Multifunctional Bicontinuous Composite Foams with Ultralow Percolation Thresholds

Integrating
ultralight weight and strong mechanical performance into cellular
monolith is a challenge unresolved yet. Here, we propose a skeleton-assisted
self-assembly method to design ultralight bicontinuous composite foams
(BCCFs) with high mechanical robustness and ultralow percolation thresholds.
Polymer foam was employed as the skeleton to support assembled graphene
networks, forming BCCFs with a high tensile strength (∼80 kPa)
and breakage elongation (>22.2%). The paraffin and poly­(dimethylsiloxane)
infiltrated BCCFs show a record low percolation threshold of 0.006
vol % and a relatively high electrical conductivity of 0.81 S m–1 at a low graphene content of 0.216 vol %. The BCCFs
demonstrate high and adjustable microwave-absorbing (MA) properties.
The effective absorption bandwidth (reflection loss ≤ −10
dB) for BCCFs with a low graphene loading of 3.4 mg cm–3 achieves 9.0 GHz at a thickness of 4 mm, and it further covers 13.6
GHz considering the adjustability of preferred absorption band. The
BCCFs with an extremely low graphene load of 0.14 mg cm–3 were further used for durable and efficient oil adsorption, which
can adsorb >60 times their own weight. The facile fabrication of
bicontinuous composite foams opens the avenue for practical applications
of high-strength, multifunctional, and productive graphene-based foams.