Doctor of Philosophy (PhD), Wright State University, 2019, Environmental Sciences PhD

Chlorinated hydrocarbons (CHCs) in groundwater can be treated by monometallic and bimetallic metal reductants through abiotic degradation. The breakdown of CHCs is achieved by gaining electrons from those reductants and removing chlorines from CHC molecules to transform the CHCs into less chlorinated compounds. This study explored the abiotic degradation of selected CHCs by zero valent magnesium Mg0 and bimetallic Cu/Mg reductant. Results showed that zero valent Mg0 was not effective in the treatment of carbon tetrachloride (CT), chloroform (CF) and dichloromethane (DCM). In contrast, the presence of Cu in Cu/Mg bimetallic reductant significantly accelerated the degradation kinetics. Degradation kinetics were observed to decrease with time, perhaps due to particle aging. The effect of Cu loading on degradation of the above compounds was also evaluated. Increasing Cu loading yielded faster degradation rates. No significant effect of Cu loading on the extent of CHC degradation was observed. CF degradation with Cu/Mg was promoted by acidic conditions. Methane (CH4), a desirable end product, was only formed as the major byproduct in CT and CF degradation by Cu/Mg bimetallic reductant. The higher yield of CH4 from CT or CF indicated that the complete reduction pathway was more significant compared with the hydrogenolysis pathway in degradation by Cu/Mg bi-metallic reductant. Instead of relying solely on surface water or groundwater sources, potable reuse of treated wastewater is becoming an increasingly common option for bolstering water resource portfolios in water-scarce regions. However, the concern over emerging trace contaminants that persist through wastewater treatment needs to be addressed to evaluate the potential risks of wastewater reuse. Poly- and perfluoroalkyl substances (PFASs) are used in a wide range of industrial and commercial applications, and are emerging contaminants posing a threat to safe drinking water. The information about their presence in re (open full item for complete abstract)

Master of Science (MS), Ohio University, 2017, Industrial and Systems Engineering (Engineering and Technology)

This thesis proposes to plan a degradation-based burn-in test for light display devices with two-phase degradation patterns by using Bayesian approach. The main focus of the burn-in test concerned in this study is to eliminate the initial rapid degradation phase, and a hierarchical Bayesian bi-exponential model is proposed and applied to define the two-phase degradation patterns of the burn-in population. Measurement uncertainty is the main focus of the burn-in test. Measurement uncertainty is an important factor during degradation observation of the burn-in population. The expected degradation path cannot represent the same as the observed degradation path. Warranty duration can also affect the optimal burn decisions. Mission reliability and expected cost criterions are considered with the available pre-burn-in data of a plasma display panel (PDP) example. To make the optimal burn-in decision, a cost optimization (minimization) model is developed for this thesis.

Doctor of Philosophy, Case Western Reserve University, 2017, Macromolecular Science and Engineering

Since CH3NH3PbI3 based perovskites were discovered as viable active materials for the next generation photovoltaic devices, their instability in different environmental conditions has been a constant challenge. In pursuit of a better understanding of the degradation mechanisms, perovskite solar cells have been fabricated and investigated by scientists in order to find correlations between the solar cell characteristics/performance and the interface variation. In this thesis, the perovskite reactivity to humidity is studied by exposing samples to D2O environment for different durations. The degradation process of CH3NH3PbI3 perovskite is examined in-situ by using time-of-flight secondary ion mass spectrometry (ToF-SIMS). 3D images are constructed through the layer-by-layer spatially resolved elemental distribution analysis and the D2O moisture penetration through the sample. The intermediate products of interaction with moisture are analyzed by ToF-SIMS and X-ray photoelectron spectroscopy (XPS). We also investigated the electrical operation-induced degradation on CH3NH3PbI3 perovskite solar cells. Upon exposure to electrical current, the structure and composition were examined by combining depth-resolved imaging with ToF-SIMS, XPS and field-emission scanning electron microscopy (FE-SEM). The results show that the interface of the perovskite and the meso-porous TiO2 intermix into each other during the initial operations of solar cell. This intermixing turns the efficiency upward and improves the power conversion efficiency (PCE) up to ~50%. Both depth profiles and SEM images proved that operating devices undergo irreversible changes in thickness, which results in a dramatic performance loss eventually. In addition to studying the degradation process of the perovskite, a new formation method was developed to achieve complete conversion of PbI2 to CH3NH3I3 on FTO/Compact TiO2 substrate by employing a quaternary ammonium salt as an additive in the PbI2 solution. Thi (open full item for complete abstract)

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

In this research, we develop an innovative approach to assessing the reliability of complex engineering systems, which are typically characterized by multiple interdependent performance characteristics (PCs). Recognizing that the degradation of these PCs often follows a positive, increasing trend, we employ the gamma process as the foundational model for degradation due to its properties of independent and non-negative increments. A critical aspect of our model is the incorporation of random-effect bivariate Gamma process degradation models, which utilize a variety of copula functions. These functions are instrumental in accurately modeling the dependency structure between the PCs, a factor that significantly influences the overall system reliability. In conventional degradation modeling, fixed and predetermined failure thresholds are commonly used to determine system failure. However, this method can be inadequate as different systems may fail at varying times due to uncontrollable factors. Our model addresses this limitation by considering random failure thresholds, which enhances the accuracy of predicting when a system might fail. We implement a hierarchical Bayesian framework for the degradation modeling, data analysis, and reliability prediction processes. This approach is validated through the analysis of a practical dataset, demonstrating the model's applicability in real-world scenarios. Furthermore, our study responds to the increasing market demand for manufacturers to provide reliable information about the longevity of their products. Manufacturers are particularly interested in the 100p-th percentile of a product's lifetime distribution. Degradation tests are vital for this, as they offer insights into the product's lifespan under various conditions over time. Utilizing our proposed model, we propose a method for designing degradation tests. This method optimizes the number of systems to be tested, the (open full item for complete abstract)

PhD, University of Cincinnati, 2017, Engineering and Applied Science: Environmental Engineering

Disinfection by products (DBPs) resulted from the reactions between the chlorine and natural organic substances which increased the formation of trihalomethanes (THMs). DBPs are carcinogens or have been known to cause health risks. Chloroform (CF) is the most abundant of all THMs with a maximum contaminant level (MCL) of 0.070 mg/L. In addition, CF and other THMs could also originate from sources other than by-products of water disinfection. Several physical and chemical removal methods are used to treat chloroform, which are expensive and could generate secondary pollutants. Biofiltration is one of the most proven technologies for volatile organic compound (VOC) control as it is environment–friendly, cost effective and releases fewer byproducts. In this study, an integrated technology was proposed. The integrated technology consists of nitrogen or air stripping followed by anaerobic or aerobic bio-trickling Filter (BTF). This study evaluated first CF only and secondly mixtures of THMs (CF and dichlorobromomethane (DCBM)). A co metabolite (ethanol) and surfactant (Tomadol 25 – 7) have been used to improve the biodegradation process. In addition, surfactin a bio surfactant was seeded within the BTF and its effectiveness has been investigated. Finally, microbial analysis was conducted to determine the dominant and responsible microbes for the BTFs performance.

Master of Science, University of Toledo, 2017, Chemical Engineering

Polyethylene Terephthalate (PET) is an industrially important polyester due to its properties. Because of PET's resistance to degradation in nature, mechanical recycling have been in practice. The Recycled PET(R-PET) has a lower Molecular Weight (MW) and Intrinsic Viscosity (IV) than virgin PET because of degradation of PET during the recycling process. With increasing demand for high performance PET in packaging industry several oxygen barrier additives have been introduced to PET. Polyamide MXD6 is one such additive, which is commercially available, and, the effect of it on the recycling process and recycled product properties are not well established. The purpose of this study was to determine the impact of MXD6 on the structure and properties of mechanically recycled PET blends. A series of pure PET, pure MXD6 and PET/MXD6 (95/5 wt.%) blend samples were prepared and recycled up to 3 times using a twin screw extruder to simulate multiple recycling process in the lab scale. Physical and structural properties of the recycled products were characterized using different methods such as DSC, FTIR, TGA, Solution and Melt Viscosity. The results showed that adding MXD6 results in lower IV of the R-Blend compared to the R-PET (37% comparing to 23% after 3 recycling step respectively). Moreover isothermal and dynamic crystallization kinetic studies showed that MXD6 increases the crystallization kinetics of the blend. In addition, the properties of MXD6 were studied following the mechanical recycling process and they changed differently than PET and Blend properties due to branching/crosslinking of MXD6 due to degradation during processing. Owing to the importance of color generation problem in all the recycled products as well as PET/MXD6 blend in particular; as a second part of the project, a novel method to reduce the color generation in the PET/MXD6 blend during recycling process has been developed and applied. Based on this method, the color generation can be decreas (open full item for complete abstract)

Doctor of Philosophy, Case Western Reserve University, 2017, Macromolecular Science and Engineering

The lifetime performance and degradation behavior of photovoltaic (PV) modules is of the utmost importance for the success and growth of solar energy as a major resource for fulfilling growing worldwide energy needs. While PV reliability has been a concern for some time, existing qualification testing methods do not reflect a cohesive picture of the science behind module degradation, and are not capable of accurately predicting module lifetime performance. Towards these goals, a statistical methodology, semi-gSEM, was developed and applied to investigate the response of full sized PV modules to accelerated stress conditions. The results of this initial study indicated that a correlation exists between system level power loss and the buildup of acetic acid resulting from the hydrolytic degradation of ethylene-vinyl acetate (EVA) polymer encapsulant. To further explore this proposed mechanistic pathway, a study was designed and conducted to characterize the degradation of mini-module samples under damp heat accelerated stress conditions. Mini-module samples featured two construction geometries that differed in the thicknesses of screen-printed silver conductive lines (SP-Ag) to assess the impact of gridline size on damp heat induced degradation. Samples were measured non-destructively at many points along their degradation pathway, using techniques that gathered both chemical and electrical information. The semi-gSEM analytical method was applied to this dataset to highlight degradation pathways and mechanisms observed in the experimental results. An EVA encapsulant spectroscopic degradation feature was found to be statistically related to quantified degradation features of simultaneously measured EL images. In turn, the EL image degradation was found to be statistically related to I-V curve parameters describing system level power loss. The degradation pathway observed was attributed to EVA encapsulant degradation leading to metallization corrosion and ultim (open full item for complete abstract)

Master of Sciences (Engineering), Case Western Reserve University, 2014, Materials Science and Engineering

Degradation of multi-component acrylic systems is becoming increasingly important as polymers and complex systems become commonplace in technological applications. For outdoor applications, understanding the interactions between each stressor and the optical, chemical, and mechanical response is important. This study focuses mainly on the magnitude and variance of optical and chemical properties of hardcoat acrylics on PET (Polyethylene terephthalate) or TPU (thermoplastic polyurethane) substrates, using big-data and unbiased statistics and analytics. PET shows a strong tendency to yellow and haze in accelerated and real-world exposures. A 0.90 correlation coefficient exists between yellowness and UVA-340 irradiance. A 0.8 correlation coefficient exists between haze and UVA-340 irradiance, but moisture must be present for hazing to occur. In TPU films, yellowing occurs until 200 MJ/m2 of UVA-340 irradiance, after which the films clear. Meanwhile, hardcoat acrylics with a TPU substrate are highly resistant to haze in all exposures studied. As optical degradation occurs up to 4000 hours of exposure, little correlation to carbonyl, C-H stretch, or N-H stretch area exists. A weak correlation is observed between increasing optical degradation and spectral attenuation, possibly indicating a complete breakdown of the polymers. Development of a model that relates observable degradation to surface and bulk phenomena can give insights into how to reduce degradation. All of this data must be used to focus the direction of R&D efforts to increase the useful lifetime of multi-component acrylic systems.

Master of Sciences (Engineering), Case Western Reserve University, 2014, Materials Science and Engineering

Understanding transparent conductive oxide (TCO) degradation is critical to improving lifetimes of thin filmphotovoltaics, which utilize TCOs like aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), and fluorine-doped tin oxide (FTO). Commercial AZO, ITO, and FTO were exposed in accelerated and outdoor exposures in several configurations, utilizing environmental stressors such as irradiance, heat and humidity. Electrical and optical properties and surface energies were measured. Yellowness, haze, water contact angle and resistivity of different materials trended differently with exposure time and type, indicating different degradation mechanisms. Interfacial layers for photovoltaic applications were also studied for AZO and ITO. OPV's PEDOT:PSS degrades TCO optics only, suggesting decoupled optical and electrical degradation mechanisms. Hazing of AZO by PEDOT:PSS appears photo-sensitive; 5x outdoor exposures demonstrated higher haze than exposures with no light. 3-aminopropyltriethoxysilane was applied to improve TCO stability and exposed to damp heat. 3-aminopropyltriethoxysilane reduces AZO's resistivity increase and edge effects.

PhD, University of Cincinnati, 2008, Medicine : Toxicology (Environmental Health)

The white rot fungus Phanerochaete chrysosporiumis primarily known for its ability to degrade a wide range of xenobiotic compounds including the highly recalcitrant polycyclic aromatic hydrocarbons. The natural substrate of this basidiomycete fungus is however, lignin, the most abundant aromatic polymer on earth. The versatililty of this fungus in breaking down a wide array of compounds arises from the presence of a highly nonspecific enzyme system (peroxidase enzyme system) in its repertoire. Most of the research involving degradation of toxic chemicals has focused on this biodegrading enzyme machinery. Cytochrome P450 monooxygenases (P450s) on the other hand, are heme-thiolate proteins that are known to be involved in metabolism of endogenous compounds as well as xenobiotic compounds in higher eukaryotes. Nearly 150 P450s are present in this organism, which is the highest number known till date among fungal species. Based on the sequence similarity criteria and our phylogenetic analysis, these P450s have been classified under 12 families and 23 sub-families. Despite indirect evidences suggesting the role of P450s in oxidation of xenobiotics, there have been hardly any reports on characterization and role of individual P450s either in regulation of physiological processes or in direct metabolism of xenobiotics in this organism. Here we characterized and investigated the role of P450 enzymes in two different mechanisms in this fungus. One, indirect involvement of P450s in peroxidase–mediated oxidation of xenobiotics, and two, direct involvement of P450s in metabolism of xenobiotics. In order to achieve the first objective, we investigated the role of PC-bphgene, the only member of the P450 CYP53 in synthesis of a secondary metabolite, veratryl alcohol, which regulates the activity of the peroxidase enzyme system of this fungus. In order to achieve the second objective, we used the functional genomic approach based on a custom-designed microarray and heterologous exp (open full item for complete abstract)

Master of Science (M.S.), University of Dayton, 2011, Chemistry

β-carotene is comprised of isoprene units, and hence contain methyl-substituted polyene chromophores, which contains 11 highly unsaturated conjugated double bonds, nine of which are in a planar polyene chain and the other two of which are located in terminal β-ionylidene rings. The first objective is to determine the kinetics of β-carotene (βC) thermal and photo-degradation rate and evaluate the correlation among content, bleaching time and temperature and solvent effects. The second objective is to figure out the chemical structure of unknown thermal and photo-degradation extents and products structures by instruments of UV-Vis spectrometry, NMR and GC-MS. Solid βC was heated in sealed pyrex tubes to ensure isothermal heating and no oxygen impacts in open tubes with vents to detect oxygen impacts. Analysis of degradation kinetic data suggested a first-order reaction for the thermal-degradation of βC. The thermal-degradation of β-Carotene was studied at oven temperatures of 100, 150 , 200, 250, 300 , 350 °C for for 30min, 60min, 90min, 120min, 4h, 8h, 24h, 72h separately. The kinetics parameters, rate constant k, activation energy Ea =11.5763kJ/mol, and pre-exponential factor A (1.4041h-1) have been calculated based on the linear regression of concentration vs temperature (100-350°C). β-carotene is heat sensitive as expected and the degradation fate displayed a relative heat instability and temperature dependence. The higher the treatment temperature, the longer time exposure period, the faster the degradation rate. The degradation products, retinol, β- ionone etc are confirmed by GC-MS, most of other products are believed to be apocarotenals and epoxy compounds. The kinetics from photochemical experiments using UV irradiation are compared with similar experiments conducted with two-photon laser irradiation. The kinetics of photochemical reactions of β-carotene was studied in hexane, carbon tetrachloride and percentages of carbon tetrachloride in hexane belo (open full item for complete abstract)

Master of Science, University of Akron, 2011, Chemical Engineering

Tissue engineering scaffolds (or matrices) with a controllable degradation profile were fabricated from multiple blends of two L-tyrosine polyurethanes (denoted as PCL1250-HDI-DTH and PEG1000-HDI-DTH ) by means of the electrospinning process. By adjusting the ratios (2:1, 1:1, 1:2, and pure solutions) of the two polymers in the blends, relative control over the scaffolds' degradation properties was achieved without detriment to other scaffold properties. The ability to control the degradation rate allows for scaffold residence time to be design variable when fabricating a medical device intended on mimicking the body. The matrices produced were characterized chemically, morphologically, and mechanically and then subjected to hydrolytic degradation. As theorized, the scaffolds degraded in a predictable and controllable manner. The scaffolds containing the higher proportion of the more resilient PCL1250-HDI-DTH polymer degraded more slowly and to a lesser extent (by mass) than those principally composed of the more hydrophilic PEG1000-HDI-DTH polymer. Specifically, after 60 days of exposure, mass losses (from highest to lowest concentration of PEG1000-HDI-DTH) were approximately 35%, 26%, 21%, 16%, and 9%. Note that decreasing concentration of PEG1000-HDI-DTH correlates to increased resistance to hydrolytic degradation. The mass lost per electrospun scaffold was between 76% and 108% greater than the identical blend in thin film configuration, demonstrating the enhanced degradation characteristics of the structure. Specifically, after 35 days of exposure, mass losses from the electrospun membranes were (from highest to lowest concentration of PEG1000-HDI-DTH) approximately 76%, 85%, 108%, 103%, and 98% greater than those of each blend's thin film counterpart. Morphologically, despite differing polymeric compositions, the scaffolds were fabricated under almost identical conditions and produced similar, acceptable fiber diameters, distributions, and pore sizes with mino (open full item for complete abstract)

Master of Sciences, Case Western Reserve University, 2024, Materials Science and Engineering

As photovoltaic (PV) installations continue to rise and cell technologies evolve, understanding cell-level contributions to module-level failure is going to become increasingly important. Advanced Si PV architectures incorporate different materials and design combinations that influence degradation modes. Ultraviolet-induced degradation (UVID) has been identified as an understudied degradation mode for advanced cell architectures and is of increasing concern in industry due to the increasing use of UV-transparent encapsulation and bifacial technologies. In order to confidently adopt these new and evolving technologies, novel component materials and processing techniques must be evaluated and designed for long-term stability in addition to the conventional design focus on efficiency. The work presented here is three-fold and includes a review of literature relevant to known and suspected UV and light- and elevated temperature-induced degradation (LETID) mechanisms in passivated emitter and rear contact (PERC) and tunnel oxide passivated contact (TOPCon) devices, the development of a study protocol and research framework for the rapid screening of unencapsulated devices against UVID, and the results of the application of that framework to PERC and TOPCon architectures to determine device- and materials-level signatures of degradation. The literature review (Chapter 2) discusses the evolution of crystalline silicon architectures from aluminum back surface field (Al-BSF) to more current tunnel oxide passivated contact (TOPCon) and silicon heterojunction (SHJ) devices. UVID and LeTID mechanisms specific to PERC and TOPCon devices are reviewed. Unencapsulated PERC and TOPCon devices were aged under different UV irradiance intensities and measured via conventional non-destructive electrical characterization methods to assess performance degradation according to the rapid screening protocol developed and outlined in section 3.1 and Chapter 4. Based on the results o (open full item for complete abstract)

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

To meet the growing demands of electric vehicles and energy storage devices, it is essential to develop advanced lithium-ion batteries (LIBs) that not only provide high energy density but also affordability and rapid charging and discharging capabilities. Cathode materials account for over 40% of the total cost of a battery and directly determine the battery's voltage and capacity. Therefore, it is imperative to develop low-cost cathode materials with high electrochemical performance. In this dissertation, we explored several cobalt-free cathode materials, including spinel-structured LiNi0.5Mn1.5O4 (LNMO), nickel-rich cobalt-free LiNi0.95M0.05O2 (M=Al, Mn, Mg, and Ti) layered oxides and xLi2MnO3·(1 – x)LiMO2 (M = Ni and Mn) layered oxides (LMR), which have the advantage of low raw materials price compared to commercialized cathode materials, such as LiCoO2 and cobalt-rich LiNi0.33Co0.33Mn0.33O2 (NMC111) layered oxides. However, like most cathode materials, they also encounter significant challenges, including low thermal stability, an unstable internal structure, and rapid capacity fading, which is caused by serious anisotropic volume changes during cycling, continuous electrolyte decomposition, and transition metal dissolution, particularly at high operating voltages. To overcome these challenges, we present three advanced strategies aimed at producing intergranular-crack-free cathode materials with superior cycling performance, high internal structure stability, and minimal parasitic reactions even under severe cycling conditions. Firstly, employing solid-state electrolytes as Li-ion conductors to form a stable cathode electrolyte interphase (CEI) layer. Secondly, establishing a concentration-gradient layered oxide with a Ni-rich core and an enrichment of substituted elements in the surface region through a co-precipitation reactor. The presence of a Ni-rich core enhances the material's capacity, while the transition elements at the surface ensure excellent cycla (open full item for complete abstract)

Master of Science (MS), Bowling Green State University, 2024, Forensic Science

With fentanyl abuse and opioid related deaths on the rise, the development of a safe and effective disposal method is imperative to mitigate the risk of accidental exposure. Utilizing gas chromatography/mass spectrometry (GC/MS) instrumentation, the fentanyl degradation efficacy of three active ingredients — trichloroisocyanuric acid (TCCA), sodium hypochlorite (NaClO), and 30% hydrogen peroxide (H2O2) — was tested. The three household commercial chemicals, Comet® cleaner with bleach, Clorox® bleach, and 3% hydrogen peroxide, respectively, contain these active ingredients and Clorox® bleach was run on the GC/MS to test its fentanyl degradation efficacy. Previous research has shown that in comparison to other oxidants, TCCA was the most effective at fentanyl degradation. However, there has yet to be a study focusing on whether the concentrations of these active ingredients affect their degradation efficacy. Thus, this experiment tested the degradation efficacy of the previously mentioned active ingredients and statistically determined that NaClO was the best performing active ingredient and that the ideal concentration was medium, and the optimum concentration was the high. This information was then used to test the corresponding commercial chemical, Clorox® bleach, utilizing the same medium and high concentrations. Overall, this study found that Clorox® bleach was just as effective at degrading fentanyl as its isolated active ingredient. This research manages to provide a step towards finding a safe, effective, and easily available solution for fentanyl disposal.

Master of Science (MS), Bowling Green State University, 2024, Forensic Science

Fentanyl is a powerful drug that has contributed to the opioid epidemic by causing thousands of overdoses since its creation. A safe and effective method for cleaning fentanyl is needed to avoid accidental exposure for the general public and first responders, however one does not currently exist. Previous studies have already shown that oxidizers are capable of degrading fentanyl, but not how pH and ionization may affect this degradation. Also, some of these oxidizers are present in household cleaners, such as OxiClean™ and Polident®, which may indicate they could degrade fentanyl as well, but little research regarding this has been completed. This research aimed to further previous work involving the oxidizers sodium percarbonate, peracetic acid, and hydrogen peroxide and their ability to degrade fentanyl by testing the reaction at pH levels of 7, 9, and 11. After establishing that peracetic acid at pH 7 and 9 was the most effective, 3-minute Polident® was examined at both the cleaner's natural pH of 9 and the optimal pH of 7. The remaining fentanyl from these reactions was quantified using area under the curve data from the resulting Gas Chromatography Mass Spectrometer (GC/MS) spectra. Statistical analyses were performed to determine which chemical was most effective and if that chemical's associated household cleaner was as effective at degrading fentanyl. This research determined that peracetic acid at pH 7 and 9 was the most effective oxidizer, and that 3-minute Polident® was just as effective at degrading fentanyl at both pH levels. Ultimately, this research provides a valuable step towards an easy, safe, and effective cleaning method for fentanyl removal and degradation.

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

This thesis delves into the investigation of the degradation mechanisms of silicon-based (Si-based) anodes in lithium-ion batteries, a pivotal concern limiting their widespread application despite their high theoretical capacity. Through a bottom-up approach, the fundamental particle level mechano-electrochemical coupling degradation behaviors of the micro-Si anode are first investigated using situ atomic force microscopy (AFM), then the electrochemical degradation of Si-based anodes (Si and SiO anodes) in cell-level was studied using electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) techniques, eventually, the degradation of practical graphite/silicon blended electrode is studied. This research unravels the complex interplay between Si mechanical morphology and anode electrochemical performance. The study initially focuses on the real-time characterization of micro-Si anodes, revealing a Si dynamic evolution sequence of initial pulverization, followed by irreversible volume expansion, Si particle cracking, and the formation of a new solid-electrolyte interphase (SEI). The characterization indicates that the degradation of micro-Si is attributed to the loss of active material (LAM) due to Si isolations and contact impedance increase. Subsequent experiments extend these insights to full-cell configurations employing nano-Si and micro-SiO, comparing their performance and identifying distinct degradation behaviors. Furthermore, the thesis explores the performance of graphite-silicon blended anodes, demonstrating their superior capacity retention and reduced impedance growth, particularly with low Si content. This work not only advances the understanding of Si-based anode degradation mechanisms but also provides concrete strategies for improving the performance and cycle life of lithium-ion batteries. The findings hold broad implications for the development of high-energy-density batteries, crucial for the future of energy storage, (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Food Science and Technology

Food safety inadequacies constitute a substantial global hazard, not only influencing human health but also bearing serious implications for animal health and environmental sustainability. The sources of food contaminants are diverse, ranging from polluted food production environments during food production to deficient practices in transportation, and inadequate storage conditions. The pollutants that contaminate our food supply can be broadly classified into physical, chemical, and biological. Among biological contaminants, pathogens and microbe-derived metabolites are largely responsible for precipitating foodborne diseases. The built environment—comprising agricultural lands, livestock, aquaculture farms, food industry and consumers settings,—is deeply impacted by microbial threats. It is crucial to provide an effective and environmentally friendly method to modulate biological threats. In the meantime, from a personal environment, it is not only essential to minimize the contact with hazards, but also important to seek an effective and convenient way to mitigate the harmful impacts of the exposure in our daily life. This method should encompass reinforcing human health defenses. This dissertation presents an innovative exploration of two effective approaches aimed at protecting health under a high-risk (cancerous) condition in a personal environment with diet intervention and controlling biological contamination at a built environment level with an environmentally friendly technique. Chapter 2 and 3 investigate the effectiveness of polyphenol-rich diet, black raspberry (BRB), on gut microbiota and their function, with a particular focus on its application for negating harmful effects from carcinogen exposure in high-risk populations. For this, we applied a carcinogenesis mouse model and simulated black raspberry ingestion to determine whether this diet can be an effective way for health risk intervention at a host level. 16s rRNA sequencing and metagenomic (open full item for complete abstract)

MS, University of Cincinnati, 2024, Engineering and Applied Science: Mechanical Engineering

The ball screw is a critical device for precision linear motion control that has widespread applications in industrial robots, computer numerical control (CNC) machines, and high-precision leveling systems, among others. Because high-precision positioning is ensured by the addition of a preload to the ball screw system, it is crucial to detect and monitor the loss of preload at the earliest possible stage of degradation. The degradation process of the ball screw can be characterized in two stages: the initial reduction of preload without backlash, followed by a loss of preload with an emergence of backlash. To explore the change of the ball screw dynamics caused by degradation, a novel fixed cycle feature test (FCFT) is implemented in combination with multi-level mass experiments and a run-to-failure (RTF) test. The relationships of the ball screw dynamics with preload, worktable mass, and axis position are investigated, with a focus on the axial natural frequency as an indicator of preload loss. Experimental results validate the axial natural frequency's role as a reliable early detector of preload loss for interventive use in a prognostic system.

Doctor of Philosophy, University of Akron, 2024, Chemical Engineering

This research aims to enhance the value and sustainability of soybean processing using carbohydrate-degrading enzymes. Soybeans consist mainly of protein (about 40%), carbohydrates (30%), and oil (20%). Oil and protein have significant market value, while the oligomeric and polymeric carbohydrates have indigestive/antinutritional concerns and complicate the protein enrichment and use. Monomerizing these carbohydrates by carbohydrases can simplify soybean processing and convert large quantities of waste carbohydrates to useful sugar-rich fermentation feedstock. Studies done here included enzyme production, optimization of pH and temperature of enzymatic reactions, and enzymatic processing of soybean particles and molasses. Hydrolyzing complex soybean carbohydrates requires cellulase, pectinase, xylanase, α-galactosidase, and invertase activities. These enzymes were produced in submerged and solid-state fermentations of Aspergillus niger NRRL 322 using soybean hull as substrate. Solid-state fermentation yielded higher productivity and enzyme activities with the adjustment of nitrogen and other macronutrients. For optimizing processing temperature, the short-term and long-term temperature effects on enzyme activity and degradation were measured and modeled. For 72-hour processing, the optimal temperature was found at 54°C for α-galactosidase, 48-54°C for invertase, 45°C for cellulase, and <45°C for xylanase and pectinase. Similarly, the pH effect on enzyme activity was measured. The optimal pH was found to be 4.5-4.8 for invertase, 4.5-5.0 for α-galactosidase, 4.5-6.0 for cellulase, and 4.5 for pectinase and xylanase. For the enzymatic processing of soybean particles, the goal was to fractionate oil, protein, and carbohydrate by enzymatically solubilizing the cell-wall polysaccharides to release the membrane-enclosed oil bodies and protein bodies, which are easily separable by centrifugation. Preliminary results confirmed the feasibility of achieving over 90% carbohydr (open full item for complete abstract)