Gd-Al-based room-temperature magnetic refrigeration material, preparation method and application method

Abstract

The chemical formula of the Gd-Al-based room-temperature magnetic refrigeration material is Gd < 3-x > LaxAl < 2 >, and x is greater than or equal to 0 and less than or equal to 0.3. The invention discloses a preparation method and an application method of a Gd-Al-based room-temperature magnetic refrigeration material. According to the room-temperature magnetic refrigeration material and the preparation method thereof, the substitution atom-La atom is introduced into the Gd3Al2 alloy, the proportion of the content of Gd and La elements in the room-temperature magnetic refrigeration material is adjusted, the magnetic phase transition temperature is continuously adjustable within the temperature range of 252-275 K, and the refrigeration temperature range is greatly widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of room temperature magnetic refrigeration, and in particular relates to a Gd-Al based room temperature magnetic refrigeration material, a preparation method and an application method. Background Art

[0002] Refrigeration technology plays a vital role in modern life in the fields of healthcare, food industry, aviation industry, etc. At present, one-fifth of the world's electricity is used for refrigeration, and refrigeration consumes 2000TWh of electricity, which is 2.5 times the electricity consumption in Africa. Among them, a key problem is that the mainstream refrigeration technology is gas compression refrigeration. After more than 150 years of development, the energy efficiency of gas compression refrigeration has almost reached its limit, which is only 5%-10% of the Carnot cycle. In addition, gas compression refrigeration often uses hydrofluorocarbons as refrigerants, and its global warming potential is thousands of times that of carbon dioxide.

[0003] Compared with gas compression refrigeration, magnetic refrigeration technology has the advantages of high energy efficiency, environmental friendliness and reliable operation, and has important research significance. In the past forty years, the research on magnetic refrigeration technology has mainly focused on the research and development of magnetic refrigeration materials, the design of magnetic field systems and the development of refrigeration systems.

[0004] Pure metal Gd cannot play a cooling role at low temperatures. In 1999, Pecharsky et al. first discovered the magnetocaloric effect of Gd3Al2 alloy. Since then, related research has mainly focused on the preparation of Gd3Al2 single-phase alloys and the effects of different substitution atoms on magnetocaloric properties. In order to obtain single-phase Gd3Al2, cast Gd3Al2 alloys usually need to be annealed for a long time at a high temperature above 900°C, which increases the preparation time and cost. However, the magnetic phase transition temperature of single-phase Gd3Al2 cannot be continuously adjusted, and the cooling range is narrow. Summary of the invention

[0005] The purpose of the present invention is to provide a Gd-Al based room temperature magnetic refrigeration material, a preparation method and an application method. By introducing a substitute atom - La atom into the Gd3Al2 alloy, the ratio of the Gd and La element contents in the room temperature magnetic refrigeration material is adjusted, the magnetic phase transition temperature can be continuously adjusted in the temperature range of 252 to 275K, and the refrigeration temperature range is greatly improved.

[0006] To achieve the above objectives, the technical solutions used in the present invention are:

[0007] Gd-Al based room temperature magnetic refrigeration material, the chemical formula is Gd 3-x La x Al2, the range of x is: 0≤x≤0.3.

[0008] Furthermore, the Curie temperature T CThe Curie temperature T is 252-275K, which can be achieved by adjusting the content of La in the alloy. C continuous change.

[0009] Furthermore, the maximum isothermal magnetic entropy change in the magnetic field range of 0-2T is 3.05J / kg K.

[0010] Furthermore, the magnetic phase transition temperature is between 252 and 275K.

[0011] The preparation method of Gd-Al based room temperature magnetic refrigeration material comprises:

[0012] Use metal Gd, La, Al with purity greater than 99wt.% as raw materials, according to Gd 3-x La x Al2 alloy components are prepared, wherein 0≤x≤0.3;

[0013] The prepared raw materials are placed in the crucible of the high-frequency induction melting furnace, and the vacuum is evacuated to make the vacuum degree in the high-frequency induction melting furnace reach 1.0×10 -2 Pa or less; use argon with a purity greater than 99% to perform gas washing operation on the high-frequency induction melting furnace, and the number of gas washing operations shall be more than 3 times;

[0014] The high-frequency induction melting furnace is filled with argon gas with a purity greater than 99%, so that the atmospheric pressure in the furnace chamber of the high-frequency induction melting furnace is 0.3-0.6 standard atmospheric pressure;

[0015] The high-frequency induction melting furnace completely melts the raw materials to form a (Gd, La)3Al2 alloy at a melting temperature of 1700K to 1800K.

[0016] Preferably, the metals Gd, La, and Al are 99.9wt.%, 99.99wt.%, and 99.99wt.%, respectively. The prepared raw materials are placed in a crucible of a high-frequency induction melting furnace, and the furnace is evacuated using a mechanical pump and a molecular pump. When the vacuum degree reaches 1.0×10 -2 When the pressure is below Pa, high-purity argon gas with a purity of 99.996% is used for gas purge operation.

[0017] Preferably, after smelting, a cast alloy ingot is obtained in a water-cooled copper crucible.

[0018] Preferably, the alloy ingot is smelted forward and backward 3-5 times to ensure the uniformity of the alloy ingot composition.

[0019] Preferably, the method further includes a step of detecting the GdLaAl alloy.

[0020] The application method of Gd-Al based room temperature magnetic refrigeration material is used for magnetic refrigerator.

[0021] The technical effects of the present invention include:

[0022] 1. The Gd-Al-based room temperature magnetic refrigeration material prepared by the present invention, namely Gd 3-x La x Al2 alloy, Curie temperature T C Continuously adjustable, the refrigeration temperature range is greatly improved.

[0023] By introducing La atoms as substitute atoms into Gd3Al2 alloy, the magnetic phase transition temperature can be continuously adjusted in the temperature range of 252-275K. Compared with pure metal Gd, rare earth-based magnetic refrigeration materials show higher magnetocaloric effect under low temperature conditions and are suitable for refrigeration in the temperature range of 252-275K or a wider temperature range. M The half-width of the -T curve exceeds 35K, which has the characteristics of a wide operating temperature range.

[0024] 2. The hysteresis of magnetic refrigeration materials in an alternating magnetic field is close to 0, and almost no hysteresis loss is generated in a magnetic refrigerator. The thermal hysteresis of magnetic refrigeration materials in the process of heating and cooling is close to 0, and no thermal hysteresis loss is generated in a magnetic refrigerator.

[0025] 3. The Gd-Al-based room temperature magnetic refrigeration material provided by the present invention reduces material costs and has a green and environmentally friendly preparation process.

[0026] Compared with pure metallic gadolinium Gd, the addition of the alternative La element makes the raw material price cheaper.

[0027] Compared with the preparation of single-phase Gd3Al2 alloy, there is no heat treatment process, the preparation process is simple, and the preparation time is shortened.

[0028] 4. Gd provided by the present invention 3-x La x Al2 room temperature magnetic refrigeration material can be used as a secondary refrigeration material for metal Gd.

[0029] The primary refrigerant uses metal Gd to reduce the temperature of the heat exchange fluid to about 280K, and the secondary refrigerant uses Gd 3-x La x Al2 alloy further reduces the temperature of the heat exchange fluid, and uses the low-temperature heat exchange fluid to take away the heat of the space that needs to be refrigerated, thereby achieving refrigeration. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Gd prepared in this embodiment of the present invention 3-x La x XRD patterns of Al2 alloy (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration materials;

[0031] Figure 2a Gd prepared in this embodiment of the present invention3-x La x SEM images of Al2 alloy (x=0) room temperature magnetic refrigeration materials;

[0032] Figure 2b Gd prepared in this embodiment of the present invention 3-x La x SEM images of Al2 alloy (x=0.1) room temperature magnetic refrigeration materials;

[0033] Figure 2c Gd prepared in this embodiment of the present invention 3-x La x SEM images of Al2 alloy (x=0.2) room temperature magnetic refrigeration materials;

[0034] Figure 2d Gd prepared in this embodiment of the present invention 3-x La x SEM images of Al2 alloy (x=0.3) room temperature magnetic refrigeration materials;

[0035] Figure 3 Gd prepared in this embodiment of the present invention 3-x La x The relationship between the magnetization intensity M and the temperature T of Al2 alloy (x = 0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration material under 0.05T magnetic field;

[0036] Figure 4 Gd prepared in this embodiment of the present invention 3-x La x Curie temperature T of Al2 alloy (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration material C Relationship curve with La content x;

[0037] Figure 5a Gd prepared in this embodiment of the present invention 3-x La x The relationship between the magnetization intensity M and the external magnetic field intensity H of Al2 alloy (x=0) room temperature magnetic refrigeration material during the magnetization process at different temperatures;

[0038] Figure 5b Gd prepared in this embodiment of the present invention 3-x La x The relationship between the magnetization intensity M and the external magnetic field intensity H of Al2 alloy (x=0.1) room temperature magnetic refrigeration material during the magnetization process at different temperatures;

[0039] Figure 5c Gd prepared in this embodiment of the present invention 3-x La xThe relationship between the magnetization intensity M and the external magnetic field intensity H of Al2 alloy (x = 0.2) room temperature magnetic refrigeration material during the magnetization process at different temperatures;

[0040] Figure 5d Gd prepared in this embodiment of the present invention 3-x La x The relationship between the magnetization intensity M and the external magnetic field intensity H of Al2 alloy (x = 0.3) room temperature magnetic refrigeration material during the magnetization process at different temperatures;

[0041] Figure 6 Gd prepared in this embodiment of the present invention 3-x La x Isothermal magnetic entropy change ΔS of Al2 alloy (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration material under 0-2.0T magnetic field M The relationship curve between the temperature T and the

[0042] Figure 7 Gd prepared in this embodiment of the present invention 3-x La x Adiabatic temperature change ΔT of Al2 alloy (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration materials in 0-1.5T magnetic field ad The relationship curve between the temperature T and the

[0043] Figure 8 Gd prepared in this embodiment of the present invention 3-x La x Adiabatic temperature change ΔT of Al2 alloy (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration material under 0-2.0T magnetic field ad The relationship curve between and temperature T. DETAILED DESCRIPTION

[0044] The following description sufficiently illustrates specific embodiments of the invention to enable those skilled in the art to practice and reproduce the invention.

[0045] The preparation method of Gd-Al based room temperature magnetic refrigeration material, the specific steps are as follows:

[0046] Step 1: Use pure metal Gd, La, and Al as raw materials, according to Gd 3-x La x Al2 alloy components are prepared, wherein 0≤x≤0.3;

[0047] The purity of the raw materials gadolinium Gd, lanthanum La and aluminum Al is greater than 99wt.%, and in this embodiment, they are 99.9wt.%, 99.99wt.% and 99.99wt.% respectively.

[0048] Step 2: Put the prepared raw materials into the crucible of the high-frequency induction melting furnace, and evacuate the high-frequency induction melting furnace to a vacuum degree of 1.0×10 -2 Pa or less; use high-purity argon (purity greater than 99%) to wash the high-frequency induction melting furnace, and the number of washing operations is more than 3 times;

[0049] The prepared raw materials were placed in the crucible of the high-frequency induction melting furnace, and the furnace was evacuated using a mechanical pump and a molecular pump. When the vacuum reached 1.0×10 -2 When the pressure is below Pa, use 99.996% high-purity argon gas for three gas washing operations;

[0050] Step 3: High-purity argon gas (purity greater than 99%) is filled into the high-frequency induction melting furnace to make the atmospheric pressure in the furnace chamber of the high-frequency induction melting furnace 0.3-0.6 standard atmospheric pressure;

[0051] Fill the furnace chamber of the high-frequency induction melting furnace with high-purity argon gas of 99.996% purity to make the atmospheric pressure of the furnace chamber 0.5×10 5 Pa.

[0052] Step 4: The high-frequency induction melting furnace completely melts the raw materials to form a (Gd, La)3Al2 alloy at a melting temperature of 1700K to 1800K.

[0053] (Gd, La)3Al2 alloy is used as Gd-Al based room temperature magnetic refrigeration material, the chemical formula is Gd 3-x La x The range of Al2x is: 0≤x≤0.3.

[0054] Turn on the smelting power switch of the high-frequency induction melting furnace, gradually increase the power supply current of the smelting alloy, so that the raw materials Gd, Er, and Al are completely melted to form Gd 3-x La x Al2 alloy, where 0≤x≤0.3.

[0055] After smelting, a cast alloy ingot is obtained in a water-cooled copper crucible; the alloy ingot is smelted forward and backward 3-5 times to ensure the uniformity of the alloy ingot composition.

[0056] Step 5: Detection of GdLaAl alloy.

[0057] 1. From Gd 3-x La x Small pieces were cut from Al2 (x=0, 0.1, 0.2, 0.3) alloy and ground into powder samples with a particle size less than 300 mesh.

[0058] Philips PW1700 X-ray diffractometer (XRD) was used to measure Gd 3-x Lax Phase composition of Al2 (x=0, 0.1, 0.2, 0.3) powder samples, test voltage 40 kW, tube current 40 mA, Cu target, scanning angle range 20°-70°, scanning speed 2° / min.

[0059] like Figure 1 As shown, the Gd prepared by the embodiment of the present invention 3-x La x XRD patterns of Al2 (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration materials.

[0060] XRD test results, Gd 3-x La x Al2 alloy (x=0, 0.1, 0.2, 0.3) is used as a magnetic refrigeration material, which is composed of three phases: Gd3Al2, GdAl and Gd2Al. The mass percentage of each phase is shown in Table 1.

[0061] Table 1

[0062]

[0063] 2. From Gd 3-x La x Small blocks were cut from Al2 alloy (x=0, 0.1, 0.2, 0.3) ingots, mounted and polished, and the microstructure of the alloy was analyzed using a Sigma 500 scanning electron microscope (SEM).

[0064] like Figure 2a As shown, the Gd prepared by the embodiment of the present invention 3-x La x SEM spectrum of Al2 alloy (x=0) room temperature magnetic refrigeration material; Figure 2b As shown, the Gd prepared by the embodiment of the present invention 3-x La x SEM spectrum of Al2 alloy (x = 0.1) room temperature magnetic refrigeration material; Figure 2c As shown, the Gd prepared by the embodiment of the present invention 3-x La x SEM spectrum of Al2 alloy (x = 0.2) room temperature magnetic refrigeration material; Figure 2d As shown, the Gd prepared by the embodiment of the present invention 3-x La x SEM spectrum of Al2 alloy (x=0.3) room temperature magnetic refrigeration material.

[0065] H represents heating, and C represents cooling.

[0066] The energy dispersive spectrometer (EDS) on a scanning electron microscope was used to test the distribution of different elements. The test results are shown in Table 2.

[0067] Table 2

[0068]

[0069]

[0070] 3. From Gd 3-x La x Small blocks were cut from Al2 alloy (x=0, 0.1, 0.2, 0.3) alloys, and the heating MT curve and cooling MT curve of the alloy block under a 0.05T magnetic field were measured using a multifunctional (magneto-electro-thermal) vibrating sample magnetometer (Versalab).

[0071] like Figure 3 As shown, the Gd prepared by the embodiment of the present invention 3-x La x The relationship curve between the magnetization intensity M and temperature T of Al2 alloy (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration material during heating and cooling under a 0.05T magnetic field.

[0072] The test results show that Gd 3-x La x The heating MT curve and cooling MT curve of Al2 alloy (x = 0, 0.1, 0.2, 0.3) are basically coincident, indicating that Gd 3-x La x The thermal hysteresis of Al2 (x=0, 0.1, 0.2, 0.3) alloy is close to 0, and the thermal hysteresis loss caused is 0.

[0073] 4. Obtain the Curie temperature T by taking the first-order derivative of the temperature-increasing MT curve C , T C and La content x.

[0074] like Figure 4 As shown, the Gd prepared by the embodiment of the present invention 3-x La x Curie temperature T of Al2 alloy (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration material C and La content x.

[0075] analyze Figure 4 It can be seen that Gd 3-x La x Curie temperature T of Al2 (x = 0, 0.1, 0.2, 0.3) alloy CWith the increase of La content, the Curie temperature gradually decreases, and the range of Curie temperature is 252K-275K.

[0076] 5. From Gd 3-x La x Small blocks were cut from Al2 alloy (x=0, 0.1, 0.2, 0.3), and the magnetization MH data of the alloy blocks were measured using a multifunctional (magneto-electro-thermal) vibrating sample magnetometer (Versalab), and a relationship curve was drawn.

[0077] like Figure 5a As shown, the Gd prepared by the embodiment of the present invention 3-x La x The relationship between the magnetization intensity M and the external magnetic field intensity H of Al2 alloy (x=0) room temperature magnetic refrigeration material during the magnetization process at different temperatures. Figure 5b As shown, the Gd prepared by the embodiment of the present invention 3-x La x The relationship between the magnetization intensity M and the external magnetic field intensity H of Al2 alloy (x = 0.1) room temperature magnetic refrigeration material during the magnetization process at different temperatures. Figure 5c As shown, the Gd prepared by the embodiment of the present invention 3-x La x The relationship between the magnetization intensity M and the external magnetic field intensity H of Al2 alloy (x = 0.2) room temperature magnetic refrigeration material during the magnetization process at different temperatures. Figure 5d As shown, the Gd prepared by the embodiment of the present invention 3-x La x The relationship curve between the magnetization intensity M and the external magnetic field intensity H of Al2 alloy (x=0.3) room temperature magnetic refrigeration material during the magnetic rising process at different temperatures.

[0078] 5. Gd 3-x La x Maximum isothermal magnetic entropy change of Al2 alloys (x=0, 0.1, 0.2, 0.3).

[0079] The magnetization MH data were obtained using Maxwell's equations

[0080]

[0081] Calculate Gd 3-x La x Al2 alloy (x=0, 0.1, 0.2, 0.3) at 0-2.0T().

[0082] like Figure 6 As shown, the Gd prepared by the embodiment of the present invention 3-x La xIsothermal magnetic entropy change ΔS of Al2 (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration material under 0-2.0T magnetic field M The relationship curve between and temperature T.

[0083] Figure 6 It shows that Gd3Al2, Gd 2.9 La 0.1 Al2、Gd 2.8 La 0.2 Al2 and Gd 2.7 La 0.3 The Al2 alloy achieved the maximum isothermal magnetic entropy change at 276K, 269K, 259K and 250K under 0-2.0T magnetic field. The maximum isothermal magnetic entropy change (ΔS M ) max The values ​​are 3.05 J / (kg·K), 2.99 J / (kg·K), 2.62 J / (kg·K) and 2.42 J / (kg·K) respectively.

[0084] Compared with metallic Gd, Gd 3-x La x Al2 alloy (x=0, 0.1, 0.2, 0.3) has a low Curie temperature and is suitable for refrigeration fields in the temperature range of 252 to 275K or a wider temperature range.

[0085] 6. From Gd 3-x La x Small blocks were cut from Al2 alloy (x = 0, 0.1, 0.2, 0.3), and the adiabatic temperature change ΔT of the alloy block was measured under 0-1.5T and 0-2.0T magnetic fields using an adiabatic temperature change direct measuring instrument. ad The relationship between and temperature T.

[0086] like Figure 7 As shown, the Gd prepared by the embodiment of the present invention 3-x La x Adiabatic temperature change ΔT of Al2 alloy (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration materials in 0-1.5T magnetic field ad and the relationship curve between temperature T; such as Figure 8 As shown, the Gd prepared by the embodiment of the present invention 3-x La x Adiabatic temperature change ΔT of Al2 alloy (x=0, 0.1, 0.2, 0.3) room temperature magnetic refrigeration material under 0-2.0T magnetic field ad The relationship curve between and temperature T.

[0087] G 3-x La xAl2 alloy (x = 0, 0.1, 0.2, 0.3) at 278K, 267K, 261K, 248K

[0088] Adiabatic temperature change ΔT ad Get the maximum value, close to the respective Curie temperature T C .Gd 3-x La x Adiabatic temperature change ΔT of Al2 alloy (x=0,0.1,0.2,0.3) ad The adiabatic temperature change ΔT of Gd3Al2 alloy at 0-1.5T and 0-2T shows a gradual decrease with the increase of La content. ad are higher, at 1.67K and 2.12K respectively.

[0089] The terms used in the present invention are illustrative and exemplary, rather than restrictive. Since the present invention can be implemented in various forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the aforementioned details, but should be widely interpreted within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A Gd-Al based room temperature magnetic refrigeration material, characterized in that: The chemical formula is Gd 3-x La x Al2, the range of x is: 0≤x≤0.

3.

2. The Gd-Al based room temperature magnetic refrigeration material according to claim 1, characterized in that: Curie temperature T of the material C The Curie temperature T is 252-275K, which can be achieved by adjusting the content of La in the alloy. C continuous change.

3. The Gd-Al based room temperature magnetic refrigeration material according to claim 1, characterized in that: The maximum isothermal magnetic entropy change in the magnetic field range of 0-2T is 3.05J / kg K.

4. The Gd-Al based room temperature magnetic refrigeration material according to claim 1, characterized in that: The magnetic phase transition temperature is between 252 and 275K.

5. The method for preparing the Gd-Al based room temperature magnetic refrigeration material according to any one of claims 1 to 4, characterized in that: include: Use metal Gd, La, Al with purity greater than 99wt.% as raw materials, according to Gd 3-x La x Al2 alloy components are prepared, wherein 0≤x≤0.3; The prepared raw materials are placed in the crucible of the high-frequency induction melting furnace, and the vacuum is evacuated to make the vacuum degree in the high-frequency induction melting furnace reach 1.0×10 -2 Pa or less; use argon with a purity greater than 99% to perform gas washing operation on the high-frequency induction melting furnace, and the number of gas washing operations shall be more than 3 times; The high-frequency induction melting furnace is filled with argon gas with a purity greater than 99%, so that the atmospheric pressure in the furnace chamber of the high-frequency induction melting furnace is 0.3-0.6 standard atmospheric pressure; The high-frequency induction melting furnace completely melts the raw materials to form a (Gd, La)3Al2 alloy at a melting temperature of 1700K to 1800K.

6. The method for preparing the Gd-Al based room temperature magnetic refrigeration material according to claim 5, characterized in that: The metal Gd, La, and Al are 99.9wt.%, 99.99wt.%, and 99.99wt.%, respectively. The prepared raw materials are placed in a crucible of a high-frequency induction melting furnace, and the furnace is evacuated using a mechanical pump and a molecular pump. When the vacuum degree reaches 1.0×10 -2 When the pressure is below Pa, high-purity argon gas with a purity of 99.996% is used for gas purge operation.

7. The method for preparing the Gd-Al based room temperature magnetic refrigeration material according to claim 5, characterized in that: After smelting, a cast alloy ingot is obtained in a water-cooled copper crucible.

8. The method for preparing the Gd-Al based room temperature magnetic refrigeration material according to claim 7, characterized in that: The alloy ingot is smelted forward and backward 3-5 times to ensure the uniformity of the alloy ingot composition.

9. The method for preparing the Gd-Al based room temperature magnetic refrigeration material according to claim 7, characterized in that: The method also includes a step of detecting the GdLaAl alloy.

10. The application method of the Gd-Al based room temperature magnetic refrigeration material according to any one of claims 1 to 4, characterized in that: Used in magnetic refrigerators.

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