PhD, University of Cincinnati, 2023, Engineering and Applied Science: Environmental Engineering

Hydropower is a renewable, low-emission energy source that supplies electricity either in isolation or as a stable baseload to support other renewable energy sources such as solar and wind. As such, hydropower reduces the carbon emissions to the environment that would have been emitted if other non-renewable sources, such as the thermal combustion of fossil fuels, were used instead. Most of the greenhouse gas emissions associated with hydropower projects and dam construction are associated with the material used. Very few emissions are expected during the operation, making it a low-carbon-emission source compared to other alternative energy sources. Moreover, hydropower production is also associated with economic development. Globally, there is still potential for future hydropower development, and newer projects are planned, especially in South America, along with the Himalayan ranges, around the Mediterranean regions, and regions of West Africa. Developing new projects in these locations could uplift the local economy and support developmental activities at a low carbon cost supporting the goals of COP26. However, the global hydropower sector (existing and projected) relies upon surface water flows of sustainable and predictable volume, making it vulnerable to climate change. The natural hydrological cycle is disrupted by climate change resulting in changes in the volume, seasonality, and intensity of precipitation and, thus, the available streamflow. Moreover, the increase in temperature also leads to the loss of snow and glacier, which provide seasonal and permanent storage for hydropower projects in higher elevations. The secondary effects of climate change on glacier lake outbursts floods, landslides, and sediment load are poorly understood and often neglected in risk assessments. The overall impact of climate change on the hydropower sector is difficult to predict and not globally uniform. Individual (open full item for complete abstract)

Committee: Patrick Ray Ph.D. (Committee Chair); Amy Townsend-Small Ph.D. (Committee Member); Katherine Schlef Ph.D. (Committee Member); Steven Buchberger Ph.D. (Committee Member) Subjects: Environmental Engineering

Doctor of Philosophy (PhD), Ohio University, 2021, Chemical Engineering (Engineering and Technology)

One of the most challenge issues in oil and gas industry is the corrosion of pipeline materials caused by carbon dioxide (CO2) and hydrogen sulfide (H2S). The precipitation of corrosion product layers, their characteristics, composition, and kinetics, play a key role in governing corrosion behaviors. The present project is focused on one key aspect in understanding and modeling the effect of surface layers: the investigation of the precipitation kinetics of corrosion product on carbon steel, the most preferred construction material in the field. The study focuses as well on brines containing high concentrations of dissolved NaCl, a situation also commonly encountered in the oil and gas industry. The first part of the project aims at improving the accuracy in the determination of species concentration in CO2 and H2S aqueous environments. The consumption of ferrous ions due to the presence of chloride ions was addressed. Several expressions related to H2O/CO2 and H2O/H2S equilibrium speciation were updated based on literature data. A previously well accepted expression for iron carbonate (FeCO3) solubility limit was re-calibrated against experimental data to better account for salt concentration effects. A methodology was developed for using Electrochemical Quartz Crystal Microbalance (EQCM) for the study of precipitation kinetics of both iron carbonate and iron sulfide (FeS), as EQCM is a technique providing very accurate in-situ measurement of surface mass change. Repeatable and consistent precipitation rates of FeCO3 obtained via the EQCM across different substrates, temperatures, and sodium chloride (NaCl) concentrations suggest that increasing NaCl from 1 wt.% to 9 wt.% did not change the precipitation rate significantly. Based on the measurements, a kinetics model was proposed to describe the FeCO3 precipitation rate in CO2 environments with varied NaCl concentrations. For FeS, the inherent complexity of the system limited the scope of the (open full item for complete abstract)

Committee: Marc Singer (Advisor); Srdjan Nesic (Committee Member); Katherine Fornash (Committee Member); Howard Dewald (Committee Member); John Staser (Committee Member) Subjects: Chemical Engineering

Bachelor of Arts (BA), Ohio University, 2021, Environmental Studies

Billions of dollars are invested annually in stream restoration in the United States. However, three centuries of landscape modification have fundamentally altered riverine ecosystems, and some current widespread stream restoration methods do not account for this. The restoration projects studied in this project removed legacy sediments and regraded the streams and banks to achieve a more historically accurate stream system, an anastomosing wetland-stream complex. This project analyzed historical water depth and precipitation data to determine the effect of the restoration on the hydrology of the system. A significant difference in the relationship between water depth and precipitation at all study sites pre-restoration to post-restoration was found. It was also found that post-restoration, rainfall led to a lesser increase in water level than pre-restoration, suggesting that floodplains were saturated and peak velocity was lowered, thus lowering erosion potential. Stream restoration methods should adjust their focus from aesthetic improvement to improvement ecological function and recreate streams as we now know they existed historically.

Committee: Natalie Kruse Dr. (Advisor) Subjects: Environmental Engineering; Environmental Science; Environmental Studies; Hydrologic Sciences; Hydrology; Water Resource Management

Master of Science (MS), Ohio University, 2019, Environmental Studies (Voinovich)

Although acid mine drainage (AMD) in the Appalachian Coal Basin has been studied for decades, the effects of climate change on these streams are not well documented. Climate change predictions for this area include increased storm frequency and intensity, which may alter AMD generation, iron hydroxide precipitation, and fate and transport of contaminants and sediments. These processes substantially affect nutrient availability and the biological communities inhabiting these streams. This study investigates the potential effects of climate change on a treated AMD stream, Hewett Fork, by quantifying changes in nutrient concentrations, sediment transport, and algal biofilm biomass during normal and storm conditions. Nitrate, sulfate, and total reactive phosphorous concentrations were measured during each sampling event. Sediment transport was measured by quantifying sediment deposition and total suspended solids (TSS). The biological response to these conditions was measured by comparing algal biofilm biomass, quantified as chlorophyll a concentration, on stream rocks. Coupled with long-term meteorological, discharge, and chemistry data, the results of this study were used to create two conceptual models of Hewett Fork's behavior during normal and storm conditions, respectively. Antecedent precipitation index (API) was used as an indicator of runoff potential to analyze the effects of recurring storm events on stream behavior. As API increased during normal and storm events, TSS concentrations increased, while chlorophyll a, conductivity, and sulfate concentrations decreased. TSS, nitrate concentration, and sediment deposition were higher overall during storm events. Total reactive phosphorous concentration remained low at all sites during the sample period, indicating that Hewett Fork may be phosphorous-limited. The results of this study indicate land use, mining, and treatment systems may contribute to lasting negative impacts on the biological community of Hewett Fo (open full item for complete abstract)

Committee: Natalie Kruse PhD (Advisor); Morgan Vis PhD (Committee Chair); Dina Lopez PhD (Committee Chair) Subjects: Biology; Ecology; Environmental Management; Environmental Science; Environmental Studies; Geochemistry; Hydrologic Sciences; Water Resource Management

Master of Science (MS), Ohio University, 2017, Environmental Studies (Voinovich)

Limited biological recovery in acid mine drainage (AMD) impacted streams may be due in part to a flushing response caused by rainfall events. While there is very little water required to react with sulfide minerals to form AMD, more is required to dissolve and transport the chemical products. Increased discharge allows for the transport of accumulated reaction products from mineral surfaces and mobilization of sediments from streambeds. The objective of this study was to investigate this flushing behavior in the heavily AMD impaired Hewett Fork Watershed by tracking the changes in water chemistry over the course of multiple rain events and seasonal flow regimes. Hewett Fork is located within Athens County, Ohio, and is currently treated by an active remediation system. This study utilized two auto-samplers, at two field sites along the same stream gradient of impairment, to allow for the collection of hourly water samples during selected storm events in spring, summer, and fall. The collected water samples were then analyzed for total concentrations of a large suit of metals, sulfate, acidity, and alkalinity. Results show how the geochemistry is changing within Hewett Fork during precipitation events. Analysis of these changes in water quality revealed response patterns of each monitored constituent allowing them to be grouped by their dominant response pattern. The constituents also displayed seasonal patterns that showed large flushing events in the spring and fall seasons. It remains unclear if these flushing events have limited the biological recovery in Hewett Fork. Further studies should be conducted to better understand the varied and complex responses of the geochemistry in AMD impacted watersheds during precipitation events to properly manage and treat this prolific non-point source pollution.

Committee: Natalie Kruse (Committee Chair); Dina Lopez (Committee Member); Kelly Johnson (Committee Member) Subjects: Environmental Geology; Environmental Management; Environmental Science; Environmental Studies; Geochemistry; Hydrologic Sciences; Hydrology; Water Resource Management

Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, University of Akron, 2024, Integrated Bioscience

The scientific reciprocity of environmental geomicrobiology and biotechnology harnessing microbially induced carbonate precipitation (MICP) is epitomized by cave speleothem research; delineating environmental conditions uncovers factors that inform the development of industrial bacteriogenic mineralization processes, with greater control over the end products. Reconciling bacterial metabolism and CaCO3 precipitation has the potential to recontextualize geological precipitation events as microbial byproducts, warranting interdisciplinary investigation. In Wind Cave, South Dakota, I identified a complex weave of speleoclimatic, geochemical, and microbiological dynamics that controls the materialization and polymorphism of CaCO3 secondary deposits known as frostwork. Microclimatic monitoring and analysis suggested an evaporative environment, modelled from detailed temperature, humidity and airflow data. Airflow measurements support a causal link between cave wind directionality and the occurrence of frostwork. Sequential deposition of carbonate phases characterizes bulk frostwork formations according to shifting Mg2+/Ca2+ ratios over the speleothem lifetime, yielding multiaggregate formations consisting of calcite, aragonite, hydromagnesite, dolomite, opal, and smectite. Thin sections showed diagenetic fabrics indicative of oscillating supersaturation conditions in response to surface seasonal climatic changes. Scanning electron microscopy (SEM) analyses identified frostwork's aragonite crystal topography as a microecological niche supporting filamentous Actinomyces bacteria, leaving room for a microbial component to Wind Cave frostwork development. To begin to monitor the impact of factors controlling crystal growth in vitro I developed two parallel techniques for measuring bacteriogenic carbonate precipitation in Escherichia coli cultures, using i) image analysis for agar media, and ii) inductively coupled plasma–optical emission spectroscopy (ICP-OES) ion quantifica (open full item for complete abstract)

Committee: Hazel Barton (Advisor); John Senko (Committee Member); Andreas Pflitsch (Committee Member); Bogdan Onac (Committee Member); Brian Bagatto (Committee Member) Subjects: Biology; Geobiology; Microbiology; Mineralogy

Doctor of Philosophy (PhD), Ohio University, 2024, Mechanical Engineering (Engineering and Technology)

This work evaluates the geochemistry between the Utica-Point Pleasant (UPP) shale and associated connate fluids under simulated reservoir conditions in a batch reactor system with a primary focus on identifying precipitate formation. Preliminary studies were performed to identify and characterize precipitation formation under simulated reservoir conditions. The formation of iron-based precipitate was evident through results from fluid and material analyses. Fe2+ was the predominant iron form found in the aqueous phase, with oxidation to Fe3+ and subsequent precipitate formation. Geochemical modeling further supported that Fe3+ was the favorable species for precipitation. Furthermore, this work evaluated a deeper comprehension of the impact of citric acid and sodium gluconate on the kinetics of iron oxidation and precipitation within the UPP formation. Zeroth- and first-order kinetic models were applied to experimental data acquired at 37, 57 and 77 °C (98.6, 134.6 and 170.6 °F) to determine reaction rates, activation energy and pre-exponential factor. It was found that zeroth-order kinetics were a better fit for the system and used as the kinetics basis for additional analysis in the study. Additionally, subsequent trials were performed to evaluate the effect of the iron control agent. Results from these trials indicate that citric acid effectively diminishes iron precipitation by exerting a chelating influence on Fe3+, with the chelation effect becoming more pronounced as the concentration of citric acid is increased. Sodium gluconate also demonstrated effectiveness as an iron control agent, inhibiting the oxidation of Fe2+ when present in the solution. No residual Fe3+ was observed in the solution for either of the sodium gluconate trials, suggesting that its chelation capability is notably lower compared to that of citric acid. It is suggested that the most effective iron control strategy for the UPP formation would involve a combination of sodium gl (open full item for complete abstract)

Committee: Jason Trembly (Advisor); Muhammad Ali (Committee Member); David Drabold (Committee Member); Martin Kordesch (Committee Member); David Young (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 1985, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2024, Welding Engineering

Welding low alloy steels can result in formation of undesirable properties in the heat affected zone with high hardness and low toughness caused by martensite formation. Such issues often require tempering procedures to improve properties and reduce cracking susceptibility. The temper bead welding technique has been applied by the power generation industry to produce tempered heat affected zones without post-weld heat treatment. The development of good temper bead procedures can be cumbersome which served as motivation for a portion of the work in this study. This research contained four elements focused on performance of low alloy steel heat affected zones after temper bead welding. These included development of an experimental and computational approach to evaluate tempering response and tempering efficiency, application of the developed methodologies using a finite element model-based design of experiment approach, characterization of the effect of short-term tempering reheats on impact properties, and evaluation of the precipitation kinetics during short-term tempering reheats. The tempering response quantification method was developed to quantify the tempering effect of the multiple non-isothermal cycles during multi-pass welding processes. A novel computational framework was developed to evaluate and quantify the tempering response and tempering efficiency in the heat affected zone in temper bead welding. This involved integrating finite element models with the tempering response methodology to allow distribution analysis of hardness, microstructure, corresponding surface areas, and other tempering response indicators. These methodologies were demonstrated and validated in temper bead weld overlays on Grade 22 steel. Efforts to facilitate temper bead procedure optimization motivated development of a computational finite element model-based design of experiment framework to evaluate a range of weld process parameters and tailor procedures to optimize perfor (open full item for complete abstract)

Committee: Boian Alexandrov PhD (Advisor); Avraham Benatar PhD (Committee Member); Carolin Fink PhD (Committee Member) Subjects: Materials Science

Master of Science, The Ohio State University, 2024, Civil Engineering

Hurricanes frequently bring intense and heavy rainfall, which compound with storm surge and contribute significantly to their overall impact. Current models assume these events as disjoint, which leads to underestimation of flooding that consequently occurs. Our research aims to bridge this gap by integrating two parametric rainfall models — the R-CLIPER (Rainfall CLImatology and PERsistence) and IPET (Interagency Performance Evaluation Task Force Rainfall Analysis) models — into an existing Discontinuous Galerkin Shallow Water Equation Model (DG-SWEM). Firstly, we aim to showcase the effectiveness of the R-CLIPER and IPET models in replicating observed rainfall patterns. To do this, we will use Quantitative Precipitation Forecast (QPF) indices to check how well these models match observed rainfall patterns around the center, around the mean and distributed volumes and around extreme precipitation values. Subsequently, we will integrate these models into the DG-SWEM storm surge framework.Our hypothesis is: Incorporation of rainfall into an existing storm surge model will enhance its ability to predict the flooding that follows hurricanes.To test this hypothesis, we evaluate the performance of DG-SWEM with and without the inclusion of rainfall for 6 storms at available United States Geological Survey (USGS) high water marks. The results clearly demonstrate that the inclusion of rainfall can indeed improve compound flood simulations.

Committee: Ethan Kubatko (Advisor); Andy May (Committee Member); Jim Stagge (Committee Member) Subjects: Civil Engineering; Environmental Engineering

Doctor of Philosophy (PhD), Ohio University, 2024, Chemical Engineering (Engineering and Technology)

The imperative to mitigate environmental degradation from the direct application of animal wastewater and the rising costs of commercial fertilizers has spurred the exploration of nutrient recovery through electro-precipitation, focusing on producing solid fertilizer efficiently. In the first study, an investigation on the electrochemical treatment of synthetic animal wastewater at initial pH levels of 5.9 and 6.6 discovered that pH 6.6 favored higher phosphorus recovery rates and proved more energy efficient. Analysis of solid byproducts through scanning electron microscopy and energy-dispersive X-ray spectroscopy highlighted the co-precipitation of struvite and brushite incredibly efficiently at the higher pH level. This pH-dependent outcome suggests the potential for tailored nutrient recovery strategies in waste management. In the second study, the focus shifted to multivariate screening analyses using the Plackett-Burman design on Synthetic Animal Wastewater (SAW) with an initial pH of 6.6 to discern the effects of temperature, cathodic potential, turbulence, and ion concentration on nutrient removal from wastewater. The Mg:Ca molar ratio was identified as the most significant factor in phosphorus recovery. The findings emphasized that controlling the Mg:Ca ratio, temperature, and N: P ratio could yield competitive energy consumption with existing industrial methods. The preference for struvite formation at lower temperatures indicated temperature's critical role in nutrient recovery optimization. In the third study, response surface methodology (RSM) and artificial neural networks (ANN) were combined to optimize phosphorus recovery from synthetic animal wastewater (SAW). The combination of a multi-layer feed-forward network and Box-Behnken design enabled the approach to be adapted to various environmental and wastewater scenarios. The dual-model system accurately forecasted the recovery efficiency, substantiated by significant R2 values and minimal root (open full item for complete abstract)

Committee: Jason Trembly (Advisor); Damilola Daramola (Committee Co-Chair); John Staser (Committee Member); Howard Dewald (Committee Member); Natalie Kruse Daniels (Committee Member) Subjects: Chemical Engineering; Environmental Engineering; Sustainability

Doctor of Philosophy, The Ohio State University, 2024, Materials Science and Engineering

Shear deformations in metallic materials, whether carried by dislocations, mechanical twinning, martensitic transformations in crystalline solids, or shear transformation zones (STZs) in amorphous solids, exhibit several common characteristics. These include autocatalysis driven by long-range elastic interactions and the occurrence of strain avalanches post-yielding. Therefore, to achieve controlled strain release and desired stress-strain behaviors tailored to specific applications, it is imperative to mitigate autocatalysis. In this dissertation, we elucidate strategies to mitigate autocatalysis by focusing on three commonly used metallic materials: Al alloys, extensively employed as lightweight structural materials in manufacturing; NiTi shape memory alloys (SMAs), widely utilized in aerospace, automotive, and biomedical industries; and metallic glasses, utilized in precise instruments and biomedical devices. The primary aim is to employ various computational methods to investigate mechanisms for suppressing autocatalysis and attaining desired mechanical responses in these three examples through appropriate microstructure engineering. In Al-alloys, dislocations are the primary carriers of shear deformation and various precipitate microstructures have been strategically designed to regulate the dislocation activities. In particular, in 7xxx series Al-alloys, e.g., Al-Zn-Mg-Cu, η' phase is the commonly observed shearable precipitate phase to strengthen the alloys. By adding Mn and Si, non-shearable precipitates (Al6Mn and α) have been introduced to prevent stain localization. To understand the synergy between the two types (shearable and non-shearable) of precipitates in achieving desired combinations of strength and ductility, it is necessary to investigate the possible interactions between the two during precipitation. These interactions determine the precipitate microstructures, as well as the interactions between a given precipitate microstructure and dislocat (open full item for complete abstract)

Committee: Yunzhi Wang (Advisor); Steve Niezgoda (Committee Member); Michael Mills (Committee Member) Subjects: Materials Science

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Materials Science

As super-saturated solid solutions of Al-Mg, 5XXX series aluminum alloys are susceptible to sensitization via intergranular precipitation of the anodic ß-phase, which promotes intergranular corrosion, exfoliation and stress corrosion cracking under environmental conditions. This deleterious process occurs at time and temperature scales that eventually impact most structural applications over the course of multiple decades. Efforts to better control sensitization in these alloys, or establish predictive models, have historically been hampered by the large inter-lot variations found between nominally identical material produced by different suppliers, as the starting microstructure and total rolling reduction are not adequately specified by current cold-rolled plate tempers. The work in this dissertation demonstrates that the sensitization response of these alloys can be approached as a combination of two independent contributions: the geometric configuration of grain boundaries passing through the microstructure that are most prone to sensitization, and the rate that these boundaries sensitize due to the formation of the ß-phase. The sensitization rate kinetics of the most susceptible boundaries can be modeled using a modified Johnson-Mehl-Avarami-Kolmogorov (JMAK) theory based approach, as applied to the impinging locally sensitized regions surrounding discrete ß-phase precipitates. The microstructural configuration manifests as a sample-dependent linear scaling factor in the sensitization response. The JMAK model describes the kinetics of sensitization with excellent accuracy across all data available in the literature. This work demonstrates through the JMAK sensitization model that a clear change in the ß-phase nucleation and growth kinetics in these alloys can be observed above 100°C, and the kinetic constants both above and below that temperature can be accurately fitted. The results of the model importantly imply that sensitization at environmental temp (open full item for complete abstract)

Committee: Matthew Steiner Ph.D. (Committee Chair); Sarah Watzman Ph.D. (Committee Member); Ashley Paz y Puente Ph.D. (Committee Member); Dinc Erdeniz Ph.D. (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2023, Chemical Engineering

The biopharmaceutical market has seen tremendous growth over the past few decades as new recombinant proteins, monoclonal antibody-based therapeutics and gene therapies have been commercialized. After production in different mammalian, yeast and microbial expression hosts, each product must be concentrated and highly purified before clinical use. Protein A affinity methods provide a convenient and widely used platform for capturing and purifying monoclonal antibodies (mAbs), Fc-fusion proteins, antibody drug conjugates (ADCs) and bispecific antibodies (BsAbs). In this work, an attempt has been made to develop novel Protein A affinity ligands having higher binding capacity than the ligands on commercial resins. There is currently no similar platform technology for purifying increasingly important non-mAb protein therapeutics. Protein therapeutics such as single domain antibodies, single chain variable fragments, Fab fragments, interferons, epoetins, clotting factors, growth factors, insulin and insulin like analogues, enzymes etc. have traditionally been purified using multiple column steps based on ion exchange, hydrophobic interaction, mixed mode, and ceramic hydroxyapatite chromatography. These multicolumn approaches require significant optimization and often result in low product yields and recoveries. Thus, scalable and cost-effective alternatives to these currently used approaches are needed. Furthermore, these alternative methods should be convenient to use and allow for easy technology transfer between clinical drug discovery, process development and manufacturing. In this work, we propose the use of pH-sensitive self-removing affinity tags as a potential solution. Purification strategies based on self-removing and self-precipitating tags have been developed previously for laboratory scale protein purification. However, these methods utilize pH sensitive contiguous inteins which suffer from premature cleavage, resulting in significant product loss during p (open full item for complete abstract)

Committee: David Wood (Advisor); Eduardo Reategui (Committee Member); Jeffrey Chalmers (Committee Member) Subjects: Biochemistry; Chemical Engineering

MS, Kent State University, 2023, College of Arts and Sciences / Department of Geography

The Colorado River supplies water for over 40 million people throughout the North American Southwest, a region that has experienced prolonged stress on water resources for more than two decades. Through the lens of critical physical geography, this research synthesizes a physical and social science approach to explicate the many human and physical distinctions that are fueling the overuse of this waterway. The Southwest region economically benefits from settler colonialism yet lacks inclusivity of access to natural resources, including water. An investigation into the intricate dynamics of land use, water policy, and climate change in the Colorado River Basin provides a holistic understanding of environmental and climate disparities gripping parts of the region. Mixed-methods consisting of a correlation and trend analysis, along with a policy analysis, were employed to identify these evolving issues. Hydroclimatological patterns over the 1956-2022 period reveal disconcerting trends, further aggravating water supply. Historical water policies from 1922-1968 demonstrate their misalignment with evolving river dynamics and contribute to inequities in resource allocation. By extracting historic to modern-day climate and adaptation data, the evidence of this study leads to the conclusion that previous and modern-day policy not only is unsuitable to withstand the future of climate-induced changes to the hydrologic health of the river, but the impact of water scarcity faced by Indigenous communities across the North American Southwest could persist. The study emphasizes the ongoing importance for policies to be more attuned to the shifting climate and landscape while ensuring equitable resource access for all.

Committee: Chris Post (Advisor); Scott Sheridan (Committee Member); Rebecca Parylak Ruthrauff (Committee Member) Subjects: American History; Climate Change; Environmental Justice; Environmental Studies; Geography; Hydrology; Land Use Planning; Public Policy; Water Resource Management

Master of Science (MS), Ohio University, 2023, Chemical Engineering (Engineering and Technology)

Considering the volumetric capacity and composition of WWTPs effluent in the United States, there is a significant potential for phosphorus recovery (an important macronutrient necessary for plant growth) to promote environmental sustainability. This project aimed to investigate struvite (a phosphate compound) production potential from municipal wastewater and the influence of magnesium on electrochemical phosphorus recovery. Wastewater effluent was collected biweekly for one year from two WWTPs in Ohio and analyzed for its composition. The result of this analysis together with Ohio corn fertilizer requirement was used to estimate struvite production potential from these plants. In the next step, magnesium concentration was varied in synthetic wastewater based on municipal wastewater chemistry to study its effect on electrochemical phosphorus recovery. The result shows that the Southerly Columbus WWTP alone can serve 5% of Ohio corn field phosphate requirement at 80% phosphorus recovery. Also, electrochemical phosphorus recovery using sacrificial Mg alloy achieved almost 100% recovery of P compared to 11%, seen with a 3:1 Mg to P molar ratio using MgCl2 as the magnesium source.

Committee: Jason Trembly (Advisor); Damilola Daramola (Committee Member); Jared DeForest (Committee Member); Natalie Kruse Daniels (Committee Member) Subjects: Chemical Engineering; Environmental Engineering; Sustainability

Doctor of Philosophy, The Ohio State University, 2023, Welding Engineering

Duplex stainless steels (DSS) are extensively used in heavy industry, such as Oil and gas, pulp and paper, and chemical, due to their remarkable corrosion resistance, yield strength, and toughness. The most corrosion-resistant DSS subgroups, super duplex stainless steels (SDSS) with Pitting Resistance Equivalent numbers (PREn) of 40-48, and the hyper duplex stainless steels (HDSS) with a PREn over 48, are highly alloyed. Additions of Cr and Mo provide better PREn but also promote intermetallic phases such as the chi and sigma phases. These intermetallics form when the material is exposed to temperatures between 600oC – 1100oC. It is known that even small volumetric fractions of the sigma phase severely reduce the material's corrosion resistance and mechanical performance. A dedicated study on sigma phase formation kinetics was developed to control sigma phase presence in these specific alloys. A field studied but not yet completely connected between scientific research and industrial applications. Fundamental aspects of sigma phase kinetics were analyzed, computationally modeled, and experimentally validated. As a result of these efforts, the interface area per unit of volume was revealed as a critical microstructure factor for the sigma phase kinetics. The resultant model's efficacy was further evaluated by building GTAW cladded mockups, and investigation into this material's mechanical and corrosion performance further expanded on the impacts of the sigma phase. A Gleeble® system was used to develop experimental time temperature transformation (TTT) maps on SDSS and HDSS filler metals for sigma phase precipitation kinetics. Classical nucleation theory was then implemented on the CALPHAD-based kinetics model. In this model, the interfacial energy and nucleation sites were identified as the kinetics parameters to adjust the model based on experimental data. The sigma phase kinetics continuous cooling transformation CCT curves were calculated using the additiv (open full item for complete abstract)

Committee: Antonio Ramirez (Advisor); Stephen Niezgoda (Committee Member); Carolin Fink (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2022, Materials Science and Engineering

In the last 20 years, research in magnesium alloys has greatly expanded with demand for high-strength lightweight alloys in the transportation industry. Mg-RE (rare earth) alloys have been of particular interest due to the formation of two strengthening phase types: long period stacking order (LPSO) phases and β-series precipitates. This work focuses on the development of high-strength cast Mg-RE multicomponent alloys that combine LPSO and β-series phases using a CALPHAD (CALculation of PHAse Diagrams)-based design approach. This work began by using CALPHAD modeling to study the effects of maximizing the LPSO phase fractions. Experimental samples demonstrated there was a slight increase in mechanical properties with high LPSO volume fractions, but the properties were below those obtained through β' precipitation in the commercial alloy WE43 (Mg-4Y-3.4RE-0.7Zr, all in wt%). It was also found that the CALPHAD model was underpredicting the LPSO phase fractions by ~20 vol%. Improvements were made to the Pandat database to bring the predictions within ~5 vol% of experimental values. In the second stage of this work, small-angle scattering (SAS) was used to quantitatively explore the effects of micro-alloying in the Mg-Nd system on β-series precipitates. Two SAS techniques were used in addition to transmission electron microscopy (TEM) to study the effects of micro-alloying: small-angle neutron scattering (SANS) and small-angle x-ray scattering (SAXS). It was found SAXS was a better technique to quantify the change in precipitate size with micro-alloying and aging, but more understanding of the system is needed to extract phase fraction changes. In the final stage of this work, the LPSO and β-series strengthening mechanisms were combined in an attempt to produce an Mg-Y-Nd-Zn-Zr alloy with properties superior to WE43. Nd does not form any LPSO phase, so there is less competition between the phases during formation. CALPHAD modeling is used to tailor the phase fracti (open full item for complete abstract)

Committee: Alan Luo (Advisor); Steve Niezgoda (Committee Member); Jenifer Locke (Committee Member) Subjects: Engineering; Materials Science

Doctor of Philosophy, The Ohio State University, 2022, Materials Science and Engineering

High level waste (HLW) in the form of spent fuel, transmutation and fission products exists as a legacy of wartime and cold war innovation and its safe disposal presents economic, environmental and societal consequences. Vitrification, which involves immobilization of HLW in a borosilicate glass matrix by processing in melters, is the current plan for most countries for disposal although crystalline ceramic waste forms will be used for radionuclides that are not efficiently processed in glass. This vitrified HLW, encased in stainless steel (SS) canisters, will be emplaced in a mined geological repository, where it is expected that over ~106 years, the radioactivity would drop to benign levels. It is imperative to be cognizant of the dissolution mechanisms of such waste forms for accurate prediction of long-term behavior since aqueous species are expected to interact with the waste forms. Their dissolution is expected to be enhanced by the localized corrosion of the nearby SS canister. The first part of our study involves the interactive corrosion between International Simple Glass (ISG), a model borosilicate waste glass, and SS 316. The two materials, placed in intimate contact were exposed to 0.6 M NaCl solution, with and without dissolved silica, for up to 365 days. Corrosion of SS was observed in 0.6 M NaCl with large pits located close to the crevice mouth suggesting that SS crevice corrosion would continue to propagate, driving the dissolution of ISG in a localized manner. The corrosion of SS is suppressed in silica-saturated solution. Irrespective of solution chemistry, the dissolution of ISG was demonstratively enhanced in the presence of SS, driven primarily by the aggressive local solution chemistry at the interface of the two materials. In the second part of this study, we examine the effect of four different electrolytes, viz. NaCl, Na2SO4, NaF and CsCl, of fixed concentration on the dissolution of ISG and compare it with deionized water (DIW). All soluti (open full item for complete abstract)

Committee: Gerald Frankel (Advisor); Jie Lian (Committee Member); Sheikh Akbar (Committee Member); Narasi Sridhar (Committee Member) Subjects: Chemistry; Engineering; Geochemistry; Materials Science