The present work used ab initio density functional theory (DFT) to study two different physical phenomena crystallization fouling and clay-based polymer nanocomposites. In the first part, two foulant materials were studied including calcium carbonate, and calcium sulfate. The lattice energy and enthalpy of formations of each crystal system were predicted using DFT methods. The most stable forms of calcium carbonate foul ant, calcite and aragonite, were investigated. For calcium sulfate, both gypsum and anhydrite crystals were investigated. The thermodynamic solubility product of each crystal system, for both foul ants, was predicted from the lattice energy and enthalpy of formations. Comparison of the stability between the different crystal systems for the same foul ant material was carried out to elucidate the effect of crystal atomic configuration and space group on the stability of foulant materials. The effect of temperature on the formation and stability of foulant material was also carried out. The results obtained using DFT methods, for enthalpy of formation and thermodynamic solubility products, were comparable with the experimental data reported in the literature. In the second part, study has been made on the clay-based nylon 6 nanocomposite materials. The purpose was to understand the interfacial interactions between clay and polymer with and without surfactant component. Both sides of the clay were examined with nylon 6. In order to determine specifically the type of interfacial interaction between clay and nylon 6, the electron distribution around the whole system was predicted. The study was carried out at various isomorphic substitutions. The substitutions took place at both octahedral and tetrahedral layers of the clay. The strength between clay and nylon 6 was predicted by calculating the binding energy. The results obtained revealed that, the strength increases with the increase in the degree of isomorphic substitutions. The type of bond between nylon 6 and basal surface of the clay was found to be basically electrostatic interactions, and particularly hydrogen bonds. Whilst, the type of interactions between nylon 6 and clay edge surface was found to include covalent bonds as well as electrostatic interactions. The formation and breakage of covalent bonds between nylon 6 and clay means that, a chemical decomposition of the clay can happen when it is mixed with certain type of polymers. The presence of surfactant can decrease the interfacial interactions between clay and nylon 6.
| Identifer | oai:union.ndltd.org:ADTP/258351 |
| Date | January 2007 |
| Creators | Mrayed, Sabri Mohamed Ali, Chemical Sciences & Engineering, Faculty of Engineering, UNSW |
| Publisher | Awarded by:University of New South Wales. Chemical Sciences & Engineering |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Mrayed Sabri Mohamed Ali., http://unsworks.unsw.edu.au/copyright |
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