Modulation of electromagnetic absorption and shielding properties of geopolymer nanocomposites by designing core–shell structure of carbon nanotubes

Abstract

In this work, an electromagnetic (EM) protective building material was developed by combining silica (SiO2)-grafted carbon nanotubes (S@CNTs) with geopolymer (GeoP). The EM absorption and shielding properties of the GeoP nanocomposites were modulated by tailoring the SiO2 shell thickness. With the increase in shell thickness, the attenuation coefficient decreased, while the impedance matching degree, which acted as a prerequisite for evaluating EM absorption performance, improved. As a result, the minimum reflection loss (RLmin) reached −38.4 dB at 11.1 GHz and the effective absorption bandwidth of 3.4 GHz with a thickness of 2.9 mm was obtained. Practically, the electron transport capability was promoted with a thinner SiO2 shell, leading to an improvement in electrical conductivity. As the conductivity increased, the EM interference shielding effectiveness (SE) increased to 11.0 dB, while the RLmin also increased to −8.7 dB. Based on the underlying mechanism analysis, the strategy for modulating EM performance can be extended to other building materials.