Study on preparation and electromagnetic shielding properties of GNs/NaCl/SCF composite carbon foam

Herein, the graphenes/sodium chloride/sucrose composite carbon foam (GNs/NaCl/SCF) was prepared by high pressure pyrolysis and chemical vapor deposition (CVD) It was found that NaCl micron particles played the role of nucleating agent in the foaming process of sucrose based carbon foam, which could effectively tailoring the pore structure of composite carbon foam. When the thickness of GNs/NaCl/SCF is only 3 mm, the total shielding efficiency (SET) of composite carbon foam in the X-band range is up to 49.25 dB, and the absorption loss (SEA) is much greater than the reflection loss (SER). The SET of GNs/NaCl/SCF was 2.8 times higher than that of pure sucrose based carbon foam (SCF). This is due to the unique structure of the composite carbon foam. First, the rich 3D continuous pore cell structure of carbon foam improves the impedance matching degree of electromagnetic wave, so that the electromagnetic wave “trapped” in the pore cell, forming multiple reflection and scattering. Second, under the catalysis of elemental copper, the graphene grown in situ on the pore cell of the carbon foam formed a conductive network, which significantly improved the conductivity of the composite carbon foam. Third, the composite carbon foam has abundant heterogeneous interfaces (such as Cu-GNs, Cu-SCF, GNs-SCF, etc.), which act as the center of polarization of induce dipole polarization to further enhance the electromagnetic shielding performance. Sequentially, the synergistic effect of the above three aspects leads to the significant improvement of the electromagnetic shielding performance of composite carbon foam. [Display omitted] •NaCl played the role of nucleating agent in the foaming process of sucrose.•Growing graphene significantly improves the conductivity of the material.•The SET of material in the X-band range is up to 49.25 dB, and the SEA is much greater than the SER.