KR20210103378A - Magnetic particles and method for manufacturing the same - Google Patents

Abstract

Provided is a manufacturing method of magnetic particles. The manufacturing method of the magnetic particles may comprise: a step of preparing a source solution wherein a first precursor comprising a rare earth element, a second precursor comprising a metal element, and a dispersant are mixed; a step of forming oxide particles comprising the rare earth element and the metal element by hydrothermal synthesizing the source solution; a step of manufacturing the base particles by coating the oxide particles with an additive comprising calcium; a step of calcining the base particles to manufacture a preliminary magnetic body wherein a calcium monoxide (CaO) in which the additive is thermally decomposed and the oxide particles are reacted; and a step of reducing the preliminary magnetic material to manufacture the magnetic particles comprising a compound of the rare earth element and the metal element. Therefore, the present invention is capable of allowing the magnetic properties of the magnetic particles to be improved.

Description

Magnetic particles and method for manufacturing the same

The present invention relates to magnetic particles and a method for manufacturing the same, and more particularly, to magnetic particles for reducing the oxide particles by forming oxide particles through a source solution in which a precursor containing a rare earth element and a precursor containing a metal element are mixed, and a manufacturing method thereof related to the method.

Permanent magnet materials have the characteristic of mutually converting electrical energy and magnetic energy, so they are essential in industries such as automobiles, aerospace, and robots, including the energy industry, which require devices such as generators and motors. The characteristics of permanent magnet materials are expressed in terms of maximum magnetic energy, and as the maximum magnetic energy product is higher, the volume and weight of permanent magnet materials in the generator and motor can be reduced. For efficiency, weight reduction and miniaturization, research has been conducted in the direction of developing materials of new composition or processes capable of exhibiting high properties.

In order to break through the currently reached limit of material properties of permanent magnets, the search for new compositions or the development of technologies in the direction of controlling the nanostructure of existing materials are being actively developed. After preparing the mother phase through the process of However, in this case, there is a difficulty in preventing the deterioration of properties due to the inflow of impurities during the process or the oxidation of the permanent magnet material.

In order to overcome the limitations of the top-down manufacturing method, a bottom-up manufacturing method such as a chemical approach such as thermal decomposition or hydrothermal synthesis or a physical approach to obtain nanoparticles by vaporizing a material using plasma energy, ferrite, rare earth, manganese Research to obtain nanoparticles of magnetic materials such as these has been extensively conducted.

One technical problem to be solved by the present invention is to provide a magnetic particle capable of manufacturing oxide particles used as a material of a permanent magnet at a lower temperature than a conventional magnetic particle manufacturing process, and a manufacturing method thereof.

Another technical problem to be solved by the present invention is to provide magnetic particles having improved magnetic properties and a method for manufacturing the same.

Another technical problem to be solved by the present invention is that problems associated with the crushing process (for example, inflow of impurities in the crushing medium, oxidation of rare earth elements due to heat in the crushing process, reduction of alignment due to the crushing process, etc.) An object of the present invention is to provide resolved magnetic particles and a method for manufacturing the same.

Another technical problem to be solved by the present invention is to provide magnetic particles in which coarsening of particles due to an increase in reduction heat treatment temperature is prevented, and a method for manufacturing the same.

Another technical problem to be solved by the present invention is to provide magnetic particles capable of selectively controlling the optimum particle size for various materials and a method for manufacturing the same.

The technical problem to be solved by the present invention is not limited to the above.

In order to solve the above-described technical problems, the present invention provides a method of manufacturing magnetic particles.

According to an embodiment, the method for manufacturing the magnetic particles includes preparing a source solution in which a first precursor containing a rare earth element, a second precursor containing a metal element, and a dispersant are mixed, and hydrothermal synthesis of the source solution. , forming oxide particles including the rare earth element and the metal element, coating the oxide particles with an additive containing calcium to prepare base particles, calcining the base particles, so that the additive is thermally decomposed monoxide The method may include preparing a preliminary magnetic body in which calcium (CaO) and the oxide particles are reacted, and reducing the preliminary magnetic body to prepare magnetic particles including a compound of the rare earth element and the metal element.

According to an embodiment, in the step of manufacturing the magnetic particles by reducing the preliminary magnetic material, the preliminary magnetic material is heat-treated and reduced, and the heat treatment temperature of the preliminary magnetic material is greater than 900°C and less than 1000°C.

According to an embodiment, in the step of preparing the preliminary magnetic body by calcining the base particles, the base particles are calcined in an air atmosphere, and the magnetic particles are first magnetic particles of a hard magnetic phase and a first magnetic particle of a soft magnetic phase. 2 may contain magnetic particles.

According to an embodiment, in the step of preparing the preliminary magnetic material by calcining the base particles, the base particles are calcined in a hydrogen (H ₂ ) atmosphere, and the magnetic particles are composite magnetic particles in which a hard magnetic phase and a soft magnetic phase are mixed. may include.

According to an embodiment, in the step of calcining the base particles to prepare the preliminary magnetic body, the calcination temperature of the base particles may include 700° C. or higher.

According to one embodiment, when the content of the metal element relative to the rare earth element is controlled to be 7.3 at% to 8.5 at% in the preparing of the source solution, the magnetic particles may include a _{hard magnetic phase of Sm 2} Co _{17 .} can

According to an embodiment, when the content of the metal element relative to the rare earth element is controlled to be 4.5 at% to 5.0 at% in the step of preparing the source solution, the magnetic particles may include a _{hard magnetic phase of SmCo 5 .} .

According to an embodiment, the additive may include calcium acetate monohydrate, Ca(C ₂ H ₃ O ₂ )·H ₂ O).

According to an embodiment, the rare earth element includes any one of samarium (Sm), neodymium (Nd), lanthanum (La), cerium (Ce), and praseodymium (Pr), and the metal element is cobalt (Co). ), iron (Fe), copper (Cu), zirconium (Zr), chromium (Cr), tin (Sn), antimony (Sb), hafnium (Hf), manganese (Mn), bismuth (Bi), and nickel It may include any one of (Ni).

According to an embodiment, the method of manufacturing the magnetic particles may further include removing the calcium monoxide (CaO) from which the additive is thermally decomposed after the manufacturing of the magnetic particles.

According to one embodiment, in the step of manufacturing the magnetic particles by reducing the preliminary magnetic body, the preliminary magnetic body is heat-treated together with a reducing agent, in a state in which the preliminary magnetic body is disposed on the reducing agent, the preliminary magnetic body is heat-treated may include

In order to solve the above technical problems, the present invention provides a magnetic particle.

According to an embodiment, the magnetic particles include a samarium (Sm)-cobalt (Co) compound, a first magnetic particle having a hard magnetic phase, and independent of the first magnetic particles, including cobalt (Co), It may include a second magnetic particle having a soft magnetic phase.

According to an embodiment, the first magnetic particles may include any one of _{Sm 2} Co ₁₇ , Sm ₂ Co _17+x (x>0), or SmCo _{5 .}

According to another embodiment, the magnetic particles include composite magnetic particles in which a hard magnetic phase including a samarium (Sm)-cobalt (Co) compound and a soft magnetic phase including a cobalt (Co) element are mixed, the samarium (Sm) )- The cobalt (Co) compound may include any one of _{Sm 2} Co ₁₇ , Sm ₂ Co _17+x (x>0), or SmCo _{5 .}

The method for manufacturing magnetic particles according to an embodiment of the present invention includes preparing a source solution in which a first precursor containing a rare earth element, a second precursor containing a metal element, and a dispersant are mixed, and hydrothermal synthesis of the source solution. , forming oxide particles including the rare earth element and the metal element, coating the oxide particles with an additive containing calcium to prepare base particles, calcining the base particles, so that the additive is thermally decomposed monoxide The method may include preparing a preliminary magnetic body in which calcium (CaO) and the oxide particles are reacted, and reducing the preliminary magnetic body to prepare magnetic particles including a compound of the rare earth element and the metal element.

Accordingly, oxide particles can be manufactured at a relatively low temperature compared to the conventional methods for manufacturing a permanent magnet. In addition, since the hard magnetic phase is formed through the reduction process after the crushing process, compared with the conventional particle manufacturing process in which the crushing process is performed after the hard magnetic phase is formed, problems associated with crushing (for example, inflow of impurities in the crushing medium, Oxidation of rare earth elements due to the heat of the crushing process, reduction of alignment due to the crushing process, etc.) can be solved. In addition, since bonding and coarsening between particles is prevented by the additive, the optimum particle size for various materials can be selectively controlled, and magnetic properties of the magnetic particles can be improved.

1 is a flowchart illustrating a method of manufacturing magnetic particles according to a first embodiment of the present invention.
2 is a view showing a manufacturing process of magnetic particles according to the first embodiment of the present invention.
3 is a flowchart illustrating a method of manufacturing magnetic particles according to a second embodiment of the present invention.
4 is a view showing a manufacturing process of magnetic particles according to a second embodiment of the present invention.
5 is an image showing oxide particles formed in the manufacturing process of magnetic particles according to an embodiment of the present invention.
6 is an image showing a mapping result of magnetic particles according to an embodiment of the present invention.
7 to 10 are images illustrating a change in a preliminary magnetic material according to a change in a calcination temperature during a manufacturing process of magnetic particles according to an embodiment of the present invention.
11 and 12 are images illustrating a change in magnetic particles according to a change in the reduction heat treatment temperature in the manufacturing process of the magnetic particles according to an embodiment of the present invention.
13 is a graph illustrating a change in the structure of magnetic particles according to a change in a reduction heat treatment temperature in a manufacturing process of magnetic particles according to an embodiment of the present invention.
14 and 15 are graphs illustrating a change in properties of magnetic particles according to a change in a reduction heat treatment temperature in a manufacturing process of magnetic particles according to an embodiment of the present invention.
16 is an XRD graph illustrating a change in properties of a preliminary magnetic material according to a change in a calcination temperature during a manufacturing process of magnetic particles according to an embodiment of the present invention.
17 is a VSM graph illustrating a change in characteristics of a preliminary magnetic material according to a change in a calcination temperature during a manufacturing process of magnetic particles according to an embodiment of the present invention.
18 is an image illustrating a change in the size of oxide particles according to a change in a source solution preparation process in a manufacturing process of magnetic particles according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical spirit of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

In this specification, when a component is referred to as being on another component, it may be directly formed on the other component or a third component may be interposed therebetween. In addition, in the drawings, thicknesses of films and regions are exaggerated for effective description of technical content.

In addition, in various embodiments of the present specification, terms such as first, second, third, etc. are used to describe various components, but these components should not be limited by these terms. These terms are only used to distinguish one component from another. Accordingly, what is referred to as a first component in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein also includes a complementary embodiment thereof. In addition, in the present specification, 'and/or' is used to mean including at least one of the elements listed before and after.

In the specification, the singular expression includes the plural expression unless the context clearly dictates otherwise. In addition, terms such as "comprise" or "have" are intended to designate that a feature, number, step, element, or a combination thereof described in the specification is present, and one or more other features, numbers, steps, configuration It should not be construed as excluding the possibility of the presence or addition of elements or combinations thereof. Also, in the present specification, the term “connection” is used to include both indirectly connecting a plurality of components and directly connecting a plurality of components.

In addition, in the following description of the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

1 is a flowchart illustrating a method of manufacturing magnetic particles according to a first embodiment of the present invention, and FIG. 2 is a diagram illustrating a manufacturing process of magnetic particles according to a first embodiment of the present invention.

1 and 2 , a source solution in which a first precursor, a second precursor, a solvent, and a dispersant are mixed may be prepared ( S110 ). The first precursor may include a rare earth element. For example, the rare earth element may include any one of samarium (Sm), neodymium (Nd), lanthanum (La), cerium (Ce), and praseodymium (Pr). For example, the first precursor may include samarium triacetylacetonate hydrate (Samarium(III) acetylacetonate hydrate, Sm(C ₅ H ₇ O ₆ ) ₃ , xH ₂ O).

Alternatively, the second precursor may include a metal element. For example, the metal element is cobalt (Co), iron (Fe), copper (Cu), zirconium (Zr), chromium (Cr), tin (Sn), antimony (Sb), hafnium (Hf), manganese (Mn), bismuth (Bi), and may include any one of nickel (Ni). For example, the second precursor may include cobalt triacetylacetonate (Cobalt(III) acetylacetonate, Co(C ₅ H ₇ O ₂ ) ₃ ).

For example, the solvent may include methanol (CH ₃ OH). For example, the dispersant may include oleylamine (C ₁₈ H ₃₇ N).

According to an embodiment, in the step of preparing the source solution, the content of the second precursor compared to the first precursor may be controlled. Accordingly, the content of the metal element (eg, cobalt) compared to the rare earth element (eg, samarium) may be controlled. Specifically, the content of the metal element (eg, cobalt) relative to the rare earth element (eg, samarium) is 7.3 at% to 8.5 at% (eg, samarium 10.5 to 12.0 at%, cobalt 88.0 to 89.5 at%) can be controlled. In this case, the magnetic particles to be described later may have a hard magnetic phase of _{Sm 2} Co _{17 .} In contrast, the content of the metal element (eg, cobalt) relative to the rare earth element (eg, samarium) is 4.5 at% to 5.0 at% (eg, samarium 16.7 to 18.0 at%, cobalt 82.0 to 83.3 at%) can be controlled. In this case, the magnetic particles to be described later may have an _{SmCo 5 hard magnetic phase.}

By hydrothermal synthesis of the source solution, oxide particles (100, for example, Sm-Co oxide) including the rare earth element (eg, samarium) and the metal element (eg, cobalt) may be formed (S120). More specifically, the oxide particles 100 may be formed by heating the source solution to a temperature of 215° C. at a temperature increase rate of 10° C./min and then heat-treating it in the air for 1 hour.

According to an embodiment, the size of the oxide particles 100 may be controlled by controlling the process conditions of the source solution preparation step. Specifically, in the step of preparing the source solution, when diethylene glycol as well as _{the oleylamine (C 18} H _{37 N) is further added as the dispersant, the oxide particles (} 100) can be reduced. In addition, in the step of preparing the source solution, the size of the oxide particles 100 may be reduced by reducing the total content of the first precursor and the second precursor. For example, when the total content of the first precursor and the second precursor is reduced by half, the size of the oxide particle 100 may be reduced by half.

An additive may be coated on the oxide particles 100 (S130). Accordingly, the base particle 200 coated with the additive may be formed around the oxide particle 100 . According to an embodiment, the additive may include calcium (Ca). For example, the additive may include calcium acetate monohydrate (Ca(C ₂ H ₃ O ₂ )·H ₂ O). Alternatively, for another example, the additive may include a calcium compound such as calcium monoxide (CaO).

The additive may prevent diffusion of the magnetic particles 400 and prevent coarsening of the magnetic particles 400 in the manufacturing of the magnetic particles 400 by reducing the preliminary magnetic material 300 , which will be described later. In the case of the magnetic particles 400, as the particles are coarsened, a problem in that magnetic properties are deteriorated may occur. However, as described above, in the method of manufacturing the magnetic particles according to the embodiment, as the oxide particles 100 are coated with the additive, the coarsening phenomenon of the magnetic particles 400 is prevented. ) can be reduced.

The first precursor (eg, Sm(acac) ₃ ) and the second precursor (eg, Co(acac) ₃ ) used in preparing the source solution, and the additive used in the step of coating The specific content of the additive (eg, Ca(ac) ₂ ) is summarized in <Table 1> below.

Magnetic Powder Phase Sm ₂ Co ₁₇ SmCo ₅ Sm(acac) ₃ content (g) 0.0560 0.0895 Co(acac) ₃ content (g) 0.3563 0.3295 Ca(ac) ₂ content (g) 0.35 0.35 Sm: Co: Ca ratio (at%) 1: 8: 17.6 1: 4.5: 11

The base particle 200 may be calcined to manufacture the preliminary magnetic material 300 ( S140 ). For example, the preliminary magnetic material 300 may include the rare earth element (eg, samarium)-the metal element (eg, cobalt)-calcium oxide (Sm-Co-Ca-O). .

Specifically, when the base particle 200 is calcined, the additive may be thermally decomposed. The additive may be thermally decomposed in the order of calcium _{carbonate (CaCO 3} ) and calcium monoxide (CaO) according to the calcination temperature. When the additive is decomposed into the calcium monoxide (CaO), the calcium monoxide (CaO) and the oxide particles 100 may react to form the preliminary magnetic body 300 . When the calcium monoxide (CaO) and the oxide particles 100 are reacted, the constituent elements (eg, samarium, cobalt, calcium, and oxygen) of the preliminary magnetic body 300 are uniformly rearranged, so that the preliminary magnetic body 300 is uniformly rearranged. The constituent elements of 300 (eg, samarium, cobalt, calcium, and oxygen) may be homogeneously mixed. Due to this, the magnetic properties of the magnetic particles 400 to be described later may be improved.

For example, the base particles 200 may be calcined at a temperature of 700 °C or higher. In this case, the additive may be thermally decomposed to generate the calcium monoxide (CaO), and the calcium monoxide (CaO) may react with the oxide particles 100 . Alternatively, when the base particles 200 are calcined at a temperature of less than 700° C., the calcium monoxide (CaO) may not be generated from the additive. Accordingly, the rearrangement of the constituent elements (eg, samarium, cobalt, calcium, oxygen) of the preliminary magnetic material 300 does not occur, so that the magnetic properties of the magnetic particles 400 to be described below are deteriorated. can

According to an embodiment, the base particles 200 may be calcined in an air atmosphere. In this case, the metal element (eg, cobalt) included in the oxide particle 100 may react with calcium (Ca) included in the additive, and the shape of the base particle 200 may be deformed. That is, the preliminary magnetic material 300 may have a different shape from the base particle 200 . For example, as shown in FIG. 2 , the base particle 200 has a powder form composed of a plurality of particles, while the preliminary magnetic material 300 is composed of a plurality of rods. It may have a powder form.

The preliminary magnetic material 300 may be reduced to produce magnetic particles 400 (S150). According to an embodiment, the preliminary magnetic material 300 may be reduced by heat treatment with a reducing agent. For example, the reducing agent may include any one of calcium (Ca) or calcium hydride (CaH _{2 ).}

Specifically, in a state in which the preliminary magnetic body 300 is disposed on the reducing agent, the preliminary magnetic body 300 may be heat-treated. In this case, despite an increase in the batch size of the magnetic particles 400 , the size of the magnetic particles 400 may be maintained substantially constant. On the other hand, when heat treatment is performed in a state in which the reducing agent and the preliminary magnetic material 300 are mixed, the size of the magnetic particles 400 may increase as the batches of the magnetic particles 400 increase. As a result, a problem in which the coercive force of the magnetic particles 400 is reduced may occur.

The magnetic particles 400 may include first magnetic particles 410 and second magnetic particles 420 that are independently distributed from each other. According to an embodiment, the first magnetic particles 410 may have a hard magnetic phase. For example, the first magnetic particles 410 may include Sm ₂ Co ₁₇ . Specifically, in the step of preparing the source solution, the content of the metal element (eg, cobalt) compared to the rare earth element (eg, samarium) is controlled to be 7.3 at% to 8.5 at%, so that the first magnetic Particles 410 may include Sm ₂ Co ₁₇ . Alternatively, as another example, the first magnetic particles 410 may include SmCo ₅ . Specifically, in the step of preparing the source solution, the content of the metal element (eg, cobalt) relative to the rare earth element (eg, samarium) is controlled to be 4.5 at% to 5.0 at%, so that the first magnetic Particles 410 may include SmCo ₅ .

According to an embodiment, the second magnetic particles 420 may have a soft magnetic phase. For example, the second magnetic particles 420 may include the metal element (eg, cobalt).

According to an embodiment, in the step of reducing the preliminary magnetic body 300 , the magnetic properties of the magnetic particles 400 may be improved by controlling the heat treatment temperature of the preliminary magnetic body 300 . Specifically, the preliminary magnetic material 300 may be reduced by heat treatment at a temperature greater than 900°C and less than 1000°C. In this case, the coercive force of the magnetic particles 400 may be improved. On the contrary, when the preliminary magnetic material 300 is heat-treated at a temperature of 900° C. or less, a problem in which the maximum magnetic energy product as well as the coercive force decreases may occur. In addition, when the preliminary magnetic material 300 is heat-treated at a temperature of 1000° C. or higher, the maximum magnetic energy product increases, but a problem of deterioration due to overgrowth of particles occurs, and magnetic properties such as coercive force may decrease. .

After the preliminary magnetic material 300 is reduced to prepare the magnetic particles 400 , the calcium monoxide (CaO) in which the additive is thermally decomposed may be removed. For example, by washing the magnetic particles 400 in which the preliminary magnetic material 300 is reduced with a mixed solution of _{ammonium chloride (NH 4} Cl) and methanol (CH _{3 OH),} The calcium monoxide (CaO) may be removed.

In order to obtain a permanent magnet having a high maximum magnetic energy product, microstructural properties such as high density, degree of anisotropy in the crystal direction, and size of crystal grains must be controlled. Assuming that permanent magnets have the same volume and exist at different densities, the maximum magnetic energy product is high in the case of permanent magnets with high densities. A difference in energy occurs, resulting in a difference in magnetic properties. In addition, as the size of the grains constituting the permanent magnet is closer to the size of the single sphere, the size of the coercive force, a characteristic that suppresses the rotation of the spin, increases, thereby increasing the maximum magnetic energy product, and the shape magnetic anisotropy according to the shape of the grain The magnetic properties of permanent magnets may be changed by the influence of

In consideration of these factors, as a conventional method for manufacturing a permanent magnet, a die-upset process and a particle manufacturing process are mainly used. The die-upset process is applied only to Nd-Fe-B permanent magnets and consists of four processes. First, an Nd-Fe-B ribbon is manufactured using a rapid solidification process, and stress is applied to the manufactured ribbon through cold forming, thereby causing rotation of crystals constituting the ribbon. By applying stress through cold forming Nd-Fe-B forming, rotation of the crystals constituting the ribbon occurs. In the cold-formed Nd-Fe-B compact, additional crystal rotation occurs immediately through hot forming to increase the anisotropy of the compact, and at the same time, a compact made of uniform crystals is produced by the growth of crystals by thermal energy. Finally, the hot-formed compact is placed in a mold larger than the diameter of the compact, and then crystal grains are deformed by applying a large stress to the compact, thereby completing a Nd-Fe-B permanent magnet with high properties. The die-upset process can impart high density and anisotropy to permanent magnets through a series of processes that apply high stress and heat, but the types of materials that can be applied are limited and nanostructures such as exchange magnetic coupling are delicate. It is difficult to apply when it has to be controlled properly, and there are problems in that the maximum magnetic energy that can be obtained is currently limited.

In the case of the conventional particle manufacturing process, a permanent magnet can be manufactured through four processes in general. First, an ingot or ribbon having a matrix of permanent magnet material is manufactured using casting or rapid solidification process, and fine particles are obtained through crushing processes such as ball milling, high energy milling, and jet-milling. Then, in the magnetic field forming process, when a magnetic field is applied to the particles located in the molding mold, the particles are rotated by the magnetic field direction so that each particle has the same crystal direction. When this state is reached, stress is applied to form a molded body having anisotropy in the crystal direction, and finally, a permanent magnet having a high density is manufactured through a sintering process. The permanent magnet manufacturing method through the conventional particle process can be applied to various permanent magnet materials, but a top-down manufacturing method of obtaining particles by crushing the parent phase is used, and in some cases, in order to obtain nanoparticles of high properties, the permanent magnet material matrix Through the crushing process in which high energy is applied, impurities such as crushing medium may be introduced, and oxides are formed on the particle surface by the thermal energy generated in the process to decompose the hard magnetic phase and the hard magnetic phase existing in the permanent magnet. It causes the problem of reducing the fraction of In particular, in the case of rare-earth permanent magnets, since chemical stability is low, more effort is required to suppress the oxidation problem, and if this is not solved, deterioration of the properties of the permanent magnet cannot be avoided.

However, the method of manufacturing magnetic particles according to the first embodiment of the present invention includes the steps of preparing the source solution in which the first precursor including the rare earth element, the second precursor including the metal element, and the dispersant are mixed , hydrothermal synthesis of the source solution to form the oxide particles 100 including the rare earth element and the metal element, coating the oxide particles 100 with an additive containing calcium to form the base particles 200 ), calcining the base particles 200 to prepare the preliminary magnetic material 300 in which calcium monoxide (CaO) in which the additive is thermally decomposed and the oxide particles 100 are reacted, and the preliminary The method may include reducing the magnetic material 300 to prepare magnetic particles including a compound of the rare earth element and the metal element.

Accordingly, the oxide particles 100 can be manufactured at a relatively low temperature compared to the above-described conventional methods for manufacturing a permanent magnet. In addition, since the hard magnetic phase is formed through the reduction process after the crushing process, compared with the conventional particle manufacturing process in which the crushing process is performed after the hard magnetic phase is formed, problems associated with crushing (for example, inflow of impurities in the crushing medium, Oxidation of rare earth elements due to the heat of the crushing process, reduction of alignment due to the crushing process, etc.) can be solved. In addition, since bonding and coarsening between particles is prevented by the additive, the optimum particle size for various materials can be selectively controlled, and magnetic properties of the magnetic particles can be improved.

As described above, the magnetic particles and a manufacturing method thereof according to the first embodiment of the present invention have been described. Hereinafter, a magnetic particle and a manufacturing method thereof according to a second embodiment of the present invention will be described.

3 is a flowchart illustrating a method of manufacturing magnetic particles according to a second embodiment of the present invention, and FIG. 4 is a view showing a manufacturing process of magnetic particles according to a second embodiment of the present invention.

3 and 4, the method for manufacturing magnetic particles according to the second embodiment includes the steps of preparing a source solution (S210), hydrothermal synthesis of the source solution to form oxide particles (S220), Preparing the base particles by coating the oxide particles with an additive (S230), calcining the base particles to prepare a preliminary magnetic body (S240), and reducing the preliminary magnetic body to prepare magnetic particles (S250) may include.

According to an embodiment, preparing a source solution (S210), hydrothermal synthesis of the source solution to form oxide particles (S220), and coating an additive on the oxide particles to prepare base particles (S230) ), preparing the source solution included in the method for manufacturing magnetic particles according to the first embodiment described with reference to FIGS. 1 and 2 (S110), hydrothermal synthesis of the source solution to form oxide particles It may be the same as the step (S120) of preparing the base particles by coating the oxide particles with an additive (S130). Accordingly, a detailed description is omitted.

The step of producing the preliminary magnetic body 300 by calcining the base particle 200 (S240). Also, the method for producing the magnetic particle according to the first embodiment described with reference to FIGS. 1 and 2 includes the It may be the same as the step ( S140 ) of calcining the base particles 200 to prepare the preliminary magnetic body 300 . However, in the method of manufacturing the magnetic particles according to the second embodiment, the base particles 200 may be calcined in a _{hydrogen (H 2 ) atmosphere.} In this case, the preliminary magnetic material 300 has a structure in which the reduced metal element (eg, cobalt) particles and the rare earth element oxide (eg, Sm-O) particles are aggregated of calcium monoxide (CaO). It may have a form disposed on a matrix.

Accordingly, when the preliminary magnetic material 300 is reduced, contact between the aggregated structures may not occur. For this reason, the magnetic particles 400 in which the preliminary magnetic material 300 is reduced may have a state in which a hard magnetic phase and a soft magnetic phase are mixed in one particle. According to an embodiment, the hard magnetic phase may include any one _{of Sm 2} Co _17+x (x>0) or SmCo _{5 .} Alternatively, the soft magnetic phase may include the metal element (eg, cobalt).

That is, the magnetic particles 400 according to the first embodiment include the first magnetic particles 410 of the hard magnetic phase and the second magnetic particles 420 of the soft magnetic phase distributed independently of each other, while the second The magnetic particles 400 according to the embodiment may include composite magnetic particles in which a hard magnetic phase and a soft magnetic phase are mixed in one particle. In this case, the magnetic particles 400 according to the second embodiment may have improved magnetic properties compared to the magnetic particles 400 according to the first embodiment.

In the above, the magnetic particles and the manufacturing method thereof according to an embodiment of the present invention have been described. Hereinafter, specific experimental examples and characteristic evaluation results of the magnetic particles and their manufacturing method according to an embodiment of the present invention will be described.

Preparation of magnetic particles according to the embodiment

40 ml of methanol, cobalt(III) acetylacetonate, Co(C ₅ H ₇ O ₂ ) ₃ ), samarium(III) acetylacetonate hydrate, Sm( C ₅ H ₇ O ₆ ) ₃ , xH ₂ O) was added and dissolved at 300 rpm for 10 minutes using a magnetic bar. After that, 20 ml of oleylamine (C ₁₈ H ₃₇ N) was added to the solution and stirred at 300 rpm for 10 minutes. prepared.

Transfer the source solution to a 100 ml Teflon container, assemble it with a stainless steel hydrothermal container, place the assembly in a box furnace, reach 215°C at a temperature increase rate of 10°C/min, and then in the air for 1 hour. During heat treatment, oxide particles containing Sm-Co were prepared. After the heat treatment was completed, the oxide particles were cooled, 30 ml of ethanol was added, and centrifugation was performed twice for 10 minutes at a speed of 8000 rpm, and the oxide particles obtained through centrifugation were dispersed and stored in the nucleic acid.

In a 250 ml 3-neck flask, 30 ml of 1-octadecene (C ₁₈ H ₃₆ ), calcium acetate monohydrate (Ca(C ₂ H ₃ O ₂ ) H ₂ O), After the oxide particles dispersed in the nucleic acid were added, the temperature was raised to 100° C. while maintaining stirring at a speed of 600 rpm using a magnetic bar, and maintained in an inert gas atmosphere (eg, argon, nitrogen, etc.) for 1 hour. . After removing moisture and nucleic acids by vaporizing them, hexadecyltrimethylammonium hydroxide (25% in methanol, C ₁₉ H ₄₃ NO) was added and maintained at 100° C. for another 30 minutes. The oxide particles were coated with calcium acetic acid monohydrate. Base particles were prepared.

Then, 30 ml of ethanol was added to the base particles, and centrifugation was performed twice for 5 minutes at a speed of 8000 rpm. The base particles obtained through centrifugation were placed in a vacuum atmosphere at room temperature for at least 1 hour to remove moisture and ethanol, and then placed in an alumina crucible and placed in an electric furnace to reach 700°C at a temperature increase rate of 10°C/min. A homogeneous Sm-Co-Ca-O preliminary magnetic material was prepared by calcination heat treatment in the atmosphere for 1 hour.

After the prepared preliminary magnetic material is placed in a stainless steel crucible, it is reached with calcium or calcium hydride at a temperature increase rate of 5-10°C/min to 700-1000°C, and then in an inert atmosphere (eg, argon or The magnetic particles according to the above example were prepared by performing a reduction heat treatment in nitrogen, etc.).

Finally, the magnetic particles _{were washed with a mixed solution of ammonium chloride (NH 4} Cl) and methanol (CH- ₃ OH) to remove calcium monoxide (CaO), and then dried in an oven at 60° C. for 1 hour.

5 is an image showing oxide particles formed in the manufacturing process of magnetic powder according to an embodiment of the present invention.

Referring to FIGS. 5A and 5B , a scanning electron microscope (SEM) image of the oxide particles formed in the manufacturing process of the magnetic powder according to the embodiment is shown. Fig. 5 (a) is an image at a magnification of 500 nm, and Fig. 5 (b) shows an image at a magnification of 2 μm. Referring to FIGS. 5A and 5B , it was confirmed that the oxide particles had a diameter of 1 μm or less, and each oxide particle was dispersed and disposed.

6 is an image showing a mapping result of magnetic powder according to an embodiment of the present invention.

Referring to (a) to (d) of Figure 6, the STEM (Scanning Transmission Electron Microscope) image and mapping results of the oxide particles formed in the manufacturing process of the magnetic powder according to the above example are shown. As can be seen from (a) to (d) of Figure 6, it was confirmed that samarium and cobalt elements were uniformly distributed in one oxide (Sm-Co-O) particle.

7 to 10 are images illustrating a change in a preliminary magnetic material according to a change in a calcination temperature during a manufacturing process of magnetic particles according to an embodiment of the present invention.

7 to 10 , the base powder state ( FIG. 7 ), the preliminary magnetic body state in which the base powder is calcined at a temperature of 200° C. ( FIG. 8 ), the base powder formed in the manufacturing process of the magnetic particles according to the embodiment Images by backscattered electrons of a scanning electron microscope are shown for the preliminary magnetic body state calcined at a temperature of 400° C. (FIG. 9), and the preliminary magnetic body state in which the base powder was calcined at a temperature of 700° C. (FIG. 10). (a) and (b) of each figure show images at different magnifications (500 nm, 2 μm).

As can be seen in FIG. 7 , in the case of the base particles coated with calcium acetic acid monohydrate on the oxide particles, it was confirmed that the oxide particles were distributed in a matrix of calcium acetic acid monohydrate. On the other hand, as can be seen in FIGS. 8 to 10 , as the calcination temperature of the base particles increases, _{decomposition proceeds in the order of calcium acetic acid, calcium carbonate (CaCO 3} ), and calcium oxide (CaO), and the preliminary calcined at a temperature of 700° C. It was confirmed that the magnetic material had the form of an oxide in which samarium, cobalt, and calcium were homogeneously mixed.

11 and 12 are images illustrating changes in magnetic particles according to a change in reduction heat treatment temperature in the manufacturing process of magnetic particles according to an embodiment of the present invention.

11 and 12 , the magnetic particles according to the embodiment were prepared, but the reduction heat treatment temperature of the preliminary magnetic material was adjusted to 800°C (FIG. 11(a)), 815°C (FIG. 11(b)), 850°C. ℃ (FIG. 11(c)), 900°C (FIG. 12(a)), 950°C (FIG. 12(b)), and 1000°C (FIG. 11(c)), each temperature SEM images were shown for the magnetic particles prepared in . As can be seen in FIGS. 11 and 12 , it was confirmed that the size of the magnetic particles was controlled from about 100 nm to about 1000 nm as the reduction heat treatment temperature of the preliminary magnetic material was changed. Accordingly, it can be seen that the coarsening phenomenon and bonding phenomenon of particles that may occur during the reduction heat treatment process are suppressed.

13 is a graph showing a change in the structure of magnetic particles according to a change in the reduction heat treatment temperature in the manufacturing process of the magnetic particles according to an embodiment of the present invention.

13, but preparing the magnetic particles according to the embodiment, the reduction heat treatment temperature of the preliminary magnetic material is controlled to 800 ℃, 815 ℃, 850 ℃, 900 ℃, 950 ℃, and 1000 ℃, at each temperature X-ray diffraction analysis was performed on the prepared magnetic particles, and the results were shown. As can be seen in FIG. 13 , it was confirmed that the Sm ₂ Co ₁₇ (PDF#01-078-8777) phase was formed under all reduction heat treatment conditions. In addition, it was confirmed that diffraction peaks for impurities and oxides other than the _{Sm 2} Co _{17 phase were not observed.} Accordingly, it was found that the composition of samarium (Sm) and cobalt (Co) of the oxide particles (Sm-Co-O) prepared through hydrothermal synthesis was correctly controlled.

14 and 15 are graphs illustrating a change in properties of magnetic particles according to a change in a reduction heat treatment temperature in a manufacturing process of magnetic particles according to an embodiment of the present invention.

14 and 15, the magnetic particles according to the embodiment are prepared, but the reduction heat treatment temperature of the preliminary magnetic material is controlled to 800°C, 815°C, 850°C, 900°C, 950°C, and 1000°C, each The magnetic susceptibility of the vibration sample was measured and shown for the magnetic particles prepared at a temperature of . The characteristic results of the magnetic particles measured in FIGS. 14 and 15 are summarized in Table 2 below.

reduction temperature
(℃) M _s
(emu/g) M _r
(emu/g) H _c
(kOe) M _r /M _s (BH) _max
(MGOe) 800 81.34 59.39 10.23 0.73 8.30 815 88.63 64.42 10.59 0.73 9.77 850 89.49 68.72 10.93 0.77 11.05 900 93.57 76.07 12.64 0.81 13.80 950 96.79 80.84 14.65 0.84 14.76 1000 101.43 86.06 13.64 0.85 15.24

(M _s : saturation magnetization, M _r : residual magnetization, H _c : coercive force, M _r /M _s : alignment, (BH) _max : maximum magnetic energy product, external magnetic field size of up to 2.5T) As can be seen in FIG. 15 and <Table 2>, as the reduction temperature increases from 800° C. to 950° C., the saturation magnetization (M _s ), the residual magnetization (M _r ), the coercive force (H _c ), alignment of the magnetic particles It was confirmed that the degree (M _r /M _s ), and the maximum magnetic energy product ((BH) _{max ) all increased.} However, it was confirmed that the _{coercive force (H c} ) decreased as it increased from 950° C. to 1000° C. When the reduction temperature is 1000° C. or higher, overgrowth (coarseness) of the magnetic particles is expressed, so that deterioration of the magnetic particles may occur.

Therefore, it can be seen that when the magnetic particles according to the embodiment of the present invention are manufactured, the magnetic properties of the magnetic particles can be improved by controlling the reduction heat treatment temperature of the preliminary magnetic material to be greater than 900°C and less than 1000°C.

16 is an XRD graph illustrating a change in properties of magnetic particles according to a change in calcination temperature during a manufacturing process of magnetic particles according to an embodiment of the present invention.

Referring to FIG. 16 , after preparing the magnetic particles according to the embodiment in which the preliminary magnetic body calcined at different temperatures (AS, 200° C., 400° C., 700° C.) was reduced at 815° C., XRD (X- ray diffraction) results are shown.

As can be seen in FIG. 16, in the case of uncalcined magnetic particles (AS), magnetic particles calcined at a temperature of 200 °C, and magnetic particles calcined at a temperature of 400 °C, a peak indicating cobalt (Co) was found. However, it was confirmed that in the case of the magnetic particles calcined at a temperature of 700 ° C., a peak indicating cobalt (Co) was not found. Accordingly, at the calcination temperature of 200 °C and 400 °C, the thermal decomposition of calcium acetic acid monohydrate does not proceed sufficiently, so that the reaction between calcium monoxide (CaO) and oxide particles does not occur, whereas at the calcination temperature of 700 °C, calcium acetic acid monohydrate does not occur. It was found that the reaction between the thermally decomposed calcium monoxide (CaO) and oxide particles occurred.

17 is a VSM graph illustrating a change in characteristics of magnetic particles according to a change in a calcination temperature during a manufacturing process of magnetic particles according to an embodiment of the present invention.

Referring to FIG. 17 , after preparing the magnetic particles according to the embodiment in which the preliminary magnetic body calcined at different temperatures (AS, 200° C., 400° C., 700° C.) was reduced at 815° C., VSM (Vibrating Sample) for each Magnetometer) results are shown.

As can be seen in Figure 17, in the case of uncalcined magnetic particles (AS), magnetic particles calcined at a temperature of 200 °C, and magnetic particles calcined at a temperature of 400 °C, the increase in magnetization by the cobalt (Co) phase and the cobalt ( It was confirmed that the kink phenomenon occurred on Co). On the other hand, in the case of the magnetic particles calcined at a temperature of 700 °C, it was confirmed that the coercive force increased compared to the non-calcined magnetic particles (AS) and the magnetic particles calcined at the temperatures of 200 °C and 400 °C.

As a result, as can be seen through FIGS. 7 to 10 and 16 to 17 , in the process of manufacturing the magnetic particles according to an embodiment of the present invention, as the calcination temperature of the base powder is controlled to 700° C. or higher, calcium acetic acid It can be seen that a reaction between calcium monoxide (CaO), which is thermally decomposed of monohydrate, and oxide particles occurs, so that the magnetic particles can be easily formed.

18 is an image illustrating a change in the size of oxide particles according to a change in a source solution preparation process in a manufacturing process of magnetic particles according to an embodiment of the present invention.

Referring to (a) to (c) of FIG. 18 , SEM images of oxide particles formed under each condition are shown after preparing the source solution differently in the manufacturing process of the magnetic particles according to the embodiment. Specific process conditions are summarized in <Table 3> below. 18(a) shows condition 1, FIG. 18(b) shows condition 2, and FIG. 18(c) shows condition 3. In addition, in the case of FIGS. 18 (b) and 18 (c), diethylene glycol was used together with oleylamine as a dispersing agent.

Precursors Surfactants Solvents heat treatment condition Sm(acac) ₃ + Co(acac) ₃
(mmol) Oleylamine
(ml) Diethylene glycol
(ml) Methanol
(ml) temperature/time One 1.1250 20 - 40 215℃/1 hour 2 1.1250 28 2 40 3 0.5625 28 2 40

As can be seen from (a) to (c) of FIG. 18 and <Table 3>, when diethylene glycol is further used as a dispersant, it was confirmed that the size of the oxide particles decreased. In addition, as the total content of the first precursor (Sm(acac) ₃ ) and the second precursor (Co(acac) ₃ ) decreased, it was confirmed that the size of the oxide particles decreased.

As mentioned above, although the present invention has been described in detail using preferred embodiments, the scope of the present invention is not limited to specific embodiments and should be construed according to the appended claims. In addition, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

100: oxide particles
200: base particle
300: preliminary magnetic material
400: magnetic particles

Claims (14)

preparing a source solution in which a first precursor including a rare earth element, a second precursor including a metal element, and a dispersant are mixed;
hydrothermal synthesis of the source solution to form oxide particles including the rare earth element and the metal element;
preparing a base particle by coating the oxide particle with an additive containing calcium;
calcining the base particles to prepare a preliminary magnetic body in which calcium monoxide (CaO) in which the additive is thermally decomposed and the oxide particles are reacted; and
and reducing the preliminary magnetic material to prepare magnetic particles including a compound of the rare earth element and the metal element.
According to claim 1,
In the step of preparing the magnetic particles by reducing the preliminary magnetic body, the preliminary magnetic body is heat-treated and reduced,
The heat treatment temperature of the preliminary magnetic material is a method for producing magnetic particles, comprising more than 900 °C and less than 1000 °C.
According to claim 1,
In the step of preparing the magnetic preliminary body by calcining the base particles, the base particles are calcined in an air atmosphere,
The method for producing magnetic particles, wherein the magnetic particles include first magnetic particles of a hard magnetic phase and second magnetic particles of a soft magnetic phase.
According to claim 1,
In the step of preparing the magnetic preliminary body by calcining the base particles, the base particles are calcined in a hydrogen (H ₂ ) atmosphere,
The method for producing magnetic particles, wherein the magnetic particles include composite magnetic particles in which a hard magnetic phase and a soft magnetic phase are mixed.
According to claim 1,
In the step of producing the preliminary magnetic body by calcining the base particles,
The method for producing magnetic particles comprising a calcination temperature of the base particles is 700 ℃ or more.
According to claim 1,
When the content of the metal element compared to the rare earth element is controlled to be 7.3 at% to 8.5 at% in the step of preparing the source solution,
A method for producing magnetic particles, wherein the magnetic particles include a hard magnetic phase of _{Sm 2} Co _{17 .}
According to claim 1,
When the content of the metal element compared to the rare earth element is controlled to 4.5 at% to 5.0 at% in the step of preparing the source solution,
A method for producing magnetic particles, wherein the magnetic particles include a hard magnetic phase of _{SmCo 5 .}
According to claim 1,
The additive is, calcium acetate monohydrate (Calcium acetate monohydrate, Ca(C ₂ H ₃ O ₂ ) · H ₂ O) method for producing magnetic particles containing.
According to claim 1,
The rare earth element includes any one of samarium (Sm), neodymium (Nd), lanthanum (La), cerium (Ce), and praseodymium (Pr),
The metal elements are cobalt (Co), iron (Fe), copper (Cu), zirconium (Zr), chromium (Cr), tin (Sn), antimony (Sb), hafnium (Hf), manganese (Mn), A method for producing magnetic particles comprising any one of bismuth (Bi) and nickel (Ni).
According to claim 1,
After the step of producing the magnetic particles, the method for producing magnetic particles further comprising the step of removing the calcium monoxide (CaO) that the additive is thermally decomposed.
According to claim 1,
In the step of reducing the preliminary magnetic material to prepare the magnetic particles,
Wherein the preliminary magnetic body is heat-treated together with a reducing agent, and in a state in which the preliminary magnetic body is disposed on the reducing agent, the preliminary magnetic body is heat-treated.
a first magnetic particle including a samarium (Sm)-cobalt (Co) compound and having a hard magnetic phase; and
A magnetic particle comprising a second magnetic particle independent of the first magnetic particle, including cobalt (Co), and having a soft magnetic phase.
13. The method of claim 12,
The first magnetic particles may include any one of _{Sm 2} Co ₁₇ , Sm ₂ Co _17+x (x>0), or SmCo _{5 .}
Comprising a composite magnetic particle in which a hard magnetic phase containing a samarium (Sm)-cobalt (Co) compound and a soft magnetic phase containing a cobalt (Co) element are mixed,
The samarium (Sm)-cobalt (Co) compound is a magnetic particle comprising any one of _{Sm 2} Co ₁₇ , Sm ₂ Co _17+x (x>0), or SmCo _{5 .}

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