Thesis (Ph. D.)--Institute of Paper Chemistry, 1972. / Includes bibliographical references (p. 145-149).

Thesis (Ph.D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Huang, Ching-Hua; Committee Member: Kim, Jaehong; Committee Member: Pavlostathis, Spyros; Committee Member: Stack, Andrew; Committee Member: Yiacoumi, Sotira

Thesis (Ph. D.)--School of Civil and Environmental Engineering, Georgia Institute of Technology, 2005. Directed by Ching-Hua Huang. / Wine, Paul, Committee Member ; Pavlostathis, Spyros, Committee Member ; Mulholland, James, Committee Member ; Yiacoumi, Sotira, Committee Member ; Huang, Ching-Hua, Committee Chair. Includes bibliographical references.

Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2006. / Tannenbaum, Rina, Committee Chair ; Rosario Gerhardt, Committee Member ; Hamid Garmestani, Committee Member ; Karl Jacob, Committee Member Vita. Includes bibliographical references.

Nanoalloys are an exciting new class of materials in the growing field of nanotechnology. Nanoalloys consist of the nanoscale co-aggregation of two or more metals with a potential to form compositionally-ordered phases or superstructures that have properties unlike those of the individual metal clusters or of bulk alloys of the constituent metals. This research seizes the opportunity that the nanoscale domain has to offer, and focuses on the synthesis of iron and cobalt nanoalloys via the simultaneous decomposition of iron cobalt organometallic precursors in a stabilizing environment, accompanied by the thorough characterization of the resulting nanoclusters. Zero-valent FeCo nanoalloys may potentially have interesting uses as magnetic materials. Since these clusters have sizes less than the size of their magnetic domain, the clusters will exhibit single domain magnetism. This magnetism may be observed by the presence of chain structures of FeCo nanoclusters due to the alignment of their single magnetic domains. In order to create a near-atomically homogeneous nanoalloy without preferential aggregation of its metal atom constituents, no clustering and phase separation should take place. In the bulk, alloys of iron and cobalt phase separate over most of the compositional range. Conversely, at the nanoscale, it may be possible to synthesize nanoalloy structures that are not normally favorable at given compositions, by the manipulation of reaction kinetics. In order to produce an atomically mixed nanoalloy, the transformation reactions of the organometallic precursors should display similar kinetic features, i.e. similar reaction rates. Therefore, the reaction kinetics of all the species in the reaction must be similar to avoid competition between them. As a result, kinetic control of the individual transformation reaction rates of each species may be used to modulate the aggregation and phase separation of the different species, and consequently control cluster morphology. This work has provided the framework for the design of synthesis methods that enable the control of the structure of FeCo nanoalloys with careful attention to precursor decomposition kinetics and the correlation between reaction kinetics and nanoalloy morphology.

The work in this thesis couples reactions with separations through the use of switchable and tunable solvents. Tunable solvents are mixed solvents which can be easily altered to afford conditions optimal for reaction or separation. Switchable solvents are solvents that can be switched when desired to alter their properties affording conditions suitable for separation. Other studies are of the reaction of CO2 with the amidine base DBU, and an NMR study of solvent-to-solute nuclear Overhauser effects. These examples constitute a marriage of reaction environment with separation environment, significantly, to the benefit of both.

In this study, we have developed a dense La0.85Sr0.15MnO3-δ (LSM) Ce0.9Gd0.1O1.95 (GDC) composite electrode system for studying the surface modification of cathodes. The LSM and GDC grains in the composite were well defined and distinguished using energy dispersive x-ray (EDX) analysis. The specific three-phase boundary (TPB) length per unit electrode surface area was systematically controlled by adjusting the LSM to GDC volume ratio of the composite from 40% up to 70%. The TPB length for each tested sample was determined through stereological techniques and used to correlate the cell performance and degradation with the specific TPB length per unit surface area. An overlapping spheres percolation model was developed to estimate the activity of the TPB lines on the surface of the dense composite electrodes developed. The model suggested that the majority of the TPB lines would be active and the length of those lines maximized if the volume percent of the electrolyte material was kept in the range of 47 57%. Additionally, other insights into the processing conditions to maximize the amount of active TPB length were garnered from both the stereology calculations and the percolation simulations. Steady-state current voltage measurements as well as electrochemical impedance measurements on numerous samples under various environmental conditions were completed. The apparent activation energy for the reduction reaction was found to lie somewhere between 31 kJ/mol and 41 kJ/mol depending upon the experimental conditions. The exchange current density was found to vary with the partial pressure of oxygen differently over two separate regions. At relatively low partial pressures, i0 had an approximately dependence and at relatively high partial pressures, i0 had an approximately dependence. This led to the conclusion that a change in the rate limiting step occurs over this range. A method for deriving the electrochemical properties from proposed reaction mechanisms was also presented. State-space modeling was used as it is a robust approach to addressing these particular types of problems due to its relative ease of implementation and ability to efficiently handle large systems of differential algebraic equations. This method combined theoretical development with experimental results obtained previously to predict the electrochemical performance data. The simulations agreed well the experimental data and allowed for testing of operating conditions not easily reproducible in the lab (e.g. precise control and differentiation of low oxygen partial pressures).

The current trend in the pharmaceutical industry is towards continuous flow processes. Continuous flow reactor technology can produce a cheaper, better quality product at reduced energy and environmental cost through more efficient mass and heat transfer. It also enables a simplified and faster approach to bulk production by scaling out as opposed to scaling up. The research presented here focuses on the configuration and installation of a continuous flow system into the laboratory, and the transfer of a Meerwein-Ponndorf-Verley (MPV) reduction from batch to continuous mode. The Corning® glass continuous flow reactor in our laboratory utilizes specially-designed mixing structures for enhanced mass transfer. Additionally, the glass reactor offers nonreactivity and corrosion resistance over a wide range of temperature and pressure, which conventional steel reactors do not allow. The MPV reduction is a well-known method to prepare primary and secondary alcohols from aldehydes and ketones, respectively. The traditional MPV reduction protocol (Al(OiPr)₃ in isopropanol) was modified to enable the technological transfer from batch to continuous mode. This is the first time MPV reduction reactions were carried out in continuous mode. As a result, the MPV reduction of the model compound, benzaldehyde, was successfully conducted with 60% less catalyst and product yield was improved up to 20% (average of 10%) in continuous flow reactions as compared to current batch technology. These results are being used to develop a technology roadmap for the pharmaceutical industry to implement continuous flow processes in their manufacturing operations.

Recent studies have demonstrated the omnipresence of antibacterial agents in the aquatic environment due to high usage and widespread applications of these compounds in medicine and agriculture, raising concerns over proliferation of antibiotic-resistant bacteria and other adverse health effects. Tetracyclines (TCs) are among the most widely used antibiotics and their fate and transformation in the soil-water environment are not yet well understood. Based on TCs' strong tendency to interact with metals, their environmental fate and transport are expected to be greatly influenced by metal species commonly present in waters and soils and thus the focus of this study. The study results show that TCs are highly susceptible to oxidative transformation mediated by dissolved Mn(II) and Cu(II) ions and manganese dioxide under environmentally relevant conditions. The oxidative transformation can occur via different TC structural moieties and reaction pathways when different metal species are involved, leading to complicated product formation patterns. It was also found that Al oxide surfaces can promote the acid-catalyzed isomeration and dehydration of TCs. To better evaluate the surface reactions of Mn oxide with TCs and other compounds, a new kinetic model was successfully developed to describe the complex reaction kinetics based on the experimental results with TCs and three other classes of antibacterial agents. Overall, this work significantly advances the fundamental understanding of the reaction mechanisms of TC compounds and provides the knowledge basis for better risk assessment of these compounds in the environment.

Metal oxide-facilitated transformation is likely an important degradation pathway of antibacterial agents at soil-water interfaces. Phenolic disinfectants (triclosan and chlorophene), fluoroquinolones (FQs), and aromatic N-oxides are of particular concern due to their widespread usage, potential toxicity and frequent detection in the environment. Results of the present study show that the above antibacterial agents are highly susceptible to metal oxide-facilitated oxidation. The interfacial reactions exhibit complex reaction kinetics, which are affected by solution pH, the presence of co-solutes, surface properties of metal oxides, and structural characteristics of antibacterial agents. Adsorption of the antibacterial agents to Mn and Fe oxide surfaces generally proceeds faster than oxidation reactions of these compounds by Mn and Fe oxides, especially in the case of Fe oxides. Reaction intermediates and end products are identified by GC/MS, LC/MS and/or FTIR. Structurally-related model compounds are examined to facilitate reaction site and mechanism elucidation. On the basis of experimental results and literature, reaction schemes are proposed. In general, the antibacterial agent is adsorbed to the oxide surface, forming a precursor complex. Electrons are transferred within the precursor complex from the antibacterial agent to the oxide, followed by releasing of the radical intermediates which undergo further reactions to generate oxidation products. The precursor complex formation and electron transfer are likely rate-limiting. For triclosan, phenoxy radicals are critical intermediates to form oxidation products through three pathways (i.e., radical coupling, further oxidation of the radical, and breakdown of an ether bond within the radical). The first two pathways are also operative in the oxidation of chlorophene. For FQs, oxidation generates radical intermediates that are most likely centered on the inner N in the piperazine ring. The radical intermediates then undergo three major pathways (i.e., radical coupling, N-dealkylation, and hydroxylation) to yield a variety of products. For aromatic N-oxides, a N-oxide radical intermediate is generated upon oxidation by MnO2, followed by the loss of oxygen from the N-oxide moiety and the formation of a hydroxyl group at the C-atom adjacent to the N-oxide moiety. Overall, a fundamental understanding of the reaction mechanisms between three classes of antibacterial agents and metal oxides has been obtained.