Cold storage particle, cold storage particle group, 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 a cold storage particle having excellent specific heat characteristics.SOLUTION: A cold storage particle of an embodiment includes: at least one first element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); nickel (Ni); at least one second element selected from the group consisting of silicon (Si) and germanium (Ge); a SmNiGe3-type crystal phase; and at least one of a CeNiSi2-type crystal phase and a CaF2-type crystal phase.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a cold storage material particle, a cold storage material particle group, a cold storage unit, 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 particles, and generates cold by, for example, exchanging heat between the regenerator particles and helium gas passing through the regenerator.

[0004] An example of the cold storage material particles is a magnetic cold storage material particle containing a rare earth element and a metal. An example of the magnetic cold storage material particles containing a rare earth element and a metal is HoCu2. In order to improve the performance of a cryogenic refrigerator, it is expected to realize a cold storage material particle with excellent specific heat characteristics. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2022 / 224783 [Non-patent literature]

[0006] [Non-Patent Document 1] Fabiana R. Arantes et al., “Structure, magnetism, and transport of single-crystalline RNiSi3(R=Y,Gd-Tm,Lu)”, Physical Review Materials 2,044402(2018) Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a cold storage material particle having excellent specific heat characteristics. [Means for solving the problem]

[0008] The regenerator particles of the embodiment include at least one first 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), at least one second element selected from the group consisting of nickel (Ni), silicon (Si), and germanium (Ge), and at least one of an SmNiGe3 type crystal phase, a CeNiSi2 type crystal phase, and a CaF2 type crystal phase. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic cross-sectional view of a cold storage material particle according to the first embodiment. [Diagram 2] FIG. 6 is a schematic cross-sectional view of a cold storage material particle according to a second embodiment. [Diagram 3] Schematic cross-sectional view of a heat storage material particle according to a modified example of the second embodiment. [Figure 4] FIG. 11 is a schematic cross-sectional view showing a configuration of a main part of a refrigerator according to a fourth embodiment. [Diagram 5] FIG. 11 is a cross-sectional view showing a schematic configuration of a cryopump according to a fifth embodiment. [Figure 6] FIG. 13 is a perspective view showing a schematic configuration of a superconducting magnet according to a sixth embodiment. [Figure 7] FIG. 13 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance imaging apparatus according to a seventh embodiment. [Figure 8] FIG. 13 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance spectrometer according to an eighth embodiment. [Figure 9] FIG. 13 is a perspective view showing a schematic configuration of a magnetic field application type single crystal pulling apparatus according to a ninth embodiment. [Figure 10] FIG. 23 is a schematic diagram showing a schematic configuration of a helium recondensation device according to a tenth embodiment. 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 25K or lower.

[0012] (First embodiment) The cold storage material particles of the first embodiment include at least one first 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), at least one second element selected from the group consisting of nickel (Ni), silicon (Si), and germanium (Ge), and at least one of an SmNiGe3 type crystal phase, a CeNiSi2 type crystal phase, and a CaF2 type crystal phase.

[0013] 1 is a schematic cross-sectional view of a heat regenerator particle according to the first embodiment. The heat regenerator particle 100 according to the first embodiment is a magnetic heat regenerator particle containing a rare earth element and a metal.

[0014] As shown in Fig. 1, the heat accumulating material particle 100 is polycrystalline. The heat accumulating material particle 100 includes a plurality of crystal grains. The plurality of crystal grains includes a first crystal grain 10a, a second crystal grain 10b, and a third crystal grain 10c. A grain boundary phase may exist between the plurality of crystal grains.

[0015] The cold storage material particle 100 includes a SmNiGe3 type crystal phase. The cold storage material particle 100 includes at least one of a CeNiSi2 type crystal phase and a CaF2 type crystal phase. The cold storage material particle 100 may include only one of a CeNiSi2 type crystal phase and a CaF2 type crystal phase. The cold storage material particle 100 may include both a CeNiSi2 type crystal phase and a CaF2 type crystal phase.

[0016] For example, the first crystal grains 10a are of the SmNiGe3 type crystal phase, the second crystal grains 10b are of the CeNiSi2 type crystal phase, and the third crystal grains 10c are of the CaF2 type crystal phase.

[0017] For example, the SmNiGe3 type crystal phase is the main crystal phase among the crystal phases contained in the cold storage material particle 100. The SmNiGe3 type crystal phase being the main crystal phase means that the ratio of the SmNiGe3 type crystal phase in the cold storage material particle 100 is greater than the ratio of other crystal phases. The ratio of the SmNiGe3 type crystal phase in the cold storage material particle 100 is preferably 30% or more, more preferably 50% or more.

[0018] Whether the cold storage material particle 100 contains the SmNiGe3 type crystal phase, the CeNiSi2 type crystal phase, or the CaF2 type crystal phase can be determined by powder X-ray diffraction (PXRD). In addition, whether the SmNiGe3 type crystal phase is the main crystal phase among the crystal phases contained in the cold storage material particle 100 can be determined, for example, by comparing the peak intensity of the crystal phase obtained by powder X-ray diffraction. In addition, the weight ratio of the crystal phase present in the sample is analyzed by Rietveld analysis of the diffraction pattern obtained by the XRD method, and the obtained values ​​are compared to determine whether the SmNiGe3 type crystal phase is the main crystal phase.

[0019] In addition, whether the SmNiGe3 type crystal phase is the main crystal phase among the crystal phases contained in the cold storage material particle 100 can be determined by, for example, observing a reflected electron image of the cross section of the cold storage material particle 100 with a scanning electron microscope (SEM). For example, it can be determined by comparing the occupied area of ​​the crystal grains identified as the SmNiGe3 type crystal phase in the reflected electron image with the occupied area of ​​the other crystal grains using image processing software. Whether the crystal grains are the SmNiGe3 type crystal phase can be determined by, for example, energy dispersive X-ray spectroscopy (EDX).

[0020] The regenerator particles 100 contain at least one first 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 first element is a rare earth element.

[0021] The regenerator particle 100 contains at least one second element selected from the group consisting of silicon (Si) and germanium (Ge).

[0022] The chemical composition of the SmNiGe3 type crystal phase contained in the heat accumulating material particle 100 is, for example, R 1±x Ni 1±x (Si y Ge 1-y ) 3±x (R is 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), 0≦x≦0.5, 0≦y≦1). The chemical composition of the SmNiGe3 type crystal phase contained in the heat accumulating material particle 100 is, for example, HoNiSi3 or HoNiGe3.

[0023] The chemical composition of the CeNiSi2 type crystal phase contained in the heat accumulating material particle 100 is, for example, R 1±x Ni 1±x (Si y Ge 1-y ) 2±x (R is 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), 0≦x≦0.5, 0≦y≦1). The chemical composition of the CeNiSi2 type crystal phase contained in the heat accumulating material particle 100 is, for example, HoNiSi2 or HoNiGe2.

[0024] The chemical composition of the CaF2 type crystal phase contained in the cold storage material particle 100 is, for example, Ni 1±x S 2±x (0≦x≦0.5).

[0025] The elements contained in the cold storage material particles 100 can be detected and the atomic concentration of the elements can be measured, for example, by using inductively coupled plasma atomic emission spectroscopy (ICP-AES). For example, the cold storage material particles 100 are dissolved in a liquid, and the dissolved cold storage material particles 100 are measured by inductively coupled plasma atomic emission spectroscopy.

[0026] The elements contained in the heat storage material particles 100, the first crystal grains 10a, the second crystal grains 10b, or the third crystal grains 10c can be detected and the atomic concentrations of the elements can be measured, for example, by using energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray spectroscopy (WDX).

[0027] The peak intensity of the peak corresponding to the (131) plane of the SmNiGe3 type crystal phase obtained from the heat storage material particle 100 by the powder X-ray diffraction method is defined as the first peak intensity (Ia), the peak intensity of the peak corresponding to the (131) plane of the CeNiSi2 type crystal phase is defined as the second peak intensity (Ib), and the peak intensity of the peak corresponding to the (111) plane of the CaF2 type crystal phase obtained by the powder X-ray diffraction method is defined as the third peak intensity (Ic). The ratio ((Ib+Ic) / Ia) of the sum of the second peak intensity (Ib) and the third peak intensity (Ic) to the first peak intensity (Ia) is, for example, 0.01 or more and 0.3 or less.

[0028] When the cold accumulator particles 100 are measured by powder X-ray diffraction, for example, the cold accumulator particles 100 are pulverized in an agate mortar, and the powder passed through a 500 mesh sieve is used as a measurement sample.

[0029] The cold storage material particles 100 have a particle size of, for example, 50 μm or more and 3 mm or less. The cold storage material particles 100 have a shape of, for example, a spherical shape.

[0030] In this specification, the particle diameter of the 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 image. The particle diameter of the cold storage material particles can be determined, for example, by image analysis of the optical microscope image or the scanning electron microscope image.

[0031] When the perimeter of the projected image of the cold storage material particle 100 is L and the actual area of ​​the projected image is A, 4πA / L 2 The circularity R expressed by the following formula is, for example, greater than 0.5. The circularity R of the cold storage material particle 100 can be determined, for example, by image analysis of an optical microscope image or a scanning electron microscope image.

[0032] The aspect ratio of the cold storage material particle 100 is, for example, from 1 to 5. The aspect ratio of the cold storage material particle 100 is the ratio of the major axis to the minor axis of the cold storage material particle 100. The aspect ratio of the cold storage material particle 100 can be determined, for example, by image analysis of an optical microscope image or a scanning electron microscope image.

[0033] The maximum value of the volumetric specific heat of the cold storage material particles 100 in the temperature range of 25 K or less is, for example, 0.38 J / (cm 3 ·K) or higher.

[0034] Next, an example of a method for producing the heat regenerator particles according to the first embodiment will be described below, taking as an example a case where the first element is holmium (Ho) and the second element is silicon (Si).

[0035] First, the HoNiSi3 mother alloy is prepared by high-frequency induction melting. Next, the HoNiSi3 mother alloy is melted and the molten metal is dropped onto a rotating disk in an argon atmosphere and rapidly solidified. The molten metal is rapidly solidified to produce the cold storage material particles.

[0036] The cooling rate of the molten metal can be controlled by controlling the rotation speed of the rotating disk. For example, the cooling rate of the molten metal can be increased by increasing the rotation speed of the rotating disk. Also, for example, the cooling rate of the molten metal can be decreased by decreasing the rotation speed of the rotating disk.

[0037] By controlling the cooling rate of the molten metal, the ratio ((Ib+Ic) / Ia) of the sum of the second peak intensity and the third peak intensity to the first peak intensity of the produced cold storage material particles can be controlled to a desired value. For example, by increasing the cooling rate of the molten metal, the ratio ((Ib+Ic) / Ia) can be reduced. Also, by decreasing the cooling rate of the molten metal, the ratio ((Ib+Ic) / Ia) can be increased.

[0038] By the above-mentioned manufacturing method, the cold storage material particles 100 of the first embodiment can be manufactured.

[0039] The heat regenerator particle 100 of the first embodiment includes a SmNiGe3 type crystal phase and includes a first element, nickel (Ni), and a second element. The chemical composition of the SmNiGe3 type crystal phase included in the heat regenerator particle 100 is, for example, RNi (Si x Ge 1-x )3 (R is 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), 0≦x≦1).

[0040] The cold storage material particle 100 of the first embodiment can achieve a high volumetric specific heat compared to, for example, HoCu2.

[0041] Furthermore, the cold storage material particle 100 of the first embodiment has a smaller atomic ratio of rare earth elements than, for example, HoCu2. The smaller atomic ratio of expensive rare earth elements allows the production cost of the cold storage material particle 100 to be reduced.

[0042] The cold storage material particles having a circularity R of 0.5 or less have, for example, unevenness on the surface. For example, when the cold storage material particles having unevenness on the surface are filled into the cold storage unit of a refrigerator, the void ratio in the cold storage unit becomes non-uniform, and the filling property becomes unstable. Therefore, for example, when the working medium flows into the cold storage unit, the cold storage performance of the cold storage unit decreases.

[0043] In addition, for example, stress applied to the cold storage material particles when the cold storage material particles are filled or when the refrigerator is in operation may cause the cold storage material particles to move or break down, generating fine particles, which may cause the gaps in the cold storage unit to become clogged. The clogging of the gaps reduces the refrigeration performance and long-term reliability of the refrigerator.

[0044] Therefore, the cold storage material particles filled in the cold storage unit are preferably spherical. In other words, the circularity R of the cold storage material particles 100 is preferably large, and the circularity R is preferably close to 1. The circularity R of the cold storage material particles 100 is preferably larger than 0.5, more preferably 0.7 or more, and even more preferably 0.9 or more.

[0045] In the cold storage material particle 100 of the first embodiment, the peak intensity of the peak corresponding to the (131) plane of the SmNiGe3 type crystal phase obtained by powder X-ray diffraction is defined as the first peak intensity (Ia), the peak intensity of the peak corresponding to the (131) plane of the CeNiSi2 type crystal phase is defined as the second peak intensity (Ib), and the peak intensity of the peak corresponding to the (111) plane of the CaF2 type crystal phase obtained by powder X-ray diffraction is defined as the third peak intensity (Ic). The ratio ((Ib+Ic) / Ia) of the sum of the second peak intensity and the third peak intensity to the first peak intensity is preferably 0.01 or more and 0.3 or less.

[0046] When the ratio ((Ib+Ic) / Ia) is 0.01 or more and 0.3 or less, it becomes easy to make the cold storage material particles 100 spherical particles. When the ratio ((Ib+Ic) / Ia) is 0.01 or more and 0.3 or less, it becomes easy to increase the circularity R of the cold storage material particles 100. When the ratio ((Ib+Ic) / Ia) is 0.01 or more and 0.3 or less, it becomes easy to make the circularity R of the cold storage material particles 100 closer to 1.

[0047] The maximum volumetric heat capacity of the heat storage material particle 100 in the temperature range below 25K is 0.38 J / (cm 3 ·K) or more, and 0.4 J / (cm 3 ·K) or more, and 0.45 J / (cm 3 ·K) or more is more preferable.

[0048] The cold storage material particle group may contain 90% or more of the cold storage material particles 100 of the first embodiment in terms of number ratio.

[0049] As described above, according to the first embodiment, it is possible to provide cold storage material particles having excellent specific heat characteristics, and it is also possible to provide cold storage material particles that can be easily formed into spherical particles.

[0050] Second Embodiment The regenerator particles of the second embodiment include at least one first 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), at least one second element selected from the group consisting of nickel (Ni), silicon (Si), and germanium (Ge), an SmNiGe3 type crystal phase, and a first phase in which the atomic concentration of the second element is greater than 70 atomic %. The cold storage material particles of the second embodiment are different from the cold storage material particles of the first embodiment in that they contain at least one phase in which the atomic concentration of the second element is greater than 70 atomic %. Hereinafter, some of the contents that overlap with the first embodiment may be omitted.

[0051] 2 is a schematic cross-sectional view of a heat regenerator particle according to the second embodiment. The heat regenerator particle 200 according to the second embodiment is a magnetic heat regenerator material containing a rare earth element and a metal.

[0052] 2, the heat accumulator particle 200 may be polycrystalline. The heat accumulator particle 200 includes a plurality of crystal grains. The plurality of crystal grains includes a first crystal grain 10a. The heat accumulator particle 200 also includes grains 10x.

[0053] The regenerator particle 200 includes a SmNiGe3 type crystal phase. For example, the first crystal grains 10a are of the SmNiGe3 type crystal phase.

[0054] For example, the SmNiGe3 type crystal phase is the main crystal phase among the crystal phases contained in the cold storage material particle 200. The SmNiGe3 type crystal phase being the main crystal phase means that the ratio of the SmNiGe3 type crystal phase in the cold storage material particle 200 is greater than the ratios of other crystal phases. The ratio of the SmNiGe3 type crystal phase in the cold storage material particle 100 is preferably 30% or more, more preferably 50% or more.

[0055] Whether the cold storage material particle 200 contains the SmNiGe3 type crystal phase can be determined by powder X-ray diffraction. In addition, whether the SmNiGe3 type crystal phase is the main crystal phase among the crystal phases contained in the cold storage material particle 200 can be determined by, for example, comparing the peak intensities of the crystal phases obtained by powder X-ray diffraction.

[0056] In addition, whether the SmNiGe3 type crystal phase is the main crystal phase among the crystal phases contained in the cold storage material particle 200 can be determined by, for example, observing the reflected electron image of the cross section of the cold storage material particle 200 with a scanning electron microscope. For example, it can be determined by comparing the occupied area of ​​the crystal grains specified as the SmNiGe3 type crystal phase in the reflected electron image with the occupied area of ​​the other crystal grains using image processing software. Whether the crystal grains are the SmNiGe3 type crystal phase can be determined by, for example, energy dispersive X-ray spectroscopy.

[0057] The heat storage material particle 200 includes a first phase in which the atomic concentration of the second element is greater than 70 atomic %. The second element is at least one element selected from the group consisting of silicon (Si) and germanium (Ge). The second element may be only either silicon (Si) or germanium (Ge). The second element may be both silicon (Si) and germanium (Ge). For example, the grain 10x is the first phase.

[0058] The first phase is, for example, crystalline or amorphous. The grain 10x is, for example, crystalline or amorphous. The atomic concentration of the second element contained in the first phase is, for example, 100 atomic % or less. In addition, the second phase and the third phase are, for example, crystalline or amorphous.

[0059] The area ratio of the first phase in the cross section of the cold storage material particle 200 is, for example, 0.01% or more and 45% or less.

[0060] Whether or not the regenerator particle 200 contains the first phase can be determined by using, for example, energy dispersive X-ray spectroscopy or wavelength dispersive X-ray analysis.

[0061] The area ratio of the first phase contained in the cold storage material particle 200 can be determined, for example, by observing a backscattered electron image of the cross section of the cold storage material particle 200 with a scanning electron microscope. For example, the area occupied by particles identified as the first phase in the backscattered electron image is measured using image processing software. Whether or not a particle is the first phase can be determined, for example, by energy dispersive X-ray spectroscopy.

[0062] The regenerator particles 200 contain at least one first 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 first element is a rare earth element.

[0063] The regenerator particles 200 contain at least one second element selected from the group consisting of silicon (Si) and germanium (Ge).

[0064] The chemical composition of the SmNiGe3 type crystal phase contained in the regenerator particle 200 is, for example, RNi(Si x Ge 1-x )3 (R is 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), 0≦x≦1). The chemical composition of the SmNiGe3 type crystal phase contained in the heat storage material particle 200 is, for example, HoNiSi3 or HoNiGe3.

[0065] The elements contained in the cold storage material particles 200 can be detected and the atomic concentration of the elements can be measured by, for example, inductively coupled plasma optical emission spectroscopy. For example, the cold storage material particles 200 are dissolved in a liquid, and the dissolved cold storage material particles 200 are measured by inductively coupled plasma optical emission spectroscopy.

[0066] The elements contained in the heat storage material particle 200, the first crystal grain 10a, or the grain 10x can be detected and the atomic concentration of the elements can be measured, for example, by using energy dispersive X-ray spectroscopy or wavelength dispersive X-ray analysis.

[0067] The cold storage material particles 200 have a particle size of, for example, 50 μm or more and 3 mm or less. The cold storage material particles 200 have a shape of, for example, a spherical shape.

[0068] When the peripheral length of the projected image of the cold storage material particle 200 is L and the actual area of ​​the projected image is A, 4πA / L 2 The circularity R expressed as: is, for example, greater than 0.5.

[0069] The aspect ratio of the cold storage material particle 200 is, for example, 1 or more and 5 or less.

[0070] The maximum value of the volumetric specific heat of the cold storage material particles 200 in the temperature range of 25 K or less is, for example, 0.38 J / (cm 3 ·K) or higher.

[0071] Next, an example of a method for producing the heat regenerator particles according to the second embodiment will be described below, taking as an example a case where the first element is holmium (Ho) and the second element is silicon (Si).

[0072] First, the HoNiSi3 mother alloy is prepared by high-frequency induction melting. Next, the HoNiSi3 mother alloy is melted and the molten metal is dropped onto a rotating disk in an argon atmosphere and rapidly solidified. The molten metal is rapidly solidified to produce the cold storage material particles.

[0073] The cooling rate of the molten metal can be controlled by controlling the rotation speed of the rotating disk. For example, the cooling rate of the molten metal can be increased by increasing the rotation speed of the rotating disk. Also, for example, the cooling rate of the molten metal can be decreased by decreasing the rotation speed of the rotating disk.

[0074] By controlling the cooling rate of the molten metal, the area ratio of the first phase of the produced cold storage material particles can be controlled to a desired value. For example, by increasing the cooling rate of the molten metal, the area ratio of the first phase can be reduced. Also, by decreasing the cooling rate of the molten metal, the area ratio of the first phase can be increased.

[0075] By the above-mentioned manufacturing method, the cold storage material particles 200 of the second embodiment can be manufactured.

[0076] The heat regenerator particle 200 of the second embodiment includes a SmNiGe3 type crystal phase and includes a first element, nickel (Ni), and a second element. The chemical composition of the SmNiGe3 type crystal phase included in the heat regenerator particle 200 is, for example, RNi (Si x Ge 1-x )3 (R is 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), 0≦x≦1).

[0077] The cold storage material particle 200 of the second embodiment can achieve a high volumetric specific heat compared to, for example, HoCu2.

[0078] Moreover, the cold storage material particle 200 of the second embodiment has a smaller atomic ratio of rare earth elements than, for example, HoCu2. The smaller atomic ratio of expensive rare earth elements allows the manufacturing cost of the cold storage material particle 200 to be reduced.

[0079] The cold storage material particles having a circularity R of 0.5 or less have, for example, unevenness on the surface. For example, when a plurality of cold storage material particles containing more than 5% of cold storage material particles having unevenness on the surface are filled into a cold storage device of a refrigerator, the void ratio in the cold storage device becomes non-uniform, or the filling property becomes unstable. For this reason, for example, when the working medium flows into the cold storage device, the cold storage performance of the cold storage device decreases.

[0080] In addition, for example, stress applied to the cold storage material particles when the cold storage material particles are filled or when the refrigerator is in operation may cause the cold storage material particles to move or break down, generating fine particles, which may cause the gaps in the cold storage unit to become clogged. The clogging of the gaps reduces the refrigeration performance and long-term reliability of the refrigerator.

[0081] Therefore, the cold storage material particles filled in the cold storage unit are preferably spherical. In other words, the circularity R of the cold storage material particles 200 is preferably large, and the circularity R is preferably close to 1. The circularity R of the cold storage material particles 200 is preferably larger than 0.5, more preferably 0.7 or more, and even more preferably 0.9 or more.

[0082] In the cold storage material particle 200 of the second embodiment, the area ratio of the first phase in which the atomic concentration of the second element is greater than 70 atomic % is preferably 0.01% or more and 45% or less.

[0083] When the area ratio of the first phase is 0.01% or more and 45% or less, it becomes easy to make the cold storage material particle 200 a spherical particle. When the area ratio of the first phase is 0.01% or more and 45% or less, it becomes easy to increase the circularity R of the cold storage material particle 200. When the area ratio of the first phase is 0.01% or more and 45% or less, it becomes easy to make the circularity R of the cold storage material particle 200 close to 1.

[0084] From the viewpoint of making the heat storage material particles 200 spherical particles, the area ratio of the first phase is more preferably 0.1% or more and 30% or less, and further preferably 1% or more and 20% or less.

[0085] From the viewpoint of making the regenerator particles 200 spherical particles, the atomic concentration of the second element contained in the first phase is more preferably 75% or more.

[0086] The maximum volumetric heat capacity of the cold storage material particles 200 in the temperature range below 25K is 0.4 J / (cm 3 ·K) or more, and 0.5 J / (cm 3 ·K) or more is more preferable.

[0087] (Modification) The cold storage material particles of the modified example of the second embodiment differ from the cold storage material particles of the second embodiment in that the cold storage material particles of the modified example of the second embodiment contain at least one of a CeNiSi2 type crystal phase and a CaF2 type crystal phase.

[0088] 3 is a schematic cross-sectional view of a heat regenerator particle according to a modification of the second embodiment. The heat regenerator particle 210 according to the modification of the second embodiment is a magnetic heat regenerator material containing a rare earth element and a metal.

[0089] As shown in Fig. 3, the cold storage material particle 210 may be polycrystalline. When the cold storage material particle 210 is polycrystalline, the cold storage material particle 210 includes a plurality of crystal grains. The plurality of crystal grains includes a first crystal grain 10a, a second crystal grain 10b, and a third crystal grain 10c. The cold storage material particle 210 also includes a grain 10x.

[0090] The cold storage material particle 210 includes a SmNiGe3 type crystal phase. The cold storage material particle 210 includes at least one of a CeNiSi2 type crystal phase and a CaF2 type crystal phase. The cold storage material particle 210 may include only one of a CeNiSi2 type crystal phase and a CaF2 type crystal phase. The cold storage material particle 210 may include both a CeNiSi2 type crystal phase and a CaF2 type crystal phase.

[0091] For example, the first crystal grains 10a are of the SmNiGe3 type crystal phase, the second crystal grains 10b are of the CeNiSi2 type crystal phase, and the third crystal grains 10c are of the CaF2 type crystal phase.

[0092] The heat regenerator particle 210 includes a first phase having an atomic concentration of a second element greater than 70 atomic %. The second element is at least one element selected from the group consisting of silicon (Si) and germanium (Ge). For example, the grain 10x is of the first phase.

[0093] The cold storage material particle 210 of the modified example of the second embodiment has the same effects as the cold storage material particle 200 of the second embodiment.

[0094] The cold storage material particle group may contain 90% or more of the cold storage material particles 200 of the second embodiment in terms of number ratio.

[0095] As described above, according to the second embodiment and the modified example, it is possible to provide cold storage material particles having excellent specific heat characteristics. Also, according to the second embodiment and the modified example, it is possible to provide cold storage material particles that can be easily formed into spherical particles.

[0096] (Third embodiment) The cold storage device of the third embodiment is a cold storage device filled with a plurality of cold storage material particles of the first or second embodiment. For example, when the peripheral length of the projected image of the plurality of cold storage material particles of the first or second embodiment is L and the actual area of ​​the projected image is A, the cold storage device of the third embodiment has a ratio 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.

[0097] The circularity R can be obtained by image processing of the shapes of a plurality of cold storage material particles in an image obtained using an optical microscope. Cold storage material particles having a circularity R of 0.5 or less have, for example, unevenness on the surface.

[0098] For example, if the cold storage unit is filled with more than 5% of cold storage particles having uneven surfaces, the porosity in the cold storage unit becomes uneven and the filling property becomes unstable. Therefore, for example, when the working medium flows in, the cold storage performance of the cold storage unit decreases.

[0099] In addition, for example, stress applied to the cold storage material particles when the cold storage material particles are filled or when the refrigerator is in operation may cause the cold storage material particles to move or break down, generating fine particles, which may cause the gaps in the cold storage unit to become clogged. The clogging of the gaps reduces the refrigeration performance and long-term reliability of the refrigerator.

[0100] Therefore, the amount of cold accumulator particles with a circularity R of 0.5 or less packed in the cold accumulator is preferably 2% or less, and more preferably 0%.

[0101] As described above, according to the third embodiment, a regenerator with excellent characteristics can be realized by using regenerator material particles with excellent characteristics.

[0102] (Fourth embodiment) The refrigerator of the fourth embodiment is a refrigerator equipped with the cold storage device of the third embodiment filled with a plurality of cold storage material particles of the first or second embodiment. In the following, some of the contents overlapping with the first, second and third embodiments will be omitted.

[0103] Fig. 4 is a schematic cross-sectional view showing the configuration of the main parts of a refrigerator according to a fourth 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 fourth embodiment. The GM refrigerator, which is an example of the refrigerator according to the fourth embodiment, includes the cold storage unit according to the third embodiment filled with a plurality of cold storage material particles according to the first or second embodiment.

[0104] The refrigerator of the fourth 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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 first or second embodiment.

[0109] The second regenerator 115 may be divided by a metal mesh material and 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 first or second embodiment. Then, for example, the regenerator particle group is combined with at least one type of regenerator particle group selected from rare earth oxide regenerator particle group, rare earth oxysulfide regenerator particle group, lead regenerator particle group, bismuth regenerator particle group, tin regenerator particle group, holmium copper regenerator particle group, erbium nickel regenerator particle group, erbium cobalt regenerator particle group, and gadolinium aluminum oxide regenerator particle group.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] The cold storage unit included in the cold storage type cryogenic refrigerator 300 of the fourth embodiment is filled with a plurality of cold storage particles of the first or second embodiment as a 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 first or second embodiment.

[0117] In the first or second embodiment, 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, and the peripheral length of each projected image of the plurality of cold storage particles is 4πA / L 2 It is preferable that the amount of the cold storage material particles having a circularity R of 0.5 or less is 5% or less.

[0118] 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 fourth 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 fourth embodiment is equipped with a regenerator material or regenerator material particles that can reduce manufacturing costs.

[0119] For example, by using the regenerative cryogenic refrigerator 300 of the fourth embodiment in a magnetic levitation train, the long-term reliability of the magnetic levitation train can be improved.

[0120] As described above, according to the fourth embodiment, a refrigerator with excellent characteristics can be realized by using the cold storage material particles with excellent characteristics.

[0121] Fifth embodiment The cryopump of the fifth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the contents that overlap with the fourth embodiment will be omitted.

[0122] 5 is a cross-sectional view showing a schematic configuration of a cryopump according to a fifth embodiment. The cryopump according to the fifth embodiment is a cryopump 500 including the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0123] 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.

[0124] According to the fifth embodiment, a cryopump with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0125] Sixth embodiment The superconducting magnet of the sixth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the contents that overlap with the fourth embodiment will be omitted.

[0126] 6 is a perspective view showing a schematic configuration of a superconducting magnet according to a sixth embodiment. The superconducting magnet according to the sixth embodiment is a superconducting magnet 600 for a magnetic levitation train equipped with the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0127] 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.

[0128] According to the sixth embodiment, a refrigerator with excellent characteristics is used, thereby making it possible to realize a superconducting magnet with excellent characteristics.

[0129] Seventh embodiment The nuclear magnetic resonance imaging apparatus of the seventh embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the contents that overlap with the fourth embodiment will be omitted.

[0130] 7 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance imaging apparatus according to a seventh embodiment. The nuclear magnetic resonance imaging (MRI) apparatus according to the seventh embodiment is a nuclear magnetic resonance imaging apparatus 700 including the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0131] 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.

[0132] According to the seventh embodiment, a nuclear magnetic resonance imaging apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0133] Eighth embodiment The nuclear magnetic resonance apparatus of the eighth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the contents that overlap with the fourth embodiment will be omitted.

[0134] 8 is a cross-sectional view showing a schematic configuration of a nuclear magnetic resonance apparatus according to an eighth embodiment. The nuclear magnetic resonance (NMR) apparatus according to the eighth embodiment is a nuclear magnetic resonance apparatus 800 including the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0135] 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.

[0136] According to the eighth embodiment, a nuclear magnetic resonance apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0137] Ninth embodiment The magnetic field application type single crystal pulling apparatus of the ninth embodiment includes the refrigerator of the fourth embodiment. In the following, some of the contents that overlap with the fourth embodiment will be omitted.

[0138] 9 is a perspective view showing a schematic configuration of a magnetic field application type single crystal pulling apparatus according to the ninth embodiment. The magnetic field application type single crystal pulling apparatus according to the ninth embodiment is a magnetic field application type single crystal pulling apparatus 900 including the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0139] 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.

[0140] According to the ninth embodiment, a magnetic field application type single crystal pulling apparatus with excellent characteristics can be realized by using a refrigerator with excellent characteristics.

[0141] (Tenth embodiment) The helium recondensing device of the tenth embodiment includes the refrigerator of the fourth embodiment. Hereinafter, some of the contents that overlap with the fourth embodiment will be omitted.

[0142] 10 is a schematic diagram showing a schematic configuration of a helium recondensation apparatus according to a tenth embodiment. The helium recondensation apparatus according to the tenth embodiment is a helium recondensation apparatus 1000 including the regenerative cryogenic refrigerator 300 according to the fourth embodiment.

[0143] The helium recondensation device 1000 includes a regenerative cryogenic refrigerator 300 , an evaporation pipe 1001 , and a liquefaction pipe 1002 .

[0144] 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.

[0145] 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.

[0146] According to the tenth embodiment, a refrigerator with excellent characteristics is used, thereby making it possible to realize a helium recondensing device with excellent characteristics. EXAMPLES

[0147] Examples of the embodiment, comparative examples, and their evaluation results will be described below.

[0148] Example 1 A HoNiSi3 mother alloy was prepared by high-frequency induction melting. Next, the HoNiSi3 mother alloy was melted at about 1500°C. Next, the molten metal was dropped onto a rotating disk in an argon atmosphere at a pressure of about 101 kPa to be rapidly cooled and solidified. The rotation speed of the rotating disk was controlled so that the quenching speed of the molten metal was about 1000°C / s, and the cold storage material particles of Example 1 were produced.

[0149] In the heat regenerator particles of Example 1, the first element is holmium (Ho) and the second element is silicon (Si). In the heat regenerator particles of Example 1, the first phase is a phase in which the atomic concentration of silicon (Si) is greater than 70 atomic %.

[0150] The produced cold storage material particles were measured by powder X-ray diffraction. The diffraction pattern obtained by the measurement was subjected to Rietveld analysis. From the Rietveld analysis, the ratio ((Ib+Ic) / Ia) of the sum of the second and third peak intensities to the first peak intensity was calculated, where Ia is the first peak intensity corresponding to the (131) plane of the SmNiGe3 type crystal phase, Ib is the second peak intensity corresponding to the (131) plane of the CeNiSi2 type crystal phase, and Ic is the third peak intensity corresponding to the (111) plane of the CaF2 type crystal phase.

[0151] The cold storage material particles were crushed in an agate mortar and passed through a 500 mesh sieve to prepare a powder, which was used as a measurement sample for the powder X-ray diffraction method.

[0152] The area ratio of the first phase was measured for the produced heat accumulator particles. A backscattered electron image of the cross section of the heat accumulator particles was observed with a scanning electron microscope. The area occupied by the particles identified as the first phase in the cross section was measured using image processing software ImageJ. Whether the particles were the first phase or not was determined by energy dispersive X-ray spectroscopy.

[0153] The maximum volumetric heat capacity of the produced heat accumulator particles was measured using a Physical Property Measurement System (PPMS).

[0154] The ratio of the cold storage material particles with a circularity of 0.5 or less was measured from the optical microscope images of the manufactured cold storage material particles. The image processing software ImageJ was used for the measurement.

[0155] The results of the above measurements are shown in Table 1. In Table 1, when the ratio of cold storage material particles with a circularity R of 0.5 or less is 5% or less, the spheroidization of the particles is rated as "Good." Also, when the ratio of cold storage material particles with a circularity R of 0.5 or less is more than 5%, the spheroidization of the particles is rated as "No Good."

[0156] (Examples 2 to 5) Except for changing the rotation speed of the rotating disk to change the quenching rate of the molten metal, the cold storage material particles were produced in the same manner as in Example 1. When the quenching rate of the molten metal was to be increased, the rotation speed was increased, and when the quenching rate of the molten metal was to be decreased, the rotation speed was decreased.

[0157] The same measurements were carried out as in Example 1. The results are shown in Table 1.

[0158] (Examples 6 to 9) Except for changing the melting temperature in addition to changing the quenching rate of the molten metal by changing the rotation speed of the rotating disk, the cold storage material particles were produced in the same manner as in Example 1. When the quenching rate of the molten metal was to be increased, the rotation speed was increased, and when the quenching rate of the molten metal was to be decreased, the rotation speed was decreased.

[0159] The same measurements were carried out as in Example 1. The results are shown in Table 1.

[0160] Example 10 The cold storage particles were produced in the same manner as in Example 1, except that the HoNiGe3 master alloy was used.

[0161] In the heat regenerator particles of Example 10, the first element is holmium (Ho) and the second element is germanium (Ge). In the heat regenerator particles of Example 10, the first phase is a phase in which the atomic concentration of germanium (Ge) is greater than 70 atomic %.

[0162] The same measurements were carried out as in Example 1. The results are shown in Table 1.

[0163] Example 11 The regenerator particles were produced in the same manner as in Example 1, except that a GdNiSi3 master alloy was used.

[0164] In the regenerator particles of Example 11, the first element is gadolinium (Gd) and the second element is silicon (Si). In the regenerator particles of Example 11, the first phase is a phase in which the atomic concentration of silicon (Si) is greater than 70 atomic %.

[0165] The same measurements were carried out as in Example 1. The results are shown in Table 1.

[0166] Example 12 The regenerator particles were produced in the same manner as in Example 1, except that a DyNiSi3 master alloy was used.

[0167] In the heat regenerator particles of Example 12, the first element is dysprosium (Dy) and the second element is silicon (Si). In the heat regenerator particles of Example 12, the first phase is a phase in which the atomic concentration of silicon (Si) is greater than 70 atomic %.

[0168] Comparative Example 1 The regenerator particles were produced in the same manner as in Example 1, except that the rotation speed of the rotating disk was reduced and the quenching speed of the molten metal was slower than in the Example.

[0169] The same measurements were carried out as in Example 1. The results are shown in Table 1.

[0170] Comparative Example 2 The regenerator particles were produced in the same manner as in Example 1, except that the rotation speed of the rotating disk was increased and the quenching speed of the molten metal was increased compared to the example.

[0171] The same measurements were carried out as in Example 1. The results are shown in Table 1.

[0172] [Table 1]

[0173] In all of Examples 1 to 12, the particle size of the cold storage material particles having a circularity R of more than 0.5 was in the range of 50 μm to 3 mm. In all of Examples 1 to 12, the aspect ratio of the cold storage material particles having a circularity R of more than 0.5 was in the range of 1 to 5.

[0174] As is clear from Table 1, when the ratio ((Ib+Ic) / Ia) of the sum of the second peak intensity and the third peak intensity to the first peak intensity is in the range of 0.01 to 0.3, the maximum volumetric specific heat is 0.4 or more. For example, the maximum volumetric specific heat of HoCu2 is about 0.4, and when the ratio ((Ib+Ic) / Ia) is in the range of 0.01 to 0.3, a maximum volumetric specific heat larger than that of HoCu2 can be obtained.

[0175] As is clear from Table 1, when the ratio ((Ib+Ic) / Ia) of the sum of the second peak intensity and the third peak intensity to the first peak intensity is in the range of 0.01 to 0.3, the ratio of cold accumulator particles having a circularity R of 0.5 or less is 5% or less. Therefore, when the ratio ((Ib+Ic) / Ia) is in the range of 0.01 to 0.3, the cold accumulator particles are easily spherical.

[0176] As is clear from Table 1, when the area ratio of the first phase is in the range of 0.01% to 45%, the maximum value of the volumetric specific heat is 0.4 or more. When the area ratio of the first phase is in the range of 0.01% to 45%, the maximum value of the volumetric specific heat is larger than that of HoCu2.

[0177] As is clear from Table 1, when the area ratio of the first phase is in the range of 0.01% to 45%, the ratio of the cold storage material particles having a circularity R of 0.5 or less is 5% or less. Therefore, when the area ratio of the first phase is in the range of 0.01% to 45%, the cold storage material particles are easily spherical.

[0178] 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.

[0179] The technical solutions of the present invention are described below, and are included in the scope of the present invention.

[0180] (Technical proposal 1) at least one first element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); Nickel (Ni) and at least one second element selected from the group consisting of silicon (Si) and germanium (Ge); SmNiGe3 type crystal phase, A cold storage material particle comprising at least one of a CeNiSi2 type crystal phase and a CaF2 type crystal phase.

[0181] (Technical proposal 2) The peak intensity of the peak corresponding to the (131) plane of the SmNiGe3 type crystal phase obtained by powder X-ray diffraction is referred to as the first peak intensity. The peak intensity of the peak corresponding to the (131) plane of the CeNiSi2 type crystal phase obtained by powder X-ray diffraction is referred to as the second peak intensity. When the peak intensity of the peak corresponding to the (111) plane of the CaF2 type crystal phase obtained by powder X-ray diffraction is defined as the third peak intensity, The heat storage material particles according to Technical Proposal 1, wherein the ratio of the sum of the second peak intensity and the third peak intensity to the first peak intensity is 0.01 or more and 0.3 or less.

[0182] (Technical proposal 3) at least one first element selected from the group consisting of yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); Nickel (Ni) and at least one second element selected from the group consisting of silicon (Si) and germanium (Ge); SmNiGe3 type crystal phase, a first phase having an atomic concentration of the at least one second element greater than 70 atomic %.

[0183] (Technical proposal 4) The heat storage material particles according to Technical Proposal 3, wherein the area ratio of the first phase in a cross section is 0.01% or more and 45% or less.

[0184] (Technical proposal 5) If the perimeter of the projected image is L and the actual area of ​​the projected image is A, then 4πA / L 2 The cold storage material particles according to any one of Technical Schemes 1 to 4, wherein the circularity R represented by the formula (1) is greater than 0.5.

[0185] (Technical proposal 6) The cold storage material particles according to any one of Technical Schemes 1 to 5, having a particle size of 50 μm or more and 3 mm or less.

[0186] (Technical proposal 7) The maximum volumetric specific heat in the temperature range below 25K is 0.38 J / (cm 3 The cold storage material particles according to any one of Technical Schemes 1 to 6, wherein the cold storage material particles have a molecular weight of 1.0 or more, and the molecular weight of the cold storage material particles is 1.0 or more.

[0187] (Technical proposal 8) A group of cold storage particles containing 90% or more of the cold storage particles described in any one of Technical Schemes 1 to 7.

[0188] (Technical proposal 9) A heat storage device filled with a plurality of heat storage material particles described in any one of Technical Solutions 1 to 7.

[0189] (Technical proposal 10) A refrigerator equipped with a regenerator as described in Technical Proposal 9.

[0190] (Technical proposal 11) A cryopump equipped with a refrigerator described in Technical Proposal 10.

[0191] (Technical proposal 12) A superconducting magnet equipped with a refrigerator described in Technical Proposal 10.

[0192] (Technical proposal 13) A nuclear magnetic resonance imaging device equipped with a refrigerator described in Technical Proposal 10.

[0193] (Technical proposal 14) A nuclear magnetic resonance apparatus equipped with a refrigerator described in Technical Proposal 10.

[0194] (Technical proposal 15) A magnetic field application type single crystal pulling apparatus equipped with the refrigerator described in Technical Proposal 10.

[0195] (Technical proposal 16) A helium recondensing device equipped with a refrigerator described in Technical Proposal 10. [Explanation of symbols]

[0196] 100 Cold storage material particles 115 Second regenerator (regenerator) 200 Cold storage material particles 210 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. At least one first 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); Nickel (Ni), at least one second element selected from the group consisting of silicon (Si) and germanium (Ge); SmNiGe ３ A type crystal phase, CeNiSi ２ Type crystal phase and CaF ２ and at least one of the above-mentioned crystal phases.

2. SmNiGe obtained by powder X-ray diffraction method ３ The peak intensity of the peak corresponding to the (131) plane of the crystalline phase is referred to as the first peak intensity (Ia), CeNiSi obtained by powder X-ray diffraction method ２ The peak intensity of the peak corresponding to the (131) plane of the crystalline phase is the second peak intensity (Ib), CaF obtained by powder X-ray diffraction method ２ When the peak intensity of the peak corresponding to the (111) plane of the crystalline phase is the third peak intensity (Ic), 2. The regenerator particle according to claim 1, wherein a ratio ((Ib+Ic) / Ia) of a sum of the second peak intensity and the third peak intensity to the first peak intensity is 0.01 or more and 0.3 or less.

3. At least one first 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); Nickel (Ni), at least one second element selected from the group consisting of silicon (Si) and germanium (Ge); SmNiGe ３ A type crystal phase, a first phase having an atomic concentration of the at least one second element greater than 70 atomic %.

4. 4. The regenerator particle according to claim 3, wherein the area ratio of the first phase in a cross section is 0.01% or more and 45% or less.

5. When the perimeter of the projected image is L and the actual area of ​​the projected image is A, 4πA / L ２ 4. The cold storage material particle according to claim 1, wherein the circularity R represented by the formula (I) is greater than 0.

5.

6. 4. The cold storage material particles according to claim 1, wherein the particle size is from 50 μm to 3 mm.

7. The maximum volumetric specific heat in the temperature range below 25K is 0.38 J / (cm ３ The cold storage material particles according to claim 1 or 3, wherein the heat capacity is 100% or more.

8. A group of cold accumulator particles comprising 90% or more of the cold accumulator particles according to claim 1 or 3.

9. A regenerator filled with a plurality of the regenerator particles according to claim 1 or 3.

10. A refrigerator comprising the regenerator according to claim 9.

11. A cryopump comprising the refrigerator according to claim 10.

12. A superconducting magnet comprising the refrigerator according to claim 10.

13. A nuclear magnetic resonance imaging apparatus comprising the refrigerator according to claim 10.

14. A nuclear magnetic resonance apparatus comprising the refrigerator according to claim 10.

15. A magnetic field application type single crystal pulling apparatus comprising the refrigerator according to claim 10.

16. A helium recondensing device comprising the refrigerator according to claim 10.

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