Graphene Size-Dependent Multifunctional Properties of Unidirectional Graphene Aerogel/Epoxy Nanocomposites.

Unidirectional graphene aerogels (UGAs) with tunable densities, degrees of alignment, and electrical conductivities are prepared by varying the average size of precursor graphene oxide (GO) sheets between 1.1 and 1596 µm2. UGAs prepared using ultralarge GO (UL-UGA) outperform those made from small GO in these properties. The UL-UGA/epoxy composites prepared by infiltrating liquid epoxy resin into the porous UGA structure exhibit an excellent electrical conductivity of 0.135 S/cm, along with an ultralow percolation threshold of 0.0066 vol %, which is one of the lowest values ever reported for all graphene-based composites. Owing to their three-dimensional interconnected network, a high degree of alignment, and effective reduction, UL-UGAs effectively enhance the fracture toughness of epoxy by 69% at 0.11 vol % graphene content through unique toughening mechanisms, such as crack pinning, crack deflection, interfacial debonding, and graphene rupture. These aerogels and composites can be mass-produced thanks to the facile, scalable, and cost-efficient fabrication process, which will find various multifunctional applications.