Master of Sciences (Engineering), Case Western Reserve University, 2017, Materials Science and Engineering

Ever since its discovery merely over a decade ago, the phenomenon of a tunable 2D electron gas at the heterointerface of SrTiO3 (STO) and LaAlO3 (LAO) has been a source of keen interest and scientific debate. Amongst the list of obstacles in understanding this phenomenon are the understanding of the role of surface adsorbates, the difficulty in elucidating the degree of intermixing at the LAO-STO interface, and marking the heterointerface itself. Films of varying thicknesses grown via Pulsed Laser Deposition (PLD) at varying O2 partial pressures and temperatures were studied. The role of surface adsorbate was investigated via detailed in-situ X-ray Photoelectron Spectroscopy (XPS). O1s regions were split into three components with the main peak identifying main oxide oxygen, while the two shoulder peaks, at ~1 and ~2 eV from the main peak, respectively, were related to hydrous and carbonaceous species. Links between differences in their respective ratios, their energies of bond formation, and ambient atmosphere exposure were established. Changes in the peak ratios vs. temperature were then related to binding energies of adsorbed species and the oxygen content from carbonaceous adsorbates through detailed analyses of C1s regions. Investigations into mechanisms of cationic intermixing were cognizant of conventional electron microscopy methods, which are limited by the respective masses of the atoms present and the small length of the interface examined. Films were subjected to surface and depth analyses via Secondary Ion Mass Spectrometry (SIMS). Intermixing was studied as a function of deposition temperature and film thickness by utilizing fragmented ions containing cations of both the film and the substrate through the use of proprietary Matlab software, and were modeled in 3D with Avizo modeling software. The position of the heterointerface was also marked by tracking a minor amount of Cr+ ions present on the surface of the substrate prior to deposition. Finally, e (open full item for complete abstract)

Committee: Alp Sehirlioglu PhD (Advisor); James McGuffin-Cawley PhD (Committee Member); Peter Lagerlof PhD (Committee Member) Subjects: Chemistry; Engineering; Materials Science; Physics

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

Effective management of pipeline steel corrosion is crucial for asset integrity, CAPEX/OPEX optimization, employee safety and environmental protection for the oil and gas industry. Organic inhibitors, especially of amphiphilic surfactant types, can efficiently reduce corrosion rates when added in small amounts to pipeline transmission systems. Electrochemical methods such as linear polarization resistance, electrochemical impedance spectra, and polarization curves have been adopted extensively to investigate corrosion reaction processes under inhibition, with surface analysis techniques usually playing insignificant roles and only providing elementary information without deeper analyses relating to inhibitor adsorption studies. However, the function of amphiphilic inhibitors depends on their adsorption on the metal surface. Traditional electrochemical measurements cannot usually provide direct information regarding inhibitor adsorption behavior. Therefore, a crucial knowledge gap exists in the fundamental understanding of inhibitor adsorption modes and corrosion inhibition mechanisms, due to the limited application of surface analysis techniques in corrosion inhibitor studies. Given its high resolution, a powerful surface characterization tool with multiple operation modes and good performance in aqueous solution, atomic force microscopy (AFM) has been widely used in surfactant studies for various inert substrates such asmica, graphite, and the noble metal gold. However, AFM has not often been used in with corrosion inhibitor studies involving mild steels. In the few studies AFM was used only to do straightforward surface roughness comparisons and provide some supplementary corrosion morphology evidence. In contrast to these previously reported inhibitor studies, the research reported in this dissertation will show how AFM can be used much more effectively as a main technique for improving the mechanistic understanding of the inhibition behavior of amphiphilic (open full item for complete abstract)

Committee: Srdjan Nesic (Advisor); Sumit Sharma (Committee Member); David Young (Committee Member); Savas Kaya (Committee Member); Katherine Cimatu (Committee Member); Benjamin Bythell (Committee Member); Marc Singer (Committee Member); Alain Pailleret (Committee Member); Katerina Lepkova (Committee Member) Subjects: Chemical Engineering; Petroleum Engineering

Master of Sciences (Engineering), Case Western Reserve University, 2018, Materials Science and Engineering

Properties of structural alloys containing chromium, for example 316L austenitic stainless steel, can be tremendously improved by surface engineering through infusion of interstitial solute, including carbon or nitrogen. However, to make the surface transparent to carbon or nitrogen, it must be “activated”. A potent method that has recently been discovered for such “surface activation” is exposing the alloy to the gaseous products of a pyrolyzed solid reagent. For this purpose, pyrolysis of nitrogen-halide salts with 316L samples has been demonstrated to be highly effective, but the micromechanisms of activation have been elusive. In this thesis project, pyrolysis FT-IR has been used to examine the products of pyrolyzing various solid reagents in an effort to model surface reactions. This work has demonstrated that ammonia and hydrogen chloride evolving from NH4Cl are responsible for reducing the surface oxide and forming chlorides and nitrides in the 316L surface. A new approach has been used to characterize the activated surface: ToF-SIMS paired with isotope-rich solid reagents. This enables observation of transport phenomena and determine surface reaction products. Considerable progress has been made on hybrid-processing (activation separated from infusion) of parts in an industrial capacity. A model has been developed to explain the micromechanisms of activation for low-temperature carburization. Understanding the chemical reactions and microstructural changes occurring during this process is vital for developing more rapid and effective low-temperature surface hardening technologies. One main conclusion of this work is that activation is not simply the reduction of protective surface oxides, but actually the formation of a 3 to 7 micrometer thick layer of chlorides and nitrides in the substrate surface. Also, activation appears to be aided by condensation of pyrolysis products on the fresh surface protecting the newly oxide-free surface from passivation. (open full item for complete abstract)

Committee: Frank Ernst (Committee Chair); Arthur Heuer (Committee Member); John Lewandowski (Committee Member); David Matthiesen (Committee Member) Subjects: Engineering; Materials Science

Master of Science (MS), Wright State University, 2017, Physics

Due to shortcomings in emerging alkali-based atomic physics based systems, a need to investigate alkali resistant materials has arisen. There is interest in alkali based systems such as atomic clocks and diode pumped alkali laser (DPAL) systems. In the case of atomic clocks and DPALs, alkali metal vapor, such as Rb, is the active part of the systems. The alkali vapor is confined in some manner of housing, but the transmission of electromagnetic radiation is required in the cells. This requires the incorporation of windows into the cell. The current window material, however, have been shown to degrade over time, thus reducing the effectiveness of these systems. It is believed that the alkali atoms diffuse into the bulk of the housing material. This diffusion results in changes of optical and, in some cases, structural properties of the material. These changes lead to the degradation of window materials in these alkali-based systems. In an effort to improve the longevity of alkali-based systems, a material study was conducted to identify window material that could resist diffusion-based changes in optical properties. Candidate materials were selected based on their structure, optical properties, and/or density. All candidate materials underwent baseline characterization. Baseline characterization techniques included atomic force microscopy, spectrophotometry, reflectometry, ellipsometry, and X-ray diffraction spectroscopy. Once baseline data was collected, the candidate materials were exposed to Rb at high temperatures for an extended period of time to simulate atomic physics devices. Exposure was achieved by heating the Rb source to ~ 550 °C while the candidate materials were kept at ~ 450 °C. This created a 100 °C temperature gradient to thoroughly expose the materials to gaseous Rb. After exposure, the materials underwent the same analysis techniques to ascertain the changes in structural and optical properties. Additionally, time of flight secondary ion mass spe (open full item for complete abstract)

Committee: Gregory Kozlowski Ph.D. (Advisor); Steven Fairchild Ph.D. (Committee Member); David Turner Ph.D. (Committee Member) Subjects: Materials Science; Physical Chemistry; Physics

Psy. D., Antioch University, 2018, Antioch Seattle: Clinical Psychology

With video game usage--and criticism on its activity--on the rise, it may be helpful for the psychological community to understand what it actually means to play video games, and what the lived experience entails. This qualitative, phenomenological study specifically explores user behaviors and decisions in the simulated life video game, The Sims. Ten participants completed one- to two-hour long semi-structured interviews, and the data was transcribed, organized into 1,988 codes, which were clustered into 30 categories, and from which six themes ultimately emerged. These resulting themes are: self-representation; past, present, and future; purpose for play; self-reflection; co-creation; and familiarity. The essence of playing The Sims includes a degree of self-representation through gameplay choices, projecting one's own past, present or future into the game, and play that is motivated by distinct reasons or benefits. Gameplay in The Sims also involves a sense of familiarity, the interaction of inspirations coming from both the user and the game, and the users' reflections on the connection between themselves and the game. Relationships between the six resulting themes and the current literature on video game psychology are reviewed, and future research and clinical implications are discussed.

Committee: Jude Bergkamp Psy.D. (Committee Chair); Kirk Honda Psy.D. (Committee Member); Elizabeth Fanning Ph.D. (Committee Member) Subjects: Artificial Intelligence; Psychology

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)

Committee: Clemens Burda (Advisor); David Schiraldi (Committee Chair); Alex Jamieson (Committee Member); Chung-Chiun Liu (Committee Member); Xuan Gao (Committee Member) Subjects: Chemistry; Materials Science; Molecular Chemistry; Organic Chemistry; Polymer Chemistry

Master of Sciences (Engineering), Case Western Reserve University, 2015, Materials Science and Engineering

A high temperature Cozchralski crystal growth system was brought online with the intention of growing doped YAG single crystals of novel chemistries. A Ce,Lu:YAG crystal was grown in the system and used in tracer diffusion studies with un-doped YAG, Ce:YAG from varying melt stoichiometries, and Nd:YAG. The self-diffusion was conducted in a gaseous oxygen-18 environment at 1400¿C. The diffusion samples were analyzed via Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Local Electrode Atom Probe Tomography (LEAP) and data analysis methods were developed for each technique. The data analysis provided a more detailed description of the isotope concentration profiles through the depth of the samples on the 0.1nm and 10nm length scales, from the LEAP and ToF-SIMS, respectively.

Committee: James McGuffin-Cawley (Advisor); Mark DeGuire (Committee Member); K. Peter D. Lagerlof (Committee Member) Subjects: Engineering; Materials Science

PhD, University of Cincinnati, 2009, Engineering : Materials Science

The following work is the study to evaluate the impact of corrosion inhibitors on the copper metal in drinking water and to investigate the corrosion mechanism in the presence and absence of inhibitors. Electrochemical experiments were conducted to understand the effect of specific corrosion inhibitors in synthetic drinking water which was prepared with controlled specific water quality parameters. Water chemistry was studied by Inductively Coupled Plasma–Atomic Emission Spectroscopy (ICP–AES) to investigate the copper leaching rate with time. Surface morphology, crystallinity of corrosion products, copper oxidation status, and surface composition were characterized by various solid surface analysis methods, such as Scanning Electron Microscopy/Energy–Dispersive Spectrometry (SEM/EDS), Grazing-Incidence-angle X-ray Diffraction (GIXRD), X-ray Photoelectron Spectroscopy (XPS), and Time-of-Flight Secondary Ions Mass Spectrometry (ToF-SIMS). The purpose of the first set of experiments was to test various electrochemical techniques for copper corrosion for short term before studying a long term loop system. Surface analysis techniques were carried out to identify and study the corrosion products that form on the fresh copper metal surface when copper coupons were exposed to test solutions for 2 days of experiments time. The second phase of experiments was conducted with a copper pipe loop system in a synthetic tap water over an extended period of time, i.e., 4 months. Copper release and electrochemically measured corrosion activity profiles were monitored carefully with and without corrosion inhibitor, polyphosphate. A correlation between the copper released into the solution and the electrochemically measured corrosion activities was also attempted. To investigate corrosion products on the copper pipe samples, various surface analysis techniques were applied in this study. Especially, static mass spectra acquisition and element distribution mapping were carried out by (open full item for complete abstract)

Committee: William Vanooij PhD (Committee Chair); Jude Iroh PhD (Committee Member); Relva Buchanan ScD (Committee Member); Darren Lytle PhD (Committee Member) Subjects: Materials Science

PhD, University of Cincinnati, 2002, Engineering : Materials Science

The adhesion interface formed between the squalene model system and the brass panel was investigated with various analysis techniques. Preliminary experiments were carried out to establish the methodologies to monitor the change during the curing process both in squalene and adhesion interface using GPC (Gel Permeation Chromatography) and TOF-SIMS (Time-of-flight Secondary Ion Mass Spectrometry). GPC analysis of the vulcanization product of the squalene mixture confirmed the formation of the intermediates during the vulcanization reaction. TOF-SIMS analysis of the surface of the brass panel cured in the squalene model mixture showed the incorporation of squalene into the adhesion layer and the existence of the accelerator fragments on the brass surface. Depth profiles and the mass spectra of the adhesion interface demonstrated the formation of the copper sulfide layer. Highly sensitive TOF-SIMS proved to be the adequate tool to investigate the cobalt distribution in the adhesion layer enough to differentiate the depth profile of the organic and inorganic cobalt species. Based upon the methodologies developed, compounding ingredients effects were investigated. It was found that the absence of the double bond on the squalene greatly suppressed the decomposition rate of the sulfenamide accelerator and subsequently the formation of the copper sulfide in the adhesion layer also. It also greatly deterred the incorporation of the cobalt species in the adhesion interface. Removal of carbon black and cobalt salt from the formulation both retarded the initiation of the accelerator decomposition and the effect was larger without cobalt salt. Morphology of the copper sulfide dendrites formed at different curing temperature was investigated with SEM (Scanning Electron Microscopy). At 150°C, the copper sulfide formed on the brass was amorphous with high surface area which would give the higher mechanical interlocking force than the highly crystalline, thin plate-shaped copper sul (open full item for complete abstract)

Committee: Dr. W.J. van Ooij (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2004, Electrical Engineering

AlGaN/GaN heterostructures and high Al mole fraction AlGaN films are used in a wide variety of applications, such as high power/high frequency transistors, UV photodetectors, solar-blind detectors, light-emitting diodes, and laser diodes. However, there are several important issues that need to be addressed in AlGaN/GaN heterostructures, such as the impact of defect states on electronic properties such as mobility and two-dimensional electron gas (2DEG) sheet charge density as well as the role of surface processing on the Schottky barrier height. Also, Si doping of AlGaN with high Al mole fraction has been shown to be difficult and may be restricted by non-intentional impurities and their associated deep levels (such as O), as well as an increasing dopant donor energy with higher Al mole fraction. Correlations have been made between deep level defects and the 2DEG sheet charge density, interface broadening, surface roughness, and Ga-N ratios. Depth-dependent cathodoluminescence spectroscopy (CLS) and secondary ion mass spectrometry (SIMS) reveal the nature of deep level defects and their effect on Si doping of high Al mole fraction (25%-100%) AlGaN. SIMS results provide correlations between AlGaN deep level emissions from CLS and elemental impurities, such as oxygen, distributed through the epitaxial bulk films. Cross-sectional CLS measurements of the AlGaN/sapphire interface reveal luminescence signatures which correlate with oxygen diffusing from the sapphire into the AlGaN. Internal photoemission spectroscopy (IPE) reveals changes in the Schottky barrier height of Ni on AlGaN/GaN heterojunction field effect transistor structures (HFETs) with pre-metallization processing conditions and post-metallization ultra-high vacuum annealing. These variations in the IPE Schottky barrier height are correlated with AlGaN near band edge emissions from low energy electron-excited nanoluminescence spectroscopy (LEEN) and Ni/AlGaN interface impurities by SIMS. It is shown that ch (open full item for complete abstract)

Committee: Leonard Brillson (Advisor) Subjects:

Master of Science, University of Akron, 2006, Physics

Metal oxide nanofibers have potential applications in filtration, catalysis, energy conversion, and other areas. The most popular techniques for the characterization of nanofibers are X-ray diffraction (XRD) and scanning electron microscopy (SEM). However, these methods need to be supplemented with surface sensitive spectroscopies for more complete characterization. In several metal oxide nanofiber systems, unexpected impurities were found which may have a significant influence on the structure and surface chemistry. These impurities are not usually detectable with XRD and SEM. The main spectroscopic methods used here for materials characterization are X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Additionally, two relatively uncommon yet powerful techniques, photoacoustic FTIR and infrared emission spectroscopy are also used. These spectroscopic methods have provided insight into some of the unusual properties of metal oxide nanofibers. With the aid of surface sensitive spectroscopies, further development of these interesting materials will be enabled.

Committee: Rex Ramsier (Advisor) Subjects:

Doctor of Philosophy, Case Western Reserve University, 2013, Materials Science and Engineering

Tolyltriazole (TTAH) is an extensively used industrial-grade corrosion inhibitor (CI) for Cu. This PhD project developed an understanding on the microscopic mechanisms for the TTAH adsorption on Cu, and the effective protection against sulfide-attack in oily medium analogous to automotive lubricants. XPS and ToF-SIMS characterization were carried out on TTAH adsorption films formed on pristine Cu surfaces immersed in 0.01 wt. % TTAH oil solution at room temperature for immersion times ranging from 1 s to 0.6 Ms. Instantaneous complete coverage of the Cu surface by TTAH is revealed by ToF-SIMS. In Tougaard analysis of XPS spectra, the adsorption film morphology is best described by a uniform-layer model assuming a film thickness of 2.5 nm after 86.4 Ks. Depth-profiling in ToF-SIMS and ARXPS provide evidence for two distinct adsorption configurations for TTAH on Cu – polymerized layer, and monomer layer. TTAH adsorption is found to take place on Cu2O. Studying the time-dependent evolution of the surface film suggests a kinetics-controlled mechanism involving two competing reactions: oxidation of Cu to Cu2O, and TTAH-Cu complex formation. The TTAH-Cu complex formation proceeds at the cost of Cu2O. The structure and the chemical-composition of the surface film fluctuate with reaction time. Studying the corrosion of Cu in sulfide solution at 80C in the absence of TTAH suggests that the oxidation of Cu to Cu2O is kinetically favored over Cu corrosion by sulfide attack. The incubation time for the sulfide-attack decreases with increasing S concentration. Two distinct sulfide corrosion products are identified – Cu2SO4, forming at the oxide interface, and Cu2S, forming atop. The presence of TTAH significantly impedes the extent of sulfide-attack. At 80C, the TTAH adsorption film is substantially thicker than that of room temperature. This suggests that the rate-determining step for the formation of the adsorption film is the outward diffusion of Cu from the substrate. (open full item for complete abstract)

Committee: Frank Ernst (Advisor); Arthur Heuer (Committee Member); Jay Mann (Committee Member); Jim McGuffin-Cawley (Committee Member) Subjects: Automotive Materials; Engineering; Materials Science; Metallurgy