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

Cd(Se,Te) has emerged as a leading choice for commercial thin-film PV devices, owing to their lower cost of production, high energy yields, and low degradation rates compared to silicon technology. Despite significant advancements, Cd(Se,Te) cells suffer from recombination losses, reducing the open-circuit voltage (Voc). This thesis aims to identify, distinguish, and quantify recombination losses and their locations within Cd(Se,Te) solar cells via temperature and light intensity-dependent current-voltage (JVTi) analysis. Cd(Se,Te) solar cells were modeled using COMSOL Multiphysics, simulating parameters such as temperature (T ), light intensity (i), front surface recombination velocity (Sf), back surface recombination velocity (Sb), bulk lifetime (τ ), conduction and valence band offset (CBO and VBO at heterojunctions), and back contact Schottky barrier height (Φbp). Additionally, graded and uniform selenium devices were studied, and ZnTe:Cu was investigated as a back contact interface. In this work, recombination activation energies, Ea, from JVTi studies were shown to quantify the front interface conduction band offset losses when the interface band gap is smaller than the bulk band gap and when front interface recombination dominates. If the Ea equals the bulk band gap, then Voc losses may occur at the front interface or within the bulk. When the front surface recombination and bulk lifetime are moderately low, a transition from front surface (low Ea) to bulk (higher Ea) mechanisms can be observed with increasing light intensity, i. Back surface recombination has negligible effects on Voc for the device parameters specified herein. Comparison of Cd(Se,Te) JVTi data provided by NREL to simulations in this work indicates that front surface recombination dominates Voc losses for Sf = 103 cm/s and CBO = -0.2 eV for that particular device. Adjusting the band alignment to CBO = 0 eV and reducing Sf would significantly increase Voc.

Committee: Marco Nardone (Committee Chair); Mikhail Zamkov (Committee Member); Alexy Zayak (Committee Member) Subjects: Physics

Doctor of Philosophy (PhD), Ohio University, 2023, Chemical Engineering (Engineering and Technology)

Internal corrosion of transmission tubulars is a huge concern in the oil and gas industry. Corrosion inhibitors (CIs) are often considered the first step in mitigating internal corrosion due to their high efficiency and cost-effectiveness. Yet, predicting the efficiency of corrosion inhibitors, developed and tested in a laboratory environment, in operating field conditions is very challenging. In addition, the presence of corrosion residues or corrosion products on the internal surface of tubular steels can significantly affect the inhibition performance of organic corrosion inhibitors. This aspect is only rarely considered when characterizing the performance of corrosion inhibitors. Therefore, understanding their effects on corrosion inhibition is of great benefit in applying corrosion inhibitors to tackle internal corrosion issues, particularly in aging pipelines. This work mainly focuses on evaluating the corrosion inhibition and revealing the inhibition mechanisms in the absence and presence of various corrosion residues or products, commonly found in oil and gas production. The first half of this work (Chapter 5 and 6) presents a methodology for the characterization of corrosion inhibitors and proposes several innovations to an inhibition prediction model, originally based on the work of Dominguez, et al.. An inhibitor model compound, i.e., tetradecyl phosphate ester (PE-C14), was synthesized in-house and characterized to obtain necessary parameter values required as inputs for the inhibition model. The updated inhibition model could predict steady state and transient corrosion inhibition behaviors with good accuracy. The second half of the presented work (Chapter 7, 8, and 9) focuses on the effects of corrosion residue (Fe3C) and products (FeCO3 and FeS) on corrosion inhibition and advances the understanding of the associated inhibition mechanisms. The galvanic effect caused by residual Fe3C on corrosion rate and inhibition efficiency was quantitatively (open full item for complete abstract)

Committee: Marc Singer (Advisor); Srdjan Nesic (Committee Member); David Young (Committee Member); Sumit Sharma (Committee Member); Katherine Cimatu (Committee Member); Katherine Fornash (Committee Member) Subjects: Chemical Engineering; Engineering; Materials Science

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

Phenolic-coal composites are a potential class of thermosetting composites that could offer enhanced thermal stability due to the similarity in aromatic macromolecular structures of the filler and polymer. Evaluating the curing kinetics of the composite can provide insight into the dynamics of bond formation in this composite during heat curing. This study employed Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) to investigate the thermal properties and curing kinetics of phenolic resin and coal mixtures. The cured phenolic-coal composite samples were characterized using Fourier transform infrared spectroscopy (FTIR), to evaluate the interaction between coal filler and the polymer network and correlate coal structure and thermal behavior. The two ranks of coal studied were sub-bituminous coal (Powder River Basin) and bituminous coal (Itmann) at 10% and 40% weight content filler weight percentages. From the TGA, 60% Phenolic-PRB mix (Pmix) had the highest weight loss at 11-12%, while the 60% Phenolic-Itmann (Imix) records the least as 6%. DSC Isoconversional analyses indicated 60% Phenolic-PRB mix had the highest activation energy: 142±8 kJ/mol, while the 60% Phenolic- Itmann mix yielded the lowest range of activation energy values: 85±5 kJ/mol. In comparison, the pure phenolic resin has activation energies in the range of 128 – 135 kJ/mol. The difference in curing activation energy and post-cured vibrational spectroscopy between the composite systems could be attributed to more reactive functional end groups present in the PRB coal. The higher level of interaction observed in the sub-bituminous coal and phenolic mix confirms an enhanced polymeric behavior. Overall, the results from this study provide a basis for the fabrication of phenolic-coal thermoset composites tailored for different applications through modified end properties of cured phenolic resins based on the choice of coal ranks as fillers.

Committee: Valerie Young (Advisor); Eric Stinaff (Committee Member); Jason Trembly (Committee Member); Damilola Daramola (Committee Chair) Subjects: Chemical Engineering; Chemistry; Materials Science; Molecules

MS, University of Cincinnati, 2020, Engineering and Applied Science: Environmental Engineering

As one of the most important persistent organic pollutants (POPs), polychlorinated biphenyls (PCBs) and their remediation has drawn global attention in the past few decades, due to their high toxicity and bioaccumulation in humans, animals, and the ecosystem. PCBs residues commonly occur in air, water, and surface sediments, many of which contain ortho-substituted PCBs which resist environmental degradation more than other congeners. Although the production of PCBs has been prohibited in many regions around the world, affordable and effective cleanup technologies are still in high demand as existing treatments are rather costly. In this study, a catalytic hydro-dechlorination (HDC) method was employed to reduce the toxicity of selected PCB compounds, such as 2-chlorobiphenyl and PCB28. PCB28 (2,4,4'-trichlorobiphenyl), a typical ortho-chlorinated PCB, was cited as one of the six indicator congeners by the World Health Organization (WHO). It prevails and cycles through indoor air, exterior soils, aquatic environments and was detected in the plasma of people who were exposed to indoor PCB-contaminated air. To explore the factors impacting the dechlorination efficiency of ortho-chlorinated PCBs, the extent and patterns of decomposition for both PCBs are studied at mild reaction temperatures viz. 20?, 50? and 80°C under atmospheric pressure. The results show that the highest reaction temperature gives the highest dechlorination ratio. In addition, excessive electron donor, Et3N, helps reduce the activation energy (Ea) of 2-chlorobiphenyl from approximately 24 KJ/mol under equivalent stoichiometric quantity to 12.4 KJ/mol (Et3N/Cl=3:1). To better understand the kinetics of ortho-substituted PCBs, Ea of 2-chlorobiphenyl was investigated and its high value (20+ KJ/mol) indicates that the reaction may be controlled by more than reaction time, temperature and Et3N loading. The intermediate products of the dechlorination of 2,4,4'-trichlorobiphenyl included 2-chlorobiphenyl, (open full item for complete abstract)

Committee: Mingming Lu Ph.D. (Committee Chair); Anastasios Angelopoulos Ph.D. (Committee Member); Sivaraman Balachandran Ph.D. (Committee Member); Maobing Tu Ph.D. (Committee Member) Subjects: Chemical Engineering

PhD, University of Cincinnati, 2020, Engineering and Applied Science: Materials Science

Dynamic mechanical analysis of nanocomposites is important in the assessment of performance and reliability of the material. However not much is known about the relaxation behavior of nanographene sheets (NGS)/polyimide composites. In this work, the relaxation behavior of polyimide and NGS/ polyimide composite was investigated as function of frequency, time, and temperature. Also, the effect of loading was examined to optimize the strength and durability. A modified form of Williams-Landel-Ferry equation (WLF) was utilized with the calculated frequencies to obtain constants C1 and C2. Cole-Cole plots were used to examine the behavior of polyimide and graphene reinforced polyimide and it showed that the composite displayed a good fit to a single-relaxation-time. The activation energy for alpha and beta transitions were determined and Master curves for the nanocomposites were constructed and used to predict the lifetime of the composites. Dielectric relaxation of the composite under various temperatures and frequencies was investigated. It was shown that the electrical properties of the composites increased with increasing weight fraction of graphene. As graphene/polyimide composites has dense morphology, their use as electrode material requires creating pores. Poly (lactic acid) additive was used to create porous graphene/polyimide composite structures. The cured porous composite showed a one phase structure. Lifetime and relaxation modulus for porous NGS/polyimide nanocomposites were determined. The lifetime of the porous composites was shown to be lowered while its damping ability improved.

Committee: Jude Iroh Ph.D. (Committee Chair); Gregory Beaucage Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member); Donglu Shi Ph.D. (Committee Member) Subjects: Materials Science

Master of Science, The Ohio State University, 2016, Chemistry

One of the major limitations of fuel cell is its sluggish kinetics for oxygen reduction reaction (ORR) occurring at the cathode and the expensive, but efficient Pt-based catalysts still remains the best catalyst for ORR. The first part of the thesis will discuss the activation energy measurement of ORR on polycrystalline Pt and PtCu/C in basic condition followed by the mechanism study via Tafel slope analysis. The results show that the activation energy of ORR at 0.8 VRHE is 23.2 ± 3.9 kJ/mol on polycrystalline Pt and 17.0 ± 3.1 kJ/mol on PtCu/C in alkaline media. The Ea obtained are relatively constant under different temperature (27 to 31 °C) and potential (0.7 to 0.95 VRHE) ranges. Tafel slope analysis gives ~ 120 mV/dec at high current density region (hcd) and ~ 60 mV/dec at low current density region (lcd) on both polycrystalline Pt and PtCu/C in alkaline media. The results indicate that the rate determining step of ORR on both polycrystalline Pt and PtCu/C is the first electron transfer step at hcd region and either the chemical dissociation step or the proton transfer step at lcd region. Also, the kinetics of Cu, Au and CuAu/C have also been studied and compared to the Pt-based catalysts. Results show that CuAu/C predominantly goes through a four-electron pathway to produce water and only produces ~10% peroxide as side product. When normalized to geometric area, the kinetic current of Au is 4-fold of CuAu/C and 120-fold of Cu. Among all five catalysts discussed in this thesis, PtCu/C has the highest ORR activity, showing that Pt-based catalyst still exhibits highest ORR activity compared to the other catalysts.

Committee: Anne Co (Advisor); Yiying Wu (Committee Member) Subjects: Chemistry

Master of Science, The Ohio State University, 2016, Chemical Engineering

Calcium looping is a sorbent based chemical looping process that uses calcium oxide or similar calcium sorbent precursors for pre-/post-combustion carbon dioxide capture. Extensive study of this process at the Ohio State University has led to the development of two variants of this process: Carbonation-calcination reaction (CCR) process for post-combustion carbon capture in electricity generation and calcium looping process (CLP) for pre-combustion carbon capture in hydrogen production and electricity generation. CCR is a cyclic post-combustion carbon capture process, demonstrated at a 120 KWth scale at OSU. This demonstration achieved more than 90% carbon dioxide removal and over 99% sulfur dioxide (SO2) removal. It has been shown through process simulations that CCR process induces less energy penalty than the conventional amine/oxy-combustion based carbon dioxide capture technologies. This process involves carbonation-calcination-steam hydration of calcium sorbents. Steam hydration is a reactivation step which mitigates the effect of sintering of sorbents during calcination, regenerates the sorbent surface, and retains carbon capture capacity over a large number of cycles. High pressure steam reactivation of calcium sorbents was investigated and the dependence of hydration rate on steam pressure is obtained. Higher steam partial pressure allows for higher temperatures (500-550oC) to get higher hydration conversions. The reaction being highly exothermic (-109 kJ/mol), high temperature gives high quality heat which can be used elsewhere in the process. Reaction kinetics of steam hydration for four different limestone based sorbents was studied using high pressure thermogravimetric analysis. Elevated pressures (1-3.5 atm) and high temperature (500-530oC) were used in this study. Steam hydration of PG Graymont limestone sorbent experimentally showed second order w.r.t steam pressure driving force (PH2O – P*H2O). Rate constants for each operating conditions were calcu (open full item for complete abstract)

Committee: Liang-Shih Fan Distinguished University Professor (Advisor); Andre Palmer Professor (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy, The Ohio State University, 2015, Physics

As we all live in a special water planet Earth, the significance of water to life has been universally recognized. The reason why water is so important to life has intrigued many researchers. This dissertation will focus on the ultrafast dynamics of protein surface water and protein-DNA interfacial water which have direct importance to the protein structure and function. Using tryptophan as an intrinsic fluorescence probe, combined with site-directed mutagenesis and ultrafast fluorescence up-conversion spectroscopy, we can achieve single residue spatial resolution and femtosecond temporal resolution. We can also precisely determine the local hydration water dynamics by monitoring the Stokes shift of tryptophan one at a time. Previously, the protein surface hydration has been extensively studied by our group. In this thesis, we will provide more details on the methods we are using to extract the hydration dynamics, and also validate our methods from both experimental and theoretical perspectives. To further interrogate the interfacial water hydration dynamics relative to the protein surface hydration, we studied two DNA polymerases: DNA Polymerase IV (Dpo4) and DNA Polymerase Beta (Pol ß). Both proteins show typical surface hydration pattern with three distinct time components including: (i) the ultrafast sub-picosecond component reflects the bulk type water motion; (ii) a few picoseconds component shows the inner water relaxation mainly corresponding to the local libration and reorientation; (iii) the tens to hundred picoseconds component represents the water-protein coupled motion involving the whole water network reorganization. Dpo4, a loosely DNA binding protein, exhibits very flexible interfacial water which resembles its surface water yet with a significantly reduced ultrafast component. Such dynamic interfacial water not only maintains interfacial flexibility, but also contributes to the low fidelity of the protein. In contrast to the Dpo4, pol ß tightly bind (open full item for complete abstract)

Committee: Dongping Zhong (Advisor); David Stroud (Committee Member); Fengyuan Yang (Committee Member); Jay Gupta (Committee Member) Subjects: Biochemistry; Biophysics; Physics

Doctor of Philosophy, The Ohio State University, 2008, Chemistry

Epoxidation is the first metabolic activation step necessary for polycyclic aromatic hydrocarbons (PAHs) to exert their biological activity. Nitrated polycyclic aromatic hydrocarbons (NPAHs) may undergo nitro reduction or ring oxidation, or a combination of ring oxidation and nitro reduction. We used density functional theory at the B3LYP/6-31+G**//B3LYP/6-31G* level of theory to explore both the reduction of NPAHs and epoxidation of PAHs and NPAHs. Substituent effects on the stability of nitrobenzene and its derivatives generated in the process of the nitro reduction were investigated. Two linear (free) energy relationships were observed: (1) a correlation between the enthalpy difference ΔH0meta [ΔH0 = H0 (meta) - H0 (para)] and the charge differences on the carbon bonded to the reaction site for neutral molecules; and (2) a correlation between the ΔH0meta and the Hammett substituent constant difference Δσ (Δσ = σm - σρ). We also explored substituent and solvent effects on the reduction, and linear Hammett correlations were obtained. The effects of ring systems on the reduction thermodynamics were also examined. Larger ring systems and azaheterocycles were found to be generally more feasibly reduced than the parent nitrobenzene system. The thermochemistry of the epoxidation reactions of various PAHs and NPAHs were explored. The regioselectivities of the epoxidations were found to be consistent with the available experimental data. We also investigated the isomerization process for arene oxides, derived from both PAHs and NPAHs, to form the corresponding oxepines. The calculated results quantitatively demonstrate the facility and the feasibility of the isomerization at room temperature. The results reveal the significant effect of the aromaticity changes on the isomerization. By comparing the results for NPAHs with the results for PAHs, the effect of the nitro group on the isomerization was found to be dependent on the location of the oxirane and the structure of th (open full item for complete abstract)

Committee: Christopher M. Hadad PhD (Advisor); David J. Hart PhD (Committee Member); Jovica D. Badjic PhD (Committee Member) Subjects: Chemistry; Pharmacology

Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, 2012, College of Sciences and Health Professions

I have observed unique variations in AC electrical conductivity of solids by dielectric analysis (DEA or DETA) when studied with respect to temperature and frequency. A wide range of solids were examined for this study e.g. organics, polymers, carbohydrates, API's (active pharmacy ingredients) and amino acids. Experimental results clearly show novel dielectric behavior of a linear increase in a log ionic conductivity vs. temperature in the pre-melt (20 to 30oC below the melt temperature) and melt transition regions. We have differentiated the solids which show the conductivity variations in pre-melt from those which do not e.g. pre-melt conductivity variations observed with polar polymers such as nylons and acetal vs. not observed in nonpolar polymers such as polyethylene, polypropylenes and long chain alkanes e.g. tetraconsane and pentacosane. Isothermal dielectric analysis was used to study the cause of this variation in solids which yielded a polarization time property. The effect of various experimental factors on the results such as the effect of heating rate, varying the frequency, and sample size on the dielectric variations in the pre-melt temperature range have been studied. Correlating dielectric with calorimetric analyses gave us a better understanding of solid state properties. Calorimetric analysis was used to assure that the observed variations in the solid state properties are not due to moisture or impurities present in the sample. The ASTM E928-08 “Standard Test Method for Purity by Differential Scanning Calorimetry (DSC)” was employed to verify the purity of the experimental chemicals used in this study e.g. Acetanilide, Acetophenitidine and Vanillin. Activation energies were calculated based on Arhennius behavior to better interpret the changes in the solid. As the different chemicals were heat cool cycled they were more amorphous, as evidenced by the decreasing activation energy for charge transfer with an increasing amorphous content. Morpho (open full item for complete abstract)

Committee: John Masnovi PhD (Committee Chair); Alan Riga PhD (Advisor); Tobili Sam-Yellowe PhD (Committee Co-Chair); Bin Su PhD (Committee Member); Valentin Gogonea PhD (Committee Member) Subjects:

Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, 2012, College of Sciences and Health Professions

Morphological and thermodynamic transitions in drugs as well as their amorphous and crystalline content in the solid state have been distinguished by Thermal Analytical techniques, which include dielectric analysis (DEA), differential scanning calorimetry (DSC), and macro-photo-micrography. These techniques were used to establish a structure vs. property relationship with the United States Pharmacopeia (USP) standard set of active pharmaceutical ingredients (API). DEA measures and differentiates the crystalline solid (low; 10¿¿¿¿¿ pS/cm) and amorphous liquid (high; 10¿¿¿ pS/cm) API electrical ionic conductivity. DEA ionic conductivity cycle establishes the quantitative amorphous/ crystalline content in the solid state at frequencies of 0.1 - 1.00 Hz and to greater than 30 ¿¿C below the melting transition as the peak melting temperature. This describes the “activation energy method”. An Arrhenius plot, log ionic conductivity vs. reciprocal temperature (1/K), of the pre-melt DEA transition yields frequency dependent activation energy (Ea, J/mol) for the complex charging in the solid state. The amorphous content is inversely proportional to the Ea. Where, Ea for the crystalline form is higher and lower for the amorphous form with a standard deviation of ¿¿ 2%. An alternate technique has been established for the drugs of interest based on an obvious amorphous and crystalline state identified by macro-photomicrography and compared to the conductivity variations. This second “empirical method” correlates well with the “activation energy” method. A comparison of overall average amorphous content by the empirical method had a linear relationship with the activation energy method with a correlation coefficient of R¿¿ = 0.925. Additionally, new test protocols have been developed which describe the temperature and material characterization calibration of thermal analyzers with pharmaceuticals. These test protocols can be blended into a universal standard protocol for DSC, DEA (open full item for complete abstract)

Committee: Mekki Bayachou PhD (Committee Chair); Alan Riga PhD (Committee Co-Chair); John Turner PhD (Committee Member); Bin Su PhD (Committee Member); Tobili Sam-Yellowe PhD (Committee Member) Subjects: Analytical Chemistry