Master of Science (M.S.), University of Dayton, 2017, Renewable and Clean Energy

Photovoltaic-thermal (PVT) technology is a relatively new technology that comprises a photovoltaic (PV) panel coupled with a thermal collector to convert solar radiation into electricity and thermal energy simultaneously. Since cell temperature affects the electrical performance of PV panels, coupling a thermal collector with a PV panel contributes to extracting the heat from the latter to improve its performance. In order to ensure a sufficient temperature difference between the PV cells and the working fluid temperature entering the thermal collector, the circulated water has to reject the heat that has been removed from the PV cells into a relatively colder environment. Borehole thermal energy storage (BTES), which is located underground, often serves as this relatively colder environment due to the stability of underground temperatures, which are usually lower than the working cell temperature. Use of BTES is especially beneficial in summer, when the degradation in cells efficiency is highest. In this thesis, the electrical, thermal, and economic performances of a PVT system are evaluated for three types of buildings -- residential, small office, and secondary school -- in two different climates in the United States, one of which is hot and the other is cold. For each case, two different scenarios are considered. In the first, a PVT system is coupled with BTES, and a ground-coupled heat pump (GCHP) is in use. In the second, a PVT system is coupled with BTES and no GCHP is in use. Each scenarios' GCHP performance is assessed as well. Both the PVT collectors and GCHP performances are evaluated over short and long-term to study the effect of continued ground heat imbalance on both technologies.

Committee: Andrew Chiasson Ph.D. (Committee Chair); Youssef Raffoul Ph.D. (Committee Member); Robert Gilbert Ph.D. (Committee Member) Subjects: Energy; Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2003, Chemical Engineering

Continuous production of microcellular foams, characterized by cell size smaller than 10 μm and cell density larger than 10 9 cells/cm 3 , was studied using supercritical carbon dioxide (CO 2 ) as the foaming agent. Microcellular foams of polystyrene and polystyrene nanocomposites were successfully produced on a two-stage single screw extruder. The contraction flow in the extrusion die was simulated with the FLUENT fluid dynamics computational code to predict profiles of pressure, temperature, viscosity, and velocity. The nucleation onset was determined based on the pressure profile and equilibrium solubility. It was shown that a high CO 2 concentration or a high foaming temperature induces an earlier nucleation near the die entrance. The pressure profile and the position of nucleation onset were correlated to cell nucleation and growth, which helps understand the effects of operating conditions on cell structure. To perform the simulation, viscosity and solubility of the CO 2 /polystyrene system were characterized. Sanchez-Lacombe equation of state was applied to represent the phase equilibrium. Effects of temperature, pressure, and CO 2 content on the shear viscosity were explained using the free volume theory. Systematic experiments were performed to verify effects of three key operating conditions: CO 2 content, pressure drop or pressure drop rate, and foaming temperature, on the foam cell structure. Experimental results were compared with simulations to gain insight into the foaming process. Studies exhibit that a higher pressure drop or pressure drop rate results in smaller cells and greater cell density. Below the CO 2 solubility, cell size decreases and cell density increases with an increase of CO 2 concentration. A high CO 2 concentration favors producing open cell foams. Die temperature affects both cell size and cell structure (open or closed). Combining nano-clay compounding with supercritical CO 2 foaming provides a new technique for the design and con (open full item for complete abstract)

Committee: Kurt Koelling (Advisor) Subjects:

Doctor of Philosophy, University of Toledo, 2022, Physics

In this dissertation the structural properties of bulk alloys and thin-films are studied using a variety of di erent techniques including density functional theory (DFT) and accelerated dynamics. The first part of this dissertation involves the use of DFT calculations. In particular, in Chapter 3 the stability and mechanical properties of 3d transitional metal carbides in zincblende, rocksalt, and cesium chloride crystal structures are studied. We find that the valence electron concentration and bonding configuration control the stability of these compounds. The filled bonding states of transition metal carbides enable the stability of the compounds. In the second part of this dissertation we use a variety of accelerated dynamics techniques to understand the properties of growing and/or sublimating thin-films. In Chapter 4, the results of temperature-accelerated dynamics (TAD) simulations of the submonolayer growth of Cu on a biaxially strained Cu(100) substrate are presented. These simulations were carried out to understand the e ects of compressive strain on the structure and morphology. For the case of 4% compressive strain, stacking fault formation was observed in good agreement with experiments on Cu/Ni(100) growth. The detailed kinetic and thermodynamic mechanisms for this transition are also explained. In contrast, for smaller (2%) compressive strain, the competition between island growth and multi-atom relaxation events was found to lead to an island morphology with a mixture of open and closed steps. In Chapter 5, we then study the general dependence of the diffusion mechanisms and activation barriers for monomer and dimer diffusion as a function of strain. The results of TAD simulations of Cu/Cu(100) growth with 8% tensile strain are also presented. In this case, a new kinetic mechanism for the formation of anisotropic islands in the presence of isotropic diffusion was found and explained via the preference for monomer diffusion via exchange over hopp (open full item for complete abstract)

Committee: Jacques Amar Professor (Advisor) Subjects: Physics

Doctor of Philosophy (PhD), Wright State University, 2021, Biomedical Sciences PhD

The carotid bodies (CB) are peripheral chemoreceptors that detect changes in arterial oxygenation and, via afferent inputs to the brainstem, correct the pattern of breathing to restore blood gas homeostasis. Elucidating the “signal” that couples carotid body sensory type I cell (CBSC) hypoxic mitochondrial inhibition with potassium channel closure has proven to be an arduous task; to date, a multitude of oxygen-sensing chemotransduction mechanisms have been described and altercated (Varas, Wyatt & Buckler, 2007; Gao et al, 2017; Rakoczy & Wyatt, 2018). Herein, we provide preliminary evidence supporting a novel oxygen-sensing hypothesis suggesting CBSC hypoxic chemotransductive signaling may in part be mediated by mitochondria-generated thermal transients in TASK-channel-containing microdomains. Confocal microscopy measured distances between antibody-labeled mitochondria and TASK-potassium channels in primary rat CBSCs. Sub-micron distance measurements (TASK-1: 0.33 ± 0.04µm, n = 47 vs. TASK-3: 0.32 ± 0.03µm, n = 54) provided the first direct evidence for CBSC oxygen-sensing microdomains. Using a temperature-sensitive dye (ERthermAC), hypoxic-inhibition of mitochondrial oxidative phosphorylation in CBSCs was suggested to cause a rapid and reversible inhibition of mitochondrial thermogenesis and thus temperature in these microdomains. Whole-cell perforated-patch current-clamp electrophysiological recordings demonstrated CBSC sensitivity of resting-Vm to temperature: lowering bath temperature from 37°C to 24°C induced consistent and reversible depolarizations (Vm at 37°C: -48.4 ± 4.11mV vs. Vm 24°C: -31.0 ± 5.69mV; n = 5; p<0.01) in isolated, primary rat CBSCs. We propose that hypoxic inhibition of mitochondrial thermogenesis may play a critical role in hypoxic chemotransduction in the carotid body. A reduction in temperature within cellular microdomains will inhibit plasma membrane ion channels, influence the balance of cellular phosphorylation–dephosphorylation, and (open full item for complete abstract)

Committee: Christopher N. Wyatt Ph.D. (Advisor); Eric S. Bennett Ph.D. (Committee Member); Paula A. Bubulya Ph.D. (Committee Member); Kathy Engisch Ph.D. (Committee Member); Robert M. Lober M.D., Ph.D. (Committee Member) Subjects: Biomedical Research; Cellular Biology; Neurobiology; Neurosciences; Physiology

Master of Science, The Ohio State University, 2019, Animal Sciences

In recent years, a variety of muscle myopathies, specifically wooden breast, white striping, and deep pectoralis myopathy, have severely impacted the poultry industry. Although broilers have become more efficient at producing muscle mass, the rapid increase in growth has exceeded the structural limits of the muscle. As a result, myopathies such as wooden breast are commonly associated with fast-growing, heavy weight broilers. However, there is little genetic correlation with breast muscle yield, indicating that environmental factors likely play a vital role. Environmental factors such as nutrient restriction and thermal stress can alter satellite cell populations, which are a type of stem cell responsible for all post-hatch muscle growth. Changes in the satellite cells will have long-lasting impacts on muscle development and meat quality. Although there have been studies that have elucidated the independent effects of nutrient restriction and thermal stress, there is little information regarding the effect of a simultaneous temperature and nutritional restriction on satellite cells, specifically, immediately after hatch, when satellite cells are the most susceptible to environmental stressors. Since chicks are rarely exposed to a single stressor, it is important to understand how simultaneous environmental factors will impact long-term muscle growth. The effect of a simultaneous post-hatch feed restriction and thermal stress on skeletal muscle growth and meat quality was studied by applying a 20% feed restriction during the first week post-hatch. At the time of hatch broiler chicks were divided into either a 20% feed restriction group, or given ad libitum access to feed and held at an ambient temperature of 31°C, 35°C, or 39°C. Gene expression for satellite cell genes Paired Box Protein 7 (PAX7), Myogenic Factor 5 (MYF5), Myogenic Differentiation 1 (MYOD1), and Myogenin (MYOG), were measured at d 7, and no significant differences were detected (P > 0.25). Muscle fib (open full item for complete abstract)

Committee: Daniel Clark PhD (Advisor); Sandra Velleman PhD (Committee Member); Michael Cressman PhD (Committee Member); Sheila Jacobi PhD (Committee Member) Subjects: Agriculture; Animal Sciences

PhD, University of Cincinnati, 2000, Engineering : Materials Science

The overall objectives of this dissertation are fabrication of titanium diboride-colloidal alumina composite coating on carbon substrate, and study of the concerned properties of being used as a protective coating in Hall-Heroult cell. A unique aqueous suspension spraying coating procedure has been developed to apply thick (>1 mm) and crack-free TiB 2 coating on carbon substrate, in which colloidal alumina is initially used as the inorganic binder to avoid the drawbacks of carbonaceous additives. The processing parameters in coating application and densification such as composition of the suspension, coating thickness, sintering temperature and time are optimized to produce thick and crack-free TiB 2 coating with high electrical conductivity and high mechanical strength. General physical and mechanical properties of the coating material, such as density, porosity, electrical conductivity, micro-hardness and flexural strength are determined; Microstructure and morphology of this unique TiB 2 -colloidal alumina composite are characterized; Properties of interest for specific utilization as a protective coating in aluminum producing cell such as wetting behavior with molten aluminum are examined. Features associated with aqueous spraying coating process, such as viscosity of the suspension, drying behavior, critical cracking thickness, interfacial bonding strength and thickness of interfacial bonding region are determined. This dissertation also represents an extensive investigation on TiB 2 -colloidal alumina composite coating. The function of the nano-sized colloidal alumina is understood in terms of forming aid and sintering aid. Based on the intensive analysis of the experimental data, a pattern in which TiB 2 particles are coated by nano-sized colloidal alumina in the suspension is successfully postulated to explain the property dependence on colloidal alumina addition. The sintering process of TiB 2 -colloidal alumina composite coating is an energy activate proce (open full item for complete abstract)

Committee: J. Sekhar (Advisor) Subjects: Engineering, Materials Science

Master of Science, The Ohio State University, 2011, Geological Sciences

The viscosity of water is a first-order constraint on the transport of material from a subducting plate to the mantle wedge. The viscosity of fluids that are released during the dehydration of hydrous minerals during subduction can vary by more than 9 orders of magnitude between the limits of pure liquid water and silicate melts. Accurate determination of low viscosities (<1 mPa·s) for liquids at simultaneous high pressures (>1 GPa) and high temperatures (>373 K) is hindered by the geometry and sample size of high-pressure devices. Here the viscosity of water at pressures representative of the deep crust and upper mantle through use of Brownian motion in the hydrothermal diamond anvil cell (HDAC) is reported. By tracking the Brownian motion of 2.8 and 3.1 micron polystyrene spheres suspended in H2O, the viscosity of the water at high pressure and high temperature can be determined in situ using Einstein's relation. Accuracies of 3-10% are achieved and measurements are extended to pressures relevant to fluid release from subducting slabs and temperatures up to 150% of the melting temperature. Unhampered by wall effects of previous methods, the results from this study are consistent with a homologous temperature dependence of water viscosity in which the viscosity is a function of the ratio of the temperature to the melting temperature at a given pressure. Based on the homologous temperature dependence of water, transport times for fluids released from subducted plates inferred from geochemical proxies are too short for transport via porous flow alone, and suggest transport through a combination of channel-flow and porous flow implying hydrofracturing at 50-150 km depth.

Committee: Wendy Panero (Advisor); Michael Barton (Committee Member); David Cole (Committee Member) Subjects: Geophysics

Master of Science, The Ohio State University, 2010, Materials Science and Engineering

This study was performed to develop a method of removing molten process fluids, namely a ferrosilicon alloy and a complex silicate melt, from an electrolysis cell. The device was designed as a component of equipment used for an in situ lunar oxygen generating process under development. This work focuses on developing a system for integration into a molten regolith electrolysis cell, the products of which are highly reactive, making materials compatibility a primary concern of a materials handling system. This paper describes the design and operation of a mechanism utilizing a pressure differential to pull molten material from a furnace into a mold. The results of several different materials choices for equipment hardware are described and suggestions for modification of the device for improvement and lunar compatibility are made.

Committee: Doru Stefanescu PhD (Advisor); Yogeshwar Sahai PhD (Committee Member) Subjects: Aerospace Materials; Engineering; Geotechnology; Materials Science; Mining

Doctor of Philosophy, The Ohio State University, 2008, Chemical Engineering

Proton-exchange membrane fuel cells (PEMFCs) have become a very active research area for both mobile and stationary applications, particularly for fuel cell vehicles. Compared to inner combustion engines, PEMFCs can decrease pollution and increase the energy efficiency. New proton-exchange membrane (PEM) materials and new technologies for fuel processing are the most important and challenging parts in this research field.Nafion® and other perfluorinated sulfonic acid membranes are still the only commercial PEM materials so far. However, their high cost and low performance at high temperatures significantly limit their applications. In this research, new five-member ring and six-member ring soft segment-containing sulfonated polyimide (SPI)-based membranes and new sulfonated polybenzimidazole (SPBI)-based membranes were successfully synthesized. The resulting membranes could outperform Nafion® at various conditions, particularly at high temperatures and low relative humidities (RHs). Moreover, the new membrane materials should be much more cost-effective since the starting materials are more than two orders of magnitude less expensive than those for Nafion® membranes. In the research on fuel processing, amine carriers were successfully incorporated into the SPBI copolymer or the crosslinked poly(vinyl alcohol) (PVA) matrix, which could react reversibly with acid gases, such as CO2. Thus, the resulting membranes have shown very promising CO2 selectivity vs. the other gas molecules, such as H2 and CH4, by the facilitated transport mechanism. These newly synthesized membranes have many applications in the field of gas separations, including the low pressure synthesis gas purification for fuel cell applications, the high pressure synthesis gas purification for refinery industrial applications, and the high pressure natural gas purification to obtain high purity CH4.

Committee: W.S. Winston Ho PhD (Advisor); L. James Lee PhD (Committee Member); Kurt Koelling PhD (Committee Member); Isil Erel PhD (Committee Member) Subjects: Chemical Engineering; Energy; Polymers

Doctor of Philosophy, Case Western Reserve University, 2004, Chemical Engineering

The operation of the polymer electrolyte membrane fuel cell (PEMFC) at high temperatures (>120°C, preferably > 150°C) is desirable because of the enhanced catalyst activity, reduced poisoning effect of fuel impurities, simplification of the system, and easy thermal compatibility. After reviewing the recent development of high temperature polymer electrolyte membranes, and properties and applications of PBI membrane in PEMFC and other electrochemical systems, this work focuses on understanding fundamental properties of acid doped PBI membranes. Water uptake and proton conductivity of phosphoric acid doped PBI membrane studies are reported as a function of temperature, relative humidity and acid doping level. Membranes directly cast from PBI/TFA/acid solution show the presence of TFA at low acid doping levels (x≤2), which is replaced by H3PO4 progressively with increasing acid doping level. At low doping level, water molecules form hydrogen bonds not only with phosphoric acid species but also with PBI and TFA. At high doping levels, water molecules interact mainly with excess phosphoric acid in the amorphous phase of the membranes. The dependence of the conductivity on temperature can be interpreted with an Arrhenius equation. The excess phosphoric acid molecules interact with PBI mainly by hydrogen bonding. Proton transfer in this system occurs along different paths under different doping levels, RHs, and temperatures. In order to explore strategies and understand the rationales for approaches to acid doped PBI membranes having both high conductivity and high acid-retention capability, several acids have been investigated. The proton conductivity, chemical and thermal stability, and acid-retention capability have been investigated for all membranes. The proton conductivity of acid, related to its acidity, chemical structure and melting point, gives an upper limit of that of the acid doped PBI membrane. All membranes exhibit lower conductivity than phosphoric acid (open full item for complete abstract)

Committee: Robert Savinell (Advisor) Subjects: Engineering, Chemical

Master of Science, University of Akron, 2005, Chemical Engineering

The development of electrochemical converters (i.e. fuel cells) has attracted research interest during the last decades due to an increasing concern on the depletion of available fossil fuel reserves and environmental issues such as global warming and emission of pollutant gases. Solid oxide fuel cells have received special attention because of their higher energy efficiency, rapid electrode kinetics without using expensive electrocatalysts such as Pt, relative resistance to impurities in the fuel and the possibility of processing CO, CH4 and other Carbon based fuels. Extensive research efforts have resulted in the development of solid oxide fuel cell materials such as Yttria stabilized Zirconia (YSZ) electrolytes, Lanthanum or Calcium doped Strontium Manganite (LSM) cathodes and Ni-YSZ cermet anodes. YSZ electrolytes require high operation temperatures (~ 1000 °C) in order to achieve sufficient ionic conductivity, placing large restrictions to candidate electrode, interconnect and housing materials. As a result, the cost of solid oxide fuel cell systems has become an important factor preventing their commercialization. Recent research efforts have shown that a variety of samarium doped oxides can be used as electrolyte and electrode materials in order to develop solid oxide fuel cells operating in intermediate temperatures. Samarium doped Ceria (SDC) has been shown to possess sufficient ionic conductivity at intermediate temperatures (600-800 °C). iv Similarly, Strontium doped Samarium Cobaltite (SSC) has been shown to act as an active electrode material. During this study we developed a synthesis procedure in order to fabricate a samarium doped ceria electrolyte and a samarium strontium cobaltite electrode material. Different fabrication conditions were tested in order to elucidate a procedure to manufacture an intermediate temperature fuel cell using an SDC electrolyte and two SSC electrodes. The impact of several fabrication variables on the resulting fuel cell (open full item for complete abstract)

Committee: Steven Chuang (Advisor) Subjects: Engineering, Chemical