Microwave absorbing properties of double-layer cementitious composites containing Mn-Zn ferrite

Double-layer cementitious composites filled with Mn-Zn ferrite as microwave absorbers were designed based on the impedance matching theory and electromagnetic wave propagation laws. The results showed that the addition of silica fume can improve the impedance matching between the cementitious composites and free space. Comparing with the single-layer structure, the reflectivity of the double-layer cementitious plates can decrease by 6-8 dB and decrease by 15 dB maximum with 30 wt.% ferrite; in addition, the reflectivity of electromagnetic wave is lower than 10 dB in the frequency range of 11.4-18 GHz. These composites can be potentially used as electromagnetic interference (EMI) materials for buildings. (C) 2010 Elsevier Ltd. All rights reserved.