This thesis deals with novel electrolytes for magnesium batteries. Prepared electrolytes were composed of affordable solvents and chemicals, which can be handled at normal laboratory conditions. Specifically, solutions of tetrahydrofurane and dimethylsulfoxide with magnesium chloride, aluminium chloride, nitrilotriacetic acid and disodium ethylenediaminetetraacetic acid, were prepared. To determine electrolyte ability of magnesium stripping and deposition, the cyclic voltammetry was used. The kinetics of electrochemical reactions in terms of polarization resistance was studied by electrochemical impedance spectroscopy. Based on scanning electron microscopy and EDS analysis, the effect of atmospheric oxygen and humidity on magnesium electrode corrosion during cycling was discussed.

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Numerous methods have been developed to measure corrosion potential relating to chloride infiltration in concrete, including an emerging application of electrochemical impedance spectroscopy (EIS). EIS involves measurements of electrical impedance to evaluate the corrosion potential of steel reinforcement in concrete. With EIS, current is injected vertically into the concrete bridge deck between the surface and the embedded reinforcing steel, usually the top mat, to evaluate the degree to which the reinforcing steel is protected from chloride infiltration by the entire bridge deck system. The objectives of this research were to 1) investigate the sensitivity of EIS measurements obtained at various frequencies to specific deck properties, 2) recommend a particular frequency or range in frequency at which impedance measurements can differentiate among various levels of corrosion protection for reinforcing steel in concrete bridge decks, and 3) compare impedance values measured at the recommended frequency(ies) to more traditional test measurements relating to corrosion of reinforcing steel in concrete bridge decks. This research involved impedance testing of 25 concrete slabs, divided into five sets. The effects of sealant presence, curing time, temperature, moisture content, cover depth, water-to-cementitious materials ratio, air content, chloride concentration, and epoxy coating condition on individual impedance measurements were evaluated. For the controlled laboratory experiments, sealant presence, curing time, temperature, moisture content, cover depth, water-to-cementitious materials ratio, air content, and epoxy coating condition were shown to have a statistically significant effect on impedance measurements, with p-values less than 0.05. The statistical analyses indicated that impedance testing in the frequency range of approximately 100 Hz to 1 kHz would be expected to provide the best data about the degree to which the reinforcing steel is protected from chloride infiltration by a bridge deck system. In this frequency range, a high level of differentiation among levels of corrosion protection is expected, and a high speed of data collection is also possible. For the uncontrolled laboratory experiments, a single frequency of 200 Hz was selected for impedance testing. Statistical analyses were performed to compare impedance with more traditional test measurements relating to corrosion of reinforcing steel in concrete bridge decks. Longitudinal and transverse cover, dry and wet resistivity, dry and wet half-cell potential, dry linear polarization, and chloride concentration were determined to be correlated with impedance, with p-values less than 0.15.

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京都大学 / 新制・課程博士 / 博士(工学) / 甲第24632号 / 工博第5138号 / 新制||工||1982(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 陰山 洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Li-ion batteries (LIB) are used in many applications because of their high-power/energy density, long life cycling, and low self-discharge rate. The use of LIB continues to grow every day, and the necessity for proper safety standards grows as well. A key aspect for safe utilization of LIB is determining their safety and remaining useful life (RUL). Battery characteristics degrade over time under normal and extreme operating conditions and modeling the electrochemical processes can improve RUL estimations. Extreme operating conditions such as abnormal temperatures and charge/discharge rates are believed to exacerbate the rate of degradation. Li-ion batteries are also susceptible to mechanical damage, which may lead to an electrical short. In severe cases, mechanical damage causes a thermal run away, and possibly explosions or fires. In the event of a car accident, battery packs can be damage without an electrical short or immediate thermal run away. Currently, there is no reliable batt / Mechanical Engineering

<p dir="ltr">Portable sensing enables an enhanced form of disease monitoring due to its accessible form-factors, low costs, and insights into user health, along with enhanced detection methods due to its many use cases for at-home or in-field applications. To that end, electrochemistry has been a widely used technique in characterization, detection, and diagnostics. Electrochemical Impedance Spectroscopy (EIS) is an electrochemical technique that enables electrode surface characterization through changes in impedance across a given frequency range making it sensitive to interactions at the electrode surface and enabling the detection and quantification of analytes. While EIS has been traditionally limited to benchtop potentiostats, advancements in integrated circuits (ICs) have since enabled the miniaturization of potentiostats for at-home or field applications. However, implementation of EIS in a portable format is still limited by discontinuous measurements, high cost, or designs not fit for portability. This work revolves around the development of a miniaturized potentiostat that can implement EIS to better accommodate the need for miniaturized sensing platforms. My design uses the AD5941 IC which is a single-chip potentiostat analog-front-end enabling a small form-factor that fits in the palm of the user’s hand. The device was able to characterize a resistor-capacitor circuit with errors as low as 0.33% and quantify the concentration of a redox active compound with a 6.2% error, providing agreeable results with a commercial benchtop potentiostat and demonstrating our device’s potential for diagnostic applications. Our working frequency range of 200 kHz – 0.15 Hz, coupled with high system configurability and a cost of $50 makes our device an accessible option for at-home and portable applications. Future work to implement truly wireless functionalities, such as WiFi or Bluetooth Low Energy, along with experimental testing of biological substances will create a truly robust platform for portable diagnostic and sensing applications.</p>

Conducting vertical nanopillar arrays can serve as three-dimensional nanostructured electrodes with improved performance for electrical recording and electrochemical sensing in bio-electronics applications. However, vertical nanopillar-array electrodes made of inorganic conducting materials by conventional nanofabrication approach still faces challenges in high manufacturing costs, poor scalability, and limited choice of carrier substrates. Here, we report a new type of conducting nanopillar arrays composed of multi-walled carbon nanotubes (MWCNTs) doped polymeric nanocomposites, which are manufactured over the wafer-scale on both rigid and flexible substrates by direct nanoimprinting of perfluoropolyether nanowell-array templates into uncured MWCNT/polymer mixtures. By controlling the MWCNT ratios and the annealing temperatures during the fabrication process, MWCNT/polymer nanopillar arrays can possess outstanding electrical properties with high DC conductivity (~4 S/m) and low AC electrochemical impedance (~104 Ω at 1000 Hz). Moreover, by electrochemical impedance spectroscopy (EIS) measurements and equivalent circuit modeling-analysis, we can decompose the overall impedance of MWCNT/polymer nanopillar arrays in the electrolyte into multiple bulk and interfacial circuit components, and thus can illustrate their different dependence on the MWCNT ratios and the annealing temperatures. In particular, we find that a proper annealing process can significantly reduce the anomalous ion diffusion impedance and improve the impedance properties of MWCNT/polymer nanopillars in the electrolyte. / Master of Science / Conducting vertical nanopillar arrays can serve as three-dimensional nanostructured electrodes with improved performance for electrical recording and electrochemical sensing in nano-bioelectronics applications. However, vertical nanopillar-array electrodes made of inorganic conducting materials by conventional nanofabrication approach still faces challenges in high manufacturing costs, poor scalability, and limited choice of carrier substrates. Compared to conventional nanofabrication approaches, nanoimprint lithography exhibits unique advantages for low-cost scalable manufacturing of nanostructures on both rigid and flexible substrates. Very few studies, however, have been conducted to achieve the scalable nanoimprinting fabrication of conducting nanopillar arrays made of MWCNT/polymer nanocomposites. Here, I'm reporting a new type of conducting nanopillar arrays composed of multi-walled carbon nanotubes (MWCNTs) doped polymeric nanocomposites, which can be manufactured over the wafer-scale on both rigid and flexible substrates by direct nanoimprinting of the perfluoropolyether nanowell-array template into uncured MWCNT/polymer mixtures. We find that the nanoimprinted conducting nanopillar arrays can possess appealing electrical properties with a high DC conductivity (~4 S/m) and a low AC electrochemical impedance (~104 Ω at 1000 Hz) in the physiologically relevant electrolyte solutions (1X PBS). Furthermore, I've conducted a systematic equivalent circuit modeling analysis of measured EIS results to understand the effects of the MWCNT ratios and the annealing temperatures on the impedance of different bulk and interfacial circuit components for MWCNT/polymer nanopillar arrays in the electrolyte.