Carbonized foams from graphene/phenolic resin composite aerogels for superior electromagnetic wave absorbers

Ultralight graphene/phenolic resin composite aerogels (GPFs) were prepared through the chemical reduction and self-assembly of graphene oxide (GO) in water-soluble phenolic resin, followed by a freeze-drying process; carbonized foams (GPFs(T)) were obtained by the subsequent heat treatment of GPFs at a relatively low temperature (500-700 degrees C). Although GPFs do not show the qualified reflection loss value of below -10dB, GPFs(T) achieve the greatly enhanced electromagnetic-wave absorbing performance. Specifically, the minimum reflection loss value of GPF1 (500) reaches -22.7 dB at 14.4 GHz with the absorber thickness of 2.0 mm and the effective absorption bandwidth is up to 5.4 GHz (12.4-17.8 GHz). The evolution of electromagnetic-wave absorbing properties from GPFs to GPFs(T) at different temperatures related with different graphene content is explored. GPFs(T) are expected to exhibit high thermal stability and excellent corrosion resistance property, and especially still maintain ultralight nature (e.g the density of GPF1 (500) is only 24.3 mg/cm3). Most importantly, little graphene (as low as 7.5 wt% of GO addition for GPF1(T)) in GPFs(T) guarantees the facile formation of threedimension (3D) skeleton network and greatly cut downs the carbonization temperature of phenolic resin to achieve the required electromagnetic-wave energy losing ability. The present work provides an effective method to fabricate an ultralight material with exceptional performances including the good electromagnetic-wave absorbing property and the high stability.

Automated summary

The study focuses on the preparation of ultralight graphene/phenolic resin composite aerogels (GPFs) through the reduction and self-assembly of graphene oxide in water-soluble phenolic resin, followed by freeze-drying and low-temperature heat treatment to obtain carbonized foams (GPFs(T)). The GPFs(T) show greatly enhanced electromagnetic-wave absorbing performance compared to GPFs, with little graphene content ensuring the formation of threedimension (3D) skeleton network and reducing the carbonization temperature of phenolic resin. This work provides an effective method to fabricate ultralight materials with good electromagnetic-wave absorbing properties and high stability.