A review of covetics - current understanding and future perspectives

Covetics are a novel class of metal-carbon composites traditionally fabricated in an induction furnace with high power electrical current in the liquid metal-carbon mixture. The electrical current facilitates chemical conversion of carbon feedstock into graphene-metal crystalline structures. We explore the synthesis mechanism and hypothesize that carbon-metal species, rather than purely-carbon ions, are the reactant species driving the covetic reaction. Experimental mechanical and electrical property characterization in aluminum, silver, and copper covetics demonstrates improved tensile, hardness, and conductivity of covetic metals over pure metal controls. The literature proves that significantly improved material properties are possible with homogeneously distributed graphitic carbon in metal. High resolution transmission electron microscopy shows stripe, multidirectional, and alternating carbon-metal plane lattice structure nanocarbon patterns for aluminum, copper, and silver covetics, respectively, as well as high- and low-carbon concentration regions. Covetic Raman spectra and theoretical calculations indicate characteristic graphene signatures and the possibility of aluminum-graphene and silver-graphene bonding. This review consolidates the current literature and provides new avenues for research.