Simulation of carbon nanocones using molecular dynamics
用分子動力學模擬碳納米錐
Student thesis: Master's Thesis
Author(s)
Detail(s)
Awarding Institution | |
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Award date | 15 Feb 2008 |
Link(s)
Permanent Link | https://scholars.cityu.edu.hk/en/theses/theses(26e23564-18ca-457d-82f4-63ed97cefa89).html |
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Other link(s) | Links |
Abstract
research community has paid
much attention to this form of carbon nanostructure because of its exceptional
properties. There are several methods for studying CNTs, such as molecular dynamics
(MD), quantum mechanics, and continuum theory, all of which have been variously
used to determine the properties of CNTs, such as their mechanical properties, thermal
properties, and electrical properties.
However, another newly synthesized form of carbon nanostructure – the carbon
nanocone (CNC) – has attracted less attention. Unlike the well developed theories for
CNTs, research work on CNCs is in its infancy. Up to now, researchers have struggled
to establish universally accepted approaches for CNC structures and growth
mechanisms, and reports on their mechanical properties are even scarcer.
In this work, the mechanical behavior of single-walled carbon nanocones
(SWCNCs) with an apex angle of 19.2º under compression is investigated. The
analysis is performed using molecular dynamics simulation, with two loading
directions – axial compression and in-plane compression – being applied to study
their influence on the strain energy of CNCs. Empirical formulas are derived for
calculating the critical strains of CNCs with various top radii that are subjected to
both axial and in-plane compression. The results of the simulation reveal that cones
under in-plane compression show a higher energy level than those under axial
compression. In the buckling and postbuckling stage, each shape change,
accompanied by an abrupt release of energy in the energy-strain curve, is analyzed,
and the possible reasons for early plastic failure are examined, taking into account the
buckling behavior of CNCs with different geometrical parameters (top radius, bottom
radius and height). The computed results show that for a fixed height/bottom radius
ratio, CNCs with a smaller top radius tend to be stiffer.
The elastic and plastic behavior of SWCNCs under tension is also examined
using MD simulation, and the force-strain response of CNCs are obtained and
compared with those of CNTs. It is revealed that CNCs with a larger apex angle have
a greater failure strength but a smaller maximum strain under tension. Following this
law, CNTs exhibit the smallest failure strength but the greatest maximum strain due to
their zero conical angle. The mechanical properties of CNCs, such as the Young’s
modulus, elastic strain limit, and ultimate force, are determined and discussed. The
Young’s modulus of CNCs is to found fall within the range of 0.29Tpa to 0.73Tpa,
depending on their conical angles, height, and top radius. Illustrations of the Young’s
modulus of CNCs demonstrate the dependency of the stiffness on the height to top
radius ratio. The Young’s modulus tends to converge as the top radius of CNCs
achieves a certain level for a fixed length to top radius ratio.
- Nanostructured materials, Molecular dynamics, Computer simulation