Photo luminescence of C545T and NPB on porous Si was studied. The porous Si structures were obtained by anodic dissolution of p-type Si in a concentrated HF solution. Pore diameter of 100Å and pore layer of a thickness around 0.5£gm were formed by varying the electrolytic condition, including HF concentration, anodiztation time, electrolytic current and voltage. The photo luminescence of C545T and NPB were investigated by depositing them onto the porous Si substrate using spin coating, dipping with ultrasonic agitation and thermal evaporation techniques. The photo luminescence of C545T and NPB were found to peak around 580nm and 440nm for samples prepared by spin coating. However, for NPB samples deposited by dipping with ultrasonic agitation and thermal evaporation, additional photo luminescence peak at 430nm were observed. SEM photos analysis confirm that the organic materials can diffuse into the Si pores by ultrasonic agitation and deposition in vacuum.

In summary, it has been shown during this study that bimetallic Fe and Mn containing catalysts can be prepared by wet impregnation and not by ion exchange because of the competition between two different metals at different oxidation number. Only a single metallic phase catalyst could be prepared successfully by using ion exchange.

In summary, it has been shown during this study that bimetallic Fe and Mn containing catalysts can be prepared by wet impregnation and not by ion exchange because of the competition between two different metals at different oxidation number. Only a single metallic phase catalyst could be prepared successfully by using ion exchange.

Thesis (Ph.D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 406-418).

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

archives@tulane.edu / Enhanced oil recovery (EOR) and oil spill remediation (OSR) in porous media both share a common theme in that they can both be modeled as a system comprising of two immiscible liquid phases and a solid porous phase. EOR seeks to improve the recovery of crude oil from existing oil reserves, while OSR improves ecological sustainability. In this thesis two novel techniques with the potential of improving the recovery of non-aqueous phase liquid (NAPL) that is trapped in a water filled random porous media. In the first project, an oil-soluble surfactant was studied to enhance crude oil mobilization in a cryolite-packed miniature bed. The cryolite packed bed provided a transparent, random porous medium for observation at the microscopic level. In the first part of the project, oil-soluble surfactants; Span 80 and Eni-surfactant (ES) were dissolved directly into the crude oil. The porous medium was imbued with the crude oil (containing the surfactants), and deionized water was the flooding phase, in this experiment, the system containing ES had the best performance. Subsequently, Sodium Dodecyl Sulfate (SDS), a hydrosoluble surfactant was used to solubilize the ES, with the SDS acting as a carrier for the ES to the contaminated porous media. Finally, the SDS/Eni-Surfactant micellar solutions were used in oil-removal tests on the packed bed. Grayscale image analysis was used to quantify the oil recovery effectiveness for the flooding experiments by measuring the white pixel percentage in the packed bed images. The SDS/ES flooding mixture had a better performance than the SDS alone. Furthermore, a model liquid hydrocarbon (n-hexadecane) was used to gain insight on the mobilization of non-aqueous phase liquids (NAPLs) trapped in porous formations, important for both EOR and oil spill remediation in porous media. Food-grade surfactants lecithin from soy and tween 80 were compared to commercial dispersant Corexit 9500A, for their ability to mobilize the hydrocarbon originally trapped in a water-filled cryolite porous medium. Red dye was added to the n-Hexadecane to improve visualization, and the aqueous phase incorporated different ratios of the surfactants Lecithin and Tween 80 to seek synergistic benefits when the two surfactants are combined. Visual-microscopic flooding experiments carried on a miniature packed bed produced images which were then analyzed using grayscale image analysis. It was determined that a ratio 40:60 by weight of Lecithin to Tween 80 has the best performance in the mobilization of n-hexadecane from the porous media. Furthermore, any (non-optimal) mixture of lecithin and tween 80 exhibited a better (synergistic) performance in n-Hexadecane recovery from the porous media than when applying either surfactant separately. Finally, applying the video-microcapillary technique utilized in the first two projects, but with a slight modification, the effect of temperature change on a highly viscous oil phase flowing through a water-filled porous media was studied. The glass microcapillary was coated externally with a thin film of Indium Tin Oxide (ITO) to render it electrically conductive. When an electric current is applied to the outside of the coated capillary, the temperature of the capillary can be elevated. The tapered region of the capillary is filled with cryolite to form a random porous media and flow experiments were conducted in this region. Applying this technique, we studied the flow pattern of a highly viscous oil displacing an aqueous phase in a porous media at 60, 70, 80, 90, and 100oC. Also, we observed capillary fingering, continuous, and Haines jump flow patterns, with capillary fingering and Haines jump more prominent at 10-3 capillary number, while flow at 10-2 exhibited continuous flow pattern. Chapters 2 and 3 of this dissertation include content in peer-reviewed journal articles published by the author.1,2 / 1 / Chike George Ezeh

Porous structures are a particular type of solids, where a large number of pores exist in the geometric domain of interest. Research on porous structures have received increasingly keen interest in recent years and this is largely because of many unique and superior properties that porous structures possess. They can undertake special tasks which general solid materials are not competent to do. In recent twenty years numerous representations are put forward for porous structure modeling. But the challenges in practical porous structure design still exist and the structure heterogeneity brings many difficulties. This thesis is motivated to propose new porous structure modeling strategies which are more accurate, flexible and easy for porous structure description. An approach of porous structure modeling based on quadtree/octree and NURBS is proposed first. Quadtree and octree are tools for modeling domain partition. The pore size and pore distribution are controlled by the flexibility of quadtree and octree enumeration technique. Derived polygon and polyhedron are then introduced to assist the generation of NURBS curves and surfaces. These NURBS curves and surfaces form the boundaries of the porous structures. However there are limitations of the above method. The accurate control of porosity is not easily achieved in 3D porous structure modeling and seemingly adopting quadtree/octree for the modeling domain partition is also less than satisfactory. Hence a new representation for porous structures based on Centroidal Voronoi tessellation (CVT) and pore-network is put forward. CVT is utilized for modeling domain partition because the CVT cells are approximate hexagons which is widely existent in plants, animals and other cellular structures in nature. The density distribution function used in CVT generation also helps to build functionally graded porous structures. Pore-network, which is a mature and commonly used model in the research of multiphase flow in porous media, is subsequently introduced to build the porous structures. This modeling approach results in porous structures that could mimic the geometry and performance of structures in nature. To evaluate the object’s properties, finite element analysis (FEA) is conducted on the porous structure models represented by the two methods. The mechanics properties of the two types of models are analyzed. The stress-strain curve of each sample is plotted and the effective Young’s modulus is calculated. Comparison of these two types of models is also done. Besides, the contributions of the thesis and suggestions for future research are also discussed. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Thesis (Ph. D - Hydrology and Water Resources) - University of Arizona. / Includes bibliographical references (leaves 303-310).

Thesis (M.Sc.)--Aberdeen University, 2009. / Title from web page (viewed on Mar. 3, 2010). Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Mukul M. Sharma. Vita. Includes bibliographical references.