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)

Committee: Jung-Hyun Kim Dr. (Advisor); Jay Sayre Dr. (Committee Member); Stephanie Stockar Dr. (Committee Member); Lei Raymond Cao Dr. (Committee Member) Subjects: Materials Science; Mechanical Engineering

PHD, Kent State University, 2022, College of Arts and Sciences / Department of Physics

We performed single-molecule studies to investigate the impact of several prominent small molecules (the oxazole telomestatin derivative L2H2-6OTD, pyridostatin, and Phen-DC 3) on intermolecular G-quadruplex (i-GQ) formation between two guanine-rich DNA strands that have 3-GGG repeats in one strand and 1-GGG repeat in the other (3+1 GGG), or 2-GGG repeats in each strand (2+2 GGG). Such structures are not only physiologically significant but have recently found use in various biotechnology applications, ranging from DNA-based wires to chemical sensors. Understanding the extent of stability imparted by small molecules on i-GQ structures has implications for these applications. The small molecules resulted in different levels of enhancement in i-GQ formation, depending on the small molecule and arrangement of GGG repeats. The largest enhancement we observed was in the 3+1 GGG arrangement, where i-GQ formation increased by an order of magnitude, in the presence of L2H2-6OTD. On the other hand, the enhancement was limited to three-fold with Pyridostatin (PDS) or less for the other small molecules in the 2+2 GGG case. By demonstrating detection of i-GQ formation at the single-molecule level, our studies illustrate the feasibility to develop more sensitive sensors that could operate with limited quantities of materials. In another study, although its mesomorphic properties have been studied for many years, only recently has the molecule of life begun to reveal the true range of its rich liquid crystalline (LC) behavior. End-to-end interactions between concentrated, ultra-short DNA duplexes – self-assembling to form longer aggregates that then organize into LC phases – and the incorporation of flexible single-stranded “gap” regions in otherwise fully-paired duplexes – leading to the first convincing evidence of an elementary lamellar (smectic-A) phase in DNA solutions – are two exciting developments that have opened new avenues for discovery. In this dissertation, w (open full item for complete abstract)

Committee: Hamza Balci (Committee Chair); Samuel Sprunt (Committee Member); Michael Tubergen (Committee Member); Sanjaya Abeysirigunawardena (Committee Member); Antal Jákli (Committee Member) Subjects: Physics

Doctor of Philosophy (Ph.D.), Bowling Green State University, 2021, Photochemical Sciences

Transparent Semiconducting oxides (TSO) belong to a special group of wide bandgap oxide materials that have high optical transmittance and high conductivity at the same time. Wide bandgap semiconductors are extremely important for their use in numerous electronic/ optoelectronic devices including MOSFETs, Photo diodes, solar cell, LED, Laser diode, sensors, etc. Recently, wide bandgap oxide materials, especially Ga2O3 have attracted a great deal of attention from the scientific community. β-Ga2O3 is the most stable polymorphs of Ga2O3 with an ultra-wide bandgap of 4.9 eV, high breakdown voltage, and high Baliga's Figure of Merit (BFM) that make it an ideal candidate for the next generation high power devices. A comprehensive study of material properties of β-Ga2O3 is needed to fabricate high-performance devices. Unfortunately, our understanding of β-Ga2O3 as a semiconductor material is not comprehensive. Point defects (e.g., Cation or anion vacancies, interstitials, etc.) that significantly affect the electrical and optical properties of this material are not yet fully understood. Proper understanding, characterizing and modification of defects can lead to its application in semiconductor-based devices. Moreover, finding suitable donors and acceptors for β-Ga2O3 to tune its electrical conductivity is crucial for its use in electronic devices. In this thesis, different aspects of β-Ga2O3 are addressed as a semiconductor material. We have studied optical, electrical, and structural properties of β-Ga2O3 single crystals and epitaxial thin films grown by several techniques. Major point defects in β-Ga2O3 were investigated using several novel techniques. We have identified and characterized major electronic traps and investigated their effects on the optical, structural, and electrical properties of β-Ga2O3. We discovered an innovative way to dope β-Ga2O3 providing high free carrier density and good mobility while maintaining low defect concentration. A novel spectromete (open full item for complete abstract)

Committee: Farida Selim Ph.D. (Advisor); Amelia Carr Ph.D. (Other); Alexander Tarnovsky Ph.D. (Committee Member); Alexey Zayak Ph.D. (Committee Member) Subjects: Chemistry; Materials Science; Physics

Master of Science, Miami University, 2019, Geology and Environmental Earth Science

Three groups of fluorapatite from the Mont Saint-Hilaire igneous complex in Quebec, Canada have been analyzed with scanning electron microscopy (SEM), electron probe microanalyses (EPMA), single-crystal X-ray diffraction (SCXRD), Fourier transform infrared spectroscopy (FTIR), and magic angle spinning nuclear magnetic resonance (MAS-NMR) to fully characterize the chemical and structural details of fluorapatite from one of the most mineralogically diverse locales on Earth. SEM and EPMA revealed these fluorapatites to be enriched in Th, Y, and Na, while FTIR showed substantial concentrations of carbonate substituting for phosphate at the tetrahedral site. The Th contents observed in these fluorapatites are the highest ever observed for natural samples, and have implications for designing new solid nuclear waste forms. SCXRD refinements revealed the dissymetrization of two of the three groups from the classic P63/m space group to the P-3 space group due to the elevated Y and Na contents. Lastly, the FTIR and NMR data show the presence of the long debated C-F bond the observation of which has important implications for the incorporation of carbonate groups into apatites, and is the first time this bond has been observed in any natural mineral.

Committee: John Rakovan Dr (Advisor); Claire McLeod Dr (Committee Member); Mark Krekeler Dr (Committee Member) Subjects: Geochemistry; Geology; Mineralogy

Doctor of Philosophy, University of Toledo, 2018, Engineering

Nowadays, shape memory alloys (SMAs), and in particular Nickel-Titanium alloys (i.e., NiTi or Nitinol), are widely used in biomedicine, and to a lesser extent in automotive, and aerospace industries. Thanks to their unique shape memory effect (SME) and superelasticity (SE), these alloys can recover a large deformation up to 8% through reversible phase transformations and provide light-weight actuation in low-profile devices. They also represent other favorable characteristics, such as biocompatibility, low stiffness (i.e., Modulus of elasticity), high damping capacity, and adequate corrosion resistance. Despite the high demand in NiTi alloys, there are two main challenges remaining; one, the inability to fabricate complex components; two, the lack of repeatable processes to provide the desired thermomechanical properties. Conventional methods of fabrication are not suitable for creating NiTi devices such as porous scaffolds and patient-specific curved surfaces. This limitation stems from factors such as the high oxygen reactivity, the stress induced phase transformation, the spring back effects, work hardening, and the burr formation associated with applying conventional fabrication methods for making three-dimensional shapes from NiTi alloys. The promise of additive manufacturing (AM) techniques is to solve these two issues and pave the way for inducing desired thermomechanical properties in a wide variety of NiTi shapes. Selective laser melting (SLM) has already been used successfully to create complex shapes from NiTi. This work focuses on the second issue in inducing the desired thermomechanical properties in the SLM fabricated NiTi parts. It is well established that the thermomechanical response of NiTi depends on the crystal texture and microstructure features of the alloy. These features, in turn, are significantly affected by the thermal and mechanical (thermomechanical) treatment history applied to the material during the alloy development and device fa (open full item for complete abstract)

Committee: Mohammad Elahinia (Advisor); Haluk Karaca (Committee Member); Abdullah Afjeh (Committee Member); Reza Mirzaeifar (Committee Member); Lesley Berhan (Committee Member); Reza Rizvi (Committee Member) Subjects: Mechanical Engineering

Master of Science in Engineering, Youngstown State University, 2018, Department of Electrical and Computer Engineering

Gallium oxide (Ga2O3) belongs to the family of transparent conducting oxides (TCOs) which have emerged as attractive semiconductor material due their excellent properties. TCOs offer the combination of high conductivity along with excellent transparency in the visible region and a large direct band gap of 4.9 eV. These open the scope for applications for deep UV optical and high power/high voltage electronic device applications. The objective of this research was to fabricate high quality Ga2O3 thin films by magnetron sputtering which would be used to fabricate optoelectronic devices. The thin films were deposited on double polished c-plane sapphire substrates. Four investigations were conducted in order to optimize the quality of the thin films. First, the effect of using different Ar/O2 mixture for deposition was investigated. Second, the post deposition annealing was investigated where the films were annealed in vacuum and in different gas environments. Third, the effect of different substrate temperature from 20 ℃ to 800 ℃ was investigated. The fourth investigation was where different amounts of tin were introduced in order to perform n-type doping of the films. The structural and elemental compositional properties of the films were determined using x-ray diffraction and energy dispersive spectrometry measurements. ( ¯2 0 1 ) oriented ß-Ga2O3 single crystal thin films were obtained when deposited using 100 % Ar at 500 ℃. The optical characteristics obtained by UV-VIS spectroscopy measurements showed excellent transmission of 90 - 95% and optical bandgaps of 4.7- 5.0 eV. Addition of tin dopants in the films produced a decrease in the optical bandgaps with increasing concentration of tin to the films.

Committee: Tom Nelson Oder PhD (Advisor); Faramarz Mossayebi PhD (Committee Member); Eric MacDonald PhD (Committee Member) Subjects: Engineering; Materials Science; Solid State Physics

Doctor of Philosophy, The Ohio State University, 2017, Physics

Spintronics research over the past two decades has focused on developing an understanding of spin transport in materials currently used in the semiconductor industry for potential spin-based applications. Recently, a surge of interest in spin transport in antiferromagnetic materials and spin interactions in novel materials have led to many promising discoveries. The work in this dissertation explores discrepancies in past discoveries, provides evidence to support recent theories on antiferromagnetic (AFM) spin transport, and develops the capabilities to further explore spin physics in novel states of matter. This dissertation focuses on four primary topics. First, a thickness dependence of the spin Hall angle in Au is discussed as a potential explanation for a large variance in the previously reported values. Second, evidence supporting a highly efficient mode of spin transport mediated by AFM fluctuations is found in the temperature dependence of the spin pumping signal in Pt/NiO/Y3Fe5O12 trilayers. Third, a new low damping metallic ferromagnet is developed and characterized as a potential platform for future spintronic research. Finally, a molecular beam epitaxy system is established with the capabilities to prepare topologically insulating materials that are predicted to host many novel phenomena.

Committee: Fengyuan Yang (Advisor) Subjects: Physics

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

Magnesium is a promising candidate for biodegradable applications. However, the performance of magnesium based implants is hampered by fast corrosion of the implants as well as hydrogen evolution and excess alkalinity in the vicinity of the implant. Unalloyed magnesium with high purity shows higher resistance to corrosion in simulated body fluids than commercial magnesium and magnesium alloys. The experiments for preparing high purity magnesium coatings using thermal PVD system have been described. The coatings were evaluated using D.C. polarization tests, in vitro and in vitro tests. These high purity coatings lower the corrosion potential and corrosion current of bulk magnesium in simulated body fluid environment and increased cell activity was also observed near the coated surfaces of conventional implant materials. The different issues arising out of using bulk polycrystalline magnesium in the human body can be addressed by using single crystals. This document describes successful efforts to design, build, establish, test and utilize a single crystal grower using the Bridgman approach for directional solidification and study the obtained single crystals. The obtained single crystals were verified for their quality using metallography with optical microscopy, powder x-ray diffraction, laue x-ray diffraction, x-ray pole figures and micro-computed tomography The mechanical properties of single crystal magnesium were studied in comparison with polycrystalline magnesium through tensile, compressive, 3-point bend and izod tests. These tests indicated that single crystal magnesium can have high ductility. Further, the microstructure response to compressive load in two orthogonal directions was also studied by electron backscattered diffraction and x-ray pole figure analysis. It revealed incipient recrystallization at strains as low as 8 % strain during compression. The observed variation in microstructural response with the orientation allows for wide range for tai (open full item for complete abstract)

Committee: Vesselin Shanov Ph.D. (Committee Chair); Rodney Roseman Ph.D. (Committee Member); Mark Schulz Ph.D. (Committee Member); Vijay Vasudevan Ph.D. (Committee Member) Subjects: Materials Science

Doctor of Philosophy, Case Western Reserve University, 1994, Materials Science and Engineering

Dislocations and mechanical properties of single crystal MoSi2 have been investigated. Specimens were tested in compression along (001), (021), and (771) axes at strain rates of 1 × 10-4/s and 1 × 10-5/s and at temperatures ranging from 900-1600°C in vacuum or argon. The yield stress along (001) was an order of magnitude greater than that measured along (021) or (771) and along all orientations the yield stress was strongly dependent on temperature. Rate jump tests performed along (001) at 1400°C revealed that the yield stress was rate sensitive with a stress exponent of 4. The activated slip systems were determined using optical slip trace analyses and techniques in transmission electron microscopy. Slip occurred via five different slip systems (11<100>, 13<100>, 1001/2<111>, 131/2<331>, and 111/2<111>) depending on the orientation, temperature and strain rate at which each test was performed. The critical resolved shear stress was determined for the activated slip systems from the measured 0.2% yield stresses. At 900-1100°C, the lo west critical resolved shear stresses were for slip on the 11<100>, 1101/2<111> and 131/2<331> slip systems while at 1200-1600°C the lowest critical resolved shear stresses were for slip on the 11<100> and the 13<100> slip systems. Decompositions and dissociations of 1/2<331> and 1/2<111> dislocations were observed. The 1/2<331> dislocation decomposes into 1/2<111> and <110> dislocations during deformation at temperatures above 900°C. This decomposition prevents deformation by the 1/2<331> dislocation at temperatures of 1200°C and above. HREM observations of the core of a 1/2<331> dislocation revealed that it was dissociated out of the 13 glide plane after deformation at 900°C, while observations of the core of a 1/2<111> dislocation after deformation at 1100°C revealed that it was dissociated by glide in the 110 plane. These core structures strongly affect the Peierls stress for glide of the 1/2<331> and 1/2<111> dislocations. Large cl (open full item for complete abstract)

Committee: Arthur Heuer (Advisor) Subjects:

Master of Science, University of Akron, 2017, Polymer Science

Two pi-conjugated polymers containing isoindigo or 3,3-(ethane-1, 2 diylidene)bis(indolin-2-one) (EBI) units with latent hydrogen-bonding on the main chain were synthesized and characterized. The designed polymers use thermal liable t-Boc groups as side chains on the backbone and can be easily dissolved in common organic solvent. Further thermal treatment of the polymers at around 180 oC can convert the polymers into strong hydrogen-bonded materials. The effect of formation of intermolecular hydrogen bonding networks on the polymer film properties including the UV/Vis absorption and electrochemical properties are studied. In the second part of this work, 2D organic single crystals of three conjugated small molecules, di-tert-butyl 1,4-dioxo-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-2,5(1H,4H)-dicarboxylate (DPPBoc), isoindigo, and cyclized DPP were successfully prepared by either solution epitaxial growth, mechanical exfoliation, or physical vapor deposition methods for organic field-effect transistor (OFET) applications. A thickness that less than 100 nm can be achieved for the obtained 2D crystals.

Committee: Yu Zhu (Advisor); Steven S.C. Chuang (Committee Member) Subjects: Polymers

Doctor of Philosophy, University of Toledo, 2016, Chemistry

Nanoclusters are finite aggregations of 2-10,000 atoms that interact through synergistic effects to form materials with unique chemical and physical properties.1-5 The properties of nanoclusters have been shown to be size-dependent, and to have incongruous chemical and physical properties from the constituent bulk material.1-5 In recent years there has been an extraordinary scientific effort to establish size-evolutionary patterns to provide a fundamental understanding of the size-dependent properties of nanoclusters.1,3,5,6 The current size-evolutionary patterns for nanoclusters have yielded theoretical and synthetic models that have begun to rationalize and explain the origin of nanocluster properties.1, 3, 5, 7 The size-evolutionary models have shown that large surface-to-volume ratios, quantum confinement, and structural and energetic size effects are the dominating factors that influence the properties of nanoclusters.1-3,5,7 However, there is an obligation to continually revise and improve the current size-evolutionary models to provide a more accurate theory to bridge the understanding between atomic/molecular states, structural motifs at the metal surface interface, and condensed-phase physics.1, 3, 5, 7 M4Ag44(p-MBA)30 nanoclusters, where M is an alkali metal, have recently been shown to have exceptional stability, which confers unique traits to this molecule. In particular, the synthesis is straightforward, produces a truly single-sized molecular product, and has a quantitative yield. Here, we describe in detail the results of experimental and theoretical studies on the synthesis, structure, stability, and electronic and optical properties of M4Ag44(p-MBA)30, including ESI-MS, NMR, optical absorption, IR, TGA, and other measurements as well as DFT and TDDFT calculations. Additionally, the structure and facile synthesis of M4Ag44(p-MBA)30 has provided a “golden” opportunity to explore the effects of doping M4Ag44(p-MBA)30 with gold. This work has deepene (open full item for complete abstract)

Committee: Terry Bigioni PhD (Committee Chair); Dragan Isailovic PhD (Committee Member); Nikolas Podraza PhD (Committee Member); Joseph Schmidt PhD (Committee Member) Subjects: Chemistry; Materials Science; Metallurgy; Nanoscience; Nanotechnology

MS, University of Cincinnati, 2015, Engineering and Applied Science: Materials Science

Magnesium (Mg) is one of the most promising biodegradable materials for implants owing to its mechanical properties. But because of its highly corrosive nature, its corrosion behavior is difficult to control or predict. This document explores a new approach by using single crystal magnesium for the implant application. Directional solidification technique using vertical modified Bridgman-Stockbarger method has been used to grow the high purity Mg single crystals. They have been characterized to test their single crystallinity and high purity using metallogrphy, X-ray diffraction, pole figure, inductively coupled plasma mass spectroscopy (ICPMS) and Micro computed tomography or "micro-CT" techniques. Attempts to improve the corrosion behavior of the substrate has been made via utilizing various surface treatments such as DC anodization, micro arc oxidation (MAO) and chemical etching. In vitro and in vivo corrosion testing has been done to evaluate the corrosion performance using potentiodynamic DC polarization testing as well as weight loss testing. Film characteristics were studied using the various surface analysis techniques such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Medical device prototypes were made for the animal model studies by the NSF Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB) participant collaborators. They were tested for their biological behavior and compatibility.

Committee: Vesselin Shanov Ph.D. (Committee Chair); Relva Buchanan Sc.D. (Committee Member); Mark Schulz Ph.D. (Committee Member) Subjects: Materials Science

Doctor of Philosophy (PhD), Ohio University, 2015, Chemical Engineering (Engineering and Technology)

In oil and gas production, internal corrosion of pipelines causes the highest incidence of recurring failures. Ensuring the integrity of ageing pipeline infrastructure is an increasingly important requirement. One of the most widely applied methods to reduce internal corrosion rates is the continuous injection of chemicals in very small quantities, called corrosion inhibitors. These chemical substances form thin films at the pipeline internal surface that reduce the magnitude of the cathodic and/or anodic reactions. However, the efficacy of such corrosion inhibitor films can be reduced by different factors such as multiphase flow, due to enhanced shear stress and mass transfer effects, loss of inhibitor due to adsorption on other interfaces such as solid particles, bubbles and droplets entrained by the bulk phase, and due to chemical interaction with other incompatible substances present in the stream. The first part of the present project investigated the electrochemical behavior of two organic corrosion inhibitors (a TOFA/DETA imidazolinium, and an alkylbenzyl dimethyl ammonium chloride), with and without an inorganic salt (sodium thiosulfate), and the resulting enhancement. The second part of the work explored the performance of corrosion inhibitor under multiphase (gas/liquid, solid/liquid) flow. The effect of gas/liquid multiphase flow was investigated using small and large scale apparatus. The small scale tests were conducted using a glass cell and a submersed jet impingement attachment with three different hydrodynamic patterns (water jet, CO2 bubbles impact, and water vapor cavitation). The large scale experiments were conducted applying different flow loops (hilly terrain and standing slug systems). Measurements of weight loss, linear polarization resistance (LPR), and adsorption mass (using an electrochemical quartz crystal microbalance, EQCM) were used to quantify the effect of wall shear stress on the performance and integrity of corrosion inhibit (open full item for complete abstract)

Committee: Nesic Srdjan Dr. (Advisor) Subjects: Chemical Engineering; Chemistry; Materials Science; Metallurgy

Doctor of Philosophy, The Ohio State University, 2014, Nuclear Engineering

The U.S. Department of Energy is interested in extending optically-based instrumentation from non-extreme environments to extremely high temperature radiation environments for the purposes of developing in-pile instrumentation. The development of in-pile instrumentation would help support the ultimate goal of understanding the behavior and predicting the performance of nuclear fuel systems at a microstructural level. Single crystal sapphire optical fibers are a promising candidate for in-pile instrumentation due to the high melting temperature and radiation hardness of sapphire. In order to extend sapphire fiber-based optical instrumentation to high temperature radiation environments, the ability of sapphire fibers to adequately transmit light in such an environment must first be demonstrated. Broadband optical transmission measurements of sapphire optical fibers were made in-situ as the sapphire fibers were heated and/or irradiated. The damage processes in sapphire fibers were also modeled from the primary knock-on event from energetic neutrons to the resulting damage cascade in order to predict the formation of stable defects that ultimately determine the resulting change in optical properties. Sapphire optical fibers were shown to withstand temperatures as high as 1300 °C with minimal increases in optical attenuation. A broad absorption band was observed to grow over time without reaching a dynamic equilibrium when the sapphire fiber was heated at temperatures of 1400 °C and above. The growth of this absorption band limits the use of sapphire optical fibers, at least in air, to temperatures of 1300 °C and below. Irradiation of sapphire fibers with gamma rays caused saturation of a defect center located below 500 nm, and extending as far as ~1000 nm, with little effect on the transmission at 1300 and 1550 nm. Increasing temperature during gamma irradiation generally reduced the added attenuation. Reactor irradiation of sapphire fibers caused an initial rapid (open full item for complete abstract)

Committee: Thomas Blue (Advisor); Wolfgang Windl (Committee Member); Lei Cao (Committee Member) Subjects: Engineering; Experiments; Materials Science; Nuclear Engineering; Optics; Radiation

Doctor of Philosophy, Miami University, 2014, Chemistry and Biochemistry

Direct liquid fuel cells, such as the direct formic acid fuel cell, have attracted increasing attention due to the environmental problems caused by the usage of normal fossil fuels. The critical issues in the development of highly efficient fuel cells are the slow kinetics in anode and cathode reactions. Platinum catalysts are normally used in fuel cells to increase the reaction rates. However, the application of these catalysts is still limited due to the limited source and expensive cost, as well as catalyst poisoning during the fuel cell operation. In addition, fuel cell reactions are sensitive to the surface structure of catalysts. Thus, the investigation of synthesis and electrocatalysis of metal catalysts other than pure platinum play a significant role in the development of fuel cells. This dissertation focuses on the synthesis of shape-controlled metal nanomaterials and studies their catalytic activities toward fuel cell reactions, such as formic acid oxidation and oxygen reduction reaction, for better understanding their mechanisms that will benefit in discovering high performance catalysts. For the structure sensitive investigation of formic acid oxidation, the key is to synthesize specific facet enclosed nanocrystals. Thus, a new approach for directly synthesizing low-index palladium nanocrystals was developed, which enables the direct comparison of low-index facets of palladium catalyst toward formic acid oxidation. In addition, twinned palladium nanorods were also introduced, which have higher catalytic activity than low-index palladium nanocrystals. Furthermore, in order to obtain high-index catalytic information of palladium toward formic acid oxidation, high-index facet as well as low-index facet enclosed gold nanocrystals were synthesized and used as templates for the study of the facet effect of palladium overlayer on gold toward formic acid oxidation. For the oxygen reduction reaction, four types of platinum based alloys were synthesized and their (open full item for complete abstract)

Committee: Shouzhong Zou PhD (Advisor); Neil Danielson PhD (Committee Chair); Andre Sommer PhD (Committee Member); Hong Wang PhD (Committee Member); Shashi Lalvani PhD (Committee Member) Subjects: Chemistry; Materials Science

BS, Kent State University, 2014, College of Arts and Sciences / Department of Chemistry and Biochemistry

This thesis overall entails the synthesis and characterization of several novel zinc coordination complexes in attempt to develop alternative Zn catalysts for the ROP of LA. Chapter II described the synthesis and characterization of several zinc thiolate complexes supported by the 1,1,3,3- tetramethylguanidine (H-TMG) ligand. These compounds were synthesized in a very straightforward reaction with diethylzinc, the corresponding thiol, and H-TMG. Reaction of compound 2 yielded an isopropoxide bridged complex that is a proposed intermediate for the ROP of PLA. Chapter III described the preliminary synthetic routes toward the synthesis of polydentate base tethered ligands. Reaction of a dilithiated 2-bromo-4,6-di-tert-butylphenol with dimethylcyanamide was shown to undergo elimination to yield compound 4. This elimination product had not been observed in previous methods for the synthesis of 1,1,3,3-tetraalkylguanidines (HTAG). Finally, Chapter IV described the reactivity of these zinc thiolate compounds and base tethered polydentate complexes in the ROP of LA as well as a method for determining the tacticity of the PLA polymers. Results showed no change in neither reactivity of the zinc thiolate compounds nor stereochemical control of the reaction relative to the zinc aryloxide compounds. The polymerization using the Zn complex with the base tethered ligand requires additional work to completely evaluate its utility.

Committee: Scott Bunge Dr (Advisor); Paul Sampson Dr (Committee Member); Nicola Brasch Dr (Committee Member); Artem Zvavitch Dr (Committee Member) Subjects: Chemistry; Inorganic Chemistry; Polymer Chemistry

Master of Science, University of Akron, 2013, Polymer Science

Abiological self-assembly has emerged as a major, active, and cutting-edge area of chemistry. Within this arena, many terpyridine-based, coordination-driven, self-assembled macrocycles have been created and studied. Investigation of potential properties and the opportunity to unveil the detailed primary and secondary structures of these materials, such as in fibers and crystals, are of particular interest. Considering that few terpyridine-based macrocyclic crystal structures have been reported, the difficulty to obtain suitable crystals for X-ray characterization is evident. Thus, drawing support from polyanionic stablization, a series of rigid, polycarboxylic acids, for example, hexakis(4-carboxyphenyl)benzene, and 3,3',3",5,5',5"-benzene-1,3,5-triyl-hexabenzoic acid (H6BHB) have been prepared to assist the crystallization of triangular terpyridine complexes and marcromolecular systems. A single crystal has been grown using the combination of a benzyl-modified, trisRu(II)-based metallomacrocycle and a 3,3',3",5,5',5"-benzene-1,3,5-triyl-hexabenzoic anion, as the counterion. Subsequently, the first successful X-ray analysis of a triangular, trisRu(II)-based, metallocycle is described.

Committee: Geroge Newkome Dr. (Advisor); Chrys Wesdemiotis Dr. (Committee Member) Subjects: Chemistry

Master of Science in Chemistry, Youngstown State University, 2000, Department of Chemistry

Single crystalline nitride-floride analogs of the binary oxide CaO, and possibly BaO, were prepared for the first time. The proposed compositions were derived by replacing two O2- ions of the oxide formula with NF4-. After repeated trials, a successful technique for preparing these highly air-sensitive materials for X-ray analysis was developed. Ca2NF was subsequently characterized successfully via single crystal x-ray diffraction, and was found to be isostructural with L-Mg2NF, rather than CaO, as previously predicted. In other work, crystal structures of three organic compunds were determined via single crystal x-ray diffraction in a collaborative effort with a researcher at the Department of Chemistry, Union College, Shenectady, NY.

Committee: Timothy Wagner (Advisor) Subjects: Chemistry, General

Master of Science (MS), Wright State University, 2008, Chemistry

A series of 1,3-di-substituted-imidazolium lithium phthalocyanines, in which the substituents on the imidazolium nitrogens were combinations of methyl, ethyl, pentyl, hexyl, isopropyl, adamantyl or 2,4,6-trimethylphenyl groups, was synthesized. The cation exchange of a single lithium ion of dilithium phthalocyanine for a 1,3-disubstituted-imidazolium ion was performed by mixing their salts in common organic solvents under ambient conditions. This afforded a number of imidazolium lithium phthalocyanines in moderate yields. They exhibited poor solubility in most solvents. Their composition and purity were initially verified by 1H and 13C-NMR and elemental analysis. The 1H-NMR spectra also indicated that the imidazolium and lithium phthalocyanine ions are present in a 1:1 ratio. Infrared spectra confirmed the C-C and C-N stretching modes that are characteristic of phthalocyanine and imidazolium aromatic structures. UV-Vis spectra for each compound showed essentially no change in absorption from that of dilithium phthalocyanine, which suggests a lack of influence of the imidazolium ions. Thermal properties of the title compounds were determined through melting points and TGA, in which high melting temperatures (330-370°C) were seen for several complexes and lowered thermal stability was seen for all. The crystal structure of the bis(adamantyl)imidazolium derivative was determined through X-ray diffraction. It was found that water molecules are associated to imidazolium and lithium phthalocyanine ions through hydrogen-bonding, which is possibly the basis for crystallization in imidazolium-lithium-phthalocyanines.

Committee: William Feld PhD (Advisor); David Grossie PhD (Committee Member); David Dolson PhD (Committee Member); Kenneth Turnbull PhD (Other); Joseph F. Thomas, Jr. PhD (Other) Subjects: Chemistry

Doctor of Philosophy, Miami University, 2010, Geology and Environmental Earth Science

Understanding the crystal chemistry of actinides in nuclear waste forms is critical for the evaluation of the material's potential use and stability as solid state waste repositories. Because of the ability of apatite to incorporate lanthanides and actinides there is great interest in the phase as a solid nuclear waste form. However, the crystal chemistry of U and Th in the apatite structure is still poorly understood. This dissertation investigates the structural crystal chemical parameters in a variety of natural and synthetic apatites with substituent U and Th through the complimentary use of single crystal X-ray diffraction and X-ray absorption spectroscopy. 1) Site preference of U and Th in F, Cl, Sr apatites, investigated the site preference of U and Th and the structural response to these substituents in a series of synthetic fluor-, chlor-, and strontium-apatite crystals using single crystal X-ray diffraction. 2) Crystal chemistry of Th in fluorapatite, obtained quantitative information of the local structure of Th in both natural and synthetic fluorapatite by Extended X-ray absorption fine-structure spectroscopy (EXAFS). Understanding the mechanism of incorporation and the structural response of fluorapatite to Th is important in assessing the use of apatite as a possible host for tetravalent radionuclides and understanding the behavior of Th in geological systems where fluorapatite is present. 3) Orientation dependent polarized micro-XAS study of single crystal apatite, developed the technique/equipment to accommodate polarization effects of synchrotron radiation on single crystal apatites. A goniometer was designed for precise positioning of single crystals for microXAS data collection. Lattice orientation is determined from X-ray diffraction data and then can be applied to EXAFS data analysis. The outcome of this technique development will have application to many other studies with similar sample constraints.

Committee: John Rakovan PhD (Committee Chair); John Hughes PhD (Committee Member); Elisabeth Widom PhD (Committee Member); Hailiang Dong PhD (Committee Member); Stephen Wright PhD (Committee Member) Subjects: Mineralogy