Effects of the absorber, thickness and surface roughness on the electromagnetic wave absorption characteristics of magnesium phosphate cement

Abstract

Magnesium phosphate cement (MPC) functionalized with excellent electromagnetic wave absorption performance, bonding capacity, fast hardening and early strength can meet the requirements for rapid electromagnetic radiation protection of military and civil building structures. Hollow glass microsphere (HGM) is added uniformly to improve the impedance matching of MPC to free space, so that the electromagnetic wave is able to be maximally introduced into MPC and effectively absorbed by carbon nanotubes (CNT) through high dielectric loss effect. Influences of HGM contents, thickness and surface roughness of specimens on the electromagnetic wave absorption performance of MPC are systematically investigated. Test results demonstrate that the electromagnetic absorption performance of MPC is significantly enhanced by the additions of HGM and CNT. The peak reflection loss and the bandwidth below −10 dB first increase and then decrease with increasing HGM content. Increasing the thickness of the MPC improves the electromagnetic reflection loss. The electromagnetic absorption properties of MPC are improved further by cutting notches. MPC blended with 50 vol% HGM and 1 wt% CNT (by MgO) with 5 mm deep notches spaced 18 mm apart has excellent electromagnetic absorption capacity as featured by a peak reflection loss of –33.5 dB and a bandwidth of 7.03 GHz below −10 dB. In the perspective of structural strengths, the modified MPC is able to repair damaged concrete of pre-fractured concrete. It achieves the dual features of absorbing electromagnetic waves and repairing existing concrete structures.