Design and preparation of double-layer iron ore tailings cement-based electromagnetic wave absorbing materials containing carbon black and steel fiber

Double-layer iron ore tailings (IOTs) cement-based electromagnetic wave (EMW) absorbing materials with carbon black (CB) and steel fiber (SF) were designed, fabricated, and used as composite absorbers, including matching and absorbing layers. The effects of IOTs, CB, and SF on the mechanical properties and electrical conductivity of cement mortar are studied. The EMW absorbing properties and mechanism allowing IOTs cement mortar to cooperate with CB and SF are also examined in terms of loss attenuation and impedance-matching characteristics. Based on the design of a single-layer structure, the optimal mix proportion and layer thickness for the double-layer structure are determined by following the principle of gradual impedance design. The results showed that the EMW absorbing properties were significantly influenced by loss attenuation and impedance matching. When the thickness of the single-layer structure was 10 mm, the minimum reflection loss (RL) reached −25.73 dB with an effective bandwidth of 0.39 GHz. In contrast, the double-layer structure exhibited excellent broadband. When the thickness of the matching layer was 5 mm and those of the absorption layer was 5 mm and 10 mm, the minimum RL of the double-layer structure reached −38.38 dB and −26.51 dB, with ultra-high effective bandwidths of 2.15 GHz and 2.29 GHz, respectively. Thus, double-layer EMW absorbing materials have excellent absorbing properties and exhibit considerable design flexibility and diversity, and may be considered suitable candidates for preparing promising EMW cement-based materials.