Master of Science (MS), Ohio University, 2007, Physics (Arts and Sciences)

This thesis presents a transmission electron microscope fitted with a home designed and built nano manipulator for novel in situ experimentation. The selectivity and nano scale manipulation capabilities of the manipulator were tested on zinc oxide nanorods. Further experimentation was performed on grown gallium oxide nanobelts prepared in an argon gas flow at 950 degrees centigrade. A nanobelt was selected for deformation with the manipulator and a series of manipulations and corresponding diffraction patterns were collected. Preliminary analysis shows trends in the diffraction patterns corresponding to lengthening and contracting of lattice constants ‘a' and ‘c' by a maximum of 3 and 5 Angstroms respectively.

Committee: Martin Kordesch (Advisor) Subjects: Physics, Condensed Matter

Doctor of Philosophy, Case Western Reserve University, 2024, Macromolecular Science and Engineering

Helices are abundant and crucial examples of rigidity throughout biology from protein lever arms in molecular motors to collagen type II that assembles into fibrils in the extracellular matrix (ECM). The origin of the collagen fibril radial length scales is not fully understood but is hypothesized to be related to the flexibility of the protofibril and environmental effects. In this work, we systemically investigate both the elasticity of biomacromolecules and their surrounding elastic environments using simple polyacrylamide gels. We determine the persistence length (lp), a measure of elasticity, of model polypeptide single helices and collagen type II triple helices by using static and dynamic light scattering. Using circular dichroism, we observe that the model polypeptide transitions from a random coil to a helix with increasing pH, and lp increases from ~1 - 2 nm to ~20 nm. In addition, we crosslink the model polypeptide to utilize its increase in lp and produce hydrogels with stain stiffening behavior at low crosslink densities. In various pH and ionic strength environments, triple helical lp varies from 60 - 90 nm but has an intrinsic lp of 90 nm when backbone interactions are neutralized. We correlate the triple helical lp to the fibril diameter as determined by transmission electron microscopy (TEM) in various ionic strength solutions and determine that the values are of similar magnitude unless in high ionic strength solutions. We then investigate the environmental elasticity effects on self-assemblies of complex coacervates using light microscopy and collagen type II fibrils using cryogenic TEM. The volume of the complex coacervate droplets is inversely proportional to the modulus of the gel that the complex coacervates are formed in and have a non-monotonic salt resistance as a function of gel moduli. Collagen fibrils in 100 mM PBS solution are ~50 nm in diameter, and the fibril diameter drops to ~30 nm in gels across 63-8700 Pa moduli. Collagen's lp, s (open full item for complete abstract)

Committee: Svetlana Morozova (Committee Chair); Lydia Kisley (Committee Member); Valentin Rodionov (Committee Member); Michael Hore (Committee Member) Subjects: Biophysics; Materials Science; Physics

Master of Science, Miami University, 2023, Geology and Environmental Earth Science

Goethite (α-FeOOH) is an iron-oxyhydroxide mineral that is commonly found in soils and is of importance within the context of industrial mineralogy and aqueous geochemistry. The structure of goethite is such that vacant rows of octahedral sites form “channels” or micropores within the structure. This study aims to investigate the role these “channels” have in distributing the force induced by dynamic shock compression. Shock compression of synthetic goethite powdered samples were achieved by using an inverted shock microscope and laser driven flyer plates. With this set-up a high-energy laser shoots small aluminum discs at high velocity towards the sample causing compression upon impact. In this experiment, 25 µm aluminum flyer plates with 3.5 km/s impact velocities were used. This resulted in the production of planar shock waves of 5 ns duration in the target goethite. Subsequent investigations of the experimental change via TEM documented that crystal morphology remained unchanged, and that goethite's “bird's nest” texture was maintained. Crystal lattices showed small zones of distortion shift in peaks and the formation of hematite. XRD interestingly identifies two blunt phases: goethite and magnetite. A thixotropic-like model for accompanying shock compression is proposed to account for goethites its shock resistant behavior.

Committee: Mark Krekeler (Advisor); Claire McLeod (Committee Member); Mithun Bhowmick (Committee Member) Subjects: Geology; Mineralogy

Master of Engineering, Case Western Reserve University, 2023, Materials Science and Engineering

Understanding phase transitions and their behaviors are critical in nuclear fuel applications. The transmission electron microscopy (TEM) diffraction field is used to further the understanding of plutonium-zirconium alloys in metallic fuels. Indexing patterns to gain an understanding is time intensive for researchers. Convolutional neural networks (CNN) have exhibited exceptional performance in classification tasks in other fields. Applying them to selected area electron diffraction (SAED) patterns has yielded better than random results. A CNN is capable of classifying between three phase groups, at 650 patterns per second, with a total accuracy up to 83.74%. CNNs can also classify between two phase groups at 82.31% accuracy while being able to discern a difference between patterns of identical symmetry but distinct structure.

Committee: Jennifer Carter (Advisor); Sunniva Collins (Committee Member); Laura Bruckman (Committee Member) Subjects: Computer Science; Materials Science

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

Novel spintronic devices based on magnetic skyrmions, a non-volatile nanoscale topological excitation, are attractive as a new paradigm for high data processing speeds and low operating power, addressing the fundamental scaling restrictions in conventional electronics. Identifying materials capable of hosting small skyrmions and being able to image and manipulate skyrmions in these materials is essential as a path to design and develop such devices. Meanwhile, revealing and understanding the mechanisms underlying emergent spintronic phenomenon in these materials will further facilitate the development of next-generation spintronic devices with application in information storage and processing. The focus of this study is to explore and apply different magnetic characterization techniques in the transmission electron microscope (TEM) to investigate the creation, annihilation and manipulation of magnetic skyrmions in potential spintronic materials and devices. The first phase of this research was committed to the establishment of imaging techniques using Lorentz TEM and STEM. In the second phase, these methods have been employed to explore promising skyrmion hosting materials, including single crystal and novel thin films with broken bulk inversion, oxide interfaces with broken surface/mirror inversion, and centrosymmetric materials with geometric confinement. The study's last step entails the design and investigation of skyrmion dynamics in prototype devices using in-situ sample holders.

Committee: David McComb (Advisor); Jinwoo Hwang (Committee Member); Roberto Myers (Committee Member) Subjects: Condensed Matter Physics; Materials Science

Doctor of Philosophy, Miami University, 2021, Botany

Understanding plant adaptation mechanisms to prolonged water immersion provides options for genetic modification of existing crops to create cultivars more tolerant of periodic flooding. An important advancement in understanding flooding adaptation would be to elucidate the mechanism of aerenchyma air-space formation induced by prolonged immersion. Lysigenous aerenchyma formation occurs through programmed cell death (PCD), which entails the chemical modification of polysaccharides in root tissue cell walls. I investigated if a relationship exists between modification of pectic polysaccharides through de-methyl-esterification, xyloglucan through fucosylation, and the formation of root aerenchyma in select Fabaceae species. To explore this objective, I first characterized the progression of aerenchyma formation within the vascular stele of three different legumes - Pisum sativum, Cicer arietinum, and Phaseolus coccineus – through traditional light microscopy histological staining and scanning electron microscopy. I assessed alterations in stele morphology, cavity dimensions, and cell wall chemistry. Then I conducted an immunolabeling protocol to detect cellulose, hemicellulose (xylan, fucosylated and non-fucosylated xyloglucan), and specific degrees of de-methyl-esterified (DME) homogalacturonan (HG) among species during a 48-hour flooding time series. Additionally, I performed an enzymatic pretreatment to remove select cell wall polymers prior to immunolabeling for cellulose, hemicellulose and DME HG. I was able to determine that all species possessed similar aerenchyma formation mechanisms that begin with degradation of root vascular stele metaxylem cells. Immunolabeling results suggest de-methyl-esterification of HG, and degradation of xyloglucan, occurs prior or concurrent with aerenchyma formation in root vascular tissues. Furthermore, enzymatic pretreatment demonstrated that removal of cellulose and select hemicellulosic carbohydrates unmasks additional antigen (open full item for complete abstract)

Committee: Daniel Gladish Ph.D. (Committee Chair); Robert Baker Ph.D. (Committee Co-Chair); Richard Moore Ph.D. (Committee Member); Melany Fisk Ph.D. (Committee Member); Mitchell Balish Ph.D. (Committee Member) Subjects: Agriculture; Biochemistry; Biology; Botany; Developmental Biology; Plant Biology; Plant Sciences

Doctor of Philosophy (PhD), Ohio University, 2020, Chemical Engineering (Engineering and Technology)

A systematic investigation of pitting failure of mild steel in marginally sour environments was performed with the objective of understanding and predicting the occurrence of localized corrosion. While localized corrosion can happen due to a variety of reasons, recent work has shown that mild steel was particularly susceptible to pitting in environments containing traces of H2S (ppm level in the gas phase, which equates to ppb level of dissolved O2 in the liquid phase) of H2S. Relevant research works related to localized corrosion of mild steel exposed to O2, CO2 and H2S containing aqueous environments were carefully reviewed and a critical comparison was performed, identifying experimental methodologies, common mechanisms and gaps in understanding. A comprehensive parametric study was conducted to identify the operating parameters controlling the occurrence of localized corrosion in marginally sour environments. As a result, pitting was found to occur under the following conditions: 0 mbar < pH2S < 0.15 mbar, pCO2 > 0 bar, temperature < 60C, bulk pH < 6, on X65 mild steel (not on pure iron), in NaCl concentrations of 0, 1, and 10 wt.%, with 3 ppb(w) < [O2]aq < 40 ppb(w). Surface analysis (FIB-TEM-SAED-PED) identified a typically 200 nm thick, porous, detached, and partially oxidized amorphous mackinawite layer precipitated within a Fe3C network. The role of O2 was further investigated to explain the unexpected presence of oxides in the corrosion product layer. Initially, FeS was thought to have been oxidized during the post processing analysis. However, in situ Raman microscopy later showed that oxygen ingress during the experiment was the origin of iron oxide formation. In addition, when [O2]aq < 3 ppb(w), neither corrosion product precipitation nor pitting was observed on the steel surface in any conditions tested, while the uniform corrosion rate remained low. In this case, the protectiveness was due to the presence of a very thin FeS chemisorbed layer. In the p (open full item for complete abstract)

Committee: Marc Singer (Advisor) Subjects: Chemical Engineering; Materials Science

Master of Science, The Ohio State University, 2020, Chemistry

The self-assembly of short designed peptides into functional nanostructures has become a growing interest in a wide range of fields from optoelectronic devices to nanobiotechnology. In the medical field, self-assembled peptides have especially attracted attention due to several attractive features for applications in drug delivery, tissue regeneration, biological engineering as well as cosmetic industry and also the antibiotics field. Here, we focused on developing functional peptide nanomaterials for drug delivery, tumor imaging, and protein immobilization. Camptothecin (CPT) is a natural product with potential anticancer activity, which has been used in research laboratories as the DNA topoisomerase 1 inhibitor1. Camptothecin analogue and itself possesses great ability to self-assemble by J-aggregation and form nanoparticles in aqueous solution. Previously, our group reported self-assembled peptide conjugates functionalized with succinyl camptothecin on C-20 that showed significantly increased solubility and improved stability of lactone E-ring under the physiological condition in human serum albumin (HSA). The amphiphilicity of hydrophilic lysine side chain and hydrophobic CPT molecules stimulate the forming of nanotubes, which was further stabilized by β-sheet formation of hydrophilic/hydrophobic alternating peptide sequence. Cytotoxicity results on human colorectal cancer cells displayed the successful release of active CPT molecules. We hypothesized that self-assembled nanostructures densely coated by PDA can sustain large changes of solvent pH or ionic strength to keep their long-range supramolecular organization. In previous work, we showed that the pH-dependent self-assembly of dilysine-naphthalenediimide (NDI-KK) conjugate can be stabilized by PDA coating to maintain the inner supramolecular organization in the resulting DA/NDI-KK composite. Indocyanine green (ICG) is a Food and Drug Administration (FDA)-approved drug that has been applied in fluoresc (open full item for complete abstract)

Committee: Jonathan Parquette (Advisor); Jovica Badjic (Committee Member) Subjects: Chemistry

Doctor of Philosophy, Miami University, 2019, Cell, Molecular and Structural Biology (CMSB)

Structural studies of membrane proteins are seminal to understand their role in myriad of biological functions. However, studying membrane proteins is challenging due to difficulties in stable expression and purification. Apart from the limitations associated with biochemistry involved in the study of membrane proteins, there is lack of suitable/robust biophysical techniques which have been a roadblock to the progress of this research field. In this dissertation, I have used electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopic techniques to study human KCNQ1 potassium ion channel protein. As presented in chapter 2 of the thesis, I have provided a structural topology model KCNQ1-voltage-sensor domain (Q1-VSD) in POPC/POPG lipid bilayer using EPR spectroscopy. Chapter 3 details lipid bilayer interactions of Q1-VSD using solid-state 31P and 2H NMR spectroscopy. In chapter 4, development and characterization of a membrane mimetic using SMALPs is described to study membrane protein(s). Finally, chapter 5 details the successful expression and purification of human KCNQ1100-370 consisting of helices 1-6 using bacterial system. The protein is further characterized using different biochemical and biophysical techniques. Overall, this dissertation provides a detailed structural aspect of human KCNQ1 ion channel. This work also sheds light on the protein's interaction with lipid bilayer mimetics.

Committee: Gary Lorigan (Advisor); Carole Dabney-Smith (Committee Chair); Rick Page (Committee Member); Dominik Konkolewicz (Committee Member); Haifei Shi (Committee Member) Subjects: Biochemistry; Biophysics; Molecular Biology

Doctor of Philosophy, The Ohio State University, 2019, Materials Science and Engineering

Metal-rich primers have been used for corrosion protection on metals for over 40 years. Recently, researchers started to investigate the use of metal-rich primers on aluminum alloys as an alternative to hexavalent-chromate systems because of their good corrosion-protective properties. The active aluminum-rich primer (AlRP) was invented and developed at NAVAIR (Patuxent River, MD) to protect aluminum alloys and steels. The Al alloy (Al-Zn-In) pigments in AlRP were fabricated from a sacrificial anode alloy, which has a lower open circuit potential (OCP) than common aluminum alloys. However, initial results indicated that the pigment particles in AlRP tended to undergo severe self-corrosion. Therefore, the Al pigments are pretreated in a trivalent chromium passivation (TCP) bath to reduce the self-corrosion rate. The objectives of this study are to understand the corrosion protection properties of AlRP on aluminum alloy 2024-T3 substrate and to evaluate the effect of TCP treatment on the Al pigment particles. The polarization curves of AA2024-T3 and the active aluminum alloy (Al-Zn-In) show that TCP-treated active aluminum alloy has a lower corrosion potential than AA2024-T3 and thus would cathodically protect it. AlRP-coated samples were exposed in accelerated exposure tests, GMW14872 and B117. Exposed samples were then examined using scanning electron microscopy and energy dispersive X-ray spectroscopy to understand the coating degradation process. In addition, samples were immersed in 0.1M NaCl solution for an extended time and were monitored using electrochemical impedance spectroscopy. The AlRP with TCP-treated pigments out performs the coating with untreated pigments. The TCP treatment on the Al-Zn-In pigments was evaluated. The chemistry and morphology of Al pigment particles treated in a TCP bath for three different immersion times were characterized using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and ener (open full item for complete abstract)

Committee: Gerald Frankel (Advisor); Jenifer Locke (Committee Member); Narasi Sridhar (Committee Member) Subjects: Materials Science

Doctor of Philosophy, Case Western Reserve University, 2019, Chemical Engineering

Cuprous and cupric bromide electrochemistry and speciation was examined in electrolytes and concentrations of interest to an all-copper flow battery (CuFB) in a bromide ion supported electrolyte. The all-CuFB was also examined and it was shown that an all-CuFB can operate at geometric current densities of up to 300 mA cm-2 at a temperature of at least 50°C. In addition, the battery was cycled for 50 cycles from 0 to 60% SOC with plating capacities of 125 mAh cm-2 with a voltaic efficiency of 64% at a temperature of 50°C. However, capacity fade (and thus fading coulombic efficiency) was observed due to non-adherent plating on the carbon electrode. Morphology and nucleation of cuprous bromide was examined via current time transients and qualitative plating experiments. Cuprous bromide electrodeposits adhered to gold, silver, and platinum but did not adhere to titanium or glassy carbon. This may due to a lattice mismatch between the copper crystalline structure and the substrate structure. It was determined that electronucleation of cuprous bromide at 30°C between overpotentials of 10 and 150mV on glassy carbon substrates most closely resembled progressive nucleation. Utilizing in situ methods to study the electrochemical nucleation and morphology of cuprous bromide led to the examination of high aspect ratio small gap height cells with side by side electrodes which are typically used for in situ ec-S/TEM. A Wagner number was derived which allows one to determine whether uniform current distribution is expected in the current ec-S/TEM cell design and chemistry of interest.

Committee: Robert Savinell (Committee Chair); Rohan Akolkar (Committee Member); Julie Renner (Committee Member); Daniel Scherson (Committee Member); Jesse Wainright (Committee Member) Subjects: Alternative Energy; Chemical Engineering; Chemistry; Energy; Engineering; Materials Science; Metallurgy; Nanotechnology

Doctor of Philosophy, The Ohio State University, 2018, Materials Science and Engineering

Materials science encompasses a broad range of different materials and applications; however, at its core is the drive to understand structure-property relationships and exploit them to engineer new materials that out-perform current ones. A unifying theme in this is materials characterization: the study of material structure, properties, processing, and performance. Next-generation electronic devices will likely exploit more than just charge transfer and bulk magnetism to compute and store data. Instead, they will also make use of the inherent spin of the electron in so-called spintronic devices. These devices promise higher densities and lower operating power demands, thus significantly increasing performance. Using electron microscopy, the structures of novel magnetic materials are characterized across many length scales, as well as their electronic and magnetic properties using spectroscopy and theory. Advances in aberration corrected scanning transmission electron microscopy (STEM) make it possible to investigate materials' structures at the atomic level on a routine basis. The growth of high quality magnetic thin films is essential to their application in future devices. Characterization of the growth mechanism of pyrochlore Nd2Ir2O7 thin films, as well as their structure and composition is presented, with a thermodynamic explanation of the observed phenomena. In addition, atomic-scale defects and ordering in double perovskite Sr2CrReO6 thin films were studied both experimentally, as well as via a quantum mechanical electron scattering model. It is found that three-dimensional ordering information can be extracted from two-dimensional high-angle annular dark field STEM images. This is due to the fact that as the electron travels through the specimen, it is encoded with such information before being collected to form the image. Using certain sample- and experiment-specific parameters, the experimental data can be compared to simulated results to access (open full item for complete abstract)

Committee: David McComb PhD (Advisor); Jinwoo Hwang PhD (Committee Member); John Lenhart PhD (Committee Member); Fengyuan Yang PhD (Committee Member) Subjects: Materials Science

Doctor of Philosophy, University of Toledo, 2017, Electrical Engineering

Electrically conductive hair-like structures, referred to as whiskers, can bridge the gap between densely spaced electronic components. This can cause current leakage and short circuits resulting in significant losses and, in some cases, catastrophic failures in the automotive, aerospace, electronics and other industries since 1946. Detecting a metal whiskers (MWs) is often a challenging task because of their random growth nature and very small size (diameters can be less than 1 µm, lengths vary from 1µm to several millimeters). Many decades ago the industry introduced whisker mitigating Pb in the solders used to fabricate electric and electronic parts. In recent years, this changed because the European Union (EU) passed a legislation in 2006, called “Restriction of the use of Certain Hazardous Substances (RoHS) in Electrical and Electronic Equipment”, which requires a reduction and elimination of the use of Pb in technology. Thus, the issue of undesirable and unpredictable whiskers growth has returned and there is a renewed interest in the mechanisms of formation of these structures. None of the whisker growth models proposed to date are capable of answering consistently and universally why whisker grow in the first place and why Pb addition suppresses their growth. Understanding MW nucleation and growth mechanism are of significant interest to this project, since this would potentially allow the development of new accelerated-failure testing methods of electronic components to replace existing testing methods which are generally found to be unreliable. In particular, this research is intended to study the effects of electric fields on the whisker growth, which according to the recently developed electrostatic theory[1] of whisker growth, are of crucial importance. This theory proposes that the imperfections on metal surfaces can form small patches of net positive or negative electric charge leading to the formation of the anomalous electric field (E), which go (open full item for complete abstract)

Committee: Daniel Georgiev Dr. (Committee Chair); Vijay Devabhaktuni Dr. (Committee Member); Victor Karpov Dr. (Committee Member); Devinder Kaur Dr. (Committee Member); Anthony Johnson Dr. (Committee Member) Subjects: Aerospace Materials; Chemical Engineering; Condensed Matter Physics; Electrical Engineering; Engineering; Experiments; Materials Science; Metallurgy; Nanoscience; Nanotechnology; Physics; Plasma Physics; Solid State Physics; Theoretical Physics

Master of Science, The Ohio State University, 2017, Welding Engineering

The medical device industry has stringent requirements for reliability, first time quality, biocompatibility, and process capability for its components and devices. The requirement of biocompatibility limits the materials available for use in long term implant applications and often requires the joining of exotic dissimilar metals. This provides a significant challenge when creating a robust weld schedule. This thesis contains two case studies in dissimilar metal welding on the small scale. The first chapter is focused on characterization of cross wire platinum to niobium micro resistance spot welds. The chapter details how small changes in processing conditions and material can have a profound effect on microstructure, defects, and mechanical properties. Transmission electron microscopy, nanoindentation, and micro pillar compression experiments were used to optimize the properties and characterize the resulting structure, improving the robustness of the joint. The second chapter utilized statistical methods to improve the microstructure and properties of a bulk metallic glass (Vitreloy 105) to titanium laser weld. A definitive screening design (DSD) experiment was performed to understand the effect of 11 different factors on the properties of a laser weld. The results showed pulse width, use of a zirconium filler metal, offset of the laser beam from the joint center, and pulse shape to be the prominent factors controlling the hardness and modulus of the weld.

Committee: Antonio Ramirez (Advisor); Carolin Fink (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2017, Materials Science and Engineering

High entropy alloys (HEAs) are a relatively new class of materials that have garnered significant interest over the last decade due to their intriguing balance of properties including high strength, toughness, and corrosion resistance. In contrast to conventional alloy systems, HEAs are based on four or more principal elements with near equimolar concentrations and tend to have simple microstructures due to the preferential formation of solid solution phases. HEAs appear to offer new pathways to lightweighting in structural applications, new alloys for elevated temperature components, and new magnetic materials, but more thorough characterization studies are needed to assess the viability of the recently developed multicomponent materials. One such HEA, AlMo0.5NbTa0.5TiZr, was selected to be the basis for this characterization study in part due to its strength at elevated temperatures (s0.2 = 1600 MPa at T = 800 ºC) and low density compared with commercially available Ni-based superalloys. The refractory element containing HEA composition was developed in order to balance the high temperature strength of the refractory elements with the desirable properties achieved by the high entropy alloying design approach for potential use in aerospace thermal protection and structural applications. Ingots of AlMo0.5NbTa0.5TiZr were cast by vacuum arc melting followed by hot isostatic pressing (HIP) and homogenization at 1400 ºC for 24 hrs with a furnace cool of 10 ºC/min. The resulting microstructure was characterized at multiple length scales using x-ray diffraction (XRD), scanning transmission electron microscopy (SEM), conventional and scanning transmission electron microscopy (TEM and STEM), and x-ray energy dispersive spectroscopy (XEDS). The microstructure was found to consist of a periodic, coherent two phase mixture, where a disordered bcc phase is aligned orthogonally in an ordered B2 phase. Through microstructural evolution heat treatment stud (open full item for complete abstract)

Committee: Hamish Fraser (Advisor); Michael Mills (Committee Member); Yunzhi Wang (Committee Member); William Brantley (Committee Member) Subjects: Materials Science

Doctor of Philosophy, University of Akron, 0, Polymer Engineering

A new, simple, and efficient Gas Jet Fiber (GJF) spinning process was used for fabrication of polymer precursor fibers from polymer precursor sol solutions with diameters ranging from a few hundreds of nanometers to a few micrometers, which on subsequent calcination in air resulted in the production of semiconducting metal oxides (SMO) nanofibers. One of the primary objectives of this research work was to fabricate SMO nanofibers for use in photocatalytic oxidation of toxic volatile organic compounds (VOCs) that cause indoor air pollution and to degrade organic pollutants in water treatment applications. Another objective was to create specific arrangements of inorganic oxide or ceramic components in the same nanofibers so as to obtain morphologies that exhibit interesting physico-chemical properties useful in photocatalytic applications. The basic strategy adopted in this work included a synergy of wet precursor sol-gel chemistry and GJF spinning followed by thermal treatment for the synthesis of ceramic nanofibers. First, we investigated and optimized the process for fabrication of titanium dioxide (TiO2), vanadium pentoxide (V2O5), and tin-doped indium oxide (ITO) nanofibers. TiO2 nanofibers exhibited a significantly higher (i.e., almost one order of magnitude) UV-light driven ethanol photocatalytic oxidation rate compared to a commercial grade P25 TiO2 nanoparticles. Second, the production of SMO nanofibers with core-shell (CS) and side-by-side (SBS) configurations was studied for a pair of inorganic oxides. TiO2, ITO, and V2O5 were used for fabrication of bi-component CS and SBS nanofibers. Third, the fabrication strategy for hierarchical V2O5-TiO2 nanostructure from a homogeneous sol solution of a mixture of SMO precursors and polymer in volatile solvents was developed. Nanofibers were successfully obtained with diameters below 200 nm exhibiting a hierarchical `nanorods-on-nanofiber' morphological form as a result of calcination of (open full item for complete abstract)

Committee: Sadhan Jana Dr. (Advisor); Darrell Reneker Dr. (Committee Member); George Chase Dr. (Committee Member); Steven Chuang Dr. (Committee Member); Xiong Gong Dr. (Committee Member); Bryan Vogt Dr. (Committee Chair) Subjects: Chemical Engineering; Chemistry; Nanoscience; Nanotechnology; Polymer Chemistry; Polymers

Doctor of Philosophy, The Ohio State University, 2016, Materials Science and Engineering

Magnesium diboride (MgB2) is a material with a superconducting transition temperature of 39 K. Discovered in 2001, the relatively large coherence length (and associated lack of weak links) together with its simple binary composition (making phase pure formation relatively easy) have made it a material of substantial interest. However, its inadequate in-field performance limits the high field applications. Chemical doping is the key to increasing the Bc2 of MgB2. Chemical doping aiming at Mg site or B site substitution is of interest and both routes are explored in this thesis. Structure-property correlations are developed for dopants that either do or do not, incorporate themselves into the MgB2 matrix. First, the effects of C doping in the state of art MgB2 wires were investigated. In order to do so, a series of state of the art C doped MgB2 wires, in both mono-filamentary and multi-filamentary forms, were fabricated by a local company. Their transport and magnetic performance in various magnetic fields, and mechanical induced degradation, were examined. The C doping influence on the critical current density and the n-values were discussed. Secondly, the effects of rare earth oxide (REO) doping in MgB2 were studied. Two sets of samples including both bulk samples and wires were fabricated. Microstructural evidence obtained by SEM and TEM proved that nano-size inclusions formed after REO doping acted as grain growth inhibitors, as evidenced a reduction of MgB2 grain size in REO doped bulk samples. The results of XRD and magnetic measurements on the bulk samples demonstrated that Dy2O3 and Nd2O3 do not alloy with MgB2, no changes being observed in the lattice parameters, Tc and Bc2 of doped MgB2. Enhancements in flux pinning and Jc were obtained in both bulk samples and wires by REO doping, consistent with the microstructural evidence of notable grain refinements and the presence of nano-size inclusions as new pinning sites in MgB2 grains. Lastly, a set of metal d (open full item for complete abstract)

Committee: Michael Sumption (Advisor); Patricia Morris (Committee Member); Roberto Myers (Committee Member) Subjects: Electromagnetics; Electromagnetism; Engineering; Materials Science; Metallurgy; Physics

Doctor of Philosophy, The Ohio State University, 2016, Materials Science and Engineering

Gallium ion irradiation in dual-beam FIB microscopes is well known to cause some degree of damage during the milling process. Although it has been established that cleaning passes with low energy ions can mitigate the extent of this damage, the mechanisms, extent, and type of damage caused have not been well studied due to geometrical limitations inherent to thin foils. By adapting the needle geometry used for atom probe and tomographic work, we can directly measure the extent of damage layers created during milling. Needles were made of multiple semiconductor, intermetallic, and metal systems, confirming previous estimates of damage thickness in Si and GaAs. Materials tested fell into two distinct classes, amorphous dominated and crystalline defect dominated. Amorphous dominated materials consisted of semiconductors and narrow phase field intermetallics, fitting previous radiation work. Crystalline defect dominated materials had semi-crystalline damage layers under 5 nm at all accelerating voltages, and residual defects were shown to have significant effects on lattice clarity in HAADF-STEM. Contrast between amorphous layers in HAADF-STEM was found to be minimal even under ideal conditions, and HRTEM was necessary to accurately confirm and measure damage layer thickness. The causes and extent of damage layer minimization during low keV milling steps were shown to be consistent across all materials.

Committee: Hamish Fraser (Advisor); Wolfgang Windl (Committee Member); Jinwoo Hwang (Committee Member) Subjects: Materials Science; Metallurgy; Radiation

MS, University of Cincinnati, 2016, Engineering and Applied Science: Mechanical Engineering

This research paper explores the possibility that treating nanomaterials with radiation from neutrons or photons will simulate the processes of diffusion and mass transfer, recovery and recrystallization, formation and interaction of defects. The defects in irradiated CNTs are mostly restricted to the outer layers. Although they appear to be well separated at the beginning, the increase in dosage may cause them to melt and eventually thicken. The most common structural defects one can notice in CNTs are atomic vacancies, topological defects, dangling bonds, microvoids and Stone-Wales defects. When graphene is irradiated there is a possibility that the high-energy particles induce morphological changes. Increase in dosage of radiation is inversely proportional to the probability of production of complex defects. Graphene has a unique property of hosting lattice defects in reconstructed atom arrangements. These defects locally increase the reactivity of the structure and allow adsorption of other atoms on graphene. The most common structural defects in graphene are Stone-Wales defects, single vacancies, reconstructed double vacancies, adatoms or interstitial atoms, substitutional impurities and line defects or one dimensional defects. Raman Spectroscopy and Thermo-Gravimetric Analysis were used in characterizing the materials and Transmission Electron microscope to image the materials before and after exposure to irradiation. To further study how the irradiation modified the nanomaterials some of them were dispersed in water. The pristine samples do not disperse due to the lack of defects while the ones exposed to radiation show that they form a homogenous mixture in some cases.

Committee: Henry Spitz Ph.D. (Committee Chair); Sam Glover Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member) Subjects: Mechanical Engineering

Master of Sciences (Engineering), Case Western Reserve University, 2016, Materials Science and Engineering

Alternative technologies are developing to replace rare-earth permanent magnets because of high costs and limited supply. Rare-earth permanent magnets currently are used in electric-vehicle motors and wind turbines because of their high saturation magnetization and high coercivity. Iron-nitrogen magnets (Fe16N2) with possible giant magnetization, can be a promising candidate for replacing rare-earth permanent magnets. In this study, during nitridation experiments which have been carried out by Z.Feng according to Jack's route, nitrogen austenite formed by nitriding the AHC 100.29 (a-Fe) powders with a gas mixture of 0.11NH3/ 0.89 H2 for 3600s (1h) at 923.15K in a designed nitriding reactor. The nitrided sample containing nitrogen austenite is cryomilled by ball milling the powder at liquid nitrogen temperature for 600s (10 min) at 30 Hz frequency in order for the transformation from nitrogen-austenite to nitrogen martensite to take place, and finally the sample is heat-treated for 7200s (2h) at 403.15K in order to form an ordered nitrogen martensite (Fe16N2) phase with possible giant magnetization. Various characterization techniques, such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and vibrating sample magnetometer (VSM) analysis by S.Lan, have been applied to precisely characterize these samples. Nitrogen austenite with the lattice expansion of 2.3% and the nitrogen content of (9.8±0.4) at.% formed by nitriding the AHC 100.29 (a-Fe) powders. Formation of a small fraction of coherent needle-shaped nitrogen martensite precipitations with possible preferred Nishiyama-Wasserman orientation relationship to the expanded austenite matrix and local rearrangement of nitrogen atoms in small parts of formed precipitations have been observed. Around 90% of the nitrogen austenite transformed into nitrogen martensite with lath-shaped morphology after cryomilling, while around 9% of the nitrogen austenite re (open full item for complete abstract)

Committee: Frank Ernst (Advisor); David Matthiesen (Committee Member); Peter Lagerlof (Committee Member) Subjects: Materials Science