Synthesis of nanoparticles of Fe, Co, and Ni oxides derived of metal–organic framework (MOF), and their combination with carbonyl iron for application in the K-band of frequencies as a microwave-absorbing material

Abstract This work introduces an innovative synthesis of α-Fe 2 O 3 (Fe), Co 3 O 4 (Co), and NiO (Ni) nanoparticles based in the following metal–organic frameworks (MOFs): Fe-MOF, Co-MOF, and Ni-MOF, respectively. These nanoparticles were combined with carbonyl iron (CI) via solid-state synthesis for use as microwave-absorbing materials (MAMs) in the K-band particularly within the 24–26 GHz frequency range. The synthesized materials were characterized structurally by X-ray diffraction (XRD), morphologically by scan electronic microscopy (SEM), and elemental qualitatively the composition by electron dispersive spectroscopy (EDS). The electromagnetic (EM) characterization was performed using a vector network analyzer (VNA) with Keysight ® software to extract the complex relative electric permittivity, and complex magnetic permeability via the Nicholson Ross Weir (NRW) method based on measured S-parameters. Additionally, reflectivity-based EM simulations were conducted to assess impedance matching and determine optimal absorb thicknesses. The results indicate that each synthetized material exhibits distinct electromagnetic behavior, and the proper combination of composition and thickness can yield promising MAM composite. Notably, the combination between nano Fe/ CI achieved a reflection loss lower than −15 dB at a thickness of 1.20 mm, while Co/CI and Ni/CI exhibited superior performance, with minimum reflection loss of −23,45 dB and −26,21 dB respectively. This work provides a novel approach to developing advanced composites for K-band microwave absorption, addressing the growing demand for effective EM pollution.