There are two main objectives in my research work. The first objective is to
investigate the adsorption behavior of various gases on single walled carbon nanotubes. This is accomplished
by using the classical molecular simulation methods. Our simulation work has provided
molecular level interpretation of some interesting phenomena observed experimentally by our collaborators.
The second objective is to study the catalytic properties of metal/metal carbide surfaces and interfacial
phenomena by using ab initio density functional theory.
We have studied the adsorption of various gases on carbon nanotubes by
using classical molecular simulation and optimization techniques. We specifically have
investigated the displacement of adsorption on different adsorption sites.
The systems investigated include
CO2 on SWNT, Xe/CF4 on SWNT and CO2/Xe on SWNT. Our simulations indicate that CO2 is easily replaced from
the endohedral and interstitial sites of SWNT bundles by Xe,
while the groove/external surface sites loose much less CO2. These calculations agree
very well with the experimental observations.
We have also observed unique one dimensional behavior of gases adsorbed on carbon nanotubes by using optimization and
parallel tempering Monte Carlo. The results show that CO2 molecules adsorbed in the
groove sites of single walled carbon nanotubes display behavior that
is quasi-1-dimensional. At finite coverages of CO2 in grooves
clusters containing only odd numbers of molecules are formed at low
temperatures. Even numbers of molecules form two clusters, each
containing an odd number of molecules.
We have carried out density functional theory studies on the catalytic
properties of metal surfaces. We investigated adsorption of CO on the Ag(110)
surface and CO adsorption, diffusion and dissociation on the W(111) surface.
The CO molecule is
found to non-dissociatively adsorb in end-on configurations (alpha
states) and dissociatively absorb in inclined configurations (beta
states). The dissociation of beta state CO is found to have an
activation energy of about 0.8 eV, which is lower than the energy
required to desorb CO molecularly from the surface.
We have also studied the tungsten difussion mechanisms in cobalt. Our calculations
indicate that the diffusion is vacancy mediated. Therefore, we proposed the triangle
and quadrangle mechanims, and examined the full diffusion pathways.
Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-04072006-170554 |
Date | 27 September 2006 |
Creators | Chen, liang |
Contributors | Joseph J. McCarthy, Christopher Matranga, Goetz Veser, J. Karl Johnson, Kenneth D. Jordan |
Publisher | University of Pittsburgh |
Source Sets | University of Pittsburgh |
Language | English |
Detected Language | English |
Type | text |
Format | application/pdf |
Source | http://etd.library.pitt.edu/ETD/available/etd-04072006-170554/ |
Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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