Granulated particle for cold storage particles, cold storage particles, cold storage unit, freezer, cryopump, superconducting magnet, nuclear magnetic resonance imaging apparatus, nuclear magnetic resonance apparatus, magnetic field application-type single crystal pulling-out apparatus, and helium recondensing apparatus

Abstract

To provide granulated particles for cold storage particles with high mechanical strength.SOLUTION: A granulated particle for a cold storage particle in an embodiment includes: a first region having a first void fraction; and a second region that is closer to the outer edge of the particle than the first region and has a second void fraction lower than the first void fraction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to granulated particles for regenerator particles, regenerator particles, a regenerator, a refrigerator, a cryopump, a superconducting magnet, a nuclear magnetic resonance imaging apparatus, a nuclear magnetic resonance apparatus, a magnetic field application type single crystal pulling apparatus, and a helium recondensation apparatus. [Background technology]

[0002] In recent years, superconducting technology has made remarkable progress, and as the fields of application of superconducting technology expand, the development of small, high-performance cryogenic refrigerators has become essential. Cryogenic refrigerators are required to be lightweight, small, and highly thermally efficient. Cryogenic refrigerators are being put to practical use in a variety of application fields.

[0003] The cryogenic refrigerator includes a regenerator filled with a plurality of regenerator materials. For example, heat is exchanged between the regenerator materials and helium gas passing through the regenerator to generate cold.

[0004] An example of the cold accumulating material is a ceramic magnetic cold accumulating material particle containing a rare earth element, which is produced, for example, by sintering granulated particles obtained by gelling raw material powder.

[0005] If the strength of the gelled granulated particles is low, there is a problem that the granulated particles may be broken during transportation before sintering. Therefore, it is expected to realize granulated particles for use as cold storage material particles that have high mechanical strength. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2023 / 032867 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide granulated particles for use as cold storage material particles, which have high mechanical strength. [Means for solving the problem]

[0008] The granulated particles for use as cold storage material particles in the embodiment include a first region having a first porosity, and a second region that is closer to the outer edge of the particle than the first region and has a second porosity smaller than the first porosity. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic cross-sectional view of a granulated particle for use as a cold storage material particle according to the first embodiment. [Diagram 2] FIG. 4 is a schematic cross-sectional view of a granulated particle for use as a cold storage material particle according to a modified example of the first embodiment. [Diagram 3] FIG. 5 is a schematic cross-sectional view of a granulated particle for use as a cold storage material particle according to a second embodiment. [Figure 4] FIG. 13 is a schematic cross-sectional view showing a configuration of a main part of a refrigerator according to a fifth embodiment. [Diagram 5] FIG. 13 is a cross-sectional view showing a schematic configuration of a cryopump according to a sixth embodiment. [Figure 6] FIG. 13 is a perspective view showing a schematic configuration of a superconducting magnet according to a seventh embodiment. [Figure 7] FIG. 13 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance imaging apparatus according to an eighth embodiment. [Figure 8] FIG. 13 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance spectrometer according to a ninth embodiment. [Figure 9] FIG. 23 is a perspective view showing a schematic configuration of a magnetic field application type single crystal pulling apparatus according to a tenth embodiment. [Figure 10] FIG. 23 is a schematic diagram showing a schematic configuration of a helium recondensation device according to an eleventh embodiment. [Figure 11] FIG. 4 shows the evaluation results of examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same reference numerals will be used to designate the same or similar components, and the description of components that have already been described may be omitted as appropriate.

[0011] In this specification, the term "extremely low temperature" refers to a temperature range in which the superconducting phenomenon can be utilized industrially in a useful manner, for example, a temperature range of 20K or lower.

[0012] (First embodiment) The granulated particles for use as cold storage material particles of the first embodiment include a first region having a first porosity and a second region that is closer to the outer edge of the particle than the first region and has a second porosity smaller than the first porosity.

[0013] FIG. 1 is a schematic cross-sectional view of a granulated particle for use as a cold storage material particle according to the first embodiment.

[0014] The granulated particles 100 for cold storage material particles of the first embodiment are granulated particles for producing cold storage material particles. The granulated particles 100 for cold storage material particles are, for example, granulated particles for producing ceramic magnetic cold storage material particles.

[0015] For example, the granulated particles 100 for cold storage material particles of the first embodiment are subjected to a heat treatment for sintering to produce cold storage material particles. Prior to the heat treatment for sintering, for example, the granulated particles 100 for cold storage material particles may be subjected to a heat treatment for sulfurization.

[0016] 1, the granulated particle 100 for use as a cold storage material particle includes a first region 10a and a second region 10b. The granulated particle 100 for use as a cold storage material particle also includes a void 11. The void 11 contains, for example, air.

[0017] The granulated particles 100 for use as cold storage material particles contain at least one rare earth element selected from the group consisting of 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), and oxygen (O).

[0018] The granulated particles 100 for cold storage material particles are an aggregate of raw material powder. The granulated particles 100 for cold storage material particles are formed by granulating the raw material powder.

[0019] The granulated particles 100 for cold storage material particles are, for example, gel. The granulated particles 100 for cold storage material particles are formed, for example, by gelling a plurality of raw material powders using a gelling agent (gelling solution). The raw material powders, for example, are in a state where they have lost their independent mobility and are aggregated and solidified.

[0020] When the granulated particle 100 for cold storage material particles is a gel, the granulated particle 100 for cold storage material particles contains, for example, a raw material powder and a dispersion medium. The dispersion medium contains, for example, a gelling agent. When the granulated particle 100 for cold storage material particles is a gel, the granulated particle 100 for cold storage material particles contains, for example, a raw material powder and a gelling agent. Note that the gelling agent after the granulated particle 100 for cold storage material particles is gelled is also referred to as a gelling agent.

[0021] The raw material powder contains, for example, a rare earth oxysulfide or a rare earth oxide. The rare earth oxysulfide contained in the raw material powder contains at least one rare earth element selected from the group consisting of 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). Furthermore, the rare earth oxide contained in the raw material powder contains at least one rare earth element selected from the group consisting of 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).

[0022] The rare earth oxysulfide contained in the raw material powder is, for example, gadolinium oxysulfide, terbium oxysulfide, dysprosium oxysulfide, or holmium oxysulfide. The rare earth oxysulfide contained in the raw material powder is, for example, Gd2O2S, Tb2O2S, Dy2O2S, Ho2O2S, or Er2O2S.

[0023] The rare earth oxide contained in the raw material powder is, for example, gadolinium oxide, terbium oxide, dysprosium oxide, or holmium oxide. The rare earth oxide contained in the raw material powder is, for example, Gd2O3, Tb2O3, Dy2O3, Ho2O3, or Er2O3.

[0024] The composition of the raw material powder can be analyzed by, for example, energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray spectroscopy (WDX), and the substance of the raw material powder can be identified by, for example, powder X-ray diffraction.

[0025] The granulated particles 100 for use as cold storage material particles contain, for example, an additional metal. The additional metal is, for example, one metal element selected from the group consisting of calcium (Ca), magnesium (Mg), beryllium (Be), strontium (Sr), aluminum (Al), iron (Fe), copper (Cu), nickel (Ni), and cobalt (Co). The additional metal is, for example, derived from a gelling solution used in producing the granulated particles 100 for use as cold storage material particles.

[0026] The detection of elements contained in the granulated particles 100 for cold storage material particles and the measurement of the atomic concentration of the elements can be performed, for example, by dissolving the granulated particles in a liquid and using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Also, it can be performed using energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray spectroscopy (WDX).

[0027] The relative density of the granulated particles 100 for cold storage material particles is, for example, 10% or more and 50% or less.

[0028] For example, when the relative density of the granulated particles 100 for cold storage material particles is low, the volume ratio of the raw material powder in the granulated particles 100 for cold storage material particles is relatively small. When the relative density of the granulated particles 100 for cold storage material particles is low, the volume ratio of the dispersion medium or voids 11 in the granulated particles 100 for cold storage material particles is relatively high.

[0029] On the other hand, when the relative density of the granulated particles 100 for cold storage material particles is high, the volume ratio of the raw material powder in the granulated particles 100 for cold storage material particles is relatively high. When the relative density of the granulated particles 100 for cold storage material particles is high, the volume ratio of the dispersion medium or voids 11 in the granulated particles 100 for cold storage material particles is relatively low.

[0030] The granulated particles 100 for cold storage material particles are sintered to form cold storage material particles, and therefore the relative density of the cold storage material particles is higher than that of the granulated particles for cold storage material particles.

[0031] The relative density of the granulated particles 100 for use as cold storage material particles can be calculated, for example, by dividing the average compact density obtained from 50 arbitrarily selected granulated particles for use as cold storage material particles by the true density of the constituent substances. The average compact density of 50 particles is obtained by dividing the weight of 50 granulated particles for use as cold storage material particles by the volume. The volume can be calculated by integrating the volumes of each particle, which are obtained by assuming that the circle-equivalent diameter of each particle is the diameter of the particle.

[0032] In calculating the true density of the granulated particles 100 for use as cold storage material particles, first, the crystal phase of the raw material powder constituting the granulated particles is identified by X-ray diffraction measurement. Then, the composition ratio of the raw material powder constituting the granulated particles is obtained by Rietveld analysis or inductively coupled plasma atomic emission spectrometry of the X-ray diffraction pattern. The true density of the granulated particles 100 for use as cold storage material particles can be calculated from the crystal phase of the raw material powder and the composition ratio of the raw material powder.

[0033] The particle size of the granulated particles 100 for use as cold storage material particles is, for example, 50 μm or more and 7 mm or less. The aspect ratio of the granulated particles 100 for use as cold storage material particles is, for example, 1 or more and 5 or less. The aspect ratio of the granulated particles 100 for use as cold storage material particles is the ratio of the major axis to the minor axis of the granulated particles 100 for use as cold storage material particles.

[0034] The shape of the granulated particles 100 for cold storage material particles is, for example, spherical, spindle-shaped, or irregular.

[0035] In this specification, the particle diameter of the granulated particles 100 for use as cold storage material particles is a circle-equivalent diameter. The circle-equivalent diameter is the diameter of a perfect circle equivalent to the area of ​​a figure observed in an image such as an optical microscope image or a scanning electron microscope (SEM) image. The particle diameter of the granulated particles 100 for use as cold storage material particles can be determined, for example, by image analysis of the optical microscope image or the SEM image.

[0036] The granulated particles 100 for cold storage material particles include a first region 10a and a second region 10b.

[0037] The first region 10a is located inside the granulated particle 100 for cold storage material particles. The first region 10a has a first porosity. The first porosity is, for example, not less than 10% and not more than 50%.

[0038] The second region 10b is closer to the outer edge of the particle than the first region 10a. The second region 10b is located on the outer periphery of the granulated particle 100 for use as a cold storage material particle. The second region 10b surrounds, for example, the first region 10a.

[0039] The second region 10b has a second porosity. The second porosity is smaller than the first porosity. The second porosity is, for example, 0.01% or more and 80% or less of the first porosity. In other words, the ratio of the second porosity to the first porosity is 0.01% or more and 80% or less.

[0040] The second porosity is, for example, not less than 0% and less than 10%.

[0041] The void fraction is the ratio of the area of ​​the voids 11 to the cross section of the granulated particles 100 for use as cold storage material particles.

[0042] The porosity is calculated, for example, from an image obtained by using a scanning electron microscope (SEM) from a cross section of the granulated particle 100 for use as a cold storage material particle solidified with a resin. For example, in an image obtained at a magnification of 5000 times, the area ratio of the voids 11 to a region of 20 μm×20 μm is calculated. For example, image processing software is used to automatically distinguish between the voids 11 and other parts, and the area ratio of the voids 11 is calculated.

[0043] The cross section of the sample was exposed by impregnating the particles in resin and then polishing them with ion milling. If polishing is done with abrasive paper, weak parts of the particles may fall off, making it difficult to accurately evaluate the voids. For this reason, it is preferable to polish the particles with ion milling, which is less likely to cause them to fall off.

[0044] For the granulated particles for the cold storage material particles to be evaluated, particles with a cross-sectional equivalent circle diameter falling within ±10% of the median value of the particle size distribution were selected, and voids were observed. This is because particles with a cross-sectional equivalent circle diameter falling outside the range of ±10% of the median value of the particle size distribution mean that the cross-section is outside the center of the particle, and there is a possibility that the proportion of voids present in the particle cannot be accurately evaluated.

[0045] 1, the cross-sectional shape of the void 11 is shown as a circle, but the cross-sectional shape of the void 11 does not necessarily have to be a circle. The cross-sectional shape of the void 11 is, for example, an ellipse or an irregular shape, and is not limited to this shape.

[0046] The distance from the outer edge of the granulated particle 100 for cold storage material particles in the second region 10b toward the inside is, for example, preferably less than 20% of the particle diameter of the granulated particle 100 for cold storage material particles, more preferably less than 18%, and even more preferably less than 15%. The distance from the outer edge of the granulated particle 100 for cold storage material particles in the first region 10a toward the inside is, for example, 15% or more of the particle diameter of the granulated particle 100 for cold storage material particles. The distance from the outer edge of the granulated particle 100 for cold storage material particles toward the inside is a straight line from a certain point on the outer edge toward another point on the outer edge. This straight line coincides with the straight line that forms the maximum diameter of the granulated particle 100 for cold storage material particles.

[0047] Next, an example of a method for producing the granulated particles for use as cold storage material particles according to the first embodiment will be described.

[0048] First, raw material powder is prepared. For example, oxide or oxysulfide is used as the raw material powder. The type and ratio of the oxide or oxysulfide are adjusted according to the target composition of the regenerator particles.

[0049] The rare earth oxysulfide contained in the raw material powder contains at least one rare earth element selected from the group consisting of 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). Furthermore, the rare earth oxide contained in the raw material powder contains at least one rare earth element selected from the group consisting of 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).

[0050] Next, the raw material powder is added to an aqueous alginic acid solution and mixed to prepare a slurry. For example, a ball mill is used to mix the raw material powder and the aqueous alginic acid solution. The aqueous alginic acid solution is, for example, an aqueous sodium alginate solution, an aqueous ammonium alginate solution, or an aqueous potassium alginate solution.

[0051] Next, the prepared slurry is defoamed by holding the slurry in a vacuum. By defoaming the slurry, the amount of gas in the slurry is reduced.

[0052] The defoamed slurry is dropped into a gelling solution to gel the slurry. The slurry is dropped into the gelling solution using, for example, a dropper, a burette, a pipette, a syringe, a dispenser, or an inkjet. By gelling the slurry, spherical particles containing the raw material powder are formed in the gelling solution.

[0053] Examples of the gelling solution include an aqueous solution of calcium lactate, an aqueous solution of calcium chloride, an aqueous solution of manganese (II) chloride, an aqueous solution of magnesium sulfate, an aqueous solution of beryllium sulfate, an aqueous solution of strontium nitrate, an aqueous solution of aluminum chloride, an aqueous solution of aluminum nitrate, an aqueous solution of aluminum lactate, an aqueous solution of iron (II) chloride, an aqueous solution of iron (III) chloride, an aqueous solution of copper (II) chloride, an aqueous solution of nickel (II) chloride, and an aqueous solution of cobalt (II) chloride.

[0054] After the particles are formed by gelation, the particles are washed with pure water and dried.

[0055] By the above-mentioned manufacturing method, the granulated particles 100 for cold storage material particles of the first embodiment can be manufactured.

[0056] By adjusting the defoaming time of the slurry, the gelling solution concentration, and the gelling time, it is possible to manufacture the granulated particles 100 for use as cold storage material particles having a desired porosity. In particular, it is considered that by defoaming the slurry, it is possible to form the first region 10a and the second region 10b having different porosities in the granulated particles 100 for use as cold storage material particles to be manufactured.

[0057] Ceramic magnetic heat accumulator particles are manufactured, for example, by sintering granulated particles obtained by gelling raw material powder. If the strength of the gelled granulated particles is low, for example, the granulated particles before sintering may be damaged during transportation. Therefore, it is expected to realize granulated particles for heat accumulator particles having high mechanical strength.

[0058] 1, the granulated particle 100 for cold storage material particles of the first embodiment includes a second region 10b that is closer to the outer edge of the particle than the first region 10a and has a second porosity smaller than the first porosity. Since the second region 10b has a smaller porosity than the first region 10a, the second region 10b has a higher mechanical strength than the first region 10a.

[0059] This increases the mechanical strength of the granulated particles 100 for use as cold storage material particles, thereby preventing damage to the granulated particles 100 for use as cold storage material particles before sintering.

[0060] For example, when producing cold storage material particles containing rare earth oxysulfide, granulated particles for cold storage material particles containing rare earth oxide as raw material powder are subjected to heat treatment for sulfurizing the raw material powder. The rare earth oxide is sulfurized by the heat treatment to become rare earth oxysulfide. After the heat treatment for sulfurizing the raw material powder, the granulated particles for cold storage material particles are sintered to produce cold storage material particles containing rare earth oxysulfide.

[0061] In the granulated particles 100 for cold storage material particles of the first embodiment, the first porosity of the first region 10a is larger than the second porosity of the second region 10b. Therefore, during the heat treatment for sulfurizing the raw material powder, the sulfurizing gas easily penetrates the first region 10a. Therefore, the sulfurization of the raw material powder is promoted. Therefore, the raw material powder in the granulated particles 100 for cold storage material particles can be sufficiently sulfurized. Since sufficient sulfurization can be realized, the ratio of oxysulfides that contribute to the specific heat increases, and the specific heat of the sintered particles increases.

[0062] According to the granulated particles 100 for cold storage material particles of the first embodiment, it is possible to achieve both high mechanical strength and sufficient sulfurization of the raw material powder.

[0063] From the viewpoint of increasing the mechanical strength of the granulated particles 100 for use as cold storage material particles, the second porosity is preferably 80% or less of the first porosity, more preferably 20% or less, and even more preferably 10% or less.

[0064] In addition, from the viewpoint of improving the degree of sulfurization of the granulated particles 100 for use as cold storage material particles, the second porosity is preferably 0.01% or more of the first porosity, more preferably 0.1% or more, and even more preferably 1% or more.

[0065] Therefore, the second porosity of the granulated particles 100 for use as cold storage material particles is preferably 0.01% to 80% of the first porosity, more preferably 0.1% to 20%, and even more preferably 1% to 10%. By setting the second porosity within such a range, it is possible to improve both the mechanical strength of the granulated particles 100 for use as cold storage material particles and the degree of sulfurization.

[0066] From the viewpoint of increasing the mechanical strength of the granulated particles 100 for use as cold storage material particles, the second porosity is preferably less than 10%, and more preferably 5% or less. From the viewpoint of increasing the mechanical strength of the granulated particles 100 for use as cold storage material particles, the first porosity is preferably 50% or less.

[0067] From the viewpoint of improving the degree of sulfurization of the granulated particles 100 for cold storage material particles, the first porosity is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more. From the viewpoint of improving the degree of sulfurization of the granulated particles 100 for cold storage material particles, the second porosity is preferably 0.1% or more, and more preferably 1% or more.

[0068] From the viewpoint of reducing the temperature of the heat treatment for sulfurization or sintering, or from the viewpoint of reducing the time of the heat treatment for sulfurization or sintering, the relative density of the granulated particles 100 for heat storage material particles is preferably 50% or less, and more preferably 40% or less.

[0069] If the relative density of the granulated particles 100 for cold storage material particles is less than 10%, for example, the proportion of voids in the granulated particles 100 for cold storage material particles increases, and the mechanical strength of the granulated particles 100 for cold storage material particles decreases.

[0070] In addition, when the relative density of the granulated particles for cold storage material particles is less than 10%, for example, the relative density of the manufactured cold storage material particles decreases, and the specific heat of the cold storage material particles decreases. This is thought to be because the number of contact points between the raw material powders decreases, and the sinterability of the cold storage material particles decreases.

[0071] Therefore, it is preferable that the granulated particles 100 for cold storage material particles have a relative density of 10% or more.

[0072] (Modification) The granulated particles for use as cold storage material particles according to the modified example of the first embodiment differ from the granulated particles for use as cold storage material particles according to the first embodiment in that the second region is present only in a portion of the outer periphery of the particle.

[0073] FIG. 2 is a schematic cross-sectional view of a granulated particle for use as a cold storage material particle according to a modified example of the first embodiment.

[0074] In the modified example of the first embodiment, the second region 10b is present only on a part of the outer periphery of the cold storage material particle 101. The second region 10b does not surround the first region 10a.

[0075] The granulated particles 101 for cold storage material particles according to the modified example of the first embodiment can achieve both high mechanical strength and sufficient sulfurization of the raw material powder, similar to the granulated particles 100 for cold storage material particles according to the first embodiment.

[0076] As described above, according to the first embodiment and the modified example, it is possible to provide granulated particles for cold storage material particles having high mechanical strength. Also, according to the first embodiment and the modified example, it is possible to provide granulated particles for cold storage material particles that can realize sufficient sulfurization of the raw material powder.

[0077] Second Embodiment The granulated particles for cold storage material particles of the second embodiment are different from the granulated particles for cold storage material particles of the first embodiment in that the granulated particles for cold storage material particles of the second embodiment further include a third region that is farther from the outer edge of the particle than the first region and has a third porosity smaller than the first porosity. Hereinafter, some of the descriptions that overlap with the first embodiment may be omitted.

[0078] FIG. 3 is a schematic cross-sectional view of a granulated particle for use as a cold storage material particle according to the second embodiment.

[0079] 3, the granulated particle 200 for use as a cold storage material particle according to the second embodiment includes a first region 10a, a second region 10b, and a third region 10c. The granulated particle 200 for use as a cold storage material particle further includes voids 11.

[0080] The first region 10a has a first porosity, which is, for example, not less than 10% and not more than 50%.

[0081] The second region 10b is closer to the outer edge of the particle than the first region 10a. The second region 10b is located on the outer periphery of the granulated particle 101 for use as a cold storage material particle. The second region 10b surrounds, for example, the first region 10a.

[0082] The second region 10b has a second porosity. The second porosity is smaller than the first porosity. The second porosity is, for example, 0.01% or more and 80% or less of the first porosity. In other words, the ratio of the second porosity to the first porosity is 0.01% or more and 80% or less.

[0083] The second porosity is, for example, not less than 0% and less than 10%.

[0084] The third region 10c is farther from the outer edge of the particle than the first region 10a. The third region 10c is located in the center of the granulated particle 100 for use as a cold storage material particle. The first region 10a surrounds the third region 10c, for example.

[0085] The third region 10c has a third porosity. The third porosity is smaller than the first porosity. The third porosity is, for example, 0.01% or more and 80% or less of the first porosity. In other words, the ratio of the third porosity to the first porosity is 0.01% or more and 80% or less.

[0086] The third porosity is, for example, not less than 0% and less than 10%.

[0087] The distance from the outer edge of the granulated particle 200 for cold storage material particles to the inside of the second region 10b is, for example, preferably less than 20%, more preferably less than 18%, and even more preferably less than 15% of the particle diameter of the granulated particle 200 for cold storage material particles. The distance from the outer edge of the granulated particle 200 for cold storage material particles to the inside of the first region 10a is, for example, 15% or more and less than 40% of the particle diameter of the granulated particle 200 for cold storage material particles. The distance from the outer edge of the granulated particle 200 for cold storage material particles to the inside of the third region 10c is, for example, 40% or more and 50% or less of the particle diameter of the granulated particle 200 for cold storage material particles.

[0088] The granulated particles 200 for use as cold storage material particles of the second embodiment can be produced, for example, by adjusting the conditions for degassing the slurry in the method for producing the granulated particles 200 for use as cold storage material particles of the first embodiment.

[0089] The granulated particle 200 for cold storage material particles of the second embodiment can achieve both high mechanical strength and sufficient sulfurization of the raw material powder, similar to the granulated particle 100 for cold storage material particles of the first embodiment. In addition, the granulated particle 200 for cold storage material particles of the second embodiment can achieve even higher mechanical strength by providing the third region 10c, which has a smaller porosity than the first region 10a, in the central portion.

[0090] As described above, according to the second embodiment, it is possible to provide granulated particles for use as cold storage material particles, which have high mechanical strength. Also, according to the second embodiment, it is possible to provide granulated particles for use as cold storage material particles, which can realize sufficient sulfurization of the raw material powder.

[0091] (Third embodiment) The cold storage material particles of the third embodiment are obtained by sintering the granulated particles 100 for cold storage material particles of the first embodiment.

[0092] The cold storage material particles of the third embodiment have a particle size of, for example, 50 μm or more and 5 mm or less. The aspect ratio of the cold storage material particles is, for example, 1 or more and 5 or less. The aspect ratio of the cold storage material particles is the ratio of the major axis to the minor axis of the cold storage material particles. The shape of the cold storage material particles is, for example, spherical.

[0093] The cold storage material particles of the third embodiment have a relative density of, for example, 90% or more.

[0094] The cold accumulator particles of the third embodiment are cold accumulator particles manufactured from the granulated particles 100 for cold accumulator particles of the first embodiment. The cold accumulator particles of the third embodiment contain a rare earth oxysulfide or a rare earth oxide.

[0095] The rare earth oxysulfide contained in the regenerator particles contains at least one rare earth element selected from the group consisting of 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). The rare earth oxide contained in the regenerator particles contains at least one rare earth element selected from the group consisting of 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).

[0096] The maximum value of the volumetric specific heat of the cold storage material particles in the third embodiment in the temperature range of 2 K to 10 K is, for example, 0.5 J / (cm 3 ·K) or higher.

[0097] The cold storage material particles of the third embodiment may be, for example, a compound represented by the general formula R 2±0.1 O2S 1±0.1 (wherein R represents at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu).

[0098] In the rare earth oxysulfide represented by the above general formula, the maximum volumetric specific heat and the temperature at which the maximum volumetric specific heat is shown vary depending on the selected rare earth element. Therefore, the specific heat characteristics of the rare earth oxysulfide can be adjusted by appropriately adjusting the ratio of the rare earth element. The rare earth element is, for example, at least one element selected from the group consisting of Gd, Tb, Dy, Ho, and Er. The rare earth element may include, for example, two or more kinds of rare earth elements.

[0099] The cold storage material particles of the third embodiment may be, for example, a compound represented by the general formula R 1±0.1 M 1±0.1 O 3±0.1 (wherein R represents at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and M represents at least one element selected from the group consisting of Al, Cr, Mn, and Fe).

[0100] In the rare earth oxide represented by the above general formula, the maximum volumetric specific heat and the temperature at which the maximum volumetric specific heat is shown vary depending on the rare earth element selected. Therefore, the specific heat characteristics of the rare earth oxide can be adjusted by appropriately adjusting the ratio of the rare earth element. The rare earth element is, for example, at least one element selected from the group consisting of Gd, Tb, Dy, Ho, and Er. The rare earth element may include, for example, two or more kinds of rare earth elements.

[0101] The cold storage material particles of the third embodiment have a maximum volumetric specific heat of 0.5 J / (cm 3 ·K) or more. Therefore, the cold storage material particles of the third embodiment have a high volumetric specific heat. Since the cold storage material particles of the third embodiment have a high volumetric specific heat, a cold storage device equipped with the cold storage material particles of the third embodiment has high cold storage performance, and the refrigerator exhibits high refrigeration capacity.

[0102] The cold storage material particles of the third embodiment are produced by carrying out a heat treatment for sintering on the granulated particles 100 for cold storage material particles of the first embodiment.

[0103] For example, when an oxide is used as the raw material powder of the granulated particles 100 for cold storage material particles to manufacture cold storage material particles containing oxysulfides, the granulated particles 100 for cold storage material particles are sulfurized. In this case, heat treatment is performed in a sulfurization atmosphere. The sulfurization atmosphere contains a gas containing a sulfur atom with a negative oxidation number, such as hydrogen sulfide (H2S), carbon sulfide (CS2), or methanethiol (CH3SH). The temperature of the sulfurization heat treatment is, for example, 400°C or higher and 600°C or lower. The time of the sulfurization heat treatment is, for example, 1 hour or higher and 5 hours or lower.

[0104] The heat treatment for sintering the obtained oxysulfide is carried out, for example, in an inert gas atmosphere at a heat treatment temperature of, for example, 1100° C. to 2000° C. for a heat treatment time of, for example, 1 hour to 48 hours.

[0105] The cold storage material particles of the third embodiment are manufactured by sintering the granulated particles 100 for cold storage material particles of the first embodiment. Therefore, for example, damage to the granulated particles 100 for cold storage material particles is suppressed, and a high manufacturing yield of the cold storage material particles can be realized. In addition, for example, sufficient sulfurization of the raw material powder can be realized, and a high manufacturing yield of the cold storage material particles can be realized. Therefore, for example, the manufacturing cost of the cold storage material particles can be reduced.

[0106] As described above, according to the third embodiment, it is possible to provide cold storage material particles that can achieve a high production yield and reduce the production cost.

[0107] (Fourth embodiment) The cold storage device of the fourth embodiment is a cold storage device filled with a plurality of cold storage particles of the third embodiment. For example, when the peripheral length of the projected image of the plurality of cold storage particles of the third embodiment is L and the actual area of ​​the projected image is A, the cold storage device of the fourth embodiment has a surface area of ​​4πA / L. 2 The ratio of the cold storage material particles having a circularity R of 0.5 or less is 5% or less.

[0108] The circularity R can be obtained by image processing of the shapes of multiple cold storage material particles using an optical microscope. Cold storage material particles with a circularity R of 0.5 or less have a shape with unevenness on the surface. When multiple cold storage material particles containing more than 5% of such cold storage material particles are filled into a cold storage device, the void ratio in the cold storage device becomes non-uniform and the filling property becomes unstable. For this reason, when the working medium flows in, the cold storage performance decreases, and the cold storage material particles move or break due to the stress applied to the cold storage material particles when the cold storage material particles are filled or when the refrigerator is operating, generating fine particles that cause clogging of the voids, thereby decreasing the refrigeration performance and long-term reliability of the refrigerator. The cold storage material particles with a circularity R of 0.5 or less are preferably 2% or less, more preferably 0%.

[0109] Fifth embodiment The refrigerator of the fifth embodiment is a refrigerator including the cold storage unit of the fourth embodiment filled with a plurality of cold storage material particles of the third embodiment. Hereinafter, some of the contents overlapping with the third and fourth embodiments will be omitted.

[0110] Fig. 4 is a schematic cross-sectional view showing the configuration of the main parts of a refrigerator according to a fifth embodiment. Fig. 4 is a schematic cross-sectional view showing the configuration of the main parts of a GM refrigerator, which is an example of the refrigerator according to the fifth embodiment. The GM refrigerator, which is an example of the refrigerator according to the fifth embodiment, includes the cold storage unit according to the fourth embodiment filled with a plurality of cold storage material particles according to the third embodiment.

[0111] The refrigerator of the fifth embodiment is a two-stage regenerative cryogenic refrigerator 300 used for cooling superconducting equipment, etc. The refrigerator may be, for example, a Stirling type refrigerator or a pulse tube type refrigerator.

[0112] The cold storage type cryogenic refrigerator 300 (refrigerator) includes a first cylinder 111, a second cylinder 112, a vacuum container 113, a first cold storage unit 114, a second cold storage unit 115 (cold storage units), a first seal ring 116, a second seal ring 117, a first cold storage material 118, a second cold storage material 119 (cold storage material particles), a first expansion chamber 120, a second expansion chamber 121, a first cooling stage 122, a second cooling stage 123, and a compressor 124.

[0113] The cold storage type cryogenic refrigerator 300 includes a vacuum container 113 in which a large-diameter first cylinder 111 and a small-diameter second cylinder 112 coaxially connected to the first cylinder 111 are installed. A first cold storage unit 114 is arranged in the first cylinder 111 so as to be capable of reciprocating. A second cold storage unit 115, which is an example of the cold storage unit of the fourth embodiment, is arranged in the second cylinder 112 so as to be capable of reciprocating.

[0114] A first seal ring 116 is disposed between the first cylinder 111 and the first regenerator 114. A second seal ring 117 is disposed between the second cylinder 112 and the second regenerator 115.

[0115] The first regenerator 114 is filled with a first regenerator material 118 such as a Cu mesh. The second regenerator 115 is filled with a second regenerator material 119, which is a plurality of regenerator particles of the third embodiment.

[0116] The second regenerator 115 may be divided by a metal mesh material and may have a plurality of regenerator packed layers. When the second regenerator 115 is divided into a plurality of packed layers, at least one packed layer is filled with a regenerator particle group consisting of a plurality of the regenerator particles of the third embodiment. Then, for example, the regenerator particle group is combined with at least one type of regenerator particle group selected from a lead regenerator particle group, a bismuth regenerator particle group, a tin regenerator particle group, a holmium copper regenerator particle group, an erbium nickel regenerator particle group, an erbium cobalt regenerator particle group, and a gadolinium aluminum oxide regenerator particle group.

[0117] The combination of the heat storage materials is such that the first heat storage material particle group has a higher peak specific heat temperature, and the second heat storage material particle group has a lower peak specific heat temperature, and the combinations are made so that the peak specific heat temperatures decrease sequentially.

[0118] In the case of the two-layer type, a combination of using holmium copper cold storage material particles as the first cold storage material particle group and the cold storage material particle group of the third embodiment as the second cold storage material particle group can be mentioned. Also, in the case of the three-layer type, a combination of using at least one cold storage material particle group selected from lead cold storage material particle group, bismuth cold storage material particle group, and tin cold storage material particle group as the first cold storage material particle group, using holmium copper cold storage material particle group as the second cold storage material particle group, and using the cold storage material particle group of the third embodiment as the third cold storage material particle group can be mentioned.

[0119] The holmium copper regenerator particles are preferably, for example, HoCu2 or HoCu.The erbium nickel regenerator particles are preferably, for example, ErNi or Er3Ni.

[0120] The first regenerator 114 and the second regenerator 115 each have a passage for the working medium provided in the gap of the first regenerator material 118 and the second regenerator material 119. The working medium is helium gas.

[0121] A first expansion chamber 120 is provided between the first cold storage unit 114 and the second cold storage unit 115. A second expansion chamber 121 is provided between the second cold storage unit 115 and the end wall of the second cylinder 112. A first cooling stage 122 is provided at the bottom of the first expansion chamber 120. A second cooling stage 123, which has a lower temperature than the first cooling stage 122, is formed at the bottom of the second expansion chamber 121.

[0122] The two-stage regenerative cryogenic refrigerator 300 described above is supplied with a high-pressure working medium from the compressor 124. The supplied working medium passes between the first regenerator material 118 packed in the first regenerator 114 and reaches the first expansion chamber 120. Then, the working medium passes between the second regenerator material 119 packed in the second regenerator 115 and reaches the second expansion chamber 121.

[0123] At this time, the working medium is cooled by supplying thermal energy to the first cold storage material 118 and the second cold storage material 119. The working medium passing between the first cold storage material 118 and the second cold storage material 119 expands in the first expansion chamber 120 and the second expansion chamber 121 to generate cold. Then, the first cooling stage 122 and the second cooling stage 123 are cooled.

[0124] The expanded working medium flows in the opposite direction between the first cold storage material 118 and the second cold storage material 119. The working medium is discharged after receiving thermal energy from the first cold storage material 118 and the second cold storage material 119. In this process, the heat recovery effect is improved, and the thermal efficiency of the working medium cycle is improved, so that the cold storage type cryogenic refrigerator 300 is configured to realize a lower temperature.

[0125] The cold storage unit included in the cold storage type cryogenic refrigerator 300 of the fifth embodiment is filled with a plurality of cold storage particles of the third embodiment as the second cold storage material 119 in the second cold storage unit 115. At least a part of the second cold storage material 119 is the cold storage particle of the third embodiment.

[0126] In the third embodiment, when the peripheral length of each projected image of the plurality of cold storage particles is L and the actual area of ​​the projected image is A, the ratio of the peripheral length of each projected image to the actual area of ​​the plurality of cold storage particles is 4πA / L 2 It is preferable that the circularity R of 0.5 or less is 5% or less.

[0127] In order to improve the refrigeration capacity of a refrigerator, it is desirable to improve the specific heat per unit volume of the regenerator material and to improve the thermal conductivity and heat transfer coefficient. The regenerator type cryogenic refrigerator 300 of the fifth embodiment is equipped with a regenerator material or regenerator material particles that maintain the volumetric specific heat and improve the thermal conductivity and heat transfer coefficient. The regenerator type cryogenic refrigerator 300 of the fifth embodiment is equipped with a regenerator material or regenerator material particles that can reduce manufacturing costs.

[0128] For example, by using the regenerative cryogenic refrigerator 300 of the fifth embodiment in a magnetic levitation train, the long-term reliability of the magnetic levitation train can be improved.

[0129] As described above, according to the fifth embodiment, a refrigerator with excellent characteristics can be realized by using the cold storage material particles with excellent characteristics.

[0130] Sixth embodiment The cryopump of the sixth embodiment includes the refrigerator of the fifth embodiment. Hereinafter, some of the contents that overlap with the fifth embodiment will be omitted.

[0131] 5 is a cross-sectional view showing a schematic configuration of a cryopump according to a sixth embodiment. The cryopump according to the sixth embodiment is a cryopump 500 including the regenerative cryogenic refrigerator 300 according to the fifth embodiment.

[0132] The cryopump 500 includes a cryopanel 501 that condenses or adsorbs gas molecules, a regenerative cryogenic refrigerator 300 that cools the cryopanel 501 to a predetermined cryogenic temperature, a shield 503 provided between the cryopanel 501 and the regenerative cryogenic refrigerator 300, a baffle 504 provided at the intake port, and a ring 505 that changes the pumping speed of argon, nitrogen, hydrogen, etc.

[0133] According to the sixth embodiment, a cryopump with excellent characteristics can be realized by using a refrigerator with excellent characteristics. In addition, by using the cryopump of the sixth embodiment in semiconductor manufacturing equipment, the long-term reliability of the semiconductor manufacturing equipment can be improved and the number of maintenance operations for the semiconductor manufacturing equipment can be reduced. As a result, this contributes to improving the quality of the manufactured semiconductors and reducing the manufacturing costs.

[0134] Seventh embodiment The superconducting magnet of the seventh embodiment includes the refrigerator of the fifth embodiment. Hereinafter, some of the contents that overlap with the fifth embodiment will be omitted.

[0135] 6 is a perspective view showing a schematic configuration of a superconducting magnet according to a seventh embodiment. The superconducting magnet according to the seventh embodiment is a superconducting magnet 600 for a magnetic levitation train equipped with the regenerative cryogenic refrigerator 300 according to the fifth embodiment.

[0136] The superconducting magnet 600 for a magnetic levitation train includes a superconducting coil 601, a liquid helium tank 602 for cooling the superconducting coil 601, a liquid nitrogen tank 603 for preventing the evaporation of the liquid helium, a laminated insulation material 605, a power lead 606, a persistent current switch 607, and a regenerative type cryogenic refrigerator 300.

[0137] According to the seventh embodiment, a superconducting magnet with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0138] Eighth embodiment The nuclear magnetic resonance imaging apparatus of the eighth embodiment includes the refrigerator of the fifth embodiment. Hereinafter, some of the contents that overlap with the fifth embodiment will be omitted.

[0139] 7 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance imaging apparatus according to an eighth embodiment. The nuclear magnetic resonance imaging (MRI) apparatus according to the eighth embodiment is a nuclear magnetic resonance imaging apparatus 700 including the regenerative cryogenic refrigerator 300 according to the fifth embodiment.

[0140] The nuclear magnetic resonance imaging apparatus 700 includes a superconducting static magnetic field coil 701 that applies a spatially uniform and temporally stable static magnetic field to the human body, a correction coil (not shown) that corrects non-uniformity of the generated magnetic field, a gradient magnetic field coil 702 that applies a magnetic field gradient to a measurement region, a radio frequency wave transmitting / receiving probe 703, a cryostat 705, and a radiation heat insulating shield 706. A regenerative type cryogenic refrigerator 300 is used to cool the superconducting static magnetic field coil 701.

[0141] According to the eighth embodiment, a nuclear magnetic resonance imaging apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0142] Ninth embodiment The nuclear magnetic resonance apparatus of the ninth embodiment includes the refrigerator of the fifth embodiment. Hereinafter, some of the contents that overlap with the fifth embodiment will be omitted.

[0143] 8 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance apparatus according to a ninth embodiment. The nuclear magnetic resonance (NMR) apparatus according to the ninth embodiment is a nuclear magnetic resonance apparatus 800 including the regenerative cryogenic refrigerator 300 according to the fifth embodiment.

[0144] 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 an induced current generated in a coil (not shown) around the sample tube 801. The apparatus also includes a regenerative type cryogenic refrigerator 300 that cools the superconducting static magnetic field coil 802.

[0145] According to the ninth embodiment, a nuclear magnetic resonance apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0146] (Tenth embodiment) The magnetic field application type single crystal pulling apparatus of the tenth embodiment includes the refrigerator of the fifth embodiment. Hereinafter, some of the contents that overlap with the fifth embodiment will be omitted.

[0147] 9 is a perspective view showing a schematic configuration of a magnetic field application type single crystal pulling apparatus according to the tenth embodiment. The magnetic field application type single crystal pulling apparatus according to the tenth embodiment is a magnetic field application type single crystal pulling apparatus 900 including the regenerative cryogenic refrigerator 300 according to the fifth embodiment.

[0148] The magnetic field application type single crystal pulling apparatus 900 includes a single crystal pulling section 901 having a crucible for melting raw material, a heater, a single crystal pulling mechanism, etc., a superconducting coil 902 for applying a static magnetic field to the raw material melt, a lifting mechanism 903 for the single crystal pulling section 901, a current lead 905, a heat shield plate 906, and a helium container 907. A regenerative type cryogenic refrigerator 300 is used to cool the superconducting coil 902.

[0149] According to the tenth embodiment, a magnetic field application type single crystal pulling apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0150] (Eleventh embodiment) The helium recondensing apparatus of the eleventh embodiment includes the refrigerator of the fifth embodiment. Hereinafter, some of the contents overlapping with the fifth embodiment will be omitted.

[0151] 10 is a schematic diagram showing a schematic configuration of a helium recondensation apparatus according to an eleventh embodiment. The helium recondensation apparatus according to the eleventh embodiment is a helium recondensation apparatus 1000 including the regenerative cryogenic refrigerator 300 according to the fifth embodiment.

[0152] The helium recondensation device 1000 includes a regenerative cryogenic refrigerator 300 , an evaporation pipe 1001 , and a liquefaction pipe 1002 .

[0153] The helium recondensing device 1000 can recondense helium gas evaporated from a liquid helium device to form liquid helium. The liquid helium device can be, for example, a superconducting magnet, a nuclear magnetic resonance (NMR) device, a nuclear magnetic resonance imaging (MRI) device, a physical property measurement system (PPMS), or a magnetic property measurement system.

[0154] Helium gas is introduced into the helium recondenser 1000 from a liquid helium device (not shown) through evaporation piping 1001. The helium gas is cooled to 4K, which is below the liquefaction temperature of helium, by the regenerative cryogenic refrigerator 300. The condensed and liquefied liquid helium passes through liquefaction piping 1002 and returns to the liquid helium device.

[0155] According to the eleventh embodiment, a refrigerator with excellent characteristics is used, thereby making it possible to realize a helium recondensing device with excellent characteristics. EXAMPLES

[0156] Hereinafter, examples and comparative examples relating to the granulated particles for cold storage material particles of the first embodiment and the cold storage material particles of the third embodiment, and their evaluation results will be described.

[0157] Example 1 Gd2O3 powder and Al2O3 powder were added to the sodium alginate aqueous solution and mixed for 12 hours to prepare a slurry. The slurry was then kept in a vacuum and degassed for 1 hour.

[0158] The defoamed slurry was dropped into the calcium lactate aqueous solution, which was the gelling solution. A syringe was used to drop the slurry. The diameter of the syringe was 510 μm, and the distance from the tip of the syringe to the liquid surface of the calcium lactate aqueous solution was 100 mm. The calcium concentration of the gelling solution was 0.1 mol%.

[0159] The slurry dropped by the syringe was kept in the gelling solution for 5 minutes. After that, the gelled particles were washed with pure water and dried. By drying the particles, the granulated particles for the cold storage material particles of Example 1 were produced.

[0160] The porosity of the produced granulated particles for use as cold storage material particles was measured. The first porosity in the interior of the granulated particles for use as cold storage material particles and the second porosity in the outer periphery were measured. Furthermore, the ratio of the second porosity to the first porosity (second porosity / first porosity) was calculated.

[0161] The porosity of the granulated particles for use as cold storage material particles was determined by observing the cross section of the particles. When observing the cross section of the granulated particles for use as cold storage material particles, a sample was used in which the particles were impregnated with resin and then polished by ion milling to expose the cross section.

[0162] The exposed cross-section of the sample was observed using a scanning electron microscope (SEM). At this time, the secondary electron image and backscattered electron image of the SEM were compared to exclude any dust adhering to the measurement surface and identify the voids.

[0163] In addition, as the granulated particles for the cold storage material particles to be evaluated, particles having a cross-sectional equivalent circle diameter within ±10% of the median value of the particle size distribution were selected, and voids were observed.

[0164] The inside and the outer periphery of the particle were observed by the above-mentioned method, and the ratio of the voids was quantified by the image processing software Image J. The area ratio of the voids obtained by dividing the second void ratio in the outer periphery of the granulated particle for heat storage material of Example 1 by the first void ratio in the inside was 0.25%.

[0165] In order to evaluate the rate at which the granulated particles for the cold storage material of Example 1 break during transportation, the granulated particles for the cold storage material were filled in a cylindrical container with a diameter of 15 mm and a height of 5 mm at room temperature and subjected to an amplitude of 2 mm and a maximum acceleration of 100 m / s 2 The simple harmonic motion of 4 The weight percentage of particles broken by the vibration was taken as the breakage rate.

[0166] After evaluating the breakage rate, the manufactured granulated particles for use as cold storage material particles were subjected to sulfurization. The particles were sulfurized by heat treatment at 500°C for 4 hours in an atmosphere containing hydrogen sulfide (H2S).

[0167] The main component of the granulated particles for use as cold storage material particles that were subjected to the sulfurization treatment in Example 1 was gadolinium oxysulfide, and the subphases included perovskite-type oxide, garnet-type oxide, and alumina.

[0168] The degree of sulfurization in the conventional technology is determined by dividing the maximum intensity attributable to gadolinium oxysulfide observed in the XRD pattern in the comparative example described later by the maximum intensity attributable to the phase with the largest abundance ratio among the group consisting of perovskite-type oxide, garnet-type oxide, and alumina. The degree of sulfurization in Example 1 was calculated, and when this value was divided by the degree of sulfurization in the conventional technology, the value was 100%.

[0169] After the particles were sulfurized, they were sintered by heat treatment at 1300° C. for 12 hours in a pressurized inert gas atmosphere. By sintering the particles, cold storage material particles corresponding to the third embodiment were obtained.

[0170] The relative density of the granulated particles for use as cold storage material particles in Example 1 was 30%.

[0171] The relative density of the cold storage material particles obtained by sintering the granulated particles for cold storage material particles of Example 1 was 90% or more. In addition, the cold storage material particles obtained from the granulated particles for cold storage material particles of Example 1 had a maximum volumetric specific heat of 0.5 J / (cm 3 ·K) or higher.

[0172] (Examples 2 to 7) The cold storage material particles of Examples 2 to 7 are different from the cold storage material particles of Example 1 in the ratio of the second porosity of the outer periphery of the cold storage material granulated particle and the first porosity of the inside. When producing the cold storage material granulated particles of Examples 2 to 7, the degassing time, the gelling solution concentration, and the gelling time were changed compared to the case of producing the cold storage material granulated particles of Example 1. The produced cold storage material granulated particles were evaluated in the same manner as in Example 1.

[0173] Example 8 Granulated particles for use as a cold storage material were produced in the same manner as in Example 1, except that Tb2O3 powder was used instead of Gd2O3 powder. The produced granulated particles for use as a cold storage material were evaluated in the same manner as in Example 1.

[0174] Example 9 Granulated particles for use as a cold storage material were produced in the same manner as in Example 1, except that Dy2O3 powder was used instead of Gd2O3 powder. The produced granulated particles for use as a cold storage material were evaluated in the same manner as in Example 1.

[0175] Example 10 The granulated particles for use as a cold storage material were produced in the same manner as in Example 1, except that Ho2O3 powder was used instead of Gd2O3 powder. The granulated particles for use as a cold storage material were evaluated in the same manner as in Example 1.

[0176] (Comparative Example) When producing the cold storage material particles of Comparative Example 1, degassing was not performed, the calcium concentration of the gelling liquid was set to 0.5 mol%, and the gelling time was set to 5 hours, in contrast to the production of the cold storage material particles of Example 1. The produced cold storage material granulated particles were evaluated in the same manner as in Example 1.

[0177] The granulated particles for cold storage material of the comparative example differ from the granulated particles for cold storage material of Example 1 in that the ratio of the second porosity of the outer periphery to the first porosity of the interior is as large as 101%. In other words, the granulated particles for cold storage material of the comparative example differ from the granulated particles for cold storage material of Example 1 in that the second porosity is larger than the first porosity.

[0178] For the granulated particles for heat storage material of each of the Examples and Comparative Examples, the first porosity inside the particle, the second porosity in the outer periphery of the particle, the ratio of the second porosity to the first porosity, and the degree of sulfurization are shown in Table 1.

[0179] [Table 1]

[0180] Fig. 11 is a diagram showing the evaluation results of Examples and Comparative Examples. Fig. 11 is a diagram showing the breakage rate and the degree of sulfurization of granulated particles for use as cold storage material particles in Examples 1 to 7 and Comparative Examples. The breakage rate and the degree of sulfurization of granulated particles for use as cold storage material particles are shown using the ratio of the second porosity to the first porosity as a parameter.

[0181] The breakage rate of the granulated particles for the cold storage material particles is shown by white circles in Fig. 11. The progress of sulfurization is shown by black circles in Fig. 11.

[0182] As is clear from Table 1 and FIG. 1, by making the second porosity of the outer periphery of the granulated particles for use as cold storage material particles smaller than the first porosity of the interior, the breakage rate of the granulated particles for use as cold storage material particles is reduced.

[0183] From the viewpoint of reducing the breakage rate of the granulated particles for use as cold storage material particles, the second porosity is preferably 80% or less of the first porosity, more preferably 20% or less, and even more preferably 10% or less.

[0184] On the other hand, as is clear from Table 1 and Fig. 11, when the second porosity of the outer periphery of the granulated particle for cold storage material particles is made smaller than the first porosity of the inside, the degree of sulfurization of the granulated particle for cold storage material particles decreases. The reason why the degree of sulfurization decreases when the ratio of the second porosity to the first porosity becomes excessively small is considered to be that the outer periphery of the particle becomes dense, making it impossible for the sulfurization gas to advance to the inside of the particle.

[0185] From the viewpoint of improving the degree of sulfurization of the granulated particles for use as cold storage material particles, the second porosity is preferably 0.01% or more of the first porosity, more preferably 0.1% or more, and even more preferably 1% or more.

[0186] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, components of one embodiment may be replaced or changed with components of another embodiment. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0187] The technical solutions of the present invention are described below, and are included in the scope of the present invention.

[0188] (Technical proposal 1) a first region having a first porosity; a second region that is closer to the outer edge of the particle than the first region and has a second porosity that is smaller than the first porosity.

[0189] (Technical proposal 2) The granulated particles for use as cold storage material particles according to Technical Scheme 1, wherein the second region surrounds the first region.

[0190] (Technical proposal 3) The granulated particles for use as cold storage material particles according to Technical Scheme 1 or 2, wherein the second porosity is 0.01% or more and 80% or less of the first porosity.

[0191] (Technical proposal 4) The granulated particles for use as cold storage material particles according to any one of Technical Schemes 1 to 3, wherein the first porosity is 10% or more and 50% or less, and the second porosity is 0% or more and less than 10%.

[0192] (Technical proposal 5) Granulated particles for use in cooling accumulator particles according to any one of Technical Schemes 1 to 4, comprising at least one rare earth element selected from the group consisting of 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), and oxygen (O).

[0193] (Technical proposal 6) A granulated particle for use as a heat storage material particle, as described in any one of Technical Proposals 1 to 5, wherein the distance from the outer edge of the particle in the second region to the inside is less than 20% of the particle's particle diameter, and the distance from the outer edge of the particle in the first region to the inside is 15% or more of the particle's particle diameter.

[0194] (Technical proposal 7) The granulated particles for use as cold storage material particles according to any one of Technical Schemes 1 to 6, having a relative density of 10% or more and 50% or less.

[0195] (Technical proposal 8) The granulated particles for use as cold storage material particles according to any one of Technical Schemes 1 to 7, which are a gel.

[0196] (Technical proposal 9) The granulated particles for use as a heat storage material particle according to any one of Technical Schemes 1 to 8 further include a third region that is farther from the outer edge of the particle than the first region and has a third porosity smaller than the first porosity.

[0197] (Technical proposal 10) The granulated particles for use as cold storage material particles according to Technical Proposal 9, wherein the second region surrounds the first region, and the first region surrounds the third region.

[0198] (Technical proposal 11) A cold storage material particle obtained by sintering a granulated particle for cold storage material particles according to any one of Technical Schemes 1 to 10.

[0199] (Technical proposal 12) The maximum volumetric specific heat in the temperature range from 2K to 10K is 0.5J / (cm 3 The cold storage material particles according to Technical Proposal 11, which are equal to or greater than K.

[0200] (Technical proposal 13) A cold storage device filled with multiple cold storage material particles described in Technical Proposal 11 or Technical Proposal 12.

[0201] (Technical proposal 14) A refrigerator equipped with a regenerator as described in Technical Proposal 13.

[0202] (Technical proposal 15) A cryopump equipped with a refrigerator described in Technical Proposal 14.

[0203] (Technical proposal 16) A superconducting magnet equipped with a refrigerator described in Technical Proposal 14.

[0204] (Technical proposal 17) A nuclear magnetic resonance imaging device equipped with a refrigerator described in Technical Proposal 14.

[0205] (Technical proposal 18) A nuclear magnetic resonance apparatus equipped with a refrigerator described in Technical Proposal 14.

[0206] (Technical proposal 19) A magnetic field application type single crystal pulling device equipped with a refrigerator described in Technical Proposal 14.

[0207] (Technical proposal 20) A helium recondensing device equipped with a refrigerator described in Technical Proposal 14. [Explanation of symbols]

[0208] 10a First Area 10b The second area 10c The third area 11 void 100 Granulated particles for cold storage material particles 101 Granulated particles for cold storage material particles 115 Second regenerator (regenerator) 119 Second cold storage material (cold storage material particles) 200 Granulated particles for cold storage material particles 300 Regenerative cryogenic refrigerator (refrigerator) 500 Cryopump 600 Superconducting Magnet 700 Nuclear Magnetic Resonance Imaging Device 800 Nuclear Magnetic Resonance Spectrometer 900 Magnetic Field Application Type Single Crystal Pulling Apparatus 1000 Helium Recondenser

Claims

1. a first region having a first porosity; a second region located closer to an outer edge of the particle than the first region and having a second porosity smaller than the first porosity.

2. The granulated particles for use as regenerator particles according to claim 1 , wherein the second region surrounds the first region.

3. 2. The granulated particles for use as regenerator particles according to claim 1, wherein the second porosity is 0.01% or more and 80% or less of the first porosity.

4. 2. The granulated particles for use as regenerator particles according to claim 1, wherein the first porosity is 10% or more and 50% or less, and the second porosity is 0% or more and less than 10%.

5. The granulated particles for use as regenerator particles according to claim 1, comprising at least one rare earth element selected from the group consisting of 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), and oxygen (O).

6. 2. The granulated particle for heat storage material particles according to claim 1, wherein the distance from the outer edge of the particle to the inside of the particle in the second region is less than 20% of the particle diameter, and the distance from the outer edge of the particle to the inside of the particle in the first region is 15% or more of the particle diameter.

7. 2. The granulated particles for use as cold storage material particles according to claim 1, having a relative density of 10% or more and 50% or less.

8. The granulated particles for use as cold storage material particles according to claim 1, which is a gel.

9. 2. The granulated particle for use as a cold storage material particle according to claim 1, further comprising a third region that is farther from an outer edge of the particle than the first region and has a third porosity smaller than the first porosity.

10. The granulated particles for use as cold storage material particles according to claim 9 , wherein the second region surrounds the first region, and the first region surrounds the third region.

11. 2. A heat accumulating material particle obtained by sintering the granulated particles for heat accumulating material particles according to claim 1.

12. The maximum volumetric specific heat in the temperature range from 2K to 10K is 0.5 J / (cm ３ The heat accumulator particles according to claim 11, wherein the heat accumulator particles have a molecular weight of 1.0 or more.

13. A regenerator filled with a plurality of the regenerator particles according to claim 11.

14. A refrigerator comprising the regenerator according to claim 13.

15. A cryopump comprising the refrigerator according to claim 14.

16. A superconducting magnet comprising the refrigerator according to claim 14.

17. A nuclear magnetic resonance imaging apparatus comprising the refrigerator according to claim 14.

18. A nuclear magnetic resonance apparatus comprising the refrigerator according to claim 14.

19. A magnetic field application type single crystal pulling apparatus comprising the refrigerator according to claim 14.

20. A helium recondensing device comprising the refrigerator according to claim 14.

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