Graphene‐infused copper: A flash‐induced far‐from‐equilibrium phase transformation

Abstract The flash phenomenon, first discovered in the context of sintering, has grown broadly into many areas of science and technology. It enables the synthesis of materials that are far from equilibrium. Flash is characterized by massive generation of defects, up to 25 mol% within the crystal lattice, astronomical rates of solid‐state diffusion, electronic conductivity in nominally insulating ceramics, solid‐state plasmas, and electroluminescence. In this work, we show that ordinary carbon deposited on the surface of a copper wire permeates throughout it, while at the same time, transforming into a network of graphene. Graphene is confirmed by Raman spectroscopy. Networks of carbon are imaged by atom probe tomography and scanning transmission electron microscopy. The network suppresses creep at high temperature (900°C). The graphene network forces the wire to retain its shape when its temperature is raised above the melting point of copper. The benchmark for copper conductivity is 58.1 MS m ‒1 or 100% international annealed copper standard (IACS). The conductivity of this graphene‐infused copper is 105%‒110% IACS, greatly exceeding the 102% IACS first reported by Scherer who introduced graphene into molten copper containing carbon by passing current. The flash experiment is carried out in the solid state by injecting current into copper and increasing it at a constant rate (without a furnace). The transformation is completed in a few seconds. Thermodynamically, carbon is barely miscible in copper (approximately 9 ppm). Here, mole fractions of 0.11% are achieved. Therefore, these results demonstrate the far‐from‐equilibrium nature of the process. The question of the electronic structure of the high‐conductivity graphene‒copper interface is highlighted.