Discrete dual-band absorption in porous BaTiO3@rGO composite aerogel synthesized by freeze-thaw assistance

Carbon-based materials hold significant potential for electromagnetic absorption applications, however, the development of effective discrete dual-band absorbers remains a formidable challenge. In this study, we synthesized BaTiO₃@reduced graphene oxide (BTO@rGO) composite aerogel via ascorbic acid-assisted thermal reduction, enhanced by a freeze-thaw treatment. This treatment induces a bimodal mesoporous structure, with pore size centered at 2.2 nm and 3.9 nm, which significantly boosts the aerogel’s specific surface area of 15.95 m² g⁻¹ . Additionally, the freeze-thaw process enriches the rGO with defect dipoles and reduces the Ba 2 + content on the surface sites. These structural and compositional features synergistically contribute to the composite’s discrete dual-band absorption characteristic. Specifically, the composite achieves minimum reflection loss values of −13.8 dB in the C-band (4.7–5.7 GHz) and −20.7 dB in the Ku-band (15.4–17.6 GHz) at a thickness of 5.0 mm, which aligns well with the quarter-wavelength theory. This innovative structural design strategy, which transforms single-frequency absorbers into dual-frequency absorbers, offers a novel and effective approach for developing advanced dual-frequency absorbing materials.