Dynamic trends for char/soot formation during secondary reactions of coal pyrolysis by large-scale reactive molecular dynamics

ABSTRACTUnzipping carbon nanotubes (CNTs) is considered one of the most promising approaches for the controlled and large-scale production of graphene nanoribbons (GNR). These structures are considered of great importance for the development of nanoelectronics because of its dimensions and intrinsic nonzero band gap value. Despite many years of investigations some details on the dynamics of the CNT fracture/unzipping processes remain unclear. In this work we have investigated some of these process through molecular dynamics simulations using reactive force fields (ReaxFF), as implemented in the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code. We considered multi-walled CNTs of different dimensions and chiralities and under induced mechanical stretching. Our preliminary results show that the unzipping mechanisms are highly dependent on CNT chirality. Well-defined and distinct fracture patterns were observed for the different chiralities. Armchair CNTs favor the creation of GNRs with well-defined armchair edges, while zigzag and chiral ones produce GNRs with less defined and defective edges.

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Reactive Molecular Dynamics Simulation of Graphene-Based Nanomaterials Produced by Confined Heating of Polymer

Volume 2: Micro/Nano-Thermal Manufacturing and Materials Processing; Boiling, Quenching and Condensation Heat Transfer on Engineered Surfaces; Computational Methods in Micro/Nanoscale Transport; Heat and Mass Transfer in Small Scale; Micro/Miniature Multi-Phase Devices; Biomedical Applications of Micro/Nanoscale Transport; Measurement Techniques and Thermophysical Properties in Micro/Nanoscale; Posters ◽

10.1115/mnhmt2016-6716 ◽

2016 ◽

Author(s):

Yuan Dong ◽

Jian Lin

Keyword(s):

Molecular Dynamics ◽

High Performance ◽

Large Scale ◽

Md Simulations ◽

Dynamics Simulation ◽

Metal Catalyst ◽

Processing Temperature ◽

Scale Production ◽

Reactive Molecular Dynamics ◽

Laser Scribing

The graphene-based nanomaterial has great potential as catalyst and supercapacitors. In this paper we study the pyrolysis of polymers in a nanosecond time scale with the reactive molecular dynamics (MD) simulations using ReaxFF potential. It is found that the confined heating will produce graphene-like nanostructures out of two kinds of polymers: polyimide and polyether ether ketone. The peak pressure achieves above 3GPa with a processing temperature of 3000K. It indicates that the local high temperature and pressure can convert polymer to graphene-based nanomaterials without metal catalyst, which may enable large scale production of high performance electrical devices and microreactors with laser scribing method.

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Carbon Nanoscrolls at High Impacts: A Molecular Dynamics Investigation

MRS Advances ◽

10.1557/adv.2016.200 ◽

2016 ◽

Vol 1 (20) ◽

pp. 1423-1428 ◽

Cited By ~ 1

Author(s):

José Moreira de Sousa ◽

Leonardo Dantas Machado ◽

Cristiano Francisco Woellner ◽

Pedro Alves da Silva Autreto ◽

Douglas S. Galvao

Keyword(s):

Molecular Dynamics ◽

Large Scale ◽

Graphene Nanoribbons ◽

Impact Behavior ◽

Experimental Investigations ◽

Axis Orientation ◽

Reactive Molecular Dynamics ◽

Structural Deformations ◽

Carbon Nanoscrolls ◽

Graphene Membranes

ABSTRACTThe behavior of nanostructures under high strain-rate conditions has been object of interest in recent years. For instance, recent experimental investigations showed that at high velocity impacts carbon nanotubes can unzip resulting into graphene nanoribbons. Carbon nanoscrolls (CNS) are among the structures whose high impact behavior has not yet been investigated. CNS are graphene membranes rolled up into papyrus-like structures. Their unique open-ended topology leads to properties not found in close-ended structures, such as nanotubes. Here we report a fully atomistic reactive molecular dynamics study on the behavior of CNS colliding at high velocities against solid targets. Our results show that the velocity and scroll axis orientation are key parameters to determine the resulting formed nanostructures after impact. The relative orientation of the scroll open ends and the substrate is also very important. We observed that for appropriate velocities and orientations, the nanoscrolls can experience large structural deformations and large-scale fractures. We have also observed unscrolling (scrolls going back to planar or quasi-planar graphene membranes), unzip resulting into nanoribbons, and significant reconstructions from breaking and/or formation of new chemical bonds. Another interesting result was that if the CNS impact the substrate with their open ends, for certain velocities, fused scroll walls were observed.

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