Magnetic refrigeration material with wide working temperature range as well as preparation method and application of magnetic refrigeration material

Abstract

The invention discloses a magnetic refrigeration material with a wide working temperature range and a preparation method and application thereof, the magnetic refrigeration material is a wrinkled alloy film with a non-uniform strain gradient, the wrinkled alloy film with the non-uniform strain gradient is obtained by transferring the alloy film, and the magnetic refrigeration material has an extremely wide working temperature range. By utilizing different expansion coefficients and weak Van der Waals interaction between the alloy film and the NaCl substrate, the film presents the self-supporting wrinkle morphology on the substrate, the preparation process of the film with the wrinkle morphology is simple and convenient, and the film with the wrinkle morphology can be conveniently separated from the substrate while the wrinkle morphology is reserved so as to obtain the wrinkle film. After the non-uniform strain gradient is introduced, the saturation magnetization intensity of the wrinkled thin film in the wide temperature range is remarkably improved compared with a block alloy and a flat thin film. Meanwhile, a magnetic entropy change result shows that the wrinkled thin film has an extremely wide working temperature range as a magnetic refrigeration material, and the magnetic refrigeration capacity of the wrinkled thin film is far higher than that of a block alloy and a flat thin film.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a magnetic refrigeration material with a wide operating temperature range, and a preparation method and application thereof. Background Art

[0002] The pulsed laser deposition system uses high-energy, high-density pulsed lasers as the excitation source. Through the focusing system, the surface of the solid target material is dissolved inside the vacuum chamber, from which the plasma plume is excited. The plasma plume is then transported directionally to the target substrate surface. The plasma in the plume is then rapidly cooled and finally connected to form a film on the substrate surface. The film obtained has uniform thickness and its composition is highly consistent with that of the target material, which is conducive to the preparation of multi-component compounds. At the same time, the coating process is pollution-free and easy to control, and the geometric parameters, laser parameters, substrate conditions and reaction atmosphere can be flexibly adjusted to obtain high-quality films.

[0003] Due to the size effect and the hard substrate constraint, the phase transition of magnetoresistive alloy films with a thickness of less than tens of nanometers is suppressed, which seriously affects many of its phase transition-related magnetic response effects. It is worth noting that through the decoupling between the film and the substrate, that is, the self-supporting alloy film with high degrees of freedom and surface-to-volume ratio, its functionality can be expanded by designing complex strain geometries. Currently, there are two typical problems in the field of magnetoresistive cooling: (1) limited operating temperature window; (2) large transition hysteresis.

[0004] The prior art (CN 117127202 A) discloses a catalyst utilizing strain gradient to induce magnetic enhancement and magnetic field response and a preparation method thereof, wherein an alloy film having a wrinkled morphology with a strain gradient is obtained by constraining the alloy film. However, the wrinkled film can only be used as a catalyst for hydrogen and oxygen evolution reactions. Summary of the invention

[0005] Purpose of the invention: In view of the problems existing in the prior art, the present invention proposes to provide a magnetic refrigeration material with a wide operating temperature range. The material has small hysteresis, wide operating temperature range and high cooling capacity, which effectively solves the bottleneck problem in the current magnetic refrigeration field.

[0006] The invention also provides a preparation method and application of the magnetic refrigeration material with a wide operating temperature range.

[0007] Technical solution: In order to achieve the above-mentioned purpose, the present invention provides a magnetocaloric material with a wide operating temperature range, wherein the magnetocaloric material is a wrinkled alloy film with a non-uniform strain gradient.

[0008] The magnetocaloric material is a wrinkled alloy film with a non-uniform strain gradient obtained by transferring an alloy film, and as a magnetocaloric material, it has an extremely wide working temperature range.

[0009] Wherein, the thickness of the alloy film is 20nm-50nm.

[0010] Wherein, the alloy film comprises a multi-component Heusler alloy.

[0011] Preferably, the alloy film is a Ni-Mn-Sn alloy film.

[0012] The method for preparing the magnetic refrigeration material with a wide operating temperature range of the present invention comprises the following steps:

[0013] (1) depositing an alloy film on a NaCl single crystal substrate;

[0014] (2) in-situ annealing after depositing the alloy film, followed by cooling to room temperature;

[0015] (3) Using low-temperature tape to transfer the film on the NaCl substrate can obtain a wrinkled film with non-uniform strain gradient.

[0016] Wherein, the temperature for depositing the metal film on the substrate in step (1) is 400° C.-450° C., and the method for depositing the alloy film on the NaCl single crystal substrate is pulsed laser deposition or laser-assisted molecular beam epitaxy.

[0017] Wherein, in step (2), the annealing temperature is 450°C-500°C, and the annealing time is 0.5h-1h.

[0018] Wherein, the annealing and cooling in step (2) need to be performed in a high vacuum environment of the cavity.

[0019] The magnetic refrigeration material of the present invention is used in preparing a magnetic refrigeration material with a wide working temperature range, small transformation hysteresis and high refrigeration capacity.

[0020] The magnetocaloric material with a wide operating temperature range described in the present invention is used as a refrigerant in refrigeration equipment, electronic equipment heat dissipation, precision instruments, aerospace, medical cold chain and low-temperature storage.

[0021] The invention discloses a magnetocaloric material with a wide operating temperature range, which is induced by non-uniform strain gradient. The alloy target is deposited on the surface of a NaCl substrate to form a connected and uniform film by pulsed laser deposition technology at a certain growth temperature. During the process of in-situ annealing of the film and cooling to room temperature, the film presents a self-supporting wrinkled morphology on the substrate due to the different expansion coefficients and weak van der Waals interaction between the NaCl substrate and the film. A wrinkled film with a non-uniform strain gradient can be obtained by transferring the film on the NaCl substrate using a low-temperature glue. After the geometric strain is introduced into the wrinkled film, the magnetization intensity of the wrinkled film is significantly improved compared with the bulk alloy and the flat alloy film grown on the hard substrate, and the magnetic entropy change measurement results show that the wrinkled film has an extremely wide operating temperature range.

[0022] The refrigeration material described in the present invention is an alloy film with a wrinkled morphology with a non-uniform strain gradient. Due to the different expansion coefficients and weak van der Waals interactions between the alloy film and the NaCl substrate, the film presents a self-supporting wrinkled morphology on the substrate, and the film preparation process with a wrinkled morphology is simple, and it can be easily separated from the substrate while retaining the wrinkled morphology to obtain a wrinkled film. After the introduction of the non-uniform strain gradient (i.e., flexural magnetism), a continuous phase change in the wrinkled film is induced, and the saturation magnetization intensity of the wrinkled film is significantly improved compared with that of the bulk alloy and the flat film (MgO substrate) in a wide temperature range, thereby resulting in a simultaneous increase in the magnetic entropy and lattice entropy in the film. At the same time, the magnetic entropy change results show that the wrinkled film has an extremely wide working temperature range as a magnetic cooling material, and the magnetic cooling capacity of the wrinkled film is much higher than that of the bulk alloy and the flat film (MgO substrate).

[0023] The present invention overcomes the long-standing obstacles of magnetic cooling alloys in wide temperature range magnetic cooling, namely limited operating temperature window and typical large transition hysteresis, by introducing non-uniform strain gradient. In order to overcome the shortcomings of the existing magnetic cooling alloy film operating temperature range, the present invention provides a preparation process for obtaining a wrinkled alloy film, and by introducing non-uniform strain gradient, the magnetic cooling operating temperature range and cooling capacity of the wrinkled film are broadened.

[0024] In the magnetocaloric material prepared by the present invention, in the Heusler alloy with non-uniform strain gradient, on the one hand, the non-uniform strain gradient induces the generation of continuous phase transition, and on the other hand, the flexural magnetism enhances the ferromagnetic moment, thereby leading to the simultaneous increase of magnetic entropy and lattice entropy, and finally leading to the formation of an extremely wide operating temperature range. At the same time, the material prepared by the present invention has a wide operating temperature range, small transformation hysteresis and high cooling capacity, and low-temperature glue transfer is used in the preparation process, which is more convenient.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0026] (1) The preparation process of the magnetic refrigeration material with a wide operating temperature range of the present invention is simple.

[0027] (2) The present invention is ingenious in that it introduces a non-uniform strain gradient into the film by using the difference in expansion coefficients between the substrate and the film and the transfer of a low-temperature tape.

[0028] (3) The magnetic refrigeration material prepared by the present invention has a wide operating temperature range, small transition hysteresis and high cooling capacity.

[0029] (4) For Ni-Mn based (Ni-Mn-X, X = In, Sb, Ga, and Al, etc.) Heusler alloys, the preparation process can be repeated. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the preparation process of a magnetic refrigeration material with a wide operating temperature range provided in an embodiment of the present invention.

[0031] Figure 2 This is an optical microscope image of the wrinkled film prepared in Example 1 of the present invention, and the inset is a schematic diagram of the strain gradient.

[0032] Figure 3 This is a scanning electron microscope image of the flat film (MgO substrate) prepared in Comparative Example 1 of the present invention.

[0033] Figure 4 These are the thermomagnetic curves of the alloy block, flat film (MgO substrate), and wrinkled film of the embodiment of the present invention under a magnetic field of 0.1 kilo-Oersted.

[0034] Figure 5 Magnetic hysteresis loops of the alloy block, flat film (MgO substrate), and wrinkled film at different temperatures according to the embodiment of the present invention.

[0035] Figure 6 Isothermal magnetization curves of bulk alloy, flat film (MgO substrate), and wrinkled film as magnetoresistance materials at 0 kilo-oersted to 50 kilo-oersted in the embodiments of the present invention.

[0036] Figure 7 The alloy block, flat film (MgO substrate) and wrinkled film in the embodiments of the present invention are used as magnetic cooling materials, and the magnetic entropy change values ​​and cooling capacity under different magnetic fields.

[0037] Figure 8 The performance comparison diagram of the present invention with other magnetic refrigeration materials is shown in FIG. 1 , with effective refrigeration capacity as the horizontal axis and transformation hysteresis and working temperature range as the vertical axis. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0039] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources. Experimental methods without specific conditions specified in the examples are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0040] NaCl single crystal substrate (1cm×1cm), MgO single crystal substrate, and Al2O3 single crystal substrate were purchased from CasCrysTech (Hangzhou) Technology Co., Ltd. (CasCrysTech, CCT), and SrTiO3 single crystal substrate was purchased from Hefei Single Crystal Material Technology Co., Ltd.

[0041] Ni, Mn and Sn are commercially available common metal single substances.

[0042] Low temperature tape is polyimide low temperature tape (Kapton, DuPont, -269~400℃)

[0043] In the embodiments of the present invention, the prepared materials were tested by the following method:

[0044] Measurement of thermomagnetic curves: A superconducting quantum interference device produced by Quantum Design, USA, was used to measure the thermomagnetic curves of the alloy block, flat film and wrinkled film respectively. The data recording of the thermomagnetic curves was divided into three parts. The sample was first cooled from 350K to 10K in zero field, and then the temperature was measured from 10K to 350K in the zero field cooling (ZFC) mode under a 0.1kOe magnetic field. Subsequently, the film was cooled to below 10K in a 0.1kOe magnetic field, and the data in the field cooled cooling (FCC) mode was recorded. After reaching 10K, the film was heated to 350K again in the same magnetic field, and the thermomagnetic curve data in the field cooled heating (FCH) mode was recorded.

[0045] Hysteresis loop measurement: The superconducting quantum interference device produced by Quantum Design Company in the United States was used to measure the hysteresis loops of the alloy bulk, flat film and wrinkled film respectively. The data recording of the hysteresis loop was divided into four parts, namely 50 kOe to 0 oested, 0 oested to -50 kOe, -50 kOe to 0 oested, and 0 oested to 50 kOe. In addition, before each measurement, the superconducting magnet was oscillated and demagnetized at 300K to ensure that there was no residual flux in the test film.

[0046] Measurement of magnetic entropy change: A superconducting quantum interference device produced by Quantum Design, USA, was used to measure the isothermal magnetization curves of the alloy bulk, flat film and wrinkled film from 20K to 340K, with a temperature interval of 20K. The data recording of the isothermal magnetization curve is divided into two parts: the magnetic field is from 0 Oersted to 50 kOersted, and then from 50 kOersted to 0 Oersted. In addition, the superconducting magnet is oscillated and demagnetized before each measurement to ensure that there is no residual magnetic flux in the test film.

[0047] Example 1

[0048] Embodiment 1 of the present invention provides a method for preparing a magnetic refrigeration material with a wide operating temperature range, the preparation method comprising the following steps:

[0049] 1) First, at a growth temperature of 450°C, a Ni-Mn-Sn alloy film was prepared on a NaCl single crystal substrate (1 cm×1 cm) using a pulsed laser deposition system, wherein the Ni-Mn-Sn element molar ratio was 2.0:1.5:0.5, and the film thickness could be controlled between 20 nm and 50 nm (controlled at 30 nm in this embodiment) according to different laser pulse numbers (5000-15000 pulses);

[0050] 2) Keep the substrate on which the alloy film is deposited at 500°C in a high vacuum environment (<1.0×10 -4 Pa) annealing for 0.5h;

[0051] 3) Turn off the temperature control switch, maintain a high vacuum environment, and wait for the alloy film to cool down to room temperature naturally, thereby forming a self-supporting wrinkle morphology.

[0052] 4) Use low-temperature adhesive to transfer the film on the NaCl substrate (bond the wrinkled film with one side facing down to a low-temperature tape with a polyimide adhesive layer, and then peel off the NaCl substrate to obtain the wrinkled film). A wrinkled film (1cm×1cm) with a non-uniform strain gradient can be obtained, and a magnetorefrigeration material with a wide operating temperature range is thus prepared.

[0053] Figure 1 For this embodiment, a layer of alloy film is prepared on a NaCl single crystal substrate using a pulsed laser deposition system at 450°C. The substrate size is 1cm×1cm. At this time, the flatness of the film is relatively high. Then, the alloy film is naturally formed during the in-situ annealing to room temperature. Finally, a low-temperature glue is used to constrain and transfer the film on the NaCl substrate to obtain a wrinkled film with a non-uniform strain gradient.

[0054] Figure 2 This is an optical microscope image of the wrinkled film finally prepared in Example 1. Figure 2It can be seen from the wrinkle morphology that the introduction of non-uniform strain gradient, that is, the introduction of flexomagnetic effect.

[0055] Comparative Example 1

[0056] Comparative Example 1 provides a flat magneto-refrigeration alloy film, which is prepared by the following steps: keeping the growth parameters in steps (1) to (3) in Example 1 unchanged, and the difference between this comparative example and Example 1 is that the single crystal substrate is different. In this comparative example, an alloy film is prepared on a MgO single crystal substrate, and a wrinkle morphology similar to that of a NaCl single crystal substrate cannot be formed on the single crystal substrate. The obtained film is flat and tightly bonded to the MgO single crystal substrate. The preparation method comprises the following steps:

[0057] 1) First, a layer of alloy film was prepared on a MgO single crystal substrate with a size of 1 cm×1 cm using a pulsed laser deposition system at a growth temperature of 450°C, and the thickness of the alloy film was controlled to be 30 nm;

[0058] 2) Maintain the temperature of the alloy film at 500°C and anneal for 0.5h;

[0059] 3) Turn off the temperature control switch, maintain a high vacuum environment, and wait for the alloy film to naturally cool down to room temperature to form a flat morphology.

[0060] The film prepared by the above method cannot form the wrinkle morphology and wide cooling temperature range of the non-uniform strain gradient in Example 1.

[0061] Figure 3 This is a scanning electron microscope image of the smooth film finally prepared in Comparative Example 1.

[0062] Comparative Example 2

[0063] Comparative Example 2 provides a magnetic cooling alloy target for preparing an alloy target, and the alloy target is prepared by the following steps:

[0064] 1) Weigh a predetermined amount of metal element (Ni:Mn:Sn=2.0:1.5:0.5) raw material with a purity higher than 99.95%;

[0065] 2) Melting in an arc melting furnace in an argon atmosphere, and repeatedly melting three times to ensure the uniformity of the target material. The composition of the target material is basically consistent with the Ni-Mn-Sn alloy film in Example 1;

[0066] 3) The smelted target material is vacuum sealed in a quartz tube, annealed at 1173K for 24h, and then rapidly quenched in cold water to obtain an alloy target material.

[0067] The bulk alloy prepared by the above method cannot form the wide operating temperature range ( Figure 7 (S1).

[0068] pass Figure 4 The measurement of the thermomagnetic curves revealed that after the introduction of the non-uniform strain gradient, the transition hysteresis between the FCC and FCH curves of the wrinkled film prepared in Example 1 was significantly reduced compared with the bulk alloy and the flat film (MgO substrate). The wrinkled film is the magnetic cooling material finally prepared in Example 1. The flat film and the alloy block are the magnetic cooling materials prepared in Comparative Examples 1 and 2, respectively.

[0069] Depend on Figure 5 Through the measurement of the hysteresis loop, it is found that after the introduction of the non-uniform strain gradient, the saturation magnetization intensity of the wrinkled film is increased by more than 40% compared with the bulk alloy and the flat film (MgO substrate) in a wide temperature range. Among them, the wrinkled film is the magnetic cooling material finally prepared in Example 1. The flat film and the alloy block are the magnetic cooling materials prepared in Comparative Examples 1 and Comparative Examples 2, respectively.

[0070] Figure 6 and Figure 7 Bulk alloy, flat film (MgO substrate) and wrinkled film were used as magnetic cooling materials to study their isothermal magnetization curves, magnetic entropy change and cooling capacity. Figure 7 S3 shows that the wrinkled film has an extremely wide working temperature range, while S1 and S2 show that the magnetic cooling working temperature range and cooling capacity of the bulk alloy and flat film (MgO substrate) are much smaller than those of the wrinkled film. Among them, the wrinkled film is the magnetic cooling material finally prepared in Example 1. The flat film and the alloy block are the magnetic cooling materials prepared in Comparative Examples 1 and 2, respectively. Figure 6 Isothermal magnetization curve, showing that the saturation magnetization intensity of the wrinkled film is significantly improved compared with the bulk alloy and flat film (MgO substrate) in a wide temperature range.

[0071] Figure 8 By comparing with other magnetoresistive alloys, the wrinkled film has small transition hysteresis, high cooling capacity and wide operating temperature range, showing its excellent performance.

[0072] Among them: calculation method of magnetic entropy change and cooling capacity, Figure 7 The magnetic entropy change (ΔS) is calculated using the Maxwell relation (Eq. (1)) from Figure 6 The isothermal magnetization curve is obtained, where T and H represent temperature and magnetic field respectively. The refrigeration capacity (RC) is determined by the relationship (2), where δT FWHM represents the half-height width of the ΔS peak, |ΔS max | is the maximum value of the ΔS peak. Using equation (3), the effective RC (Effective Refrigerant Capacity, RC eff) is calculated by subtracting the average hysteresis loss from the RC value. )get.

[0073]

[0074] RC=|ΔS max |×δT FWHM (2)

[0075]

[0076] Example 2

[0077] Example 2 provides a magnetic refrigeration material with a wide operating temperature range and a preparation method thereof, which differs from Example 1 in that in step (2), the annealing temperature is 450°C; in step (2), the annealing time is 1 hour; and the steps and condition parameters are the same as those of Example 1. The magnetic properties of the corrugated film prepared by the above method are equivalent to those of the corrugated film prepared in Example 1.

[0078] Example 3

[0079] Example 3 provides a magnetic refrigeration material with a wide operating temperature range and a preparation method thereof, which differs from Example 1 in that in step (1), the growth temperature of the NiMnSn alloy film is 500°C; in step (2), the annealing temperature is 550°C; in step (2), the annealing time is 1h; and the steps and condition parameters are the same as those of Example 1. The magnetic properties of the wrinkled film prepared by the above method are equivalent to those of the wrinkled film prepared in Example 1.

[0080] Comparative Example 3

[0081] Comparative Example 3 provides a magnetic cooling material with a wide operating temperature range and a preparation method thereof. The difference between the comparative example 3 and the embodiment 1 is that the single crystal substrate is different. The magnetic cooling alloy is prepared on SrTiO3 and Al2O3 single crystal substrates respectively. On these single crystal substrates, a wide cooling temperature range similar to that of the NaCl single crystal substrate cannot be formed. The obtained film is flat and tightly combined with the SrTiO3 and Al2O3 single crystal substrates. The preparation method comprises the following steps:

[0082] 1) First, a layer of alloy film was prepared on a SrTiO3 and Al2O3 single crystal substrate with a size of 1cm×1cm at a growth temperature of 450°C using a pulsed laser deposition system. The thickness of the alloy film was controlled to be 30nm.

[0083] 2) Maintain the temperature of the alloy film at 500°C and anneal for 0.5h;

[0084] 3) Turn off the temperature control switch, maintain a high vacuum environment, and wait for the alloy film to naturally cool down to room temperature to form a flat morphology.

[0085] The film prepared by the above method cannot form the wide cooling temperature range in Example 1.

[0086] The present invention provides a magnetocaloric material with a wide operating temperature range and a preparation method thereof. Compared with the traditional flat film deposition method, the preparation method provides a peelable self-supporting wrinkled morphology with a non-uniform strain gradient. The non-uniform strain gradient is introduced by transferring the film on the NaCl substrate using a low-temperature glue, so that the magnetic properties and magnetocaloric performance of the film are significantly improved. The whole set of operation procedures is simple and has certain application prospects. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principle of the present invention. For example, in addition to depositing certain magnetocaloric multi-element alloys or magnetocaloric metal elements, for some functional materials with good ductility and strength, non-uniform strain gradients can also be introduced based on this method and corresponding wrinkled films can be obtained to improve the magnetic properties and magnetocaloric performance. Alternatively, alloy films are prepared by vacuum coating methods such as magnetron sputtering, and these improvements should also be regarded as the scope of protection of the present invention.

Claims

1. A magnetic refrigeration material with a wide operating temperature range, characterized in that: The magnetic cooling material is a wrinkled alloy film with non-uniform strain gradient.

2. The magnetic refrigeration material with a wide operating temperature range according to claim 1, characterized in that: The magnetocaloric material is a wrinkled alloy film with a non-uniform strain gradient obtained by transferring the alloy film.

3. The magnetic refrigeration material with a wide operating temperature range according to claim 1, characterized in that: The thickness of the alloy film is 20nm-50nm.

4. The magnetic refrigeration material with a wide operating temperature range according to claim 1, characterized in that: The alloy film includes a multi-component Heusler alloy.

5. The magnetic refrigeration material with a wide operating temperature range according to claim 1, characterized in that: The alloy film is preferably a Ni—Mn—Sn alloy film.

6. A method for preparing a magnetic refrigeration material with a wide operating temperature range as claimed in claim 1, characterized in that: The following steps are involved: (1) depositing an alloy film on a NaCl single crystal substrate; (2) in-situ annealing after depositing the alloy film, followed by cooling to room temperature; (3) Using low-temperature tape to transfer the film on the NaCl substrate can obtain a wrinkled film with non-uniform strain gradient.

7. The method for preparing a magnetic refrigeration material with a wide operating temperature range according to claim 6, characterized in that: In step (1), the temperature for depositing the metal film on the substrate is 400° C.-450° C., and the method for depositing the alloy film on the NaCl single crystal substrate is pulsed laser deposition or laser-assisted molecular beam epitaxy.

8. The method for preparing a magnetic refrigeration material with a wide operating temperature range according to claim 6, characterized in that: In step (2), the annealing temperature is 450°C-500°C, and the annealing time is 0.5h-1h.

9. Use of the magnetic refrigeration material according to claim 1 in preparing a magnetic refrigeration material with a wide operating temperature range, small transition hysteresis and high refrigeration capacity.

10. Use of the magnetorefrigid material according to claim 1 as a refrigerant in refrigeration equipment, electronic equipment heat dissipation, precision instruments, aerospace, medical cold chain and low-temperature storage.

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