Hybrid Nanocomposites With Organoclay and Carbon-Based Fillers for EMI Suppression

The reinforcing role of clays in modern nanocomposites raises the question upon potential synergies with other fillers, in terms of their microwave properties and performance. To this effect, hybrid, multiphase composites are fabricated to comprise organomodified nanoclay (NC) and multiwalled carbon nanotubes (MWCNTs) or carbon black nanoparticles (CB) at varying concentrations in epoxy resin matrix (ER). The performed electromagnetic (EM) characterization in the 2–18-GHz band reveals that NC generally degrades the effective permittivity $\varepsilon _{{\rm eff}}^{\ast}$ of the NC/CB/epoxy composites, whereas for 2wt% NC a local $\varepsilon _{{\rm eff}}^{\ast}$ maximum is observed in the NC/MWCNT/epoxy system. This divergent impact of NC is attributed to different microstructural features affecting the dipolar dielectric polarization. Finally, the composites with high $\varepsilon _{{\rm eff}}^{\ast}$ contribute to the miniaturization of reflection reducing and shielding panels, since the respective return and transmission loss are found to be dominated by the destructive interference mechanism. For both topologies, the composite loaded with 2wt% NC and 0.5wt% MWCNT is evaluated as the most effective in attenuating the EM waves. Through the analysis of the microwave dielectric properties and the shielding mechanisms, the material design objectives emerge along with the potential of NC/carbon nanotubes composites for suppression of EM interference.