Electromagnetic-wave-absorbing materials for various applications

Patent metadata

Field	Value
Publication number	US-11081802-B2
Application number	US-201716087565-A
Country	US
Kind code	B2
Filing date	Mar 20, 2017
Priority date	Mar 21, 2016
Publication date	Aug 3, 2021
Grant date	Aug 3, 2021

Abstract

One subject of the present invention is an electromagnetic-wave-absorbing composite material comprising a carrier matrix (11) and an electromagnetic-wave-absorbing filler (12). According to the invention, the carrier matrix (11) is a cork matrix, which is formed of particles the equivalent diameter Del of which is comprised between 10 μm and 5 mm, and the composite material (1) has a real permittivity higher than 1.2 and a dielectric loss tangent tan δ higher than 0.1. Another subject of the present invention is a method for producing such a material, and the use of this material as an absorber, in particular in an anechoic chamber, or as a radar absorber in stealth devices, or even to improve the electromagnetic compatibility of electronic devices.

First claim

The invention claimed is:

1. Composite material that absorbs electromagnetic waves and comprises:
a supporting matrix,
a filler configured to absorb electromagnetic waves,
said composite material being characterised in that the supporting matrix is a matrix of cork, which is formed of particles having an equivalent diameter D e1 between 10 μm and 5 mm, and
in that said composite material has a real permittivity greater than 1.2 and a dielectric loss tangent tan δ greater than 0.1.

2. Material according to claim 1 , wherein the cork of the supporting matrix is natural cork or expanded cork.

3. Material according to claim 1 , wherein the particles of cork are coated with said filler.

4. Material according to claim 1 , wherein said filler is in the form of microparticles or nanoparticles having an equivalent diameter D ec between 1 nm and 1000 μm.

5. Material according to claim 1 , wherein said filler is a magnetic filler, a dielectric filler, or a filler that conducts electricity.

6. Material according to claim 5 , wherein said filler is a filler that conducts electricity, in the form of metal particles, particles of carbon, carbon fibres or carbon nanotubes, or in the form of graphene.

7. Material according to claim 1 , further comprising a binder made of thermoplastic or thermosetting polymer resin.

8. Material according to claim 1 , wherein the composite material is configured to absorb electromagnetic waves in a range of 0.5 GHz to 18 GHz.

9. Material according to claim 1 , wherein the composite material is an isotropic material.

10. A method comprising:
using the material as defined according to claim 1 as an absorber in an anechoic chamber.

11. A method comprising:
using the material as defined according to claim 1 as a radar absorber in stealth devices.

12. A method comprising:
using the material as defined according to claim 1 in order to improve the electromagnetic compatibility of electronic devices.

13. Method for manufacturing a composite material that absorbs electromagnetic waves as defined according to claim 1 , said method involving:
A) Creation of a preparation containing:
particles of cork, the equivalent diameter Dei of which is between 10 μm and 5 mm, and
a filler that absorbs electromagnetic waves,

B) Shaping of said composite material from said preparation.

14. Method according to claim 13 , wherein the step A) of creating said preparation comprises the following substeps:
A1) placing said filler in an aqueous solution;
A2) adding the aqueous solution containing said filler to particles of cork, then mixing until a homogenous preparation is obtained;
A3) drying of said homogenous preparation in open air or in a drier at a temperature between 50° C. and 120° C., until complete evaporation of the aqueous phase, in such a way as to obtain particles of cork coated with filler.

15. Method according to claim 14 , wherein a resin is added, after the drying A3), to said particles of cork coated with filler in order to obtain a bound preparation.

16. Method according to claim 15 , wherein the resin is a resin that is biosourced.

17. Method according to claim 14 , wherein the step B) of shaping is carried out by compacting said particles of cork coated with filler at a pressure between 10 MPa and 10,000 MPa.

18. Method according to claim 14 , wherein the step B) of shaping is carried out by:
introducing said particles of cork coated with filler into a container having a specific shape; then
heating said granules of cork coated with filler to a temperature of at least 200° C. in order to obtain a composite material having a mechanical strength sufficient to make it suitable for being manipulated.

19. Method according to claim 13 , wherein the step A) of creating said preparation comprises the following substeps:
A′1) incorporation of said filler into a resin; then
A′2) introduction of said particles of cork into the mixture of resin and filler thus formed.

20. Method according to claim 13 , wherein the step B) of shaping is carried out via introduction of the preparation thus obtained into a container having a specific shape.

Assignees

• Univ Rennes

Inventors

• MEJEAN Chloé
• BENZERGA Ratiba
• Sharaiha Ala

Classifications

• C08L97/007 Primary

  Cork · CPC title

• H01Q17/00

  Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems · CPC title

• H01Q17/004

  using non-directional dissipative particles, e.g. ferrite powders (H01Q17/005 takes precedence; flake-like H01Q17/002) · CPC title

• H01Q17/008 Primary

  with a particular shape (H01Q17/007 takes precedence) · CPC title