Pastes for electromagnetic interference shielding

Abstract

A paste has been developed for electromagnetic interference shielding by mixing stainless steel fibers (8-µm diameter) and graphite flakes (5 µm) in a water-based graphite colloid (containing submicron graphite flakes and a binder) in a volume ratio 0.5:20:100. The resulting coating of thickness 0.1-0.2 mm after drying exhibits shielding effectiveness of 34 dB at 1 GHz, primarily due to reflection. The paste is superior to those containing graphite flakes or carbon filaments (0.1-µm diameter), due to the higher shielding effectiveness of the steel fibers. The graphite flakes in the paste serves to help suspend the steel fibers, in addition to contributing to shielding.

Combined Use of Magnetic and Electrically Conductive Fillers in a Polymer Matrix for Electromagnetic Interference Shielding

“…This value is higher than the value of 34 dB at 1 GHz previously reported for a coating of similar thickness but in the form of a water-based dispersion comprising discontinuous stainless steel fiber (8 lm diameter), 5 lm graphite flake, and submicron graphite flake. 32 Without the steel fiber in the dispersion, the shielding effectiveness is only 28 dB. The effectiveness of the steel fiber is attributed mainly to its small diameter (the skin effect), although the large aspect ratio of the fiber may help the electrical connectivity and the limited magnetic character of the steel may help the shielding through absorption.…”

“…Reference 32 uses water as the vehicle, whereas this work uses a polymer as the vehicle. A water-based dispersion 32 has the advantage of the evaporation of the water from the coating after coating application causing an increased degree of direct contact between the conductive fiber and flake. However, in spite of the small amount of binder in a water-based dispersion, the coating is mechanically weak and the adhesion of the coating is also relatively weak, compared to the polymer-based coating of this work.…”

Electromagnetic Interference Shielding Efficiency in the Range 8.2-12.4 GHz of Polymer Composites with Dispersed Carbon Nanoparticles

“…Carbon materials have been intensively investigated as electromagnetic interference (EMI) shielding materials [1][2][3][4][5][6]. Colloidal graphite has been applied in shielding pastes [2], and conductive carbon black has shown good characteristics in composite radar absorbing structures [3] and in rubbers composites at high content [4].…”

“…Colloidal graphite has been applied in shielding pastes [2], and conductive carbon black has shown good characteristics in composite radar absorbing structures [3] and in rubbers composites at high content [4]. Recently multi-walled carbon nanotubes (MWCNT) have attracted a lot of attention from the viewpoint of their potential application as EMI shielding additives to polymers due to their high shielding characteristics at low contents [5].…”

Función de apantallamiento de interferencia electromagnética de pastas de cemento con materiales carbonosos y cenizas volantes procesadas

“…Esta aplicación está aumentando en interés en la sociedad actual debido al creciente uso de dispositivos electrónicos que se ven afectados por las radiaciones ambientales, especialmente por la radiación de radiofrecuencias. Durante los últimos años, el uso de tecnologías inalámbricas ha aumentado significativamente, siendo necesario proteger de este tipo de radiaciones algunos edificios, instalaciones o habitaciones, por ejemplo, en hospitales, edificios militares o gubernamentales, estaciones eléctricas o instalaciones estratégicas (2)(3)(4).…”