Thesis (M.Eng.(Chemical engineering))--University of Pretoria, 2009. / Includes bibliographical references.

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed July 8, 2009; title from PDF t.p. Includes bibliographical references (p. 47).

Thesis (Ph. D.)--Rutgers University, 2010. / "Graduate Program in Chemical and Biochemical Engineering." Includes bibliographical references (p. 136-142).

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 175-188).

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (p. 166-172).

Liquid dispersions of colloidal particles play a big role in nature and as industrial products or intermediates. Their material properties are largely determined by the liquid-mediated particle-particle interaction. In water-based systems, electric charge is ubiquitous and electrostatic particle interaction often is the primary factor in stabilizing dispersions against decomposition by aggregation and sedimentation. Very nonpolar liquids, by contrast, are usually considered free of charge, because their low dielectric constant raises the electrostatic cost of separating opposite charges above the available thermal energy. Defying this conventional wisdom, nonpolar solutions of certain ionic surfactants do support mobile ions and surface charges. Even some nonionic surfactants have recently been found to raise the conductivity of nonpolar oils and promote surface charging of suspended particles, but this counter-intuitive behavior is not yet widely acknowledged, nor is the mechanism of charging understood. The present study provides the first characterization of the electrostatic particle interaction caused by nonionizable surfactants in nonpolar oils. The methods used in this study are video microscopy experiments where particle positions of equilibrium ensembles are obtained and translated into particle interactions. Experimentally, equilibrium particle positions are monitored by digital video microscopy, and subjected to liquid structure analysis in order to find the energy of interaction between two particles. The observed interaction energy profiles agree well with a screened-Coulomb potential, thus confirming the presence of both surface charge and mobile ions in solution. In contrast to recently reported electrostatic particle interactions induced by ionic surfactants in nonpolar solution, the present study finds evidence of charge screening both above and below the surfactant's critical micelle concentration, CMC. Fitted Debye screening lengths are much larger than in aqueous systems, but similar to the Debye length in nonpolar oils reported for micellar solutions of ionic surfactants cite{hsu_charge_2005}. Radial distribution functions obtained from experiments are compared to Monte-Carlo simulations with input potentials obtained from a fit to the interaction measurement. The measured electrostatic forces and fitted surface potentials are fairly substantial and easily capable of stabilizing colloidal dispersions. Although few in number, surface charges formed on polymer particle surfaces submerged in nonpolar solutions of nonionizable surfactants create surface potentials comparable to those in aqueous systems.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references. Available also in a digital version from Dissertation Abstracts.

Interactions of colloidal particles with surfaces occur in natural and engineered systems, and they influence the transport of contaminants through diffusion, aggregation, filtration, and sedimentation. To quantify the transport and fate of colloidal particles and their influence on environmental systems, it is important to understand their interactions with surfaces. These interactions are influenced by physical and chemical surface properties such as hydrophobicity, charge density, and roughness, as well as environmental conditions such as relative humidity (RH). In atmospheric systems, RH induces the capillary force and also influences the contributions of van der Waals and electrostatic forces. To investigate the role of surface properties and RH in the interaction of colloidal particles with surfaces, atomic force microscopy was employed to measure the adhesion and friction forces of colloidal particles including Bacillus thuringiensis spores, silica, and gold at various experimental conditions with several types of surfaces including mica, silica, and radioactive gold. Contributions to the adhesion force by van der Waals, capillary, and electrostatic forces were theoretically calculated and compared to measured forces. Through experimental results and theoretical studies, it was identified how surface properties of interacting surfaces and experimental conditions influence the interfacial interactions of colloidal particles in atmospheric systems. The role of RH in adhesion and friction depends on the hydrophobicity or contact angles of interacting surfaces and surface roughness. Relative humidity also influences the contribution of electrostatic force to the total adhesion force by screening the strength of surface potential or providing a passage for charge leakage. The results of this thesis provide a better understanding of particulate processes that are influenced by the interactions of colloidal particles with surfaces and can be useful in monitoring and control of contamination in atmospheric systems.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 117-131).

Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006. / Yiacoumi, Sotira, Committee Chair ; Tsouris, Costas, Committee Co-Chair ; Pavlostathis, Spyros, Committee Member ; Tannenbaum, Rina, Committee Member ; Sherrill, David, Committee Member.