Novel Preparation of Graphene Foam with Adjustable Dielectric Properties for Efficient Microwave Absorption

Graphene foams (GFs) prepared via a hydrothermalmethod can be vacuum-dried directly without the need for freezingby adding naphthalene to the graphene hydrogels. By optimizing theGF preparation process, it is also possible to adjust the GF'sdielectric properties by varying the amount of naphthalene added.Based on the comparison results, it was observed that controllingthe addition of naphthalene could also modify the internal structureof GF and effectively regulate its dielectric properties. GF-80, synthesizedwith 80 g of naphthalene, exhibited exceptional microwave absorption(MA) performance. At a mass content of only 2% and a matching thicknessof 3.38 mm, a minimum reflection loss (RLmin) of -55.89 dBwas achieved. Moreover, GF-80, with a thickness of 2.31 mm, was shownto achieve a bandwidth of RL less than -10 dB across 6.88 GHz.