In this paper, we report the preparation of magnetite nanoparticles combined with polyaniline and activated carbon. The results of the X-Ray diffraction data analysis showed that the samples had a magnetite crystal phase without other phases. The existence of polyaniline and activated carbon was confirmed using Fourier transform infrared spectroscopy characterization shown by the presence of S=O, C-N, and C-C. The sample of synthesis results in this work had the band gap of 3.23 eV. Moreover, the results of data analysis using vector network analyzer revealed the maximum reflection loss value of -14 with the absorbance of 50%. Thereby, the synthesis optimization needs to be done to increase the sample absorbance to the radar wave.

In this work, the Fe3O4 nanoparticles from natural iron sand were combined with active carbon (AC) and polyaniline (PANI) to obtain Fe3O4/AC/PANI nanocomposites with mass variations of the AC of 0.1, 0.2, 0.3, 0.4, and 0.5 g. The crystalline phase of Fe3O4/AC/PANI nanocomposites formed from Fe3O4 with PANI having an amorphous phase. Meanwhile, the crystalline phase of AC was unmatched because of its very small composition. The presence of AC was observed through vibrations from the CC and COOH functional groups. The existence of PANI was indicated by the vibrations of the benzoic ring and quinonoid bonds. Besides, the presence of Fe3O4 was confirmed by the presence of Fe-O functional groups from octahedral and tetrahedral positions. The optical properties of Fe3O4/AC/PANI nanocomposites were shown by increasing the energy gap along with decreasing absorption wavelength. Interestingly, increasing AC composition made the absorption bandwidth of the Fe3O4/AC/PANI nanocomposites wider, so that the radar absorption also increased marking by the greater reflection loss that reached-15.8 dB. The increase in the radar absorption performance of Fe3O4/AC/PANI nanocomposites came from the efficient complementarity between dielectric loss and magnetic loss and interfacial polarization between Fe3O4-AC or between Fe3O4-PANI.