Fusion TEM holder tip
Image courtesy of J. Phys. D Appl. Phys.

Abstract

Dynamic heating experiments on graphene/Cu nanocomposites by in situ scanning electron microscopy were conducted to observe the evolution of the morphology and size of the Cu nanoparticles. Microstructural characterization showed that the graphene/Cu nanocomposites system consists of graphene sheets decorated with Cu-based nanoparticles with different chemistries (Cu, Cu2O), shapes (cube, rod, triangle, etc) and sizes. Evidence of neck evolution, coalescence, sublimation and Ostwald ripening were observed. Interestingly, some of the events occurred at the edges of the graphene sheets. The quantitative data of necking evolution deviates from the classical continuum theory indicating that intrinsic faceting and the shape of the nanoparticles played an important role in the necking process. This was supported by molecular dynamics simulations. Experimental data of liquid-spherical nanoparticles on graphene suggested that Cu did not wet graphene. Based on sublimation experiments and surface stability, we propose that graphene decorated with Cu nanoparticles enclosed by {1 1 1} facets are the most stable nanocomposite at high temperatures. The growth mechanism of nanoparticles on graphene is discussed.

Impact Statement

Studied the effects of temperature on Cu and Cu2O nanoparticles on graphene sheets using the Fusion system in a Zeiss Auriga SEM system. Imaged and analyzed neck formation, coalescence, sublimation and Ostwald ripening of nanoparticles of sizes
between 20 nm and a few hundred nanometers in diameter. Noted differences in the nanoparticle evolution at particular temperatures. Coalescence of particles occurred with the addition of Ostwald ripening at higher temperatures. It was also noted that the Cu nanoparticles did not wet the surface of the graphene at high temperatures. The authors report that the Cu/graphene nanocomposite may be the most temperature metal/graphene composite system and are relevant for highly sensitive chemical
sensors.