Increasingly severe electromagnetic pollution is now in urgent need of materials with lightweight, excellent flame retardancy, and outstanding electromagnetic interference shielding effectiveness (EMI SE). Renewable source-derived carbon foams and graphene have attracted extensive attention due to their 3D porous structure and remarkable electrical conductivity (σ). In this work, annealed sugarcane (ASC) was prepared by removal of lignin from sugarcane via hydrothermal reaction, followed by annealing treatment. Then graphene oxide (GO) was filled by vacuum-assisted impregnation process and thermally annealed to obtain the ASC/reduced graphene oxide (rGO) hybrid foams. When the loading of rGO is 17 wt.%, the ASC/rGO hybrid foam (density, ρ of 0.047 g/cm3) exhibits the optimal σ of 6.0 S/cm, EMI SE of 53 dB, specific SE (SSE = SE/ρ)/thickness (t) of 3830 dB·cm2/g, and compressive strength of 1.33 MPa, which is 76%, 36%, 13% and 6% higher than those of ASC, respectively. Moreover, ASC/rGO presents excellent flame retardancy, thermal stability, and heat insulation, which remains constant under burning on an alcohol lamp and presents low thermal conductivity of 115.19 mW(m·K), close to the requirement for heat insulation. Synergistic effect of ASC and rGO not only significantly increase σ of ASC/rGO, but fully utilizes the capability of ASC and rGO to attenuate electromagnetic waves by virtue of unique porous structures and abundant interfaces. Such kind of lightweight EMI materials with excellent mechanical property, shielding performance, flame retardancy, and heat insulation is expected to tackle the key scientific and technical bottleneck problems of EMI materials, and will greatly expand the application of carbon nanomaterials in the field of aerospace industry.
