Ultralight CoNi/rGO aerogels toward excellent microwave absorption at ultrathin thickness

Ultrathin thickness (<1 mm) and ultralow density (<10 mg cm(-3)) are urgent challenges for microwave absorption materials. In this manuscript, we tackle these problems by developing a novel CoNi/reduced graphene oxide (rGO) aerogel absorbent via a facile in situ solvothermal and carbonization process. The resultant CoNi/rGO aerogel with an ultralow density of 7 mg cm(-3) exhibited a hierarchical porous structure and a high surface area, in which CoNi nanospheres with a diameter of about 50-80 nm were evenly decorated onto the surface of the rGO aerogel matrix. Benefitting from these attributes, the CoNi/rGO aerogel exhibited an excellent microwave absorption performance. The minimum RL value of -53.3 dB was achieved with an ultrathin thickness of 0.8 mm at a low filler loading of 7 wt% in the paraffin template, and the effective absorption bandwidth was >3.5 GHz. The investigation of the absorption mechanism revealed that moderate dielectric loss, magnetic loss, good impedance matching and the porous structure contributed to the high microwave absorption. This work opens up a potential strategy to prepare excellent microwave absorbents with ultrathin thickness and ultralow density.