METAL FILAMENTS FOR ELECTROMAGNETIC INTERFERENCE SHIELDING

摘要

A material comprising filaments, said filaments comprising at least a metal coating, each filament having a diameter less than 2 mu m and a length more than 100 mu m, displays high effectiveness for shielding electromagnetic interference (EMI) when dispersed in a matrix to form a composite material. Said matrix is selected from the group consisting of polymers, ceramics and polymer-ceramic combinations. Said metal is selected from the group consisting of nickel, copper, cobalt, silver, gold, tin, zinc, nickel-based alloys, copper-based alloys, cobalt-based alloys, silver-based alloys, gold-based alloys, tin-based alloys and zinc-based alloys. Said filaments preferably comprise carbon filaments. The incorporation of 7 vol.% of this material in a matrix that is incapable of EMI shielding results in a composite plate that is about 3 mm thick and is capable of shielding EMI at 1-2 GHz with an effectiveness of at least 65 dB. A process for making this material comprises the steps of (i) fabricating carbon filaments from carbonaceous gases, (ii) removing polyaromatic hydrocarbons from the surface of said carbon filaments, and (iii) coating said carbon filaments with said metal. Said solvent is preferably selected from the group consisting of acetone, methylene chloride, toluene and carbon disulfide.