Fe3O4 incorporated geopolymer nanocomposites for microwave absorption: Role of size, structure, and dispersion

Abstract

The demand for sustainable construction materials with outstanding microwave absorbing properties is essential to provide comprehensive protection against the harmful effects of electromagnetic (EM) radiation. Herein, a series of Fe3O4-based materials with similar shapes, including Fe3O4 nanospheres with average sizes of 10 nm (Fe3O4-10) and 400 nm (Fe3O4-400) and hollow Fe3O4 nanospheres with an average size of 400 nm (H-Fe3O4-400), were synthesized. SiO2 was coated on the surface of Fe3O4-based materials. Geopolymer (GP) nanocomposites containing different Fe3O4-based materials were prepared. The roles of the size, structure, and dispersion of Fe3O4-based materials on the microwave absorption and compression properties of GP nanocomposites were comprehensively explored. Owing to the hollow structure and heterointerface formed, GP nanocomposites containing H-Fe3O4-400 displayed outstanding microwave absorption performance with a minimum reflection loss (RLmin) of −39.3 dB at 2.2 mm and an effective absorption bandwidth (EAB) of 4.8 GHz. More importantly, radar cross section (RCS) simulation was conducted to demonstrate the outstanding microwave attenuation capability of H-Fe3O4-400/GP nanocomposites in a real service environment. The results showed that the performance of GP nanocomposites was more competitive than that of other similar microwave absorbing construction materials. Furthermore, the compression tests showed that the introduction of H-Fe3O4-400 decreased the compressive strength of the GP nanocomposites from 37.87 to 31.62 MPa, while the presence of SiO2 enhanced interfacial load transfer, increasing the compressive strength to 37.16 MPa. The overall results validated that the as-prepared GP nanocomposites can be a potential candidate for use in construction areas where microwave absorption is essential.