Composite material and shielding against electromagnetic radiation
The present invention relates to a composite material for shielding electromagnetic radiation in the GHz range, comprising a matrix material and metal fibers, wherein the metal fibers contain at least one of the elements selected from the group consisting of copper, silver, gold, nickel, palladium, platinum, cobalt, iron, chromium, vanadium, titanium, aluminum, silicon, lithium, combinations of the foregoing and alloys containing one or more of the foregoing. Moreover, the present invention relates to a shielding against electromagnetic radiation comprising said composite material and to an electronic device comprising at least one component which is shielded against electromagnetic radiation with said shielding.
1 . A composite material for shielding electromagnetic radiation in the GHz range, comprising a matrix material and metal fibers, wherein the metal fibers contain at least one of the elements selected from the group consisting of copper, silver, gold, nickel, palladium, platinum, cobalt, iron, chromium, vanadium, titanium, aluminum, silicon, lithium, combinations of the foregoing and alloys containing one or more of the foregoing, wherein the metal fibers have a surface to volume ratio of 0.5 to 4 μm −1 , wherein the metal fibers provide absorption loss of 20 to 60 dB over a frequency band range of 3 to 300 GHz, wherein the metal fibers are not in electrical contact with each other, wherein the amount of the metal fibers in the composite is set such that it is below the percolation threshold, ensuring that the fibers are not in contact with each other, and wherein the average distance between adjacent fibers is λ/10 or less, where λ is the wavelength of the electromagnetic radiation to be shielded.
2 . Composite material according to claim 1 , wherein the metal fibers are of at least one material selected from the group consisting of
Cu and its alloys with Si, Fe and Mn,
Al and its alloys with Si, Mg, Ti, Fe and Mn,
μ-metals, and
Gold and Silver and their alloys.
3 . Composite material according to claim 1 , wherein the metal fibers are copper metal fibers or copper-alloy fibers or aluminum metal fibers or aluminum-alloy fibers.
4 . Composite material according to claim 1 , wherein the metal fibers are not made of stainless steel.
5 . Composite material according to claim 1 , wherein the metal fibers have a cross-section which is not circular.
6 . Composite material according to claim 1 , wherein the metal fibers have a cross-section having one edge that is less curved than the edge of another part of the cross-section.
7 . Composite material according to claim 1 , wherein the metal fibers have a cross-section that has one edge that is not curved.
8 . Composite material according to claim 1 , wherein the amount of metal fibers in the composite material is in the range of 0.02 to 2.5 wt. % based on the total weight of the composite material.
9 . Composite material according to claim 1 , wherein the matrix is an electrically insulating material.
10 . Composite material according to claim 1 , wherein the composite material is an electromagnetic shielding.
11 . Composite material according to claim 1 , wherein the electromagnetic shielding has one layer.
12 . Composite material according to claim 3 , wherein the metal fibers are one of Cu 99 Si 1 , Cu 98 Si 2 , Cu 96 Si 4 , Cu 88 Si 12 , Cu 92 Sn 8 , and Al 99 Si 1 .
13 . Composite material according to claim 4 , wherein the metal fibers are not made of steel.
14 . Composite according to claim 6 , wherein the cross-section is an elliptically shaped cross-section or a crescent-shaped cross-section.
15 . Composite according to claim 7 , wherein the cross-section of the metal fibers is rectangular.
16 . Composite according to claim 9 , wherein the matrix is a polymeric material.