Magnetic refrigeration material with wide working temperature range, preparation method and application thereof

Abstract

The application 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. The wrinkled alloy film has an extremely wide working temperature range as the magnetic refrigeration material. The application utilizes the different expansion coefficients and weak van der Waals interaction between the alloy film and a NaCl substrate, so that the film presents a self-supporting wrinkled morphology on the substrate. The film with the wrinkled morphology is simple in preparation process and can be easily separated from the substrate while the wrinkled morphology is reserved to obtain the wrinkled film. After the non-uniform strain gradient is introduced, the saturation magnetization of the wrinkled film under the wide temperature range is significantly improved compared with the bulk alloy and the flat film. Meanwhile, the magnetic entropy change result shows that the wrinkled film as the magnetic refrigeration material has an extremely wide working temperature range, and the magnetic refrigeration capacity of the wrinkled film is much higher than that of the bulk alloy and the flat film.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to a magnetocaloric material with a wide operating temperature range, its preparation method, and its application. Background Technology

[0002] Pulsed laser deposition systems utilize high-energy, high-density pulsed lasers as excitation sources. Focused within a vacuum chamber, these lasers ablate the surface of a solid target, generating a plasma plume. This plume is then directionally transported to the target substrate surface, where it rapidly cools, ultimately forming a film on the substrate surface. The resulting films exhibit uniform thickness and composition highly consistent with the target material, facilitating the preparation of multi-component compounds. Furthermore, the deposition process is pollution-free and easily controlled, allowing for flexible adjustment of geometric parameters, laser parameters, substrate conditions, and reaction atmosphere to obtain high-quality films.

[0003] Due to size effects and the constraints of hard substrates, phase transitions in magnetocaloric alloy films with thicknesses below tens of nanometers are suppressed, severely affecting many phase transition-related magnetic response effects. Notably, by decoupling the film and substrate, i.e., by creating self-supporting alloy films with high degrees of freedom and surface-to-volume ratios, their functionality can be extended through the design of complex strain geometries. Currently, there are two major problems in the field of magnetocaloric cooling: (1) a limited operating temperature window; and (2) a large transition hysteresis.

[0004] The prior art (CN 117127202 A) discloses a catalyst and its preparation method that utilizes strain gradient to induce magnetic enhancement and magnetic field response. The alloy film is obtained by binding the alloy film to obtain a wrinkled morphology with strain gradient. However, the wrinkled film can only be used as a catalyst for hydrogen evolution 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 magnetorheological material with a wide operating temperature range. This material has the characteristics of low hysteresis, wide operating temperature range and high cooling capacity, which effectively solves the bottleneck problem in the current field of magnetorheological refrigeration.

[0006] The present invention also provides a method for preparing and applying magnetorheological materials with a wide operating temperature range.

[0007] Technical solution: In order to achieve the above objectives, the present invention provides a magnetocaloric material with a wide operating temperature range, wherein the magnetocaloric material is a wrinkled alloy thin 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 it has an extremely wide operating temperature range as a magnetocaloric material.

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

[0010] The alloy film includes a multi-component Hassler alloy.

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

[0012] The method for preparing the magnetorheological material with a wide operating temperature range according to the present invention includes the following steps:

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

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

[0015] (3) A wrinkled film with a non-uniform strain gradient can be obtained by transferring the film on the NaCl substrate using low-temperature tape.

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

[0017] In step (2), the annealing temperature is 450℃-500℃ and the annealing time is 0.5h-1h.

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

[0019] The application of the magnetocaloric material described in this invention in the preparation of magnetocaloric materials with a wide operating temperature range, small transition hysteresis, and high cooling capacity.

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

[0021] This invention discloses a magnetocaloric material with a wide operating temperature range induced by a non-uniform strain gradient. An alloy target is deposited on a NaCl substrate using pulsed laser deposition at a specific growth temperature to form a continuous and uniform thin film. During in-situ annealing and cooling to room temperature, the different coefficients of thermal expansion and weak van der Waals interactions between the NaCl substrate and the thin film cause the film to exhibit a self-supporting wrinkled morphology on the substrate. Transferring the thin film from the NaCl substrate using a low-temperature adhesive yields a wrinkled film with a non-uniform strain gradient. After introducing geometric strain, the wrinkled film exhibits significantly enhanced magnetization compared to bulk alloys and planar alloy films grown on hard substrates, and magnetic entropy change measurements show that the wrinkled film possesses an extremely wide operating temperature range.

[0022] The cooling material described in this invention is an alloy thin film with a wrinkled morphology exhibiting a non-uniform strain gradient. Due to the different expansion coefficients and weak van der Waals interactions between the alloy thin film and the NaCl substrate, the film exhibits a self-supporting wrinkled morphology on the substrate. Furthermore, the fabrication process for this wrinkled film is simple, and it can be easily separated from the substrate while retaining the wrinkled morphology to obtain a wrinkled film. The introduction of a non-uniform strain gradient (i.e., flexural magnetism) induces a continuous phase transition in the wrinkled film, and the saturation magnetization of the wrinkled film is significantly improved over a wide temperature range compared to the bulk alloy and flat film (MgO substrate), resulting in a simultaneous increase in both magnetic entropy and lattice entropy. Simultaneously, magnetic entropy change results indicate that the wrinkled film, as a magnetocaloric material, has an extremely wide operating temperature range, and the magnetocaloric capacity of the wrinkled film is much higher than that of the bulk alloy and flat film (MgO substrate).

[0023] This invention overcomes the long-standing obstacles of magnetocaloric alloys in wide-temperature-range magnetocaloric cooling by introducing a non-uniform strain gradient, namely, the limited operating temperature window and the typical large transition hysteresis. To overcome the shortcomings of existing magnetocaloric alloy thin films in terms of operating temperature range, this invention provides a process for obtaining wrinkled alloy thin films, and further broadens the magnetocaloric operating temperature range and cooling capacity of the wrinkled films by introducing a non-uniform strain gradient.

[0024] The magnetocaloric material prepared in this invention, in a Hassler alloy with a non-uniform strain gradient, exhibits two main characteristics: firstly, the non-uniform strain gradient induces a continuous phase transition; secondly, flexural magnetism enhances the ferromagnetic moment, leading to a simultaneous increase in magnetic entropy and lattice entropy, ultimately resulting in an extremely wide operating temperature range. Furthermore, the material prepared in this invention possesses a wide operating temperature range, small transition hysteresis, and high cooling capacity. The preparation process also utilizes low-temperature adhesive transfer, making it more convenient.

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

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

[0027] (2) The present invention ingeniously introduces a non-uniform strain gradient into the thin film by means of the difference in the expansion coefficient between the substrate and the thin film and the transfer of the low temperature tape.

[0028] (3) The magnetorheological 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.) Hassler alloys, the preparation process is repeatable. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a magnetocaloric material preparation process with a wide operating temperature range, provided as an embodiment of the present invention.

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

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

[0033] Figure 4 The thermomagnetic curves of the alloy block, flat film (MgO substrate), and wrinkled film in an embodiment of the present invention under a 0.1 kΩ Oersted magnetic field.

[0034] Figure 5 The hysteresis loops of the alloy block, flat film (MgO substrate), and wrinkled film at different temperatures are shown in the embodiments of the present invention.

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

[0036] Figure 7 The alloy block, flat film (MgO substrate), and wrinkled film are used as magnetocaloric materials in the embodiments of the present invention, and their magnetic entropy changes and cooling capacities under different magnetic fields are shown.

[0037] Figure 8 The graph shows the performance comparison of this invention with other magnetorheological materials, with effective cooling capacity as the horizontal axis and transformation hysteresis and operating temperature range as the vertical axes. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. Experimental methods not specifically described in the examples are generally performed under standard conditions or as recommended by the manufacturer.

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

[0041] Ni, Mn, and Sn are commercially available conventional metallic elements.

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

[0043] In this embodiment of the invention, the prepared materials are tested using the following methods:

[0044] Thermomagnetic curve measurement: Thermomagnetic curves of the bulk alloy film, flat film, and wrinkled film were measured using a superconducting quantum interference device (SQUID) manufactured by Quantum Design, USA. The data recording was divided into three parts. The sample was first cooled from 350 K to 10 K using zero-field cooling (ZFC) mode, and then heated from 10 K to 350 K under a 0.1 kOe magnetic field. Subsequently, the film was cooled below 10 K under a 0.1 kOe magnetic field, and data was recorded under field-cooled cooling (FCC) mode. After reaching 10 K, the film was reheated to 350 K under the same magnetic field, and the thermomagnetic curve data was recorded under field-cooled heating (FCH) mode.

[0045] Hysteresis loop measurement: A superconducting quantum interference device (SQUID) manufactured by Quantum Design, USA, was used to measure the hysteresis loops of the alloy bulk, flat film, and wrinkled film, respectively. The hysteresis loop data was recorded in four parts: 50 kilo-Oerst to 0 oscillators, 0 oscillators to -50 kilo-Oerst, -50 kilo-Oerst to 0 oscillators, and 0 oscillators to 50 kilo-Oerst. Furthermore, before each measurement, the superconducting magnet was demagnetized by oscillation at 300 K to ensure that there was no residual magnetic flux in the tested film.

[0046] Measurement of magnetic entropy change: A superconducting quantum interference device (SQU) manufactured 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 temperature intervals of 20K. The isothermal magnetization curve data were recorded in two parts: the magnetic field from 0 Oersted to 50 kilo-Oersted, and then from 50 kilo-Oersted back to 0 Oersted. Furthermore, the superconducting magnet was demagnetized by oscillation before each measurement to ensure that there was no residual magnetic flux in the tested film.

[0047] Example 1

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

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

[0050] 2) The substrate on which the alloy thin film is deposited is kept at 500°C in a high vacuum environment (<1.0×10⁻⁶). -4 Annealing for 0.5 hours (Pa);

[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 wrinkled morphology.

[0052] 4) The thin film on the NaCl substrate is transferred using a low-temperature adhesive (the wrinkled film is bonded with one side facing down to a low-temperature adhesive tape with a polyimide adhesive layer, and then the NaCl substrate is removed to obtain the wrinkled film). A wrinkled film with a non-uniform strain gradient (1cm×1cm) can be obtained, and a magnetocaloric material with a wide operating temperature range is thus prepared.

[0053] Figure 1 In this embodiment, an alloy thin film was prepared on a NaCl single crystal substrate at 450°C using a pulsed laser deposition system. The substrate size was 1cm × 1cm. At this time, the flatness of the film was relatively high. Then, the alloy thin film naturally formed wrinkles during in-situ annealing to room temperature. Finally, the film on the NaCl substrate was bound and transferred using a low-temperature adhesive to obtain a wrinkled thin 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. From... Figure 2The wrinkled morphology shows that a non-uniform strain gradient was introduced, i.e., a flexural magnetic effect was introduced.

[0055] Comparative Example 1

[0056] Comparative Example 1 provides a flat magnetocaloric alloy thin film, which is prepared by the following steps: keeping the growth parameters in steps (1) to (3) of Example 1 unchanged, the difference from Example 1 is the single crystal substrate. In this comparative example, the alloy thin film is prepared on a MgO single crystal substrate. On this single crystal substrate, it is impossible to form a wrinkled morphology similar to that of the NaCl single crystal substrate. The resulting film is flat and tightly bonded to the MgO single crystal substrate. The preparation method includes the following steps:

[0057] 1) First, at a growth temperature of 450℃, an alloy thin film was prepared on a 1cm×1cm MgO single crystal substrate using a pulsed laser deposition system. The thickness of the alloy thin film was controlled at 30nm.

[0058] 2) Maintain the temperature of the alloy film at 500℃ and anneal for 0.5 hours;

[0059] 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, thus forming a smooth morphology.

[0060] The thin films prepared by the above method cannot form the wrinkled 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 flat film finally prepared in Comparative Example 1.

[0062] Comparative Example 2

[0063] Comparative Example 2 provides a magnetocooled alloy target for preparing alloy targets, which is prepared by the following steps:

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

[0065] 2) The target material is melted in an argon atmosphere using an electric arc melting furnace, and the melting is repeated three times to ensure the uniformity of the target material. The composition of the target material is basically the same as that of 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 24 hours, and then rapidly quenched in cold water to obtain the alloy target material.

[0067] The bulk alloys prepared by the above method cannot achieve the wide operating temperature range shown in Example 1. Figure 7 (S1).

[0068] pass Figure 4 Measurements of the thermomagnetic curves revealed that, after introducing a non-uniform strain gradient, the transition hysteresis between the FCC and FCH curves of the wrinkled thin film prepared in Example 1 was significantly reduced compared to that of the bulk alloy and the flat thin film (MgO substrate). The wrinkled thin film was the final magnetocaloric material prepared in Example 1. The flat thin film and the bulk alloy were magnetocaloric materials prepared in Comparative Examples 1 and 2, respectively.

[0069] Depend on Figure 5 Hysteresis loop measurements revealed that, after introducing a non-uniform strain gradient, the saturation magnetization of the wrinkled film was increased by more than 40% over a wide temperature range compared to the bulk alloy and the flat film (MgO substrate). The wrinkled film was the magnetocaloric material finally prepared in Example 1. The flat film and the bulk alloy were magnetocaloric materials prepared in Comparative Examples 1 and 2, respectively.

[0070] Figure 6 and Figure 7 Bulk alloys, flat thin films (MgO substrates), and wrinkled thin films were used as magnetocaloric materials, and their isothermal magnetization curves, magnetic entropy changes, and cooling capacities were studied. Figure 7 S3 shows that the wrinkled film has an extremely wide operating temperature range, while S1 and S2 show that the magnetocaloric operating temperature range and cooling capacity of the bulk alloy and the flat film (MgO substrate) are much smaller than those of the wrinkled film. The wrinkled film is the magnetocaloric material finally prepared in Example 1. The flat film and the bulk alloy are magnetocaloric materials prepared in Comparative Examples 1 and 2, respectively. Figure 6 The isothermal magnetization curves show that the saturation magnetization of the wrinkled film is significantly improved over a wide temperature range compared to the bulk alloy and flat film (MgO substrate).

[0071] Figure 8 Compared with other magnetorheological alloys, the wrinkled film exhibits superior performance due to its small transition hysteresis, high cooling capacity, and wide operating temperature range.

[0072] Among them: the calculation methods for magnetic entropy change and cooling capacity. Figure 7 The magnetic entropy change (ΔS) is calculated using Maxwell's relation ((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 equation (2), where δT... FWHM The full width at half maximum (FWHM) of the ΔS peak is represented by |ΔS max | represents the maximum value of the ΔS peak. Using relation (3), the effective RC (Effective Refrigerant Capacity, RC effSubtract 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 magnetorheological material with a wide operating temperature range and its preparation method. The difference between Example 2 and Example 1 is that in step (2), the annealing temperature is 450°C; the annealing time is 1 hour; and the steps and conditions are the same as in Example 1. The magnetic properties of the wrinkled film prepared by the above method are comparable to those of the wrinkled film prepared in Example 1.

[0078] Example 3

[0079] Example 3 provides a magnetocaloric material with a wide operating temperature range and its preparation method. The difference between Example 3 and Example 1 is that in step (1), the growth temperature of the NiMnSn alloy thin film is 500℃; in step (2), the annealing temperature is 550℃; and in step (2), the annealing time is 1 h. The steps and conditions are the same as in Example 1. The magnetic properties of the wrinkled thin film prepared by the above method are comparable to those of the wrinkled thin film prepared in Example 1.

[0080] Comparative Example 3

[0081] Comparative Example 3 provides a magnetocaloric material with a wide operating temperature range and its preparation method. The difference between this and Example 1 lies in the different single-crystal substrates. In this comparative example, magnetocaloric alloys are prepared on SrTiO3 and Al2O3 single-crystal substrates, respectively. A wide cooling temperature range similar to that of the NaCl single-crystal substrate cannot be formed on these single-crystal substrates. The resulting thin film is flat and tightly bonded to both the SrTiO3 and Al2O3 single-crystal substrates. The preparation method includes the following steps:

[0082] 1) First, at a growth temperature of 450℃, an alloy thin film was prepared on a 1cm×1cm SrTiO3 and Al2O3 single crystal substrate using a pulsed laser deposition system. The thickness of the alloy thin film was controlled at 30nm.

[0083] 2) Maintain the temperature of the alloy film at 500℃ and anneal for 0.5 hours;

[0084] 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, thus forming a smooth morphology.

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

[0086] This invention provides a magnetocaloric material with a wide operating temperature range and its preparation method. Compared with traditional flat thin film deposition methods, this preparation method provides a peelable, self-supporting wrinkled morphology with a non-uniform strain gradient. A non-uniform strain gradient is introduced by transferring the thin film on a NaCl substrate using a low-temperature adhesive, significantly improving both the magnetic properties and magnetocaloric performance of the film. The entire operation process is simple and has promising applications. It should be noted that those skilled in the art can make several improvements without departing from the principles of this invention. For example, in addition to depositing certain magnetocaloric multi-element alloys or magnetocaloric metallic elements, this method can also be used to introduce a non-uniform strain gradient and obtain corresponding wrinkled films for some functional materials with good ductility and strength, thereby improving their magnetic properties and magnetocaloric performance. Alternatively, alloy thin films can be prepared using vacuum deposition methods such as magnetron sputtering; these improvements should also be considered within the scope of this invention.

Claims

1. A magnetocaloric material with a wide operating temperature range, characterized in that, The magnetocaloric material is a wrinkled alloy thin film with a non-uniform strain gradient; The method for preparing the magnetorheological material with a wide operating temperature range includes the following steps: (1) Deposit an alloy thin film on a NaCl single crystal substrate; (2) After depositing the alloy thin film, in-situ annealing is performed, followed by cooling to room temperature; (3) A wrinkled film with a non-uniform strain gradient can be obtained by transferring the film on the NaCl substrate using low-temperature tape. In step (1), the temperature for depositing the metal thin film on the substrate is 400℃-450℃, and the method for depositing the alloy thin film on the NaCl single crystal substrate is pulsed laser deposition or laser-assisted molecular beam epitaxy; in step (2), the annealing temperature is 450℃-500℃, and the annealing time is 0.5 h-1 h.

2. The magnetorheological 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 an alloy film.

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

4. The magnetorheological material with a wide operating temperature range according to claim 1, characterized in that, The alloy film comprises a multi-component Hassler alloy.

5. The magnetorheological material with a wide operating temperature range according to claim 1, characterized in that, The alloy film is a Ni-Mn-Sn alloy film.

6. The application of the magnetocaloric material of claim 1 in the preparation of a magnetocaloric material with a wide operating temperature range, small transition hysteresis and high cooling capacity.

7. The application of the magnetorheological material of claim 1 as a refrigerant in refrigeration equipment, heat dissipation of electronic equipment, precision instruments, aerospace, medical cold chain and low temperature storage.

Images