Preparation of graphite-like carbon nitride (g-C3N4)/NiCo2S4 nanocomposite toward salient microwave characteristics and evaluation of medium influence on its microwave features

In this paper, NiCo2S4 sulphide spinel nanoparticles are prepared using a modified solvothermal route, after which the obtained siegenite nanoparticles are tailored on graphite-like carbon nitride (g-C3N4) nanosheets. The morphology of tailored nanostructures is accomplished via an ion exchange process. Interestingly, the g-C3N4 stick structures are fabricated based on an innovative approach. Moreover, interfacial polarizations at heterojunction interfaces, and medium effects on microwave characteristics are examined, using polystyrene (PS) and polyvinylidene fluoride (PVDF) as polymeric matrices. The specimens are characterized via Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) analyses. The optical performance of nanostructures is studied by means of diffuse reflection spectroscopy (DRS) analysis, and is suggestive of a narrow band gap for NiCo2S4 and NiCo2S4/g-C3N4 nanostructures. Finally, the material's microwave absorbing features are clarified using a vector network analyzer (VNA) instrument via a wave guide technique. The resulting significant microwave absorptions reveal that our g-C3N4/NiCo2S4/PVDF 40% nanocomposite exhibited seven notches of reflection loss (RL), more than 30 dB in its curve, at 1.75 mm in thickness, while its maximum RL was 59.39 dB at 13.07 GHz. Interestingly, this composite, in a mass fraction of 60%, illustrates an efficient bandwidth of 5.1 GHz (RL > 10 dB) at only 1 mm thickness. It is worth noting that the maximum RL of g-C3N4 stick structures/PVDF measures 74.53 dB at 14.86 GHz, with a broadband efficient bandwidth of 7.96 GHz (RL > 10 dB). More significantly, both g-C3N4/NiCo2S4/PVDF and NiCo2S4/PVDF demonstrated salient electromagnetic interference shielding effectiveness (SE) > 30 dB across both x- and ku-band frequencies.