Layered hybrid composites using multi-walled carbon nanotube film as reflection layer and multi-walled carbon nanotubes/neodymium magnet/ epoxy as absorption layer perform selective electromagnetic interference shielding

Abstract

This work develops a unique layered structural composite to prevent the device from internal electromagnetic (EM) waves’ self-disturbance and external EM wave interference. The composite is composed of two layers, the inner layer is a hybrid composite, using MWCNTs and NdFeB powders as fillers and epoxy as matrix, which is designed as absorbent layer, and the outer is MWCNT-coated non-woven fabric, which is treated as reflection layer. The inner layer containing MWCNTs and magnetic powder of NdFeB can firstly absorb parts of EM waves generating from inside devices, and when the rest EM waves transmit through the inner layer and impinge to the outer layer, almost all of the waves will be reflected back. The reflected waves will go through the inner layer and be absorbed again. In the meanwhile, as the external EM waves impinge to the outer layer, they will be reflected immediately. The optimal combination of this study is able to achieve over 92% (−23.09 dB) absorption and leave least than 8% (−11 dB) reflection of internal EM waves, and over 99.99% reflection of external EM waves.