Rare earth cobalt boron carbon magnetic refrigeration material and preparation method and application thereof

Abstract

The application discloses a rare earth cobalt boron carbon magnetic refrigeration material and a preparation method and application thereof, and belongs to the technical field of rare earth magnetic refrigeration materials. The molecular formula of the magnetic refrigeration material is RECoBC, and RE is one or a mixture of several of rare earth elements Gd, Tb, Dy, Ho, Er and Tm. The preparation method of the rare earth cobalt boron carbon magnetic refrigeration material comprises the following steps: batching, vacuum protection gas smelting, repeated smelting for 3-5 times and heat treatment. The maximum isothermal magnetic entropy change of the magnetic refrigeration material is 11.7 J / kgK-18.1 J / kgK under the magnetic field change of 0-5T, and the maximum isothermal magnetic entropy change is 15.2 J / kgK-21.9 J / kgK under the magnetic field change of 0T-7T. The above-mentioned rare earth cobalt boron carbon magnetic refrigeration material, the preparation method and the application thereof can solve the problem of low magnetic entropy change of the existing magnetic refrigeration material.

Description

Technical Field

[0001] This invention relates to the field of magnetic refrigeration materials technology, and in particular to a rare earth cobalt boron carbon magnetic refrigeration material and its preparation method. Background Technology

[0002] In recent years, with the rapid development of human economy, the damage to the environment has been increasing, so various green and environmentally friendly clean technologies have gradually become popular. Compared with traditional vapor compression refrigeration, magnetic refrigeration technology has the following significant advantages: (1) Green and environmentally friendly: Magnetic refrigeration uses solid or liquid refrigerant, which will not cause damage to the ozone layer or bring about the greenhouse effect; (2) Energy-saving and efficient: The thermodynamic process of magnetic refrigeration generating magnetocaloric effect is highly reversible and can reach 60% to 70% of the Carnot cycle efficiency; (3) Stable and reliable: The realization of magnetic refrigeration technology does not require a gas compressor, will not generate vibration and noise, and has a long equipment life and high reliability. Magnetic refrigeration technology based on magnetocaloric effect (MCE) is the most promising technology to replace traditional gas compression refrigeration in the future. The so-called magnetocaloric effect refers to the change in the order of magnetic moments inside the magnetic material when the external magnetic field changes, that is, the change in magnetic entropy, which leads to the spontaneous absorption and release of heat from the material to the outside. During excitation, the magnetic moment order of the magnetic material increases, and the magnetic entropy decreases, at which point the magnetic working fluid releases heat. During demagnetization, the magnetic moment order of the magnetic material decreases, and the magnetic entropy increases, at which point the magnetic working fluid absorbs heat from the outside. The core of magnetic refrigeration technology is the magnetic field and the magnetic refrigeration material. Generally, the higher the magnetic field, the higher the cooling capacity of the magnetic refrigeration material, but the cost also increases significantly. Therefore, researchers of magnetic refrigeration materials have been committed to obtaining magnetic refrigeration materials with large magnetic entropy changes and adiabatic temperature changes under low fields.

[0003] Rare earth metal compounds have become one of the research focuses in the field of magnetic refrigeration materials due to their advantages such as simple and reliable preparation process, large-scale production capability, easy molding and processing, and low cost. Summary of the Invention

[0004] The purpose of this invention is to provide a rare-earth cobalt-boron-carbon magnetic refrigeration material, its preparation method, and its application, thereby solving the problem of low magnetic entropy change in existing magnetic refrigeration materials.

[0005] To achieve the above objectives, the present invention provides a rare earth cobalt boron carbon magnetic refrigeration material, wherein the molecular formula of the magnetic refrigeration material is RECoBC, and RE is one or a mixture of rare earth elements Gd, Tb, Dy, Ho, Er, and Tm.

[0006] A method for preparing the above-mentioned rare-earth cobalt-boron-carbon magnetic refrigeration material includes the following steps:

[0007] S1. Weigh the raw materials, including rare earth metals, cobalt, boron, and carbon, according to their molecular formula molar ratios, mix them evenly, and obtain a mixture.

[0008] S2. Place the mixture into a melting furnace, draw a vacuum, and heat it under a protective gas atmosphere until the mixture is completely melted. Cool it to obtain a billet.

[0009] S3. Turn the billet over, melt it again and cool it. Repeat this process 3 to 5 times, each time for 40 to 60 seconds, to obtain a uniform alloy billet.

[0010] S4. Remove the oxide layer on the surface of the alloy ingot and perform heat treatment on the alloy ingot to obtain the magnetic refrigeration material.

[0011] 5. The method for preparing a rare earth cobalt boron carbon magnetic refrigeration material according to claim 4, characterized in that: in step S1, the amount of rare earth metal and carbon element weighed is 102% to 103% of the theoretical value.

[0012] Preferably, in step S2, the melting method in the melting furnace is high-vacuum electric arc discharge melting, and the working current is 140A to 220A.

[0013] Preferably, in step S2, the vacuum degree is 1×10 Pa to 3×10 Pa, and the protective gas is high-purity nitrogen or argon.

[0014] Preferably, in step S4, the heat treatment temperature is 800℃~1000℃, the heat treatment holding time is 5 days~9 days, tantalum foil is used to wrap the alloy ingot during heating and vacuum sealing is performed, and 0℃ ice water quenching is performed after heating.

[0015] Preferably, the prepared magnetic refrigeration material exhibits a maximum isothermal magnetic entropy change of 11.7 J / kgK to 18.1 J / kgK under a magnetic field change of 0 to 5 T, and a maximum isothermal magnetic entropy change of 15.2 J / kgK to 21.9 J / kgK under a magnetic field change of 0 T to 7 T.

[0016] Application of rare earth cobalt boron carbon magnetic refrigeration materials in magnetic refrigeration devices.

[0017] The advantages and positive effects of the rare-earth cobalt-boron-carbon magnetic refrigeration material, its preparation method, and its application described in this invention are as follows:

[0018] 1. This invention obtains a series of magnetic refrigeration materials by adjusting the composition of RE elements. The magnetic transition temperature of the magnetic refrigeration materials is around 20K, which can meet the refrigeration needs of the medium and low temperature ranges.

[0019] 2. The RECoBC magnetic refrigeration material described in this invention has a maximum isothermal magnetic entropy change of 11.7 J / kgK to 18.1 J / kgK under a magnetic field change of 0 to 5T, and a maximum isothermal magnetic entropy change of 15.2 J / kgK to 21.9 J / kgK under a magnetic field change of 0T to 7T; it has a high magnetic entropy change.

[0020] 3. The preparation method described in this invention is simple, has low material cost, and is suitable for industrial production.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 The graph shows the temperature and magnetization of the magnetic material prepared in Example 1 of this invention under a 0.1T magnetic field.

[0023] Figure 2 The magnetic material prepared in Example 1 of this invention has magnetization intensity diagrams under different temperatures and magnetic fields.

[0024] Figure 3 The magnetic entropy diagram of the magnetic material prepared in Example 1 of this invention under magnetic field variations of 1T-7T;

[0025] Figure 4 The graph shows the temperature and magnetization of the magnetic material prepared in Example 3 of this invention under a 0.1T magnetic field.

[0026] Figure 5 The magnetic material prepared in Example 3 of this invention has magnetization intensity diagrams under different temperatures and magnetic fields.

[0027] Figure 6 The magnetic entropy diagram of the magnetic material prepared in Example 3 of the present invention under magnetic field variations of 1T-7T. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] A rare-earth cobalt-boron-carbon magnetic refrigeration material with the molecular formula RECoBC, where RE is one or a mixture of rare-earth elements Gd, Tb, Dy, Ho, Er, and Tm.

[0030] The preparation method of the above-mentioned rare earth cobalt boron carbon magnetic refrigeration material includes the following steps:

[0031] S1. Weigh the raw materials, including rare earth metals, cobalt, boron, and carbon, according to their molecular formula molar ratios, mix them evenly, and obtain a mixture.

[0032] Considering the loss of rare earth metals and carbon during the smelting process, the amount of rare earth metals and carbon elements weighed is 102% to 103% of the theoretical value.

[0033] S2. Place the mixture into a melting furnace, evacuate the furnace, and heat it under a protective gas atmosphere until the mixture is completely melted. Cool the mixture to obtain an ingot.

[0034] The melting process in the furnace is high-vacuum electric arc discharge melting, with a working current of 140A to 220A. The vacuum level is 1×10Pa to 3×10Pa, and the protective gas is high-purity nitrogen or argon.

[0035] S3. Turn the billet over, melt it again, and cool it. Repeat this process 3 to 5 times, each time for 40 to 60 seconds, to obtain a uniform alloy billet.

[0036] S4. Polish with sandpaper and clean with alcohol to remove the oxide layer on the surface of the alloy ingot. Then, heat-treat the alloy ingot to obtain the magnetic refrigeration material. The heat treatment temperature is 800℃~1000℃, and the heat treatment holding time is 5 to 9 days. During heating, the alloy ingot is wrapped with tantalum foil and vacuum-sealed to prevent oxidation during the high-temperature treatment. After heating, it is quenched in 0℃ ice water.

[0037] Example 1

[0038] The molecular formula of rare earth cobalt boron carbon magnetic refrigeration material is TbCoBC.

[0039] The preparation method of rare earth cobalt boron carbon magnetic refrigeration material includes the following steps:

[0040] S1. Weigh 2.6941g of metallic terbium, 0.9794g of metallic cobalt, 0.1797g of elemental boron and 0.2036g of elemental carbon, mix them evenly to obtain a mixture.

[0041] S2. Place the mixture into a melting furnace, evacuate to 1×10 Pa, and heat the mixture under argon protection using an electric arc discharge method with a working current of 150 A. After the mixture is completely melted, cool it to obtain a billet.

[0042] S3. Turn the billet over, melt it again, and cool it. Repeat this process 4 times, each time for 40s to 60s, to obtain a uniform alloy billet.

[0043] S4. The oxide layer on the surface of the alloy ingot is removed by sanding with sandpaper and cleaning with alcohol. The alloy ingot is then wrapped with tantalum foil and vacuum-sealed. The alloy ingot is then heat-treated at 920℃ for 8 days, followed by quenching in 0℃ ice water. This yields the TbCoBC magnetic refrigeration material.

[0044] Example 2

[0045] The molecular formula of rare earth cobalt boron carbon magnetic refrigeration material is DyCoBC.

[0046] The preparation method of rare earth cobalt boron carbon magnetic refrigeration material includes the following steps:

[0047] S1. Weigh 2.7144g of dysprosium metal, 0.9651g of cobalt metal, 0.1770g of boron, and 0.2006g of carbon, mix them evenly to obtain a mixture.

[0048] S2. Place the mixture into a melting furnace, evacuate to 3×10Pa, and heat the mixture under argon protection using an electric arc discharge method with a working current of 200A. After the mixture is completely melted, cool it to obtain a billet.

[0049] S3. Turn the billet over, melt it again, and cool it. Repeat this process 4 times, each time for 40s to 60s, to obtain a uniform alloy billet.

[0050] S4. The oxide layer on the surface of the alloy ingot is removed by sanding with sandpaper and cleaning with alcohol. The alloy ingot is then wrapped with tantalum foil and vacuum-sealed. The alloy ingot is then heat-treated at 920℃ for 8 days, followed by quenching in 0℃ ice water. This yields the DyCoBC magnetic refrigeration material.

[0051] Example 3

[0052] The molecular formula of rare earth cobalt boron carbon magnetic refrigeration material is HoCoBC.

[0053] The preparation method of rare earth cobalt boron carbon magnetic refrigeration material includes the following steps:

[0054] S1. Weigh 2.7279g of metallic holmium, 0.9556g of metallic cobalt, 0.1753g of elemental boron, and 0.1987g of elemental carbon, mix them evenly, and obtain a mixture.

[0055] S2. Place the mixture into a melting furnace, evacuate to 2×10Pa, and heat the mixture under argon protection using an electric arc discharge method with a working current of 180A. After the mixture is completely melted, cool it to obtain a billet.

[0056] S3. Turn the billet over, melt it again, and cool it. Repeat this process 5 times, each time for 40s to 60s, to obtain a uniform alloy billet.

[0057] S4. The oxide layer on the surface of the alloy ingot is removed by sanding with sandpaper and cleaning with alcohol. The alloy ingot is then wrapped with tantalum foil and vacuum-sealed. The alloy ingot is then heat-treated at 970℃ for 8 days, followed by quenching in 0℃ ice water. This yields the HoCoBC magnetic refrigeration material.

[0058] Example 4

[0059] The molecular formula of rare earth cobalt boron carbon magnetic refrigeration material is ErCoBC.

[0060] The preparation method of rare earth cobalt boron carbon magnetic refrigeration material includes the following steps:

[0061] S1. Weigh 2.7405g of metallic erbium, 0.9467g of metallic cobalt, 0.1736g of elemental boron, and 0.1968g of elemental carbon, mix them evenly to obtain a mixture.

[0062] S2. Place the mixture into a melting furnace, evacuate to 1×10 Pa, and heat the mixture under argon protection using an electric arc discharge method with a working current of 140 A. After the mixture is completely melted, cool it to obtain a billet.

[0063] S3. Turn the billet over, melt it again, and cool it. Repeat this process 3 times, each time for 40s to 60s, to obtain a uniform alloy billet.

[0064] S4. The oxide layer on the surface of the alloy ingot is removed by sanding with sandpaper and cleaning with alcohol. The alloy ingot is then wrapped with tantalum foil and vacuum-sealed. The alloy ingot is then heat-treated at 920℃ for 8 days, followed by quenching in 0℃ ice water. This yields the ErCoBC magnetic refrigeration material.

[0065] Example 5

[0066] The molecular formula of rare earth cobalt boron carbon magnetic refrigeration material is TmCoBC.

[0067] The preparation method of rare earth cobalt boron carbon magnetic refrigeration material includes the following steps:

[0068] S1. Weigh 2.7494g of metallic thulium, 0.9403g of metallic cobalt, 0.1725g of elemental boron and 0.1954g of elemental carbon, mix them evenly to obtain a mixture.

[0069] S2. Place the mixture into a melting furnace, evacuate to 1×10 Pa, and heat the mixture under argon protection using an electric arc discharge method with a working current of 180A. After the mixture is completely melted, cool it to obtain a billet.

[0070] S3. Turn the billet over, melt it again, and cool it. Repeat this process 4 times, each time for 40s to 60s, to obtain a uniform alloy billet.

[0071] S4. The oxide layer on the surface of the alloy ingot is removed by sanding with sandpaper and cleaning with alcohol. The alloy ingot is then wrapped with tantalum foil and vacuum-sealed. The alloy ingot is then heat-treated at 920℃ for 8 days, followed by quenching in 0℃ ice water. This yields the HoCoBC magnetic refrigeration material.

[0072] The thermomagnetic curves of the TbCoBC sample prepared in Example 1 were measured using a Vibrating Sample Magnetometer (VSM) accessory manufactured by Quantum Design, Inc., USA, under 0.1T zero magnetic field cooling (ZFC) and magnetic field cooling (FC) conditions. The results are as follows: Figure 1 As shown, it can be seen that the material undergoes a significant magnetic phase transition at low temperatures, and the phase transition temperatures coincide near the transition temperature, indicating good reversibility.

[0073] Further testing was conducted on the isothermal magnetization curves of the TbCoBC material under varying magnetic fields from 0 to 7 T, ranging from 2 K to 55 K. The results are as follows: Figure 2 As shown, the magnetization of this material changes significantly with temperature and magnetic field near the phase transition temperature, and tends to saturate at a magnetic field of 7T, indicating a potential large magnetocaloric effect.

[0074] The magnetic entropy change under different magnetic field variations can be calculated using Maxwell's relations and isothermal magnetization curves at different temperatures. (Appendix) Figure 3 This illustrates the relationship between the magnetic entropy change and temperature of the TbCoBC sample prepared in Example 1 of this invention under different magnetic field variations. Figure 3 It can be seen that the calculated maximum isothermal magnetic entropy changes of TbCoBC magnetic material under magnetic field variations of 0–5T and 0–7T are 11.7 J / kgK and 15.2 J / kgK, respectively.

[0075] Figure 4 The HoCoBC sample prepared for Example 3 of this invention was tested for thermomagnetic curves under zero magnetic field cooling (ZFC) and magnetic field cooling (FC) at 0.1T. The results show that the material exhibits a magnetic phase transition at low temperatures, and the ZFC and FC thermomagnetic curves coincide near the phase transition temperature, indicating good reversibility.

[0076] Figure 5 The isothermal magnetization curves of the HoCoBC sample prepared in Example 3 of this invention are shown in the range of 2K-44K under varying magnetic fields of 0-7T. The results indicate that the magnetization intensity of this material changes significantly with temperature and magnetic field near the phase transition temperature, and tends to saturate at low temperatures with a magnetic field of 7T, exhibiting a potential large magnetocaloric effect.

[0077] Figure 6 The magnetic entropy change of the HoCoBC sample prepared in Example 3 of this invention under different magnetic field variations can be calculated using Maxwell's relation based on the isothermal magnetization curves at different temperatures. The maximum isothermal magnetic entropy changes of the HoCoBC material under magnetic field variations of 0–5T and 0–7T are 18.1 J / kgK and 21.9 J / kgK, respectively.

[0078] The DyCoBC magnetic refrigeration material prepared in Example 2 exhibits isothermal magnetic entropy changes of 16.1 J / kgK and 19.7 J / kgK under magnetic field variations of 0–5 T and 0–7 T, respectively.

[0079] The ErCoBC magnetic material prepared in Example 4 exhibits isothermal magnetic entropy changes of 14.4 J / kgK and 16.1 J / kgK under magnetic field variations of 0–5 T and 0–7 T, respectively.

[0080] The TmCoBC material prepared in Example 5 exhibits isothermal magnetic entropy changes of 17.8 J / kgK and 19.8 J / kgK under magnetic field variations of 0–5 T and 0–7 T, respectively.

[0081] Therefore, the present invention, by employing the above-mentioned rare-earth cobalt-boron-carbon magnetic refrigeration material, its preparation method, and its application, can solve the problem of low magnetic entropy change in existing magnetic refrigeration materials.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A rare-earth cobalt-boron-carbon magnetic refrigeration material, characterized in that: The molecular formula of the rare earth cobalt boron carbon magnetic refrigeration material is RECoBC, where RE is one or a mixture of rare earth elements Gd, Tb, Dy, Ho, Er, and Tm.

2. A method for preparing the rare-earth cobalt-boron-carbon magnetic refrigeration material according to claim 1, characterized in that, Includes the following steps: S1. Weigh the raw materials, including rare earth metals, cobalt, boron, and carbon, according to their molecular formula molar ratios, mix them evenly, and obtain a mixture. S2. Place the mixture into a melting furnace, draw a vacuum, and heat it under a protective gas atmosphere until the mixture is completely melted. Cool it to obtain a billet. S3. Turn the billet over, melt it again and cool it. Repeat this process 3 to 5 times, each time for 40 to 60 seconds, to obtain a uniform alloy billet. S4. Remove the oxide layer on the surface of the alloy ingot and perform heat treatment on the alloy ingot to obtain the magnetic refrigeration material.

3. The preparation method of a rare earth cobalt boron carbon magnetic refrigeration material according to claim 2, characterized in that: In S1, the amount of rare earth metals and carbon elements weighed is 102% to 103% of the theoretical value.

4. The preparation method of a rare earth cobalt boron carbon magnetic refrigeration material according to claim 2, characterized in that: In S2, the melting method in the melting furnace is high-vacuum electric arc discharge melting, and the working current is 140A to 220A.

5. The method for preparing a rare-earth cobalt-boron-carbon magnetic refrigeration material according to claim 2, characterized in that: In S2, the vacuum degree is 1×10 Pa to 3×10 Pa, and the protective gas is high-purity nitrogen or argon.

6. The method for preparing a rare-earth cobalt-boron-carbon magnetic refrigeration material according to claim 2, characterized in that: In S4, the heat treatment temperature is 800℃~1000℃, the heat treatment holding time is 5 days~9 days, tantalum foil is used to wrap the alloy ingot during heating and vacuum sealing is performed, and 0℃ ice water quenching is performed after heating.

7. The method for preparing a rare-earth cobalt-boron-carbon magnetic refrigeration material according to claim 2, characterized in that: The prepared magnetic refrigeration material exhibits a maximum isothermal magnetic entropy change of 11.7 J / kgK to 18.1 J / kgK under magnetic field variations of 0–5 T, and a maximum isothermal magnetic entropy change of 15.2 J / kgK to 21.9 J / kgK under magnetic field variations of 0 T to 7 T.

8. The rare-earth cobalt-boron-carbon magnetic refrigeration material according to claim 1, characterized in that: The rare-earth cobalt-boron-carbon magnetic refrigeration material is used in magnetic refrigeration devices.

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