▎ 摘　　要

An innovative combination of micro-computed X-ray tomography (mu CT) and electron microscopy (SEM) coupled to an image-processing software was used to study the thermal conductivity of graphene nanoplatelets(GNP)/epoxy composites. This approach afforded a precise and systematic analysis of the dispersion state of the fillers in the epoxy matrix. Here, the influence of GNP aspect ratio on thermal conductivity enhancement (TCE) and the relationship between dispersion state of the fillers and TCE is revealed. The aggregation level of GNP was finely tuned by varying the sonication power. An unexpected trend towards enhanced thermal conductivity upon aggregation of the fillers is demonstrated. Moreover, mu CT analysis revealed the encapsulation of micro-voids, undetectable with conventional methods, by large fillers aggregates. This study demonstrates that aggregation of the fillers increases the thermal conductivity of epoxy composites as long as it does not lead to voids encapsulation.