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ABSTRACT A molecular dynamics study of the mechanical properties of graphene nanoribbon-embedded gold composites

Graphene, a single sheet of carbon atoms, has recently been isolated from bulk graphite.1 Graphene nanoribbons (GNRs), quasi-one-dimensional nanostructures, and narrow (typically <20 nm) strips of graphene are all promising materials for nanoelectronic applications. An increasing number of studies have focused on graphene’s extraordinary physical, chemical, and mechanical properties.2–4 For example, the electrical mobility and thermal sp2 conductivity of graphene are over an order of magnitude greater than those of silicon.5,6 The high electron mobility of GNRs makes them a promising candidate for the next generation of logic devices.7 GNRs also have potential for use as chemical sensors due to their exceptional sensitivity.8 Graphene is also an attractive material for optical and optoelectrical devices due to its large optical absorptivity and widely tunable band gap.9,10 The ultrahigh thermal conductivity of graphene has been extensively studied both theoretically11,12 and experimentally.13–15 Results show that graphene is an ideal material for thermal (phononic) devices.16,17 The superior mechanical properties of graphene4 make it ideally suited for nanoelectromechanical system (NEMS) applications and as reinforcing fibers in super-strong composites.

Metals have become increasingly used as a matrix material for composites.18,19 Carbon nanotubes (CNTs) have also been considered for such applications. The Young’s modulus of CNT– gold composites is much larger than that of pure gold.18 However, it is virtually impossible to obtain perfect CNTs.

Defects, which influence the physical and mechanical properties, inevitably form during the growth of CNTs. Although a larger volume fraction of defective nanotubes can slightly increase the failure stress of nanocomposites, the failure strain always decreases.20 Many GNR properties are similar to those exhibited by CNTs. The single atomic layer of GNRs, either in aligned or unaligned form, is advantageous for making composite materials. The mechanical properties of GNRs have been extensively studied. However, there is a lack of information on the mechanical properties of GNR composites. To obtain highperformance composite materials, it is important to study the mechanical behaviors of metal-matrix composites with GNRs. The present work reports the mechanical properties of armchair GNR (AGNR) and zigzag GNR (ZGNR) gold composites. Five models are investigated, namely inner AGNR– gold (AGNR/Au) composites, outer AGNR–gold composites, inner ZGNR–gold (ZGNR/Au) composites, outer ZGNR–gold composites, and a single-crystal gold nanosheet, under uniaxial tension using molecular dynamics (MD) simulations. Various temperatures are considered to study the thermal kinetic effect on AGNR/Au and ZGNR/Au composites. The length effects of AGNR/Au and ZGNR/Au composites are also studied. It was found that it is difficult for a perfect sp2 graphene structure to form strong bonds with a metal matrix. Only nonbonded interatomic interaction, i.e., van der Waals energy, is considered at the GNR/Au interface.