Excellent microwave absorbing performance of biomass-derived activated carbon decorated with in situ-grown CoFe2O4 nanoparticles

Abstract

In this study, in situ-grown cobalt ferrite (CoFe₂O₄, CF) nanoparticles on waste biomass-derived porous activated carbon (AC) were grown via a facile hydrothermal technique to develop a CF/AC nanocomposite. The nanostructure and porous morphology of the nanocomposite were confirmed by FESEM, HRTEM and BET analysis. Microwave (MW) absorption analysis in the range of 2–18 GHz revealed a drastic improvement in the MW absorption performance of the CF/AC nanocomposite. Sample FAC20, having an AC loading of 20 wt%, exhibited excellent maximum reflection loss (RL_max) of −61.86 dB (@16.08 GHz) and an effective absorption bandwidth (RL < −10 dB) of 4.02 GHz at a thickness of 1.56 mm. In contrast, sample FAC30 (@30 wt% AC loading) at 1.9 mm thickness exhibited a maximum effective absorption bandwidth of 4.47 GHz in the K_u band. This remarkable MW absorption performance originates from the combination of AC and CF, which results in high impedance matching followed by sufficient attenuation of microwaves. The presence of multiple interfaces and the complicated porous structure improved the interfacial polarisation, dielectric polarisation and magnetic loss ability of the CF/AC composite. Thus, the present investigation presents the CF/AC composite as an excellent biomass-based nanocomposite for MW absorption applications.