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The incorporation of carbon nanostructures into Al alloys has the potential to further improve the mechanical and electrical properties of these alloys. We report a novel one-step fabrication method of incorporating carbon in aluminum alloys by the application of a high electric current to molten Al metal containing particles of activated carbon at high temperature and under Ar atmosphere. We propose that the mechanism for carbon incorporation is similar to electromigration where the current facilitates ionization of the carbon atoms followed by polymerization of the carbon structures and the formation of graphitic chains and ribbons along preferred directions of the Al lattice. Furthermore, the current induces transformation from amorphous carbon to crystalline graphitic structures that propagate in the metal matrix. The carbon is identified by the C-K edge in electron energy loss spectra, X-ray photoelectron spectroscopy, Raman and Kelvin probe force microscopy. The stiffness is increased in these samples; hardness, on the other hand, decreases for some samples compared to reference Al alloys with no carbon. The electrical conductivity is superior to that of Al-carbon nanotube composites previously reported. The enhanced properties of Al covetics show potential for naval and aerospace applications and power transmission lines.

Copper-nanocarbon, called covetic, films made using pulsed laser deposition (PLD) from a target containing nominally 4 wt% carbon in the copper matrix show uniform integration of up to 4.1 ± 0.2 wt.% C. We observe evidence of s p 2 carbon in PLD Cu covetic films in XPS and a peak in the C K-edge in electron energy loss spectroscopy indicative of transitions from the 1s to π * anti-bonding unoccupied state, suggesting that the C incorporated in the film is graphitic in nature. We measure sheet resistance of 1.7 Ohm/sq and transmittance of 25% at 550 nm in a ≈ 27 nm thick PLD Cu covetic film after deposition. These films also show much reduced oxidation by scanning probe techniques and very stable resistance for over 120 days - significantly longer than e-beam films of the same thickness. Cu covetic films made by PLD show good promise as transparent electrodes.

Electrocharging assisted process is a method for the incorporation of carbon in molten metals under high electric current which results in the formation of networks of carbon nanostructures inside the metal matrix, and gives the new material improved mechanical, electrical and thermal properties. Alloys produced with this method are called covetics. In our previous works, different characterization techniques such X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) confirmed the presence of sp2 crystalline graphene nanoribbons and sheets in Ag and Al-covetic samples. Here, we report on detailed Raman mapping and characterization of Al-6061, Al-7075 and Ag covetics to further investigate the fraction of sp2/sp3 bonding, strain, defects, degree of oxidation, and crystalline sizes of the graphene nanoribbons. Gradual changes of strain are observed in regions with sp2 bonding and some degree of amorphous carbon is revealed by Raman scattering. Different degrees of oxidation of the carbon nanostructures with mostly sp2 bonding are evident by EELS spectrum imaging. Atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) also reveal the presence of graphene ribbons and sheets with different lengths and conductivity.

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.

We describe a novel approach for coupling pristine graphene with superparamagnetic iron oxide nanoparticles to create dispersed, magnetically responsive hybrids. The magnetic iron oxide (Fe3O4) nanoparticles are synthesized by a co-precipitation method using ferric (Fe3+) and ferrous (Fe2+) salts and then grafted with polyvinylpyrrolidone (PVP). These PVP-grafted Fe3O4 nanoparticles are then used to stabilize colloidal graphene in water. The PVP branches non-covalently attach to the surface of the pristine graphene sheets without functionalization or defect creation. These Fe3O4–graphene hybrids are stable against aggregation and are highly responsive to external magnetic fields. These hybrids can be freeze-dried to a powder or magnetically separated from solution and still easily redisperse while retaining magnetic functionality. At all stages of synthesis, the Fe3O4–graphene hybrids display no coercivity after being brought to magnetic saturation, confirming superparamagnetic properties. Microscopy and light scattering data confirm the presence of pristine graphene sheets decorated with Fe3O4 nanoparticles. These materials show promise for multifunctional polymer composites as well as biomedical applications and environmental remediation.