Highly conductive multilayer-graphene paper as a flexible lightweight electromagnetic shield

A graphene-based porous paper made of multilayer graphene (MLG) microsheets is developed for application as a flexible electrically conducting shielding material at radio frequency. The production process is based on the thermal expansion of a graphite intercalated compound, the successive liquid-phase exfoliation of the resulting expanded graphite in a proper solvent, and finally the vacuum filtration of the MLG-suspension using a nanoporous alumina membrane. Enhancement of the electrical conductivity and electromagnetic shielding properties of the MLG paper is achieved by gentle annealing at 250 degrees C overnight, and by mechanical compression at 5 MPa. The obtained results show that the developed MLG papers are characterized by an electrical conductivity up to 1443.2 S/cm, porosity around 43%, high flexibility, shielding effectiveness up to 55 dB at 18 GHz with a thickness of 18 mu m. Numerical simulations are performed in order to understand the main factors contributing to the shielding performance of the new material. (C) 2015 Elsevier Ltd. All rights reserved.