Microwave Absorbing Mortar Using Magnetic Hollow Fly Ash Microspheres/Fe3O4 Composite as Absorbent

A new type of microwave absorption cement-based material was prepared by using a magnetic hollow fly ash microspheres (HFAM)/Fe3O4 composite as the absorbent. Through the chemical precipitation method, a nano-Fe3O4 layer was coated on the surface of HFAM to obtain the HFAM/Fe3O4 composite. Then the composite was added into mortar to prepare microwave absorption cement-based material. The mineral components, micromorphology, and electromagnetic parameters of the HFAM/Fe3O4 composite and the reflection loss of the cement-based material were investigated. It was found that the HFAM/Fe3O4 composite had superparamagnetism, and its saturation magnetization and the residual magnetization were 32.67emu/g and almost zero, respectively. The best microwave absorption of the cement-based material was obtained at 3% HFAM/Fe3O4 composite to cement, of which the bandwidth of the reflection loss lower than -10dB (responding to 90% microwave absorption) was nearing 8GHz, showing excellent microwave absorption performance.