La-Fe-Si-based magnetic refrigeration composite material and preparation method thereof

Abstract

This invention relates to a La-Fe-Si based magnetic refrigeration composite material and its preparation method. The La-Fe-Si based magnetic refrigeration composite material is a layered structure formed by alternating layers of a first constituent layer and a second constituent layer, which are then pressed together. The first constituent layer contains pores and multiple magnetocaloric phase units, and the second constituent layer contains Fe or an Fe alloy. The magnetocaloric phase is NaZn. 13 La(Fe,Si) crystal structure 13 Based on the La-Fe-Si based magnetic refrigeration composite material, after high-temperature reaction, the magnetocaloric phase units in the first constituent layer are interconnected to form an integral structure. Thus, during hydrogen expansion, the pores act as a buffer, preventing the grains and grain phases from being squeezed and broken, and reducing the overall volume change of the La-Fe-Si based alloy layer. Furthermore, because the Fe or Fe alloy particles are dense and still have a continuous layered structure, and are closely connected to the La-Fe-Si based alloy layer, the resulting layered structure inhibits the separation of the composite material layers caused by hydrogen filling. The layered composite material after hydrogen filling basically maintains its original shape and does not break.

Description

Technical Field

[0001] This invention relates to a magnetic refrigeration material, and more particularly to a La-Fe-Si based magnetic refrigeration composite material, belonging to the field of magnetic refrigeration materials. Background Technology

[0002] Traditional gas compression refrigeration technology generally suffers from many problems such as low efficiency, high energy consumption, and high greenhouse gas emissions. Magnetic refrigeration, as a highly efficient, energy-saving, and environmentally friendly refrigeration technology, has attracted widespread attention and has become one of the most promising methods to replace traditional gas compression refrigeration. Compared with traditional gas compression refrigeration, the advantages of magnetic refrigeration are: (1) high refrigeration efficiency, with a COP value of over 16, while the COP of gas compression refrigeration is less than 5; (2) low energy consumption, saving 30% more energy than traditional refrigeration; (3) no greenhouse gas emissions, making it environmentally friendly; and (4) low noise, high reliability, and easy maintenance.

[0003] The working principle of magnetic refrigeration is mainly based on the magnetocaloric effect of magnetic materials. Early research in this field focused on improving the magnetocaloric effect and related magnetic properties of materials. Since 1997, materials exhibiting room-temperature giant magnetocaloric effects have been discovered, including Gd5(Si,Ge)4-based alloys, MnAs-based alloys, MnFe(P,As,Si,Ge)-based alloys, and La(Fe,Si). 13 NaZn alloys and Heusler alloys, among others. 13 La(Fe,Si) crystal structure 13 The base alloys exhibit high entropy change, adiabatic temperature change, and low hysteresis, and their Curie temperature can be adjusted to room temperature through element doping and substitution. More notably, these alloys are widely recognized as one of the most likely materials for widespread use in magnetic refrigerators due to their abundant raw materials (La is a highly abundant rare earth element), low cost, and lack of toxic elements. Research indicates that hydrogenation is an effective method for achieving both large magnetocaloric effects and near-room temperature operation in these materials. However, La(Fe,Si)... 13 The compound is extremely brittle; the introduction of interstitial hydrogen atoms causes the lattice to expand dramatically, initiating cracks and leading to severe breakage of the bulk alloy, sometimes even turning it into powder. On the other hand, current magnetic refrigeration technologies generally employ an active regenerative heating mode. This mode requires the magnetic refrigerant to exchange heat rapidly and sufficiently with the heat exchange fluid to improve the efficiency of the magnetic refrigeration system. To achieve this, the magnetic refrigerant material needs to be processed into geometric shapes with a large specific surface area (such as thin sheets or spheres) and its thermal conductivity needs to be improved. An even more ideal design would be to increase the thermal conductivity of the magnetic refrigerant perpendicular to the heat exchange fluid while decreasing its thermal conductivity along the fluid direction, thus achieving strong anisotropic thermal conductivity of the magnetic refrigerant.

[0004] The La(Fe,Si) reported so far 13 The microstructure and properties of most basic magnetic refrigeration materials are isotropic. For example, the Chinese invention patent "Binding La(FeSi)..." 13 The patent titled "Based Magnetothermic Material, Preparation Method and Application Thereof" (patent number ZL201110374158.1, authorized publication number CN103137281B) discloses a bonded La(FeSi) material. 13 The basic magnetocaloric effect material is bonded and thermoset using adhesives. By adjusting the molding pressure, thermosetting temperature, and thermosetting atmosphere, high-strength bonded La(Fe,Si) materials can be obtained. 13 The basic magnetocaloric effect material overcomes the inherent fragility of magnetocaloric materials; the magnetic entropy change remains essentially unchanged compared to before bonding, but the poor thermal conductivity of polymer adhesives results in very low thermal conductivity in all directions of the composite material. The applicant's earlier Chinese invention patent application, "A Rare Earth-Iron-Silicon Based Magnetically Refrigerating Composite Material and Its Preparation Method," patent number ZL201710849594.7 (authorization announcement number CN109524190B), discloses a rare earth-iron-silicon based magnetically refrigerating composite material in which low-density, high-thermal-conductivity aluminum metal or aluminum alloy is mixed with rare earth-iron-silicon based alloy particles and hot-pressed to obtain a bulk magnetically refrigerating composite material. Aluminum metal or aluminum alloy serves as a second component to bond the rare earth-iron-silicon based alloy particles together. The two matrix components easily overlap to form a network structure, significantly enhancing thermal conductivity and mechanical properties, but the thermal conductivity remains the same in all directions. In recent years, in order to further improve the heat exchange efficiency of magnetic regenerators and reduce the internal heat loss of magnetic working fluids, researchers in this field have gradually developed La(Fe,Si) with anisotropic thermal conductivity. 13 Magnetothermic materials. For example, in non-patent literature (Acta Materialia 2020, 187, 1), a room-temperature free forging method was used to deform a cast La-Fe-Si alloy, followed by annealing, to prepare fully dense La(Fe,Si). 13 / Fe lamellar composite material, in which the Fe is in lamellar form, has a room temperature thermal conductivity difference of approximately 1.5 W / mK perpendicular to and parallel to the applied pressure direction, which is far from the ideal value. To obtain good overall performance, La(Fe,Si) 13 Magnetic refrigeration materials rely on a second phase to enhance their mechanical and thermal conductivity. During hydrogen absorption, the La(Fe,Si) phase in the composite material... 13 The crystal lattice expands isotropically, while the volume of the second phase often remains constant. For composite materials with macroscopic anisotropic structures, large stresses are easily generated between the magnetocaloric phase and the second phase, which can lead to phase separation and make it difficult to form a complete bulk material.

[0005] Therefore, it is necessary to further improve existing La-Fe-Si based magnetic refrigeration materials to obtain bulk materials that simultaneously possess large magnetocaloric effects at near room temperature and strong anisotropic thermal conductivity, in order to meet the requirements for designing and manufacturing high-performance magnetic refrigeration systems. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a La-Fe-Si based magnetic refrigeration composite material that has a large magnetocaloric effect and strong anisotropic thermal conductivity, while ensuring the integrity of its shape after hydrogen filling, in view of the current status of the prior art.

[0007] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned La-Fe-Si based magnetic refrigeration composite material.

[0008] The technical solution adopted by the present invention to solve the first technical problem mentioned above is as follows: a La-Fe-Si based magnetic refrigeration composite material, characterized in that the La-Fe-Si based magnetic refrigeration composite material is a layered structure formed by alternating layers of a first constituent layer and a second constituent layer, wherein the first constituent layer contains pores and multiple magnetocaloric phase units, and each magnetocaloric phase is interconnected to form an integral structure, the second constituent layer contains Fe or Fe alloy, and the magnetocaloric phase is composed of NaZn 13 La(Fe,Si) crystal structure 13 Basic compounds.

[0009] The second component layer is a toughening layer, and its thermal conductivity is higher than that of the first component layer.

[0010] The NaZn 13 La(Fe,Si) crystal structure 13 The general chemical formula of the basic compound is: La 1-x R x (Fe 1-a M a ) 13- y Si y A z Wherein, R is selected from any one or more combinations of Ce, Pr and Nd elements; M is selected from any one or more combinations of Cr, Mn, Co, Ni and Al elements; A is H element; or, A is selected from one or more combinations of B and C elements and H; 0≤x≤0.5, 1≤y≤2, 0≤z≤0.5, 0≤a≤0.1.

[0011] In the La-Fe-Si-based magnetic refrigeration composite material, by mass percentage, the content e of the first component layer in the La-Fe-Si-based magnetic refrigeration composite material satisfies: 60 wt.% < e < 100 wt.%, and the content f of the second component layer in the La-Fe-Si-based magnetic refrigeration composite material satisfies: 0 < f < 40 wt.%. In the La-Fe-Si-based magnetic refrigeration composite material of the present invention, the first component layer contains La(Fe,Si) 13 -based compounds, which are the source of the magnetocaloric effect. The second component layer serves as a high thermal conductivity channel and is the source of anisotropic heat conduction, but does not produce a magnetocaloric effect. To balance the magnetocaloric and thermal conductivity properties of the composite material, the proportion contents of the two layers need to be strictly limited, and the sum of the contents of the two layers is 100 wt.%.

[0012] Preferably, the content f satisfies: 10 wt.% ≤ f ≤ 20 wt.%.

[0013] If the first component layer further includes a non-magnetocaloric phase, then the first component layer consists only of La(Fe,Si) 13 -based magnetocaloric phase, pores, and non-magnetocaloric phase. By volume percentage, the content g of the magnetocaloric phase in the first component layer satisfies: 60 < g < 100 vol.%, the content h of the pores in the first component layer satisfies: 0 < h < 20 vol.%, and the content m of the non-magnetocaloric phase in the first component layer satisfies: 0 ≤ m < 20 vol.%. In the La-Fe-Si-based magnetic refrigeration composite material of the present invention, the magnetocaloric phase provides the magnetocaloric effect, while the pores and non-magnetocaloric phase can both eliminate the stress caused by the hydrogen absorption expansion of part of the magnetocaloric phase, hinder the internal crack propagation of the first component layer, and inhibit the separation between the first component layer and the second component layer, ensuring the geometric integrity of the composite material after hydrogen absorption. However, if the pores and non-magnetocaloric phase are too much, it will inevitably lead to a serious reduction in the magnetocaloric performance of the composite material. Therefore, the proportion contents of each component phase in the first component layer need to be strictly limited.

[0014] The La-Fe-Si-based magnetic refrigeration composite material has a Curie temperature range of 150K to 350K, and the entropy change value under a 2T magnetic field change is not less than 8 J / kgK, so the La-Fe-Si-based magnetic refrigeration composite material has a large magnetocaloric effect near room temperature.

[0015] For the La-Fe-Si-based magnetic refrigeration composite material, the stacking direction of the layered structure is recorded as the first direction, and the direction perpendicular to the first direction is the second direction. The difference Δλ between the thermal conductivity λ1 along the first direction and the thermal conductivity λ2 along the second direction of the La-Fe-Si-based magnetic refrigeration composite material satisfies: Δλ ≥ 2 W / mK.

[0016] The La-Fe-Si based magnetic refrigeration composite material can be processed into a thickness of less than 2 mm and a cross-sectional area of ​​not less than 100 mm². 2 The plate-shaped material. After being filled with hydrogen, the plate-shaped material retains its original shape without breaking.

[0017] The cross-sectional area mentioned above is the product of the length and the width.

[0018] The technical solution adopted by the present invention to solve the second technical problem mentioned above is: a method for preparing the La-Fe-Si based magnetic refrigeration composite material, characterized in that it includes the following steps in sequence:

[0019] 1) According to the chemical formula La 1-x R x (Fe 1-a M a ) (13-y)b Si y A z The raw materials are configured as follows: R is selected from any one or more combinations of Ce, Pr and Nd elements; M is selected from any one or more combinations of Cr, Mn, Co, Ni and Al elements; A is selected from one or more combinations of B and C elements; 0≤x≤0.5, 1≤y≤2, 0.1≤z≤3, 0≤a≤0.1, 0.5≤b≤1.5;

[0020] 2) Melt the raw materials prepared in step 1) to form La. 1-x R x (Fe 1-a M a ) (13-y)b Si y A z alloy;

[0021] 3) Melt the La in step 2). 1-x R x (Fe 1-a M a ) (13-y)b Si y A z The alloy was crushed into powder;

[0022] 4) Remove the crushed La from step 3) 1-x R x (Fe 1-a M a ) (13-y)b Si y A zAlloy powder is used as the first constituent layer, and Fe or Fe alloy powder is used as the second constituent layer. After being laid flat, it is pressed into a blank. The Fe alloy powder is a binary or multi-element alloy powder composed of Fe and Cr, Mn, Co, Ni, Al, B, C and Si elements.

[0023] 5) Anneal the pressed billet from step 4) to obtain a material with NaZn content. 13 Phases with a crystal structure of type ;

[0024] 6) The annealed blank from step 5) is subjected to hydrogen charging to form a La-Fe-Si based room temperature magnetic refrigeration composite material.

[0025] Preferably, in step 4) above, the molding is performed in a high vacuum environment or an inert atmosphere. If the pressing temperature is room temperature, the pressing pressure is 0.5–1.5 GPa. In step 5) above, the heat treatment temperature is 1000–1200°C, and the time is 5–72 hours.

[0026] In implementing this invention, it was discovered that the thermal conductivity in both the first and second directions is inversely proportional to the total thickness of the first and second constituent layers. The porosity characteristics in the first constituent layer are related to the powder particle size; the smaller the particle size, the smaller and more numerous the pores. This results in higher integrity of the composite material after hydrogen purging. Therefore, the sum of the thicknesses of the first and second constituent layers is less than 5 mm, and the particle size of the powder in the first constituent layer is less than 300 μm.

[0027] Another technical solution adopted by the present invention to solve the second technical problem mentioned above is: a method for preparing the La-Fe-Si based magnetic refrigeration material, characterized in that it includes the following steps in sequence:

[0028] 1) According to R x Fe 13-y Si y Chemical formula for raw materials; wherein R is La; or R is selected from any one or a combination of two or more elements Ce, Pr, and Nd, and La, x satisfies: 1≤x≤7, y satisfies: 1≤y≤10;

[0029] 2) Melt the raw materials prepared in step 1) to form an alloy, and then R x Fe 13-y Si y The alloy was crushed into powder;

[0030] 3) Take the broken R from step 2) x Fe 13-y Si y Alloy powder is used as an intermediate with Fe powder and Si powder; or, with Fe powder, Si powder and alloy powder respectively according to R x(Fe 1-a M a ) (13-y)b Si y A z The chemical formula is used to prepare a mixed powder, wherein the alloy powder is a binary or multi-element alloy powder composed of Fe and Cr, Mn, Co, Ni, Al, B, C, and Si elements; R is La; or R is selected from any one or two or more combinations of Ce, Pr, and Nd elements and La; M is selected from any one or two or more combinations of Cr, Mn, Co, Ni, and Al elements; A is selected from one or two combinations of B and C, where x satisfies: 0.8≤x≤1.2, y satisfies: 1≤y≤2, z satisfies: 0≤z≤0.5, a satisfies: 0≤a≤0.1, and b satisfies: 0.5≤b≤1.5;

[0031] 4) Mix the R in step 3) x (Fe 1-a M a ) (13-y)b Si y A z Alloy powder is used as the first constituent layer, and Fe or Fe alloy powder is used as the second constituent layer. After being laid flat, it is pressed into a blank. The Fe alloy powder is a binary or multi-element alloy powder composed of Fe and Cr, Mn, Co, Ni, Al, B, C and Si elements.

[0032] 5) Anneal the pressed billet from step 4) to obtain a material with NaZn content. 13 Phases with a crystal structure of type ;

[0033] 6) The annealed blank from step 5) is subjected to hydrogen charging to form a La-Fe-Si based room temperature magnetic refrigeration composite material.

[0034] Preferably, in step 4) above, the molding is performed in a high vacuum environment or an inert atmosphere. If the pressing temperature is room temperature, the pressing pressure is 0.5–1.5 GPa. In step 5) above, the heat treatment temperature is 1000–1200°C, and the time is 5–72 hours.

[0035] Compared with the prior art, the advantages of the present invention are as follows: the La-Fe-Si based magnetic refrigeration composite material is a layered structure formed by alternating layers of a first constituent layer and a second constituent layer, pressed together. The first constituent layer is a La-Fe-Si based alloy layer, and the second constituent layer contains Fe or Fe alloy. After high-temperature reaction, the La-Fe-Si based alloy layer (i.e., the first constituent layer) includes a magnetocaloric phase and pores, and each of the magnetocaloric phase units is interconnected to form an integral structure. Thus, during hydrogen expansion, the pores act as a buffer, preventing the grains and grain phases from being squeezed and broken, and reducing the overall volume change of the La-Fe-Si based alloy layer. Furthermore, because the Fe or Fe alloy particles are dense and still form a continuous layered structure, and are closely connected to the La-Fe-Si based alloy layer, the layered structure obtained by the present invention inhibits the separation of the composite layers caused by hydrogen filling, and the layered composite material after hydrogen filling basically maintains its original shape without breaking.

[0036] Existing technologies typically prioritize obtaining a magnetocaloric phase with a magnetocaloric effect and then pressing it into shape. However, pressure and temperature inevitably damage this phase, leading to a significant reduction in the magnetocaloric effect. This invention avoids this damage by pressing cast La-Fe-Si based alloy powder with Fe and Si powders before obtaining the magnetocaloric phase. Therefore, the resulting La-Fe-Si based magnetic refrigeration composite material exhibits a large near-room-temperature magnetocaloric effect. Furthermore, compared to existing forging techniques, this invention uses molding technology to composite the La-Fe-Si based alloy with Fe or Fe alloy. By changing the thickness of the first and second constituent layers, the ratio of the two layers, and the pressing pressure, the magnetocaloric effect and thermal conductivity in different directions can be controlled. Therefore, it is easier to achieve stable layered structures and mass production of the composite material. Attached Figure Description

[0037] Figure 1(a) shows La in Embodiment 1 of the present invention. 0.7 Ce 0.3 Fe 11.6 Si 1.4 Backscattering mode scanning electron microscope image of / Fe magnetic refrigeration composite material;

[0038] Figure 1(b) shows La in Embodiment 1 of the present invention. 0.7 Ce 0.3 Fe 11.6 Si 1.4 A magnified scanning electron microscope image of the first constituent layer of the Fe magnetic refrigeration composite material;

[0039] Figure 2(a) shows La in Embodiment 1 of the present invention. 0.7 Ce 0.3 Fe 11.6 Si 1.4Thermomagnetic (MT) curves of Fe magnetic refrigeration composite material under a 0.05T magnetic field;

[0040] Figure 2(b) shows the hydrogenated La in Example 1 of the present invention. 0.7 Ce 0.3 Fe 11.6 Si 1.4 H z Thermomagnetic (MT) curves of Fe magnetic refrigeration composite material under a 0.05T magnetic field;

[0041] Figure 3 It is the hydrogenated La in Example 1 of this invention 0.7 Ce 0.3 Fe 11.6 Si 1.4 H z Isothermal magnetization (MH) curves of Fe magnetic refrigeration composite material under different temperatures during the rising and falling fields;

[0042] Figure 4 It is the hydrogenated La in Example 1 of this invention 0.7 Ce 0.3 Fe 11.6 Si 1.4 H z Entropy change curves of Fe magnetic refrigeration composite material under magnetic field changes of 1T and 2T as a function of temperature;

[0043] Figure 5 It is the hydrogenated La in Example 1 of this invention 0.7 Ce 0.3 Fe 11.6 Si 1.4 H z Thermal conductivity of / Fe magnetic refrigeration composite material as a function of temperature in the first and second directions;

[0044] Figure 6 La in Embodiment 2 of the present invention 0.84 Ce 0.36 Fe 13.68 Si 1.6 Backscattering mode scanning electron microscope image of / Fe magnetic refrigeration composite material;

[0045] Figure 7 This refers to the hydrogenated La in Example 2 of the present invention. 0.84 Ce 0.36 Fe 13.68 Si 1.6 H z Thermomagnetic (MT) curves of Fe magnetic refrigeration composite material under a 0.05T magnetic field;

[0046] Figure 8 The hydrogenated La in Example 2 of this invention0.84 Ce 0.36 Fe 13.68 Si 1.6 H z Isothermal magnetization (MH) curves of Fe magnetic refrigeration composite material under different temperatures during the rising and falling fields;

[0047] Figure 9 The hydrogenated La in Example 2 of this invention 0.84 Ce 0.36 Fe 13.68 Si 1.6 H z The entropy change of / Fe magnetic refrigeration composite material under magnetic field changes of 1T and 2T as a function of temperature. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, in the following embodiments, the purity of the raw materials used is as follows: the purity of La, Ce, Fe, and Si is all above 99% (mass percentage content).

[0049] Example 1:

[0050] The general chemical formula of the La-Fe-Si based magnetic refrigeration composite material in this embodiment is: La 0.7 Ce 0.3 Fe 11.6 Si 1.4 H z / Fe.

[0051] La in this embodiment was observed using a scanning electron microscope. 0.7 Ce 0.3 Fe 11.6 Si 1.4 The microstructure of the / Fe magnetic refrigeration composite material is shown in Figures 1(a) and (b). This sample consists of a first constituent layer 1 and a second constituent layer 2 forming a unit. The first and second constituent layers 1 and 2 are alternately stacked to form a layered structure. The aforementioned first constituent layer 1 consists of a magnetocaloric phase 11, pores 12, and a non-magnetocaloric phase 13, wherein the volume fraction of the pores is approximately 8.9%. The magnetocaloric phase 11 is NaZn. 13 La(Fe,Si) crystal structure 13 The base compound (gray area) consists of interconnected magnetocaloric phases 11 forming a monolithic structure, with a volume fraction of approximately 80.7%. The non-magnetocaloric phase 13 is primarily composed of α-(Fe,Si) (black area) and La-Ce-rich rare earth phases (white area), with the α-(Fe,Si) phase comprising approximately 9.7% of the volume. It can be seen that the fine non-magnetocaloric phase 13 is dispersed within the magnetocaloric phase 11. The second constituent layer 2 is mainly α-(Fe,Si), with a thickness of approximately 0.3 mm. This layered La...0.7 Ce 0.3 Fe 11.6 Si 1.4 The Fe magnetic refrigeration composite material retains its complete shape even after being filled with hydrogen.

[0052] In this embodiment, La 0.7 Ce 0.3 Fe 11.6 Si 1.4 The preparation method of / Fe magnetic refrigeration composite material includes the following steps:

[0053] 1) Press La 0.7 Ce 0.3 Fe 11.6 Si 1.4 Chemical ingredients are loaded into a crucible in a vacuum induction rapid solidification furnace. After evacuation, high-purity argon gas is introduced. Once the temperature rises to the point where the raw materials are completely melted and the alloy melt is homogeneous, the alloy liquid is poured onto a rotating copper roller to form an alloy sheet.

[0054] 2) The La prepared in step 1) 0.7 Ce 0.3 Fe 11.6 Si 1.4 The alloy sheets are mechanically crushed into powder and then sieved.

[0055] 3) The La particles with a diameter of 75–150 μm obtained from sieving in step 2) 0.7 Ce 0.3 Fe 11.6 Si 1.4 Alloy powder, as the first constituent layer, and Fe powder with a particle size of 75–150 μm, as the second constituent layer, are alternately poured into a mold in a nitrogen glove box and leveled; wherein, La 0.7 Ce 0.3 Fe 11.6 Si 1.4 The mass of a single layer of powder is 1g, and the mass of a single layer of Fe powder is 0.25g. The layered powders are pressed into a green body at room temperature under a pressure of 1GPa.

[0056] 4) Press the La in step 3) 0.7 Ce 0.3 Fe 11.6 Si 1.4 The Fe blank was placed in a quartz tube, evacuated, filled with argon gas, and then sealed.

[0057] 5) Place the quartz tube containing the embryo from step 4) into an annealing furnace, heat to 1050℃, and anneal for 1 day to form a structure containing NaZn. 13 La-type structured magnetocaloric phase 0.7 Ce 0.3 Fe 11.6 Si 1.4 / Fe magnetic refrigeration composite material;

[0058] 6) Anneal the La from step 5) 0.7 Ce 0.3 Fe 11.6 Si 1.4 / Fe composite material was saturated with hydrogen at 300℃ and 0.2MPa to obtain La 0.7 Ce 0.3 Fe 11.6 Si 1.4 H z / Fe magnetic refrigeration composite material.

[0059] Physical performance testing:

[0060] I. La obtained in steps 5) and 6) was measured using a superconducting quantum interference device (SQUID) vibrating sample magnetometer (MPMS) VSM. 0.7 Ce 0.3 Fe 11.6 Si 1.4 / Fe and hydrogenated La 0.7 Ce 0.3 Fe 11.6 Si 1.4 H z / Fe magnetic refrigeration composite thermomagnetic (MT) curves, and La 0.7 Ce 0.3 Fe 11.6 Si 1.4 H z Isothermal magnetization (MH) curves of the / Fe magnetic refrigeration composite material at different temperatures. Figures 2(a) and (b) show that La... 0.7 Ce 0.3 Fe 11.6 Si 1.4 The Curie temperature of the Fe composite material is 170K, while the Curie temperature of the hydrogenated composite material increases to 315K. For example... Figure 3 As shown, near the Curie temperature, the magnetization curve of the sample exhibits a distinct inflection point, demonstrating a first-order variability transition from paramagnetic to ferromagnetic states. According to Maxwell's relation:

[0061]

[0062] Calculate the entropy change under different temperatures and magnetic field variations from the isothermal magnetization curve. Figure 4 It can be seen that low magnetic field changes can cause large entropy changes in this layered composite material. The maximum entropy changes under magnetic field changes of 0-1T and 0-2T are 12.1J / kgK and 14.9J / kgK, respectively.

[0063] II. Using a laser thermal conductivity analyzer (LFA) to test the La obtained in step 5).0.7 Ce 0.3 Fe 11.6 Si 1.4 / Fe layered composite material and hydrogenated La obtained in step 6) 0.7 Ce 0.3 Fe 11.6 Si 1.4 H z Thermal conductivity of Fe layered composite materials. Figure 5 The thermal conductivity of the composite material after hydrogenation at different temperatures shows that the composite material exhibits significant anisotropic thermal conductivity. At room temperature, the thermal conductivity of the sample before hydrogen charging is 5.9 W / mK in the first direction P1 and 11.9 W / mK in the second direction P2, with a difference of 6.0 W / mK. After hydrogen charging, the thermal conductivity of the sample decreases slightly, with the thermal conductivity in the first direction being 6.5 W / mK and 8.5 W / mK in the second direction, with a difference of 2.0 W / mK. The first direction P1 refers to the stacking direction of the layered structure, as shown in Figure 1, and is also the thickness direction of the layered sample. The second direction P2 is perpendicular to the first direction P1, i.e., along the direction of the first or second constituent layer, and also along the cross-section of the layered sample.

[0064] Example 2:

[0065] The general chemical formula of the La-Fe-Si based magnetic refrigeration composite material in this embodiment is: La 0.84 Ce 0.36 Fe 13.68 Si 1.6 H z / Fe.

[0066] La in this embodiment was observed using a scanning electron microscope. 0.84 Ce 0.36 Fe 13.68 Si 1.6 The microstructure of Fe magnetic refrigeration composite materials, such as Figure 6 As shown, the sample consists of alternating layers of a first constituent layer and a second constituent layer. The first constituent layer comprises a magnetocaloric phase, pores, and a non-magnetocaloric phase, with the pores accounting for approximately 11.3% of the volume. The magnetocaloric phase is NaZn. 13 La(Fe,Si) crystal structure 13The base compound (gray area) consists of interconnected magnetocaloric phases forming a monolithic structure, with a volume fraction of approximately 71.6%. The non-magnetocaloric phases are primarily α-(Fe,Si) (black area) and La-Ce-rich rare earth phases (white area), with the α-(Fe,Si) phase comprising approximately 16.0% of the volume. It can be seen that fine non-magnetocaloric phases are dispersed within the magnetocaloric phase. The second constituent layer is mainly α-(Fe,Si), with a thickness of approximately 0.2 mm. This layered La... 0.84 Ce 0.36 Fe 13.68 Si 1.6 The Fe magnetic refrigeration composite material retains its complete shape even after being filled with hydrogen.

[0067] In this embodiment, La 0.84 Ce 0.36 Fe 13.68 Si 1.6 The preparation method of / Fe magnetic refrigeration composite material includes the following steps:

[0068] 1) Press La 1.4 Ce 0.6 Fe 11 Si2 chemical formula is prepared and placed into a crucible in a vacuum induction melting furnace. After evacuation, high-purity argon gas is introduced. When the temperature rises to the point where the raw materials are completely melted and the alloy melt is uniform, the alloy liquid is poured into a copper mold to form an alloy ingot.

[0069] 2) The La prepared in step 1) 1.4 Ce 0.6 Fe 11 Si2 alloy ingots are mechanically crushed into powder and then sieved.

[0070] 3) The La particles with a diameter ≤38μm sieved in step 2) 1.4 Ce 0.6 Fe 11 Si2 alloy powder was used as an intermediate, and Fe powder and Si powder with a particle size ≤38μm were reacted according to the La... 0.84 Ce 0.36 Fe 13.68 Si 1.6 A chemically formulated mixed powder, serving as the first constituent layer, was alternately poured into a mold and leveled with Fe powder (particle size ≤38μm) as the second constituent layer in a nitrogen glove box. The mass of a single layer of mixed powder was 0.8g, and the mass of a single layer of Fe powder was 0.2g. The layered powder was then pressed into a green body at room temperature under a pressure of 1GPa.

[0071] 4) Press the La in step 3) 0.84 Ce 0.36 Fe 13.68 Si 1.6The Fe blank was placed in a quartz tube, evacuated, filled with argon gas, and then sealed.

[0072] 5) Place the quartz tube containing the embryo from step 4) into an annealing furnace, heat to 1080℃, and anneal for 3 days to form a structure containing NaZn. 13 La-type structured magnetocaloric phase 0.84 Ce 0.36 Fe 13.68 Si 1.6 / Fe magnetic refrigeration composite material;

[0073] 6) The La prepared in step 5) 0.84 Ce 0.36 Fe 13.68 Si 1.6 / Fe composite material was saturated with hydrogen at 300℃ and 0.2MPa to obtain La 0.84 Ce 0.36 Fe 13.68 Si 1.6 H z / Fe magnetic refrigeration composite material.

[0074] Physical performance testing:

[0075] I. La obtained in step 6) was measured using a superconducting quantum interference device (SQUID) vibrating sample magnetometer (MPMS). 0.84 Ce 0.36 Fe 13.68 Si 1.6 H z Thermomagnetic (MT) curves and isothermal magnetization (MH) curves at different temperatures of the / Fe magnetic refrigeration composite material. From Figure 7 It can be seen that the Curie temperature of the material is 315K. For example... Figure 8 As shown, near the Curie temperature, the magnetization curve of the sample exhibits a distinct inflection point, demonstrating a first-order variability transition from paramagnetic to ferromagnetic states. According to Maxwell's relation:

[0076]

[0077] Calculate the entropy change under different temperatures and magnetic field variations from the isothermal magnetization curve. Figure 9 It can be seen that low magnetic field changes can cause large entropy changes in this layered composite material. The maximum entropy changes under magnetic field changes of 0-1T and 0-2T are 7.9J / kgK and 10.7J / kgK, respectively.

[0078] II. Using a laser thermal conductivity analyzer (LFA) to test the La obtained in step 5). 0.84 Ce 0.36 Fe 13.68 Si 1.6 / Fe layered composite material and La obtained in step 6) 0.84 Ce 0.36 Fe 13.68 Si 1.6 H z Thermal conductivity of the Fe layered composite material. At room temperature, the thermal conductivity of the sample before hydrogen charging was 10.0 W / mK in the first direction and 16.2 W / mK in the second direction, with a difference of 6.2 W / mK between the two directions. After hydrogen charging, the thermal conductivity of the sample decreased slightly, with the thermal conductivity in the first direction being 5.8 W / mK and the thermal conductivity in the second direction being 9.9 W / mK, with a difference of 4.1 W / mK between the two directions, as shown in Table 1.

[0079] Example 3:

[0080] The general chemical formula of the La-Fe-Si based magnetic refrigeration material in this embodiment is: LaFe 11.6 Si 1.4 H z / Fe.

[0081] In this embodiment, LaFe 11.6 Si 1.4 H z The preparation method of the / Fe magnetic refrigeration composite material is different from that of Example 1 above, except that the annealing time in step 5) is different. Specifically, the annealing time is 3 days.

[0082] The sample consists of alternating layers of a first constituent layer and a second constituent layer. The first constituent layer comprises a magnetocaloric phase, porosity, and a non-magnetocaloric phase, with the porosity comprising approximately 11.2% by volume. The magnetocaloric phase is NaZn. 13 La(Fe,Si) crystal structure 13 The basic compound consists of interconnected magnetocaloric phases forming a monolithic structure, with the magnetocaloric phase comprising approximately 73.9% by volume. The non-magnetocaloric phase is primarily composed of α-(Fe,Si) and La-Ce-rich rare earth phases, with the α-(Fe,Si) phase comprising approximately 14.8% by volume. Fine non-magnetocaloric phase particles are dispersed within the magnetocaloric phase. The second constituent layer is mainly α-(Fe,Si), with a thickness of approximately 0.3 mm. This layered LaFe... 11.6 Si 1.4 The Fe magnetic refrigeration composite material retains its complete shape after being filled with hydrogen. The preparation process and physical properties are shown in Table 1.

[0083] Example 4:

[0084] The general chemical formula of the La-Fe-Si based magnetic refrigeration material in this embodiment is: La 0.84 Ce 0.36 Fe 13.68 Si 1.6 Hz / Fe.

[0085] In this embodiment, La 0.84 Ce 0.36 Fe 13.68 Si 1.6 H z The preparation method of the Fe magnetic refrigeration composite material is different from that of Example 2 above, except that the mass of the mixed powder monolayer and the mass of the Fe powder monolayer are different in step 3). Specifically, the mass of the mixed powder monolayer in step 3) is 1.6g and the mass of the Fe powder monolayer is 0.4g.

[0086] The sample consists of alternating layers of a first constituent layer and a second constituent layer. The first constituent layer comprises a magnetocaloric phase, porosity, and a non-magnetocaloric phase, with the porosity having a volume fraction of approximately 10.9%. The magnetocaloric phase is NaZn. 13 La(Fe,Si) crystal structure 13 The base compound consists of interconnected magnetocaloric phases forming a monolithic structure, with the magnetocaloric phase comprising approximately 72.2% by volume. The non-magnetocaloric phase is primarily composed of α-(Fe,Si) and La-Ce-rich rare earth alloys, with the α-(Fe,Si) phase comprising approximately 16.7% by volume. Fine non-magnetocaloric phase particles are dispersed within the magnetocaloric phase. The second constituent layer is mainly α-(Fe,Si), with a thickness of approximately 0.4 mm. This layered La... 0.84 Ce 0.36 Fe 13.68 Si 1.6 The Fe magnetic refrigeration composite material retains its complete shape after being filled with hydrogen. The preparation process and physical properties are shown in Table 1.

[0087] Example 5:

[0088] The general chemical formula of the La-Fe-Si based magnetic refrigeration material in this embodiment is: La 0.84 Ce 0.36 Fe 13.68 Si 1.6 H z / Fe.

[0089] In this embodiment, La 0.84 Ce 0.36 Fe 13.68 Si 1.6 H z The preparation method of the Fe magnetic refrigeration composite material is different from that of Example 2 above, except that the mass of the mixed powder monolayer and the mass of the Fe powder monolayer are different in step 3). Specifically, the mass of the mixed powder monolayer in step 3) is 2.4g and the mass of the Fe powder monolayer is 0.6g.

[0090] The sample consists of alternating layers of a first constituent layer and a second constituent layer. The first constituent layer comprises a magnetocaloric phase, porosity, and a non-magnetocaloric phase, with the porosity comprising approximately 12.8% by volume. The magnetocaloric phase is NaZn. 13 La(Fe,Si) crystal structure 13 The base compound consists of interconnected magnetocaloric phases forming a monolithic structure, with the magnetocaloric phase comprising approximately 70.9% by volume. The non-magnetocaloric phase is primarily composed of α-(Fe,Si) and La-Ce-rich rare earth alloys, with the α-(Fe,Si) phase comprising approximately 15.9% by volume. Fine non-magnetocaloric phase particles are dispersed within the magnetocaloric phase. The second constituent layer is mainly α-(Fe,Si), with a thickness of approximately 0.6 mm. This layered La... 0.84 Ce 0.36 Fe 13.68 Si 1.6 The Fe magnetic refrigeration composite material retains its complete shape after being filled with hydrogen. The preparation process and physical properties are shown in Table 1.

[0091] In step 1) of the preparation method of the above embodiments, Ce can be completely or partially replaced by one or both of Pr and Nd; in addition, in step 1) of the preparation method, the ingredients can also be prepared according to the chemical formula La. 1-x R x (Fe 1-a M a ) (13-y)b Si y A z Ingredients: R is selected from any one or more combinations of Ce, Pr and Nd; M is selected from any one or more combinations of Cr, Mn, Co, Ni and Al; A is selected from any one or more combinations of B and C; 0≤x≤0.5, 1≤y≤2, 0≤z≤0.5, 0≤a≤0.1, 0.5≤b≤1.5;

[0092] Furthermore, in step 3) of the preparation method described in the above embodiments, Fe powder can also be replaced by Fe alloy powder, which is a binary or multi-element alloy powder composed of Fe and elements such as Cr, Mn, Co, Ni, Al, B, C, and Si. The pressing method is not limited to molding, and the pressing temperature is not limited to room temperature, as long as the powder can be densified and formed.

[0093] In the above embodiments, in step 5), the composite material is cut into plates of different shapes for hydrogen filling, with a cross-sectional area of ​​4–130 mm². 2 The thickness is 1-2mm, and other sizes can be selected according to actual needs.

[0094] Table 1 Alloy composition, preparation process and physical properties of La-Fe-Si / Fe-based magnetic refrigeration composite materials

[0095]

Claims

1. A La-Fe-Si based magnetic refrigeration composite material, characterized in that, The La-Fe-Si-based magnetic refrigeration composite material is a layered structure prepared by alternately stacking and pressing a first component layer and a second component layer, the first component layer contains pores and a plurality of magnetic-thermal-phase units, each magnetic-thermal-phase is connected to form an integrated structure, the second component layer contains Fe or Fe alloy, the magnetic-thermal-phase is a La(Fe,Si) compound with a NaZn 13 13 crystal structure 13 The preparation method of the La-Fe-Si-based magnetic refrigeration composite material comprises the following steps in sequence: 1) according to R x Fe 13-y Si y Chemical formula configuration raw materials; wherein, R is La; or, R is selected from any one or two of Ce, Pr, Nd elements and combinations of two or more and La, x satisfies: 1≤x≤7, y satisfies: 1≤y≤10; 2) melt the raw materials configured in step 1) to form R x Fe 13-y Si y alloy, and then crush the alloy into powder; 3) crushing the R x Fe 13-y Si y alloy powder as an intermediate, together with Fe powder and Si powder; or, together with Fe powder, Si powder and alloy powder, respectively, according to R x (Fe 1-a M a ) (13-y)b Si y A z a mixed powder of the chemical formula, wherein the alloy powder is a binary or multi-alloy powder of Fe and Cr, Mn, Co, Ni, Al, B, C, Si elements; R is La; or R is selected from any one or two or more combinations of Ce, Pr, Nd elements and La; M is selected from any one or two or more combinations of Cr, Mn, Co, Ni, Al elements; A is selected from one or two combinations of B and C, x satisfies: 0.8≤x≤1.2, y satisfies: 1≤y≤2, z satisfies: 0≤z≤0.5, a satisfies: 0≤a≤0.1, b satisfies: 0.5≤b≤1.

5. 4) mixing the R x (Fe 1-a M a ) (13-y)b Si y A z The alloy powder is alternately laid as a first component layer with Fe or Fe alloy powder as a second component layer, and then pressed into a green body after laying. The Fe alloy powder is a binary or multi-element alloy powder of Fe and Cr, Mn, Co, Ni, Al, B, C, Si elements. 5) annealing the compact pressed in step 4) to obtain a phase having a NaZn 13 type crystal structure; 6) hydrogenating the blank annealed in step 5) to form the La-Fe-Si-based room-temperature magnetic refrigeration composite material.

2. The La-Fe-Si based magnetic refrigeration composite material of claim 1, wherein: The NaZn 13 La(Fe,Si) 13 The chemical general formula of the La(Fe,Si) 1-x R x (Fe 1-a M a ) 13-y Si y A z ; wherein R is selected from any one or a combination of two or more of Ce, Pr and Nd elements; M is selected from any one or a combination of two or more of Cr, Mn, Co, Ni and Al elements; A is H; or A is selected from one or a combination of two or more of B and C elements and H; x satisfies: 0<=x<=0.5, y satisfies: 1<=y<=2, z satisfies: 0.1<=z<=3, and a satisfies: 0<=a<=0.

1.

3. The La-Fe-Si based magnetic refrigeration composite material of claim 1, wherein: The content e of the first constituent layer in the La-Fe-Si-based magnetic refrigeration composite material satisfies: 60wt.% < e < 100wt.% according to the mass percentage, and the content f of the second constituent layer in the La-Fe-Si-based magnetic refrigeration composite material satisfies: 0 < f < 40wt.%.

4. The La-Fe-Si based magnetic refrigeration composite material of claim 3, wherein: The first constituent layer further comprises a non-magnetocaloric phase, wherein the first constituent layer is composed of La(Fe,Si) 13 The first constituent layer further comprises a non-magnetocaloric phase, wherein the first constituent layer is composed of La(Fe,Si) 13 The first constituent layer further comprises a non-magnetocaloric phase, wherein the first constituent layer is composed of La(Fe,Si) 5. The La-Fe-Si based magnetic refrigeration composite material of claim 4, wherein: The Curie temperature range is 150K-350K, and the entropy change value under the change of 2T magnetic field is not less than 8J / kgK.

6. The La-Fe-Si based magnetic refrigeration composite material of claim 1, wherein: The difference Δλ between the thermal conductivity λ1 along the first direction and the thermal conductivity λ2 along the second direction of the La-Fe-Si-based magnetic refrigeration composite material satisfies: Δλ ≥ 2W / mK.

7. The La-Fe-Si based magnetic refrigeration composite material of any one of claims 1 to 6, wherein: The magnetic refrigeration composite material can be processed into a plate-shaped material with a thickness less than 2 mm and a cross-sectional area not less than 100 mm 2 .

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