Flexible graphene-graphene composites of superior thermal and electrical transport properties.

Graphene is known for high thermal and electrical conductivities. In the preparation of neat carbon materials based on graphene, a common approach has been the use of well-exfoliated graphene oxides (GOs) as the precursor, followed by conversion to reduced GOs (rGOs). However, rGOs are more suitable for the targeted high electrical conductivity achievable through percolation but considerably less effective in terms of efficient thermal transport dictated by phonon progression. In this work, neat carbon films were fabricated directly from few-layer graphene sheets, avoiding rGOs completely. These essentially graphene-graphene composites were of a metal-like appearance and mechanically flexible, exhibiting superior thermal and electrical transport properties. The observed thermal and electrical conductivities are higher than 220 W/m · K and 85000 S/m, respectively. Some issues in the further development of these mechanically flexible graphene-graphene nanocomposite materials are discussed and so are the associated opportunities.