KR20210003656A - Fiber type magnetic structure and fabricating method of the same - Google Patents

Abstract

A method for manufacturing a fibrous magnetic structure having improved coercive force is provided. According to the present invention, the method for manufacturing a fibrous magnetic structure may comprise the steps of: preparing a magnetic core fiber containing a rare earth element and a core transition metal element; disposing catalyst particles on the magnetic core fiber; and as a plating process using a base source including a first precursor including a first shell transition metal element and a second precursor including a second shell transition metal element, forming a magnetic shell surrounding the magnetic core fiber using the catalyst particles and including a compound of the first shell transition metal element and the second shell transition metal element.

Description

Fiber type magnetic structure and fabricating method of the same}

The present invention relates to a fibrous magnetic structure and a method for manufacturing the same, and more specifically, to a fibrous magnetic structure including a magnetic core fiber containing a rare earth element and a magnetic shell containing a transition metal compound, and a method for manufacturing the same. will be.

Hard magnetic permanent magnets have been used indispensably for electric devices such as motors, speakers, and measuring instruments, as well as small motors in hybrid vehicles (HEVs) and electric vehicles (EVs). As such magnet materials, RE-Fe-B, RE-Fe-N, and RE-TM systems (RE = rare earth elements, TM = transition metal elements) with high coercivity are widely used, and these rare earth magnets are non-rare earth types. Compared with Mn-Al, Mn-Bi, and ferrite, it has a magnetic ability that is several tens of times more.

In line with the recent light weight, miniaturization, and high performance of electronic products, a permanent magnet material having a more improved maximum magnetic energy ((BH) _max ) is required. As a single-phase rare-earth material, development is limited due to its characteristic critical point, so'exchange spring magnet' supplementing this has been recently studied. Exchange spring magnet refers to a material that has a magnetic exchange coupling interaction by combining existing single-phase hard magnetic materials with soft magnetic materials, and is an important structure that can increase the characteristics of rare earth permanent magnets that have already reached the limits of research. The main issue of interchangeable spring magnets focuses on how to increase the magnetization value, coercivity, and magnetic energy by changing the shape or structure of hard magnetic soft magnetism.

In addition, various studies related to permanent magnets and materials thereof that can improve magnetic properties are being conducted. For example, in Korean Patent Publication No. 10-2017-0108468 (Application No.: 10-2016-0032417, Applicant: Yonsei University Industry-Academic Cooperation Foundation), a substrate, and a laminate formed on the substrate, comprising a Bi thin film layer and a Mn thin film layer Disclosed is a non-rare earth permanent magnet with improved coercivity and a method for manufacturing the same, including a thin film laminate obtained by repeatedly stacking and heat treating the unit at least two times or more. In addition, various studies related to permanent magnets and materials that can improve magnetic properties are continuously being conducted.

Korean Patent Publication No. 10-2017-0108468

One technical problem to be solved by the present invention is to provide a fibrous magnetic structure with improved coercivity and a method of manufacturing the same.

Another technical problem to be solved by the present invention is to provide a fibrous magnetic structure with improved maximum magnetic energy and a method for manufacturing the same.

Another technical problem to be solved by the present invention is to provide a fibrous magnetic structure with reduced self-aggregation and a method of manufacturing the same.

Another technical problem to be solved by the present invention is to provide a one-dimensional fibrous magnetic structure and a method of manufacturing the same.

Another technical problem to be solved by the present invention is to provide a fibrous magnetic structure and a method of manufacturing the same, in which an exchange magnetic coupling effect between a hard magnetic structure and a soft magnetic structure is expressed.

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

In order to solve the above technical problems, the present invention provides a method of manufacturing a fibrous magnetic structure.

According to an embodiment, the method of manufacturing the fibrous magnetic structure includes preparing a magnetic core fiber including a rare earth element and a core transition metal element, and placing catalyst particles on the magnetic core fiber. And a plating process using a base source including a first precursor including a first shell transition metal element and a second precursor including a second shell transition metal element, using the catalyst particles, and the core fiber And forming a magnetic shell including a compound of the first shell transition metal element and the second shell transition metal element surrounding the element.

According to an embodiment, the base source may be provided for less than 20 minutes, and the magnetic shell may have a thickness of 40 nm or less.

According to an embodiment, a temperature of the base source may be controlled to be greater than 70°C and less than 90°C.

According to an embodiment, the base source may further include a pH adjusting agent, and the pH of the base source may be controlled to be greater than 8 and less than 12.

According to an embodiment, the preparing of the magnetic core fiber includes preparing a source solution including the rare earth element and the core transition metal element, electrospinning the source solution, and preparing a preliminary magnetic core fiber, It may include heat-treating the preliminary magnetic core fiber to oxidize it, and reducing the oxidized preliminary magnetic core fiber by heat treatment using a reducing agent.

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

According to an embodiment, the fibrous magnetic structure includes a magnetic core fiber including a rare earth element and a core transition metal element, and surrounding the magnetic core fiber, and the first shell transition metal element and the second shell Including a magnetic shell containing a transition metal element (exchange-coupling effect) between the magnetic core fiber and the magnetic shell, the dipole interaction of the magnetic core fiber and the magnetic shell ( dipolar interaction).

According to an embodiment, the fibrous magnetic structure may include one (one) peak in a graph representing the value of <Equation 1> below with respect to the applied field value (Oe). have.

<Equation 1>

dM/dH

(M: Magnetic moments, H: External magnetic field applied)

According to an embodiment, the magnetic core fiber may include a plurality of single crystals connected in series in the longitudinal direction of the magnetic core fiber.

According to an embodiment, the diameter of the magnetic core fiber may include a diameter smaller than the size of a single-domain of the magnetic core fiber.

According to an embodiment, the thickness of the magnetic shell may include less than two times the domain-wall width of the magnetic core fiber.

According to an embodiment, the magnetic shell may include a magnetic shell that is conformally disposed on the magnetic core fiber.

According to an embodiment, the rare earth element may include any one of La, Ce, Pr, Nd, Sm, or Gd.

According to an embodiment, the core transition metal element, the first shell transition metal element, and the second shell transition metal element may include any one of Fe, Co, and Ni.

According to an embodiment, the core transition metal element may include any one of the first shell transition metal element or the second shell transition metal element.

The fibrous magnetic structure according to an embodiment of the present invention may have a one-dimensional shape composed of a magnetic core fiber and a magnetic shell surrounding the magnetic core fiber. Accordingly, self-aggregation due to attractive force is prevented, shape anisotropy constant is increased, and an exchange-coupling effect between the magnetic core fiber and the magnetic shell is caused by the magnetic core fiber and the magnetic shell. A magnetic structure with improved magnetic properties such as coercivity and maximum magnetic energy may be provided, which is greater than that of the dipolar interaction of the shell.

1 is a flow chart illustrating a method of manufacturing a fibrous magnetic structure according to an embodiment of the present invention.
2 is a flowchart specifically illustrating a step of preparing a magnetic core fiber in a method of manufacturing a fibrous magnetic structure according to an embodiment of the present invention.
3 is a view showing a manufacturing process of the fibrous magnetic structure according to an embodiment of the present invention.
4 is a view showing a fibrous magnetic structure according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating an area A in the TT' cross-section of FIG.
6 is a view showing a cross section of a fibrous magnetic structure according to another embodiment of the present invention.
7 is a photograph of a magnetic core fiber according to an embodiment of the present invention.
8 is a graph showing the characteristics of a magnetic core fiber according to an embodiment of the present invention.
9 is a photograph comparing a spherical magnetic structure according to a comparative example of the present invention and a fibrous magnetic structure according to the embodiment.
10 and 11 are graphs showing coercivity and maximum magnetic energy of magnetic structures according to Comparative Examples and Examples of the present invention.
12 and 13 are graphs comparing various magnetic properties of magnetic structures according to Comparative Examples and Examples of the present invention.
14 and 15 are photographs of a magnetic core fiber and a fibrous magnetic structure according to an embodiment of the present invention.
16 is a picture taken in more detail of the fibrous magnetic structure according to Example 1 of the present invention.
17 is a picture taken in more detail of the fibrous magnetic structure according to the fourth embodiment of the present invention.
18 is a graph showing an XRD pattern of a magnetic core fiber and a fibrous magnetic structure according to an embodiment of the present invention.
19 is a graph showing the MH curve of the magnetic core fiber and the fibrous magnetic structure according to an embodiment of the present invention.
20 is a graph showing the effect of the concentration of FeSO ₄ during the manufacturing process of the fibrous magnetic structure according to an embodiment of the present invention.
21 is a photograph of a fibrous magnetic structure according to Examples 6 and 7 of the present invention.
22 is a photograph of a fibrous magnetic structure according to Examples 5 and 8 of the present invention.
23 is a graph showing the crystallinity of the fibrous magnetic structure according to Examples 5 to 8 of the present invention.
24 is a graph showing magnetic properties of fibrous magnetic structures according to Examples 5 to 8 of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical idea 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 the present specification, when a component is referred to as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. 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, and third 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 component. 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 its complementary embodiment. 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, expressions in the singular include plural expressions unless the context clearly indicates otherwise. In addition, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, elements, or a combination of the features described in the specification, and one or more other features, numbers, steps, and configurations It is not to be understood as excluding the possibility of the presence or addition of elements or combinations thereof. In addition, in the present specification, "connection" is used to include both indirectly connecting a plurality of constituent elements and direct connecting.

Further, in the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

1 is a flowchart illustrating a method of manufacturing a fibrous magnetic structure according to an embodiment of the present invention, and FIG. 2 is a detailed description of a step of preparing a magnetic core fiber in a method of manufacturing a fibrous magnetic structure according to an embodiment of the present invention. 3 is a view showing a manufacturing process of a fibrous magnetic structure according to an embodiment of the present invention, FIG. 4 is a view showing a fibrous magnetic structure according to an embodiment of the present invention, and FIG. 5 is It is a view showing a region A of the TT' cross-section, and FIG. 6 is a view showing a cross section of a fibrous magnetic structure according to another embodiment of the present invention.

1 to 5, a magnetic core fiber 110 is prepared (S100). According to an embodiment, the magnetic core fiber 110 preparation step includes a source solution preparation step (S110), a preliminary magnetic core fiber manufacturing step (S120), a preliminary magnetic core fiber oxidation step (S130), and an oxidized premagnetic It may include a core fiber reduction step (S140). Hereinafter, each step will be described in detail.

In step S110, a source solution is prepared. According to an embodiment, the source solution may contain a rare earth element and a core transition metal element. According to an embodiment, the rare earth element may include at least one of La, Ce, Pr, Nd, and Sm. For example, the rare earth element may include nitrate, specifically, La(NO ₃ ) ₃ ·6H ₂ O, La(NO ₃ ) ₃ ·χH ₂ O, Ce(NO ₃ ) ₃ ·6H ₂ O , Ce(NO ₃ ) ₅ (H ₃ O) ₂ ·H ₂ O, Pr(NO ₃ ) ₃ ·6H ₂ O, Nd(NO ₃ ) ₃ ·6H ₂ O, Nd(NO ₃ ) ₃ ·χH ₂ O , Sm(NO ₃ ) ₃ · 6H ₂ O may be any one of. According to an embodiment, the core transition metal element may include at least one of Fe, Ni, and Co. For example, the core transition metal element may include nitrate, specifically, Fe(NO ₃ ) ₃ ·9H ₂ O, Co(NO ₃ ) ₂ ·6H ₂ O, Ni(NO ₃ ) ₂ ·6H _It may be any one of ₂ O.

The source solution may further include a polymer material, an additive, and a solvent. According to an embodiment, the polymer material is at least one of PVP (Polyvinylpyrrolidone), PAN (Polyacrylonitrile), PVAc (Poly (vinyl acetate)), PVB (Polyvinylbutyral), PVA (Poly (vinyl alcohol)) or PEO (Polyethylene oxide). It can contain either. According to an embodiment, the additive may be citric acid (C ₆ H ₈ O ₇ ). According to an embodiment, the solvent may be a mixed solution of distilled water and ethanol.

For example, the source solution is a mixture of Sm(NO ₃ ) ₃ 6H ₂ O, Co(NO ₃ ) ₂ 6H ₂ O, 0.3 wt% of PVP (polyvinylpyrrolidone), 1.0 M of Citric acid anhydrous in DI water, It can be prepared by stirring for 6 hours.

In the step S120, the source solution is electrospun to prepare a preliminary magnetic core fiber. According to an embodiment, the source solution may be injected into a syringe, and the nanofibers may be spun using a syringe pump. The syringe tip and a collector in which the spun nanofibers are collected are spaced apart from 10 to 20 cm, and the syringe pump may spun the nanofibers at a rate of 0 to 0.5 mL/h. For example, a voltage of 20 kV is applied to the syringe pump to spun the nanofibers at a rate of 0.3 mL/h, but the distance between the syringe tip and the collector may be 15 cm.

According to an embodiment, the diameter of the preliminary magnetic core fiber may be controlled by adjusting the viscosity of the source solution. The viscosity of the source solution may be adjusted according to the relative amount of the polymer material relative to the rare earth element and the core transition metal element. Specifically, when the amount of the polymer material increases relative to the rare earth element and the core transition metal element, the viscosity increases, and thus the diameter of the preliminary magnetic core fiber may increase. Alternatively, when the amount of the polymer material is decreased compared to the rare earth element and the core transition metal element, the viscosity is decreased, so that the diameter of the preliminary magnetic core fiber may be decreased.

In the step S130, the preliminary magnetic core fiber may be oxidized. According to an embodiment, the preliminary magnetic core fiber may be oxidized by heat treatment. For example, the preliminary magnetic core fiber may be heat-treated at a temperature of 700° C. in air.

In the step S140, the oxidized preliminary magnetic core fiber may be reduced. According to an embodiment, the preliminary magnetic core fiber may be reduced by heat treatment after being mixed with a reducing agent. For example, the reducing agent may include either calcium (Ca) or calcium hydride (CaH ₂ ). For example, the preliminary magnetic core fiber may be heat-treated at a temperature of 700° C. for 3 hours. Finally, the reduced preliminary magnetic core fiber is rinsed, so that the magnetic core fiber 110 according to the embodiment may be manufactured. According to an embodiment, the magnetic core fiber 110 may have hard magnetism.

As a result, the magnetic core fiber 110 according to the embodiment may include a compound of the rare earth element and the core transition metal element. For example, the magnetic core fiber 110 may have a compound structure of at least one of Sm ₂ Co ₇ , Sm ₂ Co ₁₇ , SmCo ₇ , SmCo ₃ , SmCo ₅ , or SmCo ₁₂ . In contrast, for another example, the magnetic core fiber 110 is Sm _x (Co, N) _y (C, B, Zr, Cu, Hf, Nb, Ti, M) _z (x,y>0 / N : Any one of the transition metal elements excluding cobalt, M: one of the elements in the given chemical formula and one of the elements on the periodic table excluding N). Alternatively, for another example, the magnetic core fiber 110 may have a compound structure such as an Nd-Fe-B-based alloy or an Sm-Fe-N-based alloy. In addition, the magnetic core fiber 110 may include various compound structures having hard magnetism. The compound structure of the magnetic core fiber 110 is not limited.

According to an embodiment, the magnetic core fiber 110 may have a structure in which a plurality of single crystals 110sc are connected in series in the longitudinal direction of the magnetic core fiber 110 as shown in FIG. 5. Alternatively, according to another embodiment, the magnetic core fiber 110 may have a polycrystalline structure as shown in FIG. 6.

Catalyst particles may be disposed on the magnetic core fiber 110 (S200). According to an embodiment, the catalyst particles may be formed by reacting a first metal catalyst and a second metal catalyst. According to an embodiment, the first metal catalyst may include tin (Sn). For example, the first metal catalyst may be SnCl ₂ . Alternatively, the second metal catalyst may include palladium (Pd). For example, the second metal catalyst may be PdCl ₂ . Accordingly, the catalyst particles may include Pd-Sn. More specifically, the magnetic core fiber 110 is immersed in a solution of SnCl ₂ 2H ₂ O and HCl (35-37%) for 5 minutes, and then in a solution of PdCl ₂ and HCl for at least 2 minutes. By being immersed, the catalyst particles (Pd-Sn) may be formed on the magnetic core fiber 110.

A base source may be provided to the magnetic core fiber 110 on which the catalyst particles are disposed, so that a magnetic shell 120 may be formed (S300). According to an embodiment, the base source may be provided by an electroless plating process. Accordingly, a fibrous magnetic structure 100 including the magnetic core fiber 110 and the magnetic shell 120 may be manufactured.

The base source may include a first precursor and a second precursor. According to an embodiment, the first precursor may include a first shell transition metal element. For example, the first shell transition metal element may include any one of Fe, Co, or Ni. For example, the first precursor may include FeSO ₄ . Alternatively, the second precursor may include a second shell transition metal element. For example, the second shell transition metal element may include any one of Fe, Co, or Ni. For example, the second precursor may include CoSO ₃ . That is, the first shell transition metal element may be different from the second shell transition metal element. On the other hand, the core transition metal element may be the same as the second shell transition metal element.

The base source may further include a complexing agent, a reducing agent, a pH adjusting agent, and a buffer. For example, the complexing agent may be Na ₃ C ₆ H ₅ O ₇ 2H ₂ O. The reducing agent may be NaH ₂ PO ₂ H ₂ O. The pH adjusting agent may be NaOH. The buffer may be (NH ₄ ) ₂ SO ₄ .

For a more specific example, the base source is 0.2M concentration of FeSO ₄ 7H ₂ O, 0.09M concentration of CoSO ₃ 7H ₂ O, 0.3M concentration of Na ₃ C ₆ H ₅ O ₇ 2H ₂ O, 0.25M concentration NaH ₂ PO ₂ H ₂ O, 0.1M concentration of (NH ₄ ) ₂ SO ₄ , and NaOH can be prepared by mixing.

As described above, the base source may be provided to the magnetic core fiber 110 by an electroless plating method. According to an embodiment, the magnetic core 110 may be immersed in the base source. In this case, by the catalyst particles, the first shell transition metal element and the second shell transition metal element may react. Accordingly, the magnetic shell 120 surrounding the magnetic core fiber 110 may be formed. According to an embodiment, the magnetic shell 120 may have soft magnetism. For example, the magnetic shell 120 may include an Fe ₁₁ Co ₅ compound structure. In addition, the magnetic shell 120 may include various compound structures having soft magnetic properties. The compound structure of the magnetic shell 120 is not limited.

According to an embodiment, the plating time of the base source may be controlled. For example, the base source may be provided for less than 20 minutes. Accordingly, the magnetic shell 120 may conformally cover the magnetic core fiber 110. For this reason, the fibrous magnetic structure 100 according to the embodiment has an exchange-coupling effect between the magnetic core fiber 110 and the magnetic shell 120, and the magnetic core fiber ( 110) and the magnetic shell 120 may be larger than the dipolar interaction.

In contrast, when the base source is provided for a time period of more than 20 minutes (when electroless plating is performed for a time period of more than 20 minutes), the compound of the first shell transition metal element and the second shell transition metal element , It can be formed in the form of independent crystalline particles as well as the plating layer. In this case, the dipolar interaction between the magnetic core fiber 110 and the crystalline particles is more than an exchange-coupling effect between the magnetic core fiber 110 and the crystalline particles. It can appear large.

Magnetic properties such as coercive force and maximum magnetic energy (BH _max ) when an exchange magnetic coupling effect occurs between the hard magnetic structure and the soft magnetic structure in a structure in which a hard magnetic structure and a soft magnetic structure are mixed This can be improved. However, when the dipolar interaction of each of the hard magnetic structure and the soft magnetic structure occurs predominantly, the magnetic properties may be reduced because the exchange magnetic coupling effect between the hard magnetic structure and the soft magnetic structure is reduced.

The exchange magnetic coupling effect between the hard magnetic structure and the soft magnetic structure and the size of the dipole mutual field of the hard magnetic structure and the soft magnetic structure are a graph showing the value of <Equation 1> below with respect to the applied field value (Oe) It can be determined by the number of peaks represented by.

<Equation 1>

dM/dH

(M: Magnetic moments, H: External magnetic field applied)

For example, when the exchange magnetic coupling effect between the hard magnetic structure and the soft magnetic structure is larger than the dipole interaction of the hard magnetic structure and the soft magnetic structure, one peak may appear in the above-described graph. In contrast, when the dipole interaction of the hard magnetic structure and the soft magnetic structure is greater than the exchange magnetic coupling effect between the hard magnetic structure and the soft magnetic structure, two peaks may appear in the above-described graph.

As a result, the method of manufacturing a fibrous magnetic structure according to the embodiment, by controlling the plating time of the base source to less than 20 minutes, exchange magnetic coupling between the magnetic core fiber 110 and the magnetic shell 120 By making the exchange-coupling effect appear larger than the dipolar interaction of the magnetic core fiber 110 and the magnetic shell 120, coercive force and maximum magnetic energy (BH _max ) Magnetic properties such as can be improved.

In addition, the diameter (D _c ) of the magnetic core fiber 110 is smaller than the terminal size (single-domain, D _s ) of the magnetic core fiber 110, and the thickness (T _K ) of the magnetic shell 120 May be less than twice the domain-wall width of the magnetic core fiber 110. In this case, the exchange-coupling effect between the magnetic core fiber 110 and the magnetic shell 120 is a dipole interaction between the magnetic core fiber 110 and the magnetic shell 120 ( dipolar interaction). The width of the terminal sphere wall may be defined as a distance between facing sidewalls of the single crystals 110sc adjacent to each other.

According to an embodiment, the thickness T _K of the magnetic shell 120 may be controlled according to the plating time of the base source. For example, when the plating time of the base source is controlled to 5 minutes, the thickness T _K of the magnetic shell 120 may be controlled to 10 nm to 15 nm. In contrast, when the plating time of the base source is controlled to be 10 minutes, the thickness T _K of the magnetic shell 120 may be controlled to be 15 nm to 25 nm. In contrast, when the plating time of the base source is controlled to 15 minutes, the thickness T _K of the magnetic shell 120 may be controlled to 25 nm to 35 nm. In contrast, when the plating time of the base source is controlled to be 20 minutes, the thickness T _K of the magnetic shell 120 may be controlled to be greater than 40 nm.

As described above, in the fibrous magnetic structure 100 according to the embodiment, an exchange-coupling effect between the magnetic core fiber 110 and the magnetic shell 120 is the magnetic core fiber. As the plating time of the base source is controlled to be less than 20 minutes to be greater than the dipolar interaction of (110) and the magnetic shell 120, the thickness of the magnetic shell 120 is controlled to be 40 nm or less. I can.

According to an embodiment, in order to improve the magnetic properties of the fibrous magnetic structure 100, the pH and temperature of the base source may be controlled. Specifically, the pH of the base source plated on the magnetic core fiber 110 may be controlled to be greater than 8 and less than 12. In addition, the temperature of the base source plated on the magnetic core fiber 110 may be controlled to be greater than 70°C and less than 90°C.

In contrast, when the pH of the base source is 8 or less, there may be a problem that a plating layer is not formed on the magnetic core fiber 110. On the other hand, when the pH of the base source is 12 or higher, the compound of the first shell transition metal element and the second shell transition metal element may be formed in the form of independent crystalline particles as well as a plating layer.

The conventional non-rare earth based spring magnet is difficult to replace the high energy density rare earth magnet that is most widely used in the actual industry. In addition, spring magnets manufactured by simple mixing such as ball milling are more efficient than spring magnets having a stacked structure or core-shell structure because the interaction between the two hard magnetic soft magnetics is very limited. There is a problem that it is difficult to expect a self-exchange coupling effect.

In addition, the conventional technique of plating a soft magnetic material on a hard magnetic material to have a core-shell structure, as the core structure has a 0-dimensional (eg, spherical particle) structure, self-aggregation by magnetic attraction in the manufacturing process (self -aggregation) may occur. Accordingly, there is a problem in that uneven plating results and magnetic properties are deteriorated. In order to manufacture the core-shell structure by a method other than the plating process, a sol-gel process is used, but there is a problem in that it is extremely difficult to establish a self-exchange bond because the structure size control is very difficult. In addition, the two-dimensional composite magnet structure (eg, film) has a problem that practical application is difficult because it is not suitable for mass production.

However, the fibrous magnetic structure 100 according to the embodiment of the present invention has a one-dimensional shape composed of the magnetic core fiber 110 and the magnetic shell 120 surrounding the magnetic core fiber 110. I can. Accordingly, self-aggregation due to attraction is prevented, shape anisotropy constant is increased, and the exchange-coupling effect between the magnetic core fiber 110 and the magnetic shell 120 is increased. A magnetic structure with improved magnetic properties such as coercivity and maximum magnetic energy may be provided, which is greater than the dipolar interaction of the magnetic core fiber and the magnetic shell.

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

Magnetic core fiber manufacturing according to the embodiment

Mix Sm(NO ₃ ) ₃ 6H ₂ O, Co(NO ₃ ) ₂ 6H ₂ O, 0.3 wt% of PVP (polyvinylpyrrolidone) and 1.0 M of Citric acid anhydrous in Di water, and stir for 6 hours to prepare the source solution. Was prepared. The prepared source solution was injected into a 12 mL 30-gauge syringe, a voltage of 20 kV was applied to the syringe pump, and spun at a rate of 0.3 mL/h to prepare a preliminary magnetic core fiber.

Thereafter, the preliminary magnetic core fiber was heat-treated at a temperature of 700° C. in the air to oxidize the pre-magnetic core fiber, mixed with CaH _2, and then heat-treated at a temperature of 700° C. for 3 hours to reduce. Finally, the reduced preliminary magnetic core fiber was rinsed with a 0.1 M concentration of NH ₄ Cl/methanol solution to prepare a magnetic core fiber according to an embodiment having a structure of Sm ₂ Co ₁₇ .

Fabrication of the fibrous magnetic structure according to the embodiment

The magnetic core fiber according to the above-described embodiment was immersed in a solution of SnCl ₂ 2H ₂ O and HCl (35-37%) for 5 minutes for sensitization, and then in a solution of PdCl ₂ and HCl for at least 2 minutes. After immersion, the magnetic core fiber was activated by rinsing with DI water.

0.2M concentration of FeSO ₄ 7H ₂ O, 0.09M concentration of CoSO ₃ 7H ₂ O, 0.3M concentration of Na ₃ C ₆ H ₅ O ₇ 2H ₂ O, 0.25M concentration of NaH ₂ PO ₂ H ₂ O, 0.1M A base source in which the concentration of (NH ₄ ) ₂ SO ₄ , and NaOH is mixed is prepared.

By immersing the activated magnetic core fiber in the prepared base source, it is an electroless plating process. The magnetic core fiber is coated with a magnetic shell containing FeCo, followed by rinsing with a solution of DI water and methanol. Thus, a fibrous magnetic structure according to the embodiment was manufactured.

In addition, in the manufacturing process of the fibrous magnetic structure described above, a plurality of fibrous magnetic structures according to different embodiments were manufactured by varying the electroless plating time, the electroless plating temperature, and the pH of the base source. Specific conditions of the manufactured fibrous magnetic structure are summarized through <Table 1> below.

division Plating time (min) Plating temperature Base source pH Example 1 5 70℃ 9 Example 2 10 70℃ 9 Example 3 15 70℃ 9 Example 4 20 70℃ 9 Example 5 15 50℃ 9 Example 6 15 70℃ 9 Example 7 15 80℃ 9 Example 8 15 90℃ 9

Preparation of magnetic core particles according to comparative examples

Using a source solution containing Sm(NO ₃ )6H ₂ O and Co(NO ₃ ) ₂ 6H ₂ O, magnetic core particles according to the comparative example of the Sm2Co17 structure were prepared.

Manufacture of spherical magnetic structure according to comparative example

By performing the method of manufacturing a fibrous magnetic structure according to the above-described embodiment on the magnetic core particles according to the comparative example described above, a magnetic shell having a Fe ₁₁ Co ₅ structure is coated on the Sm ₂ Co ₁₇ magnetic core particles. A spherical magnetic nanostructure was manufactured according to the comparative example.

7 is a photograph of a magnetic core fiber according to an embodiment of the present invention, and FIG. 8 is a graph showing characteristics of a magnetic core fiber according to an embodiment of the present invention.

Referring to FIG. 7, a magnetic core fiber according to the above embodiment was photographed by SEM (Scanning Electron Microscopy). As can be seen through FIG. 7, it was confirmed that the magnetic core fiber according to the embodiment has a fiber shape.

Referring to (a) of FIG. 8, a histogram of measuring Relative Intensity (au) according to the diameter (nm) of the magnetic core fiber according to the embodiment is shown, and referring to (b) of FIG. It shows an XRD (X-ray diffraction) pattern measuring the Relative Intensity (au) according to 2 theta (deg.) of the magnetic core fiber according to the example.

As can be seen in (a) of Figure 8, it was confirmed that the magnetic core fiber according to the embodiment has an average diameter size of 185 ± 31 nm, and as can be seen in (b) of Figure 8, in the above embodiment Accordingly, it was confirmed that the magnetic core fiber had an Sm ₂ Co ₁₇ structure.

9 is a photograph comparing a spherical magnetic structure according to a comparative example of the present invention and a fibrous magnetic structure according to the embodiment.

Referring to (a) of FIG. 9, the spherical magnetic structure according to the comparative example was photographed by SEM, and referring to (b) of FIG. 9, the fibrous magnetic structure according to the embodiment was photographed by SEM. . As can be seen in (a) and (b) of FIG. 9, it was confirmed that the magnetic structure according to the comparative example had a sphere shape, while the magnetic structure according to the example had a fiber shape.

10 and 11 are graphs showing coercivity and maximum magnetic energy of magnetic structures according to Comparative Examples and Examples of the present invention.

Referring to FIG. 10, the coercivity and maximum magnetic energy ((BH) _max ) of the magnetic structure according to the comparative examples and examples of the present invention were measured and shown. Referring to FIG. 11, a comparative example of the present invention According to the magnetic core particles (Sm ₂ Co ₁₇ , 0-D), the spherical magnetic structure according to the comparative example (Sm ₂ Co ₁₇ , 0-D), the magnetic core fiber according to the embodiment (Sm ₂ Co ₁₇ , 1-D ), the magnetization values (Magnetization, emu/g) of the fibrous magnetic structure (Sm ₂ Co ₁₇ , 0-D) according to the embodiment were measured, respectively, and an MH curve was shown.

As can be seen in FIG. 10, it was confirmed that the fibrous magnetic structure according to the embodiment had higher coercivity and maximum magnetic energy than the spherical magnetic structure according to the comparative example. In addition, as can be seen in FIG. 11, it was confirmed that the graph area of the fibrous magnetic structure according to the embodiment was larger than the magnetic core fiber according to the embodiment. Accordingly, it was found that the fibrous magnetic structure has improved coercivity and maximum magnetic energy compared to the spherical magnetic structure, and that the magnetic properties of the fibrous magnetic structure are higher than that of the magnetic core fiber.

12 and 13 are graphs comparing various magnetic properties of magnetic structures according to Comparative Examples and Examples of the present invention.

12A to 12C, maximum magnetization (M _25kOe , M _25kOe , for the spherical magnetic structure 0-D) according to the comparative example and the fibrous magnetic structure 1-D according to the embodiment. emu/g), squareness(M _r / M _25kOe , %), and maximum energy product ((BH) _max , MGOe) are measured, respectively, in Figs. 12(a), 12(b), and 12(c). ), and referring to (a) and (b) of FIG. 13, remanence of the spherical magnetic structure (0-D) according to the comparative example and the fibrous magnetic structure (1-D) according to the embodiment (Mr, emu/g) and intrinsic coercivity (H _ci , kOe) were measured and shown in FIGS. 13(a) and 13(b), respectively.

As can be seen in FIGS. 12 and 13, the fibrous magnetic structure (1-D) according to the embodiment has a maximum magnetization (M _25kOe , emu/g) than the spherical magnetic structure (0-D) according to the comparative example, Squareness (M _r / M _25kOe , %), remanence (Mr, emu/g), intrinsic coercivity (H _ci , kOe), and maximum energy roduct ((BH) _max , MGOe) were all high.

In particular, as can be seen in (c) of Figure 12, the fibrous magnetic structure according to the embodiment, as the base source plating time (plating time, min) increases in the manufacturing process of the fibrous magnetic structure, the maximum It was confirmed that the magnetic energy ((BH) _max ) was improved up to 36.4%.

14 and 15 are photographs of a magnetic core fiber and a fibrous magnetic structure according to an embodiment of the present invention.

14A to 14C, the fibrous magnetic structures according to Examples 1 to 3 were photographed by SEM, and referring to FIGS. 15A and 15B, the The magnetic core fiber according to the Example and the fibrous magnetic structure according to Example 4 were shown by SEM photographing.

As can be seen from (a) to (c) of Figure 14, it was confirmed that the FeCo layer was formed on the surface of the magnetic core fiber (Sm ₂ Co ₁₇ ). However, as can be seen in (b) of Figure 15, when plated for a time of 20 minutes, it was confirmed that FeCo is formed in the form of independent crystalline particles.

16 is a picture taken in more detail of the fibrous magnetic structure according to the first embodiment of the present invention, and FIG. 17 is a picture taken in more detail of the fibrous magnetic structure according to the fourth embodiment of the present invention.

Referring to FIG. 16A, the fibrous magnetic structure according to Example 1 was photographed by TEM (Transmission Electron Microscopy). Referring to FIG. 16B, the cross of FIG. 16A -sectional EDS line scan profile is shown.

As can be seen in (a) and (b) of FIG. 16, the FeCo layer was formed to a thickness of 10 nm to 15 nm on the magnetic core fiber, and it was confirmed that the magnetic core fiber and the FeCo layer are clearly distinguished.

Referring to FIG. 17(a), the fibrous magnetic structure according to the fourth embodiment was photographed by TEM (Transmission Electron Microscopy). Referring to FIG. 17(b), the cross of FIG. 17(a) -sectional EDS line scan profile is shown.

As can be seen in (a) and (b) of Fig. 17, the FeCo layer was formed to a thickness of 40 nm on the magnetic core fiber, has an independent crystalline particle shape, and the boundary between the magnetic core fiber and the FeCo layer is ambiguous. I could see that it appeared.

18 is a graph showing an XRD pattern of a magnetic core fiber and a fibrous magnetic structure according to an embodiment of the present invention.

18, 2 theta for each of the magnetic core fiber (0 min) according to the embodiment and the fibrous magnetic structure (5 min, 10 min, 15 min, 20 min) according to Examples 1 to 4 Relative intensity (au) according to (deg.) was measured to show the XRD pattern.

As can be seen in FIG. 18, it was confirmed that a clear hexagonal Sm ₂ Co ₁₇ pattern appeared in all of the fibrous magnetic structures according to Examples 1 to 4. Accordingly, it can be seen that in the process of electroless plating the magnetic core fiber with the base source, conditions such as pH and temperature of the base source do not damage the magnetic core fiber. In addition, in the case of the fibrous magnetic structure according to Example 3, a small FeCo peak appears, whereas in the case of the fibrous magnetic structure according to Example 4, a relatively large FeCo peak appears, and the X-ray diffraction pattern of crystalline Fe-Co I was able to confirm that appeared.

19 is a graph showing an M-H curve of a magnetic core fiber and a fibrous magnetic structure according to an embodiment of the present invention.

19, a magnetic core fiber (plated for 0 min) according to the embodiment, a fibrous magnetic structure (plated for 5 min) according to Example 1, and a fibrous magnetic structure (plated for 10) according to Example 2 min), for each of the fibrous magnetic structure (plated for 15 min) according to Example 3, and the fibrous magnetic structure (plated for 20 min) according to Example 4, Magnetization (emu/g) according to Applied Field (Oe) ) And dM/dH;χ _rev (au) were measured and shown. (M: Magnetic moments, H: External magnetic field applied)

As can be seen in FIG. 19, it was confirmed that the curve area of the fibrous magnetic structure according to Example 4 was significantly lower than the curve area of the fibrous magnetic structure according to Examples 1 to 3. In addition, in the dM/dH curve, it was confirmed that the fibrous magnetic structure according to Examples 1 to 3 showed one peak, but the fibrous magnetic structure according to Example 4 showed two peaks. That is, Embodiment 4 fiber-like magnetic structure according to the magnetic core fiber (Sm ₂ Co ₁₇₎ and dipole interactions of the magnetic shells (FeCO) (dipolar interaction) a magnetic core fiber (Sm ₂ Co ₁₇₎ and a magnetic shell (FeCO ), it can be seen that the magnetic properties are weakened as the result is greater than the exchange magnetic coupling effect between ).

In addition, the magnetic properties of the magnetic core fiber and the fibrous magnetic structure according to the above embodiment are summarized in Table 2 below.

division Magnetic core fiber according to the embodiment Fibrous magnetic structure according to Example 1 Fibrous magnetic structure according to Example 2 Fibrous magnetic structure according to Example 3 Fibrous magnetic structure according to Example 4 Electroless plating time (min) 0 5 10 15 20 Plating layer thickness (nm) - 10-15 15-25 25~35 >40 Saturation magnetization (emu/g) 80.995 98.956 99.357 103.290 108.470 Residual magnetization (emu/g) 55.809 67.974 68.163 69.750 65.862 Coercivity (Oe) 6943.8 6873.7 6582.7 6528.3 5571.0 Square ratio (%) 68.904 68.691 68.604 67.528 60.719 (BH) _max (MGOe) 7.43 10.14 9.34 9.70 5.85

As can be seen in FIGS. 18 and 19, <Table 4>, the exchange magnetic coupling effect between the magnetic core fiber and the magnetic shell is greater than the dipole interaction of the magnetic core fiber and the magnetic shell, so that the coercive force and the maximum magnetic energy ( In order to improve magnetic properties such as BH _max ), it was found that it was an effective method to control the plating time of the base source to less than 20 minutes.

20 is a graph showing the effect of the concentration of FeSO ₄ during the manufacturing process of the fibrous magnetic structure according to an embodiment of the present invention.

Referring to FIG. 20, in the process of preparing the base source, the concentration of FeSO ₄ was controlled, and the atomic% of the Fe element and the Co element contained in the fibrous magnetic structure according to Example 1 prepared according to the controlled concentration was measured. Shown.

As can be seen in Figure 20, when the concentration of FeSO ₄ is controlled to 0.2M, it was confirmed that the fibrous magnetic structure according to Example 1 has a structure of Fe ₆₅ Co ₃₅ . Since the structure of Fe ₆₅ Co ₃₅ has the highest saturation magnetization value among the soft magnetic phases, in order to improve the magnetic properties of the fibrous magnetic structure according to the above embodiment, it is an effective method to control the concentration of FeSO ₄ to 0.2M. Could know.

In addition, an experiment was performed to confirm the influence on the pH of the base source during the manufacturing process of the fibrous magnetic structure according to an embodiment of the present invention. Specifically, a fibrous magnetic structure according to Example 1 manufactured through a base source having a pH of 1 to 8, a fibrous magnetic structure according to Example 1 manufactured through a base source having a pH of 9 to 11, and Each of the fibrous magnetic structures according to Example 1 prepared through a base source having a pH of 12 or higher was observed. The observed results are summarized in <Table 3> below.

pH Plating layer structure 1-8 No plating layer is formed 9~11 Formation of conformal FeCo plating layer 12 or more Part of the FeCo plating layer + FeCo independent crystalline particles

As can be seen from <Table 3>, by making the exchange magnetic coupling effect between the magnetic core fiber and the magnetic shell appear larger than the dipole interaction of the magnetic core fiber and the magnetic shell, the coercive force and maximum magnetic energy (BH _max ) In order to improve the magnetic properties, it was found that controlling the pH of the base source to more than 8 and less than 12 is an effective method.

21 is a photograph of a fibrous magnetic structure according to Examples 6 and 7 of the present invention, and FIG. 22 is a photograph of a fibrous magnetic structure according to Examples 5 and 8 of the present invention.

21(a) and (b), the fibrous magnetic structures according to Examples 6 and 7 were photographed by SEM, and referring to FIGS. 22A and 22B, Examples It was shown by SEM photographs of the fibrous magnetic structure according to Example 5 and Example 8.

As can be seen in (a) and (b) of Figure 21, the fibrous magnetic structure according to Example 6 and Example 7, it can be confirmed that the FeCo layer is easily formed on the magnetic core fiber (Sm ₂ Co ₁₇ ) surface there was. However, as can be seen in (a) of FIG. 22, in the fibrous magnetic structure according to Example 5, the FeCo layer was not formed on the surface of the magnetic core fiber (Sm ₂ Co ₁₇ ), which was confirmed in FIG. 22 (b). As can be seen, in the fibrous magnetic structure according to Example 8, it was confirmed that FeCo was formed in an independent particle shape.

23 is a graph showing the crystallinity of the fibrous magnetic structure according to Examples 5 to 8 of the present invention.

Referring to FIG. 23, after preparing the fibrous magnetic structure according to Examples 5 to 8 (50°C, 70°C, 80°C, 90°C) of the present invention, the intensity (au) according to 2θ (degree) was prepared. ) Was measured and shown.

As can be seen from FIG. 23, it was confirmed that the fibrous magnetic structures according to Examples 5 to 8 gradually increased in crystallinity. That is, it was found that as the temperature of the base source plated on the magnetic core fiber increased, the crystal of FeCo constituting the magnetic shell of the fibrous magnetic structure to be manufactured also increased.

24 is a graph showing magnetic properties of fibrous magnetic structures according to Examples 5 to 8 of the present invention.

Referring to FIG. 24, after preparing a fibrous magnetic structure according to Examples 5 to 8 (50°C, 70°C, 80°C, 90°C) of the present invention, Magnetization (emu/g) and Coercivity (Oe ), and Density (g/cm ³ ) were measured and shown.

As can be seen in FIG. 24, it was confirmed that the magnetization of the fibrous magnetic structure according to Examples 5, 6, and 7 gradually increased, and the magnetization of the fibrous magnetic structure according to Example 8 decreased. Could That is, in the case of the fibrous magnetic structure manufactured in the section where the temperature of the base source plated on the magnetic core fiber increases from 50℃ to 80℃, magnetization gradually increases, but the fibrous magnetic structure manufactured in the section above 80℃ It was confirmed that magnetization gradually decreased.

As a result, as can be seen from Figs. 21 to 24, the exchange magnetic coupling effect between the magnetic core fiber and the magnetic shell is made larger than the dipole interaction of the magnetic core fiber and the magnetic shell, so that the coercive force and the maximum magnetic energy (BH _max. In order to improve magnetic properties such as ), it was found that controlling the temperature of the base source to more than 70°C and less than 90°C is an effective method.

In the above, the present invention has been described in detail using preferred embodiments, but the scope of the present invention is not limited to specific embodiments, and should be interpreted by the appended claims. In addition, those who have acquired ordinary knowledge in this technical field should understand that many modifications and variations can be made without departing from the scope of the present invention.

100: fibrous magnetic structure
110: magnetic fiber
120: magnetic shell

Claims (14)

Preparing a magnetic core fiber including a rare earth element and a core transition metal element;
Disposing catalyst particles on the magnetic core fiber; And
A plating process using a base source including a first precursor including a first shell transition metal element and a second precursor including a second shell transition metal element, and surrounding the magnetic core fiber by using the catalyst particle A method of manufacturing a fibrous magnetic structure comprising the step of forming a magnetic shell including a compound of the first shell transition metal element and the second shell transition metal element.
The method of claim 1,
The base source is provided for a time of less than 20 minutes, the method of manufacturing a fibrous magnetic structure comprising the thickness of the magnetic shell is formed to 40 nm or less.
The method of claim 1,
The method of manufacturing a fibrous magnetic structure comprising the temperature of the base source is controlled to less than 90 ℃ more than 70 ℃.
The method of claim 1,
The base source further comprises a pH adjusting agent,
The method of manufacturing a fibrous magnetic structure comprising controlling the pH of the base source to less than 8 and less than 12.
The method of claim 1,
The magnetic core fiber preparation step,
Preparing a source solution containing the rare earth element and the core transition metal element;
Electrospinning the source solution to prepare a preliminary magnetic core fiber;
Oxidizing the preliminary magnetic core fiber by heat treatment; And
A method of manufacturing a fibrous magnetic structure comprising the step of reducing the oxidized preliminary magnetic core fiber by heat treatment using a reducing agent.
Magnetic core fibers including rare earth elements and core transition metal elements; And
It includes a magnetic shell surrounding the magnetic core fiber and including the first shell transition metal element and the second shell transition metal element,
An exchange-coupling effect between the magnetic core fiber and the magnetic shell is greater than a dipolar interaction of the magnetic core fiber and the magnetic shell.
The method of claim 6,
A fibrous magnetic structure including one representing one peak in the graph representing the value of <Equation 1> below with respect to the applied field value Oe.
<Equation 1>
dM/dH
(M: Magnetic moments, H: External magnetic field applied)
The method of claim 6,
The magnetic core fiber is a fibrous magnetic structure comprising a plurality of single crystals connected in series in the longitudinal direction of the magnetic core fiber.
The method of claim 6,
A fibrous magnetic structure comprising a diameter of the magnetic core fiber is smaller than a size of a terminal hole (single-domain) of the magnetic core fiber.
The method of claim 6,
The thickness of the magnetic shell is a fibrous magnetic structure comprising less than twice the width (domain-wall width) of the terminal wall of the magnetic core fiber.
The method of claim 6,
The magnetic shell is a fibrous magnetic structure comprising the one disposed conformally on the magnetic core fiber.
The method of claim 6,
The rare earth element is a fibrous magnetic structure comprising any one of La, Ce, Pr, Nd, Sm, or Gd.
The method of claim 6,
The core transition metal element, the first shell transition metal element, and the second shell transition metal element include any one of Fe, Co, or Ni.
The method of claim 6,
The core transition metal element is a fibrous magnetic structure including any one of the first shell transition metal element or the second shell transition metal element.

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