Graphene-reinforced carbon composite foams with improved strength and EMI shielding from sucrose and graphene oxide

Graphene-reinforced carbon composite foams were prepared by thermo-foaming of graphene oxide (GO) dispersions in molten sucrose to form solid organic foams followed by carbonization at 900 °C. The hydrogen bonding interactions between sucrose hydroxyls and functional groups on GO decreased the melting point of sucrose from 185 to 120 °C when the GO concentration increased from 0 to 1.25 wt%. The viscosity of GO dispersions in molten sucrose increased gradually with an increase in GO concentration up to 0.75 wt% and then rapidly up to 1.25 wt%. The foaming time and foam setting time decreased drastically from 6 to 1 h and 34 to 9 h, respectively, when the GO concentration increased from 0.15 to 1.25 wt% due to the catalytic effect of GO toward –OH to –OH condensation. The density and cell size of the carbon composite foams depended on the GO concentration. A maximum compressive strength and specific compressive strength of 5.2 MPa and 21.3 MPa g⁻¹ cm⁻³, respectively, achieved at a very low GO concentration of 0.25 wt% corresponded to an increase of 189 and 133 %. The electrical conductivity and EMI shielding effectiveness (SE) of the graphene-reinforced carbon composite foams increased with an increase in the GO concentration up to 0.15 wt% and then decreased. The decrease was due to a decrease in foam density and GO agglomeration at higher GO concentrations. The maximum SE and specific SE of 38.6 dB and 160 dB g⁻¹ cm⁻³ were achieved at GO concentrations of 0.15 and 1 wt%, respectively.