Investigation on Microwave Absorbing Properties of Double-Layer Cementitious Composites

Abstract

Double-layer cementitious plates with absorbing microwave properties were designed, based on the impedance matching theory and electromagnetic wave propagation laws. The reflectivity of cementitious composites was measured in the frequency ranges from 8 GHz to 18GHz, and the influence of silica fume on the impedance of the composites surface was studied. Meanwhile, absorbing properties of cementitious plates, which used ferrite and carbon fiber composited ferrite as microwave absorbers, were also investigated respectively. It is shown that the addition of silica fume can improve the impedance matching between the cementitious composites and free space. Compared with the single-layer structure, the reflectivity of the double-layer cementitious plates decreased around 6 dB ~ 8 dB. The maximum reflection loss of double-layer cementitious plate employing carbon fiber and ferrite reached -16.2dB, while the absorption bandwidth under – 10 dB was from 9.6 to 18 GHz.

A Systematic Review of HPM Energy Absorbers for Building Applications

“…As part of study [69], double-layer cementitious tiles that absorb microwaves were designed based on the theory of impedance matching and the law of electromagnetic wave propagation. Ferrite and carbon fibers were used as an admixture to improve the absorptive properties and band width.…”

“…Another group of building materials are small-sized elements in the form of bricks and hollow masonry units. The authors of the articles dealing with such elements with respect to protection against EM radiation proposed the use of, i.a., a mill scale admixture in the manufacture of ceramic bricks with enhanced shielding effectiveness [67], a metallurgical slag addition to ceramic elements [68] and a ferrite and carbon fiber addition to double-layer cementitious tiles [69].…”

In situ formation of Fe3O4/N-doped carbon coating on the surface of carbon fiber with improved electromagnetic wave-absorption property

“…Many studies 11,12,17 have shown that the resistivity of CF is only (0.8-1.8) Â 10 À3 U cm because of its high graphitization degree and special graphite microcrystalline stacking structure. In accordance with the skin effect, 18,19 the complex permittivity of CFs is usually regulated using carbonaceous material coatings, where their conductivity can be controlled, 20,21 leading to reduction in complex permittivity and enhancement of wave impedance. In Zhou's study, 20 silicon carbide nanobers were in situ grown on the surface of CF by catalytic chemical vapor deposition.…”