Sliding Dynamics of Parallel Graphene Sheets: Effect of Geometry and Van Der Waals Interactions on Nano-Spring Behavior

Abstract

Graphene and carbon nanotubes are promising materials for nanoelectromechanical systems. Among other aspects, a proper understanding of the sliding dynamics of parallel graphene sheets or concentric nanotubes is of crucial importance for the design of nano-springs. Here, we analytically investigate the sliding dynamics between two parallel, rigid graphene sheets. In particular, the analysis focuses on configurations in which the distance between the sheets is kept constant and lower than the equilibrium interlayer spacing of graphite (unstable configurations). The aim is to understand how the interlayer force due to van der Waals interactions along the sliding direction changes with the geometrical characteristics of the configuration, namely size and interlayer spacing. Results show metastable equilibrium positions with completely faced sheets, namely a null force along the sliding direction, whereas net negative/positive forces arise when the sheets are approaching/leaving each other. This behavior resembles a molecular spring, being able to convert kinetic into potential energy (van der Waals potential), and viceversa. The amplitude of both storable energy and entrance/exit forces is found to be proportional to the sheet size, and inversely proportional to their interlayer spacing. This model could also be generalized to describe the behavior of configurations made of concentric carbon nanotubes, therefore allowing a rational design of some elements of carbon-based nanoelectromechanical systems.

Stacking of Monolayer Graphene Particles at a Water–Vapor Interface

“…Spheroidal particles are isotropic and maintain a characteristic length scale (∼10 3 nm) that is much greater than the thickness of a fluid–fluid interface (∼10 –1 –10 0 nm), , while monolayer graphene particles have a thickness (∼10 –1 nm) that is commensurate with the length scales of out-of-plane thermal motions of a fluid–fluid interface ( i.e ., capillary waves) . This results in graphene particles being more sensitive to thermal fluctuations of a fluid–fluid interface than spheroidal particles, and small variations in the position of graphene particles normal to the interface could induce neighboring graphene particles to overlap and stack due to attractive, face-to-face van der Waals forces, as observed in MD simulations. , Yet, there is an apparent discord between simulations and experiments, as experimental evidence has demonstrated laterally aggregated and only partially overlapped monolayer particles even after compression to high particle densities. ,, …”

Heat Transfer at the Interface of Graphene Nanoribbons with Different Relative Orientations and Gaps

“…Similarly to the typical empirical expressions adopted for heat transfer, only basic formula building-blocks (i.e., constant, multiplication, division, power) have been considered for the Eureqa fitting. As a result, the simulation results in Table A1 (configurations N. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] have been found to be best fitted (R 2 = 0.99, see Figure 4b) by the following expression:…”

“…Carbon fillers such as carbon nanotubes and graphene nanoribbons are often suggested as possible additives in composite materials. In fact, these materials show a remarkable combination of superior thermal [1][2][3][4], electrical [5][6][7], lubrication [8,9] and mechanical [10][11][12] properties, which have the potential to significantly enhance the performance of base materials. In particular, Polymer Nanocomposites (PNCs) with carbon nanofillers are currently employed in a broad variety of industries, such as the energy [13], aerospace [14], biomedical [15], electronics [16,17] and automotive ones [18,19].…”

The impact of physicochemical features of carbon electrodes on the capacitive performance of supercapacitors: a machine learning approach

“…In perspective, graphene is a promising electrode material for supercapacitors too, due to a high electrical conductivity, high SSA, and excellent mechanical strength 41,42 . Its porous structure also facilitates charge transport in the supercapacitor.…”