Cement nanocomposite with CoFe2O4 nanoparticles and graphite flakes for microwave absorption in X-band frequency

This study reports the microwave absorption in cementitious composites through the incorporation of graphite flakes (GF) and ultrasonically synthesized spherical cobalt ferrite (CoFe 2 O 4 ) nanoparticles (CF). Composites with 2.5 wt.% GF and 7.5 wt.% CF were prepared and characterized for their structural, magnetic, mechanical, and electromagnetic properties. The phase purity of CF nanoparticles and the presence of fillers in the cement matrix were confirmed by X-ray diffraction (XRD). The morphology, distribution, and interfacial interactions between the fillers and the cement matrix were examined using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Magnetic hysteresis loops revealed a saturation magnetization of 5.8 emu/g for the cement nanocomposite, confirming the retention of some magnetic behaviour of CF in cement matrix. The results demonstrated excellent microwave absorption performance in X-band range, with a minimum reflection loss (RL min ) of -41.9 dB at 10.59 GHz and an effective absorption bandwidth (EAB) of 2.4 GHz (below -10 dB) at a thickness of only 2 mm, corresponding to microwave absorption efficiency of 99.994%. The obtained microwave absorption performance is attributed to the synergistic effects of permittivity and permeability, favourable impedance matching, and high attenuation constant due to the combined dielectric loss from GF and magnetic loss from CF. Despite a slight reduction in mechanical strength compared to the reference, the composite meets standard structural requirements. This work highlights the potential of using conductive and magnetic nanofillers to develop high-performance cementitious composites for X-band microwave absorption applications. • Cement nanocomposite achieves a minimum reflection loss of -41.9 dB at 10.59 GHz. • The sample exhibits a 2.4 GHz effective absorption bandwidth (below -10 dB). • Graphite flakes and CoFe 2 O 4 nanoparticles led to excellent microwave absorption. • Synergistic dielectric-magnetic losses play significant role in microwave absorption.