SEBS / gd / SEBS composite material with large force magnetic multi-card effect temperature change at room temperature and preparation method thereof

Abstract

This invention discloses a SEBS / Gd / SEBS composite material exhibiting a strong magnetic docaloric effect temperature change at room temperature and its preparation method, relating to the field of solid-state refrigeration technology. The method includes preparing a thick SEBS polymer film; preparing Gd sheets to obtain a soft magnetic material layer; and placing the soft magnetic material layer between two SEBS polymer thick films, followed by hot pressing to obtain the SEBS / Gd / SEBS composite material. This invention combines the high thermal conductivity of metallic Gd with a thick SEBS polymer film. The resulting composite material exhibits a large mechanical-magnetic-thermal response near room temperature. Compared to a single elasto-thermal response, the mechanical-magnetic docaloric effect temperature change increases by 50%, and compared to a single magnetocaloric response, the mechanical-magnetic docaloric effect temperature change increases by 173%. Furthermore, the thermal conductivity time is shortened to 22% of the SEBS elasto-thermal effect, accelerating the refrigeration cycle.

Description

Technical Field

[0001] This invention relates to the field of solid-state refrigeration technology, specifically to a SEBS / Gd / SEBS composite material exhibiting a strong magnetic multicaloric effect temperature change at room temperature and its preparation method. Background Technology

[0002] The demand for refrigeration has increased dramatically with societal development. Statistics show that refrigeration equipment consumes approximately 20% of the world's electricity. Traditional refrigeration equipment relies on compressed steam, and the refrigerants used (such as hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs)) have high global warming potential (GWP), severely impacting the environment. The search for new refrigeration technologies is therefore urgent, and solid-state refrigeration technology, with its advantages of being environmentally friendly, emitting no greenhouse gases, highly efficient, and energy-saving, has attracted widespread attention.

[0003] Solid-state refrigeration effects mainly include magnetic card refrigeration, electrocard refrigeration, and mechanical thermal refrigeration (such as spring-loaded and pressure-loaded refrigeration), which induce reversible temperature changes in materials through external magnetic, electric, and force fields, respectively. However, the thermal response of current solid-state refrigeration devices is not high enough to meet the needs of widespread practical applications. To enhance the thermal response of solid-state refrigeration devices, one approach is to apply multiple external fields simultaneously to the material, resulting in a superposition of multiple thermal effects for better cooling—this is known as multi-calorie effect refrigeration. Multi-calorie effects mainly include force-electric multi-calorie effects, magnetic-electric multi-calorie effects, and force-magnetic multi-calorie effects. However, compared to single thermal effects, research on multi-calorie effects is relatively lacking, hindering the development of solid-state refrigeration technology. In the force-electric multi-calorie effect, an electric field is applied to the electrode to excite the material and generate an electrocardie effect. However, the deformation of the material during the application of force can easily affect the stability of the material electrodes, thus limiting the practical application prospects of the force-electric multi-calorie effect. Compared to the magnetic-electric multicalorie effect, the force-magnetic multicalorie effect is more likely to achieve a larger response near room temperature, making it a promising multicalorie refrigeration method.

[0004] Currently, research on the force-magnetic multicalorie effect mainly focuses on metallic materials. Achieving a large force-magnetic multicalorie effect in metallic materials requires applying significant forces and magnetic fields, necessitating complex equipment. Furthermore, metals inevitably experience fatigue after cyclic force loading, easily leading to refrigeration device failure. These factors limit the practical application of the force-magnetic multicalorie effect based on metallic materials. Polymers, however, can achieve a similar level of elasticity under relatively small force loading. Materials such as natural rubber (NR), polyvinylidene fluoride (PVDF), and styrene-ethylene-butene triblock copolymer (SEBS) have been shown to have large elastic responses at room temperature. However, due to their low thermal conductivity, polymers struggle to rapidly exchange heat with the external environment during refrigeration, limiting the cooling capacity of polymer-based refrigeration devices. Summary of the Invention

[0005] This invention aims to address the problems of low coefficient of performance (COP), easy material fatigue, and low cycle efficiency in existing force-magnetic multicalorie effect materials. It provides a method for preparing a SEBS / Gd / SEBS composite material with a strong magnetic multicalorie effect at room temperature. This invention combines a metal with high thermal conductivity with a polymer, achieving a large multicalorie temperature change response near room temperature, thus improving the COP. Furthermore, it enhances heat exchange performance and reduces heat loss during heat transfer.

[0006] The above-mentioned objective of the invention includes the following steps:

[0007] Step 1, preparing a SEBS polymer thick film, specifically includes:

[0008] 3-5 parts of montmorillonite, 5-10 parts of polypropylene, 20-30 parts of OBC granules and 100-120 parts of SEBS granules are mixed in an internal mixer to obtain modified SEBS granules.

[0009] Modified SEBS particles are weighed, mixed, ball-milled, sieved, and dried to obtain fine and uniform SEBS powder with a particle size range of 50-100 μm. The SEBS rubber powder is then evenly spread on a stainless steel plate and hot-pressed (at 130℃ and 5 MPa) to form a thick SEBS polymer film. Preferably, the thickness of the SEBS polymer film is 90-150 μm.

[0010] Repeat step 1 to obtain two SEBS polymer thick films of uniform thickness;

[0011] Step 2: Prepare Gd thin films. Cut 99wt.% Gd blocks into thin slices by wire cutting. Then, polish the surface with metallographic sandpaper of 400 grit, 800 grit, 1200 grit, 2000 grit and 3000 grit respectively, from smallest to largest. Use polishing paste of W5, W2.5, W1.0 and W0.25 to treat the surface to make the surface of Gd thin films smooth and uniform.

[0012] Tetraethyl orthosilicate and a coupling agent are sprayed onto a Gd sheet to form a wet film, which is then dried under vacuum to form a thin film, resulting in a soft magnetic material layer. Preferably, the coupling agent is KH570, and the weight ratio of tetraethyl orthosilicate to the coupling agent is 9:1. Magnetocooling cycles require an aqueous solvent as a cooling medium, but metallic Gd exhibits poor corrosion resistance. Spraying with tetraethyl orthosilicate enhances the water resistance of the soft magnetic material and improves its acid and alkali resistance.

[0013] Step 3: Place the soft magnetic material layer between two SEBS polymer thick films, and hot-press for 3-7 minutes under a nitrogen atmosphere, at a hot-pressing temperature of 100-150℃ and a pressure of 0.3-1MPa to obtain the composite material.

[0014] Montmorillonite, a natural nanoscale filler, has an unstable layered structure that can generate organic mineral complexes, significantly improving the stability, mechanical properties, and durability of SEBS.

[0015] Polypropylene is a non-toxic, odorless, tasteless, milky-white, highly crystalline polymer that can improve the corrosion resistance, wear resistance, and mechanical properties of polymer layers.

[0016] Olefin block copolymers (OBCs) are polyolefin thermoplastic elastomers prepared by a new chain shuttle polymerization technology that involves continuous solution polymerization in a single reaction vessel. Due to their unique multi-block structure, they have a good balance between elasticity and temperature resistance; they have a high crystallization temperature and exhibit better elastic recovery and compression deformation at both room temperature and high temperature; and their wear resistance is also improved.

[0017] Polystyrene-ethylene-butene triblock copolymer (SEBS) is a linear triblock copolymer whose basic structure includes polystyrene (PS) as the end block, ethylene-butene copolymer (EB) obtained by hydrogenation of polybutadiene as the middle elastic block, and polystyrene (PS) at the other end. This structure allows SEBS to combine the characteristics of thermoplastics and the elastomer properties of rubber.

[0018] This invention combines a high thermal conductivity metal with a polymer to effectively improve thermal conductivity. Gd, as a typical room-temperature magnetocaloric material, exhibits a good magnetic card effect near room temperature. The SEBS / Gd / SEBS composite material, under simultaneous excitation by a force field and a magnetic field, exhibits a strong-magnetic multi-card effect near room temperature. Compared to a single elastic card response, the temperature change of the strong-magnetic multi-card effect increases by 50%, and compared to a single magnetic card response, the temperature change of the strong-magnetic multi-card effect increases by 173%, while the heat conduction time is shortened to 22% of the SEBS elastic card effect.

[0019] Furthermore, the present invention grinds the soft magnetic material layer into a circle in order to prevent the SEBS polymer thick film from being punctured by the sharp edges and corners during the stretching process of the composite material, thereby reducing the service life of the material in application. Then, a mixture of low infrared emissivity modified materials is sprayed onto the surface of the circular soft magnetic material layer.

[0020] In this process, 50 parts of carbon nanotubes, 20 parts of aluminum silver paste, and 20 parts of tin antimony oxide were mixed with 10 parts of water and stirred evenly to obtain a low infrared emissivity modified material mixture. The purpose of spraying the low infrared emissivity modified material mixture was to reduce the interference of Gd surface emissivity on the experiment and to unify the emissivity of all composite materials using thermocouples and infrared cameras.

[0021] Meanwhile, stainless steel layers are provided on the two SEBS polymer thick films, with a steel sheet removed from the center of the stainless steel layer. During hot pressing, the two SEBS polymer thick films come into contact with each other, and a soft magnetic material layer is located between the two SEBS polymer thick film layers.

[0022] Preferably, the length of the steel sheet removed from the center of the stainless steel layer is 1.2-1.5 times the length of the soft magnetic material layer. This leaves sufficient space to prevent the soft magnetic material layer from deforming due to stress during hot pressing.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] The nanofiller is uniformly distributed in the physically cross-linked modified SEBS three-dimensional mesh structure. The fillers are interconnected and arranged in an interlaced manner, which increases the packing density of the fillers and forms numerous heat conduction paths, thus accelerating the heat transfer.

[0025] A SEBS / Gd / SEBS composite material with a strong magnetic multicaloric effect temperature change at room temperature and its preparation method. This invention combines high thermal conductivity metal Gd with a thick film of SEBS polymer. The resulting composite material has a large force-magnetic multicaloric response near room temperature and has the advantage of rapid thermal conduction compared to polymer refrigeration.

[0026] Pre-treating Gd flakes by spraying tetraethyl orthosilicate and coupling agent onto them can prevent Gd oxidation, which not only increases the number of refrigeration cycles of the composite material but also broadens its application scenarios.

[0027] Furthermore, the preparation process of this invention is simple, low-cost, and has excellent performance, showing great application potential. Attached Figure Description

[0028] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 This is a flowchart illustrating the preparation method of SEBS / Gd / SEBS composite materials.

[0030] Figure 2 Schematic diagram and physical image of SEBS / Gd / SEBS composite material;

[0031] Figure 3 The time-domain curves of the magnetic card effect temperature change of the SEBS / Gd / SEBS composite material prepared in Example 1 at a test temperature of 20℃ and a magnetic field strength of 0.52T, and the comparison diagram of finite element simulation; wherein, ΔT M-1 For the maximum temperature change of the magnetic card, ΔT M-2 M-On indicates the application of a magnetic field, and M-Off indicates the removal of the magnetic field;

[0032] Figure 4 The time-domain curves of the temperature change of the elastic-carbide effect of the SEBS / Gd / SEBS composite material prepared in Example 1 at a test temperature of 20°C and a strain of 300%, and the comparison diagram of finite element simulation; wherein, ΔT Ela-1 For the maximum temperature change of the bombardier, ΔT Ela-2 For maximum spring cooling temperature change, Ela-On represents strain application, and Ela-Off represents strain removal;

[0033] Figure 5 The time-domain curves (300% strain, 0.52T magnetic field) of the multicaloric effect temperature change of the SEBS / Gd / SEBS composite material prepared in Example 1 at an ambient temperature of 20°C, and finite element simulations, are also presented. Figure 5 (a) Temperature change in thermal effect response when alternating magnetic field and strain are applied; Figure 5 (b) represents the thermal effect response temperature change when a magnetic field and strain are applied simultaneously; where ΔT M&Ela-1 For the maximum multicalorie heating temperature change, ΔT M&Ela-2For maximum multicalorie cooling temperature change, M&Ela-On applies magnetic field and strain simultaneously, while M&Ela-Off removes magnetic field and strain simultaneously.

[0034] Figure 6 The graph shows a comparison of the maximum temperature change due to magnetic card effect of the composite material prepared in Example 1 under different soft magnetic material layer thicknesses at a test temperature of 20°C and a magnetic field strength of 0.52T.

[0035] Figure 7 Comparison of heat conduction time (ΔT) between composite material and SEBS during the elastic-kneading effect under the same strain (300%). R-2 ΔT represents the temperature difference that the composite material recovers from its lowest temperature. Ela-2 (This refers to the maximum temperature change value of the composite material during cooling).

[0036] Figure 8 A schematic diagram of the force-magnetic multicaloric effect refrigeration cycle for SEBS / Gd / SEBS composite materials. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. However, this does not limit the invention to the scope of the embodiments described. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0038] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] Example 1

[0040] A SEBS / Gd / SEBS composite material exhibiting strong magnetic docaloric effect temperature change at room temperature and its preparation method, such as Figure 1 As shown, it includes the following steps;

[0041] Step 1: Prepare a SEBS polymer thick film;

[0042] Step 1-1: Dry the natural nano-sized filler montmorillonite in a forced-air drying oven (105±5℃) to constant weight. Weigh out 3 parts of nano-sized montmorillonite, 6 parts of polypropylene, 20 parts of OBC particles and 100 parts of SEBS particles and mix them evenly to obtain a blend. Place the blend in the Brad mixing chamber (150-200℃) and mix for 7 minutes to obtain modified SEBS particles.

[0043] Steps 1-2 involve weighing, mixing, ball milling, sieving, and drying the modified SEBS particles to obtain SEBS rubber powder with a particle size range of 50-100 μm. The SEBS rubber powder is then evenly spread on a stainless steel plate and hot-pressed into a film in a hot press to obtain a SEBS polymer thick film with a thickness of 90-150 μm. The hot-pressing conditions are as follows: inert nitrogen atmosphere, hot-pressing temperature 150-200℃, hot-pressing time 5-15 min, and pressure 1-5 MPa.

[0044] Repeat steps 1-1 and 1-2 to obtain two SEBS polymer thick films.

[0045] Step 2: Prepare Gd thin films to obtain a soft magnetic material layer;

[0046] Step 2-1: The 99wt.% Gd block is wire-cut into slices. The surface of the Gd slices is polished with metallographic sandpaper of 400 grit, 800 grit, 1200 grit, 2000 grit and 3000 grit, respectively, from smallest to largest, to make the surface of the Gd slices flat and uniform. Tetraethyl orthosilicate and coupling agent KH570 are uniformly sprayed on the surface of the Gd slices in a weight ratio of 9:1 to form a wet film. After vacuum drying, a thin film is formed to obtain a soft magnetic material layer.

[0047] Step 2-2: Grind the edges of the soft magnetic material layer with 400-grit sandpaper to form a circle with a radius of 0.5 cm. Then, spray a low-infrared emissivity modified material mixture onto the circular soft magnetic material layer. The mixture consists of 50 parts by weight of carbon nanotubes, 20 parts of aluminum silver paste, 20 parts of tin antimony oxide, and 10 parts of water. After thorough mixing, the low-infrared emissivity modified material mixture is obtained.

[0048] Step 3: Place the soft magnetic material layer between two SEBS polymer thick films and hot press to obtain the composite material.

[0049] Step 3-1: The stainless steel plate is treated with sandblasting and shot blasting to increase its surface roughness, and a 1.5×1.5cm section is removed from the center of the stainless steel plate. 2 Square steel sheets of various sizes;

[0050] Step 3-2: Two SEBS polymer thick films are respectively adhered tightly to the surface of the treated stainless steel plate. A circular soft magnetic material layer and one SEBS polymer thick film are then placed sequentially on top of the other SEBS polymer thick film, with the soft magnetic material layer positioned between the two SEBS polymer thick films and at the center of each film. The composite material is then obtained through hot pressing. Figure 2 As shown in the figure. The thickness of the composite material is 400-600μm; the hot pressing conditions are set as follows: inert gas nitrogen atmosphere, hot pressing temperature 100-150℃, hot pressing time 3-7min, and pressure 0.3-0.8MPa.

[0051] (1) Magnetic Card Effect Cyclic Experiment

[0052] The composite material prepared in Example 1 was subjected to three magnetic card effect cycles at a test temperature of 20℃ and a magnetic field strength of 0.52T. The resulting temperature change-time curves are shown below. Figure 3 As shown by the solid line in the middle.

[0053] Figure 3 In the middle, ΔT M-1 With ΔT M-2 These represent the magnitudes of temperature changes during the heating and cooling phases of the magnetic card effect on the material, respectively, and in the three cyclic experiments of the magnetic card effect, ΔT M-1 With ΔT M-2 Almost equal.

[0054] First, we demonstrate that the SEBS / Gd / SEBS composite material prepared in Example 1 exhibits a magnetic card effect. A magnetic field (0.52T) with a period of 120s was applied to the SEBS / Gd / SEBS composite material, and the temperature change caused by the magnetic card effect was directly characterized using an infrared camera. When the magnetic field was applied to the SEBS / Gd / SEBS composite material (M-On), the magnetic domains inside the material changed from a randomly distributed disordered state to an ordered state that was as close as possible to the direction of the magnetic field. This process reduced the magnetization-related entropy, leading to an increase in the composite material's temperature. Then, due to heat conduction between the SEBS / Gd / SEBS composite material and the environment, the temperature of the SEBS / Gd / SEBS composite material gradually decreased to the ambient temperature (ΔT = 0℃). After the magnetic field was removed (M-Off), the magnetic domains inside the material returned to their initial state, and the internal magnetization-related entropy increased, causing the SEBS / Gd / SEBS composite material to cool down immediately. Subsequently, it absorbed heat from the outside, and the temperature of the SEBS / Gd / SEBS composite material gradually returned to its initial state, completing the entire magnetic card cooling cycle.

[0055] Meanwhile, to further verify the reliability of the direct characterization results, we also performed a finite element simulation of the heat transfer process caused by the magnetic card effect. The simulated temperature change time-domain curves are shown below. Figure 3 As shown by the dashed line, the results agree well with the experimental results, indicating that the characterization of the magnetic card effect of the SEBS / Gd / SEBS composite material prepared in Example 1 is reliable.

[0056] (2) Cyclic Experiment of the Spin-Card Effect

[0057] The composite material prepared in Example 1 was subjected to three cyclic tests of the spring-carrier effect at a test temperature of 20°C and a strain of 300%. The resulting temperature-time curves are shown below. Figure 4 As shown by the solid line in the middle.

[0058] Figure 4 In the middle, ΔT Ela-1 For the maximum temperature change due to the spring effect, ΔT Ela-2 To achieve the maximum cooling temperature change due to the elastic effect, the strain remains stable during the cycling process. Therefore, the composite material prepared in Example 1 has good elasticity and reversibility.

[0059] The SEBS / Gd / SEBS composite material prepared in Example 1 demonstrates the presence of an elastic-clamping effect. By fixing one end of the composite material and applying a horizontal uniaxial tension to the other end, the composite material is subjected to tensile strain (Ela-On), causing deformation. During this process, the temperature of the composite material significantly increases due to the elastic-clamping effect. When the strain is removed (Ela-Off), the composite material returns to its initial state, accompanied by a decrease in temperature. This process is mainly due to the reversible conformational change of the SEBS molecular chains under strain. During stretching, the material undergoes a conformational transformation, resulting in a decrease in conformational entropy and thus an increase in composite temperature. When the strain is removed, the composite material returns to its initial shape, the internal conformational entropy increases, and the temperature decreases. The magnitude of the elastic-clamping effect is directly related to the strain applied to the composite material and increases proportionally.

[0060] Meanwhile, to further verify the reliability of the direct characterization results, a finite element simulation of the heat transfer process caused by the spring-loaded effect was performed. The simulated temperature change time-domain curves are shown below. Figure 4 The results, as shown by the dashed line, agree well with the experimental curves, indicating that the characterization of the elastic-caking effect of the SEBS / Gd / SEBS composite material is reliable.

[0061] (3) Force-magnetic docal effect cyclic experiment

[0062] The composite material prepared in Example 1 was subjected to environmental temperature, strain of 300%, and magnetic field strength of 0.52T. The temperature change of the composite material was monitored when tensile force and magnetic field were applied simultaneously or alternately. Figure 5 ,in, Figure 5 (a) Temperature change in thermal effect response when alternating magnetic field and strain are applied; Figure 5 (b) is the temperature change in response to the thermal effect when a magnetic field and strain are applied simultaneously.

[0063] To verify that the SEBS / Gd / SEBS composite material prepared in Example 1 exhibits the force-magnetic Docalorie effect, a periodic magnetic field and strain were applied to the SEBS / Gd / SEBS composite material prepared in Example 1, and its temperature change was studied. The results are as follows: Figure 5 As shown. First, the cases where the magnetic field and strain are applied and removed sequentially are studied, such as... Figure 5 As shown in (a), a 300% strain was applied at 7s, a magnetic field of 0.52T was applied at 97s, the strain was unloaded at 187s, and the magnetic field was removed at 277s. It can be observed that when a single physical field is applied, the temperature of the composite material increases regardless of whether it is strain or magnetic field; while when the physical field is removed, the temperature of the composite material decreases, indicating that the SEBS / Gd / SEBS composite material can simultaneously exhibit both elastic and magnetic effects, possessing the characteristics of a multi-electromagnetic effect. Figure 5 (a) Showing the maximum thermostatic change ΔT of the spring after strain application. Ela-1 The maximum temperature change ΔT when the strain is removed is 2.04℃. Ela-2 The maximum temperature change ΔT of the magnetic card after applying a magnetic field is 2.03℃. M-1 The maximum temperature change ΔT is 1.09℃ when the magnetic field is removed. M-2 The result is 1.08℃. This result is similar to the temperature change of the composite material described in the previous characterization of the single magnetic card effect and the spring card effect, indicating that the composite material has little mutual influence when two external fields are applied alternately. Furthermore, the finite element simulation results are in good agreement with the experimental results.

[0064] Simultaneously applying a magnetic field and strain of the same magnitude as the unloading, the temperature change of the composite material under the mechanomagnetic Docal effect was studied, and the results are as follows: Figure 5 As shown in (b), the maximum thermal rise temperature change ΔT of the composite material can be observed. M&Ela-1 The maximum thermal drop temperature change ΔT is 2.97℃. M&Ela-2 The temperature change of the thermal effect of SEBS / Gd / SEBS is 3.01℃. Compared with the single thermal effect, the thermal effect temperature change of SEBS / Gd / SEBS is significantly improved, indicating that the force-magnetic multicalorie effect can significantly improve the thermal effect temperature change of the material. Figure 5 The infrared temperature distribution map in (b) shows that the force-magnetic multicaloric response is significantly stronger than that of the single thermal effect, indicating that the force-magnetic multicaloric effect can be greatly enhanced by simultaneously exciting the material with force and magnetic field. Furthermore, by comparing the relaxation times of the heating and cooling portions during the thermal response of the composite material, it was found that the heating and cooling temperature relaxation times of the multicaloric effect are 55s and 52s, respectively, which are lower than those of the corresponding single magnetic effect. Figure 3 ) and the single ejection effect ( Figure 4The sum of the relaxation times of the single thermal effect of heating is 76s, and the sum of the relaxation times of the single thermal effect of cooling is 73s. Therefore, the SEBS / Gd / SEBS composite material not only exhibits a mechanomagnetic docaloric effect near room temperature, improving its thermal effect response, but also accelerates the heat exchange rate.

[0065] Example 2

[0066] Based on Example 1, the Gd block from Example 1 was sliced ​​and polished to thicknesses of 100μm, 200μm, 300μm, 400μm and 500μm, respectively, and the composite material thicknesses were 400μm, 450μm, 500μm, 550μm and 600μm, respectively.

[0067] At a test temperature of 293.15℃ and a magnetic field strength of 0.52T, composite materials with soft magnetic material layers of different thicknesses were subjected to a cooling experiment, yielding the following results: Figure 6 The graph shows a comparison of the cooling curves of composite materials obtained from soft magnetic material layers of different thicknesses. Figure 6 It can be seen that, at a test temperature of 20℃ and a magnetic field strength of 0.52T, the demagnetization temperature change ΔT is [value missing] when the thickness of the soft magnetic material layer is 100μm, 200μm, 300μm, 400μm, and 500μm. M-2 The demagnetization temperature change ΔT is 0.61℃, 0.72℃, 1.10℃, 0.97℃, and 1.12℃, respectively, when the thickness of the soft magnetic material layer is 500μm. M-2 The maximum temperature is 1.12℃.

[0068] Therefore, the composite material prepared by this invention can achieve the magnetic card effect, the spring card effect, and the force-magnetic multi-card effect near room temperature through the synergistic effect of force and magnetic fields. The multi-card effect is particularly significant. When only 300% strain and 0.52T magnetic field are applied, the maximum temperature drop reaches 3.01℃, which is 174% and 50% higher than the magnetic card effect and the spring card effect, respectively. Furthermore, the self-made bonding method significantly improves the heat exchange capacity of the material's multi-card effect and accelerates the refrigeration cycle.

[0069] Example 3

[0070] Based on the above embodiments, the heat transfer rates of the composite material prepared in Example 1 and the SEBS material in a single elastic-carbide effect response were compared, such as... Figure 7 As shown. The vertical axis represents the heat conduction time ΔT corresponding to each stage of the composite material's temperature recovery from its lowest value to ambient temperature after strain removal. R-2 The value of the recovered temperature, ΔT Ela-2 This represents the maximum temperature change during cooling (i.e., the maximum temperature change during recovery). From... Figure 7It is evident that the composite material has a faster heat exchange with the external environment, and the heat conduction time required by the composite material is significantly shorter than that of SEBS, especially under large temperature changes (ΔT). R-2 / ΔT Ela-2 =100%), the heat exchange time required by SEBS reached 32s, while that of the composite material was only 7s, which is reduced to 22% of that of SEBS, greatly reducing the thermal effect cycle time.

[0071] Therefore, the composite material prepared by this invention can complete more refrigeration cycles in a limited time, thereby effectively improving the refrigeration capacity of the device.

[0072] Example 4

[0073] Based on the above embodiments, the conceptual refrigeration process of the composite material prepared by the present invention using the force-magnetic docal effect is as follows: Figure 8 As shown.

[0074] Step 1: Apply magnetic field and strain;

[0075] Simultaneously, a constant magnetic field and strain are applied to the composite material. The magnetic domains inside the composite material tend to align with the magnetic field direction, and the magnetization-related entropy decreases. At the same time, due to the strain, the composite material is stretched and undergoes a conformational transformation, which causes a decrease in conformational entropy and leads to an increase in the temperature of the composite material.

[0076] Step 2, dissipate heat;

[0077] With the magnetic field and strain applied, the composite material exchanges heat with the environment, dissipating its heat into the environment. The composite material's temperature returns to ambient temperature, at which point the magnetization and strain remain unchanged.

[0078] Step 3: Remove the magnetic field and strain;

[0079] Simultaneously, the magnetic field and strain applied to the composite material are removed, and the shape and magnetization of the composite material are restored to the state before step ①. The internal magnetization-related entropy and conformational entropy increase, causing the temperature of the composite material to drop below the ambient temperature, and the size to return to the initial state.

[0080] Step 4, absorb heat;

[0081] At this point, the composite material comes into contact with the object being cooled, absorbing heat from it and thus cooling the object. The temperature of the composite material gradually returns to its initial temperature. This completes the entire force-magnetic multicalorie refrigeration cycle.

[0082] Depend on Figure 8It is evident that the composite material prepared by this invention can achieve a good cooling effect without applying a high physical field, and the cooling effect is fast with better thermal conductivity. This not only saves costs but also expands the range of applications.

[0083] The above description is merely some specific embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a SEBS / Gd / SEBS composite material exhibiting a strong magnetic docaloric effect temperature change at room temperature, characterized in that, Includes the following steps: Preparation of SEBS polymer thick films; Gd thin films were prepared to obtain a soft magnetic material layer; A soft magnetic material layer is placed between two SEBS polymer thick films and hot-pressed to obtain a composite material. The preparation of SEBS polymer thick films specifically includes: Modified SEBS particles were obtained by mixing montmorillonite, polypropylene, olefin block copolymer and SEBS particles in an internal mixer. Modified SEBS particles were ball-milled into modified SEBS powder; Modified SEBS powder was hot-pressed to obtain a thick SEBS polymer film; The preparation of Gd thin films to obtain soft magnetic material layers specifically includes: The Gd block was cut into thin slices by wire cutting to obtain Gd thin films; Tetraethyl orthosilicate and a coupling agent are sprayed onto the surface of a Gd sheet to form a wet film, and then a soft magnetic material layer is obtained by vacuum drying.

2. The method for preparing a SEBS / Gd / SEBS composite material exhibiting a strong magnetic docaloric effect temperature change at room temperature according to claim 1, characterized in that, The soft magnetic material layer is polished into a circle, and a mixture of low infrared emissivity modified materials is sprayed onto the circular soft magnetic material layer.

3. The method for preparing a SEBS / Gd / SEBS composite material exhibiting a strong magnetic docaloric effect temperature change at room temperature according to claim 2, characterized in that, Carbon nanotubes, aluminum silver paste, and tin antimony oxide were mixed with water and stirred until homogeneous to obtain a low infrared emissivity modified material mixture.

4. The method for preparing a SEBS / Gd / SEBS composite material exhibiting a strong magnetic docaloric effect temperature change at room temperature according to claim 1, characterized in that, The weight parts of montmorillonite, polypropylene, olefin block copolymer particles and SEBS particles are 3-5 parts, 5-10 parts, 20-30 parts and 100-120 parts respectively.

5. The method for preparing a SEBS / Gd / SEBS composite material exhibiting a strong magnetic docaloric effect temperature change at room temperature according to claim 1, characterized in that, The thickness of the composite material is 400-600 μm.

6. The method for preparing a SEBS / Gd / SEBS composite material exhibiting a strong magnetic docaloric effect temperature change at room temperature according to claim 1, characterized in that, The thickness of SEBS polymer thick films ranges from 90 to 150 μm.

7. The method for preparing a SEBS / Gd / SEBS composite material exhibiting a strong magnetic docaloric effect temperature change at room temperature according to claim 1, characterized in that, A soft magnetic material layer is placed between two SEBS polymer thick films, and the composite material is obtained by hot pressing for 3-7 minutes under a nitrogen atmosphere, at a hot pressing temperature of 100-150°C and a pressure of 0.3-1MPa.

8. The SEBS / Gd / SEBS composite material prepared by any one of the preparation methods according to claims 1-7.

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