Rare-earth-based low-temperature magnetic cold storage functional material

Abstract

The invention relates to a rare-earth-based low-temperature magnetic cold storage functional material, the chemical composition of which is (Er50-aMa) (Cu50-x-yGaxNiy), M is heavy rare earth Ho and Tm, a is equal to 0-25, x is equal to 0-10, and y is equal to 0-30. The magnetic cold storage functional material is obtained by taking heavy rare earth elements and alloy elements of copper, gallium and nickel as raw materials through electric arc melting. The specific heat peak of the low-temperature magnetic cold storage functional material appears at 4-20K in a working environment of 1-20K, and the adjustment of the specific heat peak can be realized by adjusting the content of Ni; the material has excellent specific heat performance at low temperature, and the cold storage capacity is improved by about 20-175% compared with that of Pb; meanwhile, the compression strength of the low-temperature magnetic cold storage functional material can reach 900MPa or above, the low-temperature magnetic cold storage functional material has a very good application prospect in the technical field of magnetic cold storage in a 4-20K temperature region, and the preparation process is simple, green, environment-friendly, energy-saving and efficient.

Description

Technical Field

[0001] The invention belongs to the field of functional materials, and in particular relates to a rare earth-based low-temperature magnetic cold storage functional material and a preparation method and application thereof. Background Art

[0002] With the development of modern science and engineering technology, cryogenics has gone through the laboratory technology era and developed into an important branch of natural science. Cryogenic engineering has been widely used in various fields such as energy industry, aerospace, electronic information systems and biomedicine, and its use in many fields is also increasing. Among various cryogenic refrigeration technologies, cold storage gas refrigerators are widely used due to their reliable performance and simple structure. In recent decades, the rapid development of cryogenic electronics, cryogenic physics, cryogenic medicine and cryogenic biology has promoted the application of cryogenic refrigerators to expand to cutting-edge fields such as MRI superconducting magnet cooling systems, SQUID recondensation systems, cooling of small superconducting devices or infrared detection devices, and cryogenic vacuum pumps. These applications have put forward higher requirements on the minimum refrigeration temperature, refrigeration efficiency, structural size and reliability.

[0003] In order to realize the larger-scale application of cold storage gas refrigerators, it is key to further improve their refrigeration efficiency in the working temperature range. In a regenerative refrigerator, the regenerator is an important component for the exchange of heat between cold and hot fluids. Its heat transfer and flow process are realized by the regenerative (cold storage) filler installed in the regenerator, so it has a decisive influence on the refrigeration performance. The heat capacity of the regenerator filler must be much larger than the heat capacity of the working gas to ensure that the efficiency of the low-temperature refrigerator regenerator is higher than 99%. Otherwise, when the heat capacity of the regenerator filler is reduced to close to the heat capacity of the fluid, the regenerator will produce thermal saturation and fail. At lower temperatures (generally below 15K), the specific heat of traditional regenerative materials (such as lead shot, stainless steel wire mesh, etc.) drops sharply, and the efficiency of the regenerator becomes very low, and the refrigeration performance is seriously deteriorated, and it is no longer suitable as a low-temperature cold storage material below this temperature range. And because both domestic and international efforts are strengthening environmental protection, lead as a heavy metal is increasingly restricted in the application of equipment.

[0004] With the rise of the semiconductor industry, the magnetic cold storage materials for the regenerators of low-temperature refrigerators required in the 10-20K semiconductor wafer manufacturing process are relatively scarce. Existing materials cannot meet the application needs at the same time. The specific heat peak of the cold storage materials with suitable prices is relatively low, while the high specific heat storage materials are generally expensive. At the same time, the mechanical properties of traditional magnetic cold storage materials are relatively poor. Therefore, it is necessary to develop new magnetic cold storage materials with high specific heat capacity, good mechanical properties, easy processing and preparation, non-toxicity, and relatively low cost.

[0005] C101168448A discloses a low-temperature and high specific heat magnetic cold storage material, the chemical composition of which is (Er1-x M x ) (In 1- y D y )3, where M is a heavy rare earth element Ho, Dy, Tb or Gd, and D is a main group element Ga, Sn, Sb, Pb or Bi; x = 0 - 0.6, y = 0 - 0.5; this material has a simple cubic Cu3Au cubic structure and is a single phase.

[0006] CN103031501A discloses an erbium-based amorphous composite magnetic refrigeration material, which is mainly composed of erbium and is prepared on the basis of the compositions of Er3Ni and Er3Co, and its composition can be expressed by the formula: (Er 0.75 T 0.25 ) a Al b X c .

[0007] CN105063450A discloses a high-strength, high specific heat multi-phase magnetic refrigeration material, which contains 91 wt.% - 97 wt.% of Er; at least one of Ho, Dy, Gd and Tb with 0 - 1 wt.%, the weight percentage of the transition element Ni in the material is 1 wt.% - 9 wt.%, and at least one of the elements Co, Cu, Mn and Zn with a weight percentage of 0 - 1 wt.%, the oxygen content in the above material is less than or equal to 0.8 wt.%; this material consists of at least two phases or more than two phases. Sampling is carried out according to the ASTM E9 - 09 standard, and a compression test is carried out, and the compression strength is greater than 200 Mpa; in the temperature range from 2K to 10K, the specific heat per unit volume and the heat capacity value are both greater than those of Pb per unit volume; in the temperature range from 10K to 40K, the specific heat per unit volume and the heat capacity value are respectively greater than 83% of those of Pb per unit volume.

[0008] CN118006998A discloses a low-temperature magnetic refrigeration functional material, the composition of which is Er a Cu b Ga c , where 40 < a < 60, 40 < b < 60, 0 < c < 20, the low-temperature magnetic refrigeration functional material has a specific heat peak at 10 - 20K in a 1 - 20K working environment, and the specific heat capacity of the peak functional material is 0.7 - 0.85 J / cm 3 ·K, and this functional material can be prepared into spherical powder for filling a low-temperature refrigerator, and has a good specific heat peak and good strength and toughness. SUMMARY OF THE INVENTION

[0009] The object of the present invention is to overcome the deficiencies of the prior art and provide a rare earth-based environmentally friendly and efficient high specific heat magnetic refrigeration functional material under low-temperature environment.

[0010] A rare earth-based low-temperature magnetic refrigeration functional material, the chemical composition of the functional material is (Er 50-a M a )(Cu 50-x- y Ga x Ni y ), M is one or two of the heavy rare earths Ho and Tm, where a, x, and y are atomic percentages, and 0 < a < 25, 0 < x < 10, 0 ≤ y < 30; the strength and toughness of the alloy can be controlled by adjusting the content of nickel in the functional material; the compressive strength of the low-temperature magnetic refrigeration functional material is greater than 600 MPa; when the low-temperature magnetic refrigeration functional material is in a working environment of 1 - 20 K, the specific heat peak appears at 4 - 20 K.

[0011] More preferably, the element composition of the low-temperature magnetic refrigeration functional material is Er 50-a Ho a Cu 50-x-y Ga x Ni y , where a, x, and y are atomic percentages, and 0 < a < 25, 0 < x < 10, 0 ≤ y < 30; further, a is any value among 1, 2, 5, 8, 10, 12, 15, 18, 20, x can be any value among 0.1, 0.2, 0.3, 0.5, 0.7, 0.8, 1.0, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 7, 8, 9; y is any value among 0, 0.5, 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 25. More preferably, 4 < a < 20, 2 < x < 9, 0 ≤ y < 25; most preferably, 4 < a < 10, 3 < x < 7, 0 ≤ y < 20.

[0012] When the rare earth-based low-temperature magnetic refrigeration functional material is in a working environment of 1 - 20 K, the specific heat peak appears at 4 - 20 K, and the specific heat capacity of the peak functional material is 0.3 - 1.1 J / cm 3 ·K, preferably 0.4 - 1.0 J / cm 3 ·K.

[0013] The rare earth-based low-temperature magnetic refrigeration material contains an ErCu phase, which belongs to the orthorhombic crystal system, the space group is Pm-3m, α = β = γ = 90°, where the elements Ho, Ga, and Ni exist in the form of substitutional solid solution in the ErCu phase, and the volume fraction of the ErCu phase is greater than 95%; there are also ErCu2 phases and pure Er / Ho / Tm in the magnetic refrigeration material.

[0014] The rare earth-based low-temperature magnetic refrigeration material can adjust the specific heat peak by adjusting the Ni content. The higher the Ni content, the lower the temperature at which the peak value of the specific heat peak appears. At the same time, the increase in Ni content can improve the strength and toughness of the alloy.

[0015] More preferably, the compressive strength of rare earth-based low-temperature magnetic refrigeration materials is greater than 900MPa.

[0016] A method for preparing a rare earth-based low-temperature magnetic refrigeration material comprises the following steps:

[0017] (a) preparing raw materials with a purity greater than 99.9% according to the composition ratio;

[0018] (b) Place the raw materials in an electric arc furnace and evacuate the furnace to a pressure less than or equal to 3×10 -3 Pa, clean the furnace 2 to 4 times with an inert gas with a volume purity of 99.99%, and then fill it with inert gas to make the pressure in the container reach 0.5 to 0.61 standard atmospheres. When all the raw materials are completely melted, keep warm for 20 to 30 seconds, and cool naturally to room temperature to obtain a block (Er 50-a M a )(Cu 50-x-y Ga x Ni y );

[0019] (c) Block (Er 50-a M a )(Cu 50-x-y Ga x Ni y ) is turned over, and then heated in an electric arc furnace again until it is completely melted. After heating for 10 to 20 seconds, the heating is stopped and cooled naturally to room temperature. This is repeated 4 times or more to obtain a uniform composition of (Er 50- a M a )(Cu 50-x-y Ga x Ni y ) alloy ingot.

[0020] Preferably, the vacuum degree in step (b) is 1×10 -3 -3×10 -3 Pa; after impurity removal treatment, the oxygen content in the furnace is less than 5ppm, more preferably less than 2ppm; the content of other heteroatoms is less than 100ppm, more preferably less than 20ppm; the smelting conditions in step (c) are 1500-1650℃ for 1-5h, more preferably 1550-1600℃ for 2-3h.

[0021] Application of a new type of rare earth-based low-temperature magnetic cold storage functional material in low-temperature cold storage. The rare earth-based low-temperature magnetic refrigeration material has a specific heat peak at 4-20K under a 1-20K working environment, and the specific heat capacity of the peak functional material can reach 1.1J / cm 3 K, preferably 0.4-1.0 J / cm 3 ·K.

[0022] Beneficial technical effects of the present invention: Compared with the prior art, the rare earth-based low-temperature magnetic refrigeration material disclosed in the present invention has a specific heat peak at 4-20K under a service environment of 1-20K, with a high specific heat peak value and a large peak width, which improves the cold storage capacity in the temperature range of 4-20K and the refrigeration efficiency compared with the currently widely used Pb; at the same time, this functional material does not contain Pb, which greatly improves the environmental performance of the material. The new low-temperature magnetic cold storage functional material can be used as a substitute for lead in low-temperature refrigerators. Its volume heat capacity in the range of 1-20K is 20-175% greater than that of lead, and its magnetism, ductility, and oxidation resistance are more than 10 times stronger than those of lead. The compression strength reaches 600MPa; further, the compression strength reaches more than 750MPa; most preferably, the compression strength reaches more than 900MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the XRD diffraction pattern of Example 2-5;

[0024] Figure 2 The room temperature compression engineering stress-strain curves of Comparative Examples 1 and 2 and Examples 1 and 5;

[0025] Figure 3 The low-temperature specific heat data of Comparative Example 1, Examples 1-6 and commercial cold storage material Pb. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with comparative examples and embodiments.

[0027] Example 1

[0028] The composition of rare earth-based low-temperature magnetic refrigeration materials is: Er 45 H5 45 Ga5.

[0029] The preparation method of the functional material comprises the following steps:

[0030] (a) Prepare the raw materials with a purity greater than 99.9% according to the composition ratio;

[0031] (b) During smelting, high vacuum is first drawn, and then Ti is used to absorb oxygen and other impurities in the furnace;

[0032] (c) The raw materials are then smelted in an electric arc furnace to obtain an alloy ingot, and the arc melting is performed 3-5 times to make it uniform.

[0033] Tested at room temperature Er 45 H5 45 Mechanical properties of Ga5 alloy powder, such as Figure 2 shown.

[0034] Using the PPMS comprehensive physical property measurement platform, Er was measured at a temperature interval of 0.5K. 45 H5 45 The volume specific heat of Ga5 alloy in the 2K-30K temperature range varies with temperature, such as Figure 3 shown.

[0035] Example 2

[0036] The composition of rare earth-based low-temperature magnetic refrigeration materials is: Er 45 H5 40 Ga5Ni5.

[0037] The preparation method of the functional material comprises the following steps:

[0038] (a) Prepare the raw materials with a purity greater than 99.9% according to the composition ratio;

[0039] (b) During smelting, high vacuum is first drawn, and then Ti is used to absorb oxygen and other impurities in the furnace;

[0040] (c) The raw materials are then smelted in an electric arc furnace to obtain an alloy ingot, and the arc melting is performed 3-5 times to make it uniform.

[0041] Using Smartlab X-ray Diffractometer Measured Er 45 H5 40 The XRD diffraction peaks of Ga5Ni5 alloy are as follows: Figure 1 shown.

[0042] Tested at room temperature Er 45 H5 40 Mechanical properties of Ga5Ni5 alloy powder, such as Figure 2 shown.

[0043] Using the PPMS comprehensive physical property measurement platform, Er was measured at a temperature interval of 0.5K. 45 H5 40 The volume specific heat of Ga5Ni5 alloy in the 2K-20K temperature range varies with temperature, such as Figure 3 shown.

[0044] Example 3

[0045] The composition of rare earth-based low-temperature magnetic refrigeration materials is: Er 45 H5 35 Ga5 10 .

[0046] The preparation method of the functional material comprises the following steps:

[0047] (a) Prepare the raw materials with a purity greater than 99.9% according to the composition ratio;

[0048] (b) During smelting, high vacuum is first drawn, and then Ti is used to absorb oxygen and other impurities in the furnace;

[0049] (c) The raw materials are then smelted in an electric arc furnace to obtain an alloy ingot, and the arc melting is performed 3-5 times to make it uniform.

[0050] Using Smartlab X-ray Diffractometer Measured Er 45 H5 35 Ga5 10 The XRD diffraction peaks of the alloy are as follows: Figure 1 shown.

[0051] Tested at room temperature Er 45 H5 35 Ga5 10 Mechanical properties of alloy powders, such as Figure 2 shown.

[0052] Using the PPMS comprehensive physical property measurement platform, Er was measured at a temperature interval of 0.5K. 45 H5 35 Ga5 10 The curve of volume specific heat of alloy in 2K-30K temperature range with temperature is as follows: Figure 3 shown.

[0053] Example 4

[0054] The composition of rare earth-based low-temperature magnetic refrigeration materials is: Er 45 H5 30 Ga5 15 .

[0055] The preparation method of the functional material comprises the following steps:

[0056] (a) Prepare the raw materials with a purity greater than 99.9% according to the composition ratio;

[0057] (b) During smelting, high vacuum is first drawn, and then Ti is used to absorb oxygen and other impurities in the furnace;

[0058] (c) The raw materials are then smelted in an electric arc furnace to obtain an alloy ingot, and the arc melting is performed 3-5 times to make it uniform.

[0059] Tested at room temperature Er 45 H5 30 Ga5 15 Mechanical properties of alloy powders, such as Figure 2 shown.

[0060] Using Smartlab X-ray Diffractometer Measured Er 45 H5 30 Ga5 15 The XRD diffraction peaks of the alloy are as follows: Figure 1 shown.

[0061] Example 5

[0062] The composition of rare earth-based low-temperature magnetic refrigeration materials is: Er 45 H5 25 Ga5 20 .

[0063] The preparation method of the functional material comprises the following steps:

[0064] (a) Prepare the raw materials with a purity greater than 99.9% according to the composition ratio;

[0065] (b) During smelting, high vacuum is first drawn, and then Ti is used to absorb oxygen and other impurities in the furnace;

[0066] (c) The raw materials are then smelted in an electric arc furnace to obtain an alloy ingot, and the arc melting is performed 3-5 times to make it uniform.

[0067] Using Smartlab X-ray Diffractometer Measured Er 45 H5 25 Ga5 20 The XRD diffraction peaks of the alloy are as follows: Figure 1 shown.

[0068] Tested at room temperature Er 45 H5 25 Ga5 20 Mechanical properties of alloy powders, such as Figure 2 shown.

[0069] Using the PPMS comprehensive physical property measurement platform, Er was measured at a temperature interval of 0.5K. 45 H5 25 Ga5 20 The curve of volume specific heat of alloy in 2K-30K temperature range with temperature is as follows: Figure 3 shown.

[0070] Example 6

[0071] The composition of rare earth-based low-temperature magnetic refrigeration materials is: Er 45 Tm5Cu 45 Ga5.

[0072] The preparation method of the functional material comprises the following steps:

[0073] (a) Prepare the raw materials with a purity greater than 99.9% according to the composition ratio;

[0074] (b) During smelting, high vacuum is first drawn, and then Ti is used to absorb oxygen and other impurities in the furnace;

[0075] (c) The raw materials are then smelted in an electric arc furnace to obtain an alloy ingot, and the arc melting is performed 3-5 times to make it uniform.

[0076] Using the PPMS comprehensive physical property measurement platform, Er was measured at a temperature interval of 0.5K. 45 Tm5Cu 45 The volume specific heat of Ga5 alloy in the 2K-30K temperature range varies with temperature, such as Figure 3 shown.

[0077] Comparative Example 1

[0078] Er was prepared by electric arc furnace 50 Cu 45 Ga5 alloy, tested at room temperature Er 50 Cu 45 Mechanical properties of Ga5 alloy powder, such as Figure 2 As shown. Using the PPMS comprehensive physical property measurement platform, Er was measured at a temperature interval of 0.5K. 50 Cu 45 The volume specific heat of Ga5 alloy in the 2K-20K temperature range varies with temperature, such as Figure 3 As shown. 50 Cu 45 The specific heat peak of Ga5 alloy appears at 12K, reaching 0.7J / cm 3 ·K or above, compression strength 759MPa, compression rate 7.4%.

[0079] Comparative Example 2

[0080] Er was prepared by electric arc furnace 25 Ho 25 Cu 40 Ga5Ni5 alloy, tested at room temperature Er 25 Ho 25 Cu 40Mechanical properties of Ga5Ni5 alloy powder, such as Figure 2 As shown in the figure, the compression strength is only 591MPa and the compression rate is 9.3%. When the Ho and Tm contents are ≥25, the mechanical properties are not ideal.

[0081] Compared with the comparative example, the embodiments of the present invention add heavy rare earth and nickel elements, which can achieve a lower specific heat peak temperature (Examples 3 and 5), and at the same time, the specific heat peak can be increased to 0.8 J / cm above 12K. 3 ·K or above (Examples 1 and 6), the temperature range near 12K is wider than the thermal peak (Example 2); the addition of heavy rare earth and nickel elements also improves the strength and toughness of the alloy (Example 6).

[0082] The above contents are merely examples and explanations of the concept of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the present invention, they shall all fall within the protection scope of the present invention.

Claims

1. A rare earth-based low-temperature magnetic cold storage functional material, characterized in that The chemical composition of the functional material is (Er 50-a M a )(Cu 50-x-y Ga x Ni y ), where M is a heavy rare earth Ho or Tm, a, x, and y are atomic percentages, and 0 < a < 25, 0 < x < 10, 0 ≤ y < 30; the strength and toughness of the alloy can be controlled by adjusting the nickel content; the compressive strength of the alloy is greater than 600 MPa; for the low-temperature magnetic refrigeration functional material, the specific heat peak appears at 4 - 20 K in a working environment of 1 - 20 K.

2. The rare earth-based low-temperature magnetic cold storage functional material according to claim 1, characterized in that: 4 of them <a<20,2<x<9,0≤y<25。 3. The rare earth-based low-temperature magnetic cold storage functional material according to claim 1, characterized in that: The low-temperature magnetic cold storage functional material has a specific heat peak at 4-20K under a 1-20K working environment, and the specific heat capacity of the peak functional material is 0.3-1.1 J / cm 3 K, preferably 0.4-1.0 J / cm 3 ·K.

4. The rare earth-based low-temperature magnetic cold storage functional material according to claim 1, characterized in that: The magnetic refrigeration material contains ErCu phase, belongs to the orthorhombic crystal system, the space group is Pm-3m, α=β=γ=90°, wherein Ho, Ga, and Ni elements exist in the ErCu phase in the form of substitutional solid solution, and the volume fraction of the ErCu phase is greater than 95%. The magnetic refrigeration material also contains ErCu2 phase and pure Er / Ho / Tm.

5. The rare earth-based low-temperature magnetic cold storage functional material according to claim 1, characterized in that: The specific heat peak can be adjusted by adjusting the Ni content. The higher the Ni content, the lower the temperature at which the peak value of the specific heat peak appears. At the same time, the increase in Ni content can improve the strength and toughness of the alloy.

6. The low-temperature magnetic cold storage functional material according to claim 1, characterized in that: Its volume heat capacity in the range of 1-20K is 20-175% greater than that of lead, and its magnetism, ductility and oxidation resistance are more than 10 times stronger than those of lead.

7. A method for preparing a rare earth-based low-temperature magnetic cold storage functional material according to any one of claims 1 to 6, characterized in that The steps include: (a) preparing raw materials with a purity greater than 99.9% according to the composition ratio; (b) Place the raw materials in an electric arc furnace and evacuate the furnace to a pressure less than or equal to 3×10 -3 Pa, clean the furnace 2 to 4 times with an inert gas with a volume purity of 99.99%, and then fill it with inert gas to make the pressure in the container reach 0.5 to 0.61 standard atmospheres. When all the raw materials are completely melted, keep warm for 20 to 30 seconds, and cool naturally to room temperature to obtain a block (Er 50-a M a )(Cu 50-x-y Ga x Ni y ); (c) Block (Er 50-a M a )(Cu 50-x-y Ga x Ni y ) is turned over, and then heated in an electric arc furnace again until it is completely melted. After heating for 10 to 20 seconds, the heating is stopped and cooled naturally to room temperature. This is repeated 4 times or more to obtain a uniform composition of (Er 50-a M a )(Cu 50-x-y Ga x Ni y ) alloy ingot.

8. The method according to claim 7, characterized in that: The vacuum degree in step (b) is 1×10 -3 -3×10 -3 Pa; after cleaning the furnace, the oxygen content in the furnace is less than 5ppm; the content of other heteroatoms is less than 100ppm; the smelting conditions in step (c) are 1500-1650℃ for 1-5h.

9. The method according to claim 7, characterized in that: After cleaning the furnace in step (b), the oxygen content in the furnace is less than 2 ppm; the content of other heteroatoms is less than 20 ppm; and the smelting conditions in step (c) are 1550-1600° C. for 2-3 hours.

10. Use of the rare earth-based low-temperature magnetic cold storage functional material according to any one of claims 1 to 6 or the rare earth-based low-temperature magnetic cold storage functional material prepared by the method according to any one of claims 7 to 9 in low-temperature cold storage.

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