JP2010077484A - Magnetic material for magnetic refrigeration, magnetic refrigeration device, and magnetic refrigeration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an La(Fe, Co, Si)<SB>13</SB>based magnetic material for magnetic refrigeration which is easily producible, is also suitable for magnetic refrigeration of an AMR (Active Magnetic Regenerative Refrigeration) system, and has high magnetic refrigeration properties, to provide a magnetic refrigeration device using the magnetic material, and to provide a magnetic refrigeration system. <P>SOLUTION: The magnetic material for magnetic refrigeration includes: an La(Fe, Co, Si)<SB>13</SB>phase with an NaZn<SB>13</SB>type crystal structure as the main phase; and an La(Fe, Co)Si phase with a CeFeSi type crystal structure, and in which the volume occupancy ratio of the La(Fe, Co, Si)<SB>13</SB>phase is ≥70%, and the material is composed of almost spherical grains with the maximum size of 0.1 to 2 mm. The magnetic refrigeration device and magnetic refrigeration system use the same. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic material for magnetic refrigeration having a magnetocaloric effect, a magnetic refrigeration device using the same, and a magnetic refrigeration system.

Currently, most of room temperature refrigeration technologies closely related to human daily life, such as refrigerators, freezers, and indoor air-conditioners, use a gas compression / expansion cycle. However, with regard to the refrigeration technology based on the gas compression / expansion cycle, environmental destruction due to the environmental discharge of the specific chlorofluorocarbon gas becomes a major problem, and there is a concern about the influence of the alternative chlorofluorocarbon on the environment. Against this background, efforts are being made using natural refrigerants (CO ₂ , ammonia, etc.) and isobutane with low environmental risks, and there is no problem of environmental destruction associated with the disposal of working gas, and it is safe and clean. There is a need for practical use of highly efficient refrigeration technology.

  As one of such environmentally friendly and highly efficient refrigeration technologies, the expectation for magnetic refrigeration has increased, and research and development of magnetic refrigeration technologies for room temperature has been activated. The magnetic refrigeration technology is based on the magnetocaloric effect in iron (Fe) discovered by Warburg in 1881. The magnetocaloric effect is a phenomenon in which, when an externally applied magnetic field is changed with respect to a magnetic substance in an adiabatic state, the temperature of the magnetic substance changes. Physically, it is explained that the energy transfer occurs between the electron system and the lattice system as a result of the change in the entropy of the magnetic spin system inside the magnetic material, and as a result, the temperature of the magnetic material changes.

In the early 1900s, refrigeration systems using paramagnetic salts and paramagnetic compounds represented by Gd ₂ (SO ₄ ) ₃ .8H ₂ O and Gd ₃ Ga ₅ O ₁₂ having magnetocaloric effects were developed. However, this is mainly applied to a cryogenic region of 20K or less, and a magnetic field of about 10 T by a superconducting magnet is required.

Since the 1970s, researches using the magnetic transition between the paramagnetic state and the ferromagnetic state in ferromagnetic materials have been actively conducted to realize magnetic refrigeration in a high temperature region, and have reached the present day. As a result of these studies, an AMR method (Active Magnetic Regenerative Refrigeration) has been proposed as a useful refrigeration method for the normal temperature range, and lanthanum rare earth elements such as Pr, Nd, Dy, Er, Tm, and Gd, Gd-Y, two or more kinds of rare earth alloy materials, such as _{Gd-Dy, Gd 5 (Ge} , Si) 4 based material, MnFe (P, as) based material, Mn (as, Sb) based material, La ( Magnetic materials such as Fe, Si) _13- based substances have been proposed. In particular, a La (Fe, Co, Si) _13- based material is promising as a magnetic refrigeration material because a relatively large magnetic entropy change is obtained at a low magnetic field and there is almost no hysteresis with respect to temperature.

In order to produce La (Fe, Co, Si) ₁₃ phases, first, raw materials such as La, Fe, Si, Co, etc. are adjusted by the stoichiometric ratio, and then melted by an arc melting method or a high frequency melting method. Integrate. However, since La and Fe are completely non-solid solution in terms of metal phase, they are separated into two phases of an Fe-rich phase and an La-rich phase only through a simple dissolution process. The former is an Fe alloy phase (hereinafter also referred to as α-Fe phase) having a bcc crystal structure containing Si and containing Fe as a main constituent element. The latter is a phase containing Si and having La as a main constituent element.

In a simple melting process such as an arc melting method or a high-frequency melting method, a coarse crystal phase of an Fe-rich phase and an La-rich phase exhibits a complicated metal structure (see, for example, Patent Document 1). Subsequently, the integrated alloy is heat-treated at a temperature of about 900 to 1100 ° C. for a long time, so that a La (Fe, Co, Si) ₁₃ phase is gradually generated based on the mutual diffusion of elements. . Thus, the bulk La (Fe, Co, Si) ₁₃ phase generation process to which a general dissolution method is applied requires heat treatment at a relatively high temperature. And when the metal structure is coarse, it has the difficulty that a long-term heat treatment is required.

In order to eliminate the need for long-time heat treatment in the La (Fe, Si) ₁₃ phase generation process, for example, Patent Document 2 describes that a ribbon manufacturing process by a liquid quenching method is applied. Patent Document 1 describes a magnetic refrigeration material containing at least one metalloid element selected from B, C, P, As, Se, Sb, Te, Bi, Po, and At. Here, by adding a metalloid element such as B or C in the range of 1.8 atomic% or more and 5.4 atomic% or less, 75 vol% or more of La (Fe, Si) ₁₃ phase is obtained immediately after melt casting. Is generated.

On the other hand, in order to apply to magnetic refrigeration such as the AMR method, it is desirable that the magnetic material is processed into a practical spherical particle shape. For this purpose, a mother alloy prepared by melting is heat-treated to form a La (Fe, Si) ₁₃ phase and then fragmented, and a mother alloy is fragmented and then heat-treated to obtain La (Fe, Si) _13. There are ways to generate phases. Among these methods, the former method has a drawback that the filling rate of the magnetic refrigeration material is lowered depending on the pulverized shape because the mother alloy after heat treatment is pulverized into small pieces. Furthermore, since cracks (cracks) enter into the small piece due to the stress at the time of crushing, it becomes fragile and causes problems such as pulverization during magnetic refrigeration operation and hindering the operation.

As a method of melting an alloy material (mother alloy) into pieces, generally known are an atomizing method, a rotating disk method (RDP method), a rotating electrode method (REP method), and the like. A spherical particle (magnetic refrigeration material particle) suitable for magnetic refrigeration such as the AMR method can be obtained by heat-treating the spherical particle produced by these methods to generate a La (Fe, Co, Si) ₁₃ phase. it can. In particular, the rotating electrode method capable of producing spherical particles without going through the melting process of the mother alloy in the crucible applies La (Fe, Co, Si) _13- based material to magnetic refrigeration such as AMR method. This is suitable as a method for producing spherical particles. According to the rotating electrode method, spherical particles close to a true sphere can be produced efficiently, but there is a problem that segregation of the mother alloy is strongly reflected in the produced particles.
JP 2004-099928 A JP 2004-100043 A

As described above, the conventional La (Fe, Co, Si) _13- based magnetic material takes a long time to manufacture due to the segregation of the composition between particles due to the segregation of the mother alloy when it is fragmented and the coarsening of the structure of the particles. There was a problem that the surface condition deteriorated. In addition, the spherical particles produced thereby vary in the content of La (Fe, Co, Si) ₁₃ phase, the peak temperature of the entropy change, and the like based on the variation in the composition of each particle during production. For this reason, when spherical particles are filled in a container and applied to an AMR type magnetic refrigeration, the optimum operation temperature varies with respect to the magnetocaloric effect, and a sufficient refrigeration effect cannot be obtained in a thermal cycle test. there were.

The present invention has been made in consideration of the above circumstances, and the object of the present invention is La (Fe, Co) which is easy to manufacture and has high magnetic refrigeration characteristics suitable for AMR magnetic refrigeration. , Si) To provide a _13- based magnetic material for magnetic refrigeration, a magnetic refrigeration device using the same, and a magnetic refrigeration system.

The magnetic material for magnetic refrigeration according to the first aspect of the present invention includes a La (Fe, Co, Si) ₁₃ phase having a NaZn ₁₃ type crystal structure as a main phase and La (Fe, Co) having a CeFeSi type crystal structure. It is a substantially spherical particle containing a Si phase, wherein the La (Fe, Co, Si) ₁₃ phase has a volume occupancy of 70% or more and a maximum diameter of 0.1 mm or more and 2 mm or less. .

Magnetic materials for magnetic refrigeration in the second aspect of the present invention includes a _{La (Fe, Co, Si)} 13 phase having a NaZn ₁₃ type crystal structure, La (Fe, Co) having a CeFeSi type crystal structure and a Si phase In the X-ray diffraction pattern, when the diffraction intensity of the main peak of the La (Fe, Co, Si) ₁₃ phase is I ₁ , and the diffraction intensity of the main peak of the La (Fe, Co) Si phase is I ₂ , I ₂ / (I ₁ + I ₂ ) ≦ 0.1, and substantially spherical particles having a maximum diameter of 0.1 mm to 2 mm.

In the magnetic material for magnetic refrigeration according to the first or second aspect, La _x Fe _100-xyz Co _y Si _z (4 <x <15 at.%, 0 <y ≦ 10 at.%, 3.5 ≦ z ≦ 23.5 at.%) Is desirable.

  A magnetic refrigeration device according to an aspect of the present invention is a magnetic refrigeration device using a liquid refrigerant, a heat exchange container filled with a magnetic material, and a magnetic field generating unit that applies and removes a magnetic field to and from the magnetic material, A refrigerant circuit formed by connecting a low temperature side heat exchange section, a high temperature side heat exchange section, the heat exchange vessel, the low temperature side heat exchange section, and the high temperature side heat exchange section, and circulating the liquid refrigerant; At least a part of the magnetic material is the magnetic material for magnetic refrigeration according to the first or second aspect.

  The magnetic refrigeration system according to one aspect of the present invention includes the above-described magnetic refrigeration device, a cooling unit thermally connected to the low temperature side heat exchange unit, and exhaust heat thermally connected to the high temperature side heat exchange unit. And comprising a part

According to the present invention, an La (Fe, Co, Si) _13- based magnetic material for magnetic refrigeration having high magnetic refrigeration characteristics, which is easy to manufacture and suitable for AMR magnetic refrigeration, and a magnetic material using the same A refrigeration device and a magnetic refrigeration system can be provided.

(First embodiment)
The magnetic material for magnetic refrigeration according to the first embodiment of the present invention includes a La (Fe, Co, Si) ₁₃ phase having a NaZn ₁₃ type crystal structure as a main phase, and La (Fe, Co, Si having a CeFeSi type crystal structure. Co) Si phase. Here, the volume occupancy in the magnetic material for magnetic refrigeration of La (Fe, Co, Si) ₁₃ phase is 70% or more. And it is a substantially spherical particle | grain with a maximum diameter of 0.1 mm or more and 2 mm or less. The magnetic material for magnetic refrigeration according to the present embodiment also contains an α-Fe phase.

  In the present specification, the main phase means a phase having the highest volume occupation ratio among all the crystalline phases and non-crystalline phases constituting the magnetic material particles for magnetic refrigeration. Here, the volume occupancy of the phase in the magnetic material for magnetic refrigeration is obtained from the cross-sectional SEM photograph to obtain the ratio of the area occupied by each phase of each particle to the entire particle cross-sectional area, and the average of about 10 particles. Can be estimated. Further, the measurement of the maximum diameter of the particles can be evaluated by calipers under visual observation, or by direct observation under a microscope or measurement with a micrograph.

The magnetic material for magnetic refrigeration of the present embodiment has a La (Fe, Co, Si) ₁₃ phase as a main phase, and the volume occupancy in the magnetic material for magnetic refrigeration is 70% or more, so that it is low in the normal temperature range. A relatively large magnetic entropy change is obtained with a magnetic field. Therefore, this material has high magnetic refrigeration characteristics that can realize a large refrigeration temperature difference. From the viewpoint of realizing high magnetic refrigeration characteristics, it is desirable that the volume occupancy ratio of the La (Fe, Co, Si) ₁₃ phase magnetic material for magnetic refrigeration is 80% or more.

  The magnetic material for magnetic refrigeration according to the present embodiment is suitable for AMR magnetic refrigeration because it is a substantially spherical particle having a maximum diameter of 0.1 mm to 2 mm. In order for a magnetic refrigeration device using liquid refrigerant to achieve high refrigeration capacity, heat exchange between the magnetic material filled in the heat exchange container and the liquid refrigerant is sufficiently performed to achieve high heat exchange efficiency. is important.

  And it is necessary to ensure the flow path of a liquid refrigerant, maintaining the high filling rate of a magnetic material so that heat exchange with a magnetic material and a liquid refrigerant may fully be performed. For this purpose, the magnetic material for magnetic refrigeration is preferably substantially spherical. Moreover, it is preferable to reduce the particle size to increase the specific surface area of the magnetic particles, but if the particle size is too small, the pressure loss of the refrigerant increases. Therefore, in order to reduce the pressure loss and keep the heat exchange efficiency favorable, the magnetic particles of the present embodiment have a maximum diameter of 0.1 mm to 2 mm.

In addition, the magnetic material for magnetic refrigeration according to the present embodiment containing 70% or more of La (Fe, Co, Si) ₁₃ phase has a particle shape that is most easily used in the AMR magnetic refrigeration as it is, and thus is manufactured. The complexity of the process can be reduced.

  Furthermore, the magnetic material for magnetic refrigeration according to the present embodiment has an advantage that the composition of each particle is stabilized during the production. Accordingly, when a large number of particles are used as a particle group in an AMR type magnetic refrigeration device, it is possible to suppress a decrease in refrigeration characteristics due to variation in particle composition.

From the viewpoint of reducing the surface efficiency of the particles due to the high temperature of the heat treatment during the magnetic material production and reducing the low efficiency due to the prolongation, and stabilizing the composition of each particle, other than the La (Fe, Co, Si) ₁₃ phase The volume occupancy of the phase is preferably about 10%.

The magnetic material for magnetic refrigeration in this embodiment, the composition formula _{La x Fe 100-x-y} -z Co y Si z (4 <x <15at.%, 0 <y ≦ 10at.%, 3.5 ≦ z ≦ 23.5 at.%) Is desirable. The composition of the magnetic material for magnetic refrigeration can be obtained by performing plasma emission spectroscopic analysis with particles of several grams.

The content of La is 4 at. % Or 15 at. If it exceeds 50% or more, it is considered that a surplus that cannot form the La (Fe, Co, Si) ₁₃ phase tends to remain, and a volume occupation ratio of 70% or more cannot be secured. The content of La is 7 at. % Or more and 10 at. % Or less is more preferable. The Si content is 3.5 at. Even if it is less than%, the production efficiency of particles having a La (Fe, Co, Si) ₁₃ phase is lowered. Further, the Si content is 23.5 at. If the content exceeds 50%, the characteristics of the magnetic refrigeration material particles will deteriorate. From the viewpoint of controlling the magnetic transition temperature, the Co content is 10 at. % Or less is desirable. However, the Co is contained, it is necessary to ferromagnetic transition temperature (T _C) to room temperature range.

Next, the manufacturing method of the magnetic material for magnetic refrigeration of this Embodiment is demonstrated. First, La, Fe, Co, and Si raw materials are mixed so as to have a stoichiometric ratio of La (Fe, Co, Si) ₁₃ to prepare a raw material mixture. This raw material mixture is melted in a high-frequency melting furnace, and a columnar mother alloy is produced using a mold. This columnar mother alloy is composed of an Fe-rich phase and an La-rich phase.

Next, spherical particles are produced by the rotating electrode method using this columnar mother alloy. Then, the spherical particles were wrapped in Ta-night and enclosed in a quartz tube in an Ar atmosphere having a degree of vacuum of about 1 × 10 ⁻⁶ Torr. Then, heat treatment is performed at 1030 ° C. for one week, and the Fe-rich phase and the La-rich phase are reacted to form the La (Fe, Co, Si) ₁₃ phase. At this time, conditions are set so that the volume occupancy of the La (Fe, Co) Si phase is 15% or less. In this way, the magnetic material for magnetic refrigeration according to the present embodiment is manufactured.

  In this manufacturing method, the composition ratio of the spherical particles varies due to the coarse two-phase separation state of the mother alloy, and this becomes a factor of deteriorating the characteristics of the magnetic refrigeration material particles. That is, when spherical particles are produced by the rotating electrode method using a mother alloy having a metal structure in which a coarse Fe-rich phase and a La-rich phase are partially segregated, the variation in composition among the spherical particles increases.

Even if heat treatment is performed on the spherical particles in such a state, the characteristic variation of the magnetic refrigeration material particles becomes large based on the variation in the composition of the spherical particles, and the mutual diffusion of elements is less likely to occur, so La (Fe, Co) A large amount of Si phase remains, and the production efficiency of the La (Fe, Co, Si) ₁₃ phase is lowered.

  For example, magnetic refrigeration material particles (spherical particles) produced using a master alloy having a metal structure in which a coarse Fe-rich phase and a La-rich phase are partially segregated have a peak temperature of entropy change, etc. Variation occurs. When such spherical particles are filled in a container and applied to an AMR type magnetic refrigeration, the optimum operating temperature varies with respect to the magnetocaloric effect based on the variation among the particles, and sufficient refrigeration is possible in the thermal cycle test. The effect cannot be obtained.

  Therefore, when preparing a columnar master alloy by melting the raw material mixture in a high-frequency melting furnace, it is important to increase the cooling rate and prepare a columnar master alloy in which the structure of the Fe-rich phase and the La-rich phase are finely interlaced. It becomes. In order to increase the cooling rate, for example, there is a method of making the shape of the mold so that the cooling rate is increased.

(Second Embodiment)
The second magnetic material for magnetic refrigeration in the form of embodiment of the present invention includes a _{La (Fe, Co, Si)} 13 phase having a NaZn ₁₃ type crystal structure, La (Fe, Co) having a CeFeSi type crystal structure Si phase Containing. Here, in the X-ray diffraction pattern, when the diffraction intensity of the main peak of the La (Fe, Co, Si) ₁₃ phase is I ₁ and the diffraction intensity of the main peak of the La (Fe, Co) Si phase is I ₂ , I ₂ / (I ₁ + I ₂ ) ≦ 0.1. And it is a substantially spherical particle | grain with a maximum diameter of 0.1 mm or more and 2 mm or less.

  The magnetic material for magnetic refrigeration of the present embodiment is the same as the magnetic material for magnetic refrigeration of the first embodiment except that the specific method of composition is different. Therefore, it has the same operation and effect as the first embodiment.

(Third embodiment)
The magnetic refrigeration device according to the third embodiment of the present invention is an AMR type magnetic refrigeration device using a liquid refrigerant. A heat exchange container filled with the magnetic material, magnetic field generating means for applying and removing a magnetic field to and from the magnetic material, a low temperature side heat exchange unit, and a high temperature side heat exchange unit are provided. Furthermore, a heat exchanger vessel, a low temperature side heat exchange part, and a high temperature side heat exchange part are connected, and the refrigerant circuit which circulates a liquid refrigerant is provided. At least a part of the magnetic material filled in the heat exchange container is the magnetic material for magnetic refrigeration according to the first or second embodiment. About the magnetic material, description is abbreviate | omitted about the content which overlaps with 1st or 2nd embodiment.

  FIG. 2 is a schematic structural cross-sectional view of the magnetic refrigeration device of the present embodiment. This magnetic refrigeration device uses, for example, water as a liquid refrigerant. A low temperature side heat exchange unit 21 is provided on the low temperature end side of the heat exchange vessel 10, and a high temperature side heat exchange unit 31 is provided on the high temperature end side. And the switching means 40 of the direction through which a refrigerant | coolant flows is provided between the low temperature side heat exchange part 21 and the high temperature side heat exchange part 31. As shown in FIG. Further, a refrigerant pump 50 that is a refrigerant transport means is connected to the switching means 40. And the heat exchange container 10, the low temperature side heat exchange part 21, the switching means 40, and the high temperature side heat exchange part 31 are connected by piping, and form the refrigerant circuit which circulates a liquid refrigerant.

  The heat exchange vessel 10 is filled with the magnetic material 12 described in the first or second embodiment having a magnetocaloric effect. Outside the heat exchange vessel 10, a horizontally movable permanent magnet 14 is arranged as a magnetic field generating means.

  Next, the outline of the operation of the magnetic refrigeration device of the present embodiment will be described with reference to FIG. When the permanent magnet 14 is disposed at a position facing the heat exchange container 10 (position shown in FIG. 2), a magnetic field is applied to the magnetic material 12 in the heat exchange container 10. For this reason, the magnetic material 12 having a magnetocaloric effect generates heat. At this time, the liquid refrigerant is circulated in the direction from the heat exchange container 10 toward the high temperature side heat exchange unit 31 by the operation of the refrigerant pump 50 and the switching unit 40. The warm heat is transported to the high temperature side heat exchanging section 31 by the liquid refrigerant whose temperature is increased by the heat generation of the magnetic material 12.

  Thereafter, the permanent magnet 14 is moved from a position facing the heat exchange vessel 10 to remove the magnetic field with respect to the magnetic material 12. The magnetic material 12 absorbs heat by removing the magnetic field. At this time, the refrigerant pump 50 and the switching means 40 are operated to circulate the liquid refrigerant in the direction from the heat exchange vessel 10 toward the low temperature side heat exchange unit 21. The cold heat is transported to the low temperature side heat exchanging portion 21 by the liquid refrigerant cooled by the heat absorption of the magnetic material 12.

  By repeatedly moving the permanent magnet 14 and repeatedly applying and removing the magnetic field to and from the magnetic material 12 in the heat exchange container 10, a temperature gradient is generated in the magnetic material 12 in the heat exchange container 10. And the cooling of the low temperature side heat exchange part 21 is continued by the movement of the liquid refrigerant synchronized with the application / removal of the magnetic field.

  The magnetic refrigeration device of the present embodiment can achieve high heat exchange efficiency by using a magnetic material for magnetic refrigeration having a high magnetic refrigeration operating temperature.

  In the present embodiment, the magnetic material 12 in the heat exchange vessel 10 is not necessarily filled uniformly with one magnetic material having the same composition, but has two or more different compositions. May be filled.

  For example, the magnetic material includes the magnetic material for magnetic refrigeration described in the first or second embodiment, and a magnetic material having at least one other composition, and the plurality of magnetic materials for magnetic refrigeration are heated. The exchange container may be mixed and filled. Further, a plurality of magnetic materials for magnetic refrigeration may be packed in layers in the heat exchange container.

(Fourth embodiment)
A magnetic refrigeration system according to a fourth embodiment of the present invention includes a magnetic refrigeration device according to the third embodiment, a cooling unit thermally connected to a low temperature side heat exchange unit, and a high temperature side heat exchange unit. And an exhaust heat section that is thermally connected to. Hereinafter, the description overlapping the content described in the third embodiment is omitted.

  FIG. 3 is a schematic structural sectional view of the magnetic refrigeration system of the present embodiment. In addition to the magnetic refrigeration device of FIG. 1, this magnetic refrigeration system includes a cooling unit 26 that is thermally connected to the low-temperature side heat exchange unit 21, and an exhaust heat unit 36 that is thermally connected to the high-temperature side heat exchange unit 31. And.

  The low temperature side heat exchanging unit 21 includes a low temperature side water storage tank 22 for storing a low temperature refrigerant, and a low temperature side heat exchanger 24 provided in contact with the refrigerant inside thereof. Similarly, the high temperature side heat exchange part 31 is comprised by the high temperature side water tank 32 which stores a high temperature refrigerant | coolant, and the high temperature side heat exchanger 34 provided in the inside so that a refrigerant | coolant may be contact | connected. The cooling unit 26 is thermally connected to the low temperature side heat exchanger 24, and the exhaust heat unit 36 is thermally connected to the high temperature side heat exchanger 34.

  Here, this magnetic refrigeration system can be applied to a household refrigerator, for example. In this case, the cooling unit 26 is a freezing / refrigeration room that is an object to be cooled, and the heat exhausting unit 36 is, for example, a heat sink.

  The magnetic refrigeration system is not particularly limited. In addition to the above-mentioned domestic refrigerator-freezer, for example, it can be applied to refrigeration systems such as household refrigerator-freezers, household air conditioners, industrial refrigerator-freezers, large-sized refrigerator-freezers, liquefied gas storage / transport refrigerators, etc. is there. The required refrigeration capacity and control temperature range differ depending on the application location. However, the refrigerating capacity can be varied according to the amount of magnetic particles used. Further, the control temperature range can be adjusted to a specific temperature range because the magnetic transition temperature can be varied by controlling the material of the magnetic particles. Furthermore, the present invention can also be applied to air conditioning systems such as home air conditioners and industrial air conditioners that use the exhaust heat of the magnetic refrigeration device as heating. You may apply to the plant using both cooling and heat_generation | fever.

  With the magnetic refrigeration system of the present embodiment, a magnetic refrigeration system that improves the magnetic refrigeration efficiency can be realized.

  The embodiments of the present invention have been described above with reference to specific examples. The above embodiment is merely given as an example, and does not limit the present invention. In the description of the embodiment, the description of the magnetic refrigeration magnetic material, the magnetic refrigeration device, the magnetic refrigeration system, etc., which is not directly necessary for the explanation of the present invention is omitted, but the required magnetism. Elements relating to a magnetic material for refrigeration, a magnetic refrigeration device, a magnetic refrigeration system, and the like can be appropriately selected and used.

  In addition, all magnetic materials for magnetic refrigeration, magnetic refrigeration devices, and magnetic refrigeration systems that include elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention. The scope of the present invention is defined by the appended claims and equivalents thereof.

  Hereinafter, embodiments of the present invention will be described in detail.

(Examples 1-4)
Each raw material of La, Fe, Co, and Si was mixed and adjusted at a ratio shown in Table 1 to prepare a raw material mixture. This raw material mixture was melted in a high-frequency melting furnace to produce a columnar mother alloy. At this time, a mold having a shape capable of increasing the cooling rate was used.

  FIG. 4A shows a cross-sectional observation photograph of the metal structure of the mother alloy of Example 1 using an optical microscope. The light color portion is the Fe rich phase, and the dark color portion is the La rich phase. Fe-rich phase islands ranged from a few μm to 20-30 μm. And the structure which the Fe rich phase and the La rich phase minutely interlaced is exhibited.

Subsequently, spherical particles were produced by the rotating electrode method using this columnar mother alloy. The spherical particles were wrapped in Ta night and enclosed in a quartz tube in an Ar atmosphere with a vacuum degree of about 1 × 10 ⁻⁶ Torr. Then, heat treatment was performed at 1030 ° C. for one week to produce La (Fe, Co, Si) ₁₃ .

X-ray diffraction measurement was performed on the spherical particles. The peak shape of the X-ray diffraction pattern of Example 1 is shown in FIG. Since several grains are pulverized at the same time, it corresponds to looking at the average between the grains. ○ corresponds to the La (Fe, Co, Si) ₁₃ phase, and ▼ corresponds to the La (Fe, Co) Si phase. The peak intensity ratio I ₂ / (I _{1, where} the diffraction intensity of the main peak of the La (Fe, Co, Si) ₁₃ phase is I ₁ and the diffraction intensity of the main peak of the La (Fe, Co) Si phase is I _2. The results obtained for + I ₂ ) are shown in Table 2.

Table 3 shows the results of obtaining the volume occupancy of the La (Fe, Co, Si) ₁₃ phase from the cross-sectional SEM photograph.

Magnetization measurement was performed on several randomly extracted particles. The magnetic entropy change ΔS, which is an index of the magnetocaloric effect of a magnetic material used in magnetic refrigeration, is calculated by the following equation.
FIG. 6A shows the temperature dependence of ΔS in Example 1 with the applied magnetic field ΔH _ext = 640000 A / m (8 kOe) calculated using the equation (1) based on this measurement data. In addition, Table 4 shows the average value of ΔS for Example 1.

  Furthermore, the freezing temperature difference (ΔT) was evaluated by the following method. The sample was filled into a heat exchange vessel so that the sample did not move easily. Next, a thermocouple was inserted from a 0.8 mmφ hole opened in the center of the container upper lid so that the thermocouple was in the center of the sample container. Further, the entire sample container was covered with a heat insulating material and fixed to the sample holder in the thermostat. The sample holder is in a position where a magnetic field can be applied and removed by operation of the yoke magnet, and the constant temperature layer can adjust the internal temperature from the outside. After shutting off the inside of the thermostatic chamber from the outside, the temperature is adjusted and waits until the temperature inside the thermostatic bath becomes uniform.

Thereafter, the yoke magnet was operated to repeatedly apply and remove the magnetic field to the sample, and the temperature difference ΔT at that time was measured. Subsequently, after adjusting the temperature in the thermostat, the process of measuring the temperature difference ΔT accompanying the application / removal of the magnetic field of the sample was repeated, and ΔT at each temperature of the sample was evaluated. The results of Example 1 are shown in FIG. In addition, Table 5 shows ΔT _max of Examples 1 to 4.

(Comparative Examples 1 and 2)
In the same manner as in Example 1, except that each raw material of La, Fe, and Si is mixed and adjusted at a ratio shown in Table 1 to prepare a raw material mixture, and a mold having a shape that increases the cooling rate is not used. Spherical particles were produced. Moreover, the same evaluation as Example 1 was performed with respect to the produced spherical particle.

  FIG. 4B shows a cross-sectional observation photograph of the metal structure of the mother alloy of Comparative Example 1 using an optical microscope. Fe-rich phase islands are several tens to hundreds of tens of μm, which is larger than Example 1. That is, it has a metal structure in which coarse Fe-rich phase and La-rich phase are partially segregated.

The result of X-ray diffraction measurement performed on the spherical particles of Comparative Example 2 is shown in FIG. The peak intensity ratio I ₂ / (I _{1, where} the diffraction intensity of the main peak of the La (Fe, Co, Si) ₁₃ phase is I ₁ and the diffraction intensity of the main peak of the La (Fe, Co) Si phase is I _2. The results obtained for + I ₂ ) are shown in Table 2.

Table 3 shows the results of determining the volume occupancy of the La (Fe, Co, Si) ₁₃ phase from the cross-sectional SEM photograph.

The temperature dependence of ΔS is shown in FIG. Moreover, the result of having evaluated (DELTA) T in each temperature of the sample of the comparative example 1 is shown in FIG. ΔT _max is shown in Table 5.

As can be seen from Table 3, in the examples, the volume occupancy of the La (Fe, Co, Si) ₁₃ phase is 70% or more. On the other hand, in the comparative example, the volume occupancy of the La (Fe, Co, Si) ₁₃ phase is less than 70%.

As can be seen from Table 2, in the example, the diffraction intensity of the main peak of the La (Fe, Co, Si) ₁₃ phase is I ₁ and the diffraction intensity of the main peak of the La (Fe, Co) Si phase in the X-ray diffraction pattern. the when the _{I 2, I 2 / (I} 1 + I 2) is 0.1 or less. On the other hand, in a comparative example, it is larger than 0.1.

  As can be seen from FIGS. 6 (a) and 6 (b), it is difficult to say that both are uniform with respect to the magnitude of ΔS, but as can be seen from Table 4, the average value of ΔS in Example 1 compared to the comparative example. Has improved.

  As can be seen from FIG. 1 and Table 5, it was confirmed that ΔT in the spherical particles of Examples 1 to 4 gives larger ΔT than the spherical particles of Comparative Example 1.

  As described above, the effect of the present invention was confirmed by this example.

It is a figure which shows the evaluation result of (DELTA) T in each temperature of the sample of an Example and a comparative example. It is a typical structure sectional view of the magnetic refrigeration device of a 3rd embodiment. It is sectional drawing which shows the structure of the magnetic material in the heat exchange container of 4th Embodiment. It is a cross-sectional observation photograph of the mother alloy of an example and a comparative example. It is a figure which shows the X-ray-diffraction measurement result of an Example and a comparative example. It is a figure which shows the evaluation result of the temperature dependence of (DELTA) S of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Heat exchange container 12 Magnetic material 14 Permanent magnet 18 Partition 21 Low temperature side heat exchange part 22 Low temperature side water tank 24 Low temperature side heat exchanger 26 Cooling part 31 High temperature side heat exchange part 32 High temperature side water tank 34 High temperature side heat exchanger 36 Waste heat unit 40 switching means 50 refrigerant pump

Claims (5)

La (Fe, Co, Si) ₁₃ phase having NaZn ₁₃ type crystal structure as a main phase;
A La (Fe, Co) Si phase having a CeFeSi type crystal structure,
The volume occupancy of the La (Fe, Co, Si) ₁₃ phase is 70% or more;
A magnetic material for magnetic refrigeration, wherein the magnetic material is a substantially spherical particle having a maximum diameter of 0.1 mm to 2 mm. La (Fe, Co, Si) ₁₃ phase having NaZn ₁₃ type crystal structure;
A La (Fe, Co) Si phase having a CeFeSi type crystal structure,
When the diffraction intensity of the main peak of the La (Fe, Co, Si) ₁₃ phase is I ₁ and the diffraction intensity of the main peak of the La (Fe, Co) Si phase is I ₂ in the X-ray diffraction pattern, I ₂ / (I ₁ + I ₂ ) ≦ 0.1,
A magnetic material for magnetic refrigeration, wherein the magnetic material is a substantially spherical particle having a maximum diameter of 0.1 mm to 2 mm. La _x Fe _100-xyz Co _y Si _z (4 <x <15 at.%, 0 <y ≦ 10 at.%, 3.5 ≦ z ≦ 23.5 at.%) The magnetic material for magnetic refrigeration according to claim 1 or 2, wherein the magnetic material is used for magnetic refrigeration. A magnetic refrigeration device using a liquid refrigerant,
A heat exchange container filled with magnetic material;
Magnetic field generating means for applying and removing a magnetic field to the magnetic material;
A low temperature side heat exchange section;
A high temperature side heat exchange section;
A refrigerant circuit formed by connecting the heat exchange vessel, the low temperature side heat exchange unit and the high temperature side heat exchange unit to circulate the liquid refrigerant;
The magnetic refrigeration device according to claim 1, wherein at least a part of the magnetic material is the magnetic material for magnetic refrigeration according to claim 1. A magnetic refrigeration device according to claim 4;
A cooling unit thermally connected to the low temperature side heat exchange unit;
An exhaust heat section thermally connected to the high temperature side heat exchange section;
A magnetic refrigeration system comprising: