CN114005633A - Rare earth soft magnetic material with multi-shell structure and preparation method thereof - Google Patents
Rare earth soft magnetic material with multi-shell structure and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a rare earth soft magnetic material with a multi-shell structure and a preparation method thereof, belongs to the technical field of magnetic materials, and solves the problem that the frequency bandwidth of the existing soft magnetic material is small. The rare earth soft magnetic material with the multi-shell structure is a core-shell structure consisting of a main phase core and two shells, and the two shells are a first shell and a second shell in sequence along the direction from the main phase core to the shells; the main phase inner core has easy plane shape anisotropy and easy plane magnetocrystalline anisotropy, and the directions of the two anisotropy fields are consistent; the first shell layer is a phase with easy plane shape anisotropy and easy conical surface magnetocrystalline anisotropy simultaneously; the second shell layer is a rare earth-rich phase oxide layer and has high resistivity. The rare earth soft magnetic material with the multi-shell structure has wider frequency bandwidth and lower complex dielectric constant, and can effectively improve the impedance matching and microwave absorption performance of the material.
Description
Technical Field
The invention belongs to the technical field of magnetic materials, and particularly relates to a rare earth soft magnetic material with a multi-shell structure and a preparation method thereof.
Background
The transmission rate of energy and information and the data arithmetic capability are continuously improved, and a high-frequency device with higher working frequency is required. Soft magnetic materials are the key to the efficient operation of new generation high frequency devices. Soft magnetic materials that can currently operate at high frequencies mainly include planar hexaferrite, 3d metal alloys, amorphous nanocrystalline alloys, and the like.
The planar hexagonal ferrite has low anisotropy field and low saturation magnetization, so that the resonant frequency and the high-frequency magnetic permeability are low, and the requirements of high-frequency devices cannot be met. Although the saturation magnetization intensity of the material is high, the resonant frequency of the material still cannot meet the requirements of high-frequency electronic devices due to the fact that the magnetocrystalline anisotropy field of the material is low. The rare earth intermetallic compound and the biphase nanocrystalline high-frequency soft magnetic material have high magnetocrystalline anisotropy fields, can greatly improve the resonance frequency of the material, but cannot prepare anisotropic particles by the traditional method. At present, the magnetic powder with the shape anisotropy and the magnetocrystalline anisotropy of the easy surface has improved resonance frequency and high-frequency intrinsic magnetism, but has smaller bandwidth.
The device works in a high frequency range, and not only a high resonance frequency but also a wider frequency bandwidth are required, but related researches are not reported.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a rare earth soft magnetic material with a multi-shell structure and a preparation method thereof, which solves the problem of small frequency bandwidth of the soft magnetic material in the prior art. The soft magnetic material provided by the invention has wider frequency bandwidth, has lower complex dielectric constant, and can effectively improve the impedance matching and microwave absorption performance of the material.
The purpose of the invention is mainly realized by the following technical scheme:
on one hand, the invention provides a multi-shell structure rare earth soft magnetic material which is a core-shell structure consisting of a main phase core and two shells, wherein the two shells are a first shell and a second shell in sequence along the direction from the main phase core to the shells;
the main phase inner core has easy plane shape anisotropy and easy plane magnetocrystalline anisotropy, and the directions of the two anisotropy fields are consistent;
the first shell layer is a phase with easy plane shape anisotropy and easy conical surface magnetocrystalline anisotropy simultaneously;
the second shell layer is a rare earth-rich phase oxide layer and has high resistivity.
Furthermore, the multi-shell structure rare earth soft magnetic material is integrally flaky, and comprises a main phase core, a first shell wrapping the main phase core and a second shell wrapping the first shell; the thickness direction section of the flaky multi-shell structure rare earth soft magnetic material is of a 5-layer structure and sequentially comprises a second shell, a first shell, a main phase core, a first shell and a second shell.
Further, the composition of the main phase core mainly comprises R, Fe and B; the composition of the first shell layer mainly comprises R, R', Fe and B; the components of the second shell mainly comprise R, R', M, O and Fe; r is one or more of Sm (samarium), Er (erbium) and Tm (thulium), R' is one or more of praseodymium (Pr), neodymium (Nd), cerium (Ce), lanthanum (La) and yttrium (Y), and M is one or more of copper, aluminum, gallium, niobium, zirconium and iron.
Further, the chemical formula of the main phase core is represented as R according to the atomic ratio2Fe14B; the chemical formula of the first shell layer is expressed as (RR')2Fe14B。
Furthermore, the raw materials for preparing the rare earth soft magnetic material with the multi-shell structure comprise a main phase alloy and an auxiliary alloy; the chemical formula of the main phase alloy is represented as R according to the atomic ratio2+xFe14B; the chemical formula of the secondary alloy is R 'in terms of atomic ratio'yM1-y。
Furthermore, x is more than or equal to 0.01 and less than or equal to 0.4, and y is more than or equal to 0.3 and less than 1.
On the other hand, the invention also provides a preparation method of the rare earth soft magnetic material with the multi-shell structure, which is used for preparing the rare earth soft magnetic material with the multi-shell structure.
Further, the preparation method comprises the following steps:
step 4, heat treatment: performing heat treatment on the thermally deformed magnetic block within the temperature range of 400-900 ℃ to enable the auxiliary alloy to be fully diffused into the main phase alloy to form a main phase kernel and a first shell;
step 5, crushing: and (4) crushing the magnetic blocks obtained in the step (4) into magnetic powder particles, and oxidizing the surfaces of the magnetic powder particles into rare earth-rich phase oxide layers to obtain the rare earth soft magnetic material with the multi-shell structure.
Further, in the step 1, the weight ratio of the auxiliary alloy powder in the mixed powder is more than 0 and less than or equal to 10%.
Further, in the step 3, the thermal deformation temperature is 780-850 ℃.
Compared with the prior art, the invention has at least one of the following beneficial effects:
1) the rare earth soft magnetic material with the multi-shell structure comprises a main phase core, a first shell wrapping the main phase core and a rare earth-rich phase oxide layer (namely a second shell) wrapping the first shell, wherein the main phase core has easy plane shape anisotropy and easy plane magnetocrystalline anisotropy simultaneously through selection of rare earth elements Sm, Er and Tm, and the two anisotropy fields have a superposition effect in the same direction; the first shell layer is a phase which has easy plane shape anisotropy and easy conical surface magnetocrystalline anisotropy simultaneously through selection of rare earth elements Pr, Nd, Ce, La and Y; the main phase core and the first shell have different magnetocrystalline anisotropy fields. The two types of materials with different anisotropic fields are coupled on the nanometer scale, so that the resonance frequency bandwidth of the materials is effectively improved, for example, the resonance frequency bandwidth reaches more than 4.2 GHz.
2) According to the multi-shell structure rare earth soft magnetic material provided by the invention, the addition of the auxiliary alloy can form a high-resistivity rare earth-rich oxide layer with a certain thickness on the surface of the material, so that the complex dielectric constant of the soft magnetic material can be effectively reduced, and the impedance matching and microwave absorption performance of the material are further improved.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the instrumentalities and combinations particularly pointed out in the written description.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a schematic structural diagram of a multi-shell structure rare earth soft magnetic material of the present invention;
FIG. 2 is a cross-sectional view of a thermally deformed magnetic block of example 1;
FIG. 3 is an SEM photograph of the magnetic powder after crushing of example 1.
Reference numerals:
1-main phase kernel, 2-first shell, 3-second shell, A-main phase kernel easy plane magnetic moment distribution, B-first shell easy cone magnetic moment distribution.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention.
On one hand, the invention provides a multi-shell structure rare earth soft magnetic material which is a core-shell structure consisting of a main phase core and two shells, wherein the two shells are a first shell and a second shell in sequence along the direction from the main phase core to the shells;
the main phase inner core has easy plane shape anisotropy and easy plane magnetocrystalline anisotropy, and the directions of the two anisotropy fields are consistent;
the first shell layer is a phase with easy plane shape anisotropy and easy conical surface magnetocrystalline anisotropy simultaneously;
the second shell layer is a rare earth-rich phase oxide layer, and has a metal oxide phase compared with the metal compound composition of the main phase core and the first shell layer, so that the second shell layer has high resistivity. That is, the high resistivity claimed by the present invention is a relative concept, and the metal oxide phase of the second shell layer has a higher resistivity than the metal compound composition of the main phase core and the first shell layer, that is, the resistivity of the main phase core and the first shell layer is lower than that of the second shell layer.
The rare earth soft magnetic material is rare earth magnetic particles with a multi-shell structure, a main phase is used as an inner core, the rare earth soft magnetic material comprises a core-shell structure with two shell layers, the inner core is a main phase inner core with easy plane shape anisotropy and easy plane magnetocrystalline anisotropy, a first shell layer with easy plane shape anisotropy and easy plane magnetocrystalline anisotropy and a second shell layer with high resistivity, namely a rare earth-rich phase oxide layer shell layer, are sequentially wrapped outside, namely the first shell layer is wrapped on the surface of the main phase inner core, and the second shell layer is wrapped on the surface of the first shell layer and is positioned on the outermost layer of the magnetic particles.
The rare earth soft magnetic material provided by the invention is completely not used for soft magnetic materials such as plane hexagonal ferrite, 3d metal alloy, amorphous nanocrystalline alloy and the like in the prior art, and the high-frequency intrinsic magnetism of the rare earth soft magnetic material is improved by the consistent directions and mutual superposition of two anisotropic fields of a main phase core and a main phase core, and the rare earth soft magnetic material is cooperated with a first shell layer with an easy conical surface shape, so that the rare earth soft magnetic material has wider natural resonance frequency; meanwhile, the second shell layer with high resistivity is covered, so that the complex dielectric constant of the material is greatly reduced, and better impedance matching and microwave absorption performance can be obtained.
Fig. 1 is a schematic structural diagram of the rare earth soft magnetic material with a multi-shell structure provided by the present invention, as shown in fig. 1, the whole rare earth soft magnetic material with a multi-shell structure is in a sheet shape, the rare earth soft magnetic material with a multi-shell structure includes a main phase core 1, a first shell 2 wrapping the main phase core 1, and a second shell 3 wrapping the first shell 2, and the second shell 3 is a rare earth-rich phase oxide layer. That is to say, the thickness direction section of the rare earth soft magnetic material with the flaky multi-shell structure is a 5-layer structure, and the rare earth soft magnetic material sequentially comprises a second shell layer 3 (namely a rare earth-rich phase oxide layer), a first shell layer 2, a main phase core 1, a first shell layer 2 and a second shell layer 3 (namely a rare earth-rich phase oxide layer); the main phase kernel 1 has both easy plane shape anisotropy and easy plane magnetocrystalline anisotropy, and the two anisotropy fields have the same direction and have the superposition effect.
Specifically, the main phase core 1 mainly comprises R, Fe and B. Wherein R is one or more of Sm (samarium), Er (erbium) and Tm (thulium).
Specifically, the chemical formula of the main phase core 1 may be represented by R in terms of atomic ratio2Fe14B。
Specifically, the composition of the first shell 2 mainly includes R, R', Fe and B. Wherein, R' is one or more of praseodymium (Pr), neodymium (Nd), cerium (Ce), lanthanum (La) and yttrium (Y).
Specifically, the chemical formula of the first shell layer 2 can be represented by (RR')2Fe14B。
Specifically, the composition of the second shell 3 mainly includes R, R', M, O and Fe.
Specifically, the thickness of the second shell 3 may be 3 to 90 nm.
Specifically, the main phase core 1 has both easy planar anisotropy and easy planar magnetocrystalline anisotropy, and the two anisotropy fields have the same direction and have the superposition effect; the first shell layer 2 is a phase having both easy planar anisotropy and easy conical magnetocrystalline anisotropy; the second shell 3 is a rare earth-rich phase oxide layer having a high resistivity.
Specifically, the raw materials for preparing the rare earth soft magnetic material with the multi-shell structure comprise a main phase alloy and an auxiliary alloy; wherein the chemical formula of the main phase alloy can be represented as R according to the atomic ratio2+xFe14B. Wherein the composition of the main phase alloy comprises a main phase and a rare earth-rich phase, wherein the chemical formula of the main phase can be expressed as R according to the atomic ratio2Fe14B, the chemical formula of the rare earth-rich phase can be expressed as R according to the atomic ratiox. Wherein R is one or more of Sm (samarium), Er (erbium) and Tm (thulium) to ensure R2Fe14The B phase has easy-to-plane magnetocrystalline anisotropy.
Specifically, x is controlled to be more than or equal to 0.01 and less than or equal to 0.4 in order to ensure that enough rare earth-rich phase is subjected to thermal deformation in the preparation process.
Specifically, the chemical formula of the secondary alloy may be represented by R 'in terms of atomic ratio'yM1-yR 'is one or more of praseodymium (Pr), neodymium (Nd), cerium (Ce), lanthanum (La) and yttrium (Y) so as to ensure R'2Fe14The B phase has C-axis magnetocrystalline anisotropy.
Specifically, M is one or more of copper, aluminum, gallium, niobium, zirconium, and iron, so as to ensure that M element is only distributed in the second shell 3 and does not enter the main phase core 1 during the preparation process.
Specifically, in the above-mentioned secondary alloy, too small an amount of R 'inhibits the permeation diffusion of R' into the main phase.
Therefore, y is controlled to be more than or equal to 0.3 and less than 1;
on the other hand, the invention provides a preparation method of the rare earth soft magnetic material with the multi-shell structure, which takes a main phase alloy comprising a main phase and a rare earth-rich phase and an auxiliary alloy containing rare earth elements as raw materials, realizes the modification of the main phase alloy part by the auxiliary alloy through hot pressing, thermal deformation and heat treatment processes, forms a core-shell structure of a main phase core, a first shell and a rare earth-rich phase layer, and obtains the rare earth soft magnetic material with the multi-shell structure, which is composed of the main phase core, the first shell and a rare earth-rich phase oxide layer (namely a second shell) after the rare earth-rich phase layer is oxidized.
The main phase alloy and the auxiliary alloy are both powder, the mixed powder is pressed into a full-density isotropic block body in the hot pressing process, and the full-density isotropic block body formed by hot pressing is subjected to thermal deformation treatment to obtain the thermal deformation magnetic block with the inner particles in a sheet structure.
The main phase alloy comprises a main phase and a rare earth-rich phase, and the chemical formula of the main phase alloy can be expressed as R according to the atomic ratio2+ xFe14B. Wherein the chemical formula of the main phase can be represented as R in terms of atomic ratio2Fe14B, the chemical formula of the rare earth-rich phase can be expressed as R according to the atomic ratiox. The chemical formula of the secondary alloy can be represented as R 'according to the atomic ratio'yM1-yAnd R' is one or more of praseodymium (Pr), neodymium (Nd), cerium (Ce), lanthanum (La) and yttrium (Y). In the process of carrying out heat treatment on the thermal deformation magnetic block, the rare earth element of the auxiliary alloy is partially diffused into part of the main phase, the main phase part without the diffusion of the rare earth element of the auxiliary alloy forms a main phase inner core, and the main phase part with the diffusion of the rare earth element of the auxiliary alloy forms a first shell layer 2. Accordingly, the chemical formula of the first shell layer 2 can be represented by (RR')2Fe14B。
As the rare earth element of the auxiliary alloy is diffused into part of the main phase to form the first shell layer 2, the rare earth-rich phase of the main phase alloy is oxidized in the crushing treatment process of the thermal deformation magnetic block to form the second shell layer 3 comprising the first shell layer 2. Accordingly, the composition of the second shell 2 mainly includes R, R', M, O and Fe.
Specifically, the preparation method of the rare earth soft magnetic material with the multi-shell structure comprises the following steps:
step 4, heat treatment: performing heat treatment on the thermally deformed magnetic block within the temperature range of 400-900 ℃, wherein the heat treatment time is 10-120 min, so that the rare earth elements (the rare earth elements are diffused into part of the main phase) of the auxiliary alloy are fully diffused into the main phase alloy to form a main phase kernel 1 and a first shell layer 2;
step 5, crushing: and (4) crushing the magnetic block obtained in the step (4) by using a coarse crusher or hydrogen, then crushing the magnetic block into magnetic powder particles by using a ball mill or an air flow mill, and fully oxidizing the surfaces of the magnetic powder particles into a rare earth-rich phase oxide layer to obtain the rare earth soft magnetic material with a multi-shell structure.
Specifically, in the step 1, the powder mixing time is too short, so that the mixing is insufficient and uneven; therefore, the powder mixing time is controlled to be more than 1 h.
Specifically, in the step 2, the hot pressing has the effect of densifying the powder, and the excessive temperature can rapidly grow the crystal grains of the main phase alloy, so that the thermal deformation effect is influenced; too low may reduce densification. Therefore, the hot pressing temperature is controlled to be higher than the melting point of the secondary alloy, for example, the hot pressing temperature is controlled to be 700-750 ℃ (e.g., 710 ℃, 720 ℃, 730 ℃, 740 ℃).
Specifically, in the step 3, the thermal deformation is used for enabling the main phase alloy to be distributed in a sheet shape after being deformed, the magnetocrystalline anisotropy and the shape anisotropy are kept consistent, the grains of the main phase alloy can grow rapidly when the temperature is too high, and the deformation effect can be reduced when the temperature is too low. Therefore, the thermal deformation temperature is controlled to be 780-850 ℃ (for example, 810 ℃, 820 ℃, 830 ℃, 840 ℃).
Specifically, in the step 4, the heat treatment is performed to fully diffuse the secondary alloy and the main phase alloy, the temperature is related to the components of the secondary alloy, the secondary alloy can diffuse into the whole particles of the main phase alloy after a long time, and the diffusion can be insufficient after a short time. Therefore, the temperature is controlled to be 400-900 ℃ (e.g., 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃) and the time is 10-120 min (e.g., 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110 min).
Specifically, in the step 5, the magnetic powder particles prepared by the crushing process are in a sheet shape, the magnetic powder is crushed to be broken along the rare earth-rich phase, and the surfaces of the crushed magnetic powder particles are fully oxidized into the second shell layer 3.
Specifically, in the step 5, the obtained rare earth soft magnetic material with the multi-shell structure is mostly used under high frequency, and the complex permeability of the magnetic powder is reduced when the length of the magnetic powder particles is too small; therefore, the length of the magnetic powder particles is controlled to be more than or equal to 1 mu m; the particle thickness is too large to suppress the eddy current effect, and thus, the particle thickness is controlled to be <500 nm.
Specifically, in the step 5, the mass percentage of R and R' in the second shell layer 3 in the multi-shell-layer structure rare earth soft magnetic material is not less than 35%.
Specifically, in the step 5, the resonance frequency bandwidth of the obtained rare earth soft magnetic material with the multi-shell structure reaches more than 5GHz, for example, 5 to 6.2 GHz; the complex dielectric constant is less than 34, for example, 27.5 to 34.
In the step 1, the preparation method of the main alloy powder and the auxiliary alloy powder comprises the following steps:
step 11, batching: proportioning rare earth metal R, iron and ferroboron alloy according to the proportion of main phase alloy; proportioning the rare earth metals R' and M according to the auxiliary alloy proportion;
step 12, smelting: under the protection of argon, smelting the raw materials proportioned in the step 11 into an ingot, and cooling; respectively smelting the main phase alloy and the auxiliary alloy;
step 13, rapidly quenching and casting a main-phase alloy ingot: preparing the main phase alloy ingot cast smelted in the step 12 into a main alloy rapid quenching zone by a melt rapid quenching method;
step 14, preparing the auxiliary alloy ingot smelted in the step 12 into an auxiliary alloy rapid quenching belt by a melt rapid quenching method, or carrying out homogenization heat treatment on the auxiliary alloy ingot smelted in the step 12, wherein the heat treatment temperature is 550-1100 ℃, and the heat treatment time is more than or equal to 10 hours;
step 15, coarse crushing: grinding or hydrogen crushing the main alloy rapid quenching belt prepared in the step 13 and the auxiliary alloy rapid quenching belt or the auxiliary alloy ingot subjected to heat treatment in the step 14 until the granularity of alloy powder is less than 150 mu m;
specifically, in step 11, because the oxide scale may form impurities distributed in the sample during the smelting process, in order to ensure the purity of the sample, the oxide scale removal treatment needs to be performed on the surface of the raw material before the batching.
Specifically, in the step 12, the melting process needs to be performed with electromagnetic stirring or repeated melting for more than or equal to 3 times, so as to ensure that the alloy is uniformly melted.
Specifically, in step 13, the grain size of the main phase alloy is required to be in the nanometer level due to the thermal deformation process; therefore, the main alloy rapid quenching zone is controlled to be of a nanocrystalline structure or an amorphous structure or a coexisting amorphous and nanocrystalline structure.
Specifically, in the step 14, the aim of performing the homogenization heat treatment on the secondary alloy ingot melted in the step 12 is to make the secondary alloy components uniform and to prevent the phenomenon of element segregation. The temperature selection is related to the components and melting points of the auxiliary alloy, and the auxiliary alloy can be melted when the temperature is too high; the purpose of fully diffusing elements cannot be achieved when the content is too low; too short a time, insufficient diffusion of elements; therefore, the heat treatment temperature is controlled to be 550-1100 ℃, and the heat treatment time is more than or equal to 10 hours.
Specifically, in the step 15, the grain size of the alloy powder after coarse crushing is too large, which reduces the subsequent crushing efficiency; therefore, the grain size of the alloy powder after coarse crushing is controlled to be less than 150 μm.
Specifically, in the step 1, the amount of the auxiliary alloy powder is too small to permeate around the main phase; the auxiliary alloy is a non-magnetic phase, and the overall magnetism of the magnetic powder is reduced if the auxiliary alloy is excessive; therefore, the weight ratio of the secondary alloy powder in the mixed powder is controlled to be more than 0 and 10% or less, for example, 1% to 10%.
The rare earth soft magnetic material with the multi-shell structure comprises a main phase core, a first shell wrapped outside the main phase core and a rare earth-rich phase oxide layer wrapped outside the first shell, wherein the main phase core simultaneously has easy plane shape anisotropy and easy plane magnetocrystalline anisotropy, and the two anisotropy fields have a superposition effect in the same direction; the first shell layer is a phase with easy plane shape anisotropy and easy conical surface magnetocrystalline anisotropy simultaneously; the main phase kernel and the first shell of the present invention have different anisotropy fields. The two types of materials with different anisotropic fields are coupled on the nanometer scale, so that the resonance frequency bandwidth of the materials is effectively improved, for example, the resonance frequency bandwidth reaches more than 5 GHz.
According to the multi-shell structure rare earth soft magnetic material provided by the invention, the addition of the auxiliary alloy can form a high-resistivity rare earth-rich oxide layer with a certain thickness on the surface of the material, so that the complex dielectric constant of the soft magnetic material can be effectively reduced (for example, the complex dielectric constant is reduced to 27.5-34), and the impedance matching and microwave absorption performance of the material are further improved.
Example 1:
the embodiment provides a multi-shell structure rare earth soft magnetic material, which comprises the following raw materials: sm2+0.01Fe14B+Nd0.7Cu0.3The preparation method of the rare earth soft magnetic material with the multi-shell structure comprises the following steps:
(1) preparing materials: according to the design composition Sm of the main phase alloy2+0.01Fe14B, secondary alloy design component Nd0.7Cu0.3The method comprises the following steps of proportioning samarium, neodymium, pure iron, copper and ferroboron, and removing oxide skin on the surface of raw materials before proportioning;
(2) smelting: respectively smelting the proportioned raw materials into ingots under the protection of argon, keeping electromagnetic stirring in the smelting process, and casting the molten alloy raw materials in a double-sided water-cooled copper mold;
(3) quick quenching and belt throwing: and preparing the main-phase alloy cast ingot into a nanocrystalline rapid quenching belt by a melt rapid quenching method. The melt-spun temperature is 1420 ℃, and the linear velocity of the high-speed rotating molybdenum roller is 28 m/s;
(4) homogenizing heat treatment: packaging the auxiliary alloy cast ingot in a vacuum quartz tube, and carrying out homogenization heat treatment at 550 ℃ for 48 h;
(5) coarse crushing: grinding and crushing the main alloy rapid quenching belt and the heat-treated auxiliary alloy cast ingot respectively, wherein the grain size (average value of grain diameter) D after coarse crushingave＝100～110μm；
(6) Mixing powder: mixing the coarsely crushed main and auxiliary alloys respectively according to the weight percentage of 5% and 10% of the auxiliary alloys for 120 min;
(7) hot pressing: pressing the uniformly mixed main and auxiliary alloys into a full-density magnetic block in a hot pressing furnace, wherein the hot pressing temperature is 700 ℃;
(8) thermal deformation: thermally deforming the hot-pressed magnetic block at 830 ℃ and 200MPa, wherein particles in the magnetic block after thermal deformation are distributed in a sheet shape, as shown in FIG. 2;
(9) and (3) heat treatment: carrying out heat treatment on the thermally deformed magnetic block at 500 ℃ for 2h, and carrying out water cooling and discharging after the heat treatment;
(10) crushing: crushing the heat-treated magnetic blocks into particles smaller than 100 microns by a coarse crusher, and then carrying out ball milling treatment on the coarse crushed magnetic powder under the protection of 3% of antioxidant, wherein the ball milling rotation speed is 450rpm, and the ball milling time is 8 hours; obtaining magnetic powder particles (namely the rare earth soft magnetic material with a multi-shell structure) after crushing; the morphology of the magnetic powder particles is shown in fig. 3. The average length of the magnetic powder particles is about 4 mu m, and the thickness of the magnetic powder particles is 200-300 nm.
Example 2:
the embodiment provides a multi-shell structure rare earth soft magnetic material, which comprises the following raw materials: sm2+0.01Fe14B+Ce0.5Fe0.2Cu0.3The preparation method of the rare earth soft magnetic material with the multi-shell structure comprises the following steps:
(1) preparing materials: according to the design composition Sm of the main phase alloy2+0.01Fe14B, design constituent of the secondary alloy Ce0.5Fe0.2Cu0.3The method comprises the following steps of proportioning samarium, cerium, pure iron, copper and ferroboron, and removing oxide skin on the surface of raw materials before proportioning;
(2) smelting: respectively smelting the proportioned raw materials into ingots under the protection of argon, keeping electromagnetic stirring in the smelting process, and casting the molten alloy raw materials in a double-sided water-cooled copper mold;
(3) quick quenching and belt throwing: preparing a nanocrystalline rapid quenching belt from the main phase alloy ingot and the auxiliary alloy ingot by a melt rapid quenching method; the melt-spinning temperature of the main phase alloy is 1420 ℃, the melt-spinning temperature of the auxiliary alloy is 950 ℃, and the linear speed of the high-speed rotating molybdenum roller is 28 m/s;
(4) coarse crushing: grinding and crushing the main alloy rapid quenching zone and the auxiliary alloy rapid quenching zone respectively, wherein the grain size D is obtained after coarse crushingave＝120μm；
(6) Mixing powder: mixing the coarsely crushed main and auxiliary alloys according to the weight ratio of 1% and 3% of the auxiliary alloys respectively for 60 min;
(7) hot pressing: pressing the uniformly mixed main and auxiliary alloys into a full-density magnetic block in a hot pressing furnace, wherein the hot pressing temperature is 700 ℃;
(8) thermal deformation: thermally deforming the hot-pressed magnetic block at 830 ℃ and 200MPa, wherein particles in the magnetic block after thermal deformation are distributed in a sheet shape;
(9) and (3) heat treatment: carrying out heat treatment on the thermally deformed magnetic block at 800 ℃ for 30min, and carrying out water cooling and discharging after the heat treatment;
(10) crushing: crushing the heat-treated magnetic blocks into particles smaller than 100 microns by a coarse crusher, and then carrying out jet milling treatment on the coarse crushed magnetic powder under the protection of 1% antioxidant to obtain the multi-shell-layer structure rare earth soft magnetic material. The average length of the magnetic powder particles is about 6 mu m, and the thickness of the magnetic powder particles is 350-400 nm.
Example 3
The embodiment provides a multi-shell structure rare earth soft magnetic material, which comprises the following raw materials: er2+0.01Fe14B+Pr0.5Al0.5. The preparation method of the rare earth soft magnetic material with the multi-shell structure is almost the same as that of the embodiment 1, and the difference is only that:
(3) the melt-spun temperature is 1550 ℃, and the linear speed of the high-speed rotating molybdenum roller is 25 m/s.
(4) Carrying out homogenization heat treatment at 600 ℃ for 72 h;
(5) in (D)ave＝110μm。
(6) In the formula, the weight of the auxiliary alloy accounts for 1 percent and 5 percent. Mixing the powders respectively for 60 min.
(7) And the hot pressing temperature is 750 ℃.
(8) In the method, the hot-pressing magnetic block is subjected to thermal deformation treatment at 850 ℃ and 200 Mpa;
(9) in the method, the thermally deformable magnetic block is subjected to heat treatment at 600 ℃ for 1 h.
(10) The average length of the magnetic powder particles is about 2 μm, and the thickness is 200 nm.
Example 4
The embodiment provides a multi-shell structure rare earth soft magnetic material, which comprises the following raw materials: tm is2+0.015Fe14B+Y0.65Ga0.35. The preparation method of the rare earth soft magnetic material with the multi-shell structure is almost the same as that of the embodiment 1, and the difference is only that:
(3) the melt-spun temperature was 1350 ℃ and the linear velocity of the high-speed rotating molybdenum roller was 45 m/s.
(4) Carrying out homogenization heat treatment at 600 ℃ for 72 h;
(5) in (D)ave＝100μm。
(6) In the weight ratio of the secondary alloy, 2 percent and 8 percent. Mixing the powders respectively for 100 min.
(7) The hot pressing temperature is 700 ℃.
(8) In the method, the hot-pressing magnetic block is subjected to thermal deformation treatment at 780 ℃ and 200 MPa;
(9) in the method, the thermally deformable magnetic block is subjected to heat treatment at 550 ℃ for 1 h.
(10) In the magnetic powder, the average length of the magnetic powder particles is about 4.5 μm, and the thickness is 400-450 nm.
The results of the tests on the high-frequency magnetic properties of the materials before and after the modification of the prealloys of examples 1 to 4 are shown in Table 1, and it can be seen from the table that the rare earth magnetic particles modified with the prealloy have a wider bandwidth and a lower complex dielectric constant, and that the larger the addition amount of the prealloy, the larger the bandwidth and the smaller the complex dielectric constant.
TABLE 1 high frequency Performance of rare earth magnetic particle composites (vol.50%) before and after Co-alloy modification of examples 1-4
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (10)
1. The rare earth soft magnetic material with the multi-shell structure is characterized in that the rare earth soft magnetic material with the multi-shell structure is a core-shell structure consisting of a main phase core and two shell layers, and the two shell layers are a first shell layer and a second shell layer in sequence along the direction from the main phase core to the shell layers;
the main phase inner core has easy plane shape anisotropy and easy plane magnetocrystalline anisotropy, and the directions of the two anisotropy fields are consistent;
the first shell layer is a phase with easy plane shape anisotropy and easy conical surface magnetocrystalline anisotropy;
the second shell layer is a rare earth-rich phase oxide layer.
2. The multi-shell structure rare earth soft magnetic material according to claim 1,
the multi-shell structure rare earth soft magnetic material is integrally flaky, and comprises a main phase core (1), a first shell (2) wrapping the main phase core (1) and a second shell (3) wrapping the first shell (2); the thickness direction section of the flaky multi-shell structure rare earth soft magnetic material is of a 5-layer structure and sequentially comprises a second shell (3), a first shell (2), a main phase core (1), a first shell (2) and a second shell (3).
3. The multi-shell structure rare earth soft magnetic material according to claim 2,
the main phase core (1) mainly comprises R, Fe and B;
the components of the first shell layer (2) mainly comprise R, R', Fe and B;
the components of the second shell layer mainly comprise R, R', M, O and Fe;
r is Sm (samarium), Er (erbium), Tm (thulium) one or more, R' is praseodymium (Pr), neodymium (Nd), cerium (Ce), lanthanum (La), yttrium (Y) one or more, M is copper, aluminium, gallium, niobium, zirconium, iron in one or more.
4. The rare earth soft magnetic material of multi-shell structure as claimed in claim 3, wherein the chemical formula of the main phase core (1) is represented by R in terms of atomic ratio2Fe14B; the chemical formula of the first shell layer (2) is expressed as (RR')2Fe14B。
5. The multi-shell structure rare earth soft magnetic material as claimed in claim 1, wherein the raw material for preparing the multi-shell structure rare earth soft magnetic material comprises a main phase alloy and an auxiliary alloy; the chemical formula of the main phase alloy is expressed as R according to atomic ratio2+xFe14B; the chemical formula of the secondary alloy is R 'according to the atomic ratio'yM1-y。
6. The rare earth soft magnetic material of a multi-shell structure according to claim 5, wherein x is 0.01. ltoreq. x.ltoreq.0.4, and y is 0.3. ltoreq. y.ltoreq.1.
7. A preparation method of a multi-shell structure rare earth soft magnetic material is characterized in that the preparation method is used for preparing the multi-shell structure rare earth soft magnetic material as claimed in claims 1-6, the preparation method takes a main phase alloy comprising a main phase and a rare earth-rich phase and an auxiliary alloy containing rare earth elements as raw materials, the auxiliary alloy is used for modifying the main phase of the main phase alloy part through hot pressing, hot deformation and heat treatment processes to form a core-shell structure of a main phase core, a first shell and a rare earth-rich phase layer, and the rare earth-rich phase layer is oxidized to obtain the multi-shell structure rare earth soft magnetic material with two shell structures, wherein the multi-shell structure rare earth soft magnetic material comprises the main phase core, the first shell and a rare earth-rich phase oxide layer.
8. The method for preparing a rare earth soft magnetic material with a multi-shell structure according to claim 7, comprising:
step 1, mixing powder: mixing the main alloy powder and the auxiliary alloy powder;
step 2, hot pressing: pressing the mixed alloy powder into a full-density isotropic block;
step 3, thermal deformation: carrying out thermal deformation treatment on the full-density isotropic block body subjected to thermal pressing to obtain a thermal deformation magnetic block;
step 4, heat treatment: performing heat treatment on the thermally deformed magnetic block within the temperature range of 400-900 ℃ to enable the auxiliary alloy to be fully diffused into the main phase alloy to form a main phase kernel and a first shell;
step 5, crushing: and (4) crushing the magnetic blocks obtained in the step (4) into magnetic powder particles, and oxidizing the surfaces of the magnetic powder particles into rare earth-rich phase oxide layers to obtain the rare earth soft magnetic material with the multi-shell structure.
9. The method for preparing a rare earth soft magnetic material with a multi-shell structure according to claim 8, wherein in the step 1, the weight ratio of the auxiliary alloy powder in the mixed powder is more than 0 and less than or equal to 10%.
10. The method for preparing the rare earth soft magnetic material with the multi-shell structure according to claim 7, wherein in the step 3, the temperature of thermal deformation is 780-850 ℃.
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