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US-12620518-B2 - Magnetic particles and method for producing same, magnetic core, and coil component

US12620518B2US 12620518 B2US12620518 B2US 12620518B2US-12620518-B2

Abstract

Magnetic particles, each including a core made of a metal magnetic material and a coating film which covers a surface of the core, in which the coating film contains a reaction product formed using a first metal alkoxide containing no metal atom-carbon atom bond in a molecule, and a second metal alkoxide containing two or more metal atom-carbon atom bonds in a molecule.

Inventors

  • Ryota SAISHO
  • Hironobu Kubota

Assignees

  • MURATA MANUFACTURING CO., LTD.

Dates

Publication Date
20260505
Application Date
20220127
Priority Date
20210204

Claims (12)

  1. 1 . Magnetic particles, each comprising a core made of a metal magnetic material, and a coating film which covers a surface of the core, wherein the coating film contains a structure derived from a reaction between a first metal alkoxide containing no metal atom-carbon atom bond in a molecule, and a second metal alkoxide containing two or more metal atom-carbon atom bonds in a molecule, wherein the first metal alkoxide is from 5% by weight to 95% by weight and the second metal alkoxide is from 5% by weight to 95% by weight, and the weight ratio is a ratio where the total weight of the first metal alkoxide and the second metal alkoxide is 100% by weight.
  2. 2 . The magnetic particles according to claim 1 , wherein the first metal alkoxide is a compound or a mixture of two or more compounds represented by the general formula (1) below: M 1 (OR 1 ) x (1) wherein, in the formula (1), M 1 is Li, Na, Mg, K, Ca, Cu, Sr, Y, Ba, Ce, Ta, Bi, Si, Ti, Al, or Zr; x is the valence of M 1 and is an integer of 1 to 4; R 1 s are each independently an alkyl group having 1 to 10 carbon atoms or —C(R 2 )═CH—CO—R 3 (in the formula, R 2 is an alkyl group having 1 to 10 carbon atoms, and R 3 is an alkyl group having 1 to 30 carbon atoms, an alkyloxy group having 1 to 30 carbon atoms, or an alkenyloxy group having 1 to 30 carbon atoms); and among R 1 s, when two adjacent R 1 s are the alkyl groups, the two adjacent R 1 s may be joined to each other to configure a ring, together with the oxygen atoms to which the two R 1 s are attached and the M 1 atom to which the oxygen atoms are attached.
  3. 3 . The magnetic particles according to claim 1 , wherein the second metal alkoxide is a compound having two or more Si atom-carbon atom bonds in a molecule.
  4. 4 . The magnetic particles according to claim 1 , wherein the second metal alkoxide is a compound or a mixture of two or more compounds represented by the general formula (2A) below: (R 211 O) 3 Si—R 31 —Si(OR 212 ) 3 (2A) wherein, in the formula (2A), R 211 and R 212 are each independently an alkyl group having 1 to 10 carbon atoms; and R 31 is a divalent hydrocarbon group having 1 to 20 carbon atoms.
  5. 5 . The magnetic particles according to claim 4 , wherein in the general formula (2A), R 31 is a divalent hydrocarbon group having 1 to 10 carbon atoms.
  6. 6 . The magnetic particles according to claim 5 , wherein in the general formula (2A), R 31 is a divalent hydrocarbon group having 2 to 8 carbon atoms.
  7. 7 . The magnetic particles according to claim 1 , wherein the coating film has an average thickness of from 1 nm to 100 nm.
  8. 8 . The magnetic particles according to claim 1 , wherein the metal magnetic material contains Fe.
  9. 9 . The magnetic particles according to claim 1 , wherein the metal magnetic material is Fe, an Fe—Si alloy, an Fe—Si—Cr alloy, an Fe—Al alloy, an Fe—Si—Al alloy, or an Fe—Ni alloy.
  10. 10 . A magnetic core comprising the magnetic particles according to claim 1 .
  11. 11 . A coil component comprising: the magnetic core according to claim 10 ; and a coil wound around the magnetic core.
  12. 12 . A coil component comprising: a body which contains the magnetic particles according to claim 1 and a resin; and a coil embedded in the body.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims benefit of priority to Japanese Patent Application No. 2021-016771, filed Feb. 4, 2021, the entire content of which is incorporated herein by reference. BACKGROUND Technical Field The present disclosure relates to magnetic particles and a method for producing the same, and also relates to a magnetic core and a coil component produced by using the magnetic particles. Background Art Coil components, such as inductors and choke coils, are used in various electrical devices and electronic devices. A coil component generally includes a coil and a magnetic core. In recent years, the size of electrical devices and electronic devices has been increasingly reduced, and consequently, there has been a demand for reduction in size of coil components used therein. Furthermore, besides being small-sized, coil components are required to have excellent magnetic, electrical and mechanical characteristics, and therefore, magnetic cores are required to have high magnetic permeability, high magnetic flux density, low loss, and high strength. In particular, when used in the high-frequency range, in order to suppress an increase in eddy current loss, magnetic cores are required to have high specific resistance. In order to satisfy such requirements, magnetic cores are known which are produced by forming a soft magnetic material into fine particles (powder), covering a surface of each particle with an insulating coating film, and performing compression molding. For example, Japanese Unexamined Patent Application Publication No. 2013-209693 discloses a magnetic core obtained by compression molding of powder of magnetic particles in which a surface of each particle is coated with carbon and further coated with a metal oxide composed mainly of silicon oxide. SUMMARY However, the present inventors have found that the following problems arise in the existing magnetic core (e.g., the magnetic core described in Japanese Unexamined Patent Application Publication No. 2013-209693): the magnetic particles easily adhere or cohere to each other and do not exhibit sufficient filling performance during compression molding, and therefore the resulting magnetic core has relatively low relative permeability; and the coating film does not have sufficient fracture resistance and is easily fractured during compression molding, and therefore the resulting magnetic core has relatively low specific resistance. Accordingly, the present disclosure provides magnetic particles which are used to produce a magnetic core having sufficiently higher relative permeability and specific resistance and a method for producing the magnetic articles and to provide a magnetic core and a coil component produced by using the magnetic particles. The present inventors have performed thorough studies in order to solve the problems described above. As a result, it has been found that, by forming a specific coating film on a surface of each core made of a magnetic material used for producing a magnetic core, it is possible to produce a magnetic core having high specific resistance and high relative permeability, thus leading to the present disclosure. The present disclosure relates to magnetic particles, each including a core made of a metal magnetic material and a coating film which covers a surface of the core, in which the coating film contains a reaction product formed using a first metal alkoxide containing no metal atom-carbon atom bond in a molecule, and a second metal alkoxide containing two or more metal atom-carbon atom bonds in a molecule. The present disclosure also relates to a method for producing magnetic particles including mixing cores made of a metal magnetic material, a first metal alkoxide containing no metal atom-carbon atom bond in a molecule, a second metal alkoxide containing two or more metal atom-carbon atom bonds in a molecule, and a solvent; and hydrolyzing and drying the first metal alkoxide and the second metal alkoxide to obtain magnetic particles, each including the core made of a metal magnetic material and a coating film which covers a surface of the core. By using magnetic particles of the present disclosure, it is possible to produce a magnetic core having sufficiently higher relative permeability and specific resistance. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing a core of a magnetic particle of the present disclosure, and a coating film covering the core; FIG. 2 is a schematic conceptual diagram showing a main bonding state at the interface between a coating film and a core in a magnetic particle of the present disclosure; FIG. 3 is a schematic conceptual diagram showing a main structure of a coating film in a magnetic particle of the present disclosure; FIG. 4 is a schematic sketch showing a front view of a coil component including a magnetic core of the present disclosure; FIG. 5 is a schematic perspective view showing another coil co