Synthesis and development of Fe3O4-expanded graphite embedded cement nanocomposites as excellent X-band microwave absorber

In the present work, novel Fe₃O₄-expanded graphite-white cement composites of different wt.% ratios (5%, 10%, 20%, 30% and 40%) were prepared as viable microwave absorbers in the frequency range (8.2–12.4) GHz. Initially, the synthesized Fe₃O₄ and expanded graphite (EG) were characterized by XRD and SEM studies confirming mean particle size of Fe₃O₄ ~ 26.41 nm and loose and spongy structure of EG flakes providing elevated surface area. Microwave absorption’s constitutive parameters viz. complex permittivity (\({\varepsilon }_{r}\)) and permeability (\({\mu }_{r}\)) measured using Nicolson Ross method showed increasing trend with higher Fe₃O₄ -EG wt.%. Based on transmission line theory, optimized single-layer absorber designs were fabricated for microwave absorption evaluation. The reflection loss (RL_m) was measured to be approximately − 25 dB at 10.8 GHz and − 36 dB at 11.8 GHz for composites with 5 wt.% and 20 wt.% loading, respectively. Further, geometrically modified perforated structure of triangular lattice pattern in the composites was proposed for broad absorption bandwidth.