A controllable foaming approach for the fabrication of “rattan-like” graphene-based composite aerogel with desirable microwave absorption capacity

As a common environmental pollutant, microwave can cause great harms to human health. The development of high-performance microwave absorber with lightweight is indeed necessary. Herein, "rattan-like" graphene-based composite aerogels, having macroscopic pores surrounded by plenty of small pores, were designed and fabricated via an in-situ foaming then carbonized approach. Firstly, graphene oxide (GO), nanocellulose and ferrous ions were integrated into an aerogel with uniform large pores via a freeze-casting method. Then, the aerogel was immersed into a H2O2 solution, during which bubble clusters generated in situ. These bubbles were driven into the stacked GO sheets and formed small pores. With the increase of the H2O2 concentration from 0.5 to 10 wt%, the count percentage of the small pores in the aerogel increased from 81.5 to 95.2%. After the final carbonization, the graphene sheets were dually interconnected with magnetic nanoparticles and carbonized nanocellulose. The unique porous structure and dual-connected networks endowed the aerogel with enhanced conductive loss and optimized impedance matching capacity, and thus an excellent microwave absorption performance, whose maximum reflection loss achieves −68.5 dB. Further, the aerogel also exhibited superior sound absorption performance (noise reduction coefficient up to 0.91 in 1000–6300 Hz), and good mechanical stability.