An EuTiO3-based composite material, its preparation method and application

Abstract

The application relates to a EuTiO3-based composite material and a preparation method and application thereof, and belongs to the technical field of magnetic refrigeration materials. The EuTiO3-based composite material provided by the application comprises a EuTiO3 base and a metal filler; wherein the EuTiO3 base is EuTiO3 and / or EuTiO3 doped with metal M, the metal M is at least one of Al, Nb, Ta and Zr; the metal filler is Cu, and the mass content of the Cu is 2-20%; and the preparation method is that a copper layer is uniformly covered on the surface of EuTiO3-based micro powder by adopting a chemical plating technology, and then tabletting and sintering are carried out to obtain the EuTiO3-based composite material. The EuTiO3-based composite material has both large magnetic heat effect and high thermal conductivity in a liquid helium temperature range, can obtain high heat exchange efficiency and refrigeration capacity in a magnetic refrigeration system, and has high practical value.

Description

Technical Field

[0001] This invention relates to the field of magnetic refrigeration materials technology, and in particular to an EuTiO3-based composite material, its preparation method, and its application. Background Technology

[0002] Over the past few decades, research on magnetic refrigeration materials has made significant progress, with many materials exhibiting large magnetocaloric effects in the liquid helium temperature range emerging. Perovskite-type EuTiO3 is a typical multiferroic material with a magnetic phase transition temperature around 5.5 K. Its maximum magnetic entropy values ​​at Δμ0H = 1 and 5 T are 11.0 and 42.4 J·kg, respectively. -1 ·K -1 However, the saturation magnetic entropy change of EuTiO3, calculated using the local magnetic moment model Rln(2J+1)(J=7 / 2), reaches 69.8 J·kg⁻¹. -1 ·K -1 This indicates that there is still significant room for improvement in the magnetic entropy change of this magnetic system. Existing techniques, such as applying strain to induce lattice distortion and introducing itinerant electrons or oxygen vacancies, can achieve greater magnetocaloric effects at lower magnetic fields. CN111072063A discloses a low-temperature magnetic refrigeration material, EuTi. 1-x The magnetic entropy change of AlxO3 under a magnetic field change of 0-1T is 11.6-15.6 J·kg. -1 ·K -1 The cooling capacity is 48-58.2 J·kg -1 These oxide materials exhibit significant magnetocaloric properties near their phase transition temperatures. However, their thermal conductivity is generally low, especially decreasing sharply with decreasing temperature, which limits their practical applications.

[0003] In magnetic refrigeration applications, to achieve good refrigeration performance, magnetic refrigeration materials are required to exhibit not only a large magnetocaloric effect but also excellent thermal conductivity to achieve high thermal efficiency and refrigeration capacity during the magnetic refrigeration cycle. However, researchers have paid relatively little attention to the thermal conductivity of materials. Zheng Wenshuai et al. (Appl. Therm. Eng. 226(2023)120272) used EuTiO3 series materials combined with Pb and ErNi to construct a regenerator for a GM magnetic refrigerator, achieving a minimum no-load refrigeration temperature of 2.48K at an operating frequency of 0.4Hz; however, the refrigeration capacity of the system at 4.2K was only 0.65W, far less than the theoretical value. One possible reason is that the thermal conductivity of EuTiO3 series materials is too low in the liquid helium temperature range, resulting in very low heat exchange efficiency of the system.

[0004] Therefore, developing a material with a large magnetocaloric effect and significantly improving the thermal conductivity of magnetic refrigeration materials at low temperatures, as well as its preparation method, to improve heat exchange efficiency and overcome application bottlenecks, is of great scientific value and strategic significance for the early application of magnetic refrigeration technology in end-user applications and for supporting low-temperature scientific research and low-temperature applications in the field of nuclear magnetic resonance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a EuTiO3-based composite material, its preparation method, and its applications. The EuTiO3-based composite material provided by this invention possesses both a large magnetocaloric effect and a high thermal conductivity in the liquid helium temperature range, thus improving heat transfer efficiency and exhibiting high practical value.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides an EuTiO3-based composite material, comprising an EuTiO3 matrix and a metal filler; wherein the EuTiO3 matrix is ​​EuTiO3 and / or EuTiO3 doped with metal M, wherein the metal M is at least one selected from Al, Nb, Ta, and Zr; and wherein the metal filler is Cu, wherein the mass content of Cu is 2-20%.

[0008] The EuTiO3 composite material provided by this invention comprehensively improves the magnetic refrigeration performance of the material by combining EuTiO3 matrix and metal filler Cu. The composite material not only exhibits a large magnetic entropy change and good refrigeration capacity near the liquid helium temperature, but also has excellent thermal conductivity and high heat exchange efficiency.

[0009] The aforementioned EuTiO3 matrix includes EuTiO3 and / or EuTiO3 doped with specific metals. Composite materials with a specific mass content of Cu on the EuTiO3 matrix can effectively balance the material's thermal conductivity and magnetocaloric effect. If the Cu mass content is less than 2% or no composite is used, the thermal conductivity of the material near the liquid helium temperature decreases significantly; if the Cu mass content is greater than 20%, the magnetocaloric properties of the material are affected, and the magnetocaloric effect is significantly weakened in the low-temperature region.

[0010] The EuTiO3-based composite material provided by this invention achieves a maximum magnetic entropy change of 15 J·kg⁻¹ under a magnetic field change of 0–1 T at a temperature of 5.5 K. -1 ·K -1 The maximum magnetic entropy change of the magnetic field from left to right and from 0 to 2T can reach 24 J·kg. -1 ·K -1 The above is true; furthermore, the thermal conductivity of this composite material at the liquid helium temperature (4.2K) can reach 5 W·m. -1 K -1It can be applied to the field of magnetic refrigeration technology in the liquid helium temperature range, and has significant scientific value and strategic significance for the construction of scientific research platforms in the liquid helium temperature range and the low-temperature application in the field of nuclear magnetic resonance.

[0011] Preferably, the Cu content is 4-6% by mass. The selection of this EuTiO3 matrix and the defined Cu content can effectively balance the magnetocaloric effect and thermal conductivity of the composite material.

[0012] Preferably, the maximum magnetic entropy change of the EuTiO3-based composite material under a magnetic field change of 0-1T is 11.5-15 J·kg. -1 ·K -1 The maximum magnetic entropy change under a magnetic field variation of 0-2T is 19.5-25 J·kg. -1 ·K -1 .

[0013] Preferably, the thermal conductivity of the EuTiO3-based composite material is 1.7-6 W·m at a temperature of 4.2 K. -1 K -1 .

[0014] The EuTiO3-based composite material provided by this invention has a significantly higher thermal conductivity at low temperatures than that of titanate materials in the prior art at the same temperature, and also exhibits a large magnetocaloric effect, making it a high-performance magnetic refrigeration material in the liquid helium temperature range.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned EuTiO3-based composite material, comprising the following steps:

[0016] (1) The EuTiO3-based micro powder is activated, degelatinated, and copper-plated to obtain composite micro powder; the particle size of the EuTiO3-based micro powder is 100-300 μm;

[0017] (2) The composite micro powder is pressed into a green body and then sintered in a protective atmosphere to obtain the EuTiO3-based composite material.

[0018] The aforementioned EuTiO3-based composite material is prepared by uniformly coating a copper layer onto the surface of EuTiO3-based micropowder within a specific particle size range using chemical plating, followed by pressing and sintering. The internal EuTiO3-based micropowder forms a uniform and dense microstructure with a continuous Cu filler network, thereby improving the composite material's thermal conductivity while also exhibiting good magnetocaloric effects. The prepared EuTiO3-based composite material can achieve high heat exchange efficiency and cooling capacity in magnetic refrigeration systems, demonstrating high application value. The EuTiO3-based micropowder can be EuTiO3 and / or EuTiO3 doped with metal M, and its shape can be spherical or irregular.

[0019] Preferably, in step (1), the activation includes the following steps: adding EuTiO3-based micro powder to an activator solution at 30°C for activation, followed by washing to obtain activated micro powder; the stirring speed during activation is 350-400 r / min and the stirring time is 8-12 min; the activator solution includes the following components at the following concentrations: 200-300 ml / L hydrochloric acid, 3-6 ml / L palladium chloride, and 2-3 g / L stannous chloride.

[0020] Preferably, in step (1), the degellation includes the following steps: placing the activated micropowder into a degelatinizing agent solution at 50°C for 90-120 seconds, followed by washing to complete the degellation; the degelatinizing agent solution includes 20-30 ml / L hydrochloric acid. All hydrochloric acid is 37% concentrated hydrochloric acid.

[0021] Preferably, in step (1), the copper plating solution includes the following components at the following concentrations: 1-3 g / L anhydrous copper sulfate, 3-5 g / L formaldehyde, and 6-14 g / L sodium hydroxide.

[0022] Preferably, in step (1), the temperature of the plating solution is 30-45℃, the pH value is 12-13.5, the copper plating time is 3-40 min, and the copper plating rotation speed is 350-450 r / min.

[0023] By comprehensively controlling the copper plating process and the copper content in the material using the above-mentioned copper plating solution and conditions, a copper layer can be uniformly deposited and covered on the surface of EuTiO3-based micro powder. This allows the copper layer to form a suitable continuous network structure in the subsequent pressing and sintering steps, which is beneficial for improving thermal conductivity and heat exchange efficiency.

[0024] Preferably, in step (2), the pressure of pressing the green body is 400-3000 MPa.

[0025] Preferably, in step (2), the sintering temperature is 600-1000℃ and the holding time is 3-6h.

[0026] In a preferred embodiment of the method for preparing the high thermal conductivity magnetic refrigeration material of the present invention, the sintering temperature is 600-1000℃. For example, it can be 600℃, 700℃, 800℃, 900℃ or 1000℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] In a preferred embodiment of the preparation method of the high thermal conductivity magnetic refrigeration material of the present invention, the sintering time is 3h-6h. For example, it can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, in step (2), the protective atmosphere is an argon atmosphere or a hydrogen-argon mixture atmosphere.

[0029] More preferably, the hydrogen-argon mixed atmosphere is 10 vol% H2 + 90 vol% Ar, or the hydrogen-argon mixed atmosphere is 5 vol% H2 + 95 vol% Ar.

[0030] Thirdly, the present invention provides the application of the above-mentioned EuTiO3-based composite material in magnetic refrigeration.

[0031] Preferably, the magnetic refrigeration includes liquid helium temperature refrigeration.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] The EuTiO3-based composite material provided by this invention achieves a uniform and dense internal structure by uniformly coating a copper layer onto the surface of EuTiO3-based micropowder using chemical plating technology, followed by pressing and sintering, forming a continuous Cu filler network. This invention endows the material with superior magnetic refrigeration performance in the liquid helium temperature range by controlling the Cu filler content. Its thermal conductivity at low temperatures is significantly better than that of existing titanate materials at the same temperature, and it also exhibits a large magnetocaloric effect, enabling it to achieve high heat exchange efficiency and cooling capacity in magnetic refrigeration systems. Furthermore, the chemical plating technology used in the preparation of the material is simple, has good bonding properties, high yield, low cost, and is suitable for large-scale industrial production. Attached Figure Description

[0034] Figure 1 The graphs show the thermal conductivity of the EuTiO3-based composite materials and the pure EuTiO3 phase material in Examples 1, 2, and 3 of this invention as a function of temperature.

[0035] Figure 2 The graphs show the changes in magnetic entropy of the EuTiO3-based composite materials in Examples 1, 2, and 3 of this invention under different magnetic field variations.

[0036] Figure 3 The scanning electron microscope (SEM) image and corresponding EDS surface analysis image of the Cu / EuTiO3-based composite micropowder prepared by copper plating in Example 1 of this invention are shown.

[0037] Figure 4 The images shown are scanning electron microscope (SEM) images and corresponding EDS surface analysis images of the EuTiO3-based composite green body of Example 1 of this invention.

[0038] Figure 5 The images show scanning electron microscope (SEM) images and corresponding EDS surface analysis diagrams of the EuTiO3-based composite materials in Examples 1, 2, and 3 of this invention. Detailed Implementation

[0039] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available reagents and materials.

[0040] Example 1

[0041] One embodiment of the EuTiO3-based composite material of the present invention, wherein the EuTiO3-based composite material of this embodiment includes EuTi 0.875 Al 0.125 O3 matrix and Cu filler with a mass content of 5%.

[0042] The preparation method of the EuTiO3-based composite material provided by this invention is as follows:

[0043] (1) Preparation of composite micro powder:

[0044] Add hydrochloric acid and the dissolved stannous chloride solution to deionized water and stir. Then add palladium chloride solution to prepare an activator solution (250 ml / L hydrochloric acid, 4.5 ml / L palladium chloride, 2.5 g / L stannous chloride). Heat the solution in a 30°C water bath.

[0045] Weigh 5g of EuTi with a particle size of 100-300μm. 0.875 Al 0.125 O3 micro powder was added to the above activator solution and stirred at 350 r / min. After reacting for 10 min, the activated EuTi was added. 0.875 Al 0.125 O3 micro powder was washed with deionized water; the activated EuTi was then... 0.875 Al 0.125 O3 micro powder was placed in a descaling agent solution (25 ml / L hydrochloric acid), heated in a 50°C water bath for 2 minutes, and then washed with deionized water.

[0046] A chemical copper plating solution (2 g / L anhydrous copper sulfate, 4 g / L formaldehyde, 10 g / L sodium hydroxide) was prepared by adding copper sulfate pentahydrate, formaldehyde, etc., to deionized water. The pH was adjusted to 12.8-12.9 by adding sodium hydroxide solution, and then placed in a 40°C water bath. The degelatinized EuTi was then added to the copper plating solution. 0.875 Al 0.125 O3 micro powder was reacted for 12 minutes at a rotation speed of 400 rpm, then washed with deionized water, filtered, and dried to obtain Cu / EuTi. 0.875 Al 0.125 O3 composite micro powder.

[0047] (2) Green body forming: The Cu / EuTi obtained in step (1) 0.875 Al 0.125 O3 composite micro powder was pressed into a green body of composite material under a pressure of 600 MPa;

[0048] (3) High-temperature sintering: The green blank obtained in step (2) is sintered in a furnace with a hydrogen-argon mixed atmosphere (10 vol% hydrogen and 90 vol% argon) at a temperature of 600°C for 6 h to obtain the EuTiO3-based composite material, wherein the mass content of Cu is 5%.

[0049] Example 2

[0050] One embodiment of the EuTiO3-based composite material of the present invention, wherein the EuTiO3-based composite material of this embodiment includes EuTi 0.8125 Nb 0.125 Al 0.0625 O3 matrix and Cu filler with a mass content of 5.2%.

[0051] The preparation method of the EuTiO3-based composite material provided by this invention is as follows:

[0052] (1) Preparation of composite micro powder:

[0053] Add hydrochloric acid and the dissolved stannous chloride solution to deionized water and stir. Then add palladium chloride solution to prepare an activator solution (250 ml / L hydrochloric acid, 4.5 ml / L palladium chloride, 2.5 g / L stannous chloride). Heat the solution in a 30°C water bath.

[0054] Weigh 5g of EuTi with a particle size of 100-300μm. 0.8125 Nb 0.125 Al 0.0625 O3 micro powder was added to the above activator solution and stirred at 350 r / min. After reacting for 10 min, the activated EuTi was added. 0.8125 Nb 0.125 Al 0.0625 O3 micro powder was washed with deionized water; the activated EuTi was then... 0.8125 Nb 0.125 Al 0.0625 O3 micro powder was placed in a descaling agent solution (25 ml / L hydrochloric acid), heated in a 50°C water bath for 2 minutes, and then washed with deionized water.

[0055] A chemical copper plating solution (2 g / L anhydrous copper sulfate, 4 g / L formaldehyde, 10 g / L sodium hydroxide) was prepared by adding copper sulfate pentahydrate, formaldehyde, etc., to deionized water. The pH was adjusted to 12.8-12.9 by adding sodium hydroxide solution, and then placed in a 40°C water bath. The degelatinized EuTi was then added to the copper plating solution.0.8125 Nb 0.125 Al 0.0625 O3 micro powder was reacted for 12 minutes at a rotation speed of 400 rpm, then washed with deionized water, filtered, and dried to obtain Cu / EuTi. 0.8125 Nb 0.125 Al 0.0625 O3 composite micro powder.

[0056] (2) Green body forming: The Cu / EuTi obtained in step (1) 0.8125 Nb 0.125 Al 0.0625 O3 composite micro powder was pressed into a green body of composite material under a pressure of 600 MPa;

[0057] (3) High-temperature sintering: The green blank obtained in step (2) is sintered in a hydrogen-argon mixed atmosphere (10 vol% hydrogen and 90 vol% argon) furnace at 800°C for 6 h to obtain the EuTiO3-based composite material, wherein the mass content of Cu is 5.2%.

[0058] Example 3

[0059] One embodiment of the EuTiO3-based composite material of the present invention, wherein the EuTiO3-based composite material of this embodiment includes EuTi 0.9375 Ta 0.0625 O3 matrix and Cu filler with a mass content of 4.9%.

[0060] The preparation method of the EuTiO3-based composite material provided by this invention is as follows:

[0061] (1) Preparation of composite micro powder:

[0062] Add hydrochloric acid and the dissolved stannous chloride solution to deionized water and stir. Then add palladium chloride solution to prepare an activator solution (250 ml / L hydrochloric acid, 4.5 ml / L palladium chloride, 2.5 g / L stannous chloride). Heat the solution in a 30°C water bath.

[0063] Weigh 5g of EuTi with a particle size of 100-300μm. 0.9375 Ta 0.0625 O3 micro powder was added to the above activator solution and stirred at 350 r / min. After reacting for 10 min, the activated EuTi was added. 0.9375 Ta 0.0625 O3 micro powder was washed with deionized water; the activated EuTi was then... 0.9375 Ta 0.0625 O3 micro powder was placed in a descaling agent solution (25 ml / L hydrochloric acid), heated in a 50°C water bath for 2 minutes, and then washed with deionized water.

[0064] A chemical copper plating solution (2 g / L anhydrous copper sulfate, 4 g / L formaldehyde, 10 g / L sodium hydroxide) was prepared by adding copper sulfate pentahydrate, formaldehyde, etc., to deionized water. The pH was adjusted to 12.8-12.9 by adding sodium hydroxide solution, and then placed in a 40°C water bath. The degelatinized EuTi was then added to the copper plating solution. 0.9375 Ta 0.0625 O3 micro powder was reacted for 12 minutes at a rotation speed of 400 rpm, then washed with deionized water, filtered, and dried to obtain Cu / EuTi. 0.9375 Ta 0.0625 O3 composite micro powder.

[0065] (2) Green body forming: The Cu / EuTi obtained in step (1) 0.9375 Ta 0.0625 O3 composite micro powder was pressed into a green body of composite material under a pressure of 600 MPa;

[0066] (3) High-temperature sintering: The green blank obtained in step (2) is sintered in a hydrogen-argon mixed atmosphere (10 vol% hydrogen and 90 vol% argon) furnace at a temperature of 1000°C for 6 h to obtain the EuTiO3-based composite material, wherein the mass content of Cu is 4.9%.

[0067] Example 4

[0068] One embodiment of the EuTiO3-based composite material of the present invention, wherein the EuTiO3-based composite material of this embodiment includes EuTi 0.8125 Nb 0.125 Al 0.0625 O3 matrix and Cu filler with a mass content of 2.3%.

[0069] The difference between the preparation method of the EuTiO3-based composite material in this embodiment and that in Example 2 is that the copper plating time in step (1) is controlled at 4 minutes. The Cu mass content in the prepared EuTiO3-based composite material is 2.3%.

[0070] Example 5

[0071] One embodiment of the EuTiO3-based composite material of the present invention, wherein the EuTiO3-based composite material of this embodiment includes EuTi 0.8125 Nb 0.125 Al 0.0625 O3 matrix and Cu filler with a mass content of 19.6%.

[0072] The difference between the preparation method of the EuTiO3-based composite material in this embodiment and that in Example 2 is that the copper plating time in step (1) is controlled at 40 min. The mass content of Cu in the prepared EuTiO3-based composite material is 19.6%.

[0073] Comparative Example 1

[0074] An EuTiO3-based material is prepared as follows:

[0075] (1) Green body forming: EuTi with a particle size of 100-300μm is formed. 0.8125 Nb 0.125 Al 0.0625 O3 micro powder was pressed into a green body under a pressure of 600MPa;

[0076] (2) High-temperature sintering: The green blank obtained in step (1) is sintered in a furnace with a hydrogen-argon mixed atmosphere (10 vol% hydrogen and 90 vol% argon) at a temperature of 800°C for 6 h to obtain EuTiO3-based material, wherein the mass content of Cu is 0.

[0077] Comparative Example 2

[0078] A composite material comprising EuTi 0.8125 Nb 0.125 Al 0.0625 O3 matrix and Cu filler with a mass content of 25.4%.

[0079] The only difference between the preparation method of the composite material in Comparative Example 2 and Example 2 is that the copper plating time in step (1) is controlled at 50 min, so that the mass content of Cu in the composite material is 25.4%.

[0080] Example 1

[0081] To comprehensively evaluate the performance of the EuTiO3-based composite material provided by this invention, and to investigate the magnetocaloric effect of the materials in the examples and comparative examples under low temperature and low magnetic field conditions, as well as the thermal conductivity of the materials in the liquid helium temperature range, the following tests were conducted:

[0082] 1. Using the Quantum Design, Inc. Integrated Physical Property Measurement System (PPMS), the thermal conductivity of the samples was tested by thermal transport (TTO) to determine the change in thermal conductivity with temperature. Thermal conductivity curves were plotted, and the thermal conductivity of the materials in each embodiment and comparative example at the liquid helium temperature (4.2K) was obtained.

[0083] 2. Based on Maxwell's relation, the isothermal magnetization curves of the materials at different temperatures were measured, and the magnetic entropy change under different magnetic field changes was calculated. The magnetic entropy change curves of each embodiment and comparative material under different magnetic field changes were obtained respectively.

[0084] 3. The microstructure and corresponding EDS surfaces of the green blanks and composite materials obtained during the preparation process of each embodiment were observed and analyzed by scanning electron microscopy and EDS surface analysis.

[0085] Figure 1 The graph shows the thermal conductivity of the EuTiO3-based composite materials in Examples 1, 2, and 3 of this invention, and the pure EuTiO3 matrix material prepared in Comparative Example 1, as a function of temperature in the liquid helium temperature range.

[0086] Figure 2 The magnetic entropy changes of the EuTiO3-based composite materials in Examples 1, 2, and 3 of this invention under different magnetic field variations (0-1T and 0-2T) are shown.

[0087] Figure 3 The images shown are scanning electron microscope (SEM) images and corresponding EDS (Electro-Measuring Spectroscopy) diagrams of the Cu / EuTiO3-based composite micropowder prepared by chemical plating in Example 1 of this invention. Figure 3 -(a) is a scanning electron microscope image. Figure 3 -(c)-(d) are the corresponding EDS surface analysis plots. Figure 3 -(b) is Figure 3 -(a) Microstructure diagram.

[0088] from Figure 3 It can be observed that the Cu coating particles are uniformly and densely distributed on the EuTiO3 surface in a cellular structure, and the cellular structure of the Cu particles has obvious boundaries.

[0089] Figure 4 The images shown are scanning electron microscope (SEM) images and corresponding EDS (Electronics Displacement Spectroscopy) diagrams of the EuTiO3-based composite green body from Example 1 of this invention. Figure 4 -(a) is a scanning electron microscope image. Figure 4 -(b)-(c) are the corresponding EDS surface analysis diagrams.

[0090] according to Figure 4 It can be seen that after Cu plating, the formation of the Cu / EuTiO3 shell / core structure can be clearly observed in the green blank, and the Cu plating layer is uniformly coated on the surface of the EuTiO3-based micro powder.

[0091] Figure 5 The images show scanning electron microscope (SEM) images and corresponding EDS surface analysis diagrams of the EuTiO3-based composite materials in Examples 1, 2, and 3 of this invention. Figure 5 (a)-(c), (d)-(f) and (g)-(i) in the examples correspond to Example 1, Example 2 and Example 3, respectively.

[0092] from Figure 5As can be seen, at different sintering temperatures, in Examples 1-3, each EuTiO3 matrix was surrounded by a continuous and dense Cu network, which is beneficial for obtaining excellent thermal properties.

[0093] Table 1 below summarizes the test results of the magnetocaloric and thermal conductivity properties of the materials in the embodiments and comparative examples of the present invention. According to Table 1 and the figures:

[0094] (1) The thermal conductivity of the composite materials provided by the present invention in Examples 1-5 is significantly higher than that of the pure EuTiO3 matrix phase prepared in Comparative Example 1, and also has a certain magnetocaloric effect, indicating that the magnetic refrigeration material provided by the present invention has high thermal conductivity in the liquid helium temperature range and has a certain advantage in heat exchange efficiency.

[0095] (2) From Figure 1 , 2 As shown in Table 1, the Cu / EuTi content obtained under the preparation conditions of Example 2 was 5.2% by mass. 0.8125 Nb 0.125 Al 0.0625 The O3-based composite material exhibits the best thermal conductivity, reaching 4.1 W·m at the liquid helium temperature (4.2 K). -1 K -1 Meanwhile, at 5.5 K, the maximum magnetic entropy change of the EuTiO3-based composite material was 14.4 J·kg⁻¹ when the magnetic field changed to 0-1 T and 0-2 T, respectively. -1 ·K -1 and 23.9 J·kg -1 ·K -1 Compared with other embodiments and comparative examples, it can well balance high thermal conductivity and better magnetocaloric effect, and the overall effect is optimal.

[0096] (3) Comparing Examples 1-3 of the present invention: the magnetic entropy change values ​​of EuTiO3-based composite materials are not much different at different sintering temperatures, but the thermal conductivity reaches the optimal value at a sintering temperature of 800℃.

[0097] (4) Compared to Example 2, in Example 5, by extending the copper plating time and increasing the Cu mass content, the thermal conductivity of the material was significantly improved, but the magnetism was significantly reduced. In Comparative Example 2, further increasing the Cu filler mass content did not significantly improve the thermal conductivity, and the magnetocaloric effect continued to decrease, which may significantly affect the magnetic refrigeration effect of the material. In Comparative Example 1, when the Cu filler content was 0, the magnetocaloric effect was not significantly improved, and the thermal conductivity of the material at the liquid helium temperature (4.2K) was significantly reduced to 0.07 W·m. -1 K -1Therefore, controlling the Cu mass content in EuTiO3-based composite materials within a limited range can ensure that the composite material achieves a significant increase in thermal conductivity while minimizing the loss of magnetocaloric performance, thus balancing good heat transfer efficiency and a large magnetocaloric effect, and has high application value in the field of magnetic refrigeration.

[0098] Table 1. Test results of magnetocaloric and thermal conductivity of the materials in the examples and comparative examples.

[0099]

[0100]

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An EuTiO3-based composite material, characterized in that, It comprises an EuTiO3 matrix and a metal filler; the EuTiO3 matrix is ​​EuTiO3 and / or EuTiO3 doped with metal M, wherein the metal M is at least one selected from Al, Nb, Ta, and Zr; the metal filler is Cu, wherein the mass content of Cu is 2-20%; The preparation method of the EuTiO3-based composite material includes the following steps: (1) The EuTiO3-based micro powder is activated, degellated, and electrolessly copper-plated to obtain composite micro powder; the particle size of the EuTiO3-based micro powder is 100-300 μm; the copper plating solution includes the following components at the following concentrations: 2 g / L anhydrous copper sulfate, 4 g / L formaldehyde, and 10 g / L sodium hydroxide; the temperature of the plating solution is 40 ℃, the pH value is 12.8-12.9; the copper plating time is 12 min, and the copper plating rotation speed is 400 r / min; (2) The composite micro powder is pressed into a green body and then sintered in a protective atmosphere to obtain the EuTiO3-based composite material; the pressing pressure of the green body is 600 MPa, the sintering temperature is 800℃, and the holding time is 6 h.

2. The EuTiO3-based composite material as described in claim 1, characterized in that, The mass content of Cu is 4-6%.

3. The EuTiO3-based composite material as described in claim 1, characterized in that, The maximum magnetic entropy change of the EuTiO3-based composite material under a magnetic field change of 0-1 T is 11.5-15 J·kg. -1 ·K -1 The maximum magnetic entropy change under a magnetic field variation of 0-2 T is 19.5-25 J·kg. -1 ·K -1 .

4. The EuTiO3-based composite material as described in claim 1, characterized in that, The thermal conductivity of the EuTiO3-based composite material is 1.7-6 W·m at 4.2 K. -1 K -1 .

5. The application of the EuTiO3-based composite material as described in any one of claims 1-4 in magnetic refrigeration.

Images