CN112575270B - Hydrogenated heavy rare earth high-entropy composite material and preparation method and application thereof - Google Patents

Hydrogenated heavy rare earth high-entropy composite material and preparation method and application thereof Download PDF

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CN112575270B
CN112575270B CN202011311704.2A CN202011311704A CN112575270B CN 112575270 B CN112575270 B CN 112575270B CN 202011311704 A CN202011311704 A CN 202011311704A CN 112575270 B CN112575270 B CN 112575270B
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沈宝龙
邵里良
薛琳
张耀
袁子蕊
王倩倩
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Abstract

The invention discloses a hydrogenated heavy rare earth high-entropy composite material and a preparation method and application thereof. The chemical formula of the hydrogenated heavy rare earth high-entropy composite material is A in terms of mole percentage of each atom20B18C18Co20Al24HxWherein A, B, C are different from each other and are respectively selected from one of Gd, Tb, Dy, Ho, Er and Tm, and x is larger than 0. The preparation method comprises the following steps: weighing corresponding raw materials according to the chemical molecular formula of the high-entropy composite material; smelting and cooling the raw materials to obtain a master alloy ingot; melting the mother alloy cast ingot into alloy solution, and carrying out suction casting to obtain a high-entropy amorphous alloy bar; crushing and ball-milling the bar to obtain high-entropy amorphous alloy powder; the powder is subjected to isothermal hydrogen absorption treatment to prepare the hydrogenated heavy rare earth high-entropy composite material. The invention induces the amorphous matrix to separate out rare earth hydride by carrying out isothermal hydrogen absorption treatment on the high-entropy amorphous alloy, greatly improves the magnetic entropy change of the alloy and obviously reduces the hysteresis loss of the alloy. The hydrogenated heavy rare earth high-entropy composite material can be used as a magnetic refrigeration working medium.

Description

Hydrogenated heavy rare earth high-entropy composite material and preparation method and application thereof
Technical Field
The invention relates to a high-entropy amorphous alloy, a preparation method and application thereof, in particular to a hydrogenated heavy rare earth high-entropy composite material, a preparation method and application thereof, and belongs to the field of magnetic refrigeration.
Background
In recent years, magnetic refrigeration technology based on the magnetocaloric effect has received much attention from researchers. Compared with the traditional air compression refrigeration technology, the magnetic refrigeration has the advantages of high refrigeration efficiency, environmental protection, no pollution, low vibration noise and the like, has wide application prospect in the refrigeration fields of refrigerators, air conditioners, precise instruments, aerospace and the like, and is known as the refrigeration technology of twenty-first century. The core of the magnetic refrigeration technology is a magnetic refrigeration working medium, and after decades of research, scientists explore and prepare a plurality of magnetic refrigeration materials, such as GdSiGe, MnFePAs (Ga), LaFeSi and other series of alloys, which all show giant magnetocaloric effect and show large magnetic entropy change near the Curie temperature. However, the alloy systems are all primary magnetic phase change materials, and have narrower phase change temperature regions, larger hysteresis loss and lower refrigeration capacity. In addition, the crystal structure of some single-phase compounds needs to be subjected to heat treatment for 30 days, so that the production cost is greatly increased, and the industrial development and application of the single-phase compounds are limited.
Compared with a crystal material, the amorphous magnetic refrigeration material with the secondary magnetic phase change characteristic has a wider magnetic transition temperature region, smaller magnetic hysteresis and thermal hysteresis, relatively larger magnetic entropy change value and high magnetic refrigeration capacity due to the disordered atomic structure. In addition, the amorphous magnetic refrigeration material also has the advantages of high resistivity, small eddy, adjustable phase transition temperature, good mechanical property, high wear resistance, high corrosion resistance and the like, and can well meet the application requirements of the magnetic refrigeration working medium. Among a plurality of amorphous magnetic refrigeration materials, the performance of the heavy rare earth-based amorphous alloy is particularly outstanding, and Gd, Tb, Dy, Ho, Er and Tm-based amorphous alloy magnetic refrigeration systems have been developed. It is worth noting that in recent years, researchers have introduced the concept of high entropy into amorphous alloys to design a series of heavy rare earth high entropy amorphous alloy systems, typically Gd20Tb20Dy20Co20Al20、Gd20Dy20Er20Co20Al20、Gd25Ho10Y15Co25Al25Five members such as Gd10Tb10Dy1 0Ho10Er10Y10Ni10Co10Ag10Al10A ten-element high-entropy amorphous alloy. The high-entropy amorphous alloy enriches the components of the heavy rare earth-based amorphous alloy, and meanwhile, the replacement of a proper rare earth principal element is beneficial to optimizing the alloy performance, reducing the material cost and promoting the development and application of amorphous magnetic refrigeration materials.
Chinese patent application CN105296893A discloses a high-entropy amorphous alloy, a preparation method and application thereof. The chemical composition of the alloy is A20B20C20T20Al20Wherein A, B, C are different from each other and are respectively selected from one heavy rare earth element of Gd, Tb, Dy, Ho, Er and Tm, and T is selected from one element of Fe, Co and Ni. However, the maximum magnetic entropy change of most components in the system under the condition of 5T external magnetic field is less than 10J kg-1K-1And is relatively low.
Therefore, how to effectively improve the magnetic entropy change of the heavy rare earth high-entropy amorphous alloy has important significance for the practical application of the heavy rare earth high-entropy amorphous alloy as a magnetic refrigeration material.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problem that the magnetic entropy change of the existing heavy rare earth high-entropy amorphous alloy is lower, the invention provides a hydrogenated heavy rare earth high-entropy composite material, and the precipitation of rare earth hydride can greatly improve the magnetic entropy change of the amorphous alloy; meanwhile, a preparation method of the hydrogenated heavy rare earth high-entropy composite material is also provided; in addition, the invention also provides an application of the hydrogenated heavy rare earth high-entropy composite material as a magnetic refrigeration working medium.
The technical scheme is as follows: the invention relates to a hydrogenated heavy rare earth high-entropy composite material, and the chemical molecular formula of the high-entropy composite material is A in terms of the mole percentage of each atom20B18C18Co20Al24HxWherein A, B, C are different from each other and are respectively selected from one of Gd, Tb, Dy, Ho, Er and Tm, and x is larger than 0. In the composite material, rare earth hydride (such as GdH) is formed between hydrogen and part of heavy rare earth element2) Thereby obviously improving the magnetic entropy change of the high-entropy amorphous alloy material; and with the increase of the hydrogen content, the magnetic entropy of the composite material gradually increases until the hydrogen content is saturated and then is kept stable.
Optionally, A, B, C is Gd, Tb, Dy respectively, and the high-entropy amorphous alloy has better forming capability at this time. When A, B, C is Gd, Tb and Dy respectively, preferably, x is more than or equal to 43.2, and the magnetic entropy change of the hydrogenated heavy rare earth high-entropy composite material under the condition of 5T external magnetic field is more than 10J kg-1K-1. More preferably, x is not less than 43.2 and not more than 130.65, the hydrogen absorption content is further increased, and when x is 130.65, the maximum magnetic entropy change of the hydrogenated heavy rare earth high-entropy composite material under a 5T external magnetic field can reach 13.6J kg-1K-1(ii) a At the moment, the hydrogen absorption does not reach a saturated state, the isothermal time is prolonged, and the hydrogen absorption can be further carried out, so the value of x can be further improved, and the hydrogen absorption can be feasible within the range that x is more than 0 and less than or equal to 140.
The invention relates to a preparation method of a hydrogenated heavy rare earth high-entropy composite material, which comprises the following steps:
(1) according to the chemical formula A of the high-entropy composite material20B18C18Co20Al24Weighing corresponding raw materials;
(2) smelting the weighed raw materials, and cooling to obtain a master alloy ingot with uniform components;
(3) melting the obtained master alloy ingot into alloy liquid, and sucking the alloy liquid into a water-cooling copper mold to obtain a heavy rare earth high-entropy amorphous alloy bar;
(4) crushing and ball-milling the obtained high-entropy amorphous alloy bar to obtain high-entropy amorphous alloy powder;
(5) and carrying out isothermal hydrogen absorption treatment on the obtained high-entropy amorphous alloy powder to prepare the hydrogenated heavy rare earth high-entropy composite material.
In the step (1), the purity of the heavy rare earth raw material is not less than 99.9 wt.% (wt.%), and the purity of Co and Al elements is not less than 99.99 wt.%.
In the step (2), the smelting process may be: putting the raw materials into an electric arc melting furnace, closing the cavity, and vacuumizing the cavity to 3 multiplied by 10-3Introducing high-purity argon for protection below Pa; firstly, smelting a titanium ingot to further remove residual oxygen in a cavity, then smelting the alloy ingot for six times by using low current and high current in sequence, and then naturally cooling to room temperature to obtain a master alloy ingot with uniform components and small burning loss.
In the step (3), the preparation of the heavy rare earth high-entropy amorphous alloy bar specifically comprises the following steps: removing surface impurities from the mother alloy cast ingot, cleaning, crushing, placing into a water-cooling copper mold of suction casting equipment, closing the cavity, and vacuumizing to vacuum5×10- 3And introducing high-purity Ar gas below Pa, turning on a power supply and gradually increasing the current intensity in the inert gas protection atmosphere until the alloy ingot is melted into alloy melt, and then sucking the alloy melt into a water-cooling copper mold by utilizing the air pressure difference to obtain the heavy rare earth high-entropy amorphous alloy bar. When the chemical molecular formula of the high-entropy composite material is Gd20Tb18Dy18Co20Al24And meanwhile, the forming capability of the high-entropy amorphous alloy is excellent, and the block amorphous alloy with the diameter of 3mm can be prepared.
In the step (4), the preparation process of the high-entropy amorphous alloy powder may include: firstly, crushing a high-entropy amorphous alloy bar into small pieces, then putting the small pieces into a ceramic ball milling tank, and carrying out ball milling according to a ball-material ratio of 15: 1; preferably, the ball mill is set at a speed of 200 revolutions per minute and stopped for 5 minutes per ten minutes of revolution to ensure that the temperature of the milling jar does not rise to affect the amorphous structure of the sample for a total milling time (without rest) of 5 hours. And after ball milling, taking out powder obtained by ball milling, and sieving the powder by a 200-mesh sieve to obtain the high-entropy amorphous alloy powder with the particle size of less than 200 meshes.
Preferably, in the step (5), the isothermal hydrogen absorption treatment process may be: and (3) placing the high-entropy amorphous alloy powder obtained in the step (4) in a hydrogen absorption device under the protection of high-purity argon, setting the hydrogen pressure of a cavity to be 1-5 MPa, heating the sample to be below the glass transition temperature of the high-entropy amorphous alloy, preserving the heat, carrying out isothermal treatment, and controlling the isothermal time to obtain the hydrogenated heavy rare earth high-entropy composite materials with different hydrogen contents. The isothermal temperature adopted by the invention is below the glass transition temperature, and the crystallization of the amorphous alloy is very small after the isothermal temperature is kept for a long time at the temperature, so that the better magnetocaloric property can be maintained; preferably, the isothermal temperature may be 200 to 280 ℃. Furthermore, the isothermal time is not less than 12h, the longer the isothermal time is, the higher the hydrogen content is, when the isothermal time is 12h, the mass fraction of absorbed hydrogen is 0.4%, and the magnetic entropy change of the obtained hydrogenated heavy rare earth high-entropy composite material can be improved by more than 30% and is more than 10J kg- 1K-1。
The application of the hydrogenated heavy rare earth high-entropy composite material is to use the hydrogenated heavy rare earth high-entropy composite material as a magnetic refrigeration working medium.
Has the advantages that: compared with the prior art, the invention has the advantages that: (1) the invention induces the amorphous matrix to separate out rare earth hydride (such as GdH) by carrying out isothermal hydrogen absorption treatment on the high-entropy amorphous alloy2) Greatly improves the magnetic entropy change of the alloy, and the maximum magnetic entropy change reaches 13.6J kg under the 5T external field-1K-1The improvement is over 50 percent; meanwhile, the hysteresis loss of the alloy is obviously reduced; (2) the five main elements of the heavy rare earth high-entropy amorphous alloy are designed in unequal atomic ratio, have better amorphous forming capacity, can be used for preparing the block amorphous alloy with the diameter of 3mm, is superior to most of reported heavy rare earth high-entropy amorphous alloys, and is convenient for subsequent treatment.
Drawings
FIG. 1 is Gd prepared by mechanical ball milling20Tb18Dy18Co20Al24A DSC curve of the high-entropy amorphous alloy powder, and an inset is an XRD (X-ray diffraction) spectrum of the amorphous powder prepared by 2mm amorphous blocks and mechanical ball milling;
FIG. 2 is Gd prepared by mechanical ball milling20Tb18Dy18Co20Al24SEM pictures of high-entropy amorphous alloy powder;
FIG. 3 is Gd prepared by mechanical ball milling20Tb18Dy18Co20Al24The particle size distribution diagram of the high-entropy amorphous alloy powder;
FIG. 4 is a graph of Gd prepared in comparative example and example 120Tb18Dy18Co20Al24And Gd20Tb18Dy18Co20Al24H130.65XRD pattern of high entropy powder sample;
FIG. 5 is a graph of Gd prepared in comparative example and example 120Tb18Dy18Co20Al24And Gd20Tb18Dy18Co20Al24H130.65The magnetization curves of the high-entropy powder sample are subjected to Field Cooling (FC) and Zero Field Cooling (ZFC), and the external field is 0.01T;
FIG. 6 is a graph of Gd prepared in comparative example and example 120Tb18Dy18Co20Al24And Gd20Tb18Dy18Co20Al24H130.65A hysteresis loop curve of the high-entropy powder sample, and the test temperature is 5K;
FIG. 7 Gd prepared in comparative example20Tb18Dy18Co20Al24Isothermal magnetization curve of high entropy powder sample;
FIG. 8 is Gd prepared as a comparative example20Tb18Dy18Co20Al24The magnetic entropy change curve of the high-entropy powder sample;
FIG. 9 is Gd prepared in example 120Tb18Dy18Co20Al24H130.65Isothermal magnetization curve of high entropy powder sample;
FIG. 10 is Gd prepared in example 120Tb18Dy18Co20Al24H130.65The magnetic entropy change curve of the high-entropy powder sample;
FIG. 11 is Gd prepared in example 220Tb18Dy18Co20Al24H43.2XRD pattern of high entropy powder sample;
FIG. 12 is Gd prepared in example 220Tb18Dy18Co20Al24H43.2Isothermal magnetization curve of high entropy powder sample;
FIG. 13 is Gd prepared in example 220Tb18Dy18Co20Al24H43.2Magnetic entropy change curve of high entropy powder sample.
Detailed Description
The technical solution of the present invention is further explained with reference to the drawings and the embodiments.
Unless otherwise specified, other materials and raw materials used in the present invention are all conventional materials which are commercially available. The equipment used is also conventional in the art. Operations not mentioned in the present invention are all those conventional in the art.
The test apparatus used in the examples was as follows:
(1) preparing high-entropy amorphous alloy powder by using a planetary ball mill;
(2) carrying out an isothermal hydrogen absorption experiment by using a Sieverts type gas-solid reaction testing device;
(3) determining the amorphous structure of the prepared sample by using an X-ray diffractometer (XRD);
(4) characterizing the particle size morphology of the prepared powder sample by using a Scanning Electron Microscope (SEM);
(5) measuring the thermal property of the heavy rare earth high-entropy amorphous alloy by using a Differential Scanning Calorimeter (DSC), heating a heavy rare earth high-entropy amorphous alloy sample at a heating rate of 20K/min until the heavy rare earth high-entropy amorphous alloy sample is completely crystallized, and calibrating the glass transition temperature (T)g) Initial crystallization temperature (T)x) To obtain the width Delta T of the supercooled liquid phase regionx(ΔTx＝Tx-Tg) To evaluate the thermal stability of the heavy rare earth block high-entropy amorphous alloy;
(6) measuring the temperature-rising magnetization curve (with field and zero field) and isothermal magnetization curve of the heavy rare-earth-based amorphous alloy by using a magnetic measurement system (MPMS), and calculating to obtain the Curie temperature (T) of the sampleC) And magnetic entropy change (Δ S)M). The calculation process of the relevant parameters is described in the literature Annu.Rev.Mater.Sci.2000(30): 387-429.
Example 1
Preparation of chemical formula Gd20Tb18Dy18Co20Al24H130.65The heavy rare earth high-entropy composite material.
The preparation process comprises the following steps:
step 1, Gd, Tb, Dy, Co and Al raw materials with the purity of more than 99.9 wt.% are mixed according to the molecular formula of Gd20Tb18Dy18Co20Al24Proportioning according to the atomic percentage;
step 2, putting the raw materials weighed in the step 1 into a water-cooled copper crucible of an electric arc melting furnace, closing the cavity, and firstly vacuumizing the cavity to 3 multiplied by 10-3Introducing high-purity argon for protection to smelt under Pa, smelting a titanium ingot for 3-5 min to further remove residual oxygen in the cavity, smelting the alloy ingot twice at low current (150-180A), smelting the alloy ingot four times at high current (270-300A), turning over the alloy ingot before smelting each time, and then smelting the alloy ingot at high current (270-300A) againNaturally cooling for 30min to obtain a master alloy ingot with uniform components and small burning loss;
step 3, removing surface impurities from the mother alloy ingot obtained in the step 2, cleaning the mother alloy ingot, crushing the mother alloy ingot into small alloy ingots, putting the alloy ingots into a water-cooled copper crucible of a suction casting furnace, closing a cavity, and vacuumizing the cavity to 5 multiplied by 10-3And introducing high-purity argon under Pa, adjusting the pressure difference to be 0.05MPa, setting the temperature of cooling water to be 10 ℃, starting a power supply and gradually increasing the current intensity until the alloy ingot is molten in the inert gas protection atmosphere, and sucking the molten alloy liquid into a water-cooling copper mold with the diameter of 2mm by utilizing the pressure difference to obtain the heavy rare earth high-entropy amorphous alloy 2mm bar.
As shown in the inset branch of FIG. 1, the XRD pattern of the heavy rare earth high-entropy amorphous alloy 2mm bar shows that the curve shows two diffraction peaks which are widely dispersed, and no sharp crystallization peak exists, which indicates that the alloy bar is of a typical amorphous structure.
And 4, smashing the high-entropy block amorphous alloy bar material with the diameter of 2mm prepared in the step 3 into small fragments, putting about 2g of amorphous sample and 30g of ceramic grinding balls into a 50ml ceramic ball milling tank, and carrying out ball milling according to the ball-to-material ratio of 15: 1. The ball mill is set to rotate at 200 revolutions per minute and stopped for 5 minutes every ten minutes to ensure that the temperature of the ball milling tank does not rise to affect the amorphous structure of the sample, and the total ball milling time (without rest) is 5 hours. And taking out the powder subjected to ball milling, and sieving the powder by using a 200-mesh metal sieve to obtain a high-entropy amorphous alloy powder sample with the particle size of less than 200 meshes.
As shown in the inset diagram branch of FIG. 1, the XRD pattern of the high-entropy amorphous alloy powder sample shows that the curve shows two widely dispersed diffraction peaks without any sharp crystallization peak, which indicates that the alloy rod is of a typical amorphous structure.
SEM pictures and corresponding particle size distribution diagrams of the high-entropy amorphous alloy powder are shown in figures 2 and 3, and the average particle size of the prepared powder is about 41 mu m.
A Differential Scanning Calorimeter (DSC) is used for measuring the thermal property of the high-entropy amorphous alloy powder, a DSC curve (the temperature rise rate is 20K/min) is shown in figure 1, a sample shows obvious glass transition process (broad endothermic peak) and crystallization process (sharp exothermic peak), the glass transition temperature is 606K, and the width of a supercooled liquid phase region is 72K, which shows that the amorphous alloy has better thermal stability.
And 5, placing the high-entropy amorphous alloy powder prepared in the step 4 in a hydrogen absorption device under the protection of high-purity argon, setting the hydrogen pressure of a cavity to be 5MPa, heating the sample to 265 ℃, preserving the temperature, and carrying out isothermal treatment for 40 h. The mass fraction of the absorbed hydrogen is 1.2 percent, and the molecular formula of the obtained hydrogenated heavy rare earth high-entropy composite material is Gd after being converted into the atomic percent20Tb18Dy18Co20Al24H130.65。
Comparative example
Preparation of Gd formula according to the procedure of example 120Tb18Dy18Co20Al24The high-entropy amorphous alloy of (2).
The difference is that in the step 5, the high-entropy amorphous alloy powder prepared in the step 4 is placed in a hydrogen absorption device under the protection of high-purity argon, the pressure of hydrogen in a cavity is set to be 0MPa, the temperature of the sample is raised to 265 ℃, the temperature is kept, isothermal treatment is carried out, the isothermal time is 40h, and Gd is obtained20Tb18Dy18Co20Al24High entropy amorphous alloy powder.
XRD patterns of the high-entropy powders prepared in the comparative example and the example 1 are shown in figure 4, and it can be seen that after long-time isothermal annealing treatment, a small amount of REAL and RECo (RE stands for rare earth element) crystallization phases are precipitated on an amorphous matrix, and a sample after hydrogen absorption treatment precipitates rare earth hydride GdH2And (4) crystallizing.
The magnetic properties of the amorphous alloy are measured by MPMS:
comparative example Gd20Tb18Dy18Co20Al24High entropy alloy powder and example 1Gd20Tb18Dy18Co20Al24H130.65The magnetization curves of the hydrogenated high-entropy alloy powder under the belt field and zero field cooling are shown in FIG. 5, and it can be seen that the samples of the comparative example and the example 1 show obvious ferromagnetic to paramagnetic transition along with the temperature increase. The Curie temperature of the sample before and after hydrogen absorption is obtained by calculating the first derivative of the magnetization curveThe degrees are 59K and 8K, respectively, as shown in Table 1.
The hysteresis loops of the high-entropy alloy powders prepared in the comparative example and the example 1 at 5K are tested, as shown in FIG. 6, and as can be seen from FIG. 6, the coercive force of the heavy rare earth high-entropy composite powder after hydrogen absorption is greatly reduced, and the hysteresis loss in the magnetic transformation process is obviously reduced.
Comparative example Gd20Tb18Dy18Co20Al24High entropy alloy powder and example 1Gd20Tb18Dy18Co20Al24H130.65The isothermal magnetization curves of the hydrogenated high entropy alloy powders are shown in fig. 7 and 9, respectively, and it can be seen that the samples of the comparative example and example 1 both exhibit a distinct ferromagnetic to paramagnetic transition with increasing temperature.
Based on the isothermal magnetization curves, the variation curves of the magnetic entropy change with the temperature of the high-entropy powder samples of the comparative example and the example 1 can be calculated through a Maxwell relationship, and are respectively shown in FIGS. 8 and 10. It can be seen that the magnetic entropy change of the sample after hydrogen absorption is obviously improved, and the maximum magnetic entropy change under the 5T external field is 8.8J kg-1K-1Lifting to 13.6J kg-1K-1The improvement is nearly 55%.
Example 2
With reference to example 1, preparation of a compound having the chemical formula Gd20Tb18Dy18Co20Al24H43.2The heavy rare earth high-entropy composite material.
The difference lies in step 5: and (3) placing the high-entropy amorphous alloy powder prepared in the step (4) in a hydrogen absorption device under the protection of high-purity argon, setting the hydrogen pressure of a cavity to be 5MPa, heating the sample to 265 ℃, preserving the temperature, and carrying out isothermal hydrogen absorption for 12 hours. The mass fraction of the absorbed hydrogen is 0.4 percent, and the molecular formula of the obtained hydrogenated heavy rare earth high-entropy composite material is Gd after being converted into the atomic percent20Tb18Dy18Co20Al24H43.2。
The XRD pattern of the hydrogenated high-entropy amorphous alloy powder is shown in FIG. 11, and similar to the sample obtained in example 1, GdH is precipitated on the amorphous matrix after long-time isothermal hydrogen absorption2And (4) phase(s).
The magnetic properties of the samples were measured by PPMS, and the isothermal magnetization curve and the corresponding magnetic entropy change curve are shown in FIGS. 12 and 13, respectively, and the associated magnetic properties are shown in Table 1. Gd compared to comparative example20Tb18Dy18Co20Al24After a small amount of hydrogen is absorbed by the high-entropy amorphous alloy powder, the Curie temperature and the coercive force are greatly reduced, and the magnetic entropy change reaches 11.7J kg-1K-1And the improvement is 33 percent.
TABLE 1 magnetic properties of high-entropy amorphous alloy samples obtained in comparative examples and examples 1-2
Figure BDA0002790014060000071
As is clear from the above examples, when A, B, C is Gd, Tb or Dy, respectively, A is effectively increased by the hydrogen absorption treatment20B18C18Co20Al24The magnetic entropy of the high-entropy amorphous alloy changes. Because the properties of Gd, Tb, Dy, Ho, Er and Tm are similar to those of several heavy rare earth elements, REH is easily formed under the action of hydrogen2Phase (RE refers to one of the above elements) and all have a large hydrogen adsorption capacity, see P.Vajda, Handbook on the Physics and Chemistry of Rare Earth, Amsterdam: North-Holland,1995. it is therefore expected that when A, B, C is selected from the other elements Gd, Tb, Dy, Ho, Er, Tm, A can be effectively increased by hydrogen adsorption treatment20B18C18Co20Al24The magnetic entropy of the high-entropy amorphous alloy changes.

Claims (5)

1. The hydrogenated heavy rare earth high-entropy composite material is characterized in that the chemical molecular formula of the high-entropy composite material is A in terms of mole ratio of each atom20B18C18Co20Al24HxWherein A, B, C is Gd, Tb and Dy respectively; x is more than or equal to 43.2 and less than or equal to 130.65; the preparation method of the hydrogenated heavy rare earth high-entropy composite material comprises the following steps:
(1) according to the chemical formula A of the high-entropy alloy20B18C18Co20Al24Weighing corresponding raw materials;
(2) smelting the weighed raw materials, and cooling to obtain a master alloy ingot with uniform components;
(3) melting the master alloy ingot into alloy liquid, and sucking the alloy liquid into a water-cooling copper mold to obtain a heavy rare earth high-entropy amorphous alloy bar;
(4) crushing and ball-milling the high-entropy amorphous alloy bar to obtain high-entropy amorphous alloy powder;
(5) and carrying out isothermal hydrogen absorption treatment on the high-entropy amorphous alloy powder to prepare the hydrogenated heavy rare earth high-entropy composite material.
2. A hydrogenated heavy rare earth high entropy composite according to claim 1, wherein in step (5), the isothermal hydrogen absorption treatment is: and (3) placing the high-entropy amorphous alloy powder obtained in the step (4) in a hydrogen absorption device under the protection of high-purity argon, setting the hydrogen pressure of a cavity to be 1-5 MPa, then heating to the temperature below the glass transition temperature of the high-entropy amorphous alloy, preserving heat, and carrying out isothermal treatment.
3. The preparation method of the hydrogenated heavy rare earth high-entropy composite material according to claim 2, wherein the high-entropy amorphous alloy powder is heated to 200-280 ℃ and is subjected to heat preservation.
4. The method for preparing a hydrogenated heavy rare earth high entropy composite material according to claim 3, wherein the isothermal treatment time is not less than 12 h.
5. Use of the hydrogenated heavy rare earth high-entropy composite material as defined in claim 1 as a magnetic refrigerant.
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