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<p> The legacy of disposal practices for radioactive and other heavy metals has resulted in highly contaminated soils at the INL facility in Idaho Falls. Microbial effects on the mobility of a suite of metals (U, As, Cr, Co and Zn) within INL vadose sediments were assessed over a range of solution metal concentrations and biological activity through batch experiments. Sediment associated metals in the bulk sample as well as individual soil compartments increased as a function of total solution metal concentration. System specific trends in partitioning coefficients emerged, reflecting complex interrelations among biological activity, solution metal concentration and the specific metals involved. </p> <p> Results of this study clearly show that cyclic linkages between metal concentration and biological activity play a role in metal sediment biogeochemical behaviour. Differential impacts of biological activity on metal solid retention as a function of solution metal concentration were observed. This result may reflect feedback of metals on the microbial population such that the extent and/or nature of microbial activity is concentration dependent. Typically biological activity has a stronger effect with increased concentration, changing from a beneficial/neutral impact to an increasingly negative effect across the concentration range. The degree of this effect, and whether positive or negative on soil metal retention was however, element specific and dependent on the degree of biological activity. </p> <p> This is one of the first studies to evaluate the relative affinities of a suite of metals for the solid vs. solution phases over varying metal cocktail concentrations and levels of biological activity. My results indicate that differing affinities occur across this suite of metals, and that their relative affinities are non-linearly dependent on both the levels of metal and biological activity present. These results indicate that successful prediction of metal behaviour in complex natural systems, based on mono-metal laboratory experiments is likely limited. </p> / Thesis / Master of Science (MSc)

As one category of energetic materials, impact-initiated reactive materials are able to release a high amount of stored chemical energy under high strain rate impact loading, and are used extensively in civil and military applications. In general, polymers are introduced as binder materials to trap the reactive metal powders inside, and also act as an oxidizing agent for the metal ingredient. Since critical attention has been paid on the metal / metal reaction, only a few types of polymer / reactive metal interactions have been studied in the literature. With the higher requirement of materials resistant to different thermal and mechanical environments, the understanding and characterization of polymer / reactive metal interactions are in great demand. In this study, PTFE (Polytetrafluoroethylene) 7A / Ti (Titanium) composites were studied under high strain rates by utilizing the Taylor impact and SHPB tests. Taylor impact tests with different impact velocities, sample dimensions and sample configurations were conducted on the composite, equipped with a high-speed camera for tracking transient images during the sudden process. SHPB and Instron tests were carried out to obtain the stress vs. strain curves of the composite under a wide range of strain rates, the result of which were also utilized for fitting the constitutive relations of the composite based on the modified Johnson-Cook strength model. Thermal analyses by DTA tests under different flow rates accompanied with XRD identification were conducted to study the reaction mechanism between PTFE 7A and Ti when only heat was provided. Numerical simulations on Taylor impact tests and microstructural deformations were also performed to validate the constitutive model built for the composite system, and to investigate the possible reaction mechanism between two components. The results obtained from the high strain rate tests, thermal analyses and numerical simulations were combined to provide a systematic study on the reaction mechanism between PTFE and Ti in the composite systems, which will be instructive for future energetic studies on other polymer / reactive metal systems.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第22798号 / エネ博第412号 / 新制||エネ||79(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー応用科学専攻 / (主査)教授 平藤 哲司, 教授 土井 俊哉, 教授 馬渕 守 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

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The focus of this research is to explore the molecular-level interactions between reactive metal surfaces and aqueous environments by combined ultra-high vacuum/electrochemistry (UHV-EC) methodology. The objectives of this work are to understand (1) the effects of sulfate ions on the passivity of metal oxide/hydroxide surface layer, (2) the effects of sulfur-modification on the evolution of metal oxide/hydroxide surface layer, and (3) the effects of sulfur adsorbate on cation adsorption at metal surfaces.

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