The Electromagnetic Wave Absorbing Property of Dual-Layer Cement Matrix Composites Based on the Principle of Electromagnetic Energy - Thermal Energy Conversion

Abstract

Based on the application of stealth technology in actual engineering projects, and according to the theory that when electromagnetic waves (EMW) pass through different wave absorbing materials, they will undergo resistance loss, dielectric loss, and magnetic loss, and the electromagnetic energy will be converted into thermal energy, this paper designed and developed a dual-layer EMW-absorbing Cement Matrix Composites (CMC) combining with the principle of impedance matching, and proposed to take cement paste mixed with expanded perlite as the matching layer of the newly developed material, and aggregate and nanomaterials as its wave absorbing layer. The aggregate was prepared by mixing 15wt.% 38μm Fe3O4 powder and 10wt.% 500nm SiC powder into the clay powder to produce cement raw pellets and calcine them at 1190℃, the fabricated aggregate has obvious dielectric loss and magnetic loss to EMW, and its crushing resistance strength can reach 13.7MPa. For the dual-layer test pieces made of the prepared aggregate and 2wt.% Conductive Carbon Black (CCB), within 8-18GHz frequency band, the bandwidth with a reflectivity lower than -10db reached 9.5GHz, the bandwidth with a reflectivity lower than -12db reached 7.55 GHz, and its maximum reflection loss reached -19.56db. In addition, the prepared CMC exhibited good mechanical properties, and its compressive strength reached 50.7MPa at the age of 28d.

Preparation of a novel foamed concrete modified with carbon fiber and graphite:

“…Traditional cement-based materials have a dense structure and poor impedance matching, making it difficult for electromagnetic waves to enter [10]. With low density and low dielectric constant, porous materials such as expanded polystyrene [11,12], hollow glass beads [13], and expanded perlite [14,15] are often incorporated into cement-based materials to improve impedance matching with free space [16,17]. However, foam concrete itself can extend the transmission length of incident waves and simplify the preparation process.…”