Brent Foy (Committee Member), Gregory Kozlowski (Committee Member), Amit Sharma (Advisor)
Master of Science (MS)
The bottom-up analysis of Carbon Nanotube synthesis is not well understood. Specifically, the question as to how carbon adsorbs to a substrate inclusive of a supported catalyst may lead to the energetically favorable structure of a hexagonal close- packed structure along the wall, or walls, of the tube. A first time simulation using COMSOL Multiphysics has been generated in order to capture the gas-phase mech- anism which leads to carbon production. It is thought that the carbon adsorbs and the walls are formed from the bottom up and the inside out for multi-wall CNTs. The studies involved accurately setting up a simulation to capture chemical kinetics, mass transport, heat transfer, and fluid flow. It is shown that a variation in inflow velocity yields a variation in efficiency of ethylene cracking in the reactor. When the residence time is increased the outlet concentration of ethylene is lowered, as expected. This means that variations in concentrations can be accounted for through varying initial parameters. Chemical reactions involving ethylene decomposition from GRI-Mech 3.0  is imported and the validity of the Troe Form chemical kinetics was tested. Using equilibrium calculations with the use of an ICE (Initial, Concentration, Equilibrium) table, 0-D studies using the high pressure limit of the rate constant and the Troe Form of the rate constant were used in separate tests for comparison. It was subsequently showed that the Troe Form kinetics do not accurately determine the expected concentrations. The chemical species concentration, gas pressure, temperature, and velocities were calculated for a final set of approximately 32 gas-phase reactions. A nearly completed set of gas-phase and surface reactions were compiled but only the most important chemical reactions were implemented in the present studies to form a basis for future analysis. The results of the present study shows production of amorphous carbon within the gas-phase, which is not high enough for CNT growth, implying the impor- tance of surface hydrocarbon reactions in the CNT production in a CVD reactor.
Department or Program
Department of Physics
Year Degree Awarded
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