Electromagnetic wave absorption properties of MWCNTs-COOH/cement composites with different shapes of chiral, armchair and zigzag

Abstract

The electromagnetic wave absorption performances and the dielectric properties of multi-walled carbon nanotube (MWCNT) functionalization with carboxyl (-COOH) group/cement composites with different shapes; chiral, zigzag and armchair were investigated. In this study, the influence of the sample thickness and the MWCNT shape on the electromagnetic wave reflection loss, insertion loss and absorption were studied in the frequency range of 8–12 GHz. The addition of 0.1 wt% MWCNT dramatically increases the absorption properties of the cement mortar in the frequency range of 8–10 GHz. With the increase of thickness from 3 mm to 6 mm, the frequency bandwidths of the reflection loss for MWCNT/cement composites increases but the number of peaks decreases. Moreover, the reflection loss peak has increased dramatically with increasing thickness. In composite specimens prepared with a thickness of 3 mm, the chiral sample has higher absorption than the zigzag and armchair samples. The absorption behavior of composites with thickness of 6 mm at 10 GHz to 11.5 GHz is different to each other. The chiral sample shows higher absorption before 9 GHz and after 11 GHz. Experimental results show that the composite specimens at both thicknesses of 3 mm and 6 mm at frequencies below 10–10.5 GHz have higher absorption properties than the control sample. The peaks created on the relative permittivity curves also showed the nonlinear dielectric resonant behavior. Furthermore, the structural analysis and surface morphology of MWCNT/cement composites with different shapes have been explored using SEM technique.