Date of Award
College of Natual Science and Mathematics, Physics and Astronomy
M. Mercedes Calbi
Adsorption, Carbon nanohorns, Carbon nanotubes, Isosteric heat, Isotherms, Monte carlo
A study of gas adsorption has been carried out with the focus of better understanding the relationships between the individual properties of the adsorbent/adsorbate (e.g. material structure, interactions, gas size and shape, etc.) and the overall adsorptive properties of the combined system (e.g. capacity, binding strength, equilibration time, etc.) as a function of thermodynamical variables. This is useful from the perspective of a comprehensive and fundamental understanding as well as for practical applications. The equilibrium regime of adsorption on carbon nanostructure materials (nanohorns, nanotubes, and graphite) is investigated using molecular statics (MS) and grand canonical monte carlo (GCMC) methods for a variety of gas species (carbon dioxide, ethane, argon, etc.). Through the controlled variation and comparison of these simulations, interaction and structural models are developed to help interpret and understand experimental observations. For the case of the adsorption of ethane on closed carbon nanohorns, the lack of distinct features in the adsorption data was found to be a result of binding on exterior sites of the aggregate as well as the increased degrees of freedom of the molecular species. The isosteric heat of adsorption of carbon dioxide on both carbon nanotubes and nanohorns has been experimentally shown to trend through a minimum before approaching the bulk value, which contradicts what is observed for all other adsorbate species. Here it is shown that carbon dioxide's unique behavior is due to the increased gas-gas interactions which are present due to its quadrupole moment. In order to study the effect of complex geometries and inhomogeneous interaction profiles in the kinetic regime, such as those present in carbon nanohorns, a general 3D on-lattice KMC modelling scheme was developed. A lattice model for carbon nanohorns was developed within this scheme and preliminary calculations show the variation of binding energy along the length of the pore serves to reduce the time to reach equilibrium as well as causes higher site occupancy near the bottom of the pore.
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Justin Matthew Petucci
Received from ProQuest
Petucci, Justin Matthew, "Gas Adsorption in Carbon Nanohorns: Equilibrium and Kinetics" (2020). Electronic Theses and Dissertations. 1822.