The preparation of super lightweight magnetic Fe3O4/graphene/carbon aerogels and their use in electromagnetic interference shielding

Magnetic Fe3O4/graphene/carbon aerogels were prepared by the sol-gel method, followed by supercritical drying and pyrolysis. The microstructures, electrical properties and electromagnetic interference shielding performance of the aerogels were investigated. The aerogels were crushed into a fine powder with a bimodal particle size distribution (similar to 0.1 and 10 mu m) and released into a chamber to a particle concentration of 1 g m(-3) at room temperature under atmosphere pressure using a dispensing device, where electromagnetic interference shielding was tested. Results indicate that the composite aerogels have high conductivity and a hierarchical pore structure with a density as low as 0.015 g cm(-3). The concentration of the fine powder in the chamber decreased with time and levelled off above 20 min. The shielding is dominated by the particles that are difficult to settle due to their perturbation by air. The shielding for the visible wave band of the composite aerogels in powder form initially and after the release for 30 min are above 99.90% and 98.77%, respectively. Those for 3-5 mu m and 8-12 mu m infrared light are respectively 99.55% and 99.35% initially, and 99.05% and 96.79% after the release for 30 min. For the millimeter wave band, the shielding ratios initially and after the release for 30 min are above 83.68% and 82.54%, respectively.