Optimization of multicomponent microwave absorbents for improved electromagnetic wave absorption of layered foamed cementitious materials

Abstract

The integrated design of materials and structures is essential for achieving superior electromagnetic wave absorption performance (EWAP) in cementitious materials. In this study, multicomponent microwave absorbents are designed to improve the EWAP of foamed cementitious materials. The effects of the type, content, and single/compound doping of the absorbents and material density on the EWAP of multilayer foamed cementitious materials are tested. The experimental results show that the multilayer structure can enhance the impedance-matching characteristics between cementitious materials and air. It also conduces more electromagnetic waves to penetrate deeper into the cementitious materials to be absorbed. The electromagnetic dissipation of cementitious materials can be significantly improved by combining the effects of interlayer reflection scattering, interface polarization, and resonance. Furthermore, the multilayer structure offers flexibility in adjusting the type and content of the absorbent in each layer and endows each layer with different electromagnetic dissipation mechanisms, resulting in a significantly improved EWAP. For four layers of foamed cementitious materials, the EWAP is optimized using three different iron ores (WMHL-135: 10 wt% magnetite, 30 wt% hematite, and 50 wt% limonite) in the absorbing layers. It achieves the optimum EWAP with a full-band effective absorption bandwidth of reflection loss (RL) < -10 dB, in the frequency range of 2–18 GHz, a minimum RL of −37.0 dB, and an average RL of –23.4 dB.