Preparation of magnetic three-dimensional porous Co-rGO aerogel for enhanced microwave absorption

Abstract

A good electromagnetic wave (EMW) absorption material should possess both favorable impedance matching and superb EMW absorption performances. Apart from this, the characteristics of lightweight, thin matching thickness, strong absorption and broad bandwidth are required. To achieve this, ultralight Co-rGO aerogel materials were prepared through a series of treatments of hydrothermal, freeze-drying and annealing. Through the addition of pvp and under different annealing temperatures, we investigated the effect of pore structure, pore size and magnetism on the absorbing properties of the materials. The magnetic and porous properties are demonstrated by the Vibrating Sample Magnetometer (VSM) and Brunauer Emmett Teller (BET) N2 adsorption-desorption isotherms, respectively. According to the SEM and TEM images, it can be seen that the Co-MOF microspheres growing onto the reduced graphene oxide (rGO) nanosheets. It is worth noting that the 800Co-rGO-pvp composite shows excellent EMW absorption performances with a low filling content of 4 wt%, which achieves strong absorption of −40.57 dB at a thickness of 2.0 mm and broad effective absorption bandwidth (EAB) of 7.12 GHz at a thickness of 2.5 mm, covering the whole Ku band and a quarter of X band. Moreover, a series of absorption mechanisms are elaborated, such as interfacial polarization, dipolar polarization, conduction loss, magnetic resonance and eddy current loss. All in all, the outstanding EMW absorption performances are attributed to the magnetic three-dimensional porous structure of Co-rGO aerogel.