The purpose of this study was to examine the performance of several generic types of organic protective coatings as a corrosion protection method for the interior of subsea pipelines in sour gas media. The sour gas environment was simulated in the laboratory by the use of an Autoclave and the performance of the organic coatings was studied via the use of Electrochemical Impedance Spectroscopy (EIS) and Linear Polarization Resistance (LPR) tests to determine the coatings resistance, capacitance and corrosion behavior before and after the exposure to sour gas environment. The coating degradation and the corrosion products formed were examined by the use of SEM/EDS. The results indicated that both FBE and Novolac Epoxy coatings had excellent adhesion properties and chemical resistance. The Amine-Cured Novolac Epoxy coating exhibited good adhesion properties and chemical resistance. However, the Phenolic Epoxy coating started to degrade over time and corrosion took place under the coating.

The objective of this research was to develop a novel technique for mechanical treatment to manipulate the microstructure of Nickel-Manganese-Gallium Hesuler alloys to increase anisotropy, which can lead to higher magnetocaloric properties. Ni2+xMn1-xGa intermetallics have the potential to be employed in magnetic refrigeration devices including residential refrigerators, heat pumps, and air conditioning. Solid-state magnetic refrigeration systems are smaller, quieter, and reduce energy consumption by 20% compared to existing conventional vapor-cycle refrigeration devices which rely on harmful hydro-fluorocarbon gases and pump millions of tons of greenhouse gases into the atmosphere. The magnetic refrigeration market is predicted to reach US$ 315.7 Million by 2022. Magnetic refrigeration systems can also be used in electronic systems and the space industry. The current state-of-the-art magnetic refrigeration systems use expensive rare earth elements including Gadolinuim (Gd). The need to replace Gd and other rare earth elements with cheaper and more available elements led to other alloys including Ni-Mn-Ga. By understanding the processing-microstructure-property relationship of Ni-Mn-Ga alloy, it is possible to manipulate the microstructure in order to obtain higher refrigeration capacity. It is a promising alternative to rare earth elements and improves national security by minimizing foreign dependence on the import of rare earth metals. This novel in situ study establishes that twin boundaries can be manipulated in a polycrystalline Ni-Mn-Ga alloy. This results in a change in magnetocrsytalline anisotropy, which leads to a higher magnetic cooling power. Mechanical loading in a preferred direction, traditionally referred to as a training process, was able to move the twin boundaries, and the combination of focused ion beam imaging linked specific movement with mechanical loading. This technique, in situ monitoring process, can be utilized to devise training procedures for future iterations of magnetocaloric and shape memory alloys.

High hardness steels can be affected by delayed brittle cracking often attributed to hydrogen embrittlement. Improved resistance to hydrogen embrittlement would be beneficial to many industries including military, automotive, and high-rise construction. While other prevention methods include coating, trapping, and barriers, design efforts in this study were focused on improving intrinsic properties to be more resistant to hydrogen embrittlement. Four alloys targeting 477 – 534 HB were designed and produced in-house and compared against a commercial grade 500 HB alloy. Charpy V-notch (CVN) impact toughness and tensile specimens were made according to ASTM E23 and ASTM E8 to characterize mechanical properties. Hydrogen embrittlement testing was performed using ASTM E8 test samples electro-chemically charged in either sodium hydroxide or sulfuric acid with thiourea in solution. Results suggested that alloying for lower strength and better toughness by reducing C and Mn results in lower hydrogen embrittlement susceptibility.

Understanding the mechanisms that control the mechanical behavior of microscale actuators is necessary to design an actuator that responds to an applied actuation force with the desired behavior. Micro actuators which employ a diaphragm supported by torsional hinges which deform during actuation are used in many applications where device stability and reliability are critical. The material response to the stress developed within the hinge during actuation controls how the actuator will respond to the actuating force. A fully recoverable non-linear viscoelastic response has been observed in electrostatically driven micro actuators employing torsional hinges of silicon covered with thin metal films. The viscoelastic response occurs over a time period of 50 minutes at an operating temperature of 35°C. This viscoelastic phenomenon is similar to that reported in articles addressing anelastic behavior associated with viscous grain boundary slippage and dislocation bowing. In order to investigate this viscoelastic response as a function of metal film composition and thickness, bi-layer torsional hinge actuators consisting of Si with a deposited metal layer were designed to exhibit similar stress levels as the electrostatically driven micro actuators. The test devices were fabricated using common semiconductor fabrication techniques. The actuators were micromachined by deep etching 100mm diameter, 425µm thick, double side polished, single crystal (100) wafers to create a 4.5µm thick device layer. Subsequent etching of the device layer released the fixed-fixed torsional hinge test actuators. Physical vapor depositions of Au, Al and Al-Ti in two different thicknesses (100nm, and 150nm) were deposited in order to investigate the impact of metal film thickness and composition on the viscoelastic response. Grain sizes of the deposited films were estimated using backscattered electron images. Rotational actuation of the test actuators was achieved by using a modified Ambios XP-1 surface profiler that applies a constant force of 0.28mN while measuring the displacement of the actuator with respect to time. The viscoelastic response was observed in the test devices with Au and Al thin films indicating that this phenomenon is attributable to the stresses induced on the torsional hinge. Results indicate that the viscoelastic response was not observed in AlTi thin films consisting of 0.3at% titanium. Two theoretical models are presented that discuss the mechanism associated with the viscoelastic response as well as a method for inhibiting these mechanisms by the addition of an alloying element to form a second phase precipitate.

As applications for thermoplastic composites increase, the understanding of their properties become more important. Fabrication methods for thermoplastic composites continually improve to match designs specifications. These advanced thermoplastics have begun to show an improvement in mechanical properties over those found in thermoset composites commonly used in industry. Polyaryletherketones (PEK) have high service temperatures, good mechanical properties, and improved processing capabilities compared to thermoplastics used in the past making them important to the aerospace industry. The wide range of types of PEK make them suitable for a variety of applications, but selection of specific chemistries, processing parameters, and composite stack-ups determine the mechanical properties produced. Differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) were used to determine crystallinity and chemical properties of several polyaryletherketones. Tensile, compressive, and Mode I interlaminar fracture toughness tests were conducted to analyze mechanical properties of these advanced thermoplastics. Several fabrication processes were also tested to determine optimal consolidation and aesthetic appearance of structural members. All testing was conducted at The Boeing Company in Seattle, Washington. Because all testing and conclusions are proprietary a general synopsis of the experience will be presented.

Water soluble conjugated polyelectrolytes (CPEs), which fall under the category of conductive polymers, possess numerous advantages over other conductive materials for the fabrication of electronic devices. Namely, the processing of water soluble conjugated polyelectrolytes into thin film electronic devices is much less costly as compared to the processing of inorganic materials. Moreover, the handling of conjugated polyelectrolytes can be performed in a much more environmentally friendly manner than in the processing of other conjugated polymers because conjugated polyelectrolytes are water soluble, whereas other polymers will only dissolve in toxic organic solvents. The processing of electronic devices containing inorganic constituents such as copper indium gallium selenide (CIGS), is much more expensive and poses much greater environmental risks because toxic metals may be released into landfills or waterways upon cell disposal.75 Because conjugated polyelectrolytes enjoy an assortment of advantages over other materials for the manufacturing of thin film electronic devices, there is globally vested interest in the researching of their properties. Despite the fact that CPEs can serve as efficient electron transport mediums, devices such as organic solar cells cannot realize their highest efficiencies unless the morphology of CPEs is precisely controlled. Charged surfactants can electrostatically and ionically interact with CPEs, and when introduced in specific concentrations, molar ratios, and temperature ranges, will aid in a ‘coil to rod’ transition of the CPE, wherein polymer chains undergo intramolecular transitions to obtain rigid-rod morphologies. The kinetics and thermodynamics of the ‘coil to rod’ transition are heavily dependent upon the type(s) of charged surfactant complexed with the CPE (i.e. on the surfactant architecture). By performing UV/Vis Spectroscopy and Fluorometry on dilute polymer/surfactant solutions, Polarized Optical Microscopy (POM) and Small Angle X-Ray Scattering (SAXS) on high concentration polymer/surfactant solutions, and Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) on solid-state polymer/surfactant samples, the role of various surfactant architectures on the kinetics and thermodynamics of the ‘coil to rod’ transition was studied. The liquid crystalline physical properties and the extent of solid state crystallinity were also investigated. Through an analysis of the data obtained from these various techniques, it was found that the ‘coil to rod’ transition is progressively favored when the alkyl chain length of a single tailed surfactant is sequentially increased, and that as the concentration of double-tailed surfactant increases, the ‘coil to rod’ transition is negated.

<p>We explore the effect of size on the phase stability of nanosystems by comparing calculated trends with the annealing behavior of nanoparticles (NPs) initially in a core-shell configuration. The NPs are characterized using a variety of transmission electron microscopy (TEM) techniques.</p> <p>We first theoretically consider the equilibrium within a Au-Pt NP of a given size. When considering the contribution of surface and interface energies, we note the appearance of a restricted composition range of the phase diagram over which the liquid and solid phases cannot coexist in a core-shell configuration. A critical radius of ",42 nm is identified below which the NP is single-phased for any composition. It is demonstrated that both branches of the miscibility gap of the Au-Pt phase diagram shift towards the Au-rich composition with increasing curvature. The magnitude of the shift is found to be strongly correlated with the coupling of nonlinear terms entering the Gibbs energy. The main contribution to the shift arises from the composition-dependent surface energy, calculated by considering the selective adsorption of Au to the surface, evaluated using the available thermodynamic properties of the Au-Pt system.</p> <p>An array of TEM-related analytical methods were developed or adapted for the characterization of individual NPs. In particular, chemical maps with quantitative information from a NP with a spatial resolution of '" 1.2 nm could be achieved, with their corresponding error analysis. We introduce an algorithm to retrieve the radial elemental composition from the projected chemical map of a NP if a spherical symmetry can be assumed and test it with NPs of known structures. We also present a technique to determine the composition of a NP having one of the elements depleting during analysis, and test it experimentally with 5-20 nm Au-Ag NPs. Typically, for every Ag characteristic X-ray detected, one Ag atom is lost to knock-on damage. We discuss the detection limit of the method as a function of NP size and composition.</p> <p>We follow the structural evolution of a ",20 nm Au(core) Pt(shell) NP during annealing at various temperatures between 300 and 800 °e. At low temperatures, interdiffusion occurs between the core and the shell, while at temperatures abovt: ",600 °e, the configuration evolves towards one composed of Au- and Pt-rich spherical caps, separated by a relatively fiat interface. We could measure a 5-10% shift in the composition of each phase with respect to the bulk phase diagram that we assigned to capillarity effect. The shift agrees qualitatively with the calculated trends. The ratio of the surface to the interface energy is measured directly from a TEM micrograph of a segregated NP and is in close agreement with the calculated ones.</p> <p>This work contributes to the understanding of the phase stability of binary NPs. The prospect of extending these studies to NPs of other bimetallic systems while probing their properties seems promising, especially in view of their catalytic, magnetic and optical potential.</p> / Doctor of Philosophy (PhD)

There is great need to understand the mechanical properties of lead-free alloys—an alternative of lead-based alloys—to address the environmental problems associated with the use of lead-based materials in microelectronics. In this work, the microstructures of Bi57In26Sn17 lead-free alloy were examined using Optical Microscopy and Energy Dispersive X-ray Spectroscopy analysis. The micro-indentation technique was used to study the mechanical properties of Bi57In26Sn17 lead-free alloy. The experimental results of the hardness and contact modulus were presented and discussed. Local creep during the indentation was observed from the load-displacement curves. The Vickers hardness (HV) increases with the decrease of the indentation depth, suggesting that the alloy exhibits indentation size effect.

Silicon (Si) has been considered as a promising negative electrode material for lithium ion batteries (LIBs) because of its high theoretical capacity, low discharge voltage, and low cost. However, the utilization of Si electrode has been hampered by problems such as slow ionic transport, large stress/strain generation, and unstable solid electrolyte interphase (SEI). These problems severely influence the performance and cycle life of Si electrodes. In general, ionic conduction determines the rate performance of the electrode, while electron leakage through the SEI causes electrolyte decomposition and, thus, causes capacity loss. The goal of this thesis research is to design Si electrodes with high current efficiency and durability through a fundamental understanding of the ionic and electronic conduction in Si and its SEI. Multi-scale physical and chemical processes occur in the electrode during charging and discharging. This thesis, thus, focuses on multi-scale modeling, including developing new methods, to help understand these coupled physical and chemical processes. For example, we developed a new method based on ab initio molecular dynamics to study the effects of stress/strain on Li ion transport in amorphous lithiated Si electrodes. This method not only quantitatively shows the effect of stress on ionic transport in amorphous materials, but also uncovers the underlying atomistic mechanisms. However, the origin of ionic conduction in the inorganic components in SEI is different from that in the amorphous Si electrode. To tackle this problem, we developed a model by separating the problem into two scales: 1) atomistic scale: defect physics and transport in individual SEI components with consideration of the environment, e.g., LiF in equilibrium with Si electrode; 2) mesoscopic scale: defect distribution near the heterogeneous interface based on a space charge model. In addition, to help design better artificial SEI, we further demonstrated a theoretical design of multicomponent SEIs by utilizing the synergetic effect found in the natural SEI. We show that the electrical conduction can be optimized by varying the grain size and volume fraction of two phases in the artificial multicomponent SEI.

This dissertation is focus on the study of solid-electrolyte interphases (SEIs) on advanced lithium ion battery (LIB) anodes. The purposes of this dissertation are to a) develop a methodology to study the properties of SEIs; and b) provide guidelines for designing engineered SEIs. The general knowledge gained through this research will be beneficial for the entire battery research community.