Sp2 carbon embedded in Al-6061 and Al-7075 alloys in the form of crystalline graphene nanoribbons

Electrocharging assisted process has been used to incorporate carbon in Aluminum 6061 and 7075 alloys ensuing significant improvements of the ultimate tensile strength, hardness, and electrical conductivity. This work investigates the presence of carbon, its structure, carbon-metal bonding, surface characterization and dispersion of carbon incorporated in Al alloys by electrocharging assisted process. Networks of Graphene nanoribbons with 3D epitaxy and preferred orientation along the < 110 > and < 112 > directions of Al are evident by transmission electron microscopy and spectrum imaging of the C-K edge electron energy loss spectra. X-ray photoelectron spectroscopy and Raman scattering corroborate sp(2) carbon in Al-6061, and hybrid sp(2)-sp(3) in Al-7075 with added carbon. Kelvin probe force microscopy substantiates the presence of carbon in the Al matrix. Phonon density of states derived from first-principles calculations predicts C-Al Raman active modes whilst density functional theory indicates covalent bonding between carbon and Al. This method of incorporation of graphene nanostructures in metals with strong carbon-metal bonding can open up new avenues for incorporation of sp(2) carbon structures in other materials. (C) 2016 Elsevier Ltd. All rights reserved.