Low percolation threshold in highly conducting graphene nanoplatelets/glass composite coatings

Thermal sprayed thick glass coatings with a small percentage of multilayer graphene nanoplatelets (GNP) demonstrate electrical functionality with a quite remarkable low percolation limit (1.18 vol.%). This low critical content and the high electrical conductivity (similar to 40 S m(-1)) observed for the in-plane direction are related to the peculiar coating microstructure, formed by the pileup of lamellar amorphous particles decorated by GNP mostly following a surface parallel orientation. The general effective media model fitting to the electrical conductivity data for these coatings suggests a 3D connectivity of graphene and estimates an upper limit conductivity for the GNP of 10(5) S m(-1). Hall effect shows the n-type behavior intrinsic to the SiO2/graphene interface, and carrier density and mobility rising with the GNP content. In addition, the coatings evidence a very high solar absorptivity that jointly with their high electrical conductivity broadens their potential applications, among others, for electromagnetic interference shielding or as photothermal detector and solar absorber for solar steam generation and water desalination. (C) 2018 Elsevier Ltd. All rights reserved.