Mechanical properties of hydrogen functionalized graphene allotropes

Abstract

Molecular dynamics (MD) simulations have been performed to investigate the mechanical properties of hydrogen functionalized graphene allotropes (GAs) for H-coverage spanning the entire range (0-100%). Four allotropes (graphyne, cyclic graphene, octagonal graphene, and biphenylene) with larger unit lattice size than graphene are considered. The effect of the degree of functionalization and molecular structure on the Young's modulus and strength are investigated, and the failure processes of some new GAs are reported for the first time. We show that the mechanical properties of the hydrogenated GAs deteriorate drastically with increasing Hcoverage within the sensitive threshold, beyond which the mechanical properties remain insensitive to the increase in H-coverage. This drastic deterioration arises both from the conversion of sp 2 to sp 3 bonding and easy rotation of unsupported sp 3 bonds. Allotropes with different lattice structures correspond to different sensitive thresholds. The Young's moduli deterioration of fully hydrogenated allotropes can be up to 70% smaller than that of the corresponding pristine structure. Moreover the tensile strength shows an even larger drop of about 90% and higher sensitivity to H-coverage even if it is small. Our results suggest that the unique coverage-dependent deterioration of the mechanical properties must be taken into account 2 when analyzing the performance characteristics of nanodevices fabricated from functionalized GAs.

Site-dependent hydrogenation on graphdiyne

“…It can also directly modify the interaction of graphdiyne with the environment, which can be exploited in several technological applications [21,22]. Because of these properties, a considerable number of papers on pristine and functionalized graphynes and graphdiynes has been recently reported [16,[23][24][25][26][27]. These results illustrate the remarkable variation in mechanical properties, fracture patterns, and exciting exotic electronic and geometrical properties exhibited by some hydrogenated graphyne and/or graphdiynes structures.…”

A theoretical consideration of the ballistic response of continuous graphene membranes

“…In summary, we have shown that multi-layer stacks of continuous graphene membrane could provide a revolutionary advance in ballistic barriers. In fact, graphene is only one example of the broad field of two-dimensional polymers [36][37][38][39][40][41][42][43][44], many of which would be expected to exhibit nominally isotropic high strength and stiffness. Other two-dimensional materials such as BN [45] and MoS 2 [46] are also predicted to provide excellent in-plane mechanical properties although at values that are somewhat lower than graphene.…”

Influence of hydrogen functionalization on the fracture strength of graphene and the interfacial properties of graphene–polymer nanocomposite

“…Hydrogen functionalization significantly lowers the tensile strength of graphene allotropes [17]; shear strength of graphene also reduces with increasing hydrogen adatom concentration [18]. Adsorption of methyl functional groups onto graphene greatly reduces its tensile strength, especially when methyl groups are arranged in lines perpendicular to the tensile direction [30].…”

“…The adsorption of adatoms could have a significant impact on the non-bonded interactions between graphene and composite matrix. Molecular dynamics simulation studies reveal that hydrogen adsorption can have a significant impact on the strength of graphene and its allotropes [17,18]. On the other hand, dangling bonds in defective graphene, which are created by defects (e.g.…”