Electrically Conductive and Mechanically Strong Graphene/Mullite\nCeramic Composites for High-Performance Electromagnetic Interference\nShielding

Abstract

Ceramic\ncomposites with good electrical conductivity and high strength\nthat can provide electromagnetic interference (EMI) shielding are\nhighly desirable for the applications in harsh environment. In this\nstudy, lightweight, highly conductive, and strong mullite composites\nincorporated with reduced graphene oxide (rGO) are successfully fabricated\nby spark plasma sintering at merely 1200 °C using the core–shell\nstructured γ-Al₂O₃@SiO₂ powder\nas a precursor. The transient viscous sintering induced by the γ-Al₂O₃@SiO₂ precursor not only prohibits\nthe reaction between mullite and rGO by greatly reducing the sintering\ntemperature, but also induces a highly anisotropic structure in the\nrGO/mullite composite, leading to an extremely high in-plane electrical\nconductivity (696 S m^–1 for only 0.89 vol % of rGO)\nand magnitude lower cross-plane electrical conductivity in the composites.\nAs a result, very large loss tangent and EMI shielding effectiveness\n(>32 dB) can be achieved in the whole K band with extremely low\nrGO\nloading (less than 1 vol %), which is beneficial to maintain a good\nmechanical performance in ceramic matrix composites. Accordingly,\nthe rGO/mullite composites show greatly improved strength and toughness\nwhen the rGO content is not high, which enables them to be applied\nas highly efficient EMI shielding materials while providing excellent\nmechanical performance.