Graphene enhanced flexible expanded graphite film with high electric, thermal conductivities and EMI shielding at low content

Expanded graphite (EG) films with low oxidation degree exhibit excellent thermal, electric properties and electromagnetic interference (EMI) shielding. However, the mechanical brittleness is the major limitation for their applications. To meet this challenge, in this work, a small amount of flexible graphene (GE) is introduced to endow EG films with good flexibility and mechanical properties by forming simulate shell structure. Moreover, the influence of oxidation degree and sheet thickness for carbon sheets as well as the lateral size of GE on the film performance is carefully discussed. As a result, a 431% enhancement of tensile strength from 7.7 Mpa to 40.9 Mpa and little sacrifice of electric, thermal conductivities up to 1467 S cm(-1) and 348 W m(-1) K-1 are observed with the loading of only 10% large GE (LGE) sheets in EG films. Besides, high EMI shielding of 48.3 dB is achieved as the film thickness reaches 43 mu m. The excellent flexibility of prepared EG/LGE films can be retained even after more than 1000 times of direct folding. These excellent properties of light-weight EG/LGE films, together with their advantages of environmentally friendly and facile large-scale fabrication, endow the films with great potential applications in next-generation commercial portable flexible electronics. (C) 2018 Elsevier Ltd. All rights reserved.