Abstract
Wrinkles as intrinsic topological feature have been expected to affect the electrical and mechanical properties of atomically thin graphene. Molecular dynamics simulations are adopted to investigate the wrinkling characteristics in hydrogenated graphene annulus under circular shearing at the inner edge. The amplitude of wrinkles induced by in-plane rotation around the inner edge is sensitive to hydrogenation, and increases quadratically with hydrogen coverage. The effect of hydrogenation on mechanical properties is investigated by calculating the torque capability of annular graphene with varying hydrogen coverage and inner radius. Hydrogenation-enhanced wrinkles cause the aggregation of carbon atoms towards the inner edge and contribute to the critical torque strength of annulus. Based on detailed stress distribution contours, a shear-to-tension conversion mechanism is proposed for the contribution of wrinkles on torque capacity. As a result, the graphane annulus anomalously has similar torque capacity to pristine graphene annulus. The competition between hydrogenation caused bond strength deterioration and wrinkling induced local stress state conversion leads to a U-shaped evolution of torque strength relative to the increase of hydrogen coverage from 0 to 100%. Such hydrogenation tailored topological and mechanical characteristics provides an innovative mean to develop novel graphene-based devices.
Highlights
The gray domains represents the inner and outer boundaries which are not plotted in other figures for clarity. (b) The equilibrated wrinkled patterns around the inner rim at the onset of failure ∆θc = 13o. (c) The failure mode of the hydrogenated annulus at ∆θ = 14o. (d–f) The wrinkle configurations of annulus with different hydrogen coverage H-coverage= 0, 50%, 100% at critical rotation angle ∆θc
Annular graphene as a popular structures in nanoelectronics[29], is susceptible to wrinkling under circular shearing
Molecular dynamics and continuum mechanics have been applied to study the wrinkle characteristics and its effect on surface area of graphene[30] The unusual wrinkles in annular graphene can be exploited for applications in nano-force sensors, tunable magnetic or electronic devices, as well as patterned stretchable electronics[31] the applications of graphene always involve surface functionalization for specific optimized properties, while limited knowledge is available about the effect of surface characterization on wrinkling as well as torque capacity of annular graphene
Summary
(Refer to Videos S5 for the dynamics simulation process of graphene annulus with H = 0 %, 10%, 50% and 100%, Figure S4 shows the corresponding snapshots of wrinkle configurations) Figs 3 and 4 show the evolution of wrinkle characteristics and torque capacity as a function of hydrogen coverage, and shows similarity to the results of the fully relaxed boundary conditions. Such similarity demonstrates the generality of the tunable effects of hydrogenation on graphene annulus. Our results demonstrate that the topological and mechanical characteristics of graphene annulus can be tailored with hydrogenation, the conclusions opens up a straightforward means to develop novel graphene -based devices
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