Electromagnetic interference (EMI) shielding effectiveness (SE) of syntactic foam containing metal-coated hollow carbon microspheres

Abstract

Syntactic foam is a binary composite consist of hollow particles and a matrix. Due to its good mechanical properties, it is widely applied in aerospace and marine industries. However, among the past studies, there is a significant lack of research to investigate its functional property such as its electromagnetic interference (EMI) shielding performance. Therefore, the objective of this work is to develop syntactic foam with improved EMI shielding performance by modifying hollow particles with deposited metal layers. Hollow carbon microspheres (HCMs), which were produced from hollow phenolic microspheres, were used as the filler to fabricate syntactic foam with phenolic resin. In attempt to improve the EMI shielding performance of the syntactic foam, HCMs were coated with nickel and copper by electroless plating. Syntactic foams containing 28-30 vol% of un-coated HCMs, copper-coated HCMs and nickel-coated HCMs, respectively, were fabricated. Results verified that EMI shielding performance of syntactic foam was clearly improved with metal-coated HCMs. Three EMI shielding mechanisms, namely, reflection, absorption and multiple-reflection were discussed. The shielding mechanism for syntactic foam containing different types of HCMs will be compared. The EMI shielding effectiveness (SE) value of syntactic foam fabricated with copper-coated HCMs was about 4 dB and 8 dB, for samples in the thickness of 3mm and 6mm, respectively. The EMI SE for syntactic foam with nickel-coated HCMs in the thickness of 3mm is about 10 dB and the highest EMI SE in this work was about 16 dB for syntactic foam containing nickel-coated HCMs in the thickness of 6mm, which demonstrates the potential of syntactic foam in EMI shielding applications.