Coatings are widely used to mitigate corrosion of structural steel in aggressive humid environments. However, the service life is often diminished in aggressive environments. Repair of coatings can be costly due to materials, labor and environmental controls. So, in search for novel coatings, Chemically Bonded Phosphate Ceramic (CBPC) coating was investigated for marine bridge application. The research on CBPC coating considered various exposure environments such as inland, beach, salt-fog, wet and alternate wet and dry exposure to identify the degradation mechanism. To assess the corrosion damage, the coating was evaluated by visual inspection, thickness, adhesion, microscopy and X-ray diffraction. The CBPC coating degraded initially due to alternate wet and dry exposure. The unreacted coating constituent reacted further in moist environment to form magnesium phosphate hydrate and enhanced bulk coating porosity. That facilitated moisture to the coating substrate and formed apparent protective iron phosphate hydrate by interaction with steel substrate to the coating constituents. Passive-like conditions were observed in wet test of chloride-free solutions for the formation of hydration product of magnesium but that type of hydrate was not identified in chloride solution for the apparent high solubility. The resolved coating impedance parameters were introduced to characterize the bulk ceramic degradation. The solution resistance did show a decrease for all samples due to leaching of minerals from the bulk material. The resolved pore resistance did not show any distinct change, though there was an indication of bulk coating degradation by MIP. Water saturation level during exposure was also calculated from the resolved capacitance. An approach was proposed to transfer the pre-exponential term, Yo to coating capacitance, CC for ceramic coating. The estimated value of the coating capacitance from the developed technique indicated early saturation with water during exposure due to the porosity. So, the extent of CBPC coating permeability and degradation could not be resolved only by conventional analysis approaches. However, the formation of iron hydrogen phosphate hydrate and iron phosphate hydrate from reaction of unreacted coating constituents was thought to provide apparent enhanced corrosion protection but there is a probability of steel substrate corrosion in extended exposure in humid environment.

Stricter regulations concerning emissions from road traffic and increasing fuel prices has lead to an interest in hybrid electric vehicles (HEVs). Today even manufacturers of heavy duty vehicles are introducing hybrid alternatives. Batteries are expensive and a complex part in HEVs, and ways of determining a battery’s capacity is a current research topic. When a battery is used it ages, i.e. the capacity decreases and the impedance rises. Since battery cost is high, it is important to be able to determine battery ageing properly. The focus of this master thesis has been on impedance measurement methods for Li-ion batteries. The work has been carried out in cooperation with Scania CV AB. When a battery is aged, the impedance increases. Monitoring ageing mechanisms could enable increased lifetime of the batteries through optimized usage in for example heavy duty hybrid vehicles. In this work, Hybrid Pulse Power Characterization (HPPC) has been compared with Electrochemical Impedance Spectroscopy (EIS). A major difference between these methods is that HPPC uses pulses of high direct current, whereas a small alternating current perturbation is used in EIS. EIS give information about different mechanisms influencing the battery impedance, e.g. internal resistance and charge transfer resistance, but requires expensive and complex laboratory equipment. HPPC gives less detailed information about the impedance, but is more similar to field applications for a vehicle. A literature survey showed that much research is conducted on in-situ impedance measurements of batteries. One example is the long-term demonstration of an Impedance Measurement Box (IMB), which is currently carried out at Idaho National Laboratory. The method uses a sum-of-sines signal consisting of octave harmonics for a fast impedance measurement with good precision. The results showed a good correlation with laboratory EIS measurements. The experimental part of this project suggest that a linear correlation  exists between the discharge resistance from HPPC measurements and the sum of internal resistance and charge transfer resistance from EIS measurements. The linear fitting did not have very good R-squared value but a residual analysis showed that the residuals were randomly scattered around zero, indicating that a linear fitting is suitable. However, the precision of the results is too poor for the correlation to be useful in a real HEV application. Additional work to improve the linear fitting is recommended. Furthermore, it was showed that AC-components have to be used as a measurement signal in order to measure the complex impedance of a battery. A paired t-test was conducted in order to study if noise could be used as that signal for a battery under load. The impedance at 100 Hz was calculated, which corresponds to the second harmonic of the power grid. The difference between this impedance and the impedance measured at 100 Hz with EIS was statistically tested. For shorter times pans (in this case 20 milliseconds) after applying the DC pulse, using noise cannot be ruled out for measuring a battery’s impedance under load. But for longer time spans after applying the DC pulse (in this case 1.3 seconds), there was a significant difference between the two methods. Concentration gradients caused by mass transfer limitations could be causing this effect.

In this paper, I sought to identify and develop a protocol on electrode arrays as a result of rapid aging by applying rapid current over time. We, however, apply a different approach by using phosphate buffer solution (PBS) to mimic the conditions of the body. Here we have established an in vitro protocol for accelerated aging, a process that involves testing in extreme conditions such as oxygen, heat, sunlight, humidity, and vibration aimed at speeding the normal aging process of items; on commercially available shape memory polymer electrode arrays from Qualia over a period of 30 days in PBS. Two electrode arrays were placed in 37°C and 2 were placed in 57°C. Open lead electrochemical impedance spectroscopy (EIS) was conducted on the electrode arrays. Overall, the results showed there were differences in average impedance during this accelerated aging protocol. At 37°C we see that the average impedance values increased as the electrodes were aged at 1kHz from an average of 4.15E6 to 9.14E6 Ohms. At 57°C electrode arrays 4 and 5 showed strong P values well above 0.05, but average impedance increased drastically from 3.27E6 to 9.97E6 and P value of 0.04 from measurement day 24 to day 30. This indicated to us that the electrode could be experiencing some delamination. In addition, this could be because the Qualia nerve cuffs tested were "B" grade, so changes in impedance could be due to the integrity of the device. This would tell us that these electrode arrays would not be capable to withstand long – term recording for up to 240 days. As a result, rejecting the hypothesis that this protocol would show no change in impedance levels for a simulated aging period of 240 days. Although this protocol was not in a perfect setting and the quality of the electrodes were not up to standard, this gave us insight into the electrochemical properties of SMP electrodes which will be useful when we bio-fabricate our own electrodes to study gastrointestinal (GI) disorders.

Electrode microstructure influences ionic transport and electronic transport and is a key factor that affects lithium-ion battery performance. Non-uniform microstructure or heterogeneity in battery electrodes has long been observed and leads to non-uniform transport properties. This work provides a better understanding of in-plane heterogeneity at millimeter length scale and through-plane heterogeneity at micrometer length scale, through a combination of experiment and modeling. The first part of this work develops the aperture probe technique, which is an experimental method and associated model to locally estimate ionic transport, represented by MacMullin number, in the electrode. By generating contour maps of MacMullin number, the in-plane variation of ionic transport is visualized in the electrodes. The local ionic transport measurement technique is validated by comparing with another measurement technique and showing an agreement between the results obtained from the two techniques. The second part of this work focuses on characterizing dual-layer anodes that consist of two layers of coating with distinctly different microstructures. The aperture probe technique was adapted to determine the MacMullin numbers in the two layers separately. The method was validated by a series of virtual experiments and by comparing in one case to an electrode film that was delaminated from the current collector and experimentally sampled from both sides. Because both the electronic transport and the ionic transport are found to be related with the electrode microstructure, it is of interest to understand how these two transport properties relate to each other. The local electronic conductivity and MacMullin number of several commercial-grade electrodes were mapped. The correlation between the two transport properties is distinct for each electrode and significant at length scales larger than about 6 mm. The last part of this work investigates how heterogeneity of ionic transport affects the cycling performance of a lithium-ion cell. A localized MacMullin number measurement is made to characterize the ionic transport heterogeneity of electrodes prior to cycling. Then synchrotron-based X-ray diffraction is applied to analyze the heterogeneity in state of lithiation after high-rate cycling. When comparing the ionic transport map and the state-of-charge map, no strong correlation is observed. While this experiment was inconclusive, it suggests that other factors are more responsible for spatial variations in state of lithiation.

The field of energy storage has improved drastically within the last two decades. Batteries of various chemistries have been relied on to provide energy for numerous portable electronic devices. Lithium-ion cells, when compared to other chemistries have been known to provide outstanding energy-to-weight ratios and exhibit low self-discharge when not in use [1]. The aforementioned benefits in conjunction with decreasing costs have made lithium-ion cells an exceptional choice for use in electrical vehicles (EVs). Battery Management Systems (BMS) in EVs are responsible for providing estimates for values that are indicative of the battery pack’s present operating condition. The current operating condition could be described by State of Charge, power fade, capacity fade and various other parameters [2]. Importantly, it is essential for the estimation technique to adjust to fluctuating cell characteristics as the cell ages, in pursuance of having available accurate estimates for the life time of the pack. In order for the estimation technique to properly estimate the desired quantities, a mathematical model capable of capturing cell dynamics is desired. There are various proposed methods recommended for mathematically modeling a cell, namely equivalent Circuit modeling, electro-chemical modeling and impedance spectroscopy. Consequently, in order to ensure mathematical models are accurate and further to have the ability to compare the proposed models, it is essential to have available data gathered from a given cell at specific operating conditions. This Master’s thesis outlines the development of a lithium-ion cell tester that is capable of controlling, monitoring and recording parameters such as current, voltage and temperature. The Dual capability of obtaining data from standardized cell tests as well as high frequency cell tests is fascinating and intriguing. As this capability holds the possibility of reducing cost otherwise spent on man hours and equipment which are both paramount in any industrially automated process. / Thesis / Master of Applied Science (MASc)

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No description available.

Commercial aluminum (Al) alloys are often precipitation strengthened to improve strength and wear resistance. However, localized corrosion due to the galvanic coupling between the precipitates and Al matrix often leads to degraded performance when these alloys are exposed to corrosive environment. In this work, Al-based solid solution was synthesized to simultaneously improve the strength and corrosion resistance of Al alloys, which ultimately led to high tribocorrosion resistance. Specifically, the effects of testing condition (e.g. sliding frequency) and alloying effects (e.g. Mn and Mo) on the corrosion and tribocorrosion behavior of Al-based binary and ternary solid solutions were studied. To understand the effects of wear condition on the depassivation-repassivation kinetics during tribocorrosion, in the first study, the tribocorrosion behaviors of Al-20 at.%Mn alloys were investigated in simulated seawater by changing the sliding frequency from 0.05 to 1 Hz in reciprocal motion. The results show that the depassivation rate of passive film increased with increasing sliding frequency. Mechanical wear also increased with increasing sliding frequency, which was mainly related to the increase of coefficient of friction and real contact area. Chemical wear tended to increase with scratching frequency, most likely due to faster repassivation kinetics at lower frequency. The surface layer was analyzed by cross-sectional transmission electron microscopy, indicating the passive film was primarily consisted of aluminum oxide where manganese was selectively dissolved. Despite extensive past research, the fundamental understanding of the alloying effects on the atomistic structure, composition, and chemical state of the passive layer of Al alloys and their formation mechanism is still not well understood. In the second study, the effects of Mn on the aqueous corrosion of Al-Mn alloys were investigated. It was confirmed that Mn alloying could enhance the corrosion resistance of Al without participating in the surface oxidation. Atom probe tomography analysis confirmed the absence of Mn in the anodized and corroded surface of Al-Mn alloys. The selective dissolution of Mn in these alloys was believed to increase the free volume at the metal/oxide interface to facilitate the formation of a denser, thinner oxide layer with closer to stoichiometry composition, leading to its enhanced corrosion resistance than pure Al. Lastly, to better understand the corrosion and tribocorrosion resistance of Al-based lightweight concentrated alloys and the effects of alloying concentrations on the structure and property of the passive layer, the third study investigated the effects of a passive element (Mo) and non-passive element (Mn) on the corrosion and tribocorrosion behavior of Al-Mn-Mo alloys. Specifically, Al80Mn8Mo12 exhibited higher corrosion resistance than Al80Mn20 due to the formation of a more compact and less defective passive film, as explained by the roles Mo played in both the substrate and the passive film. It was found that the pitting potential and corrosion current density of Al-Mn-Mo increased with Mo%. The effect of Mo alloying concentration on the tribocorrosion behavior of Al-Mn-Mo alloys was investigated as well. Adding Mo to Al-Mn alloys led to a lower wear and tribocorroison resistance of Al-Mn-Mo alloys. In addition, decreasing Mn and Mo concentrations resulted in a reduction of the tribocorrosion resistance in the ternary alloy, which was mainly dominated by the mechanical response under the selected testing conditions. / Doctor of Philosophy / Various critical current and future applications in the fields of aerospace, transportation, energy, and biomedical industries require not only a strong and tough metal, but one that is robust and reliable when interacting with some very corrosive environment. Such corrosive environment is testing the limits of most engineering metals and challenging the current understanding of the underlying degradation mechanism. For example, strength and wear resistance in most precipitation-hardened Al (aluminum) alloys is often achieved at the expense of sacrificed corrosion resistance, mainly due to micro-galvanic coupling between the soft matrix and hard precipitates. In addition, the performance of Al alloys deteriorates dramatically when there is combined wear and corrosion, i.e. tribocorrosion attack at the surface, due to the depassivation on the wear track as a result of mechanical removal of the passive film. Recent study shows that alloying Al with appropriate transition metals in supersaturated solid solution simultaneously improves the corrosion and wear resistance of Al. In this thesis, Al-Mn and Al-Mn-Mo solid solutions was synthesized and studied to understand the effects of testing condition (e.g. sliding frequency) and alloy composition (e.g. Mn and Mo concentration) on the corrosion and tribocorrosion behavior. First, the depassivation mechanism during tribocorrosion of Al-Mn alloys was investigated by performing tribocorrosion test using different sliding frequency from 0.05 to 1 Hz in 0.6 M NaCl aqueous solution. Results showed that both chemical and mechanical wear increased with increasing frequency. The mechanical wear increased with scratching frequency due to faster depassivation rate and increased real contact area, while chemical wear increased with frequency due to higher repassivation kinetics. Secondly, the effects of Mn on the aqueous corrosion and passivation of Al-Mn solid solution alloys were investigated by electrochemical experiments and advanced surface characterization. It was found that Mn addition enhanced the corrosion resistance of Al without participating in the surface oxidation. A denser, thinner oxide layer was formed on Al-Mn due to the increased free volume at the metal/oxide interface as a result of Mn dissolution. Lastly, the effects of alloying concentration on the aqueous corrosion and tribocorrosion of Al-Mn-Mo alloys were studied experimentally. The pitting potential and corrosion current density of Al-Mn-Mo were found to increase with Mo%. The passive film thickness depended on the total alloy concentration, while its compactness and defect density on the individual ones. The tribocorrosion resistance of Al-Mn-Mo alloys decreased with increasing Mn and Mo concentrations. In summary, the results from this thesis develop mechanistic understanding of the corrosion and tribocorrosion mechanisms of Al-based solid solution alloys, which sheds light on a new alloy design strategy for making lightweight, strong, and corrosion-resistant metals.

The National Environmental Policy Act (NEPA) declared the Federal government's commitment to comprehensive environmental protection. The cutting-edge of NEPA is its requirement for including an Environmental Impact Statement (EIS) for all major Federal actions significantly affecting the environment. Opinions about the effectiveness of NEPA's EIS requirement range along a continuum. On one extreme are those who view the NEPA process as essentially procedural and overshadowed by other environmental legislation which provide explicit standards of environmental protection for specific environmental values. On the other extreme are those who believe that NEPA provides substantive, comprehensive, and holistic environmental protection of all environmental values. Most of the research on NEPA and its EIS reqUirement has revolved around the act's procedural and substantive mandates. However, despite the proliferation of non-NEPA environmental legislation mandating the protection of such environmental values as air and water quality, land use, and wildlife and endangered species, very little attention has been paid to the role of the mandates and requirements of these legislation in the EIS process. This research effort characterizes the role of NEPA's EIS process in light of the mandates and requirements of this body of non-NEPA legislation to determine the extent to which it addresses the substance of environmental impact evaluation. Specifically, this research focuses on the following questions: • Is the body of non-NEPA legislation sufficiently comprehensive to cover the entire spectrum of environmental values making NEPA's EIS requirement redundant? • Does NEPA enhance the avenues for public participation in government decision-making provided by non-NEPA legislation? • Does NEPA address the impacts of large scale projects, public programs and policy decisions, and cumulative impacts in a more comprehensive manner than non-NEPA legislation? • Does NEPA enhance coordination and integration among Federal agencies in ensuring that environmental issues are addressed comprehensively? The study focuses on the civil works program of the U.S. Army Corps of Engineers (Corps). As such, all conclusions are applicable only to the Corps and are not generalized to other agencies to which NEPA's requirements apply. The study involved a literature review on the role of NEPA in Federal agency planning and decision-making and the development of five research hypotheses with respect to the questions outlined earlier. These hypotheses were then evaluated through a critical review of NEPA and of the role of NEPA and other legislation in Corps activities, and a case-study of a Corps-directed EIS of the Metropolitan Denver Water Supply System. This research effort concluded that there is a relative lack of redundence among the environmental policy and requirement provisions of NEPA and those of non-NEPA legislation—what exists is a complementary, albeit tenuous relationship. Complementary, because in theory and intent: • NEPA proclaims a national policy for all environmental values while specific legislation focus only on specific environmental values; • NEPA does not contain specific standards or requirements but draws from those contained in other legislation; • in the absence of NEPA, assessments of a project's impacts to specific environmental values would be disjointed and incomplete; • the antagonistic and synergistic impacts to various values preclude individualized assessments—such impacts may not be fully addressed in the absence of NEPA; and • NEPA's public participation mechanisms as well as its requirements to ensure coordination among agencies are necessary and complementary to the focused provisions of other legislation. Tenuous, because this complementary intent has not been fully realized in practice. While the intent of NEPA was to ensure the complete and comprehensive alignment of NEPA and non-NEPA legislation, the realities of NEPA’s implementation have brought to light a variety of obstacles. These include: • inadequate guidance on NEPA compliance with other legislation; • inadequate integration among agency planning procedures and procedures for compliance with the requirements of various legislation, and inadequate inter-agency integration mechanisms; • redundant pubic participation procedures; and • a general lack of internalization in Federal agencies of the true intent of NEPA’s national policy declaration. Recommendations to surmount these obstacles include among others: developing comprehensive guidance on NEPA compliance with other legislation; ensuring that agencies’ compliance procedures are standardized and consistent with one another; developing processes whereby NEPA's public participation procedures subsume those of other legislation; and creating a fully represented Federal task force to develop and recommend detailed options for streamlining NEPA implementation. / Ph. D.

State-of-Health (SoH), a specified measure of stability, is a critical parameter for determining the safe operating area of a battery cell and battery packs to avoid abuse and prevent failure and accidents. A series of experiments were performed to evaluate the performance of a 4P1S battery array using electrochemical impedance spectroscopy to identify key frequencies that may describe battery state of health at any state of charge. Using a large sample number of cells, the state of health frequency, fSoH, for these LiFePO4 26650 cells is found to be 158 Hz. Four experiments were performed to evaluate the lifetime in different configurations: single-cell at 1C (2.6A), single-cell at 10C (26A), four cells in parallel at 10C (ideal match), and four cells in parallel (manufacturer match). The lifetime for each experiment set degraded substantially, with the final parallel series reaching end of life at 400 cycles, a 75.32% reduction in life compared to operating solo. Analysis of the fSoH data for these cells revealed a change in imaginary impedance at the critical frequency that corresponded to changes in the capacity and current data, supporting the development of a single-frequency diagnostic tool. An electrochemical model of the battery was generated, and it indicated the anode material was aging faster than the SEI layer, the opposite of normal cell degradation. A post-mortem analysis of cells from three configurations (baseline, single-cell, and parallel-cell) supported the modeling, as physical damage to the copper current collector in the anode was visible in the parallel-connected cell. / Ph. D.