Electromagnetic-wave-absorbing materials for various applications
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 D el 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.
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.