Materials Science & Engineering Theses and Dissertations

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    (2023) Kirsch, Dylan; Takeuchi, Ichiro; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Thermoelectrics (TEs) are a class of materials capabl¬¬e of converting heat into electricity in the solid state. Their widespread application is limited by the low efficiency (≈ 5 %) for commercial modules in applications such as waste heat recovery and refrigeration. Half-Heusler (hH) TE intermetallic alloys have good electrical properties that are easily tuned by doping but are limited in commercial deployment due to high thermal conductivity (TC). This limits the achievable thermal gradient across a TE module, reducing the efficiency. One method to improve hH alloy performance is to decrease the lattice contribution to the TC through solid-solution alloying. Combinatorial synthesis approaches have the advantage of rapid sample fabrication and characterization over a wide range of material compositions. This approach can provide insights into materials systems that could be missed using conventional synthesis approaches. Several publications reported p-type NbFeSb hH alloys can accommodate off-stoichiometry, which could positively impact the TE properties similar to TC decrease observed via Ta-alloying. Combinatorial thin film co-sputter synthesis of hH alloy (Ta0.40Nb0.40Ti0.20)-Fe-Sb composition spread libraries coupled with high throughput (HiTp) characterization is utilized to produce maps of the composition-structure-property relationships as a function of Fe- and Sb-content in this system for the first time. Continuous spread composition gradient and homogeneous discrete co-sputtered combinatorial thin film synthesis methodologies are leveraged to investigate the hH stability region and TE performance in (Ta0.40Nb0.40Ti0.20)-Fe-Sb. Combinatorial thin film characterization requires specialized custom or commercial instrumentation capable of scanning across samples. Established HiTp tools were utilized to characterize the crystal structure, electrical transport properties (Seebeck coefficient and electrical resistivity), and chemical composition of the films. A scanning thin film TC measurement instrument was not available prior to this dissertation. Without this ability, the dimensionless TE figure-of-merit zT cannot be calculated. To address this need, a custom, automated Frequency Domain Thermoreflectance (FDTR) instrument was designed and constructed. FDTR TC measurements are presented on single-phase F¯4 3m off stoichiometric discrete combinatorial hH (Ta0.40Nb0.40Ti0.20)-Fe-Sb for the first time. Maximum zT values at 296 K are calculated to be 0.076 for compositions (Nb0.412Ta0.327Ti0.261)28.5Fe40.3Sb31.2 and (Nb0.418Ta0.328Ti0.254)35.0Fe31.7Sb33.3 having TC values around 2.25 ± 0.27 W m-1 K-1.
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    (2023) Thomas, Austin Michael; Richardson, Christopher; Takeuchi, Ichiro; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This thesis is an investigation into the growth and characterization of NbNx and TiN transition metal nitrides, along with the alloy NbxTi1-xN. These materials are commonly used in many applications ranging from superconducting quantum computing, superconducting conventional computing, high kinetic inductance devices such as single photon detectors, and hard coatings for industrial applications. This thesis will begin with an overview of superconducting quantum computing and superconducting materials, then review the fabrication of Josephson junctions and highlight the need for material improvement. The goal of this work is to grow a superconducting nitride material which can be engineered to lattice match with AlN, the barrier layer in a hypothetical all-nitride, epitaxially grown superconducting quantum computing structure. The alloy NbxTi1-xN is chosen as the superconducting alloy of choice due to the range of lattice constants available, the high critical temperature of these nitrides, and the high quality of material able to be grown using PAMBE. The first aim of this thesis studies the binary transition metal nitrides NbNx and TiN to generate endpoints for various properties of the alloy NbxTi1-xN. This thesis is one of the first investigations of multi-phase growth of ε-NbN and γ-Nb4N3, and demonstrates control over the phase, crystal orientation, superconducting properties, and surface morphology by changing PAMBE growth parameters. The second aim of this thesis demonstrates the growth of NbxTi1-xN and is the first investigation of tunable material properties for this alloy by adjusting the composition. The last aim of this work is the development of a novel annealing scheme used to prepare NbxTi1-xN thin films for Josephson junction integration. The novel annealing scheme ensures excellent surface roughness of NbxTi1-xN thin films, increases the superconducting critical temperature of this alloy from approximately 14 K to 16.8 K, and improves the crystal quality by way of nitrogen incorporation and improvement of the crystal quality. The results from this work will be crucial in developing NbxTi1-xN / AlN / NbxTi1-xN Josephson junctions with smooth, uniform interfaces and low-loss, defect free nitride materials. Additionally, this thesis represents an investigation into the relationship between phases of NbNx and TiN, the role of nitrogen incorporation caused by in-situ annealing, and a useful record of control over this material using PAMBE growth conditions and alloy composition.
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    Materials modeling by ab initio methods and machine learning interatomic potentials: a critical assessment
    (2023) Liu, Yunsheng; Mo, Yifei; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Atomistic modeling is a crucial research technique in materials science to simulate physical phenomena based on the interactions of atoms. Density functional theory (DFT) calculation has been the standard technique for evaluating atom interactions, but their applications are limited due to high computation cost. Classical interatomic potential, as another widely adopted technique, provides an alternative by enabling large-scale simulations that are computationally inexpensive. However, the employment of classical potentials for cheap atomistic simulations is achieved in exchange of accurately evaluating atom interactions and the transferability to different chemistries. Most recently, machine learning interatomic potential (MLP) emerges as a new computation technique to bridge the gap between first-principles computation and classical potentials.I first utilized the atomistic modeling based on DFT calculations to find novel Li superionic conductor, a key component of the emerging all-solid-state Li-ion battery technology. I performed a systematic study on the Li-ion conduction of lithium chloride materials system and predicted a dozen potential Li superionic conductors. I revealed that the Li-ion migration in the materials is greatly impacted by the Li content, the cation configuration, and the cation concentrations. I further demonstrated tuning these three factors in designing new chloride Li-ion conductors. Then, I studied the atomistic dynamics predicted by MLPs in comparison to DFT calculations to answer the open question whether MLPs can accurately reproduce dynamical phenomena and related physical properties in molecular dynamics simulations. I examined the current state-of-the-art MLPs and uncovered a number of discrepancies related to atomistic dynamics, defects, and rare events compared to DFT methods. I found that testing averaged errors of MLPs are insufficient and developed evaluation metrics that better indicate the accurate prediction of related properties by MLPs in MD simulations. I further demonstrated that the MLPs optimized by the proposed evaluation metrics have improved prediction in multiple properties. I also study the performance of MLPs in assessing the elemental orderings in a large variety of phases across composition range in alloy system. Using the Li-Al alloy system as a case study, I trained MLPs using only a few phases and the trained MLP demonstrated good performances over a number of existing and other hypothetical materials in- and out- of the training data across the Li-Al binary alloy system. We developed several new evaluation metrics on energy rankings to evaluate the elemental ordering, which is critical for studying the phase stabilities of materials. I tested MLP transferability to other phases and the limits of MLP applications on commonly performed simulations. I also studied the effect of diverse training data on MLP performances. With these efforts evaluating MLP performances for a number of properties, metrics, prediction errors, and dynamical phenomena, I constructed a dataset with a large number of MLPs and their performances and performed an empirical analysis to identify the challenging properties to be predicted by the MLPs. Further, I identified pairs of properties that are challenging to predict. This series of works demonstrated that atomistic modeling is an effective computation technique for studying atomistic dynamic mechanisms, evaluating materials thermodynamics, and guiding materials discovery. As an emerging computational technique, MLPs show good performance on many materials and have great potential to enhance the materials research, but the results show that critical assessments are needed to examine their capabilities to accurately reproduce physical phenomena and understand their limits of performing reliable simulations. My thesis evaluates MLP performances on a number of critical issues related to materials simulations and provides guidance to improve MLPs for future studies.
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    Magnetic nanoparticle inks for syringe printable inductors
    (2023) Fedderwitz, Rebecca; Kofinas, Peter; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Direct Ink Writing (DIW) additive manufacturing (AM) has the transformative potential to construct complex shapes and devices with a single apparatus by exchanging the printable material at the print head. Iron cobalt (FeCo), permalloy (Ni80Fe20), and iron (II,III) oxide (Fe2O3·FeO) nanoparticles with varying magnetic properties were incorporated in resins to explore the influence of particle loading on printability and inductor device performance. It was generally found that increasing particle loading increased ink viscosity, with a loading maximum approaching 29 – 42 vol% depending on the particle type and resin mixtures due to differences in particle shape and size and resin viscosity. With more magnetic content, composites had higher magnetic permeability and inductance. Syringe printable, colloidal, aqueous magnetic inks were made using both stabilized iron oxide and MnZn doped ferrite nanoparticles with added free polymers. MnZn doped ferrite inks are printed into toroids, sintered to improve magnetic permeability and mechanical robustness, and constructed into an inductor device. Inductors with high magnetic permalloy nanoparticle content were also syringe printed into toroids and hand-wound to demonstrate their viability in fabricating three-dimensional inductors. The effect of particle size on stability and printability was observed. The research presented in this thesis investigates various methods for formulating magnetic nanoparticle inks and evaluates the contributions of particle stabilization, free polymer content, solvent composition, and particle loading on the rheological behavior required for syringe printing. Material properties and device performances were characterized using methods such as zeta potential and settling studies to observe particle functionalization and stability, rheology to study viscoelastic flow behavior, and vector network analysis to measure inductance and device efficiency to showcase the viability of this technique to manufacture passive electronic devices.
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    The Determination of Preferred Orientation in Rolled Electrical Steels Using Single Diffraction of Neutrons
    (1963) Eugenio, Manuel; Duffey, Dick; Nuclear Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)
    Preferred orientation in rolled electrical steels has been determined using single diffraction of neutrons from the University of Maryland pool-type nuclear reactor (DMR) operating at 10 KW thermal . X-rays are used extensively to determine preferred orientations in metallic wires and rolled sheets, but X-rays suffer the disadvantage of high absorption and cannot be used effectively on thick samples without chemical or mechanical treatment which ultimately results in the destruction of the samples. The use of reactor neutrons for this purpose is believed to offer particular advantages such as the use of thicker samples and wider beams. To this end, neutrons from the UMR were scattered directly from metallic sheet samples to obtain diffraction patterns from which preferred orientations of the crystallographic axes could be deduced. The neutron diffraction data were obtained in the form of : 1) Maxwellian curves; and 2) rocking curves. To obtain the first type of curve, the sample and neutron detector were rotated at a 1-to-2 angular ratio, respectively, and the diffraction pattern was essentially the Maxwellian neutron energy distribution. From the maximum of the Maxwellian curve, the crystallographic plane mainly responsible for the reflection was calculated; from this, the main orientation was deduced. For the second type of curve, the sample was rocked back and forth, with the neutron detector fixed, and the resulting pattern was used to infer the variation of a given crystallographic direction about its main orientation. The results of this study, particularly on grain-oriented and cube-textured silicon-iron (Si-Fe) alloy sheets demonstrate that single diffraction techniques can be used to determine preferred orientation in highly oriented materials. The results on Si-Fe sheets described as non-oriented indicate the possibility that these techniques may be applicable to ordinary rolled metallic sheets, which are not highly oriented.
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    Functionalized Thin-Film Shape Memory Alloys for Novel MEMS Applications
    (2023) Curtis , Sabrina M.; Takeuchi, Ichiro; Quandt, Eckhard; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Nickel-titanium (NiTi) shape memory alloy (SMA) films are already implemented into microelectromechanical system (MEMS) devices such as sensors, actuators, and implantable medical devices. In this thesis, I used DC magnetron sputter deposition to study the influence of film composition, microstructure, and annealing conditions on the stability of the phase transformation for the NiTi-based SMA thin films TiNiCu, TiNiCuCo, and TiNiHf. SMAs are a type of smart material that can undergo stress or temperature-induced solid-to-solid phase transformation between two different crystalline phases. In NiTi-based SMAs, the two phases are known as martensite with a monoclinic crystalline structure and austenite with a cubic crystal structure. The temperature-induced phase transformations can be used to switch between the martensite and austenite phases, and thus switch between two sets of material properties in the SMA. For example, in NiTi-based SMAs the Young’s modulus, electrical resistivity, and coefficient of thermal expansion of the austenite phase are typically 2X larger than that of the martensite phase. The transformation temperatures, recovery strains, enthalpy of transformation, and fatigue properties of NiTi SMAs can be tuned by alloying NiTi with other elements like copper (Cu), cobalt (Co), and hafnium (Hf). For example, certain compositions of sputtered TiNiCu and TiNiCuCo are known to be ultra-low fatigue SMAs, able to reversibly undergo the phase transformation for 10+ million cycles without degradation in the mechanical or thermal properties. The primary focus of this thesis was the integration of these sputtered NiTi-based SMA thin-films into the following four novel MEMS devices: 1) TiNiCu for magneoelectric sensors, 2) TiNiHf for bistable actuators, 3) TiNiCuCo for stretchable electronics and 4) thin-film SMA stretchable auxetic structures for wearable and implantable medical devices. The shape memory effect was observed in TiNiCu and TiNiHf films when the film thickness and lateral dimensions are downscaled to micro and nano dimensions. In the research publication “Integration of AlN piezoelectric thin films on ultralow fatigue TiNiCu shape memory alloys.”, I showed the reproducibility of the thermal-induced phase transformation of Ti50Ni35Cu15 is attractive for integration into MEMS devices that require a high cycle lifetime. I showed how the SMA’s phase transformation can be used to tune the resonant of bending cantilever-type sensors like magnetoelectric sensors. I also demonstrated excellent thin-film piezoelectric and shape memory alloy properties for 2 μm AlN/ 5 μm TiNiCu films composites deposited onto silicon substrates. The large work densities and high strength-to-weight ratio offered by SMAs are attractive for the development of micro and nano actuators. The thermal induced phase transformation between martensite and austenite is also used to develop bi-directional micro-actuators with TiNiHf/Si and TiNiHf/SiO2/Si composites. In another research publication, “TiNiHf/SiO2/Si shape memory film composites for bi-directional micro actuation”, I demonstrated the influence of film thickness and substrate on the phase transformation properties of TiNiHf thin-films. Ti40.4Ni48Hf11.6 films with thicknesses as low as 220 nm on SiO2/Si substrates can undergo the phase transformation with high transformation temperatures (As > 100 °C) and a wide thermal hysteresis (ΔT > 50 °C). In this publication, we explain how the wide hysteresis and high transformation temperature obtained in TiNiHf films can be used to develop micro and nano-scale bistable actuators based on PMMA/TiNiHf/Si composites. Even though thin-film NiTi-based SMAs are known to reversibly recover superelastic strains of up to 8%, surprisingly, they have not yet been exploited in the growing field of stretchable electronics. In the technical article “Thin-Film Superelastic Alloys for Stretchable Electronics” I demonstrate the first experimental and numerical studies of freestanding thin-film superelastic TiNiCuCo structured into a serpentine geometry for use as stretchable electrical interconnects. Fabricated electropolished serpentine structures were demonstrated to have low fatigue after cycling external strains between 30% - 50% for 100,000 cycles. The electrical resistivity of the austenite phase of a Ti53.3Ni30.9Cu12.9Co2.9 thin-film at room temperature was measured to be 5.43 × 10-7 Ω m, which is larger than reported measurements for copper thin-films (1.87 × 10-8 Ω m). Expanding upon this work, in the conference proceedings paper “Auxetic Superelastic TiNiCuCo Sputtered Thin-Films for Stretchable Electronics”, I present a new platform for functionalized wearable electronics and implantable medical devices based on superelastic thin-film SMA substrates structured into novel stretchable auxetic geometries. Since thin-film SMAs are conductive, the structured substrate itself could serve as the current collector for such stretchable and flexible devices, or a more conductive electrode can be deposited on top of the stretchable auxetic SMA substrate. Overall, the results discussed in this doctoral thesis look to the future of harnessing the functional properties of thin-film sputtered SMAs for novel uses in next-generation MEMS devices.
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    (2023) Guerin, Steven James; Al-Sheikhly, Mohamad I; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Nuclear power plants (NPPs) are complex engineering systems, with malfunctions having enormous potential to lead to widespread and extreme impacts on society and the environment as a whole. Their safe operation depends on a multitude of factors such as intelligent planning, proper design, quality components, high-level safety operations, and economic viability. Due to requiring high temperature and high pressure of an NPP’s cooling fluid, one of the main concerns for further developing safe operating conditions and evaluating component lifetimes is improving our understanding on the issue of corrosion in nuclear systems. In the U.S., all commercially operated Pressurized Water nuclear Reactors (PWRs) are light-water reactors wherein their coolant waters can reach temperatures up to 350 °C. According to a report in 2005 in association with the U.S. Federal Highway Administration, an annual cost of $4.2 billion was directly attributed to corrosion in NPPs in 1998, out of a total $6.9 billion in the electrical utilities industry (Koch, et al., 2005). Boron is added into commercial PWR primary water in the form of boric acid as a soluble chemical neutron “shim” in order to compensate for fuel burnup and allow smooth long-term reactivity control. After a boron nucleus captures a thermal neutron and becomes unstable, the energy of the recoil ions resulting from its fission accounts for up to 33 % of the total dose to the primary water. This event is an important source for H2 and corrosive H2O2, so its product yields must be accurately included in models of the cooling water radiation chemistry. H2 produced in water from the 10B(n,α)7Li fission reaction has been measured up to 300 °C to aid in quantification of the corrosive H2O2 from the same reaction. Thermal energy neutrons from the Rhode Island Nuclear Science Center 2 MW reactor interacted with boric acid contained in N2O-saturated water in temperature-controlled high-pressure cells made from tubing of either titanium or zirconium alloy. After exposure for a minimum of one hour, the solution samples were extracted and sparged with argon. The H2 entrained by the sparging gas was sampled with a small mass spectrometer. A small amount of sodium was included in the boric acid solution so that after sparging, samples could be collected for 24Na activation measurements in a gamma spectrometer to determine the neutron exposure and thus the total energy deposited in solution. The G-value (µmol/J) for H2 production was obtained for water at a pressure of 25 MPa, over a temperature range from 20 °C to 300 °C. These results have been complemented with Monte Carlo N-Particle® (MCNP®) simulations in collaboration with the National Institute of Standards and Technology, and have been compared with previous experimental results at room temperature and simulated results up to 350 °C. Additionally, boric acid has thus far been accepted as a chemically nondisruptive additive, as it was confirmed long ago to have extremely low reactivity with the two main reactive species produced in reactor primary water by radiolysis, the solvated aqueous electron and the hydroxyl radical (e(aq)- and •OH). However, at the Electric Power Research Institute standard desired pH of 7.3 and the operational temperature of 350 °C, approximately 22% of the boron added in PWR primary water exists in the chemical form of the conjugate base, borate, not boric acid. Although borate was previously confirmed to have no appreciable reactions with e(aq)-, it was not adequately studied for reactions with •OH prior to this work. We have observed a clearly apparent reaction between borate and •OH. Current chemistry models are completely ignorant on both the existence of the resultant species and its reactions. The chemical reaction of [B(OH)4]- (borate) with •OH along with cross-reactions of the product species have been studied up to 200 °C to determine those reactions’ rate constants and the products’ spectra. The University of Notre Dame Radiation Laboratory’s 8 MeV electron linear accelerator (LINAC) was configured to perform pulse radiolysis with pulse widths between 4ns to 20ns providing doses between 5.5 Gy and 62 Gy. High-energy electrons from the LINAC interact with the borated solution which has been N2O-saturated and is continuously flowed through a 316 stainless-steel optical cell. The cell temperature was adjusted by resistive-heating silicon cartridges, and pressure was controlled by two syringe pumps to prevent boiling. The cell had two fused silica windows for transmitting light from a xenon arc lamp through the solution and out to a multichromatic spectrophotometer system. Time-resolved spectral data was obtained over nano- and micro-second timeframes, for wavelengths ranging from the deep UV and into the infrared spectrum (250 nm to 820 nm). The reaction rates and products’ spectra were then obtained by analyzing the data using computational aids, namely IGOR Pro by Wavemetrics and KinTek Explorer by KinTek Corp. The product species of the reaction between borate and •OH is conjectured to be •[BO(OH)3]-, on the basis of ab initio calculations, which likely reacts with boric acid or borate to form a polymer radical.
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    Development of Low-Cost Autonomous Systems
    (2023) Saar, Logan Miles; Takeuchi, Ichiro; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A central challenge of materials discovery for improved technologies arises from the increasing compositional, processing, and structural complexity involved when synthesizing hitherto unexplored material systems. Traditional Edisonian and combinatorial high-throughput methods have not been able to keep up with the exponential growth in potential materials and relevant property metrics. Autonomously operated Self-Driving Labs (SDLs) - guided by the optimal experiment design sub-field of machine learning, known as active learning - have arisen as promising candidates for intelligently searching these high-dimensional search spaces. In the fields of biology, pharmacology, and chemistry, these SDLs have allowed for expedited experimental discovery of new drugs, catalysts, and more. However, in material science, highly specialized workflows and bespoke robotics have limited the impact of SDLs and contributed to their exorbitant costs. In order to equip the next generation workforce of scientists and advanced manufacturers with the skills needed to coexist with, improve, and understand the benefits and limitations of these autonomous systems, a low-cost and modular SDL must be available to them. This thesis describes the development of such a system and its implementation in an undergraduate and graduate machine learning for materials science course. The low-cost SDL system developed is shown to be affordable for primary through graduate level adoption, and provides a hands-on method for simultaneously teaching active learning, robotics, measurement science, programming, and teamwork: all necessary skills for an autonomous compatible workforce. A novel hypothesis generation and validation active learning scheme is also demonstrated in the discovery of simple composition/acidity relationships.
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    Pyrolysis of 3D Printed Photopolymers: Characterization and Process Development
    (2023) Tyler, Joshua Bixler; Cumings, John; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    3D printing has shown to be instrumental in the development of complex structures that have been previously unobtainable through traditional manufacturing processes. Photopolymers have been used in lithography-based 3D printing techniques for decades and have shown to be easily printed from the micro to macro scales. The thermal decomposition, or pyrolysis, of patterned photopolymers of microscale and mesoscale has been shown to create carbon devices such as carbon micro electromechanical systems (MEMS) and electrodes. In this dissertation, I present the characterization of pyrolyzed photopolymers 3D printed via stereolithography (SLA) and two-photon polymerization (2PP). Furthermore, processes in which to bolster the material properties of the pyrolyzed materials was examined.First, I study the effects of increasing the pyrolysis temperature on 2PP photopolymers and how this changes the electrical conductivity and microstructure of the material. From this it was shown the ability to vary the conductivity of 3D printed and pyrolyzed glassy carbon parts by up to 500X through only the temperature of pyrolysis, including reaching conductivities an order of magnitude higher than previously reported work. By extending the characterization of pyrolyzed photopolymers to SLA photopolymers I am able to further develop a generalized understanding of the electrical and microstructural properties of pyrolyzed 3D printed photopolymers. Further, demonstrate a metric in which to understand the deformation of the material during pyrolysis and perform an electrical and microstructural study of the material. Secondly, I investigate increasing the electrical and mechanical properties of pyrolyzed photopolymers through metals deposition via electroplating. In doing so I introduce a novel technique on which to electrodeposit on the surface of pyrolyzed SLA and 2PP 3D printed parts. Metallizing these pyrolyzed samples showed to increase both the electrical conductivity and ultimate strength of both pyrolyzed photopolymers. Lastly, I looked at increasing the stiffness of the pyrolyzed photopolymers through the addition of hBN filler into the precursor photopolymer. In doing so I examine the manufacturing of the composite hBN containing photopolymers for 3D printing with SLA and 2PP systems. Following 3D printing and pyrolysis of the hBN/photopolymer composite compositional and microstructural analysis is performed. Mechanical testing of the pyrolyzed composites shows that a slight increase in the stiffness of the material is observed. I have shown the ability to control the electrical conductivity and microstructure of pyrolyzed 3D printed photopolymers through pyrolysis temperature. Through the addition of metals via electroplating I demonstrate a process by which to increase the electrical conductivity and ultimate strength of pyrolyzed photopolymers and through the addition of hBN into the precursor photopolymer I have shown a way to increase the stiffness of the pyrolyzed materials. These processes have already demonstrated the ability to 3D printed electrical devices and have laid out a groundwork for future development of 3D printed electronics, energy-storage devices, and shielding.
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    Title of Dissertation: Structural and Electrochemical Variances in Doped Lithiated Cathodes and Ionically Conducting Solid State Materials: Relationships in Solid State Electrolytes, Cathodes, and the Interfaces
    (2023) Limpert, Matthew A.; Wachsman, Eric D; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Lithium-ion conducting Li7La3Zr2O12 (LLZO) garnets are being explored as a replacement for the flammable organic electrolytes used in batteries. However, LLZO garnets require high temperature sintering to densify the structure, but that microstructure and electrochemical properties can vary with lithium content as the lithium volatizes during sintering. The effects of sintering the LLZO garnet requires a detailed examination and study to determine how lithium content can affect physical properties, phase purity and density, as well as performance through ionic conductivity. Studying these parameters produced ionic conductivities above 10-4 S cm-1 in samples that had increased density by enabling liquid phase sintering through the eutectic between Al2O3 and Li2O. Despite this high conductivity, the movement of Li+ through a solid electrolyte encounters even slower kinetics through the rigid electrolyte-cathode interface to the active cathode material. A cathode for LLZO garnets requires a new design with both ionic conduction and electronic conduction pathways while reducing interfacial resistance when co-sintered. Excess lithium within LLZO garnet reduced formation of nonconductive LaCoO3 when co-sintered with the active material, LiCoO2 (LCO), which enables a new completely solid-state cathode for lithium metal batteries to be designed and interfacial resistance to be minimized. LCO, however, is limited to 4.2 V to ensure long life cycle without lattice deformation. Unlocking the potential 5 V cycling with of LLZO garnet necessitated the development of a higher voltage cathode. Chlorinating the oxygen site of lithium spinel, LiMn2O4, using a citric acid method stabilizes the 2 V plateau, which increases the capacity to 180 mAhr g-1, and triple doping with Co, Fe, and Ni enables customization of the properties while shifting the voltage to 5 V. The high voltage spinel and LLZO garnet enables high voltage cycling with increased safety potential enabling a pathway to a safe 400 Wh kg-1 cell, 150 Wh kg-1 higher than the current state of the art.
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    (2023) Wang, Chuangye; Zhao, Ji-Cheng; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This study leveraged the high-throughput experiments and high-throughput calculations to study the thermodynamic and kinetic behaviors, and mechanical properties of different alloy systems. CALculation of PHAse Diagrams (CALPHAD) and machine learning (ML) are two computational approaches to predict the phase equilibria of alloys and were adopted to study the phase formation of 2436 high-entropy alloys (HEAs). HEAs were found to form 100% BCC at VEC < 6.87 and form essentially 100% FCC at VEC > 9.16 experimentally, this is consistent with the CALPHAD calculations (VEC = valence electron concentration). ML trained models can reach more than 90% accuracy in predicting BCC/B2, BCC/B2 + FCC, and FCC phases. An autonomous materials search engine (AMASE) method was developed by collaborators to map the phase diagram of the thin-film Sn-Bi system in a closed-loop method, which speeds up the phase diagram mapping and thermodynamic assessment processes over the traditional grid mapping. In the NSF sponsored project, the diffusion-multiple approach was employed to map the phase diagrams of the ternary subsystems of the Cr-Fe-Ni-Nb system. Wavelength-dispersive spectroscopy (WDS) mapping was adopted to measure the compositions in the triple-junction areas of diffusion multiples, leading to improve the efficiency of constructing phase diagrams in comparison with the previous practice of using electron probe microanalysis (EPMA) line scans. The WDS mapping method was demonstrated in the experimentally determined ternary phase diagram of Fe-Nb-Ni at 1100 °C. The measured tie-line data was then provided to collaborators to obtain more accurate predictions of the phase stability of topologically close-packed (TCP) phases for future improvement of the Ni-based thermodynamic databases. Besides thermodynamic calculations, mobility assessments of 25 binary systems with single-phase BCC or FCC structure were performed using the 1-parameter Z-Z-Z binary diffusion model. The data will be useful input to robust diffusion coefficient (mobility) databases. Hardness testing was performed to study the solid solution hardening effects on eight Mg-X (X = Al, Ca, Ce, Gd, Li, Sn, Y, Zn) binary systems using liquid-solid diffusion couples and on three binary systems (Mo-Nb, Mo-Ta, and Nb-Ta) of refractory elements using novel macro-gradient samples made by electron beam welding of stacked wedge-samples.
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    (2023) Shi, Changmin; Wachsman, Eric EW; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    There is every-growing clean energy storage systems demand to address the climate change challenges. The Lithium-Sulfur (Li-S) battery using solid-state electrolyte (SSE), therefore, are becoming a rising star to meet this requirement due to the low cost and high domestic availability of sulfur, exceptionally high theoretical energy density of sulfur chemistry, less flammability, the potential for suppression of the polysulfide shuttle, Li dendrite growth, low coulombic efficiency, and short circuiting in more conventional liquid electrolyte Li-S batteries. The most popular SSEs in Li-S battery field are Li10GeP2S12 (LGPS) and Li stuffed garnet type Li7La3Zr2O12 (LLZO) with a space group of Ia3 ̅d. LGPS has a high ionic conductivity of 1–10 mS/cm at room temperature (22℃), but the generation of H2S toxic gas when reacting with moisture and the instability with Li metal limit its applications. LLZO is a highly promising SSE for Li-S batteries due to its reasonably high ionic conductivity (0.1–1 mS/cm) at 22℃ and excellent chemical stability with Li metal. However, Li dendrite growth is still observed in LLZO. To overcome the potential Li dendrite growth issue, our group introduced a novel 3D porous/dense bilayer and porous/dense/porous trilayer LLZO structures that achieve an exceptional Li stripping/plating performance at a high current density of 10 mA/cm2 at 22℃ with no applied pressure. Although significant improvement has been done in mitigating the LLZO/Li anode interface, further work on stabilizing the sulfur/LLZO interface still needs to be done to achieve high energy density and stable cycling Li-S batteries. Through the studies in this dissertation, it was observed that La segregation to the LLZO surface on the sulfur cathode side led to Li-S battery charge failure. To address the issue, a PEO-based interlayer was applied on the cathode side to physically separate sulfur cathode and LLZO. Consequently, the Li-S batteries demonstrated a high initial discharge capacity of 1307 mAh/g at 22℃, corresponding to an energy density of 134 Wh/kg and 639 Wh/L. Next, since the PEO-based interlayer has a low ionic conductivity, an in-situ formed gel polymer electrolyte (GPE) was invented as a catholyte that had a high ionic conductivity of 3.5–5.6 mS/cm at 22℃. With an organic sulfur cathode (active material: sulfurized polyacrylonitrile) and a thin bilayer LLZO architecture, a very stable cycling using high sulfur loading (5.2 mg/cm2) was obtained for 60 cycles at a discharge current density of 0.87 mA/cm2 with a high initial discharge capacity of 1542 mAh/g, corresponding to an energy density of 223 Wh/kg and 769 Wh/L. In addition, using the same configuration and sulfur loading but using a different cell, 80% capacity retention for over 265 cycles was demonstrated at a discharge current density of 1.74 mA/cm2 at 22℃. In the third project, as a small amount of flammable organic liquid catholyte and/or GPE compromises on the safety of solid-state batteries, the proof-of-concept “all-solid-state” Li-S battery using LLZO electrolyte was first innovated through a novel three-phase sulfur cathode to meet the high safety demand of solid-state Li-S batteries. In addition, by using the same “all-solid-state” battery design and a 3D column LLZO architecture, a high energy density of 338 Wh/kg and 797 Wh/L was demonstrated.
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    (2022) Wang, Haotian; Rubloff, Gary; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Li-ion battery (LIB) is a popular energy storage device that predominates the market of microelectronics due to its high energy density and light weight. In the recent trend of electrification of vehicles, LIBs also showed promise in the application of electric vehicles but the energy density of current LIBs with graphite electrode doesn’t suffice the need of long driving range. Replacing graphite electrode with alloying type electrodes that have almost ten times higher energy density is thus a necessary route to improve the energy density of LIBs. However, alloying type electrodes, such as Si and Sn, typical undergo enormous volume change (up to 310%) during Li insertion and extraction, which lead to various mechanical problems such as cracking, delamination, and pulverization. These mechanical issues eventually cause catastrophic capacity fading in LIBs and thus, are central topics for the application of alloying type electrodes in next generation LIBs. This dissertation presents a three-phase experimental study of stress development in Si electrodes and Si based solid state batteries. In the first phase, ex-situ stress characterization in single-c Si electrode was performed to validate Raman spectroscopy as a promising stress characterization technique for Si electrode. In the second phase, in-situ stress characterization in patterned poly-c Si electrode with confocal micro-Raman setup was performed, to investigate the correlation between complex geometries and stress distribution in crystalline Si electrode and the critical size effect. In the last phase, a solid-state battery (SSB) platform device with lateral layout was proposed and validated for stress characterization in Si based SSBs. The platform device can also serve as a versatile testbed for electrochemistry study of bulk SSB components and interfaces. Overall, this dissertation demonstrates a methodology that combines Raman spectroscopy, novel design of electrochemical devices, and computational modeling as a powerful tool for electrochemo-mechanics study of alloying type electrodes and SSB systems.
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    Radiation-Induced Modification of Aramid Fibers: Optimizing Crosslinking Reactions and Indirect Grafting of Nanocellulose for Body Armor Applications
    (2022) Gonzalez Lopez, Lorelis; Al-Sheikhly, Mohamad; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The goal of this dissertation was to design, synthesize, and analyze novel aramid fibers by covalently grafting nanocellulose through electron beam irradiation. These nanocellulose functionalized fibers showed enhanced strength and larger surface areas, which improves their performance and applicability in fiber-reinforced composites. Unmodified aramid fibers have smooth and chemically inert surfaces, which results in poor adhesion to many types of resins. Nanocellulose was chosen as the ideal filler to functionalize the fibers due to its reactive surface and high strength-to-weight ratio. Aramid fibers were further modified by radiation-induced crosslinking reactions as a means to avoid scission of the polymeric backbone and to further increase the fiber strength.An indirect radiation-induced grafting approach was used for synthesizing these novel nanocellulose-grafted aramid fibers while avoiding the irradiation of nanocellulose. The fibers were irradiated using the e-beam linear accelerator (LINAC) at the Medical Industrial Radiation Facility (MIRF) at the National Institute of Standards and Technology (NIST). After the irradiation, the fibers were kept in an inert atmosphere and then mixed with a nanocellulose solution for grafting. The grafted fibers were evaluated by gravimetric analysis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) spectroscopy. The mechanical properties of the synthesized fibers were studied by single fiber tensile tests. Aramid fibers were also irradiated at the MIRF in the presence of acetylene gas and triacrylate solution as a means to induce crosslinking reactions. These fibers were irradiated at both low doses and high dose rates at room temperature. A mechanism for the crosslinking of aramid fibers was proposed in this dissertation. Mechanical testing of the fibers after crosslinking showed an increase in the strength of the fibers of up to 15%. Ultra-high molecular weight polyethylene (UHMWPE) fibers were also studied, but due to an issue of entanglement of the fibers during the grafting process, their mechanical properties could not be analyzed. Future work will focus on using a better set up to avoid entanglement of these fibers. To complete the study of the radiation effects on polymers, this thesis explored the radiation-induced degradation of aromatic polyester-based resins. The composition of the resins studied included phenyl groups and epoxies, which complicate radiation-induced grafting and crosslinking reactions. Unlike aramid and polyethylene fibers, polyester-based resins have a C-O-C bond that is susceptible to degradation. The resins were irradiated at high doses in the presence of oxygen. The scission of the polymeric backbone of the polymers was studied using Electron Paramagnetic Resonance (EPR) analysis. EPR showed the formation of alkoxyl radicals and C-centered radicals as the primary intermediate products of the C-O-C scissions. The degradation mechanisms of the resins in the presence of different solvents were proposed. Changes in the Tg of the polymers after irradiation, as an indication of degradation, were studied by Dynamic Mechanical Analysis (DMA). The results obtained from this work show that irradiation of these resins results in continuous free radical-chain reactions that lead to the formation of recyclable oligomers.
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    Understanding the effect of fabrication conditions on the structural, electrical, and mechanical properties of composite materials containing carbon fillers
    (2022) Morales, Madeline Antonia; Salamanca-Riba, Lourdes G; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Carbon structures are commonly used as the reinforcement phase in composite materials toimprove the electrical, mechanical, and/or thermal properties of the matrix material. The structural diversity of carbon in its various forms (graphene, carbon nanotubes, graphite fibers, for example) makes it a useful reinforcement phase, as the properties of the composite material can be tailored for a specific application depending on the structure and properties of the carbon structure used. In this work, the incorporation of graphene/graphitic carbon into an aluminum metal matrix by an electrocharging assisted process (EAP) was investigated to create a composite material with enhanced electrical conductivity and yield strength. The increased electrical conductivity makes the composite suitable for application in more efficient power transmission lines. The increased strength makes it useful as a lightweight structural material in aerospace applications. The EAP involves applying a direct current to a mixture of molten aluminum and activated carbon to induce the crystallization of graphitic sheets/ribbons that extend throughout the matrix. The effect of processing conditions (current density, in particular) on the graphitic carbon structure, electrical properties, and mechanical properties of the composite material was investigated. The effect of porosity/voids and oxide formation was discussed with respect to the measured properties, and updates to the EAP system were made to mitigate their detrimental effects. It was found that the application of current results in some increase in graphitic carbon crystallite size calculated from Raman spectra, but many areas show the same crystallite size as the activated carbon starting material. It is likely that the current density used during processing was too low to see significant crystallization of graphitic carbon. There was no increase in electrical conductivity compared to a baseline sample with no added carbon, most likely due to porosity/voids in the samples. The mechanical characterization results indicated that the graphitic carbon clusters formed by the process did not act as an effective reinforcement phase, with no improvement in hardness and a decrease in elastic modulus measured by nanoindentation. The decreased elastic modulus was a result of compliant carbon clusters and porosity in the covetic samples. The porosity/voids were not entirely eliminated by the updates to the system, thus the electrical conductivity still did not improve. Additionally, a multifunctional composite structure consisting of a carbon-fiber reinforced polymer (CFRP) laminate with added copper mesh layers was investigated for use in aerospace applications as a structural and electromagnetic interference (EMI) shielding component. The CFRP provides primarily a structural function, while the copper mesh layers were added to increase EMI shielding effectiveness (SE). Nanoindentation was used to study the interfacial mechanical properties of the fiber/polymer and Cu/polymer interfaces, as the interfacial strength dictates the overall mechanical performance of the composite. Further, a finite element model of EMI SE was made to predict SE in the radiofrequency to microwave range for different geometry and configurations of the multifunctional composite structure. The model was used to help determine the optimum design of the multifunctional composite structure for effective shielding of EM radiation. It was found from nanoindentation near the fiber/polymer and Cu/polymer interfaces that the carbon fibers act as an effective reinforcement phase with hardness in the matrix increasing in the interphase region near the carbon fibers due to strong interfacial adhesion. In contrast, the Cu/polymer interface did not exhibit an increase in hardness, indicating poor interfacial adhesion. The EMI SE model indicated that the combination of CFRP layers, which primarily shields EMI by absorption, and Cu mesh, which predominantly shields by reflection, provided adequate SE over a wider frequency range than the individual components alone. Further, it was found that the SE of the CFRP layers were improved by including multiple plies with different relative fiber orientations.
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    (2022) Ostrovskiy, Yevgeniy; Wachsman, Eric; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Ceramics have a wide variety of applications for energy conversion and other industries because of their unique properties. Conduction of multiple charged species simultaneously enables their use as membranes, electrodes, and more. Perovskites especially, have highly tunable features, and can be modified through doping, surface coating, and microstructure. In this work, each of those approaches was used to improve and/or characterize ceramic components for either proton conducting membranes or solid oxide fuel cells (SOFCs). In the case of membranes, perovskites have limited electronic conductivity, which reduces their ability to permeate hydrogen. Through changing the dopants used in existing perovskite compositions, the electronic conductivity was improved dramatically allowing its use as an n-type conductor. This was achieved by using Pr as a dopant, which introduces electronic conductivity due its multivalent nature. It also has a favorable ionic radius for proton conduction, which is required for hydrogen permeation. In the case of fuel cells, both performance and stability need to be improved for their widespread adoption. The surface chemistry and physical properties of two major cathode materials were evaluated, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) and Sm0.5Sr0.5CoO3 (SSC). Both are susceptible to the formation of unwanted secondary phases during operation as SOFC cathodes. By studying the surface chemistry of LSCF it was possible to better understand the mechanism of cathode degradation. In the case of LSCF, it was found that electrostatic forces that result from a chemical potential difference between the bulk and surface, promote the segregation of Sr cations from the bulk which is responsible for the degradation. However, the behavior of SSC was more difficult to determine. In SSC, cation segregation was far more dependent on the grain orientation than LSCF and therefore was more difficult to quantify, and the techniques used for improving stability in LSCF were unsuccessful when applied to SSC. Additionally thin films deposited through atomic layer deposition (ALD) were tested as a means of enhancing the performance of LSCF. Due to the challenges of using ALD on porous substrates, the role of variables in the deposition process that can be widely implemented were studied, with a focus on oxygen vacancies. It was found that the choice of oxidizer and the addition of an annealing step can dramatically improve the effectiveness of thing film electrode coatings. Although ALD may not be practical for modifying SOFC electrodes, these are process steps that can be easily implemented by other researchers to improve their existing approaches. Finally, the role of microstructure was addressed as well. Tuning the porosity of SOFC anodes is essential for large scale fabrication of fuel cells and improving their performance and reliability. A microstructure featuring a hierarchal porosity was able to improve the performance of SOFC anodes, especially at lower temperatures and fuel ratios. Improvements in microstructure will allow the fabrication of larger scale SOFCs that are more reliable and mechanically stronger, with minimized performance losses associated with using a thicker anode. The primary scientific merit of this research is demonstrated in the work on cathode degradation and coatings. There the focus was on using a methodology based on a fundamental material property, oxygen vacancies, which are essential to many applications of metal oxides. With this type of approach, it is possible to apply similar techniques to other areas of research involving metal oxides or thin films. The main engineering merit of this research is evaluating the relationship between microstructure, SOFC performance, and large SOFC production. Commercialization of SOFCs requires that they are as effective as possible outside of ideal conditions (pure fuel, high temperatures). Hierarchal porosity has been shown to improve performance under both conditions and can also be applied to cathodes.
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    Investigating Aluminum Nitride As A Protection Layer For Lithium Germanium Thiophosphate Solid Electrolytes
    (2022) Klueter, Sam; Rubloff, Gary; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Lithium germanium thiophosphate (LGPS) is an attractive solid-state electrolyte material due to its exceptionally high ionic conductivity, which rivals organic liquid electrolytes. Despite this potential, other properties have impeded its adoption into solid-state batteries, particularly the poor voltage stability of the material at potentials near that of high voltage cathodes or lithium metal. Aluminum nitride (AlN) can serve as an anodic protection interlayer between LGPS and lithium metal, enhancing cell performance. AlN is grown via plasma-enhanced ALD at 250 °C using TMA and both N2 and NH3, but the deposited films show significant oxygen contamination originating from the plasma and lack crystallinity. Galvanostatic cycling and electrochemical impedance spectroscopy show that LGPS-coated cells perform better than bare cells, with expected lifetimes >3x greater in certain cases. Finally, XPS line scans highlight the slow room-temperature reactivity between AlN and evaporated lithium, and a computational model is built to aid further XPS experiments.
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    Examination of a Highly Porous Gel Polymer Interlayer for Interfacial Improvement in Solid State Lithium Batteries
    (2022) Rae, Tyler Jeffrey; Wachsman, Eric; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Solid-state lithium garnet (LLZT) electrolytes display relatively high ionic conductivity, thermal stability, and compatibility with lithium metal, which makes them encouraging for the future of lithium-ion batteries. As with many other solid electrolytes, their main weakness is poor contact and high interfacial resistance with electrodes. The use of polymer gels as interlayers has been demonstrated to reduce this interface, improving cell stability and lifespan. In this study, immersion precipitation has been explored as a preparation method to create poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) polymer membranes. The resultant microstructure is highly porous and can uptake nearly 600% its weight in liquid electrolyte when forming a gel. Polymethyl methacrylate (PMMA) and lithium fluoride (LiF) are incorporated into the membranes and evaluated for their contributions to mechanical and electrochemical properties. Membranes containing LiF showed high stability up to 4.5 V vs Li/Li+ and were analyzed in cells of composition NMC/PVDF-HFP/LLZT/Li. Specific discharge capacities up to 174 mAh/g were achieved during early cycling and showed promise for future exploration and application in quasi-solid-state lithium-ion batteries.
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    Plasma Oxidized AlOx Tunnel Barriers and Nb/Al Bilayers Examined by Electrical Transport
    (2022) Barcikowski, Zachary Scott; Cumings, John; Pomeroy, Joshua; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Results are reported for two related projects: the examination of material stability of plasma oxidized, free energy confined aluminum oxide and the evolution of the electronic structure in Nb/Al bilayers as a function of Al thickness. Al/AlOx and Nb are critical materials for solid-state quantum computing, mostly driven by the relatively large superconducting gap of Nb (1.5 meV) and ∼ 2 nm diffusion limited oxide formed on Al with room temperature thermal oxidation. Plasma oxidation and free energy confinement of AlOx with Co electrodes is used to produce homogeneous tunnel barriers with an O/Al ratio approaching Al2O3. The weeks long time stability of resulting metal-insulator-metal tunnel junctions is found to greatly improve, as resistance measured over ≈ 8 months increases by 34.0 ± 5.4 % in the confined devices (Co/AlOx/Co) compared to an increase of 95.4 ± 7.8 % in unconfined devices (Co/Al/AlOx/Co). In the second experiment, normal metal-insulator-superconductor (NIS) tunnel junctions are used to study the interplay of superconducting properties in Nb/Al bilayers as a function of Al thickness. The performance of superconducting quantum information devices is sensitive to thedetailed nature of the superconducting state in the materials, which is drastically altered through proximity in the case of dissimilar materials. I extract the effective Nb/Al quasiparticle DOS from the conductance spectra of NIS tunnel junctions with Nb/Al superconducting electrodes. The conductance spectra evolve from a primarily single-gapped structure for thin Al (< 20 nm) to a dual gapped structure at thicker Al. I present a modified Blonders-Tinkham-Klapwijk (BTK) based model interpreting the conductance spectra as a steady-state convolution of the Al-like DOS and the Nb-like DOS in the bilayer. These results inform future device design for quantum information by providing additional grounding to current proximity effect theory.
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    (2022) Nuwayhid, Ramsay Blake; Rubloff, Gary; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Lithium-ion batteries dominate portable energy storage systems today due to their light weight and high performance. However, with the continuing demand for battery capacity projected to outstrip the supply of lithium, alternative energy storage systems based on the more abundant Na and K alkali metals are attractive from both a resource perspective and their similar charge storage mechanism. Beyond limited lithium resources, there remains significant opportunity for innovation to improve battery architecture and thus performance. Nanostructured solid-state batteries (SSBs) are poised to meet the demands of next-generation energy storage technologies, with atomic layer deposition (ALD) being a powerful tool enabling high-performance nanostructured SSBs that offer competitive performance with their liquid-based counterparts. This dissertation has two main objectives: First, the development of the first reported ALD solid-state Na+ and K+ conductors are presented. Second, by leveraging the work on developing new solid- state Na+ ion conductors, a proof-of-principle nanoscale Na-SSB is fabricated and tested.ALD processes are developed for the Na and K based analogues of the well-known solid- state electrolyte (SSE) lithium phosphorus oxynitride (LiPON). In this case; NaPON and KPON. A comprehensive comparison of the structure, electrochemical, and processing parameters between the APON (A = Li, Na, K) family of materials is presented. The structure of NaPON closely resembles that of ALD LiPON, both possessing a N/P of 1, classifying them as alkali polyphosphazenes. Interestingly, KPON exhibits similar ALD process parameters to NaPON and LiPON, but the resulting film composition is quite different, showing little nitrogen incorporation and more closely resembling a phosphate glass. NaPON is determined to be a promising SSE with an ionic conductivity of 1.0 ́ 10-7 S/cm at 25 °C and a wide electrochemical stability window of 0-6.0V vs. Na/Na+. The electrochemical stability and performance of NaPON as a SSE is tested in liquid-based and all solid-state battery configurations comprised of a V2O5 cathode and Na metal anode. Electrochemical analysis suggests intermixing of the NaPON/V2O5 layers during the ALD NaPON deposition, and further reaction during the Na metal evaporation step. The reaction during the ALD NaPON deposition on V2O5 is determined to be two-fold: (1) reduction of V2O5 to VO2 and (2) Na+ insertion into VO2 to form NaxVO2. The Na metal evaporation process is found to exacerbate this reactivity, resulting in the formation of irreversible interphases leading to poor SSB performance. Despite the relatively poor performance, this work represents the first report of a nanoscale Na-SSB and showcases cryo- TEM as a powerful characterization technique to further the understanding of nanoscale SSBs. Looking forward, the intermixing during the ALD NaPON deposition does not impact the cycling of the NaxVO2 electrode in liquid-based cells, with NaPON-coated electrodes outperforming unsodiated V2O5 electrodes. This may be advantageous for the fabrication of SSBs, as the SSE deposition simultaneously could pre-sodiate a stable cathode material, excluding the need for ex-situ sodiation in liquid solutions or depositing a pre-sodiated electrode material. Strategies to pair this NaxVO2/NaPON cathode/electrolyte with a stable anode are discussed, with a focus on the ultimate realization of a high-performance Na-SSB. This work highlights the high reactivity of Na compared to Li based battery chemistries, not only necessitating the need for interfacial coatings in Na SSBs, but also the extreme caution required during fabrication of Na-SSBs or liquid sodium- ion batteries.