The Effect of Hydrothermal Temperature and Sample Thickness on the Synthesis of BaFe<sub>12</sub>O<sub>19</sub>@MnO<sub>2</sub> Core-Shell Composites

Abstract

Advances in radar technology today are experiencing rapid development based on the latest findings that complement each other. BaFe12O19 is a type M hexagonal ferrite material as the best candidate for absorber material applications. Manganese dioxide (MnO2) is a transition metal that has a high dielectric loss and has the opportunity to increase the absorption of electromagnetic waves. The BaFe12O19@MnO2 core-shell composite produces the combined characteristics of BaFe12O19 and MnO2, which can improve performance as radar-absorbing material. The BaFe12O19@MnO2 core-shell composite is synthesized in two stages: molten salt synthesis in manufacturing BaFe12O19 as a core and hydrothermal synthesisto grow MnO2 nanoflowers as a shell. The research objective was to produce BaFe12O19@MnO2 core-shell composite for radar absorbing applications in the x-band with absorption of ~99%. In molten salt synthesis, using two calcination operations at 1000 °C for two hours to create BaFe12O19 as a template, then combining BaFe12O19 template with Fe2O3 and BaCl2.2H2O for eight hours at 1100 °C prepared for MnO2 pathways on the BaFe12O19 surface. Hydrothermal synthesis occurs by dissolving BaFe12O19 and KMnO4 in deionized water with a mass ratio of BaFe12O19 to KMnO4 is 1:1, followed by hydrothermal synthesisat a holding time of 12 hours with a temperature of 150 °C; 170 °C; 190 °C. Characterization of vector network analysis on a variation of sample thickness (1; 1.5; 2; 2.5; 3) mm were analyzed in the x-band frequency on 8-12 GHz. BaFe12O19@MnO2 core-shell composite was hydrothermally produced at 170 °C with a particle size of 197.1 nm, a thickness of 2.5 mm, and a reflection loss of -20.31 dB at 8.7 GHz. The absorber material from the combined synthesis of molten salt and hydrothermal synthesis to make BaFe12O19@MnO2 core-shell composite successfully produced microwave absorption up to 99.06%.