Radio wave absorber

Patent metadata

Field	Value
Publication number	US-12160984-B2
Application number	US-202117518825-A
Country	US
Kind code	B2
Filing date	Nov 4, 2021
Priority date	May 14, 2019
Publication date	Dec 3, 2024
Grant date	Dec 3, 2024

Abstract

There is provided a radio wave absorber including a powder of a hexagonal ferrite; and a binder, in which the radio wave absorber has a squareness ratio in a range of 0.40 to 0.60.

First claim

What is claimed is:

1. A radio wave absorber comprising:
a powder of a hexagonal ferrite; and
a binder,
wherein the radio wave absorber has a thickness of 2 mm or more, a squareness ratio as measured in a randomly selected measurement direction A in a range of 0.40 to 0.60, and a squareness ratio in the same range as measured in a measurement direction B which is perpendicular to the measurement direction A, each measurement direction being the direction in which a magnetic field is applied at the time of measurement, the squareness ratios being measured in an oscillating sample magnetometer, with the intensity of magnetization of a measurement sample being measured with respect to an applied magnetic field under a maximum applied magnetic field of 50 kOe and a magnetic field sweep rate of 104 Oe/s (seconds) in an environment with an ambient temperature of 23° C., and the measurement sample being the radio wave absorber itself or a sample cut out therefrom.

2. The radio wave absorber according to claim 1 ,
wherein the radio wave absorber has a squareness ratio as measured in measurement direction A in a range of 0.45 to 0.55, and a squareness ratio as measured in measurement direction B in the same range.

3. The radio wave absorber according to claim 1 ,
wherein the hexagonal ferrite has a composition represented by Formula 1,
AFe (12-X) Al X O 19   Formula 1

in Formula 1, A represents at least one kind of atom selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.50≤x≤8.00.

4. The radio wave absorber according to claim 3 ,
wherein an atom represented by A in Formula 1 includes Sr.

5. The radio wave absorber according to claim 2 ,
wherein the hexagonal ferrite has a composition represented by Formula 1,
AFe (12-X) Al X O 19   Formula 1

in Formula 1, A represents at least one kind of atom selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.50≤x≤8.00.

6. The radio wave absorber according to claim 5 ,
wherein an atom represented by A in Formula 1 includes Sr.

7. The radio wave absorber according to claim 1 ,
wherein the radio wave absorber is a molded product obtained by molding a composition containing the powder of a hexagonal ferrite and the binder.

8. The radio wave absorber according to claim 7 ,
wherein the radio wave absorber is a plate-shaped molded product.

9. The radio wave absorber according to claim 2 ,
wherein the radio wave absorber is a molded product obtained by molding a composition containing the powder of a hexagonal ferrite and the binder.

10. The radio wave absorber according to claim 9 ,
wherein the radio wave absorber is a plate-shaped molded product.

11. The radio wave absorber according to claim 3 ,
wherein the radio wave absorber is a molded product obtained by molding a composition containing the powder of a hexagonal ferrite and the binder.

12. The radio wave absorber according to claim 11 ,
wherein the radio wave absorber is a plate-shaped molded product.

13. The radio wave absorber according to claim 4 ,
wherein the radio wave absorber is a molded product obtained by molding a composition containing the powder of a hexagonal ferrite and the binder.

14. The radio wave absorber according to claim 13 ,
wherein the radio wave absorber is a plate-shaped molded product.

15. The radio wave absorber according to claim 5 ,
wherein the radio wave absorber is a molded product obtained by molding a composition containing the powder of a hexagonal ferrite and the binder.

16. The radio wave absorber according to claim 15 ,
wherein the radio wave absorber is a plate-shaped molded product.

17. The radio wave absorber according to claim 6 ,
wherein the radio wave absorber is a molded product obtained by molding a composition containing the powder of a hexagonal ferrite and the binder.

18. The radio wave absorber according to claim 17 ,
wherein the radio wave absorber is a plate-shaped molded product.

19. The radio wave absorber according to claim 1 ,
wherein the hexagonal ferrite is a substitution-type magnetoplumbite-type hexagonal ferrite in which a part of iron atoms of the magnetoplumbite-type hexagonal ferrite is substituted with an aluminum atom.

Assignees

• Fujifilm Corp

Inventors

• Shirata Masashi
• Hashimoto Hirokazu

Classifications

• H01F1/11

  in the form of particles {(for magnetic record carriers G11B5/70626)} · CPC title

• C08K2003/2265

  of iron · CPC title

• H01F1/37

  in a bonding agent · CPC title

• C08L101/00

  Compositions of unspecified macromolecular compounds · CPC title

• C08K3/22

  of metals · CPC title