Thesis (MAppSc)--University of South Australia, 1998

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Thesis (PhD)--University of South Australia, 2001

The problem of determining the electrical double-layer interaction between a rigid planar surface and a deformable liquid droplet is formulated as a pair of coupled differential equations. The Young-Laplace equation, describing the shape of the droplet subject to a range of pressures, is solved numerically, while the linearized Poisson-Boltzmann equation, which describes the double-layer interaction is solved analytically. The van der Waals force is also considered. Results are provided over a wide range of boundary conditions, electrolyte concentrations and internal pressures. / Thesis (MSc(AppPhysics))--University of South Australia, 2001.

Thesis (PhD)--University of South Australia, 2001

The thesis presents a technique for and results of surface force measurements in a 3-phase system. The phases are a solid medium (mica), fluid (water and water-based electrolyte solutions) and gas (an air bubble). Analysis of deformation of the air bubble with respect to mutual position of the bubble and the mica surface, the capillary pressure of the undeformed bubble surface, the capillary pressure, and the disjoining pressure provide data for calculation of the air-liquid surface electrical potential. Furthermore, the information extracted from the deformation analysis made it possible to draw a conclusion regarding the nature of electrical double-layer forces in the system and, to some degree, about the effect of ion properties on the surface charging properties of the air-liquid interface. / Surface forces between an air bubble and a flat mica surface immersed in aqueous electrolyte solutions have been investigated using a modified surface force apparatus. This method allows forces to be detected in two regimes: at long range where the bubble is distorted slightly by the surface forces, and at short range where the force is manifest as disjoining pressure in a thin wetting film separating the bubble from the solid. The force was calculated from the equilibrium (or quasi-equilibrium) shape of the bubble surface. The experiments clearly show that long-range double-layer repulsion acts between mica and an air bubble in water and electrolyte solutions of different concentration. Double-layer repulsion indicates that the air bubble surface is negatively charged. However, there is clear evidence that charge regulation occurs at the air-water interface to maintain a constant surface potential, and as a result of this, the charge at this interface changes from negative to positive as the bubble approaches the negatively charged mica surface. Because of the attraction that arises due to the charge reversal, excessive force is required to separate the bubble from the mica, though the mica remains completely wetted by the aqueous phase. / The air-liquid surface potential has been evaluated from fitting a theoretically calculated shape to experimental measurements of bubble shape and film thickness, where the theoretical bubble shape was obtained from the numerical solution of the augmented Young-Laplace equation. Potential on the air bubble surface mainly depends on the concentration of electrolyte but is insensitive to the type of cation or anion within the low range of concentration investigated here. / The more important issue for such concentrations appears to be the electrostatic interaction between ions in solution and the air bubble interface. Therefore at the concentrations investigated, the potential on the gas-liquid interface arises due to the non-specific adsorption of ions to oriented water dipoles at the interface. / Thesis ([PhDApSc(MineralsandMaterials)])--University of South Australia, 2005.

Thesis (Ph. D.)--University of Adelaide, Dept. of Physics, and Mathematical Physics, 1993. / Includes bibliographical references (leaves 154-163).

Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Sotira Yiacoumi; Committee Co-Chair: Costas Tsouris; Committee Member: Ching-Hua Huang; Committee Member: Sankar Nair; Committee Member: Spyros G. Pavlostathis.

abstract: In the last few years, significant advances in nanofabrication have allowed tailoring of structures and materials at a molecular level enabling nanofabrication with precise control of dimensions and organization at molecular length scales, a development leading to significant advances in nanoscale systems. Although, the direction of progress seems to follow the path of microelectronics, the fundamental physics in a nanoscale system changes more rapidly compared to microelectronics, as the size scale is decreased. The changes in length, area, and volume ratios due to reduction in size alter the relative influence of various physical effects determining the overall operation of a system in unexpected ways. One such category of nanofluidic structures demonstrating unique ionic and molecular transport characteristics are nanopores. Nanopores derive their unique transport characteristics from the electrostatic interaction of nanopore surface charge with aqueous ionic solutions. In this doctoral research cylindrical nanopores, in single and array configuration, were fabricated in silicon-on-insulator (SOI) using a combination of electron beam lithography (EBL) and reactive ion etching (RIE). The fabrication method presented is compatible with standard semiconductor foundries and allows fabrication of nanopores with desired geometries and precise dimensional control, providing near ideal and isolated physical modeling systems to study ion transport at the nanometer level. Ion transport through nanopores was characterized by measuring ionic conductances of arrays of nanopores of various diameters for a wide range of concentration of aqueous hydrochloric acid (HCl) ionic solutions. Measured ionic conductances demonstrated two distinct regimes based on surface charge interactions at low ionic concentrations and nanopore geometry at high ionic concentrations. Field effect modulation of ion transport through nanopore arrays, in a fashion similar to semiconductor transistors, was also studied. Using ionic conductance measurements, it was shown that the concentration of ions in the nanopore volume was significantly changed when a gate voltage on nanopore arrays was applied, hence controlling their transport. Based on the ion transport results, single nanopores were used to demonstrate their application as nanoscale particle counters by using polystyrene nanobeads, monodispersed in aqueous HCl solutions of different molarities. Effects of field effect modulation on particle transition events were also demonstrated. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

The spatiotemporal evolution of temperature of leaves-on-branchlet carbon based electric double layer capacitors (EDLCs) under imposed constant current was studied using a continuum thermal model. The hot spot aggregated at the tips of graphene petals (GPs), particularly at the high concave surface, at the beginning of the charging step. As the charging proceeded, the overall temperature rose continuously, and the temperature distribution was likely uniform throughout the graphene petals due to an increasingly uniform distribution of ions on GPs surfaces. To elucidate the effects of electrode geometry on the change of temperature, several simple two-dimensional structures were also simulated in the charging step. Concave and planar structures contributed to high temperature change, while a convex structure tended to alleviate the hot spot. An insight into geometric effects on the thermal behavior may lead engineers to develop a new class of nanomaterials for supercapacitors.