Cold storage material particles and method for producing the same, cold storage device, refrigerator, cryopump, superconducting magnet, nuclear magnetic resonance imaging apparatus, nuclear magnetic resonance apparatus, magnetic field application type single crystal pulling apparatus

Abstract

The granulated cold accumulating material of the embodiment contains at least one first element selected from the group consisting of a rare earth element, silver (Ag), and copper (Cu), and a second element different from the first element and forming a polyvalent metal ion in an aqueous solution, the atomic concentration of the second element being 0.001 atomic % or more and 60 atomic % or less, and the maximum value of the volumetric heat capacity at a temperature of 20 K or lower being 0.3 J / cm 3 • K or more.

Description

Technical Field

[0001] The embodiments of the present invention relate to cold storage material particles, cold storage devices, refrigerators, cryogenic pumps, superconducting magnets, nuclear magnetic resonance imaging devices, nuclear magnetic resonance devices, magnetic field applied single crystal pulling devices, and methods for manufacturing cold storage material particles. Background Technology

[0002] In cryogenic freezers used for cooling superconducting devices and creating ultra-high vacuum, cryogenic material particles containing cryogenic substances with high volumetric specific heat in the low-temperature region are used. Here, specific heat per unit volume is defined as volumetric specific heat. For cryogenic materials, examples include metals such as lead (Pb) and bismuth (Bi), rare earth compounds such as HoCu2 and Er3Ni, oxides such as Ag2O and Cu2O, and oxysulfides such as Gd2O2S.

[0003] In cryogenic freezers, various cryogenic material particles are filled into the cryoaccumulator. For example, cold is generated by heat exchange between the cryogenic material particles and helium gas passing through the cryoaccumulator. Cryogenic freezers employing cryogenic cycles such as the Gifford-McMahon (GM) method, the Stirling method, or the pulse tube method are used in superconducting nuclear magnetic resonance (MRI) devices and cryogenic pumps.

[0004] Furthermore, in maglev trains, the use of superconducting magnets to generate magnetic force necessitates the use of high-performance cryogenic systems. Additionally, in semiconductor manufacturing equipment, cryogenic pumps are used to maintain ultra-high vacuum in the chambers where thin films are formed on wafers. Moreover, recently, high-performance cryogenic systems have also been used in superconducting energy storage devices (SMES) and magnetic field-applied single-crystal pulling devices for manufacturing high-quality silicon wafers. Furthermore, the development and practical application of highly reliable pulse tube cryogenic systems are actively underway.

[0005] In such a refrigerator, compressed helium (He) gas or other working medium flows in one direction within a accumulator filled with cold storage material particles, supplying its heat energy to the cold storage material. Then, the working medium, expanding within the accumulator, flows in the opposite direction, absorbing heat energy from the cold storage material particles. As the reheating effect in this process improves, the thermal efficiency of the working medium circulation increases, enabling the achievement of even lower temperatures.

[0006] Cold storage material particles are filled into the cold storage container of a refrigerator, where they exert their freezing capacity in extremely low temperatures through heat exchange with helium (He) gas flowing in as the working medium. During this time, the cold storage material particles are subjected to pressure vibrations, stresses, and impacts from the high-pressure helium gas acting during refrigerator operation. In the case of a GM refrigerator, stress is further exerted on the cold storage material particles by the reciprocating motion of the displacement device (piston for compressing the working medium). Furthermore, during refrigerator startup, the temperature drops rapidly from near room temperature to an extremely low temperature of around 4K, resulting in significant thermal shock to the cold storage material particles.

[0007] Thus, the pressure vibrations and various stresses acting during the operation of the refrigeration unit cause the cold storage material particles to break down and become micronized. The resulting micronized particles damage components such as the refrigeration unit's seals, significantly reducing its freezing capacity. To maintain the refrigeration unit's high freezing capacity over a long period, and thus improve its long-term reliability, the cold storage material particles filling the refrigeration unit must possess excellent properties such as high specific heat capacity, high mechanical strength, high thermal conductivity, and high heat transfer efficiency.

[0008] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2017-58079 Patent Document 2: Japanese Patent Application Publication No. 2010-64946 Patent Document 3: Japanese Patent Application Publication No. 2003-213252 Patent Document 4: International Publication No. 2018 / 025581 Summary of the Invention

[0009] The problem that the invention aims to solve The problem to be solved by the present invention is to provide cold storage material particles with high mechanical strength and a method for manufacturing the same.

[0010] Methods for solving problems The cold storage material particles of the embodiment comprise at least one first element selected from the group consisting of rare earth elements, silver (Ag), and copper (Cu), and a second element different from the first element that forms polyvalent metal ions in aqueous solution. The atomic concentration of the second element is 0.001 atomic% or more and 60 atomic% or less, and the maximum volumetric specific heat at a temperature below 20 K is 0.3 J / cm³. 3 K and above. Attached Figure Description

[0011] Figure 1 This is an explanatory diagram of the cold storage material particles according to the first embodiment.

[0012] Figure 2 This is an explanatory diagram of the cold storage material particles according to the second embodiment.

[0013] Figure 3 This is an explanatory diagram of the cold storage material particles in the third embodiment.

[0014] Figure 4 This is a schematic cross-sectional view showing the main components of a GM refrigerator, which is an example of a refrigerator according to the fourth embodiment.

[0015] Figure 5 This is a cross-sectional view showing the schematic configuration of the cryogenic pump according to the fifth embodiment.

[0016] Figure 6 This is a perspective view showing the schematic configuration of the superconducting magnet according to the sixth embodiment.

[0017] Figure 7 This is a cross-sectional view showing the schematic configuration of the magnetic resonance imaging apparatus according to the seventh embodiment.

[0018] Figure 8 This is a cross-sectional view showing the schematic configuration of the nuclear magnetic resonance apparatus according to the eighth embodiment.

[0019] Figure 9 This is a perspective view showing the schematic configuration of the magnetic field applied single crystal pulling device according to the ninth embodiment. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that in the following description, the same or similar components are marked with the same symbol, and the description of components that have been described before is sometimes appropriately omitted.

[0021] In this specification, "extremely low temperature" refers, for example, to the temperature range in which superconductivity can be usefully utilized industrially. For example, it could be the temperature range below 20 K.

[0022] (First Implementation) The cold storage material particles of the first embodiment comprise at least one first element selected from the group consisting of rare earth elements, silver (Ag), and copper (Cu), and a second element different from the first element that forms polyvalent metal ions in aqueous solution. Furthermore, the atomic concentration of the second element is 0.001 atomic% or more and 60 atomic% or less. In addition, the maximum volumetric specific heat at a temperature below 20 K is 0.3 J / cm³. 3 K and above.

[0023] Figure 1 This is an explanatory diagram of the cold storage material particles according to the first embodiment. Figure 1 (a) is a schematic cross-sectional view of the cold storage material particles. Figure 1(b) is a schematic cross-sectional view obtained by magnifying a portion of the cold storage material particles. Figure 1 (b) For example, Figure 1 (a) Schematic cross-sectional view of region R.

[0024] The cold storage material particles 10 of the first embodiment are used, for example, in a freezer to achieve extremely low temperatures below 5K.

[0025] The shape of the cold storage material particles 10 is, for example, spherical. Figure 1 (a) indicates the case where the cold storage material particle 10 is a positive sphere. Figure 1 (a) is a cross-section through the center of the cold storage material particle 10. The particle size of the cold storage material is ( Figure 1 In (a), D) is, for example, 50 μm or more and 3 mm or less. The aspect ratio of the cold storage material particle 10 is, for example, 5 or less. The aspect ratio of the cold storage material particle 10 is the ratio of the major axis to the minor axis of the cold storage material particle 10.

[0026] The particle size D of the cold storage material particles 10 is the equivalent circle diameter. The equivalent circle diameter is the diameter of a circle whose area is equivalent to the area of ​​the shape observed in an image such as an optical microscope image or a scanning electron microscope image (SEM image). The particle size D of the cold storage material particles 10 can be determined, for example, by image analysis of an optical microscope image or a SEM image.

[0027] The maximum volumetric specific heat of the cold storage material particles 10 at temperatures below 20K is 0.3 J / cm³. 3 Above K. The maximum volumetric specific heat of the cold storage material particles 10 at temperatures below 20 K is 0.3 J / cm³. 3 Cooling materials above K.

[0028] The cold storage material particles 10 contain a cold storage element. The cold storage element is at least one element selected from the group consisting of rare earth elements, silver (Ag), and copper (Cu). The rare earth elements are at least one element selected from the group consisting of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0029] The cold storage element is one of the elements that constitute the cold storage substance. The cold storage element is an example of the primary element.

[0030] The cold storage material particles 10 contain added metal elements. The added metal elements are metal elements that form polyvalent metal ions in aqueous solution. For example, the added metal elements are at least one element selected from the group consisting of calcium (Ca), magnesium (Mg), beryllium (Be), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co).

[0031] An example of adding a metal element as a second element. For example, two or more added metal elements can also be included in the cold storage material particles 10.

[0032] The atomic concentration of the added metal element in the cold storage material particles 10 is 0.001 atomic% or more and 60 atomic% or less. It should be noted that when the cold storage material particles 10 contain two or more added metal elements, the total atomic concentration of each added metal element is set as the atomic concentration of the added metal element in the cold storage material particles 10.

[0033] The atomic concentration of the added metal element is, for example, lower than the atomic concentration of the cold-storage element. The atomic concentration of the added metal element is, for example, higher than the atomic concentration of the cold-storage element.

[0034] The detection of elements contained in the cold storage material particles 10 and the determination of the atomic concentration of the elements can be performed, for example, by energy dispersive X-ray spectrometry (EDX) or wavelength dispersive X-ray analysis (WDX).

[0035] The atomic concentration of the added metal element in the cold storage material particles 10 is, for example, as follows: Figure 1 (a) shows the average atomic concentration measured at 13 measurement points P1 to P13. The atomic concentration of the added metal is the atomic concentration with the total amount of atoms measured by WDX or EDX as the denominator. The measurement point is, for example, Φ20 μm.

[0036] It should be noted that the detection of elements contained in the cold storage material particles 10 and the determination of the atomic concentration of the elements can also be performed by dissolving the cold storage material particles 10 in a liquid and using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0037] The cold storage material particles 10 contain, for example, oxygen sulfides. The cold storage material contains, for example, oxygen sulfides as a main component. In the case where the cold storage material contains oxygen sulfides, the cold storage material particles 10 contain oxygen (O) and sulfur (S).

[0038] The cold storage material contains oxygen sulfides, such as gadolinium (Gd). The cold storage material contains oxygen sulfides, such as gadolinium oxysulfide. The cold storage material contains oxygen sulfides, such as Gd₂O₂S.

[0039] When the oxygen sulfide contained in the cold storage material is gadolinium oxysulfide, the cold storage element is gadolinium (Gd).

[0040] The identification of the cold storage material contained in the cold storage material particles 10 can be performed, for example, by powder X-ray diffraction (XRD).

[0041] The cold storage material particles 10 contain cold storage substances, for example, rare earth compounds as the main component. Examples of rare earth compounds in the cold storage material include HoCu2 and Er3Ni.

[0042] When the cold storage material contains HoCu2, the cold storage elements are holmium (Ho) and copper (Cu). Furthermore, when the cold storage material contains Er3Ni, the cold storage element is erbium (Er).

[0043] The cold storage material particles 10 contain, for example, an oxide as the main component. In the case where the cold storage material contains an oxide, the cold storage material particles 10 contain oxygen (O).

[0044] The oxide contained in the cold storage material includes, for example, at least one of silver (Ag) and copper (Cu). The oxide contained in the cold storage material is, for example, silver oxide or copper oxide. The oxide contained in the cold storage material is, for example, Ag₂O or Cu₂O.

[0045] When the oxide contained in the cold storage material is silver oxide, the cold storage element is silver (Ag). Furthermore, when the oxide contained in the cold storage material is copper oxide, the cold storage element is copper (Cu).

[0046] Compositional analysis of the cold storage material can be performed, for example, using EDX or WDX. Furthermore, the identification of the cold storage material can be performed, for example, using powder X-ray diffraction.

[0047] Figure 1 (b) is a schematic cross-sectional view obtained by magnifying a portion of the cold storage material particles. Figure 1 (b) For example, Figure 1 (a) Schematic cross-sectional view of region R.

[0048] The cold storage material particles 10 in the first embodiment are as follows: Figure 1As shown in (b), it comprises four phases: phase A, phase B, phase C, and phase D. Phases A, B, C, and D are distinct phases. Phases A, B, C, and D are examples of the first, second, third, and fourth phases, respectively. It should be noted that two distinct phases mean that at least two phases have different chemical compositions.

[0049] Phases A, B, C, and D are, for example, crystalline phases. Phases A, B, C, or D can also be amorphous phases.

[0050] Phase A is a cold-storage material. Phase A contains cold-storage elements. For example, phase A is gadolinium oxysulfide. For example, phase A is Gd₂O₂S.

[0051] When phase A is gadolinium oxysulfide, the cold storage element is gadolinium (Gd). Phase A contains gadolinium (Gd), sulfur (S), and oxygen (O).

[0052] The cold storage material particles 10, for example, contain two or more different added metal elements. The cold storage material particles 10 contain a first added metal element and a second added metal element different from the first added metal element. An example of the first added metal element is element α. An example of the second added metal element is element β.

[0053] Phase B contains a first added metal element and a second added metal element. Phase B contains two or more different elements, including both the first and second added metal elements. The atomic concentration of the added metal elements in Phase B is greater than that in Phase A.

[0054] Phase B can be an oxide containing calcium (Ca) and aluminum (Al). Phase B can also be a compound containing calcium (Ca), aluminum (Al), and oxygen (O). For example, phase B is CaO·6Al2O3.

[0055] In the case where phase B is an oxide containing calcium (Ca) and aluminum (Al), the first added metal element is calcium (Ca) and the second added metal element is aluminum (Al).

[0056] Phase B may further contain cold storage elements. For example, phase B may contain gadolinium (Gd). In this case, phase B contains calcium (Ca), aluminum (Al), gadolinium (Gd), and oxygen (O).

[0057] Phase C contains a second added metal element.

[0058] The C phase is, for example, aluminum oxide. The C phase is, for example, Al2O3.

[0059] When the C phase is alumina, the C phase contains aluminum (Al) and oxygen (O).

[0060] The D phase contains a cold storage element and a second added metal element. Examples of the D phase include oxides containing gadolinium (Gd) and aluminum (Al). Examples of the D phase include compounds containing gadolinium (Gd), aluminum (Al), and oxygen (O). An example of the D phase is GdAlO3.

[0061] In the cross-section of the cold storage material particle 10, for example, phase A surrounds phases B, C, and D. In the cross-section of the cold storage material particle 10, the proportion of the area occupied by phase A, which contains the cold storage element, is, for example, greater than the proportion of the area occupied by the other phases.

[0062] In the cross-section of the cold storage material particle 10, the area occupied by the B phase containing added metal elements is, for example, more than 0.001% and less than 75%.

[0063] In the cross-section of the cold storage material particle 10, the proportions of the area occupied by phase A, phase B, phase C, and phase D can be determined, for example, by image analysis from optical microscope images or scanning electron microscope images (SEM images).

[0064] For example, by using a scanning electron microscope (SEM) to capture reflected electron images of the cross-section of the cold storage material particles 10, phases can be distinguished by differences in image density. Furthermore, by using EDX or WDX to perform point-based compositional analysis within each phase, the types and concentrations of elements contained in each phase can be determined. For example, by considering XRD results in addition to the aforementioned EDX or WDX results, the compounds contained in each phase can be identified.

[0065] In image analysis of scanning electron microscope (SEM) images, for example, reflectance electron images are used. Image analysis software, such as ImageJ, can be used. Corresponding regions can be extracted from the image based on the brightness of the reflectance electron image. When extracting these regions, the brightness is binarized, for example. The extracted regions are then compared visually with the original image. In cases where obvious grain boundaries or intragranular areas are not properly extracted, the area of ​​each phase is evaluated after manual image correction. Software for image correction, such as Paint, a software standard on Windows 10, can be used.

[0066] In the cross-section of the cold storage material particle 10, the area of ​​each B phase containing the added metal element is, for example, 0.001 μm. 2 Above and 6000μm 2 Below. The area of ​​each B phase containing the added metal element is, for example, the central value of the areas of multiple B phases.

[0067] In the cross-section of the cold storage material particles 10, the particle size of each B phase containing the added metal element is, for example, 0.1 μm or more and 100 μm or less. Here, the particle size is, for example, the major axis of the B phase. The major axis of the B phase is the longest length among any two points on the outer periphery of the B phase. The particle size of each B phase containing the added metal element is, for example, the central value of the particle sizes of multiple B phases.

[0068] In the cross-section of the cold storage material particles 10, the area and particle size of the B phase containing added metal elements can be determined, for example, by image analysis of optical microscope images or scanning electron microscope images.

[0069] Next, an example of a method for manufacturing the cold storage material particles 10 according to the first embodiment will be described.

[0070] The method for manufacturing cold storage material particles according to the first embodiment includes: mixing powder containing at least one first element selected from the group consisting of rare earth elements, silver (Ag) and copper (Cu) with an aqueous solution of alginate to form a slurry; spraying the slurry in droplets into a gelling solution containing a second element that forms polyvalent metal ions; holding the slurry in the gelling solution to form gelled particles; and sintering the particles.

[0071] First, the raw material powder of the cold storage substance is added to an alginate aqueous solution and mixed to prepare a slurry. The cold storage substance contains cold storage elements. A ball mill is used, for example, to mix the raw material powder of the cold storage substance with the alginate aqueous solution.

[0072] The mixing time is, for example, more than one hour and less than one week. By changing the mixing time, for example, the proportion of the second phase in contact with the third phase and the proportion of the second phase in contact with the fourth phase in the cross-section of the manufactured cold storage material particles can be changed.

[0073] Next, the slurry is sprayed as droplets into a gelation solution containing a second element that forms polyvalent metal ions. The prepared slurry is then added dropwise to the gelation solution to gel the slurry. Devices for adding the slurry to the gelation solution include, for example, droppers, burettes, pipettes, syringes, dispensers, or inkjet printers.

[0074] Depending on the device used for ejection, the viscosity of the slurry suitable for ejection varies. For example, for syringe ejection, it is 0.1 mPa·s or more and 1,000,000 mPa·s; for dispenser ejection, it is 50 mPa·s or more and 300,000 mPa·s or less; and for inkjet ejection, it is 1 mPa·s or more and 1,000 mPa·s or less. The viscosity of the slurry should be adjusted appropriately according to the device used for ejection.

[0075] The particle manufacturing rate varies depending on the ejection method. For example, the particle manufacturing rate is about 1 particle / second with a syringe, but it can reach about 1 to 400 particles / second by using a dispenser, and about 500 to 2000 particles / second by inkjet printing. The manufacturing rate can be further increased by adding the same nozzle.

[0076] When using a syringe, the nozzle diameter of the syringe is, for example, 50 μm or more and 3000 μm or less. Furthermore, the distance from the tip of the syringe to the surface of the gelling solution is, for example, 1 mm or more and 1000 mm or less. By changing the nozzle diameter of the syringe and the distance from the tip of the syringe to the surface of the gelling solution, for example, the particle size and aspect ratio can be changed.

[0077] When using a distributor for ejection, any of the following devices can be used: an air pulse distributor, a plunger distributor, or a piezoelectric distributor. In an air pulse distributor, the slurry is ejected drop by drop at the ejection outlet using a piston rod driven up and down by high-pressure air. In the case of a piezoelectric distributor, the slurry is ejected drop by drop using a piston rod driven up and down by a piezoelectric element or by pressure waves generated by piezoelectric volume changes. Here, the particle size can be changed by altering the nozzle outlet diameter, i.e., the nozzle diameter. The nozzle diameter is, for example, 50 μm or more and 3000 μm or less.

[0078] As described above, the slurry is ejected by driving the piston rod up and down. Therefore, the particle manufacturing rate varies depending on the duration of the piston rod's up-and-down movement. For example, the piston rod driving time is between 2.5 ms and 100 ms per cycle.

[0079] By changing the distance from the nozzle tip of the dispenser to the surface of the gelling solution, for example, the particle size and aspect ratio can be changed. The distance from the nozzle tip to the surface of the gelling solution is, for example, 0.1 mm or more and 1000 mm or less.

[0080] Inkjet printing, as a method of ejection, is broadly divided into continuous and on-demand types, and either type can be used. Furthermore, on-demand printing is further divided into three types: piezoelectric, thermal, and valve-based, and any of these can be used.

[0081] In continuous flow systems, liquid column atomization is promoted by applying pressure waves to the liquid column ejected through a pressurized flow path. These pressure waves are applied via pumps, piezoelectric elements, etc. On the other hand, in on-demand systems, droplets are ejected one at a time, but the method of ejecting the droplets differs depending on the specific application.

[0082] In the piezoelectric method, a pressure wave is generated by the rapid volume change of the piezoelectric element caused by applying a voltage, and this pressure wave is used to eject droplets one by one. In the thermal method, bubbles are generated in the liquid being sprayed after being heated by a heater, and droplets are ejected one by one. Furthermore, in the valve method, droplets are ejected one by one by using a solenoid to open and close the cap of the nozzle.

[0083] In thermal inkjet printing, the ink is heated and the moisture evaporates, increasing the likelihood of raw material powder clogging the flow path and hindering ejection. Therefore, in on-demand inkjet printing, piezoelectric and valve-based methods are preferred over thermal methods.

[0084] The nozzle diameter of the inkjet nozzle is, for example, 50 μm or more and 3000 μm or less. The distance from the tip of the nozzle to the surface of the gelling solution is, for example, 0.1 mm or more and 1000 mm or less. By changing the nozzle diameter and the distance from the tip of the syringe to the surface of the gelling solution, the particle size and aspect ratio can be changed, for example.

[0085] In inkjet printing, changes in the viscosity of the ink result in changes in the amount of ink exiting the nozzle per unit time, thus altering the particle size. Therefore, the nozzle diameter is adjusted according to the ink viscosity to ensure a particle size of 50 μm or larger but less than 3 mm.

[0086] In continuous inkjet printing, the particle manufacturing speed can be altered by changing the waveform of the pressure wave applied to the liquid column ejected through the pressurized flow path. Furthermore, in on-demand piezoelectric inkjet printing, the particle manufacturing speed can be changed by altering the frequency of volume change of the piezoelectric element. Additionally, in on-demand thermal inkjet printing, the particle manufacturing speed can be changed by altering the heating frequency of the heater. Furthermore, in on-demand valve-type inkjet printing, the particle manufacturing speed can be changed by altering the valve opening and closing frequency. The frequencies in each inkjet type are, for example, 500 Hz or higher and 2000 Hz or lower. When the frequency is 500 Hz or higher and 2000 Hz or lower, the particle manufacturing speed is 500 particles / second or higher and 2000 particles / second or lower.

[0087] A slurry, added dropwise to a gelling solution using a dropper, burette, pipette, syringe, dispenser, inkjet printer, etc., gels by being held in the gelling solution. By gelling the slurry, spherical particles of the raw material powder containing a cooling substance are formed.

[0088] The gelation solution contains added metal elements that become polyvalent metal ions. Gelation occurs through a cross-linking reaction generated by the polyvalent metal ions. As the slurry is held in the gelation solution for an extended period, the added metal elements gradually penetrate from the outer edges of the particles toward the center. By varying the holding time of the slurry in the gelation solution, the distribution of the added metal elements within the particles can be controlled.

[0089] The holding time of the slurry in the gelation solution is, for example, 10 minutes or more and 48 hours or less. Hereinafter, the holding time of the slurry in the gelation solution will also be referred to as the gelation time. By setting the holding time of the slurry in the gelation solution to 10 minutes or more, particles formed by the gelation of the added slurry can be obtained.

[0090] After the particles are formed through gelation, they are washed with pure water. By washing the particles, the added metal elements adsorbed on the surface of the particles are removed.

[0091] After washing, the particles are dried. Following drying, the particles are sintered to increase their mechanical strength and the density of the cold-storing material. If the cold-storing material is an oxysulfide, the particles may be sulfided, for example, before sintering.

[0092] When sulfiding the particles, heat treatment is performed in a sulfiding atmosphere. The sulfiding atmosphere may contain gases containing sulfur atoms with negative oxidation states, such as hydrogen sulfide (H₂S), carbon sulfide (CS₂), or methanethiol (CH₃SH). The heat treatment temperature is, for example, 400°C or higher and 700°C or lower. Furthermore, the heat treatment time is, for example, 1 hour or higher and 8 hours or lower.

[0093] The heat treatment of particle sintering is carried out, for example, in an atmosphere of inert gas. The heat treatment temperature is, for example, above 1000°C and below 2000°C. The heat treatment temperature is, for example, above 1100°C and below 1700°C. The heat treatment time is, for example, above 1 hour and below 48 hours.

[0094] During particle sintering, for example, a first phase containing a cold storage element and a second phase containing an added metal element can be formed. Furthermore, by setting two or more added metal elements, for example, a third phase containing added metal elements and a fourth phase containing both cold storage elements and added metal elements can be formed.

[0095] Second, third, or fourth phases can be formed, for example, by properly managing the heat treatment temperature during particle sintering, and the curves of the heat treatment's heating and cooling.

[0096] Furthermore, for example, by changing the heat treatment conditions for sulfidation and sintering of the particles, it is possible to change the area and particle size of each second phase in the cross-section of the particles.

[0097] Cooling materials include, for example, silver oxide, copper oxide, or rare earth oxides. Rare earth oxides include, for example, gadolinium oxide.

[0098] Alginate aqueous solutions include, for example, sodium alginate aqueous solution, ammonium alginate aqueous solution, or potassium alginate aqueous solution.

[0099] Gelation solutions include, for example, aqueous solutions of calcium lactate, calcium chloride, manganese(II) chloride, magnesium sulfate, beryllium sulfate, strontium nitrate, barium chloride, barium hydroxide, aluminum chloride, aluminum nitrate, aluminum lactate, ferric chloride(II), ferric chloride(III), copper chloride(II), nickel chloride(II), and cobalt(II) chloride.

[0100] The combination of the cold storage substance, the alginate aqueous solution, and the gelling solution is arbitrary. However, when the cold storage substance is silver oxide, if the gelling solution is a combination of calcium chloride aqueous solution, manganese(II) chloride aqueous solution, barium chloride aqueous solution, aluminum chloride aqueous solution, ferric chloride(II) aqueous solution, ferric chloride(III) aqueous solution, copper(II) chloride aqueous solution, nickel(II) chloride aqueous solution, or cobalt(II) chloride aqueous solution, silver chloride will be generated. Therefore, the above combinations are excluded.

[0101] The cold storage material particles 10 of the first embodiment can be manufactured using the above manufacturing method.

[0102] It should be noted that, for example, by controlling the gelation time, the atomic concentration distribution of the added metal element in the particles can be controlled to an arbitrary distribution. For example, by controlling the gelation time, the added metal element penetrates to the center of the particle, and the added metal element in the particle can be distributed approximately uniformly.

[0103] Furthermore, by controlling the amount of raw material powder of the cold storage material, the atomic concentration of the added metal element in the gelation solution, and the sintering conditions of the particles, the chemical composition of the first phase and the second phase of the cold storage material particles 10, the area ratio of the first phase and the second phase in the cross section of the cold storage material particles 10, and the area of ​​the first phase and the second phase in the cross section of the cold storage material particles 10 can be adjusted to suitable values.

[0104] Next, the function and effect of the cold storage material particles 10 in the first embodiment will be explained.

[0105] In cryogenic refrigerators used for cooling superconducting devices, various cryogenic material particles are filled into the cryogenic accumulator. For example, cold is generated by heat exchange between the cryogenic material particles and helium gas passing through the cryogenic accumulator. The cryogenic material particles filled into the cryogenic accumulator are required to have excellent properties such as high volumetric specific heat, high mechanical strength, high thermal conductivity, and high heat transfer rate.

[0106] The maximum volumetric specific heat of the cold storage material particles 10 in the first embodiment at a temperature below 20K is 0.3 J / cm³. 3 K and above. Therefore, the cold storage material particles 10 possess high volumetric specific heat at extremely low temperatures.

[0107] Furthermore, the cold storage material particles 10 of the first embodiment contain an added metal element that forms polyvalent metal ions in an aqueous solution. The added metal element promotes the sintering of the particles during manufacturing. Therefore, the cold storage material particles 10 have a high degree of sintering and possess high mechanical strength.

[0108] Furthermore, to fully obtain the required properties of the cold storage material particles 10, such as mechanical strength, thermal conductivity, heat transfer rate, and volumetric specific heat, sufficient sintering temperature and sintering time are needed in the sintering process. By adding metal elements to promote sintering, the required sintering temperature and sintering time can be reduced. Therefore, the manufacturing cost of the cold storage material particles 10 can be reduced, providing inexpensive cold storage material particles 10.

[0109] Furthermore, the cold storage material particles 10 of the first embodiment have high thermal conductivity due to the high degree of sintering inside the particles. Additionally, the cold storage material particles 10 of the first embodiment also have a high degree of sintering at their outer periphery, thus improving heat transfer characteristics, for example, with helium gas in contact with the outer periphery. Therefore, the cold storage material particles 10 of the first embodiment have a high heat transfer rate.

[0110] The atomic concentration of the added metal element in the cold storage material particles 10 is 0.001 atomic% or more and 60 atomic% or less. More preferably, the atomic concentration of the added metal element in the cold storage material particles 10 is 0.01 atomic% or more and 40 atomic% or less.

[0111] When the atomic concentration of the added metal element in the cold storage material particles 10 exceeds the aforementioned lower limit, the degree of sintering increases, resulting in higher mechanical strength, thermal conductivity, and heat transfer rate of the cold storage material particles 10. Furthermore, when the atomic concentration of the added metal element in the cold storage material particles 10 is below the aforementioned upper limit, the volumetric specific heat increases.

[0112] The added metal element in the cold storage material particles 10 is preferably at least one element selected from the group consisting of calcium (Ca), magnesium (Mg), beryllium (Be), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co). The added metal element in the cold storage material particles 10 is further preferably at least one element selected from the group consisting of calcium (Ca), magnesium (Mg), beryllium (Be), strontium (Sr), and barium (Ba).

[0113] By adding the aforementioned metallic elements, the sintering of the particles during the manufacture of the cold storage material particles 10 is further promoted. As a result, the mechanical strength, thermal conductivity, and heat transfer rate of the cold storage material particles 10 are increased.

[0114] From the viewpoint of accelerating the gelation rate of the slurry during the manufacture of the cold storage material particles 10, calcium (Ca) is the preferred metal element to be added. Furthermore, from the viewpoint of improving the mechanical strength, thermal conductivity, and heat transfer rate of the cold storage material particles 10, aluminum (Al) is the preferred metal element to be added. The preferred metal elements to be added are calcium (Ca) and aluminum (Al).

[0115] The cold storage material particles 10 preferably contain alkali metal elements. By containing alkali metal elements, the cold storage material particles 10 can be sintered in the sintering process.

[0116] Therefore, it can promote the sintering of cold storage material particles 10, and increase the mechanical strength, thermal conductivity and heat transfer rate of cold storage material particles 10.

[0117] To fully obtain the required properties of the cold storage material particles 10, such as mechanical strength, thermal conductivity, heat transfer rate, and volumetric specific heat, sufficient sintering temperature and sintering time are needed in the sintering process. By utilizing the sintering-promoting effect of alkali metal elements, the required sintering temperature and sintering time can be reduced. Therefore, the manufacturing cost of the cold storage material particles 10 can be lowered, providing inexpensive cold storage material particles 10.

[0118] The atomic concentration of alkali metal elements in the cold storage material particles 10 is preferably 0.0001 atomic% or more and 10 atomic% or less, more preferably 0.001 atomic% or more and 5 atomic% or less.

[0119] In order to include alkali metal elements in the cold storage material particles 10, sodium alginate aqueous solution or potassium alginate aqueous solution is used, for example, as the alginate aqueous solution used in manufacturing the cold storage material particles 10.

[0120] The cold storage material particles 10 preferably comprise a first phase containing cold storage elements and a second phase containing added metal elements that is different from the first phase. For example, compared to the case where the cold storage material particles 10 are formed from a single phase, the number density of grain boundaries increases due to the presence of different phases.

[0121] Furthermore, the cold storage material particles 10 preferably include a third phase containing added metal elements and different from the first and second phases. For example, compared to the case where the cold storage material particles 10 are formed from two different phases, the presence of three different phases can suppress the grain growth of each phase, and the number density of grain boundaries further increases. Here, the number density of grain boundaries refers to the number of grain boundaries per unit volume.

[0122] Furthermore, the cold storage material particles 10 preferably include a fourth phase containing added metal elements and different from the first, second, and third phases. For example, compared to the case where the cold storage material particles 10 are formed from three different phases, the presence of four different phases can further suppress the grain growth of each phase, and the number density of grain boundaries increases dramatically.

[0123] The increased number density at grain boundaries enhances the strength of the cold storage material particles 10 relative to plastic deformation. Therefore, the inclusion of a second phase different from the first phase increases the mechanical strength of the cold storage material particles 10. The inclusion of a third phase in addition to the second phase further enhances the mechanical strength. The inclusion of both a third and a fourth phase in addition to the second phase further increases the mechanical strength of the cold storage material particles 10.

[0124] It should be noted that the cold storage material particles 10 can also be in the form of uniformly dispersed metal elements, with the cold storage material particles 10 consisting of a single phase. Here, uniform dispersion means that the added metal elements are uniformly dispersed in the cold storage material particles 10 at the atomic level, and the atomic concentration of the added metal elements is approximately constant in the overall cold storage material particles 10.

[0125] When the cold storage material particles 10 contain a first phase and a second phase, the proportion of the area occupied by the second phase in the cross section of the cold storage material particles 10 is preferably 0.01% or more and 75% or less, more preferably 0.01% or more and 50% or less.

[0126] In the cross-section of the cold storage material particles 10, if the proportion of the area occupied by the second phase exceeds the aforementioned lower limit, the grain boundary number density increases, and the mechanical strength of the cold storage material particles 10 increases. Furthermore, if the degree of sintering of the cold storage material particles 10 increases, the mechanical strength, thermal conductivity, and heat transfer rate also increase. Conversely, if the proportion of the area occupied by the second phase in the cold storage material particles 10 is lower than the aforementioned upper limit, the proportion of the cold storage material in the cold storage material particles 10 increases, and the volumetric specific heat increases.

[0127] In the cross-section of the cold storage material particle 10, the area of ​​each second phase is preferably 0.001 μm. 2 Above and 6000μm 2 Below. In the cross-section of the cold storage material particle 10, if the area of ​​the second phase exceeds the aforementioned lower limit, the number density of grain boundaries decreases, and the thermal conductivity of the cold storage material particle 10 increases. Furthermore, if the area of ​​each second phase in the cold storage material particle 10 is lower than the aforementioned upper limit, the number density of grain boundaries in the cold storage material particle 10 increases, and the mechanical strength of the cold storage material particle 10 increases.

[0128] In the cross-section of the cold storage material particles 10, the particle size of each second phase is preferably 0.1 μm or more and 100 μm or less. If the particle size of the second phase in the cross-section of the cold storage material particles 10 exceeds the aforementioned lower limit, the number density of grain boundaries decreases, and the thermal conductivity of the cold storage material particles 10 increases. Furthermore, by ensuring that the particle size of each second phase in the cold storage material particles 10 is below the aforementioned upper limit, the number density of grain boundaries in the cold storage material particles 10 increases, and the mechanical strength of the cold storage material particles 10 increases.

[0129] In the cross-section of the cold storage material particles 10, preferably more than 20% and less than 90% of the second phase is in contact with the third phase, and more than 40% and less than 75% of the second phase is in contact with the third phase. In other words, the proportion of the second phase in contact with the third phase is preferably more than 20% and less than 90%, and more preferably more than 40% and less than 75%.

[0130] By allowing the second and third phases to come into contact, the grain growth of both phases during sintering can be suppressed. Therefore, it is possible to increase the sintering temperature or extend the sintering time while maintaining the second and third phases in a finely textured state.

[0131] Therefore, the proportion of voids in the cold storage material particles can be reduced. That is, the number density of the grain boundary phase can be maintained at a higher level, and the porosity in the cold storage material particles can be reduced. Consequently, by exceeding the aforementioned lower limit value in the proportion of the second phase in contact with the third phase, the mechanical strength of the cold storage material particles is improved.

[0132] It is assumed that the second and third phases have different coefficients of thermal expansion. Therefore, when the refrigeration unit is operating and cooling from room temperature to a low temperature, stress is generated between the second and third phases due to the difference in thermal contraction. Similarly, it is assumed that the second and fourth phases have different coefficients of thermal expansion. Therefore, when the refrigeration unit is operating and cooling from room temperature to a low temperature, stress is generated between the second and fourth phases due to the difference in thermal contraction.

[0133] When the second phase is in contact with the third and fourth phases simultaneously, the second phase is simultaneously subjected to stress due to the difference in thermal contraction between it and the third and fourth phases, and each stress increases accordingly. Therefore, by keeping the proportion of the second phase in contact with the third phase below the aforementioned upper limit, the proportion of the second phase in contact with the third and fourth phases simultaneously can be reduced. As a result, the cold storage material particles 10 can suppress cracking within the particles due to the difference in thermal contraction when cooled from room temperature to low temperature during refrigerator operation.

[0134] In the cross-section of the cold storage material particle 10, the proportion of the second phase that is in contact with the third phase is preferably higher than the proportion of the second phase that is in contact with the fourth phase. By increasing the proportion of the second phase that is in contact with the third phase, the mechanical strength of the cold storage material particle 10 is improved.

[0135] The particle size of the cold storage material particles 10 is preferably 50 μm or more and 3 mm or less, more preferably 1 mm or less, and even more preferably 500 μm or less. When the particle size of the cold storage material particles 10 exceeds the aforementioned lower limit, the packing density of the cold storage material particles in the cold accumulator decreases, the pressure loss of the working medium such as helium decreases, and the refrigeration performance of the refrigerator is improved. On the other hand, when the particle size of the cold storage material particles 10 is lower than the aforementioned upper limit, the distance from the surface of the cold storage material particles to the center of the particles becomes shorter, making it easier for heat transfer between the working medium and the cold storage material particles to reach the center of the cold storage material, thus improving the refrigeration performance of the refrigerator.

[0136] The aspect ratio of the cold storage material particles 10 is preferably 5 or less, more preferably 2 or less. By ensuring that the aspect ratio of the cold storage material particles 10 is lower than the above-mentioned upper limit, the voids when the cold storage material is filled in the cold accumulator become homogeneous, thereby improving the freezing performance of the refrigerator.

[0137] By controlling the area, particle size, and contact ratio of each phase within the particle, the unevenness of the mechanical strength and thermal conductivity of the cold storage material particles can be reduced through the manufacturing method of the cold storage material particles according to the first embodiment.

[0138] According to the first embodiment, it is possible to obtain cold storage material particles with excellent properties such as high volumetric specific heat, high mechanical strength, high thermal conductivity and high heat transfer rate.

[0139] (Second Implementation) The cold storage material particles in the second embodiment do not contain a fourth phase, which differs from the cold storage material particles in the first embodiment. Hereinafter, some details that are repeated in the first embodiment will be omitted.

[0140] Figure 2 This is an explanatory diagram of the cold storage material particles according to the second embodiment. Figure 2 (a) is a schematic cross-sectional view of the cold storage material particles. Figure 2 (b) is a schematic cross-sectional view obtained by magnifying a portion of the cold storage material particles. Figure 2 (b) For example, Figure 2 (a) Schematic cross-sectional view of region R.

[0141] The cold storage material particles 20 in the second embodiment are as follows: Figure 2 As shown in (b), it includes three phases: X, Y, and Z. Phases X, Y, and Z are different phases. Phases X, Y, and Z are examples of the first, second, and third phases, respectively.

[0142] Phase X, phase Y, and phase Z can be crystalline phases, for example. Phase X, phase Y, and phase Z can also be amorphous phases, for example.

[0143] Phase X is a cold-storage material. Phase X contains cold-storage elements. For example, phase X is gadolinium oxysulfide. For example, phase X is Gd₂O₂S.

[0144] When phase X is gadolinium oxysulfide, the cold storage element is gadolinium (Gd). Phase X contains gadolinium (Gd), sulfur (S), and oxygen (O).

[0145] Phase Y contains added metal elements. The atomic concentration of the added metal elements in Phase Y is greater than that in Phase X.

[0146] The Y phase can be, for example, an oxide containing aluminum (Al). The Y phase can be, for example, aluminum oxide. The Y phase can be, for example, Al₂O₃.

[0147] When the Y phase is an oxide containing aluminum oxide, the added metal element is aluminum (Al).

[0148] The Z phase contains cold storage elements and added metal elements. Examples of Z phases include oxides containing gadolinium (Gd) and aluminum (Al). Examples of Z phases include compounds containing gadolinium (Gd), aluminum (Al), and oxygen (O). An example of a Z phase is GdAlO3.

[0149] The atomic concentration of the added metal element in the second phase is preferably greater than that in the first phase. For example, the atomic concentration of the added metal element in the Y phase is preferably greater than that in the X phase.

[0150] More than 20% and less than 90% of the second phase is preferably in contact with the third phase. For example, more than 20% and less than 90% of the Y phase is preferably in contact with the Z phase.

[0151] In the cross-section of the cold storage material particles, the area occupied by the second phase is preferably 0.001% or more and 75% or less. For example, in the cross-section of the cold storage material particles 20, the area occupied by the Y phase is preferably 0.001% or more and 75% or less.

[0152] In the cross-section of the cold storage material particles, the area of ​​each second phase is preferably 0.001 μm. 2 Above and 6000μm 2 For example, in the cross-section of the cold storage material particle 20, the area of ​​each Y phase is preferably 0.001 μm. 2 Above and 6000μm 2 the following.

[0153] In the cross-section of the cold storage material particles, the particle size of each second phase is preferably 0.1 μm or more and 100 μm or less. For example, in the cross-section of the cold storage material particles 20, the particle size of each Y phase is preferably 0.1 μm or more and 100 μm or less.

[0154] The cold storage material particles 20 of the second embodiment can be manufactured using the same manufacturing method as that of the first embodiment.

[0155] According to the second embodiment, the same as the first embodiment, it is possible to achieve cold storage material particles with excellent properties such as high volumetric specific heat, high mechanical strength, high thermal conductivity, and high heat transfer rate.

[0156] (Third Implementation) The third embodiment differs from the first embodiment in that the cold storage material particles have a first region and a second region that is closer to the outer edge of the cold storage material particles than the first region and has a higher atomic concentration of the second element than the first region. Hereinafter, some descriptions that are repeated in the first embodiment will be omitted.

[0157] Figure 3 This is an explanatory diagram of the cold storage material particles in the third embodiment. Figure 3 (a) is a schematic cross-sectional view of the cold storage material particles. Figure 3 (b) is a graph showing the atomic concentration distribution of added metal elements in the cold storage material particles.

[0158] The cold storage material particles 30 have a low-concentration region 30a (first region) and a high-concentration region 30b (second region). The atomic concentration of the added metal element in the high-concentration region 30b is higher than that in the low-concentration region 30a.

[0159] The high-concentration region 30b is closer to the outer edge of the cold storage material particles 30 compared to the low-concentration region 30a. The high-concentration region 30b surrounds the low-concentration region 30a. The low-concentration region 30a is, for example, the region containing the center of the cold storage material particles 30, while the high-concentration region 30b is the region surrounding the low-concentration region 30a.

[0160] Both the low-concentration region 30a and the high-concentration region 30b contain cold-storage elements. At least in the high-concentration region 30b, the cold-storage elements are mixed with added metal elements. Alternatively, a structure can be made in which the low-concentration region 30a does not contain added metal elements.

[0161] In the high-concentration region 30b, the atomic concentration of the added metal element is, for example, 0.1 atomic% or more and 2.0 atomic% or less.

[0162] The atomic concentration of the added metal element in the high-concentration region 30b is, for example, more than 1.03 times and less than 10 times the atomic concentration of the added metal element in the low-concentration region 30a. The distance from the outer edge of the cold storage material particle 30 to the high-concentration region 30b, where the atomic concentration of the added metal element in the high-concentration region 30b is more than 1.03 times that in the low-concentration region 30a, is... Figure 3 (b) d) is, for example, more than 1 / 20 of the particle size D of the cold storage material particles 30.

[0163] The distance from the outer edge of the cold storage material particle 30 up to the position where the atomic concentration of the added metal element is more than 1.03 times that of the low concentration region 30a. Figure 3 (b) d) is, for example, 10 μm or more.

[0164] The atomic concentration of the added metal element decreases monotonically from the outer edge of the cold storage material particle 30 toward the center.

[0165] The detection of added metal elements contained in the cold storage material particles 30 and the determination of the atomic concentration of the added metal elements can be performed, for example, by using WDX. For example, by measuring the concentration of added metal elements at multiple locations from the outer edge of the cold storage material particles 30 toward the center using WDX, it is possible to determine whether there is a high-concentration region 30b near the outer edge of the cold storage material particles 30, determine the atomic concentration of added metal elements in the high-concentration region 30b, determine the ratio of the atomic concentration of added metal elements in the high-concentration region 30b to the atomic concentration of added metal elements in the low-concentration region 30a, and measure the distance from the outer edge of the cold storage material particles 30 to the position where the atomic concentration of added metal elements is more than 1.03 times that of added metal elements in the low-concentration region 30a. Figure 3 (b) d) is calculated. In addition, for example, by plotting the atomic concentration of the added metal element in the cold storage material particles 30 by WDX, it is possible to identify whether the high concentration region 30b surrounds the low concentration region 30a.

[0166] The cold storage material particles 30 of the third embodiment can be manufactured using the same manufacturing method as that of the first embodiment.

[0167] When manufacturing the cold storage material particles 30 of the third embodiment, the atomic concentration distribution of the added metal element in the particles is controlled, for example, by controlling the gelation time. That is, by controlling the gelation time, a distribution is formed in which the atomic concentration of the added metal element is low in the central region of the particles and high in the peripheral region of the particles.

[0168] From the viewpoint of forming the above distribution, the gelation time is preferably as short as possible to prevent the particle shape from disintegrating in subsequent processes. The gelation time is preferably within 1 hour, more preferably within 30 minutes.

[0169] Next, the function and effect of the cold storage material particles 30 in the third embodiment will be explained.

[0170] The cold storage material particles 30 of the third embodiment have a high-concentration region 30b in the outer peripheral region of the particles, where the atomic concentration of the added metal element is high. The added metal element promotes the sintering of the particles during manufacturing. Therefore, the high-concentration region 30b has a high degree of sintering and high mechanical strength. Consequently, the cold storage material particles 30 possess high mechanical strength.

[0171] Furthermore, due to the high degree of sintering, the high-concentration region 30b exhibits higher thermal conductivity and heat transfer efficiency. Therefore, the cold storage material particles 30 possess both high thermal conductivity and high heat transfer efficiency.

[0172] If the atomic concentration of the added metal element increases, the degree of sintering of the particles increases. On the other hand, due to the increased volume proportion of the added metal element, there is a problem of a decrease in the volume proportion of the cold storage material. Furthermore, the added metal element reacts with the cold storage material to form compounds with low volumetric specific heat. Therefore, if the atomic concentration of the added metal element increases, the cold storage material may transform into a compound with low volumetric specific heat, thus reducing the volume proportion of the cold storage material.

[0173] The cold storage material particles 30 of the third embodiment have a low-concentration region 30a in the central region of the particles, where the atomic concentration of the added metal element is low. Therefore, the decrease in the volume ratio of the cold storage material caused by the addition of the metal element is suppressed in the central region of the particles. Therefore, the cold storage material particles 30 have a high volumetric specific heat.

[0174] The cold storage material particles 30 of the third embodiment improve mechanical strength, thermal conductivity, and heat transfer rate by having a high-concentration region 30b with a high atomic concentration of added metal elements in the outer peripheral region of the particles. On the other hand, by having a low-concentration region 30a in the central region of the particles, the volumetric specific heat is improved. The cold storage material particles 30 of the third embodiment achieve high volumetric specific heat, high mechanical strength, high thermal conductivity, and high heat transfer rate by optimizing the concentration distribution of added elements in the particles.

[0175] The atomic concentration of the added metal element in the high-concentration region 30b is preferably 0.1 atomic% or more, more preferably 0.2 atomic% or more. This can improve the mechanical strength, thermal conductivity, and heat transfer rate of the cold storage material particles 30.

[0176] The atomic concentration of the added metal element in the high-concentration region 30b is preferably 1.03 times or more than the atomic concentration of the added metal element in the low-concentration region 30a, more preferably 1.05 times or more, even more preferably 1.1 times or more, and most preferably 1.2 times or more. This enables the cold storage material particles 30 to achieve high mechanical strength, high thermal conductivity, high heat transfer rate, and high volumetric specific heat.

[0177] The distance from the outer edge of the cold storage material particle 30 up to the position where the atomic concentration of the added metal element is more than 1.03 times that of the added metal concentration in the low concentration region 30a. Figure 3 (b) d) is preferably the particle size D of the cold storage material particles 30. Figure 3 The value of D in (a) is more than 1 / 20, and more preferably more than 1 / 10. This can improve the mechanical strength, thermal conductivity and heat transfer rate of the cold storage material particles 30.

[0178] The distance from the outer edge of the cold storage material particle 30 up to the position where the atomic concentration of the added metal element is more than 1.03 times that of the added metal concentration in the low concentration region 30a. Figure 3 In (b), d) is preferably 10 μm or more, more preferably 20 μm or more. This can improve the mechanical strength, thermal conductivity and heat transfer rate of the cold storage material particles 30.

[0179] From the viewpoint of achieving high mechanical strength, high thermal conductivity, high heat transfer rate and high volumetric specific heat of the cold storage material particles 30, the concentration of added metal is preferably monotonically reduced from the outer edge of the cold storage material particles 30 toward the center.

[0180] According to the third embodiment, it is possible to obtain cold storage material particles with excellent properties such as high volumetric specific heat, high mechanical strength, high thermal conductivity and high heat transfer rate.

[0181] (Fourth Implementation) The refrigerator of the fourth embodiment is a refrigerator equipped with a cold storage tank filled with a plurality of cold storage material particles of the first embodiment. Hereinafter, some descriptions that are repeated with the first embodiment will be omitted.

[0182] Figure 4 This is a schematic cross-sectional view showing the main components of a GM cryostat, an example of a cryostat according to the fourth embodiment. The cryostat of the fourth embodiment is a two-stage cryogenic storage cryostat 100 used for cooling superconducting devices, etc. In addition to the GM cryostat described above, the cryostat filled with a plurality of cryogenic storage material particles of the first embodiment can also be a Stirling cryostat, a pulse tube cryostat, etc.

[0183] The cryogenic storage type cryogenic refrigerator 100 includes a first cylinder 111, a second cylinder 112, a vacuum container 113, a first accumulator 114, a second accumulator 115, a first sealing ring 116, a second sealing ring 117, a first cryogenic storage material 118, a second cryogenic storage material 119, a first expansion chamber 120, a second expansion chamber 121, a first cooling platform 122, a second cooling platform 123, and a compressor 124.

[0184] The cryogenic cryogenic freezer 100 has a vacuum container 113 equipped with a large-diameter first cylinder 111 and a small-diameter second cylinder 112 coaxially connected to the first cylinder 111. A first accumulator 114 is flexibly disposed in the first cylinder 111. A second accumulator 115, which is an example of an accumulator according to a fourth embodiment, is flexibly disposed in the second cylinder 112.

[0185] A first sealing ring 116 is disposed between the first cylinder 111 and the first accumulator 114. A second sealing ring 117 is disposed between the second cylinder 112 and the second accumulator 115.

[0186] The first cold storage unit 114 contains a first cold storage material 118, such as a Cu mesh. The second cold storage unit 115 is filled with a plurality of cold storage material particles 10 of the first embodiment as a second cold storage material 119.

[0187] The second cold storage unit 115 can also be separated by a metal mesh and has multiple cold storage material filling layers. When the second cold storage unit 115 is divided into multiple filling layers, at least one filling layer is filled with a group of cold storage material particles formed by multiple cold storage material particles of the first embodiment, for example, combined with at least one cold storage material particle group selected from lead cold storage material particle group, bismuth cold storage material particle group, tin cold storage material particle group, holmium copper cold storage material particle group, erbium nickel cold storage material particle group, erbium cobalt cold storage material particle group and gadolinium aluminum oxide cold storage material particle group.

[0188] In the combination of cold storage materials, the cold storage materials with higher peak specific heat temperature are set as the first cold storage material particle group, and the cold storage materials with lower peak specific heat temperature are set as the second cold storage material particle group, and they are combined in order of decreasing peak specific heat temperature.

[0189] In the case of a two-layer type, examples include using a holmium copper cold storage material particle group in the first cold storage material particle group and a combination of using the cold storage material particle group of the first embodiment in the second cold storage material particle group. Furthermore, in the case of a three-layer type, examples include using at least one cold storage material particle group selected from lead, bismuth, and tin as the first cold storage material particle group, using a holmium copper cold storage material particle group as the second cold storage material particle group, and a combination of using the cold storage material particle group of the first embodiment as the third cold storage material particle group.

[0190] Holmium copper cold storage material particles are preferably, for example, HoCu2 or HoCu. Erbium nickel cold storage material particles are preferably, for example, ErNi or Er3Ni.

[0191] The first cold accumulator 114 and the second cold accumulator 115 each have a passage for a working medium disposed in the gaps between the first cold storage material 118 and the second cold storage material 119. The working medium is helium.

[0192] A first expansion chamber 120 is provided between the first accumulator 114 and the second accumulator 115. Furthermore, a second expansion chamber 121 is provided between the second accumulator 115 and the front end wall of the second cylinder 112. A first cooling platform 122 is provided at the bottom of the first expansion chamber 120. Additionally, a second cooling platform 123, which is at a lower temperature than the first cooling platform 122, is formed at the bottom of the second expansion chamber 121.

[0193] For the aforementioned two-stage cryogenic storage refrigerator 100, a high-pressure working medium is supplied from the compressor 124. The supplied working medium passes through the space between the first cryogenic storage materials 118 contained in the first cryogenic storage unit 114 and then passes through the space between the second cryogenic storage materials 119 contained in the second cryogenic storage unit 115 and then passes through the space between the second cryogenic storage materials 119 ...

[0194] At this time, the working medium supplies heat energy to the first cold storage material 118 and the second cold storage material 119, thereby cooling them. The working medium 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, generating cold. Then, the first cooling platform 122 and the second cooling platform 123 are cooled.

[0195] The expanded working medium flows in opposite directions between the first cold storage material 118 and the second cold storage material 119. After absorbing heat energy from the first cold storage material 118 and the second cold storage material 119, the working medium is discharged. The cold storage type cryogenic refrigerator 100 is configured such that the thermal efficiency of the working medium circulation increases as the reheating effect becomes better in this process, and a lower temperature is achieved.

[0196] By utilizing the refrigeration unit of the fourth embodiment in maglev trains, helium recondensation devices, etc., the long-term reliability of maglev trains and helium recondensation devices can be improved.

[0197] It should be noted that the cold storage material particles of the second embodiment or the third embodiment can also be used as the second cold storage material 119.

[0198] According to the fourth embodiment, by using cold storage material particles with excellent properties, a refrigerator with excellent properties can be achieved.

[0199] (Fifth implementation method) The cryogenic pump of the fifth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0200] Figure 5 This is a cross-sectional view showing the schematic configuration of the cryogenic pump according to the fifth embodiment. The cryogenic pump of the fifth embodiment is a cryogenic pump 500 equipped with the cold storage type ultra-low temperature freezer 100 of the fourth embodiment.

[0201] The cryogenic pump 500 includes a cryogenic panel 501 for condensing or adsorbing gas molecules, a cold storage type cryogenic freezer 100 for cooling the cryogenic panel 501 to a specified extremely low temperature, a shielding plate 503 disposed between the cryogenic panel 501 and the cold storage type cryogenic freezer 100, a baffle 504 disposed at the intake port, and a ring 505 for changing the exhaust speed of argon, nitrogen, hydrogen, etc.

[0202] According to the fifth embodiment, a cryogenic pump with excellent characteristics can be achieved by using a refrigeration unit with superior characteristics. Furthermore, by utilizing the cryogenic pump of the fifth embodiment in semiconductor manufacturing apparatuses, the long-term reliability of the semiconductor manufacturing apparatus can be improved, and the frequency of maintenance of the semiconductor manufacturing apparatus can be reduced. As a result, it contributes to improving the quality of the manufactured semiconductors and reducing manufacturing costs.

[0203] (Sixth Implementation Method) The superconducting magnet of the sixth embodiment includes the cryostat of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0204] Figure 6This is a perspective view showing the schematic configuration of the superconducting magnet according to the sixth embodiment. The superconducting magnet of the sixth embodiment is a superconducting magnet 600 for a maglev train equipped with the cryogenic storage type cryogenic refrigerator 100 of the fourth embodiment.

[0205] The superconducting magnet 600 for maglev trains includes a superconducting coil 601, a liquid helium tank 602 for cooling the superconducting coil 601, a liquid nitrogen tank 603 to prevent the evaporation of liquid helium, a laminated insulation material 605, a power lead wire 606, a permanent current switch 607, and a cryogenic storage type cryogenic freezer 100.

[0206] According to the sixth embodiment, a superconducting magnet with excellent properties can be achieved by using a cryostat with excellent properties.

[0207] (Seventh Implementation) The magnetic resonance imaging apparatus of the seventh embodiment includes the cryostat of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0208] Figure 7 This is a cross-sectional view showing the schematic configuration of the magnetic resonance imaging (MRI) apparatus according to the seventh embodiment. The magnetic resonance imaging (MRI) apparatus of the seventh embodiment is an MRI apparatus 700 equipped with the cryogenic cryostat 100 of the fourth embodiment.

[0209] The magnetic resonance imaging device 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 for non-uniformity of the generated magnetic field, a tilting magnetic field coil 702 that applies a magnetic field gradient to the measurement area, a radio wave transceiver probe 703, a cryostat 705, and a radiation-insulating shield 706. Furthermore, a cryogenic storage type cryogenic freezer 100 is used for cooling the superconducting static magnetic field coil 701.

[0210] According to the seventh embodiment, a magnetic resonance imaging device with excellent characteristics can be realized by using a cryostat with excellent characteristics.

[0211] (Eighth Implementation) The nuclear magnetic resonance apparatus of the eighth embodiment includes the cryostat of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0212] Figure 8 This is a cross-sectional view showing the schematic configuration of the nuclear magnetic resonance (NMR) apparatus according to the eighth embodiment. The nuclear magnetic resonance (NMR) apparatus of the eighth embodiment is an NMR apparatus 800 equipped with the cryogenic cryogenic freezer 100 of the fourth embodiment.

[0213] 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 substance placed in a sample tube 801, a high-frequency oscillator 803 that applies radio waves to the sample tube 801 in the magnetic field, and an amplifier 804 that amplifies the induced current generated in a coil (not shown) around the sample tube 801. Furthermore, it includes a cryogenic storage cryostat 100 for cooling the superconducting static magnetic field coil 802.

[0214] According to the eighth embodiment, a nuclear magnetic resonance device with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0215] (Ninth Implementation) The magnetic field-applied single crystal pulling apparatus of the ninth embodiment includes the cryostat of the fourth embodiment. Hereinafter, some descriptions that are repeated in the fourth embodiment will be omitted.

[0216] Figure 9 This is a perspective view showing the schematic configuration of the magnetic field applied single crystal pulling device according to the ninth embodiment. The magnetic field applied single crystal pulling device of the ninth embodiment is a magnetic field applied single crystal pulling device 900 equipped with the cold storage type ultra-low temperature freezer 100 of the ninth embodiment.

[0217] The magnetic field-applied single crystal pulling device 900 includes a single crystal pulling section 901 with a raw material melting crucible, a heater, and a single crystal pulling mechanism; a superconducting coil 902 that applies a static magnetic field to the molten raw material; a lifting mechanism 903 for the single crystal pulling section 901; current leads 905; a heat insulation plate 906; and a helium container 907. Furthermore, a cryogenic storage type cryogenic freezer 100 is used for cooling the superconducting coil 902.

[0218] According to the ninth embodiment, a magnetic field-applied single crystal pulling device with excellent characteristics can be realized by using a cryostat with excellent characteristics.

[0219] It should be noted that the refrigeration unit of the fourth embodiment can improve long-term reliability by utilizing it in magnetic levitation trains, helium recondensation devices, etc.

[0220] Example The following describes examples, comparative examples, and evaluation results of the cold storage material particles of the first to third embodiments.

[0221] The composition and evaluation results of the cold storage material particles of Examples 1 to 77 and Comparative Examples 1 to 7 are shown in Tables 1 to 7.

[0222] (Example 1) As a raw material for the cold storage substance, gadolinium oxide powder was added to an aqueous solution of sodium alginate and mixed to form a slurry. Alumina was also added to the slurry. The mixing time was set to 12 hours.

[0223] A slurry containing a cold-storing substance was dropwise added to an aqueous solution of calcium lactate, which served as a gelling solution. The slurry was added using a syringe. The nozzle diameter of the syringe was set to 510 μm, and the distance from the tip of the syringe to the surface of the calcium lactate aqueous solution was set to 100 mm.

[0224] The slurry was kept in the gelation solution for 5 hours.

[0225] Next, the gelled particles are washed with pure water. After washing, the particles are dried. After drying, the particles undergo vulcanization and sintering.

[0226] The particles are sulfided by heat treatment at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (H2S). The particles are then sintered by heat treatment at 1300°C for 12 hours in a pressurized atmosphere containing an inert gas.

[0227] The cold storage material particles in Example 1 are spherical.

[0228] The cold storage material particles in Example 1 contain gadolinium oxysulfide as the cold storage substance, with gadolinium (Gd) as the first element and calcium (Ca) and aluminum (Al) as the second elements. The calcium concentration in the cold storage material particles of Example 1 is 0.12 atomic%. In addition, the aluminum concentration in the cold storage material particles is 23.3 atomic%.

[0229] The concentration ratio (C2 / C1) of the second element in the second region of the cold storage material particles relative to the atomic concentration (C1) of the second element in the first region is 1. That is, C2 / C1=1.

[0230] It should be noted that in the following examples and comparative examples, the mixing time of the raw material powder and the alginate aqueous solution, the holding time of the slurry in the gelation solution (gelation time), the conditions of the sulfidation heat treatment, and the conditions of the sintering heat treatment are adjusted in a way that makes them suitable.

[0231] (Example 2) In addition to aluminum oxide, magnesium oxide was also used. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0232] (Example 3) Aluminum chloride was used as the gelling solution, and the cold storage material particles were otherwise manufactured in the same manner as in Example 1.

[0233] (Example 4) Magnesium sulfate aqueous solution was used as the gelling solution, and the cold storage material particles were otherwise manufactured in the same manner as in Example 1.

[0234] (Example 5) A beryllium sulfate aqueous solution was used as the gelling solution, and the cold storage material particles were otherwise manufactured in the same manner as in Example 1.

[0235] (Example 6) As the gelling solution, an aqueous solution of strontium nitrate was used. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0236] (Example 7) A barium chloride aqueous solution was used as the gelling solution. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0237] (Example 8) As the gelling solution, an aqueous solution of manganese chloride was used. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0238] (Example 9) As the gelling solution, an aqueous solution of ferric chloride was used. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0239] (Example 10) A copper chloride aqueous solution was used as the gelling solution. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0240] (Example 11) As the gelling solution, an aqueous solution of nickel chloride was used. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0241] (Example 12) As the gelling solution, an aqueous solution of cobalt chloride was used. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0242] (Example 13) The cold storage material particles were manufactured by replacing a portion of the gadolinium in the cold storage element with yttrium (Y); increasing the weight of the raw material powder of the cold storage substance in the slurry; and not using alumina.

[0243] (Example 14) A portion of the gadolinium in the cold storage element was replaced with cerium (Ce); the weight of the raw material powder of the cold storage substance in the slurry was increased; and alumina was not used; magnesium chloride was used as the gelling solution. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0244] (Example 15) A portion of the gadolinium in the cold storage element was replaced with praseodymium (Pr); the weight of the raw material powder of the cold storage substance in the slurry was increased; and alumina was not used; an aqueous solution of beryllium sulfate was used as the gelling solution. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0245] (Example 16) A portion of the gadolinium in the cold storage element was replaced with neodymium (Nd); the weight of the raw material powder of the cold storage substance in the slurry was increased; and alumina was not used; an aqueous solution of strontium nitrate was used as the gelling solution. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0246] (Example 17) A portion of the gadolinium in the cold storage element was replaced with promethium (Pm); the weight of the raw material powder of the cold storage substance in the slurry was increased; and alumina was not used; barium chloride aqueous solution was used as the gelling solution. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0247] (Example 18) A portion of the gadolinium in the cold storage element was replaced with samarium (Sm); aluminum oxide was not used; and an aqueous solution of manganese chloride was used as the gelling solution. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0248] (Example 19) A portion of the gadolinium in the cold storage element was replaced with europium (Eu); aluminum oxide was not used; an aqueous solution of aluminum chloride was used as the gelling solution; otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0249] (Example 20) A portion of the gadolinium in the cold storage element was replaced with terbium; aluminum oxide was not used; and an aqueous solution of ferric chloride was used as the gelling solution. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0250] (Examples 21-26) A portion of the gadolinium (Gd) in the cold storage element was replaced with dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), or lutetium (Lu); the weight of the raw material powder of the cold storage material in the slurry was reduced; alumina was not used; aqueous solutions of copper chloride, nickel chloride, cobalt chloride, calcium chloride, or magnesium chloride were used as the gelling solution. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1.

[0251] (Example 27) The cold storage material particles in Example 27 differ from those in Example 3 in that the added metal element is strontium (Sr).

[0252] (Example 28) The cold storage material particles in Example 28 have a higher concentration of aluminum (Al) particles than those in Example 3.

[0253] (Example 29) The concentration ratio (C2 / C1) of the added metal element in the second region of the cold storage material particles in Example 29 to the added metal element in the first region is 1.03, which is different from the cold storage material particles in Example 1.

[0254] The cold storage material particles of Example 29 were manufactured using the same method as those of Example 1, but with a shorter gelation time compared to that of Example 1.

[0255] (Example 30) The concentration ratio (C2 / C1) of the added metal element in the second region of the cold storage material particles in Example 30 to the added metal element in the first region is 1.05, which is different from the cold storage material particles in Example 29.

[0256] In manufacturing the cold storage material particles of Example 30, the gelation time was shortened compared to the case of manufacturing the cold storage material particles of Example 29.

[0257] (Example 31) The concentration ratio (C2 / C1) of the added metal element in the second region of the cold storage material particles in Example 31 to the added metal element in the first region is 1.1, which is different from the cold storage material particles in Example 29.

[0258] In manufacturing the cold storage material particles of Example 31, the gelation time was shortened compared to the case of manufacturing the cold storage material particles of Example 30.

[0259] (Example 32) The cold storage material particles of Example 32 differ from those of Example 1 in that they contain silver oxide as the cold storage substance and silver (Ag) as the cold storage element. Furthermore, they differ from those of Example 1 in that they contain magnesium (Mg) as an added metal element and do not contain aluminum (Al) as an added metal element. The cold storage material particles of Example 32 contain both Ag-O and Ag-Mg-O phases.

[0260] (Example 33) The cold storage material particles of Example 32 differ from those of Example 1 in that they contain silver oxide as the cold storage substance and silver (Ag) as the cold storage element. Furthermore, they do not contain aluminum (Al) as the added metal element, unlike the cold storage material particles of Example 1. The cold storage material particles of Example 33 contain both Ag-O and Ag-Ca-O phases.

[0261] (Example 34) The cold storage material particles of Example 34 differ from those of Example 1 in that they contain copper oxide as the cold storage substance and copper (Cu) as the cold storage element. Furthermore, they differ from those of Example 1 in that they contain strontium (Sr) as an added metal element and do not contain aluminum (Al) as an added metal element. The cold storage material particles of Example 34 contain both Cu-O and Cu-Sr-O phases.

[0262] (Example 35) The cold storage material particles of Example 35 differ from those of Example 1 in that they contain copper oxide as the cold storage substance and copper (Cu) as the cold storage element. Furthermore, they differ from those of Example 1 in that they contain barium (Ba) as an added metal element and do not contain aluminum (Al) as an added metal element. The cold storage material particles of Example 34 contain Cu-O and Cu-Ba-O phases.

[0263] (Examples 36-41) The area and particle size of each second phase in the cross-section of the cold storage material particles in Examples 36-41 are different from those in Example 1. In manufacturing the cold storage material particles of Examples 36-41, the sintering temperature and sintering time were changed compared to the manufacturing of the cold storage material particles of Example 1.

[0264] (Examples 42-50) The proportions of the second phase in contact with the third phase and the proportions of the second phase in contact with the fourth phase in the cross-section of the cold storage material particles in Examples 42-50 differ from those in the cold storage material particles of Example 1. In manufacturing the cold storage material particles of Examples 42-50, the mixing time between the raw material powder and the alginate aqueous solution was changed compared to the manufacturing process of the cold storage material particles of Example 1.

[0265] (Examples 51-56) The particle size or aspect ratio of the cold storage material particles in Examples 51-56 are different from those in Example 1. In manufacturing the cold storage material particles of Examples 51-56, the nozzle diameter of the syringe and the distance from the tip of the syringe to the surface of the gelled solution were changed compared to the manufacturing of the cold storage material particles of Example 1.

[0266] (Examples 57-59) Terbium oxide, holmium oxide, and dysprosium oxide were used instead of gadolinium oxide, and otherwise the same procedure was followed as in Example 3 to produce the cold storage material particles.

[0267] (Example 60) Instead of a syringe, an air pulse dispenser was used for adding the slurry. Otherwise, the cold storage material particles were produced in the same manner as in Example 1. The piston rod was driven up and down for 10 ms per cycle, the nozzle outlet diameter was set to 510 μm, and the distance from the nozzle tip to the surface of the calcium lactate aqueous solution was set to 100 mm. At this time, the particle production rate was 100 particles / second, which is an improvement compared to adding the slurry with a syringe.

[0268] In the following embodiments, the particle size is adjusted by adjusting the mixing time of the raw material powder and the alginate aqueous solution, the slurry viscosity, the holding time of the slurry in the gelation solution (gelation time), the conditions of the sulfidation heat treatment, the conditions of the sintering heat treatment, the time of driving the piston rod up and down, the hydraulic pressure, the nozzle outlet diameter, and the distance from the tip of the nozzle to the surface of the calcium lactate aqueous solution.

[0269] (Example 61) In addition to aluminum oxide, magnesium oxide was also used. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 60.

[0270] (Example 62) Aluminum chloride was used as the gelling solution, and the cold storage material particles were otherwise manufactured in the same manner as in Example 60.

[0271] (Examples 63-65) Terbium oxide, holmium oxide, and dysprosium oxide were used instead of gadolinium oxide, and otherwise the same operation as in Example 60 was performed to produce the cold storage material particles.

[0272] (Example 66) As for the slurry dripping method, a piezoelectric dispenser was used instead of a syringe. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1. The piston rod was driven up and down for 10 ms per cycle, the nozzle outlet diameter was set to 510 μm, and the distance from the nozzle tip to the surface of the calcium lactate aqueous solution was set to 100 mm. At this time, the particle manufacturing rate was 100 particles / second, which is an improvement compared to the dripping method using a syringe.

[0273] It should be noted that, in the following embodiments, the particle size is adjusted by adjusting the mixing time of the raw material powder and the alginate aqueous solution, the slurry viscosity, the holding time of the slurry in the gelation solution (gelation time), the conditions of the vulcanization heat treatment, the conditions of the sintering heat treatment, the time of the piston rod driving up and down, the hydraulic pressure, the nozzle outlet diameter, and the distance from the front end of the nozzle to the surface of the calcium lactate aqueous solution.

[0274] (Example 67) In addition to aluminum oxide, magnesium oxide was also used. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 66.

[0275] (Example 68) Aluminum chloride was used as the gelling solution, and the cold storage material particles were otherwise manufactured in the same manner as in Example 66.

[0276] (Examples 69-71) Terbium oxide, holmium oxide, and dysprosium oxide were used instead of gadolinium oxide, and otherwise the same operation as in Example 66 was performed to produce the cold storage material particles.

[0277] (Example 72) As for the slurry droplet addition method, a continuous inkjet printer was used instead of a syringe. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 1. By appropriately controlling the waveform of the pressure wave applied to the liquid column, the particle manufacturing speed was set to 500 particles / second. This manufacturing speed is improved compared to the manufacturing speed when using a syringe for droplet addition. The nozzle outlet diameter was set to 510 μm, and the distance from the nozzle tip to the surface of the calcium lactate aqueous solution was set to 100 mm.

[0278] It should be noted that in the following embodiments, the particle size is adjusted by adjusting the mixing time of the raw material powder and the alginate aqueous solution, the slurry viscosity, the holding time of the slurry in the gelation solution (gelation time), the conditions of the vulcanization heat treatment, the conditions of the sintering heat treatment, the particle manufacturing speed, the hydraulic pressure, the nozzle outlet diameter, and the distance from the nozzle tip to the surface of the calcium lactate aqueous solution.

[0279] (Example 73) In addition to aluminum oxide, magnesium oxide was also used. Otherwise, the cold storage material particles were manufactured in the same manner as in Example 72.

[0280] (Example 74) Aluminum chloride was used as the gelling solution, and the cold storage material particles were otherwise manufactured in the same manner as in Example 72.

[0281] (Examples 75-77) Terbium oxide, holmium oxide, and dysprosium oxide were used instead of gadolinium oxide, and otherwise the same operation as in Example 72 was performed to produce the cold storage material particles.

[0282] (Comparative Example 1) The cold storage material particles of Comparative Example 1 have an aluminum (Al) atomic concentration of as low as 0.0008 atomic% in the particles, which differs from the cold storage material particles of Example 3. In manufacturing the cold storage material particles of Comparative Example 1, compared to manufacturing the cold storage material particles of Example 3, the weight of the raw material powder of the cold storage substance in the slurry was increased, and alumina was not used in the slurry.

[0283] (Comparative Example 2) The cold storage material particles of Comparative Example 2 differ from those of Example 3 in that they do not contain aluminum (Al) and the atomic concentration of calcium (Ca) in the particles is as high as 47 atomic%. In manufacturing the cold storage material particles of Comparative Example 2, compared with the case of manufacturing the cold storage material particles of Example 1, the weight of the raw material powder of the cold storage substance in the slurry is reduced, and alumina is not used in the slurry.

[0284] (Comparative Example 3) The cold storage material particles of Comparative Example 3 differ from those of Example 1 in that they do not contain aluminum (Al) and the atomic concentration of calcium (Ca) in the particles is as high as 61 atomic%. In manufacturing the cold storage material particles of Comparative Example 3, compared with the manufacturing of the cold storage material particles of Example 1, the weight of the raw material powder of the cold storage substance in the slurry was reduced, aluminum oxide was not used in the slurry, and an aqueous solution of copper chloride was used as the gelling solution.

[0285] (Comparative Example 4) The cold storage material particles of Comparative Example 4 differ from those of Example 1 in that they do not contain aluminum (Al) and the atomic concentration of beryllium (Be) in the particles is as low as 0.0005 atomic%. In manufacturing the cold storage material particles of Comparative Example 4, compared to manufacturing the cold storage material particles of Example 32, the weight of the raw material powder of the cold storage substance in the slurry was increased, and an aqueous solution of beryllium sulfate was used as the gelling solution.

[0286] (Comparative Example 5) The cold storage material particles of Comparative Example 5 have an atomic concentration of up to 37 atomic% of calcium (Ca) in the particles, which differs from the cold storage material particles of Example 33. In manufacturing the cold storage material particles of Comparative Example 5, the weight of the raw material powder of the cold storage substance in the slurry was reduced compared to the case of manufacturing the cold storage material particles of Example 33.

[0287] (Comparative Example 6) The cold storage material particles of Comparative Example 6 differ from those of Example 1 in that they do not contain aluminum (Al) and the atomic concentration of iron (Fe) in the particles is as low as 0.0005 atomic%. In manufacturing the cold storage material particles of Comparative Example 6, compared to manufacturing the cold storage material particles of Example 34, the weight of the raw material powder of the cold storage substance in the slurry was increased, and an aqueous solution of ferric chloride was used as the gelling solution.

[0288] (Comparative Example 7) The cold storage material particles of Comparative Example 7 have an atomic concentration of up to 40 atomic% of manganese (Mn) in the particles, which differs from the cold storage material particles of Example 35. In manufacturing the cold storage material particles of Comparative Example 7, compared to manufacturing the cold storage material particles of Example 35, the weight of the raw material powder of the cold storage substance in the slurry was reduced, and an aqueous solution of manganese chloride was used as the gelling solution.

[0289] For the manufactured cold storage material particles, the maximum volumetric specific heat at below 20 K was measured. The results are shown in Tables 1 to 7.

[0290] The required mechanical strength of the cold storage material particles was evaluated while the refrigeration unit was operating and the cold storage material particles were filled into the cold storage tank of a refrigeration unit. The manufactured cold storage material particles were filled into cylindrical containers with a diameter of 15 mm and a height of 5 mm. The cold storage material particles were fixed in the cylindrical containers, and a sufficient amount of particles was filled to prevent them from moving freely. A strength of 1 × 10⁻⁶ particles was applied to each container. 6 Second and 1×10 7 The amplitude of the second wave is 2mm, and the maximum acceleration is 400m / s². 2 The single vibration. As a result, the proportion of damaged cold storage material particles is shown in Tables 1 to 7.

[0291] The required mechanical strength of the cryogenic material particles was evaluated while the refrigeration unit was operating and the cryogenic material particles were filled with cryogenic material. Furthermore, the required tolerance to temperature changes of the cryogenic material particles was also evaluated when the temperature of the cryogenic material fluctuated between room temperature and extremely low temperatures before and after the operation of the refrigeration unit. The manufactured cryogenic material particles were filled into cylindrical containers with a diameter of 15 mm and a height of 5 mm. The cryogenic material particles were fixed in the cylindrical containers, and a sufficient amount of particles was filled to prevent free movement. After filling, the cylindrical containers were cooled from room temperature to liquid helium temperature and then restored to room temperature. Next, the containers were subjected to a 1×10⁻⁶ test. 4 The amplitude of the second wave is 2 mm, and the maximum acceleration is 400 m / s². 2 The single vibration. As a result, the proportion of damaged cold storage material particles is shown in the table.

[0292] The thermal conductivity and freezing capacity of the cold storage material particles at 4.2 K are shown in the table. The freezing capacity was investigated using a two-stage GM refrigeration unit with a power consumption of 3.4 kW. A Cu mesh was contained in the first cold storage unit, lead (Pb) was filled as the cold storage material in the first layer on the high-temperature side of the second cold storage unit, HoCu2 was filled as the cold storage material in the second layer, and the cold storage material particles of the evaluation object were filled in the low-temperature side of the third layer.

[0293] It was found that if the atomic concentration of the added metal element in the cold storage material particles becomes greater than 60 atomic%, as in Comparative Example 3, the maximum value of the volumetric specific heat becomes smaller, even lower than 0.3. This is believed to be because the proportion of cold storage material in the cold storage material particles decreases due to the increased proportion of added metal element.

[0294] If the atomic concentration of the added metal element in the cold storage material particles becomes less than 0.001 atomic%, as in Comparative Examples 1, 4, and 6, the proportion of damaged cold storage material particles increases to more than 5 wt%. This is believed to be due to insufficient sintering of the cold storage material particles caused by the low atomic concentration of the added metal element.

[0295] 1×10 will be given 7 The proportion of destructive particles during single vibration was compared between Examples 1 to 12. Examples 1 and 2, which contained calcium (Ca) as an added metal element, had a lower proportion of destructive particles. This is believed to be due to the particularly high ability of calcium (Ca) to promote the sintering of the cold storage material particles.

[0296] Furthermore, if, as in Examples 29-31, the concentration ratio (C2 / C1) of the added metal element in the second region relative to the atomic concentration (C1) of the added metal element in the first region becomes greater than 1, then the maximum value of the volumetric specific heat increases. This is believed to be due to the increased proportion of the cold-storing material in the center of the cold-storing material particles.

[0297] As shown in Tables 1 to 7, if the proportion of the second phase in the cross-section of the cold storage material particles exceeds 0.001%, the proportion of damaged cold storage material particles decreases sharply. If the proportion of the second phase in the cross-section exceeds 0.001%, the mechanical strength increases.

[0298] On the other hand, it was shown that if the proportion of the second phase in the cross-section of the cold storage material particles is less than 75%, the maximum volumetric specific heat below 20 K increases. By controlling the proportion of the second phase in this way, cold storage material particles with high thermal conductivity and high strength can be provided.

[0299] As shown in Tables 1 to 7, if the area of ​​each second phase in the cross-section of the cold storage material particles exceeds 0.001 μm... 2 Then the thermal conductivity is significantly improved. On the other hand, if the area of ​​each second phase in the cross-section of the cold storage material particles is less than 6000 μm... 2 Then give 1×10 7 The proportion of damaged cold storage material particles after a single vibration is significantly reduced. It is known that if the area of ​​each second phase in the cross-section of the cold storage material particles is less than 6000 μm... 2 This increases the mechanical strength of the cold storage material particles. By controlling the area of ​​each phase in this way, it is possible to provide cold storage material particles with high thermal conductivity and high strength.

[0300] Tables 1-7 show that if the particle size of each second phase in the cross-section of the cold storage material particles exceeds 0.1 μm, the thermal conductivity is significantly improved. Conversely, if the particle size of each second phase in the cross-section of the cold storage material particles is less than 100 μm, a 1×10⁻⁶ ppm is applied. 7 The proportion of cold storage material particles that fail after a single vibration is significantly reduced. It has been found that when the particle size of each second phase in the cross-section of the cold storage material particles is less than 100 μm, the mechanical strength of the cold storage material particles is improved. By controlling the particle size of each phase in this way, cold storage material particles with high thermal conductivity and high strength can be provided.

[0301] As shown in Tables 1 to 7, if the proportion of the second phase in the cross-section of the cold storage material particles that is in contact with the third phase exceeds 20%, then after the temperature changes from room temperature to liquid helium temperature, a 1×10⁻⁶ ppm solution is applied. 4The proportion of destructive particles decreases after a single vibration. It is known that if the proportion of particles in contact with the third phase within the second phase exceeds 20%, the mechanical strength of the cold storage material particles increases when a temperature change is applied.

[0302] On the other hand, if the proportion of the second phase in the cross-section of the cold storage material particles that is in contact with the third phase is less than 90%, then after the temperature changes from room temperature to liquid helium temperature, a 1×10⁻⁶ ppm should be applied. 4 The proportion of destructive particles after a single vibration decreases. This indicates that if the proportion of the second phase in contact with the third phase within the cross-section of the cold storage material particles is less than 90%, the mechanical strength of the cold storage material particles when subjected to temperature changes increases. By controlling the contact ratio between the second and third phases in this way, the mechanical strength of the cold storage material particles when subjected to temperature changes is improved.

[0303] As shown in Tables 1 to 7, if the proportion of the second phase in the cross-section of the cold storage material particles that is in contact with the third phase exceeds the proportion of the second phase that is in contact with the fourth phase, then after the temperature changes from room temperature to liquid helium temperature, a 1×10⁻⁶ ppm will be applied. 4 The proportion of destructive particles after a single vibration decreases. If the proportion of the second phase in the cross-section of the cold storage material particles that is in contact with the third phase exceeds the proportion of the second phase that is in contact with the fourth phase, the mechanical strength of the cold storage material particles when subjected to temperature changes increases.

[0304] As shown in Tables 1 to 7, if the particle size of the cold storage material falls within the range of 50 μm or more and 3000 μm or less, the freezing capacity at 4.2 K is significantly improved.

[0305] As shown in Tables 1 to 7, if the aspect ratio of the cold storage material particles is less than 5, the freezing capacity at 4.2K is significantly improved.

[0306] As demonstrated in Examples 60, 66 and 72, the manufacturing speed of cold storage material particles is significantly increased when a dispenser or inkjet printer is used compared to the use of a syringe.

[0307] As shown in Tables 1 to 7, regardless of whether the solution is added by a syringe, dispenser, or inkjet printer, as long as the conditions other than the method of adding the solution are the same, the same particle size, aspect ratio, phase dispersion relationship within the particles, intensity, and specific heat are observed.

[0308] As shown in Tables 1 to 7, even if the methods of adding the solution are different, as long as the particle size, aspect ratio, phase dispersion relationship, strength and specific heat are the same, the performance and reliability of the refrigerator carrying the particle are the same.

[0309] Through the above embodiments, the effects of the cold storage material particles in the first to third embodiments have been confirmed.

[0310] In the first to third embodiments, gadolinium (Gd) was used as an example of the rare earth element that serves as the cold storage element. However, the cold storage element may also be a rare earth element other than gadolinium (Gd).

[0311] Furthermore, in the first to third embodiments, the case of adding calcium (Ca) or aluminum (Al) as the metal element was described as an example, but the metal element added may also be magnesium (Mg), beryllium (Be), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), iron (Fe), copper (Cu), nickel (Ni), or cobalt (Co).

[0312] Furthermore, examples of air pulse distributors or piezoelectric distributors have been given, but plunger distributors can also be used.

[0313] Furthermore, while continuous inkjet printing was used as an example, on-demand inkjet printing can also be used.

[0314] Several embodiments of the present invention have been described, but these embodiments are provided by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, the constituent elements of one embodiment can be substituted or modified with the constituent elements of other embodiments. These embodiments and their variations are included in the scope and spirit of the invention, and are also included in the invention as described in the claims and its equivalents.

[0315] Explanation of symbols 10. Cold storage material particles of the first embodiment 20 Cold storage material particles of the second embodiment 30 Cold storage material particles of the third embodiment 30a Low concentration area 30b High concentration area 100 Cold Storage Type Ultra-Low Temperature Refrigeration Unit 500 Cryogenic Pump 600 superconducting magnet 700 Magnetic Resonance Imaging Device 800 nuclear magnetic resonance device 900° magnetic field applied single crystal pulling device

Claims

1. A cold storage material particle, comprising: Choose at least one first element from the group consisting of rare earth elements, silver (Ag), and copper (Cu), and A second element that differs from the first element and forms polyvalent metal ions in aqueous solution. The atomic concentration of the second element is 0.001 atomic% or more and 60 atomic% or less. The maximum volumetric specific heat at temperatures below 20K is 0.3 J / cm³. 3 K and above, The cold storage material particles comprise a first phase containing the first element and a second phase containing the second element and different from the first phase. The atomic concentration of the second element in the second phase is greater than that in the first phase. The cold storage material particles have a third phase that includes the first element and the second element and is different from the first phase and the second phase. More than 20% and less than 90% of the second phase are in contact with the third phase. The second element is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co).

2. A cold storage material particle, comprising: Choose at least one first element from the group consisting of rare earth elements, silver (Ag), and copper (Cu), and A second element that differs from the first element and forms polyvalent metal ions in aqueous solution. The atomic concentration of the second element is 0.001 atomic% or more and 60 atomic% or less. The maximum volumetric specific heat at temperatures below 20K is 0.3 J / cm³. 3 K and above, The cold storage material particles comprise a first phase containing the first element and a second phase containing the second element and different from the first phase. The atomic concentration of the second element in the second phase is greater than that in the first phase. The second element contains two or more different elements, including element α and element β. The second phase includes element α and element β. The cold storage material particles further possess: A third phase containing element β and different from the first and second phases, and A fourth phase that includes the first element and the element β, and is different from the first phase, the second phase, and the third phase. More than 20% and less than 90% of the second phase are in contact with the third phase. The second element is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), manganese (Mn), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co).

3. The cold storage material particles according to claim 1 or 2, wherein, It further contains oxygen.

4. The cold storage material particles according to claim 1, wherein, The second element contains two or more different elements.

5. The cold storage material particles according to claim 2, wherein, The proportion of the second phase that is in contact with the third phase is higher than the proportion of the second phase that is in contact with the fourth phase.

6. The cold storage material particles according to claim 1 or 2, wherein, In the cross-section of the particle, the area occupied by the second phase is more than 0.001% and less than 75%.

7. The cold storage material particles according to claim 1 or 2, wherein, In the cross-section of the particle, the area of ​​each second phase is 0.001 μm. 2 Above and 6000μm 2 the following.

8. The cold storage material particles according to claim 1 or 2, wherein, In the cross-section of the particles, the particle size of each second phase is greater than 0.1 μm and less than 100 μm.

9. The cold storage material particles according to claim 1 or 2, wherein, The cold storage material particles have a first region and a second region that is closer to the outer edge of the particle than the first region and has a higher atomic concentration of the second element than the first region.

10. The cold storage material particles according to claim 1 or 2, wherein, The first element comprises gadolinium (Gd), and the second element comprises at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra) and aluminum (Al). The cold storage material particles further contain sulfur (S).

11. The cold storage material particles according to claim 1 or 2, wherein, The cold storage material particles contain oxides of the first element or oxysulfides of the first element.

12. The cold storage material particles according to claim 11, wherein, The cold storage material particles contain silver oxide, copper oxide, or gadolinium oxysulfide.

13. The cold storage material particles according to claim 1 or 2, wherein, The particle size of the cold storage material is greater than 50 μm and less than 3 mm.

14. The cold storage material particles according to claim 1 or 2, wherein, The aspect ratio of the cold storage material particles is less than 5.

15. A cold storage device filled with a plurality of cold storage material particles according to any one of claims 1 to 14.

16. A refrigeration unit comprising the cold accumulator as claimed in claim 15.

17. A cryogenic pump comprising the refrigeration unit of claim 16.

18. A superconducting magnet comprising the cryostat of claim 16.

19. A magnetic resonance imaging apparatus comprising the cryostat as described in claim 16.

20. A nuclear magnetic resonance apparatus comprising the cryostat as described in claim 16.

21. A magnetic field-applied single crystal pulling device comprising the cryostat as described in claim 16.

22. A method for manufacturing cold storage material particles according to any one of claims 1 to 14, wherein, A slurry is formed by mixing powder containing at least one first element selected from the group consisting of rare earth elements, silver (Ag), and copper (Cu) with an aqueous solution of alginate. The slurry is sprayed in droplets into a gelled solution containing a second element that forms polyvalent metal ions. The slurry is held in a gelling solution to form gelled particles. The particles are then sintered.

23. The method for manufacturing cold storage material particles according to claim 22, wherein, After the particles are formed, further The particles are washed. The particles are dried. After the particles are dried, they are sintered.

24. The method for manufacturing cold storage material particles according to claim 23, wherein, After the particles are dried and before they are sintered, the particles are further heat-treated in a sulfurizing atmosphere.

25. A method for manufacturing cold storage material particles according to any one of claims 22 to 24, wherein, When the slurry is sprayed into the gelling solution... Use any of the following devices: air pulse dispenser, plunger dispenser, piezoelectric dispenser, inkjet, suction tube, and syringe.

26. The method for manufacturing cold storage material particles according to claim 25, wherein, The nozzle diameter of any of the aforementioned devices is 50 μm or more and 3000 μm or less.

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