatment for sintering the resulting oxysulfide is carried out, for example, in an atmosphere of inert gas under pressure. The heat treatment temperature is, for example, 1000°C or more and 2000°C or less. The heat treatment temperature is, for example, 1100°C or more and 1700°C or less. The heat treatment time is, for example, 1 hour or more and 48 hours or less.

The cold storage material of the first embodiment of the invention may be, for example, a sintered body of cold storage material particles made from the first cold storage material.

Next, the functions and effects of the cold storage material of the first embodiment of the invention will be described.

In a cryogenic refrigerator used for cooling a superconducting device or the like, a cold storage material is placed in the cold storage device. For example, cold is generated by heat exchange between the cold preservation material and helium gas passing through the cold preservation device. In order to improve the cooling performance of a refrigerator, the cold preservation material housed in the cold preservation device must have excellent characteristics such as high specific heat capacity and high thermal conductivity.

The upper limit of volumetric specific heat capacity is limited by the composition of the substance. Therefore, it is difficult to significantly improve the volumetric specific heat capacity. Meanwhile, thermal conductivity can be improved by increasing crystallinity and reducing voids.

In the cold storage material of the first embodiment of the invention, the maximum value of the volumetric specific heat in the temperature range of 2 K or more and 10 K or less is 0.5 J/(cm ³ ⋅K) or more. Thus, the cold storage material of the first embodiment of the invention has a high volumetric specific heat capacity.

The cold storage material of the first embodiment of the invention has, for example, a volumetric specific heat capacity of 0.5 J/(cm ³ ⋅K) or more in the temperature range of 2.5 K or more and 10 K or less. In this case, for example, the volumetric specific heat capacity in the temperature range of 2 K or more and 8 K or less is 0.55 J/(cm ³ ⋅K) or more, and in the temperature range of 4 K or more and 7 K or less is 0 .6 J/(cm ³ ⋅K) or more.

As described above, since the cold storage material of the first embodiment of the invention has a high volumetric specific heat, the cold storage device containing the cold storage material of the first embodiment has high cold retention performance. The refrigerator including the cold preservation device in which the cold preservation material of the first embodiment of the invention is housed has a high cooling capacity.

In addition, the cold storage material of the first embodiment contains an element of the first group in an atomic concentration of 0.001 atomic% or more and 10 atomic% or less. The first group element has the function of promoting sintering of the molded body and reducing the amount of voids in the resulting sintered body during the sintering step when the cold preservation material is produced. Therefore, the cold storage material of the first embodiment of the invention has a high degree of sintering and high thermal conductivity.

In order to sufficiently obtain the characteristics required for a cold preservation material, such as thermal conductivity and volumetric specific heat, sufficient sintering temperature and sintering time are required in the sintering process. The cold preservation material of the first embodiment can reduce the sintering temperature required for sintering and shorten the sintering time through the sintering promotion function of the first group member. In this way, the manufacturing cost of the cold preservation material can be reduced and an inexpensive cold preservation material can be obtained.

When the atomic concentration of a Group 1 element in the cold preservation material is 0.001 atomic% or more, the degree of sintering increases and the number of extremely fine voids decreases. Therefore, the thermal conductivity of the cold preservation material may increase.

When the atomic concentration of a group 1 element in a cold preservation material exceeds 10 atomic%, a sulfide containing a rare earth element and a group 1 element is formed, so that the volumetric specific heat is reduced and the thermal conductivity is reduced. When the atomic concentration of the first group element in the cold storage material is 10 atomic% or less, the volumetric specific heat is high and thermal conductivity can be increased, and the cooling performance of the refrigerator containing the cold storage material of the first embodiment of the invention is improved.

The first group element contained in the material of the first embodiment of the invention is, for example, at least one element selected from the group consisting of Li, Na, K, Rb, Cs and Fr. The element of the first group is preferably at least one element selected from the group consisting of Li, Na and K. For example, two or more kinds of elements of the first group may be included in the cold preservation material.

The cold preservation material containing the first group element can be obtained by using a carbonate, oxide, nitride or carbide containing the first group element in the raw material powder. The concentration of the Group 1 element in the cold preservation material is controlled by adjusting the amount of carbonate, oxide, nitride or carbide containing the Group 1 element.

The cold storage material of the first embodiment of the invention contains a total of, for example, 0 atomic% or more and 10 atomic% or less of the atomic concentration of a second group element. In this case, for example, the element of the second group is contained in a total amount of 0.001 atomic% or more and 10 atomic% or less in terms of atomic concentration. The second group element is at least one element selected from the group consisting of Be, Mg, Ca, Sr, Ba and Ra. The atomic concentration of the second group element is, for example, 0.001 atomic % or more and 5 atomic % or less overall. The cold preservation material may contain, for example, two or more types of elements of the second group.

In the cold storage material of the first embodiment, the second group element is contained in an amount of 0.001 atomic % or more in addition to the first group element, thereby further improving sinterability and reducing the amount of extremely fine voids. This further improves thermal conductivity. The element of the second group does not have specific thermal characteristics. Therefore, when the content of the second group element exceeds a total of 10 atomic%, the volumetric specific heat of the cold storage material decreases, the performance of the cold storage device decreases, and the cooling capacity of the refrigerator decreases.

By using a carbonate, oxide, nitride or carbide containing an element of the second group in the raw material powder, it is possible to obtain a cold preservation material containing an element of the second group. The concentration of the Group 2 element contained in the cold preservation material is controlled by adjusting the amount of carbonate, oxide, nitride or carbide containing the Group 2 element.

When the cold preservation material of the first embodiment of the invention is manufactured by adding 0.01 atomic% or more of a sintering aid in the form of a metal or a metalloid element forming a sintering aid in addition to the element of the first group, the sintering ability is further improved and the amount is extremely small voids are reduced. This further improves thermal conductivity. The metal or metalloid element forming the sintering aid does not have good specific heat capacity. Therefore, when the amount of added metal or metalloid element constituting the sintering aid exceeds 20 atomic%, the volumetric specific heat of the cold preservation material decreases, the performance of the cold preservation device decreases, and the cooling capacity of the refrigerator decreases.

The cold storage material of the first embodiment preferably contains 0.01 atomic% or more and 20 atomic% or less of at least one element selected from the group consisting of aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), cobalt (Co), zirconium (Zr) and boron (B). At least one element selected from the group consisting of Al, Fe, Cu, Ni, Co, Zr and B is, for example, an element obtained from a sintering aid material. At least one element selected from the group consisting of Al, Fe, Cu, Ni, Co, Zr and B is, for example, an example of a metal or metalloid element constituting the sintering aid.

As described above, according to the first embodiment of the invention, a cold storage material having excellent characteristics such as high volumetric specific heat capacity and high thermal conductivity can be realized.

Second embodiment of the invention

The particle of the cold storage material of the second embodiment of the invention is formed from the cold storage material of the first embodiment and has a size of 50 μm or more and 3 mm or less. The aspect ratio of the cold preservation material particle is, for example, 1 or more and 5 or less. The aspect ratio of a cold storage material particle is the ratio of the major axis of the cold storage material particle to its minor axis. The particle shape of the cold preservation material is, for example, spherical.

Hereinafter, the description of contents identical to the first embodiment of the invention may be partially omitted.

The particle size of the cold storage material is the equivalent diameter of a circle. The equivalent circle diameter 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 size of the cold storage material can be determined, for example, by analyzing an image obtained using an optical microscope or an SEM image.

The method for producing the cold preservation material particle of the second embodiment of the invention is not particularly limited, but, for example, the cold preservation material particle can be obtained by mixing raw material powders using a ball mill or the like to obtain a raw material mixture, molding (granulating) the resulting raw material mixture into particles by a tumbling granulation method, a stir granulation method, an extrusion method, a sputtering method, a compression molding method or the like, and then sintering the resulting granular molded body.

The resulting granular molded body is called granular particles.

In the granulation method, the strength of the granular particles is improved by adding a binder to adhere the raw material powder particles to each other. The binder is, for example, polyvinyl alcohol, polyvinyl butyral, carboxymethylcellulose, acrylic resin or polyethylene glycol. The amount of the binder added is, for example, 0.01 mass% or more and 20 mass% or less.

Rare earth metal oxide or rare earth metal oxysulfide can be used as raw material powder. The type and ratio of rare earth oxide or rare earth oxysulfide are adjusted according to the target particle composition of the cold preservation material.

The cold storage material particles containing the first group element can be produced by using a carbonate containing the first group element, an oxide containing the first group element, a nitride containing the first group element, or a carbide containing the first group element in the raw material powder. In addition, the cold preservation material particles containing a group 2 element can be prepared by using a carbonate containing a group 2 element, an oxide containing a group 2 element, a nitride containing a group 2 element or a carbide containing a group 2 element in powder. raw materials.

By adding a sintering aid to the raw material powder, cold preservation material particles containing the sintering aid can be obtained. When the sintering aid and the rare earth oxide raw material react with each other, an oxide phase containing a rare earth element and a metal or metalloid element constituting the sintering aid can be formed.

In addition, the suspension prepared by adding the raw material powder to the alginic acid aqueous solution and mixing the raw material powder with the alginic acid aqueous solution can be added dropwise to the gelling solution, and the suspension can be gelled to granulate the suspension into particles. This method of particle granulation is a method of causing gelation as a result of a cross-linking reaction with polyvalent metal ions contained in the gelling solution. Therefore, the strength of granular particles, that is, the gelling strength, depends on the amount of alginate contained in the particles.

The amount of alginate contained in the particles can be changed depending on the concentration of alginate contained in the alginic acid aqueous solution or the ratio between the alginic acid aqueous solution and the raw material powder. To instill the suspension into the gelling solution, you can use, for example, a dropper, burette, pipette, syringe, dispenser, jet device or the like. Hereinafter, the method of granulating particles using this method is called the method of obtaining a gel using alginic acid.

In the alginic acid gelling process, the particle size and aspect ratio of the particles can be changed by adjusting the viscosity of the suspension, the diameter of the outlet at the time of dripping, or the distance between the tip of the outlet and the surface level of the gelling solution. The outlet diameter is, for example, 50 μm or more and 3000 μm or less. The viscosity of the suspension is, for example, 0.1 mPa.s or more and 1,000,000 mPa.s or less. The distance between the tip of the outlet and the surface level of the gelling solution is, for example, 0.1 mm or more and 1000 mm or less.

If a dispenser is used for dosing, it can be any type of dispenser from a pneumatic pulse dispenser, a plunger dispenser and a piezo dispenser.

Based on their mode of operation, jet devices are generally divided into continuous dispensers and demand dispensers, and in this case any type of dispenser can be used. Further, the type of demand-actuated dispensers are divided into three types: piezo type, thermal type and valve type, and any type of dispenser can be used in this case.

The suspension to be gelled, dropped into the gelling solution using a dropper, burette, pipette, syringe, dispenser, jet device, or the like, is kept in the gelling solution. As a result of gelation of the suspension, granular particles are formed containing raw material powder to maintain cold.

The residence time of the suspension in the gelling solution is, for example, 10 minutes or more and 48 hours or less. When the gelation time is short, gelation does not proceed sufficiently so that the strength of the granular particles is less than the strength expected from the amount of alginate.

The alginic acid aqueous solution used in the method for producing alginic acid gel is, for example, a sodium alginate aqueous solution, an ammonium alginate aqueous solution or a potassium alginate aqueous solution. When using an aqueous solution of sodium alginate or an aqueous solution of potassium alginate containing an element of the first group, sodium or potassium may be contained in the particles of the material to maintain cold. Sodium and potassium can be contained simultaneously by using a mixed aqueous solution consisting of an aqueous solution of sodium alginate and an aqueous solution of potassium alginate in suspension.

The concentration of the group 1 element contained in the particle is controlled by adjusting the concentration of the alginate containing the group 1 element. For example, the concentration of alginate in the alginate aqueous solution is 0.01 mass% or more and 5 mass% or less. When the concentration of the alginate aqueous solution is lower than 0.01 mass%, a gel having sufficient strength cannot be formed and particles cannot be obtained.

As an aqueous solution containing an element of the second group, 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 barium chloride or an aqueous solution of barium hydroxide.

When using aqueous calcium lactate, aqueous calcium chloride, aqueous magnesium sulfate, aqueous beryllium sulfate, aqueous strontium nitrate, aqueous barium chloride and aqueous barium hydroxide in the gelling solution, calcium, magnesium, beryllium, strontium and barium may contained in particles of material to preserve cold.

When using aqueous aluminum chloride, aqueous aluminum nitrate, aqueous aluminum lactate, aqueous ferric (II) chloride, aqueous ferric (III) chloride, aqueous copper (II) chloride, aqueous nickel (II) chloride or aqueous cobalt(II) chloride solution as a gelling solution, aluminum, iron, copper, nickel or cobalt may be contained in the cold preservation material particles as a sintering aid.

Since gelation occurs as a result of the cross-linking reaction of polyvalent metal ions contained in the gelling solution, when an aqueous solution containing an element of the first group is used as a suspension, and an aqueous solution containing an element of the second group is used as a gelling solution, the amount of the element of the first group and element of the second group contained in the particles can be adjusted by adjusting the immersion time of the particles, which are added dropwise to the gelling solution and granulated in the gelling solution.

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 magnesium sulfate, an aqueous solution of beryllium sulfate, an aqueous solution of strontium nitrate, an aqueous solution of barium chloride and aqueous barium hydroxide solution are mixed and used as a gelling solution, thus two or more kinds of elements of the second group can be contained in the particles of the cold preservation material.

The size of the granular particles is, for example, 70 μm or more and 5 mm or less. The aspect ratio of the granular particles is, for example, 1 or more and 5 or less.

By defatting granular particles, a certain amount of organic components can be removed. In the case where the raw material is an oxide, if degreasing is insufficient, the sulfonation process does not occur sufficiently, and the required amount of oxysulfide cannot be obtained. In addition, when degreasing is insufficient and too much organic component remains, the density of the sintered particles decreases. Therefore, the strength of the cold preservation material particle becomes small, and the cold preservation material particle cannot withstand use in the refrigerator.

When defatting continues for too long, the organic component that provides strength disappears, so that the strength of the granular particles after defatting is reduced and the particles crack or chip. The degreasing temperature is, for example, 400°C or more and 800°C or less, and the time is 30 minutes or more and 12 hours or less.

When rare earth oxide is used as the raw material powder, the granular particles are subjected to sulfonation. In this case, heat treatment is carried out in a sulfurization atmosphere. The sulfurization atmosphere contains, for example, a gas containing a sulfur atom with a negative oxidation number, such as hydrogen sulfide (H ₂ S), carbon sulfide (CS ₂ ) or methanethiol (CH ₃ SH). The heat treatment temperature is, for example, 400°C or more and 700°C or less. The heat treatment time is, for example, 1 hour or more and 8 hours or less.

The heat treatment for sintering the oxysulfide particles is carried out, for example, in an inert gas atmosphere under pressure. The heat treatment temperature is, for example, 1000°C or more and 2000°C or less. The heat treatment temperature is, for example, 1100°C or more and 1700°C or less. The heat treatment time is, for example, 1 hour or more and 48 hours or less.

Next, the functions and effects of the cold preservation material particle of the second embodiment of the invention will be described.

The particle of the cold storage material of the second embodiment is made from the cold storage material of the first embodiment and has a size of 50 μm or more and 3 mm or less. The aspect ratio of the cold preservation material particle is, for example, 1 or more and 5 or less. The aspect ratio of a cold preservation material particle is the ratio of its major axis to its minor axis. The particle shape of the cold preservation material is, for example, spherical.

In the cold storage material particle of the second embodiment, the maximum value of the volumetric specific heat in the temperature range of 2 K or more and 10 K or less is 0.5 J/(cm ³ ⋅K) or more. Thus, the cold storage material particle of the second embodiment has a high volumetric specific heat capacity. Since the cold storage material particle of the second embodiment has a high volumetric specific heat, the cold storage device using the cold storage material particle of the second embodiment has high refrigeration capacity. Moreover, the refrigerator including the cold preservation device using the cold preservation material particle of the second embodiment has high cooling capacity.

In addition, the cold storage material particle of the second embodiment contains an element of the first group in an atomic concentration of 0.001 atomic% or more and 10 atomic% or less. The element of the first group has the function of promoting sintering of the cold preservation material particle and reducing the amount of voids contained in the cold preservation material particle during sintering when producing the cold preservation material particle. Thus, the cold preservation material particle has a high degree of sintering and high thermal conductivity.

In the cold preservation material of the first embodiment of the invention, the sinterability is further improved by adding 0.01 atomic% or more of a sintering aid in the form of a metal or a metalloid element forming a sintering aid in addition to the element of the first group, and an amount of extremely fine voids decreases. This further improves thermal conductivity. The metal or metalloid element forming the sintering aid does not have good specific heat capacity. Therefore, when the amount of added metal or metalloid element forming the sintering aid exceeds 20 atomic%, the volumetric specific heat of the cold preservation material decreases, the performance of the cold preservation device decreases, and the cooling capacity of the refrigerator decreases.

In order to sufficiently obtain the properties required for cold retention material particles, such as thermal conductivity and volumetric specific heat, the sintering process requires sufficient sintering temperature and sufficient sintering time. The cold preservation material particle of the second embodiment can reduce the sintering temperature required for sintering and shorten the sintering time through the sintering promotion function of the element of the first group. Thus, it is possible to reduce the cost of manufacturing a cold storage material particle and obtain an inexpensive cold storage material particle.

The particle size of the cold preservation material according to the second embodiment of the invention is 50 μm or more and 3 mm or less. More preferably, the particle size of the cold preservation material is 1 mm or less, and even more preferably 500 μm or less.

When the particle size of the cold preservation material exceeds the above lower limit value, the packing density of the particles of the cold preservation material in the cold preservation device is reduced, the pressure loss of the working medium such as helium is reduced, and the refrigeration performance of the refrigerator is improved. Meanwhile, when the particle size of the cold preservation material is smaller than the above upper limit value, the distance from the surface of the cold preservation material particle to its center is shortened, the heat of the working medium is easily transferred to the center of the cold preservation material particle, and the refrigeration performance of the refrigerator are improving.

The aspect ratio of the cold preservation material particles is preferably 1 or more and 5 or less, and more preferably 1 or more and 2 or less. When the aspect ratio of the particles of the cold storage material is smaller than the above-mentioned upper limit value, the gaps when filling the cold storage device with the particles of the cold storage material become uniform, and the cooling performance of the refrigerator is improved.

The cold preservation material particle of the second embodiment of the invention cracks or chips during processing if the strength of the defatted granular particle is below a certain level. When a refrigerator uses particles of cold preservation material that deviate from the spherical shape, the cooling performance of the refrigerator is reduced, and therefore granular particles that are cracked or chipped are rejected as a defective product. For this reason, it is desirable that the granular particles have a specified level of strength or greater at which cracking or chipping does not occur.

The strength of granular particles mainly depends on the amount of binder or the amount of alginate, but when the amount of these organic components is too large, sulfurization or sintering becomes difficult. Meanwhile, the element of the first group promotes sintering of material particles to maintain cold. When the granular particles contain an element of the first group in an atomic concentration of 0.001 atomic% or more and 10 atomic% or less and further contain a binder or a carbon component derived from alginate in an amount of 0.01 mass% or more and 20 mass% or less , due to the above two effects, both sinterability and high strength can be achieved.

The content of the carbon component is more preferably 10 mass% or less, even more preferably 5 mass% or less. Even when the first group element is contained in an atomic concentration of 0.001 atomic% or more and 10 atomic% or less, if the carbon component exceeds 20 mass%, it is difficult to properly remove the organic component, or the molding density after degreasing is significantly reduced, and the sintering reaction does not occurs even at high sintering temperatures. For this reason, the strength of the sintered particles is very low, and it is difficult to remove the sintered particles in particulate form. When the amount of the carbon component is less than 0.01 mass%, the amount of binder or sodium alginate contained in the granular particles is small, so the strength is weakened, and cracking or chipping occurs when the granular particles are handled.

In defatted granular particles, when the element of the first group is contained in an atomic concentration of 0.001 atomic% or more and 10 atomic% or less, and the binder or carbon component derived from alginate is contained in an amount of 0.001 mass% or more and 10 mass% or However, both sinterability and high strength can be ensured. More preferably, the content of the carbon component is 5 mass% or less, even more preferably 3 mass% or less. When the carbon component is contained in an amount of more than 10 mass%, since the molding density is low, the density is not increased even after sintering, and the strength that allows the particles to be used in a refrigerator is not achieved. When an attempt is made to improve the post-sintering density by increasing the sintering temperature, the particles stick to each other and the aspect ratio decreases markedly.

In view of shrinkage due to sintering, it is desirable that the granular particle size before and after degreasing is 70 µm or more and 5 mm or less. The aspect ratio of granular particles before and after degreasing is, for example, 1 or more and 5 or less.

As described above, according to the second embodiment of the invention, it is possible to realize a cold storage material particle having excellent characteristics such as high volumetric specific heat capacity and high thermal conductivity.

Third embodiment of the invention

The cold storage device of the third embodiment of the invention is a cold storage device filled with a plurality of particles of the cold storage material of the second embodiment. In the cold preservation device of the third embodiment, for example, the ratio of particles of the cold preservation material of the second embodiment having a roundness R represented by the formula 4πA/L ² less than or equal to 0.5 is 5% or less. "L" represents the perimeter of each projection image of the cold preservation material particles, and "A" represents the actual area of the projection image in the formula.

The roundness R can be obtained by processing images of the shapes of multiple particles of the cold preservation material using an optical microscope. A particle of cold preservation material having a roundness R of 0.5 or less is shaped, for example, having irregularities on the surface. When a plurality of cold storage material particles containing such cold storage material particles in an amount of more than 5% fills the cold storage device, the porosity of the material formed by the cold storage particles in the cold storage device becomes uneven and the filling property becomes unstable. . Therefore, when the working medium enters inside, the cooling capacity of the refrigerator decreases or the particles of the cold preservation material move or break due to the stress applied to the particles of the cold preservation material while the cold preservation device is filled with particles of the cold preservation material or during operation of the refrigerator , and small particles are formed that clog the gaps, resulting in clogged gaps, reducing the cooling performance and long-term reliability of the refrigerator. The cold storage material particles having a roundness R of 0.5 or less are preferably 2% or less, more preferably 0%.

Fourth Embodiment

The refrigerator of the fourth embodiment of the invention is a refrigerator including a cold storage device filled with the cold storage material of the first embodiment or a plurality of particles of the cold storage material of the second embodiment. Hereinafter, description of contents identical to the first embodiment, the second embodiment and the third embodiment will be partially omitted.

In fig. 1 is a schematic cross-sectional view illustrating the configuration of a main body of a refrigerator of the fourth embodiment including the cold storage device of the third embodiment filled with a plurality of particles of the cold storage material of the second embodiment. The refrigerator of the fourth embodiment is a two-stage cryogenic cold storage refrigerator 100 used for cooling a superconducting device or the like.

The cryogenic cold preservation refrigerator 100 includes a first cylinder 111, a second cylinder 112, a vacuum container 113, a first cold preservation device 114, a second cold preservation device 115, a first O-ring 116, a second O-ring 117, a first cold preservation material. 118, a second cold storage material 119, 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 cold storage refrigerator 100 includes a vacuum container 113 in which a first large diameter cylinder 111 and a second small diameter cylinder 112 are mounted coaxially connected to the first cylinder 111. The first cold storage device 114 is reciprocatably mounted in the first cylinder 111. In the second cylinder 112, a second cold storage device 115 is reciprocatably mounted, which is an example of the cold storage device of the third embodiment of the invention.

The first O-ring 116 is located between the first cylinder 111 and the first cold retaining device 114. A second O-ring 117 is located between the second cylinder 112 and the second cold retaining device 115.

The first cold storage device 114 includes a first cold storage material 118, such as a copper mesh. The second cold storage device 115 accommodates the second cold storage material 119.

The first cold storage device 114 and the second cold storage device 115 have a working fluid passage provided in the space between the first cold storage material 118 and the second cold storage material 119. The working medium is helium gas.

The first expansion chamber 120 is provided between the first cold storage device 114 and the second cold storage device 115. A second expansion chamber 121 is provided between the second cold storage device 115 and the distal end wall of the second cylinder 112. A first cooling stage 122 is provided at the bottom of the first expansion chamber 120. A second cooling stage 123 having a temperature lower than the temperature of the first cooling stage 122 is formed on the bottom of the second expansion chamber 121.

A high-pressure working fluid is supplied from the compressor 124 to the above-described two-stage cryogenic refrigerator 100. The supplied working fluid passes between the first cold storage materials 118 housed in the first cold storage device 114 and reaches the first expansion chamber 120. Then, the refrigerant passes between the second cold preservation materials 119 disposed in the second cold preservation device 115 and reaches the second expansion chamber 121.

At this time, the working medium is cooled by transferring thermal energy to the first cold storage material 118 and the second cold storage material 119. The working medium passing between the first cold storage material 118 and the second cold storage material 119 expands in the first expansion chamber 120 and the second expansion chamber 121 to generate cold. As a result, the first cooling stage 122 and the second cooling stage 123 are cooled.

The expanded working fluid flows in the reverse direction between the first cold storage material 118 and the second cold storage material 119. The working fluid is withdrawn after receiving thermal energy from the first cold storage material 118 and the second cold storage material 119. The cryogenic cold storage refrigerator 100 is configured such that the thermal efficiency of the working fluid cycle is improved because in such a process the recovery effect is improved and a lower temperature is realized.

The cold storage device included in the refrigerator of the fourth embodiment of the invention includes the cold storage material of the first embodiment in the second cold storage device 115 as at least a part of the second cold storage material 119. The second cold storage device 115 may be filled with a plurality of particles of the cold storage material of the second embodiment as at least a portion of the second cold storage material 119. It is preferable that in the plurality of particles of the cold preservation material of the second embodiment, the ratio of particles having a roundness R represented by the formula 4πA/L ² less than or equal to 0.5 is 5% or less. "L" represents the perimeter of each projection image of the cold preservation material particles, and "A" represents the actual area of the projection image in the formula.

In the fourth embodiment of the invention, the cold storage device of the third embodiment may include, for example, a plurality of fill layers of different types of cold storage materials. Different types of cold storage materials can be separated by mesh. The mesh is, for example, a metal mesh. At least one of the plurality of core layers of cold storage materials is a cold storage material of the first embodiment or a particle of a cold storage material of the second embodiment. In the refrigerator of the fourth embodiment, for example, the cold storage material of the first embodiment or a plurality of particles of the cold storage material of the second embodiment fills the cold storage device on the low temperature side.

To improve the refrigerating capacity of a refrigerator, it is desirable to improve the specific heat capacity per unit volume of cold preservation material and improve thermal conductivity. The refrigerator of the fourth embodiment of the invention includes a cold preservation material or particles of a cold preservation material that maintain volumetric specific heat capacity and have improved thermal conductivity.

For example, by using the refrigerator of the fourth embodiment in the magnetic levitation train, the long-term reliability of the magnetic levitation train can be improved.

As described above, according to the fourth embodiment of the invention, a refrigerator with excellent performance can be realized by using a cold preservation material or particles of a cold preservation material with excellent performance.

Fifth embodiment of the invention

The cryopump according to the fifth embodiment of the invention includes a refrigerator of the fourth embodiment. Hereinafter, description of contents identical to the fourth embodiment will be partially omitted.

In fig. 2 is a cross-sectional view illustrating a schematic configuration of a cryopump according to a fifth embodiment of the invention. The cryopump according to the fifth embodiment is a cryopump 500 including a cryogenic refrigerator 100 for keeping cold according to the fourth embodiment.

The cryopump 500 includes a cryopanel 501 that condenses or adsorbs gas molecules, a cryogenic cooler 100 that cools the cryopanel 501 to a predetermined cryogenic temperature, a screen 503 provided between the cryopanel 501 and the cryogenic cooler 100, a baffle 504, provided at the inlet port, and a ring 505 that changes the release rate of argon, nitrogen, hydrogen or the like.

According to a fifth embodiment of the invention, a cryopump having excellent performance can be realized by using a refrigerator having excellent performance. By using a cryopump in the semiconductor manufacturing apparatus according to the fifth embodiment of the invention, the reliability of the semiconductor manufacturing apparatus in the long term can be improved.

Sixth embodiment of the invention

The superconducting magnet of the sixth embodiment includes a refrigerator of the fourth embodiment. Hereinafter, description of contents duplicating the fourth embodiment will be partially omitted.

In fig. 3 is a perspective view illustrating a schematic configuration of a superconducting magnet according to a sixth embodiment of the invention. The superconducting magnet of the sixth embodiment is, for example, a superconducting magnet 600 for a magnetic levitation train including a cryogenic cold storage refrigerator 100 of the fourth embodiment.

The superconducting magnet 600 for magnetic levitation train includes a superconducting coil 601, a liquid helium tank 602 for cooling the superconducting coil 601, a liquid nitrogen tank 603 to prevent liquid helium from evaporating, a laminated heat insulating material 605, a power wire 606, a DC switch 607 and a cryogenic refrigerator 100 to keep things cold.

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

Seventh Embodiment

The nuclear magnetic resonance imaging apparatus of the seventh embodiment includes a refrigerator of the fourth embodiment. Hereinafter, description of contents identical to the fourth embodiment will be partially omitted.

In fig. 4 is a cross-sectional view illustrating a schematic configuration of a nuclear magnetic resonance imaging apparatus of the seventh embodiment of the invention. The nuclear magnetic resonance imaging (MRI) apparatus of the seventh embodiment is a nuclear magnetic resonance imaging apparatus 700 including a cryogenic refrigerator 100 for keeping cold in the fourth embodiment.

The nuclear magnetic resonance imaging apparatus 700 includes a superconducting static magnetic field coil 701 that applies a spatially uniform and temporally stable static magnetic field to the human body, a correction coil (not shown) that corrects the inhomogeneity of the generated magnetic field, a gradient coil 702 magnetic field that creates a magnetic field gradient in the measurement area, a probe 703 for transmitting/receiving radio waves, a cryostat 705, and a radiation adiabatic screen 706. The cryogenic cold storage refrigerator 100 is used to cool the superconducting static magnetic field coil 701.

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

Eighth Embodiment

The nuclear magnetic resonance apparatus of the eighth embodiment of the invention includes a refrigerator of the fourth embodiment. Hereinafter, description of contents identical to the fourth embodiment will be partially omitted.

In fig. 5 is a cross-sectional view illustrating a schematic configuration of a nuclear magnetic resonance apparatus of the eighth embodiment of the invention. The nuclear magnetic resonance (NMR) apparatus of the eighth embodiment is a nuclear magnetic resonance apparatus 800 including a cryogenic refrigerator 100 for keeping cold in the fourth embodiment.

The nuclear magnetic resonance apparatus 800 includes a superconducting static magnetic field coil 802 that applies a magnetic field to a sample, such as an organic matter, placed in a test tube 801, a high-frequency generator 803 that applies a radio wave to the test tube 801 in a magnetic field, and an amplifier 804, which amplifies the induced current generated in a coil (not shown) around the test tube 801. In addition, a cryogenic cold storage refrigerator 100 is provided that cools the superconducting static magnetic field coil 802.

According to the eighth embodiment of the invention, a nuclear magnetic resonance apparatus with excellent performance can be realized using a refrigerator with excellent performance.

Ninth embodiment of the invention

The magnetic field-applied single crystal drawing apparatus of the ninth embodiment includes a refrigerator of the fourth embodiment. Hereinafter, description of contents duplicating the fourth embodiment will be partially omitted.

In fig. 6 is a perspective view illustrating a schematic configuration of a single crystal drawing apparatus applying a magnetic field according to the ninth embodiment of the embodiment. The magnetic field-applied single crystal drawing apparatus of the ninth embodiment is a magnetic field-applied single crystal drawing apparatus 900 including the cryogenic refrigerator 100 of the fourth embodiment.

The apparatus 900 for drawing single crystals with the application of a magnetic field includes a unit 901 for drawing single crystals having a crucible for melting raw materials, a heater, a mechanism for drawing single crystals and the like, a superconducting coil 902 that applies a static magnetic field to the molten raw materials, a lifting mechanism 903 of the unit 901 drawing monocrystals, current lead 905, heat shield plate 906 and container 907 for helium. To cool the superconducting coil 902, a cryogenic refrigerator 100 is used to keep it cold.

According to a ninth embodiment of the invention, a magnetic field-applied single crystal drawing apparatus having excellent characteristics can be realized by using a refrigerator having excellent characteristics.

Tenth embodiment of the invention

The helium recondensation apparatus of the tenth embodiment includes a refrigerator of the fourth embodiment. Hereinafter, description of contents identical to the fourth embodiment will be partially omitted.

In fig. 7 is a schematic diagram showing a configuration of a helium recondensation apparatus according to a tenth embodiment of the invention. The helium recondensation device according to the tenth embodiment is a helium recondensation device 1000 including the cold storage cryogenic refrigerator 100 of the fourth embodiment.

The helium recondensation apparatus 1000 includes a cryogenic refrigerator 100 for maintaining cold, an evaporator pipe 1001 and a liquefaction pipe 1002.

The helium recondensation device 1000 can recondense helium gas evaporated from the liquid helium device included in the liquid helium using device into liquid helium. The device using liquid helium may be a superconducting magnet, a nuclear magnetic resonance (NMR) device, a nuclear magnetic resonance imaging (MRI) device, a physical properties measurement system (PPMS), or a device using a superconducting magnet such as a magnetic properties measurement system.

Helium gas is introduced from a liquid helium device (not shown) into a helium recondensation device 1000 through an evaporator tube 1001. The helium gas is cooled to a temperature of 4 K, equal to or below the helium liquefaction temperature, in a cryogenic refrigerator 100 to maintain cold. The condensed and liquefied liquid helium passes through the liquefaction pipe 1002 and is returned to the liquid helium device.

According to a tenth embodiment of the invention, a helium recondensation device having excellent characteristics can be realized by using a refrigerator having excellent characteristics.

Examples

Next, Examples, Comparative Examples and evaluation results of the cold storage material of the first embodiment and the cold storage material particles of the second embodiment will be described.

Example 1

Gd ₂ O ₃ powder and Na ₂ CO ₃ powder were mixed and ground in a ball mill for 24 hours to obtain a raw material mixture. The resulting raw material mixture was then dried and granulated using a granulator to obtain granular particles ranging in size from 0.3 mm to 0.5 mm. In this case, polyvinyl alcohol was used as a binder, which was added in an amount of 1.2 wt.% relative to the raw material powder. The sodium concentration in the granular particles was 0.52 atom% and the carbon concentration was 0.99 wt%. The resulting raw material mixture was molded to obtain a molded body.

In order to evaluate the strength of granular particles, a cylindrical container with a diameter of 15 mm and a height of 5 mm was filled with granular particles. In this case, the cylindrical container was filled with cold preservation materials in an amount sufficient to ensure that the granular particles were fixed in the cylindrical container and could not move freely. A single vibration with an amplitude of 2 mm and a maximum acceleration of 200 m/s ² was applied to the container 1×10 ³ times. As a result, the amount of destroyed cold storage material was less than 0.1 mass%.

The granular particles and the molded body were degreased at 600°C for 6 hours in an air atmosphere. The defatted granular particles and molded body had a sodium concentration of 0.54 atom% and a carbon concentration of 0.51 wt%. Heat treatment was carried out at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (H ₂ S) to sulfurize the particles and the molded body. Heat treatment was carried out at 1300°C for 12 hours under an inert gas atmosphere under pressure to sinter the particles and the molded body.

The main constituents of the cold storage material and the cold storage material particles of Example 1 are gadolinium oxysulfide. The sodium concentration of the cold storage material and the particles of the cold storage material of Example 1 was 0.55 atomic percent.

The maximum value of volumetric specific heat at 10 K or less and thermal conductivity at 4.2 K of the cold storage material of Example 1 were measured. The measurement was carried out using a physical properties measurement system (PPMS).

250 g of the cold preservation material particles of Example 1 were poured into the low temperature side of the second stage of the cold preservation apparatus of the GM two-stage refrigerator shown in FIG. 1, and 250 g of Pb cold preservation material was poured into the high temperature side, assembled the refrigerator according to Example 1, and conducted a cooling test to measure the cooling capacity at 4.2 K. A heat load was applied to the first stage cold preservation device so that the temperature was 50 K.

The cooling test results in 0.66 W of cooling capacity at 4.2 K.

In the following Examples and Comparative Examples, the mixing time of raw material powders, sulfonation heat treatment conditions, sintering heat treatment conditions, etc. regulated to ensure appropriate conditions. In addition, the test conditions for the refrigerator were set to be the same.

Example 2

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that Li ₂ CO ₃ powder was used instead of Na ₂ CO ₃ powder.

Example 3

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that K ₂ CO ₃ powder was used instead of Na ₂ CO ₃ powder.

Example 4

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that CaCO ₃ powder was used in addition to Na ₂ CO ₃ powder.

Example 5

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 4 except that Li ₂ CO ₃ powder was used instead of Na ₂ CO ₃ powder.

Example 6

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 4 except that K ₂ CO ₃ powder was used instead of Na ₂ CO ₃ powder.

Example 7

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 4 except that MgCO ₃ powder was used instead of CaCO ₃ powder.

Example 8

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 4 except that SrCO ₃ powder was used instead of CaCO ₃ powder.

Example 9

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 4 except that BaCO ₃ powder was used instead of CaCO ₃ powder.

Example 10

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that Gd ₂ O ₂ S powder was used instead of Gd ₂ O ₃ powder.

Example 11

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that Tb ₂ O ₃ powder was used instead of Gd ₂ O ₃ powder.

Example 12

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that Dy ₂ O ₃ powder was used instead of Gd ₂ O ₃ powder.

Example 13

The cold preservation material and cold preservation material particles were prepared 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 14

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that K ₂ CO ₃ powder was used in addition to Na ₂ CO ₃ powder.

Example 15

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that Li ₂ CO ₃ powder was used in addition to Na ₂ CO ₃ powder.

Example 16

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that in addition to Na ₂ CO 3 powder, K ₂ CO ₃ powder and CaCO ₃ powder were used.

Example 17

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that CaCO ₃ powder and SrCO ₃ powder were used in addition to Na ₂ CO ₃ powder.

Examples 18-20

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that the weight of the Na ₂ CO ₃ powder was reduced.

Examples 21 to 23

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1 except that the weight of the Na ₂ CO ₃ powder was increased.

Examples 24 and 25

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 4 except that the weight of the CaCO ₃ powder was reduced.

Examples 26-28

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 4 except that the weight of the CaCO ₃ powder was increased.

Examples 29 to 31

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 1, except that part of the Gd ₂ O ₃ powder was replaced by Tb ₂ O ₃ , Dy ₂ O ₃ or Ho ₂ O ₃ .

Example 32

Gd ₂ O ₃ powder was added to an aqueous solution of sodium alginate and stirred for 12 hours to obtain a suspension. An aqueous solution of sodium alginate was added so that the amount of sodium alginate was 2.3 mass% of the amount of raw material powder. The prepared suspension was added dropwise to an aqueous solution of calcium lactate as a gelling solution. A syringe was used to instill the suspension. The diameter of the syringe was 510 μm, and the distance from the tip of the syringe to the surface of the aqueous calcium lactate solution was 100 mm. The suspension was filled into a mold, and then the suspension was immersed in a gelling solution.

The suspension instilled with a syringe and the suspension filling the mold were kept in the gelling solution for 5 hours.

After this, the gelled granular particles were washed with clean water. The mold filling slurry was removed from the mold and then washed with clean water to obtain a molded body. After washing the molded body and particles, the molded body and particles were dried. The sodium concentration in the granular particles was 0.78 atom% and the carbon concentration was 082 wt%. After the molded body and particles were dried, the molded body and particles were degreased, sulfurized and sintered.

Degreasing was carried out at 600°C for 6 hours in an air atmosphere, and after defatting, the sodium concentration of the granular particles was 1.0 atomic% and the carbon concentration was 0.54 mass%. After degreasing, heat treatment was carried out at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (H ₂ S) to sulfurize the molded body and particles. Heat treatment was carried out at 1300°C for 12 hours under an inert gas atmosphere under pressure to sinter the molded body and particles. The main constituent of the cold storage material and the cold storage material particles of Example 32 is gadolinium oxysulfide. The sodium concentration of the cold storage material of Example 32 and the cold storage material particles was 0.83 atomic percent.

Example 33

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 32 except that an aqueous solution of potassium alginate was used instead of an aqueous solution of sodium alginate.

Examples 34-38

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 33 except that the amount of the potassium alginate aqueous solution was increased or decreased.

Example 39

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 32 except that instead of an aqueous solution of calcium lactate, an aqueous solution of magnesium chloride was used.

Example 40

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 32 except that an aqueous solution of strontium chloride was used instead of an aqueous solution of calcium lactate.

Example 41

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 32 except that an aqueous barium chloride solution was used instead of an aqueous solution of calcium lactate.

Example 42

The cold preservation material and cold preservation material particles were produced in the same manner as in Example 32 except that K ₂ CO ₃ powder was added as a raw material powder.

Example 43

The cold preservation material and cold preservation material particles were produced in the same manner as in Example 18 except that Li ₂ CO ₃ powder was added as a raw material powder.

Example 44

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 32, except that an air pulse dispenser was used instead of a syringe as the method of filling the mold with the suspension and the method of instilling the suspension. The nozzle diameter was 510 μm, and the distance from the tip of the nozzle to the surface of the aqueous calcium lactate solution was 100 mm.

Example 45

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 32, except that a piezo dispenser was used instead of a syringe as a method for filling the mold with the slurry and a method for instilling the slurry. The nozzle diameter was 510 μm, and the distance from the tip of the nozzle to the surface of the aqueous calcium lactate solution was 100 mm.

Examples 46-51

The particles of the cold storage material of Examples 46-51 differ from the particles of the cold storage material of Example 44 in size or aspect ratio. When obtaining a particle of the cold preservation material of Examples 51-56, the diameter of the syringe and the distance from the tip of the syringe to the surface of the gelling solution were changed compared to the case of obtaining a particle of the cold preservation material of Example 1.

Example 52

The cold preservation material and cold preservation material particles were produced in the same manner as in Example 32, except that a continuous type jet apparatus was used instead of a syringe as the method of filling the mold with the slurry and the method of dropping the slurry instead of a syringe. The nozzle diameter was 510 μm, and the distance from the tip of the nozzle to the surface of the aqueous calcium lactate solution was 100 mm.

Examples 53-56

The cold preservation material and the cold preservation material particles were prepared in the same manner as in Example 1, except that the weight of the polyvinyl alcohol was changed. In this case, the strength of granular particles was measured in the same way as in Example 1.

Example 57-60

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 32, except that the amount of sodium alginate relative to the amount of raw material powder was changed by changing the concentration of the sodium alginate aqueous solution or the ratio of the aqueous alginate solution sodium and powder raw materials. In this case, the strength of the granular particles was measured in the same way as in Example 1.

Example 61

The cold preservation material and cold preservation material particles were produced in the same manner as in Example 1 except that Al ₂ O ₃ powder was also used as the raw material powder. Al ₂ O ₃ powder was added so that the Al content in the particles of the cold preservation material was 15 atomic%.

Example 62

The cold preservation material and cold preservation material particles were produced in the same manner as in Example 4 except that Al ₂ O ₃ powder was also used as the raw material powder. Al ₂ O ₃ powder was added so that the Al content in the particles of the cold preservation material was 15 atomic%.

Example 63

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 32 except that instead of an aqueous solution of calcium lactate, an aqueous solution of aluminum chloride was used. Al was added so that the amount of Al contained in the cold preservation material particles was 0.01 atomic%.

Example 64

The cold preservation material and cold preservation material particles were prepared in the same manner as in Example 32 except that an aqueous solution of aluminum chloride was used in addition to an aqueous solution of calcium lactate. Al was added so that the amount of Al contained in the cold preservation material particles was 0.01 atomic%.

Comparative example 1

The cold preservation material and cold preservation material particles of Comparative Example 1 differ from the cold preservation material and cold preservation material particles of Example 1 in that the atomic concentration of sodium is 0.0008 atomic%. When producing the cold preservation material and the cold preservation material particle of Comparative Example 1, the weight of the Na ₂ CO ₃ powder was reduced compared with the case of producing the cold preservation material and the cold preservation material particle of Example 1.

Comparative example 2

The cold preservation material and cold preservation material particle of Comparative Example 2 differ from the cold preservation material and cold preservation material particle of Example 1 in that the atomic concentration of sodium reaches 15 atomic %. When the cold preservation material and the cold preservation material particle of Comparative Example 2 were obtained, the weight of the Na ₂ CO ₃ powder was increased compared with the case of obtaining the cold preservation material and the cold preservation material particle of Example 1. Here, in addition to Gd ₂ O ₂ S was noticeably formed by NaGdS ₂ .

Comparative example 3

The cold preservation material and cold preservation material particle of Comparative Example 3 differ from the cold preservation material and cold preservation material particle of Example 4 in that the atomic concentration of calcium reaches 15 atomic %. When producing the cold preservation material and cold preservation material particle of Comparative Example 3, the weight of CaCO ₃ powder was increased compared with the case of producing the cold preservation material and cold preservation material particle of Example 4.

Comparative example 4

The cold preservation material and cold preservation material particle of Comparative Example 4 differ from the cold preservation material and cold preservation material particle of Example 1 in that they do not contain the first group element. The cold preservation material and the cold preservation material particle of Comparative Example 4 were produced without using a powder containing an element of the first group.

Comparative Example 5

The granular cold storage material particles of Comparative Example 5 differ from those of Example 1 in that carbon constitutes up to 25% by weight. The granular particles of Comparative Example 5 had a carbon concentration of 12 mass% after degreasing, but after sintering, the particles cracked or split and could not be removed. For this reason, specific heat capacity and strength assessments and testing of the refrigerator could not be carried out. When the cold preservation material and the cold preservation material particle of Comparative Example 5 were produced, the weight ratio of polyvinyl alcohol used as a binder was increased to 34 mass% of the amount of raw material powder.

Comparative Example 6

The granular body of the cold storage material of Comparative Example 6 differs from the granular body of Example 1 in that the carbon content is only 0.005 mass%. In Comparative Example 6, particles could not be recovered after granulation. For this reason, specific heat capacity and strength assessments and testing of the refrigerator could not be carried out. When producing the cold preservation material and the cold preservation material particle of Comparative Example 6, the weight ratio of polyvinyl alcohol to raw material powder was 0.2 mass%.

Comparative example 7

The granular particles of cold storage material after degreasing treatment in Comparative Example 7 differ from those in Example 1 in that the carbon content reaches 15 mass%. The carbon concentration before degreasing was 19 wt.%. The granular particles of Comparative Example 7 were sintered to obtain a cold storage material and cold storage material particles. In the production of the cold preservation material and the cold preservation material particle of Comparative Example 7, degreasing was carried out at 400°C for 1 hour in an air atmosphere using polyvinyl alcohol in an amount of 24 mass% of the amount of raw material powder.

Comparative Example 8

The cold preservation material particle of Comparative Example 8 after degreasing differs from the particle of Example 1 in that the carbon content is less than or equal to the detection limit. The granular particles of Comparative Example 8 were cracked or chipped after degreasing. The carbon concentration before degreasing was 0.01 wt%. When producing the cold preservation material and cold preservation material particles of Comparative Example 8, polyvinyl alcohol accounted for 0.2 mass% of the raw material powder amount, and degreasing was carried out at 800°C for 12 hours in an air atmosphere.

Comparative Example 9

The cold storage material and cold storage material particles of Comparative Example 9 differ from the material of Example 61 in that the Al contained in the cold storage material particles is up to 25 atomic %. In the production of the cold preservation material and the cold preservation material particle of Comparative Example 9, the weight of the Al ₂ O ₃ powder was increased compared with the case of the production of the cold preservation material and the cold preservation material particle of Example 61.

The cold storage materials of the Examples and Comparative Examples had their maximum volumetric specific heat capacity at 10 K or less and thermal conductivity at 4.2 K measured. The results are summarized in Table 1, Table 2 and Table 3.

The cooling capacity of the cold storage material particles in each of the Examples and Comparative Examples is shown in Table 1, Table 2 and Table 3. 250 g of the cold storage material particles in each of the Examples and Comparative Examples were poured into the low temperature side of the second stage of the storage apparatus cold of the two-stage GM refrigerator shown in FIG. 1, and 250 g of Pb cold preservation material was poured into the high temperature side, the refrigerator was assembled, and a cooling test was carried out to measure the cooling performance at 4.2 K. The heat load was applied to the first stage cold preservation device such that the temperature was 50 K.

The evaluation results of the strength of the cold storage material granules before degreasing and after degreasing according to each of the Examples and Comparative Examples are shown in Table 3. A cylindrical container with a diameter of 15 mm and a height of 5 mm was filled with granular particles according to each of the Examples and Comparative Examples. In this case, the cylindrical container was filled with cold preservation materials in an amount sufficient to ensure that the granular particles were fixed in the cylindrical container and could not move freely. A single vibration with an amplitude of 2 mm and a maximum acceleration of 200 m/s ² was applied to the container 1×10 ³ times. As a result, the proportion of destroyed granular particles of the cold preservation material was assessed.

In both Comparative Example 1 and Comparative Example 4, it can be seen that when the atomic concentration of a Group 1 element in the cold storage material is less than 0.001 atomic% or the cold storage material does not contain a Group 1 element, the thermal conductivity is 0.005 W/cm⋅ K and 0.004 W/(cm⋅K). This is believed to be due to the fact that the sintering promoting effect has decreased due to the reduction in the proportion of the group 1 element in the cold-preserving material, and because the number of small voids has increased.

As in Comparative Example 2, it can be seen that when the atomic concentration of a Group 1 element in the cold storage material is more than 10 atomic%, the volumetric specific heat capacity is 0.4 J/(cm ³ ⋅K). This is thought to be because the relative amount of rare earth oxysulfide has decreased, as sulfide containing rare earths and a group 1 element is formed as the proportion of the group 1 element in the cold-storing material increases.

From the results of Comparative Example 3, it can be seen that when the atomic concentration of the second group element in the cold preservation material was more than 10 atomic%, the thermal conductivity increased, but the volumetric specific heat was only 0.4 J/(cm ³ ⋅K), and the refrigeration performance when used particles of material for maintaining cold was significantly reduced. This is believed to be due to the fact that the proportion of rare earth element decreases relatively as the proportion of group 2 element increases in the particles of the cold preservation material.

From the results of Tables 1 and 4, the strength increases with the addition of the sintering aid, so that the content of the metal or metalloid element obtained from the sintering aid is 0.01 atomic% or more. When the content was more than 20 atomic%, the strength was further increased, but the volumetric specific heat capacity was reduced to 0.4 J/(cm ³ ⋅K), and the refrigeration performance of using material particles to maintain cold was significantly reduced. This is believed to be due to the fact that the proportion of rare earth element decreases relatively as the proportion of auxiliary agglomerate in the cold preservation material particles increases.

From Tables 1 and 2, it can be seen that when the particle size of the cold preservation material is in the range of 50 μm or more and 3000 μm or less, the cooling performance at 4.2 K is significantly improved.

Tables 1 and 2 show that when the particle aspect ratio of the cold preservation material is 5 or less, the cooling performance at 4.2 K is significantly improved.

From Tables 1 and 2 it can be seen that even when the method of granulating the particles of the material for maintaining cold is different, with appropriate adjustment of the synthesis conditions, the same particle size, aspect ratio, content of elements of the first and second groups and thermal conductivity appear.

From Table 1 and Table 2, it can be seen that even if the cold storage material particles are produced by different granulation methods, the performance and reliability of the refrigerator equipped with the cold storage material particles are equivalent if the particle size, aspect ratio and thermal conductivity are equivalent.

From Table 3, the strength of the granular particles is high when the granular particles contain 0.001 atomic% or more and 10% or less of a Group 1 element and 0.01 mass% or more and 20 mass% or less of carbon before degreasing. When the carbon concentration is below 0.01 wt%, the granular particles are very fragile and cannot be recovered as particles.

Table 3 shows that when the element of the first group is contained in an amount of 0.001 atomic% or more and 10% or less, and the carbon after degreasing is contained in an amount of 0.001 atomic% or more and 10 mass% or less, both strength and and sinterability of granular particles. In addition, a refrigerator equipped with the obtained particles of the material to preserve cold demonstrates high refrigeration characteristics. When the carbon concentration after degreasing exceeds 10 mass%, the particle strength is maintained even after degreasing, but since the molding density is low and the sintering ability is poor, the particle density is low, and the specific heat capacity and thermal conductivity are low. For this reason, the refrigeration performance when using particles in a refrigerator is also reduced. When the carbon concentration is less than 0.001 wt.%, the defatted particles are very fragile and therefore cannot be recovered as particles.

In the above Examples, the effects exhibited by the cold storage material of the first embodiment and the cold storage material particle of the second embodiment were confirmed.

Although an air pulse meter or a piezo meter has been described as an example of a metering device, a plunger metering device can also be used.

As an example of an inkjet apparatus, a continuous type inkjet apparatus has been described, but an on-demand inkjet apparatus can be used.

Although certain embodiments of the invention have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These embodiments may be embodied in various other forms; in addition, various exceptions, substitutions and modifications may be made without departing from the spirit of the inventions. For example, a component of one embodiment may be replaced or replaced by a component of another embodiment. Such embodiments and modifications thereof are within the spirit of the invention and are included within the scope of the invention as described in the claims and their equivalent scope.

List of reference items

100 Cryogenic refrigerator to keep cold

114, 115 Cold storage device

118, 119 Cold keeping material

500 Cryopump

600 Superconducting magnet

700 Nuclear magnetic resonance imaging apparatus

800 Nuclear magnetic resonance apparatus

900 Apparatus for drawing single crystals using a magnetic field

1000 Helium re-condensation device

Claims (30)

1. Cold preservation material including: a rare earth oxysulfide 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; And an element of the first group in an amount in the range from 0.001 to 10 at.%, for which the maximum value of volumetric specific heat in the temperature range from 2 to 10 K is 0.5 J/(cm ³ ⋅K) or more. 2. The cold preservation material according to claim 1, wherein the element of the first group is at least one element selected from the group consisting of Li, Na and K. 3. Material for maintaining cold according to claim 1 or 2, additionally including an element of the second group in an amount of 10 at.% or less. 4. Material for preserving cold according to claim 1 or 2, additionally including an element of the second group in an amount from 0.001 to 10 at.%. 5. The cold preservation material according to claim 3 or 4, wherein the element of the second group is at least one element selected from the group consisting of Mg, Ca, Sr and Ba. 6. Material for maintaining cold according to any one of paragraphs. 1-5, further including from 0.01 to 20 at.% of at least one element selected from the group consisting of Al, Fe, Cu, Ni, Co, Zr and B. 7. A cold storage material particle formed from the cold storage material according to any one of claims. 1-6 and having a size from 50 microns to 3 mm. 8. A particle of cold preservation material according to claim 7, in which the aspect ratio is from 1 to 5. 9. Granular particle, which is the raw material for the particle of cold preservation material according to claim 7 or 8, including: a rare earth oxide 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 oxysulfide 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; an element of the first group in an amount from 0.001 to 10 at.%; And carbon in an amount from 0.01 to 20 wt.%, in which the particle size is from 70 µm to 5 mm, and the aspect ratio is from 1 to 5. 10. A defatted granular particle, which is the raw material for a particle of cold preservation material according to claim 7 or 8, including: a rare earth oxide 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 oxysulfide 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; an element of the first group in an amount from 0.001 to 10 at.%; And carbon in an amount from 0.001 to 10 wt.%, in which the particle size is from 70 µm to 5 mm, and aspect ratio ranges from 1 to 5. 11. A device for preserving cold, containing a material for preserving cold according to any one of paragraphs. 1-6. 12. A cold preservation device filled with a plurality of particles of the cold preservation material according to claim 7 or 8. 13. A refrigerator including a device for maintaining cold according to claim 11 or 12. 14. Cryopump, including a refrigerator according to claim 13. 15. A superconducting magnet including a refrigerator according to claim 13. 16. An apparatus for nuclear magnetic resonance imaging, including a refrigerator according to claim 13. 17. A nuclear magnetic resonance apparatus, including a refrigerator according to claim 13. 18. An apparatus for drawing single crystals with the application of a magnetic field, including a refrigerator according to claim 13. 19. A device for re-condensing helium, including a refrigerator according to claim 13.