Electromagnetic wave absorption of multi-walled carbon nanotube–epoxy composites in the R band

Abstract

Multi-walled carbon nanotube (MWCNT)–epoxy composites with MWCNT (outer diameter 8–15 nm) loadings from 0.1 to 5 wt% were fabricated. The morphologies, conductivities, dielectric permittivities, and electromagnetic (EM) wave absorptions of the MWCNT–epoxy composites were investigated. The results showed that the EM wave absorptions strongly depended on the complex permittivities of the composites. An abrupt enhancement of conductivity by 9 orders of magnitude for the composite sample with 5 wt% MWCNT loading was observed, which is associated with a sharp improvement in the electromagnetic absorption in the R band (26.5–40 GHz) and is characterized by the formation of a conductive network structure consisting of separated MWCNT aggregates and connected MWCNT bundle bridges in the composites. The electrically-conductive composite allows charge transport between the conductive MWCNT components and contributes to the substantial improvement of the electromagnetic absorption of the MWCNT–epoxy composites.