The
field of two-dimensional (2D) nanomaterials has gained significant
interest over the last few decades in numerous applications because
of their unique properties that exhibit when a bulk material is reduced
to its 2D form. A wide variety of 2D layered materials are synthesized
by a newly developed compressible flow exfoliation (CFE) process,
which has considerable advantages over current top-down approaches.
In this study, classical molecular dynamics (MD) simulations are used
to investigate the interactions of gas particles with pristine, unfunctionalized
graphene sheets during the CFE process and try to understand the atomistic
mechanism of layer separation. The thermal vibration of graphene layers
increases with the elevation of temperature that accelerates the exfoliation
tendency, but the presence of static gas particles is insignificant
here because of their lower binding energy. The range of one-directional
flow velocities is incorporated to the compressible gases to replicate
the experimental situation, and dispersion of graphene is observed
when the velocity exceeds the supersonic flow condition. Analyzing
the dynamic properties of exfoliation, it is established that sliding
or the parallel direction is the preferable exfoliation mechanism
of graphene than vertical separation. Besides, the upstream pressure
plays a fundamental role because gas density and flow velocity are
associated with that. It is also observed that heavier gas is less
susceptible to delaminate graphene than lighter gas because of their
higher atomic mass and lower flow rate at identical conditions. The
findings of this study provide more flexibility to synthesize not
only graphene but any 2D materials using compressible gases.
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