R-T-Si alloy particles, R-T-Si secondary alloy particles and preparation method and application of R-T-Si secondary alloy particles

Abstract

The invention discloses R-T-Si alloy particles, R-T-Si secondary alloy particles and a preparation method and application of the R-T-Si alloy particles and the R-T-Si secondary alloy particles. In the R-T-Si alloy particles, the atomic ratio of the R to the'T and Si 'is (1-1.1): (13-15.5); the atomic ratio of the T to the Si is (4.4-30): 1; wherein R is one or more of rare earth metal elements; t is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium; the average particle size of the R-T-Si alloy particles ranges from 10 micrometers to 1000 micrometers. The R-T-Si alloy particles have the advantages of being high in sphericity degree, smooth in surface and free of obvious defects, and have good magnetocaloric performance when being applied to the field of solid refrigeration.

Description

[0001] This application claims the priority of Chinese patent application No. 2023118312755 filed on December 27, 2023. This application cites the entire text of the above Chinese patent application. Technical Field

[0002] The present invention specifically relates to RT-Si alloy particles, RT-Si secondary alloy particles and preparation methods and applications thereof. Background Art

[0003] Magnetic refrigeration technology is a new solid-state refrigeration technology based on the magnetocaloric effect of magnetic materials. It has the advantages of high efficiency, energy saving, green environmental protection, and strong reliability. It can be used in low-temperature physics, medical equipment, household appliances and other fields. However, RT-Si alloy particle refrigeration materials still face some technical difficulties in the preparation and processing process, such as: the conventional preparation process requires complex process flow such as smelting, heat treatment, hydrogen absorption, crushing, and processing and molding; and RT-Si materials are prone to defects such as fragility, oxidation, and stress during processing, which affect their structure and performance.

[0004] It is of great significance to overcome the above technical difficulties, develop a new type of RT-Si alloy particle magnetic refrigeration material, and solve the problems of complex preparation process and difficult processing. Summary of the invention

[0005] The present invention mainly provides RT-Si alloy particles, RT-Si secondary alloy particles and their preparation methods and applications in order to overcome the shortcomings and defects of the prior art in preparing RT-Si alloy particles. The RT-Si alloy particles of the present invention have the advantages of high sphericity, smooth surface and no obvious defects. When applied to the field of solid-state refrigeration, they have good magnetocaloric properties.

[0006] To overcome the above-mentioned defects, the present invention provides the following technical solutions.

[0007] The present invention provides an RT-Si alloy particle, wherein the atomic ratio of R to “the T and the Si” is (1-1.1): (13-15.5); the atomic ratio of T to the Si is (4.4-30): 1;

[0008] Wherein, R is one or more rare earth metal elements; T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium; and the average particle size of the RT-Si alloy particles is 10 μm-1000 μm.

[0009] In the present invention, the atomic ratio of the R to “the T and the Si” may be (1.03-1.05):(13-14), for example, 1.03:13, 1.05:13 or 1.05:13.2.

[0010] In some specific embodiments, when the minimum T is 10.6, the corresponding maximum Al is 2.4.

[0011] In some specific embodiments, when the maximum value of T is 15, the corresponding minimum value of Al is 0.5.

[0012] In the present invention, the atomic ratio of the R, the T and the Si is (1.03-1.05):(11-12):(1-2), for example, 1.03:11.5:1.5, 1.03:11.6:1.4, 1.05:11.5:1.5, 1.05:11.8:1.2, 1.05:11.6:1.6, 1.05:11.7:1.5 or 1.05:12:1.2.

[0013] In the present invention, R is one or more of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; preferably, R includes lanthanum; for example, R is lanthanum and cerium, lanthanum and praseodymium, "lanthanum, cerium and praseodymium" or "lanthanum, cerium, praseodymium and neodymium".

[0014] In some preferred embodiments of the present invention, R is lanthanum and cerium, and the atomic ratio of lanthanum and cerium is preferably (2-6):1, for example 0.735:0.315;

[0015] In some preferred embodiments of the present invention, the R is lanthanum and praseodymium, and the atomic ratio of lanthanum and praseodymium is (2-6):1, for example, 0.84:0.21.

[0016] In some preferred embodiments of the present invention, R is lanthanum, cerium and praseodymium, and the atomic ratio of lanthanum, cerium and praseodymium is (2-6):1:1, for example, 0.63:0.21:0.21.

[0017] In some preferred embodiments of the present invention, R is lanthanum, cerium, praseodymium and neodymium, and the atomic ratio of lanthanum, cerium, praseodymium and neodymium is (2-6):2:1:1, for example, 0.63:0.21:0.105:0.105.

[0018] In the present invention, the T includes one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium; preferably, the T includes iron, for example, the T is iron, "iron and manganese", "iron and cobalt" or "iron, manganese and cobalt".

[0019] In some preferred embodiments of the present invention, the T is iron and manganese, and the atomic ratio of iron to manganese is (30-40):1, for example, 11.2:0.3.

[0020] In some preferred embodiments of the present invention, T is iron and cobalt, and the atomic ratio of iron to cobalt is (10-15):1, for example, 11:0.8.

[0021] In the present invention, the relative purity of R may be ≥99wt%, preferably ≥99.5wt%.

[0022] In some specific embodiments of the present invention, R is lanthanum, T is iron, and the atomic ratio of lanthanum, iron and silicon is (1.03-1.05):11.5:1.5, for example, 1.05:11.5:1.5, 1.03:11.5:1.5 or 1.03:11.6:1.4.

[0023] In some specific embodiments of the present invention, R is lanthanum and cerium, T is iron, and the atomic ratio of lanthanum, cerium, iron and silicon is (0.6-0.8): (0.2-0.4): (11.5-12): 1.5, for example 0.735: 0.315: 11.5: 1.5 or 0.735: 0.315: 11.7: 1.5.

[0024] In some specific embodiments of the present invention, R is lanthanum and praseodymium, T is iron, and the atomic ratio of lanthanum, praseodymium, iron and silicon is (0.7-0.9): (0.1-0.3): (11.5-12): (1-1.5), for example 0.84:0.21:11.5:1.5 or 0.84:0.21:11.7:1.5.

[0025] In some specific embodiments of the present invention, R is lanthanum, T is iron and cobalt, and the atomic ratio of lanthanum, iron, cobalt and silicon is 1.05: (10.9-11.1): (0.7-0.9): 1.2, for example, 1.05: 11: 0.8: 1.2 or 1.05: 11.1: 0.9: 1.2.

[0026] In some specific embodiments of the present invention, R is lanthanum, T is iron and manganese, and the atomic ratio of lanthanum, iron, manganese and silicon is 1.05: (11.1-11.3): (0.2-0.4): 1.5, for example, 1.05: 11.2: 0.3: 1.5 or 1.05: 11.3: 0.2: 1.5.

[0027] In some specific embodiments of the present invention, R is lanthanum, cerium and praseodymium, T is iron, and the atomic ratio of lanthanum, cerium, praseodymium, iron and silicon is 0.63:0.21:0.21:11.5:1.5.

[0028] In some specific embodiments of the present invention, R is lanthanum, cerium, praseodymium and neodymium, T is iron, and the atomic ratio of lanthanum, cerium, praseodymium, neodymium, iron and silicon is 0.63:0.21:0.105:0.105:11.5:1.5.

[0029] In some specific embodiments of the present invention, R is lanthanum and cerium, T is iron and cobalt, and the atomic ratio of lanthanum, cerium, iron, cobalt and silicon is 0.84:0.21:11:0.8:1.2.

[0030] In some specific embodiments of the present invention, R is lanthanum and cerium, T is iron and manganese, and the atomic ratio of lanthanum, cerium, iron, manganese and silicon is 0.735:0.315:11.2:0.3:1.5.

[0031] The present invention also provides a method for preparing the RT-Si alloy particles as described above, which comprises the following steps: subjecting a substrate to a plasma rotating electrode atomization method to obtain the RT-Si alloy particles;

[0032] Wherein, the substrate includes R, T and Si, the atomic ratio of R to "the T and the Si" is 1:(11.8-15.5); the atomic ratio of T to the Si is (4.4-30):1; wherein, R is one or more rare earth metal elements; and T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium.

[0033] In the present invention, the plasma rotating electrode atomization method is carried out in a plasma rotating electrode atomization device.

[0034] In some specific embodiments of the present invention, the rotation speed of the substrate may be 500 rpm-30000 rpm, preferably 1500 rpm-26000 rpm, for example 1500 rpm, 2500 rpm, 4000 rpm, 12000 rpm or 26000 rpm.

[0035] The working current varies along the radial direction of the cross section of the substrate, and the working current is the total current of the plasma rotating electrode atomization device.

[0036] In some specific embodiments of the present invention, when the cross-section of the substrate is at the center, the operating current is 800-3000A, such as 800A, 1400A, 1600A, 2100A or 2600A.

[0037] In some specific embodiments of the present invention, at a quarter of the diameter of the cross section of the substrate, the operating current is 600-3000 A, such as 600 A, 800 A, 900 A, 1100 A or 1400 A. In the present invention, "a quarter of the diameter of the cross section" is based on the edge of the cross section.

[0038] In the present invention, the feeding speed of the substrate may be 1-10 mm / s, preferably 1-5 mm / s, such as 1.5 mm / s.

[0039] In the present invention, the plasma rotating electrode atomization device used in the plasma rotating electrode atomization method includes an electrode rotating and sealing device, a pushing device, a plasma gun head, an atomization chamber, an inert gas environment and a collector. The plasma rotating electrode atomization method (PREP method) is a metal powder preparation method based on the principle of high-speed rotating centrifugal atomization of electrode rods. This method can prepare metal powders with low oxygen content, no adhesion and high sphericity. The rare earth-transition metal-silicon-based alloy spherical working fluid material required for magnetic refrigeration technology prepared by the plasma rotating electrode atomization method maintains an excellent magnetocaloric effect, has a high specific surface area and a high heat exchange effect, and solves the problems of complex preparation process, high processing difficulty, poor material stability and low cycle life.

[0040] The rotating device is used to rotate the substrate at a certain speed, and the melted droplets naturally form spherical particles in the process of flying in the air by centrifugal force. The rotating device also includes a sealing device, which can ensure that the electrode can rotate at a high speed and feed smoothly, while ensuring the sealing effect of the cavity.

[0041] The plasma gun head utilizes its own high temperature to melt the surface part of the substrate and splash out to form spherical droplets.

[0042] The pushing device is used to feed the substrate into the equipment cavity at a certain feeding speed, and form a continuous arc between the substrate and the plasma gun head and be in the airflow of the arc. The pushing device can be a single feeder or a continuous feeder, and continuous feeding can be achieved by threaded connection with the matching rod.

[0043] The shape of the collector is preferably cylindrical or conical; the inner wall of the collector is preferably made of non-sticky material; an outlet is provided at the bottom for collecting RT-Si alloy particles. The chamber of the collector is preferably circular or conical; the width of the chamber of the collector is preferably 100 mm-2000 mm; and the diameter of the chamber is preferably 1000 mm-4000 mm.

[0044] In the present invention, the vacuum degree in the atomization chamber can be ≤1×10 -2 Pa.

[0045] In the present invention, the oxygen content in the atomization chamber is ≤50ppm, preferably ≤5ppm;

[0046] In the present invention, the preparation is carried out in an inert gas environment. The inert gas environment is conducive to arc starting. The spherical droplets fly and solidify in the inert gas environment. The inert gas environment can protect the spherical droplets from oxidation. At the same time, the heat transfer and heat exchange of the inert gas accelerates the speed at which the droplets solidify into balls during flight, shortens the flight distance, and forms RT-Si alloy particles. The inert environment is conducive to reducing the volume, weight and cost of the equipment.

[0047] The oxygen content in the inert gas is preferably ≤50 ppm, more preferably ≤5 ppm.

[0048] The gas pressure of the inert gas environment is preferably maintained at 0.05 MPa-0.3 MPa; more preferably 0.1 MPa-0.2 MPa, such as 0.12 MPa.

[0049] Wherein, the inert gas is preferably argon and / or helium.

[0050] In the present invention, the center of the plasma gun head may correspond to any position of the cross section of the substrate, such as the center position of the cross section of the substrate or a quarter of the diameter of the cross section of the substrate.

[0051] In the present invention, the substrate can be obtained from the market or by a conventional preparation method in the art; the preparation method of the substrate may include the following steps: the raw material is smelted and cast to obtain an ingot, and the ingot is then machined to obtain the desired size and shape. During the preparation process, the substrate is placed in a plasma rotating electrode atomization device as an electrode. The substrate is a mixture of RT-Si alloy raw materials, which is subsequently atomized by a plasma rotating electrode.

[0052] Wherein, the smelting method can be a vacuum medium frequency induction smelting preparation process.

[0053] The casting mold may be a copper mold or a cast iron mold; the shape of the mold may be selected according to demand, such as square or cylindrical.

[0054] In the present invention, the substrate is in the shape of a rod; the diameter of the rod is preferably 5 mm-150 mm; and the rod is preferably threaded.

[0055] In the present invention, the surface roughness of the substrate is Ra≤1.6 μm.

[0056] The present invention also provides RT-Si alloy particles prepared according to the preparation method as described above.

[0057] The present invention also provides a RT-Si secondary alloy particle, wherein the atomic ratio of R to “the T and the Si” is (1-1.1): (13-15.5); the atomic ratio of T to the Si is (4.4-30): 1;

[0058] Wherein, R is one or more rare earth metal elements; T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium;

[0059] The RT-Si secondary alloy particles contain a main phase, and the main phase is R(TSi) 13 type compound; the RT-Si secondary alloy particles may also contain a heterogeneous phase, and the heterogeneous phase may be at least one of a T element, an R element, an RT compound and an R1T1Si1 type compound; the average particle size of the RT-Si secondary alloy particles is 10μm-1000μm.

[0060] In the present invention, the heterophase may include an α-iron phase.

[0061] When the heterophase includes T element, in the RT-Si secondary alloy particles, a portion of T atoms will form R(TSi) with R and Si. 13 The type compound is the main phase, and the T element is dispersed in the main phase as the impurity phase. The main phase mainly provides magnetocaloric effect performance, and the presence of an appropriate amount of impurity phase can improve the mechanical properties of the material.

[0062] When the heterophase includes R atoms, the R atoms contribute to R(TSi) 13 The formation of this type of compound is more demanding. Once the easily oxidized R atoms react with oxygen and are partially consumed or form compounds with Si and are partially consumed, the amount of R atoms will be insufficient, so it can exist in an appropriate amount.

[0063] The present invention also provides a RT-Si secondary alloy particle, which is obtained by subjecting the above-mentioned RT-Si alloy particle to heat treatment.

[0064] In the present invention, the temperature of the heat treatment may be 1050-1150°C, for example 1050°C or 1120°C.

[0065] In the present invention, the heat treatment holding time may be 12-48 hours, such as 12 hours or 24 hours.

[0066] In some specific embodiments, the heat treatment period can be extended to 7-14 days.

[0067] In the present invention, the equipment and method of heat treatment can be selected conventionally in the art, such as a high vacuum sintering furnace or vacuum packaging in a quartz tube or a tantalum tube.

[0068] In the present invention, after the heat treatment, the cooling method can be selected by conventional methods in the art, such as argon rapid air cooling, water quenching, ice water quenching or liquid nitrogen quenching.

[0069] The present invention also provides RT-Si secondary alloy particles prepared by the above-mentioned preparation method.

[0070] The present invention also provides the use of the RT-Si alloy particles as described above or the RT-Si secondary alloy particles as described above as magnetic refrigeration materials in the field of solid-state refrigeration.

[0071] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0072] The reagents and raw materials used in the present invention are commercially available.

[0073] The positive and progressive effects of the present invention are:

[0074] The RT-Si alloy particles provided by the present invention have the advantages of high sphericity, smooth surface and no obvious defects. When applied to the field of magnetic refrigeration, the RT-Si alloy particles also have good magnetocaloric properties.

[0075] The preparation method provided by the present invention is relatively simple, does not require complicated equipment and operation; does not require additional separation and purification processes; and can adjust the particle size distribution by adjusting parameters such as the rotation speed and working current of the equipment to meet different application requirements with a high yield. The particles prepared by the preparation method of the present invention can solve the material molding problem that is difficult to solve in the prior art. At the same time, the mechanical properties of the material are guaranteed, and it has good corrosion resistance and fast thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 This is a physical picture of the spherical particles obtained in Example 12.

[0077] Figure 2 This is a metallographic image of the spherical particles obtained in Example 12.

[0078] Figure 3 This is the particle size distribution diagram of the spherical particles prepared in Example 12.

[0079] Figure 4 This is the XRD pattern of the RT-Si alloy particles prepared in Example 12.

[0080] Figure 5 This is the XRD pattern of the RT-Si secondary alloy particles prepared in Example 12.

[0081] Figure 6This is a sphericity diagram of the RT-Si alloy particles prepared in Example 12.

[0082] Figure 7 This is the MT diagram of the RT-Si alloy particles prepared in Example 12 measured under a magnetic field of 0.02T.

[0083] Figure 8 This is the MT diagram of the RT-Si alloy particles prepared in Example 12 measured under a magnetic field of 1~3T.

[0084] Fig. 9 This is a graph of the Curie temperature (Tc) of the RT-Si alloy particles prepared in Example 12 under different magnetic fields.

[0085] Fig.10 Magnetic entropy change data diagram of RT-Si alloy particles prepared in Example 12 under different magnetic fields. DETAILED DESCRIPTION

[0086] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0087] Example 1

[0088] La 1.03 Fe 11.5 Si 1.5 The preparation of alloy particles comprises the following steps:

[0089] (1) The lanthanum, iron and silicon raw materials with a relative purity of more than 99wt% are mixed according to the atomic ratio of 1.03:11.5:1.5, and a lanthanum-iron-silicon alloy ingot is prepared by vacuum induction melting and casting. The casting mold is a cast iron mold, and the mold shape can be cylindrical according to the actual size requirements;

[0090] (2) machining the ingot into a lanthanum-iron-silicon alloy rod with a diameter of 30 mm and a surface roughness Ra of no more than 1.6 μm;

[0091] (3) Fix the lanthanum iron silicon alloy rod to the rotating device of the plasma rotating electrode equipment as an electrode, so that the center position of the cross section of one end of the alloy rod is aligned with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also makes the feeding smooth and ensures a good sealing effect;

[0092] (4) Evacuate the chamber of the plasma rotating electrode equipment to a vacuum degree of 1*10 -2 Pa, monitor the oxygen content in the chamber to ensure that the oxygen content in the chamber is less than or equal to 5ppm;

[0093] (5) Close the valve between the vacuum pump and the chamber, open the inert gas valve, and fill the vacuum chamber of the plasma rotating electrode equipment with high-purity argon gas to keep the gas pressure in the chamber at 0.12 MPa;

[0094] (6) Turn on the power and adjust the parameters of the plasma rotating electrode equipment. The feed speed of the rod is 1.5 mm / s; the speed of the rotating device is 26000 rpm; the working current of the equipment is 800 A;

[0095] (7) After the plasma gun head and the electrode strike an arc, a plasma gas flow is sprayed toward the lanthanum iron silicon alloy rod electrode through the plasma gun, so that the end surface of the alloy rod partially melts and splashes out with the rotation of the electrode, forming droplets of lanthanum iron silicon alloy;

[0096] (8) The centrifugal force of the rotating device and the surface tension of the droplets make the droplets naturally form a spherical shape during flight; the electrode rotates, the end surface melts, the droplets splash, and the pushing device continuously feeds, so that the atomization process continues;

[0097] (9) The cooling effect of the inert gas causes the droplets to solidify rapidly during flight to form lanthanum-iron-silicon alloy particles. The inert gas also helps in arc starting.

[0098] (10) The lanthanum iron silicon alloy particles are collected by a collector.

[0099] The lanthanum iron silicon alloy particles prepared in this example have high sphericity, a smooth surface, no obvious defects, controllable particle size and uniform distribution, D50 is 36 μm, and the yield of lanthanum iron silicon alloy particles is 78 wt %.

[0100] Example 2

[0101] Metal Alloy La 0.735 Ce 0.315 Fe 11.5 Si 1.5 The preparation of spherical particles comprises the following steps:

[0102] (1) Raw materials of lanthanum, cerium, iron and silicon with a relative purity of more than 99 wt% are mixed according to an atomic ratio of 0.735:0.315:11.5:1.5, and lanthanum-cerium-iron-silicon alloy ingots are prepared by vacuum induction melting. A cast iron mold is selected as the casting mold, and the mold shape can be cylindrical according to actual size requirements;

[0103] (2) machining the ingot into a lanthanum-cerium-iron-silicon alloy rod with a diameter of 50 mm and a surface roughness Ra of no more than 1.6 μm;

[0104] (3) Fix the lanthanum-cerium-iron-silicon alloy rod to the rotating device of the plasma rotating electrode equipment as an electrode, so that the center position of the cross section of one end of the alloy rod is aligned with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also makes the feeding smooth and ensures a good sealing effect;

[0105] (4) Evacuate the chamber of the plasma rotating electrode equipment to a vacuum degree of 1*10 -2 Pa, monitor the oxygen content in the chamber to ensure that the oxygen content in the chamber is less than or equal to 5ppm;

[0106] (5) Close the valve between the vacuum pump and the chamber, open the inert gas valve, and fill the vacuum chamber of the plasma rotating electrode equipment with high-purity argon gas to keep the gas pressure in the chamber at 0.12 MPa;

[0107] (6) Turn on the power and adjust the parameters of the plasma rotating electrode equipment. The feed speed of the rod is 1.5 mm / s, the speed of the rotating device is 12000 rpm; the working current of the equipment is 2100 A;

[0108] (7) After the plasma gun head and the electrode are arced, a plasma gas flow is sprayed toward the lanthanum-cerium-iron-silicon alloy rod electrode through the plasma gun, so that the end surface of the alloy rod is partially melted and splashed out with the rotation of the electrode to form droplets of lanthanum-cerium-iron-silicon alloy;

[0109] (8) The centrifugal force of the rotating device and the surface tension of the droplets make the droplets naturally form a spherical shape during flight; the electrode rotates, the end surface melts, the droplets splash, and the pushing device continuously feeds, so that the atomization process continues;

[0110] (9) The inert gas cools the droplets rapidly during flight to form lanthanum-cerium-iron-silicon alloy particles. The inert gas also helps in starting the arc.

[0111] (10) The lanthanum-cerium-iron-silicon alloy particles are collected by a collector.

[0112] The lanthanum-cerium-iron-silicon alloy particles prepared in this example have high sphericity, a smooth surface, no obvious defects, controllable particle size and uniform distribution, D50 is 132 μm, and the yield of lanthanum-cerium-iron-silicon alloy particles is 79 wt %.

[0113] Example 3

[0114] Metal Alloy La 0.84 Pr 0.21 Fe 11.5 Si 1.5 The preparation of spherical particles comprises the following steps:

[0115] (1) Raw materials of lanthanum, praseodymium, iron and silicon with a relative purity of more than 99 wt% are mixed according to an atomic ratio of 0.84:0.21:11.5:1.5, and lanthanum-praseodymium-iron-silicon alloy ingots are prepared by vacuum induction melting and casting. A cast iron mold is selected as the casting mold, and the mold shape can be cylindrical according to actual size requirements;

[0116] (2) machining the ingot into a lanthanum-praseodymium-iron-silicon alloy rod with a diameter of 75 mm and a surface roughness Ra of no more than 1.6 μm;

[0117] (3) Fix the lanthanum-praseodymium-iron-silicon alloy rod to the rotating device of the plasma rotating electrode equipment as an electrode, so that the center position of the cross section of one end of the alloy rod is aligned with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also makes the feeding smooth and ensures a good sealing effect;

[0118] (4) Evacuate the chamber of the plasma rotating electrode equipment to a vacuum degree of 1*10 -2 Pa, monitor the oxygen content in the chamber to ensure that the oxygen content in the chamber is less than or equal to 5ppm;

[0119] (5) Close the valve between the vacuum pump and the chamber, open the inert gas valve, and fill the vacuum chamber of the plasma rotating electrode equipment with high-purity argon gas to keep the gas pressure in the chamber at 0.12 MPa;

[0120] (6) Turn on the power and adjust the parameters of the plasma rotating electrode equipment. The feed speed of the rod is 1.5 mm / s, the speed of the rotating device is 4000 rpm; the working current of the equipment is 2600 A;

[0121] (7) After the plasma gun head and the electrode strike an arc, a plasma gas flow is sprayed toward the lanthanum-praseodymium-iron-silicon alloy rod electrode through the plasma gun, so that the end surface of the alloy rod partially melts and splashes out with the rotation of the electrode, forming droplets of lanthanum-praseodymium-iron-silicon alloy;

[0122] (8) The centrifugal force of the rotating device and the surface tension of the droplets make the droplets naturally form a spherical shape during flight; the electrode rotates, the end surface melts, the droplets splash, and the pushing device continuously feeds, so that the atomization process continues;

[0123] (9) The inert gas cools the droplets in flight to form lanthanum-praseodymium-iron-silicon alloy particles. The inert gas also helps in starting the arc.

[0124] (10) The lanthanum-praseodymium-iron-silicon alloy particles are collected by a collector.

[0125] The lanthanum-praseodymium-iron-silicon alloy particles prepared in this example have high sphericity, a smooth surface, no obvious defects, controllable particle size and uniform distribution, D50 is 324 μm, and the yield of the lanthanum-praseodymium-iron-silicon alloy particles is 78 wt %.

[0126] Example 4

[0127] Metal Alloy La 1.05 Fe 11 Co 0.8 Si 1.2 The preparation of spherical particles comprises the following steps:

[0128] (1) Raw materials of lanthanum, iron, cobalt and silicon with a relative purity of more than 99 wt% are mixed according to an atomic ratio of 1.05:11:0.8:1.2, and lanthanum iron cobalt silicon alloy ingots are prepared by vacuum induction melting and casting. A cast iron mold is selected as the casting mold, and the mold shape can be cylindrical according to actual size requirements;

[0129] (2) machining the ingot into a lanthanum iron cobalt silicon alloy rod with a diameter of 50 mm and a surface roughness Ra of no more than 1.6 μm;

[0130] (3) Fix the lanthanum iron cobalt silicon alloy rod to the rotating device of the plasma rotating electrode equipment as an electrode, so that the center position of the cross section of one end of the alloy rod is aligned with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also makes the feeding smooth and ensures a good sealing effect;

[0131] (4) Evacuate the chamber of the plasma rotating electrode equipment to a vacuum degree of 1*10 -2 Pa, monitor the oxygen content in the chamber to ensure that the oxygen content in the chamber is less than or equal to 5ppm;

[0132] (5) Close the valve between the vacuum pump and the chamber, open the inert gas valve, and fill the vacuum chamber of the plasma rotating electrode equipment with high-purity argon gas to keep the gas pressure in the chamber at 0.12 MPa;

[0133] (6) Turn on the power and adjust the parameters of the plasma rotating electrode equipment. The feed speed of the rod is 1.5 mm / s, the speed of the rotating device is 2500 rpm; the working current of the equipment is 1600 A;

[0134] (7) After the plasma gun head and the electrode are arced, a plasma gas flow is sprayed toward the lanthanum iron cobalt silicon alloy rod electrode through the plasma gun, so that the end surface of the alloy rod is partially melted and splashed out with the rotation of the electrode to form droplets of lanthanum iron cobalt silicon alloy;

[0135] (8) The centrifugal force of the rotating device and the surface tension of the droplets make the droplets naturally form a spherical shape during flight; the electrode rotates, the end surface melts, the droplets splash, and the pushing device continuously feeds, so that the atomization process continues;

[0136] (9) The inert gas cools the droplets rapidly during flight to form lanthanum iron cobalt silicon alloy particles. The inert gas also helps in starting the arc.

[0137] (10) The lanthanum iron cobalt silicon alloy particles are collected by a collector.

[0138] The lanthanum iron cobalt silicon alloy particles prepared in this example have high sphericity, a smooth surface, no obvious defects, controllable particle size and uniform distribution, D50 is 564 μm, and the yield of lanthanum iron cobalt silicon alloy particles is 79 wt %.

[0139] Example 5

[0140] Metal Alloy La 1.05 Fe 11.2 Mn 0.3 Si 1.5 The preparation of spherical particles comprises the following steps:

[0141] (1) Raw materials of lanthanum, iron, manganese and silicon with a relative purity of more than 99 wt% are mixed according to an atomic ratio of 1.05:11.2:0.3:1.5, and lanthanum iron manganese silicon alloy ingots are prepared by vacuum induction melting and casting. A cast iron mold is selected as the casting mold, and the mold shape can be cylindrical according to actual size requirements;

[0142] (2) machining the ingot into a lanthanum iron manganese silicon alloy rod with a diameter of 50 mm and a surface roughness Ra of not more than 1.6 μm;

[0143] (3) Fix the lanthanum iron manganese silicon alloy rod to the rotating device of the plasma rotating electrode equipment as an electrode, so that the center position of the cross section of one end of the alloy rod is aligned with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also makes the feeding smooth and ensures a good sealing effect;

[0144] (4) Evacuate the chamber of the plasma rotating electrode equipment to a vacuum degree of 1*10 -2 Pa, monitor the oxygen content in the chamber to ensure that the oxygen content in the chamber is less than or equal to 5ppm;

[0145] (5) Close the valve between the vacuum pump and the chamber, open the inert gas valve, and fill the vacuum chamber of the plasma rotating electrode equipment with high-purity argon gas to keep the gas pressure in the chamber at 0.12 MPa;

[0146] (6) Turn on the power and adjust the parameters of the plasma rotating electrode equipment. The feed speed of the rod is 1.5 mm / s, the speed of the rotating device is 1500 rpm; the working current of the equipment is 1400 A;

[0147] (7) After the plasma gun head and the electrode are arced, a plasma gas flow is sprayed toward the lanthanum iron manganese silicon alloy rod electrode through the plasma gun, so that the end surface of the alloy rod is partially melted and splashed out with the rotation of the electrode to form lanthanum iron manganese silicon alloy droplets;

[0148] (8) The centrifugal force of the rotating device and the surface tension of the droplets make the droplets naturally form a spherical shape during flight; the electrode rotates, the end surface melts, the droplets splash, and the pushing device continuously feeds, so that the atomization process continues;

[0149] (9) The cooling effect of the inert gas causes the droplets to solidify rapidly during flight to form lanthanum-iron-manganese-silicon alloy particles. The inert gas also helps to start the arc.

[0150] (10) The lanthanum-iron-manganese-silicon alloy particles are collected by a collector.

[0151] The lanthanum iron manganese silicon alloy particles prepared in this example have high sphericity, a smooth surface, no obvious defects, controllable particle size and uniform distribution, D50 is 973 μm, and the yield of lanthanum iron manganese silicon alloy particles is 77 wt %.

[0152] The raw material ratios and process parameters of Examples 6-16 are shown in Table 1.

[0153] Examples 17-21

[0154] Examples 17-21 are RT-Si secondary alloy particles obtained by heat treating the RT-Si alloy particles obtained in Examples 1-5, wherein the heat treatment temperature of the RT-Si alloy particles is 1050-1150°C and the insulation time is 12-48h.

[0155] The obtained RT-Si secondary alloy particles formed a 1:13 phase and a mixed phase; taking the RT-Si secondary alloy particles obtained by heat treatment of the RT-Si alloy particles in Example 12 as an example, an XRD test was performed on them. The XRD spectra before and after the heat treatment are as follows: Figure 4 and Figure 5 As shown, it can be seen that there is only an impurity phase before heat treatment, and after heat treatment, a 1:13 main phase is generated, and some impurity phases also exist.

[0156] Table 1

[0157]

[0158] The RT-Si alloy particles of the present invention have the advantages of good sphericity, smooth surface and no obvious defects. When applied to the field of magnetic refrigeration, they also have good magnetocaloric properties. The preparation method of the present invention can adjust the particle size distribution by adjusting parameters such as the rotation speed and working current of the equipment to meet different application requirements and the yield is high, all of which are 75% and above.

[0159] Taking Example 12 as an example, the physical picture of the prepared lanthanum iron silicon alloy particles is as follows: Figure 1 As shown, the metallographic diagram is as follows Figure 2 As shown, combined Figure 6 , it can be seen that the prepared alloy particles have high sphericity, smooth surface and no obvious defects; Figure 3 This is a particle size distribution diagram of the lanthanum iron silicon alloy particles obtained in Example 12. It can be seen that the diagram presents a normal distribution in a relatively narrow range, indicating that the particle size of the lanthanum iron silicon alloy particles obtained in the present invention is controllable and uniformly distributed. The measured D50 is 556 μm, and the yield of the lanthanum iron silicon alloy particles is ≥75%. Figure 4 is the XRD pattern of the lanthanum-iron-silicon alloy particles obtained in Example 12, Figure 5 This is the XRD diagram of the lanthanum iron silicon secondary alloy particles prepared in Example 12. It can be seen that there is only an impurity phase before heat treatment, and a large amount of 1:13 main phase is generated after heat treatment, with only a small amount of partial impurity phase. Figure 7 and Figure 8 The MT curve of the lanthanum-iron-silicon alloy particles obtained in Example 12 measured under a magnetic field of 0.02-3 T is shown in FIG. Fig. 9 It can be seen that the Curie temperature (Tc) of the alloy particles under different magnetic fields, the alloy particle curve conforms to the characteristics of the first-order phase change material, and the curve transitions smoothly near the Curie temperature, indicating that the phase composition of the material is uniform; Fig.10 This is a graph showing the magnetic entropy change data of the lanthanum-iron-silicon alloy particles prepared in Example 12 under different magnetic fields. It can be seen that the alloy particles have good magnetocaloric properties under different magnetic fields.

[0160] The above descriptions are only a few embodiments of the present invention and do not limit the present invention in any form. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A RT-Si alloy particle, characterized in that: It includes R, T and Si, wherein the atomic ratio of R to "the T and the Si" is (1-1.1): (13-15.5); the atomic ratio of T to the Si is (4.4-30): 1; Wherein, R is one or more rare earth metal elements; T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium; The average particle size of the RT-Si alloy particles is 10 μm-1000 μm.

2. The RT-Si alloy particles according to claim 1, characterized in that The atomic ratio of R to "the T and the Si" is (1.03-1.05):(13-14), for example, 1.03:13, 1.05:13 or 1.05:13.2; and / or, the atomic ratio of the R, the T and the Si is (1.03-1.05):(11-12):(1-2), for example, 1.03:11.5:1.5, 1.03:11.6:1.4, 1.05:11.5:1.5, 1.05:11.8:1.2, 1.05:11.6:1.6, 1.05:11.7:1.5 or 1.05:12:1.2; And / or, the RT-Si alloy particles satisfy one or more of the following conditions ac: a. R is one or more of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium; preferably, R includes lanthanum; for example, R is lanthanum, "lanthanum and cerium", "lanthanum and praseodymium", "lanthanum, cerium and praseodymium" or "lanthanum, cerium, praseodymium and neodymium"; Wherein, when the R is lanthanum and cerium, the atomic ratio of lanthanum and cerium is preferably (2-6):1, for example, 0.735:0.315; Wherein, when the R is lanthanum and praseodymium, the atomic ratio of lanthanum and praseodymium is preferably (2-6):1, for example, 0.84:0.21; Wherein, when the R is lanthanum, cerium and praseodymium, the atomic ratio of lanthanum, cerium and praseodymium is preferably (2-6):1:1, for example, 0.63:0.21:0.21 Wherein, when the R is lanthanum, cerium, praseodymium and neodymium, the atomic ratio of lanthanum, cerium, praseodymium and neodymium is preferably (2-6):2:1:1, for example, 0.63:0.21:0.105:0.105; b. The T comprises one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium; preferably, the T comprises iron, for example, the T is iron, "iron and manganese", "iron and cobalt" or "iron, manganese and cobalt"; When T is iron and manganese, the atomic ratio of iron to manganese is preferably (30-40):1, such as 11.2:0.3; When T is iron and cobalt, the atomic ratio of iron and cobalt is preferably (10-15):1, such as 11:0.8; c. The relative purity of R is ≥99wt%, preferably ≥99.5wt%.

3. The RT-Si alloy particles according to claim 1, characterized in that R is lanthanum, T is iron, and the atomic ratio of lanthanum, iron and silicon is (1.03-1.05):11.5:1.5, for example, 1.05:11.5:1.5, 1.03:11.6:1.4 or 1.03:11.5:1.5; Or, R is lanthanum and cerium, T is iron, and the atomic ratio of lanthanum, cerium, iron and silicon is (0.6-0.8): (0.2-0.4): (11.5-12): 1.5, for example 0.735: 0.315: 11.5: 1.5 or 0.735: 0.315: 11.7: 1.5; Or, R is lanthanum and praseodymium, T is iron, and the atomic ratio of lanthanum, praseodymium, iron and silicon is (0.7-0.9): (0.1-0.3): (11.5-12): (1-1.5), for example 0.84: 0.21: 11.5: 1.5 or 0.84: 0.21: 11.7: 1.5; Or, R is lanthanum, T is iron and cobalt, and the atomic ratio of lanthanum, iron, cobalt and silicon is 1.05: (10.9-11.1): (0.7-0.9): 1.2, for example, 1.05: 11: 0.8: 1.2 or 1.05: 11.1: 0.9: 1.2; Or, R is lanthanum, T is iron and manganese, and the atomic ratio of lanthanum, iron, manganese and silicon is 1.05: (11.1-11.3): (0.2-0.4): 1.5, for example, 1.05: 11.2: 0.3: 1.5 or 1.05: 11.3: 0.2: 1.5; Or, R is lanthanum, cerium and praseodymium, T is iron, and the atomic ratio of lanthanum, cerium, praseodymium, iron and silicon is 0.63:0.21:0.21:11.5:1.5; Or, R is lanthanum, cerium, praseodymium and neodymium, T is iron, and the atomic ratio of lanthanum, cerium, praseodymium, neodymium, iron and silicon is 0.63:0.21:0.105:0.105:11.5:1.5; Or, R is lanthanum and cerium, T is iron and cobalt, and the atomic ratio of lanthanum, cerium, iron, cobalt and silicon is 0.84:0.21:11:0.8:1.2; Or, R is lanthanum and cerium, T is iron and manganese, and the atomic ratio of lanthanum, cerium, iron, manganese and silicon is 0.735:0.315:11.2:0.3:1.

5.

4. A method for preparing RT-Si alloy particles, characterized in that: It includes the following steps: The substrate is subjected to a plasma rotating electrode atomization method to obtain the RT-Si alloy particles; Wherein, the substrate includes R, T and Si, the atomic ratio of R to "the T and the Si" is 1:(11.8-15.5); the atomic ratio of T to the Si is (4.4-30):1; wherein, R is one or more rare earth metal elements; and T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium.

5. The method for preparing RT-Si alloy particles according to claim 4, characterized in that: The plasma rotating electrode atomization method is performed in a plasma rotating electrode atomization device, and the parameter setting of the plasma rotating electrode atomization device satisfies one or more of the following conditions ag: a. The rotation speed of the substrate is 500rpm-30000rpm, preferably 1500rpm-26000rpm, for example 1500rpm, 2500 rpm, 4000 rpm, 12000 rpm or 26000 rpm; b. The operating current varies along the radial direction of the cross section of the substrate. Preferably, at the center of the cross section of the substrate, the operating current is 800-3000A, such as 800A, 1400A, 1600A, 2100A or 2600A; at a quarter of the diameter of the cross section of the substrate, the operating current is 600-3000A, such as 600A, 800A, 900A, 1100A or 1400A; c. The feed speed of the substrate is 1-10 mm / s, preferably 1-5 mm / s, for example 1.5 mm / s; d. The plasma rotating electrode atomization device used in the plasma rotating electrode atomization method includes an electrode rotating and sealing device, a pushing device, a plasma gun head, an atomization chamber, an inert gas environment and a collector; wherein the chamber of the collector is preferably circular or conical; the width of the chamber of the collector is preferably 100-2000mm; the diameter of the chamber is preferably 1000-4000mm; e. The vacuum degree in the atomization chamber is ≤1×10 -2 Pa; the oxygen content in the atomization chamber is ≤50ppm, preferably ≤5ppm; f. The preparation is carried out in an inert gas environment, wherein the oxygen content in the inert gas is preferably ≤50ppm, more preferably ≤5ppm, and the pressure of the inert gas environment is preferably maintained at 0.05MPa-0.3MPa; more preferably 0.1MPa-0.2MPa, for example 0.12MPa; the inert gas is preferably argon and / or helium; g. The center of the plasma gun head corresponds to any position of the cross section of the substrate, such as the center position of the cross section of the substrate or one quarter of the diameter of the cross section of the substrate; And / or, the substrate is in the shape of a rod; the diameter of the rod is preferably 5 mm-150 mm; the rod is preferably threaded; And / or, the surface roughness of the substrate is Ra≤1.6 μm; And / or, the preparation method of the substrate comprises the following steps: melting and casting the raw materials to obtain an ingot, and then machining the ingot; the melting method is preferably a vacuum medium frequency induction melting preparation process.

6. RT-Si alloy particles obtained by the preparation method according to claim 4 or 5.

7. A RT-Si secondary alloy particle, characterized in that: The atomic ratio of R to "the T and the Si" is (1-1.1): (13-15.5); the atomic ratio of T to the Si is (4.4-30): 1; Wherein, R is one or more rare earth metal elements; T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium; The RT-Si secondary alloy particles contain a main phase, and the main phase is R(TSi) 13 type compound; the RT-Si secondary alloy particles may also contain a heterogeneous phase, the heterogeneous phase is at least one of a T element, an R element, an RT compound and a R1T1Si1 type compound, and the average particle size of the RT-Si secondary alloy particles is 10μm-1000μm.

8. A method for preparing RT-Si secondary alloy particles, characterized in that: It is prepared by heat treating the RT-Si alloy particles according to any one of claims 1 to 3 and claim 6; Wherein, the temperature of the heat treatment is preferably 1050-1150°C, for example 1050°C or 1120°C; The heat treatment holding time is preferably 12-48 hours, such as 12 hours or 24 hours.

9. A RT-Si secondary alloy particle, characterized in that: It is prepared by the preparation method described in claim 8.

10. Use of the RT-Si alloy particles according to any one of claims 1 to 3 and 6, or the RT-Si secondary alloy particles according to claim 7 or 9 as magnetic refrigeration materials in the field of solid-state refrigeration.

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