▎ 摘　　要

Fabrication of lightweight graphene/graphite fibers (GFs) with high thermal and electrical conductivity, and good mechanical properties via facile processing method is yet a challenge for industries. The common fabrication of reduced graphene oxide fibers originated from graphite, requires several cost-intensive steps of oxidation and reduction and still, exceptional thermal and electrical conductivity and stiffness of the graphene sheet as a single layer, has not been translated in such fibers. We report the fabrication of ultralight graphene/graphite fibers with the density of 0.25 g/cm(3), and an exceptional thermal and electrical conductivity of 2x10(3) W/K-m and 2x10(5) S/m, respectively as well as impressive mechanical properties of similar to 0.5 GPa strength and 40 GPa Young's modulus via entirely water based process, from achieving exfoliation of graphite through assembling into fibers. Furthermore, the resulting ultralight high performance GFs have been incorporated into epoxy resin, producing self-floating, lightweight composites with enhanced electrical and mechanical properties. (C) 2020 Elsevier Ltd. All rights reserved.