High-performance microwave absorption by optimizing hydrothermal synthesis of BaFe12O19@MnO2 core–shell composites

Abstract

Stealth technology advances in radar-absorbing materials (RAMs) continue to grow rapidly. Barium hexaferrite is the best candidate for RAMs applications. Manganese dioxide (MnO₂) is a transition metal with high dielectric loss and can be used as a booster for changing polarization and reducing reflection loss. The advantages of BaFe₁₂O₁₉ and MnO₂ can be combined in a core–shell BaFe₁₂O₁₉@MnO₂ composite to improve the material's performance. MnO₂ composition, temperature, hydrothermal holding time, and sample thickness all have an impact on the core–shell structure. In this study, a core–shell BaFe₁₂O₁₉@MnO₂ composite is synthesized in two stages: molten salt synthesis to produce BaFe₁₂O₁₉ as the core and hydrothermal synthesis to synthesize MnO₂ as the shell. In the hydrothermal synthesis, BaFe₁₂O₁₉ and KMnO₄ were mixed in deionized water using different mass ratios of BaFe₁₂O₁₉ to KMnO₄ (1 : 0.25, 1 : 0.5, 1 : 0.75, and 1 : 1). The main goal of the analysis was to figure out how well the hydrothermal synthesis method worked at different temperatures (140 °C, 160 °C, and 180 °C) and holding times (9 h, 12 h, and 15 h). The composite material was subjected to characterization using a vector network analyzer, specifically at thicknesses of 1.5 mm, 2 mm, 2.5 mm, and 3 mm. The hydrothermal temperature and composition ratio of BaFe₁₂O₁₉ : MnO₂ are the most influential parameters in reducing reflection loss. Accurate control of the parameters makes a BaFe₁₂O₁₉@MnO₂ core–shell composite structure with a lot of sheets. The structure is capable of absorbing 99.99% of electromagnetic waves up to a sample thickness of 1.5 mm. The novelty of this study is its ability to achieve maximal absorptions on a sample with minimal thickness through precise parametric control. This characteristic makes it highly suitable for practical applications, such as performing as an anti-radar coating material. BaFe₁₂O₁₉@MnO₂ demonstrates performance as a reliable electromagnetic wave absorber material with simple fabrication, producing absorption at C and X band frequencies.