Boron carbide-aromatic composites, formed by plasma-enhanced co-deposition of carboranes and aromatic precursors, present enhanced electron-hole separation as neutron detector. This is achieved by aromatic coordination to the carborane icosahedra and results in improved neutron detection efficiency. Photoemission (XPS) and FTIR suggest that chemical bonding between B atoms in icosahedra and aromatic contents with preservation of π system during plasma process. XPS, UPS, density functional theory (DFT) calculations, and variable angle spectroscopic ellipsometery (VASE) demonstrate that for orthocarborane/pyridine and orthocarborane/aniline films, states near the valence band maximum are aromatic in character, while states near the conduction band minimum include those of either carborane or aromatic character. Thus, excitation across the band gap results in electrons and holes on carboranes and aromatics, respectively. Further such aromatic-carborane interaction dramatically shrinks the indirect band gap from 3 eV (PECVD orthocarborane) to ~ 1.6 eV (PECVD orthocarborane/pyridine) to ~1.0 eV (PECVD orthocarborane/aniline), with little variation in such properties with aromatic/orthocarborane stoichiometry. The narrowed band gap indicate the potential for greatly enhanced charge generation relative to PECVD orthocarborane films, as confirmed by zero-bias neutron voltaic studies. The results indicate that the enhanced electron-hole separation and band gap narrowing observed for aromatic/orthocarborane films relative to PECVD orthocarborane, has significant potential for a range of applications, including neutron detection, photovoltaics, and photocatalysis. Acknowledgements: This work was supported by the Defense Threat Reduction Agency (Grant No.HDTRA1-14-1-0041). James Hilfiker is also gratefully acknowledged for stimulating discussions.

Advances in synthesis of boron-containing molecules significantly enlarged the usage of boron-containing subunits in medicinal chemistry. Interestingly, few recently approved drugs are boron analogues of natural amino acid derivatives. They contain an aminoboronic subunit. This subunit is also known to serve as a useful synthetic intermediate. However, despite its unique properties, limited examples of its synthesis are reported. In this work, a new method of obtaining aminoboronic acids derivatives is discussed. In Chapter 2 conditions towards obtaining β-aminoboronic acid derivatives via anti-Markovnikov Cope-type hydroamination are presented. Cope-type hydroamination with boron containing species have shown to proceed at lower temperatures compared to unsubstituted alkene derivatives. The products of Cope-type hydroamination reaction are new: to our knowledge similar oxazaborolidine heterocycles have not been reported. Despite reduced stability of the synthesised products and their proneness to conduct bora-Cope type elimination reaction, it was possible to demonstrate oxazaborolidine synthetic utility by various derivatization reactions. A scope with primary and secondary hydroxylamines is presented for a vinylboronate substrate. This work required access to a range of hydroxylamines. Recently our group discovered simple conditions to oxidize amines to hydroxylamines. In Chapter 3 an investigation of isolation conditions for a variant of this newly developed hydroxylamine synthesis is presented. While the oxidation is generally efficient in the presence of excess amine, the main challenge proved to be the propensity of the unreacted amine and hydroxylamine product to interact together. The efficiency and main limitations of different isolation strategies are presented. In general, the best results of removal of the excess amine via filtration were obtained using oxalic acid to form the corresponding amine salt. This filtration was followed by a short silica plug to further remove the amine salt causing contamination.

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The decomposition of Ammonium Perchlorate (AP), a strong oxidizer used in solid rocket propellant, is widely studied in an attempt to increase the burn characteristics of propellants. Many materials have been shown to catalyze its decomposition, but little is known about the mechanism by which AP decomposition becomes catalyzed. In this study, Boron Nitride (BN) nanostructures, a material previously unknown to act as a catalyst, is studied. The decomposition reaction is studied by thermo-gravimetric analysis / differential scanning calorimetry, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. The goal of this study is to discover the activation energy of this catalyst reaction, intermediary products of the reaction, mechanism of reaction and end state of the boron nitride nanostructures (ie, if the BN acts as a true catalyst, or participates on the overall reaction and has some end state that*s different from the initial state). Four variations of BN have been synthesized using a hydrothermal process; BN nanoribbons, Boron Rich BN, Nitrogen-Rich BN, and high surface area BN. It is shown that the decomposition of AP is significantly altered when in the presence of BN and the mechanism through which BN catalyzes the decomposition is most likely the presence of oxidized nitrogen species on the BN material.

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An investigation was undertaken to check the difference in isotopic content between two boron samples measured earlier in this laboratory by using different methods of sample preparation from those used in the previous investigation. Yields of preparation were measured throughout. Measurements using methyl borate and boron trifluoride indicated a difference of slightly over 2% in the isotopic content of the samples, whereas the difference found in the previous investigation was 3.5%. / Thesis / Master of Science (MS)

The chemistry, analysis, treatment, and occurrence of boron and chromium are of high interest since they are under consideration for revised MCLs in potable water. As a starting point to guide regulatory decision-making, a comprehensive review of boron in relation to potable water was undertaken. That work demonstrated that there were not proven cost-effective options for boron treatment. In preparation for a national survey of boron and chromium occurrence, it was discovered that existing analytical protocols sometimes '"missed" much of the total chromium that was present in water. It was determined that this was due to incomplete dissolution of particulates during routine Standard Method analysis of drinking water at pH 2.0. A more rigorous hydroxylamine digestion was developed and applied to circumvent this limitation. In relation to treatment, it was determined that sodium carbonate softening at pH 10.3 is a viable method of removing various inorganic contaminants including chromium from drinking water sources. The nationwide survey revealed that removals varied widely and were dependent on solution composition. Median removal of chromium was 92%. Linear and nonlinear empirical models were fit to crudely estimate the removal of various contaminants in the presence of other elements that are typically removed in the softening process (i.e. calcium, magnesium, silicon, iron, and aluminum). Boron was removed to a much lesser extent (median removal 2%) in this study, consistent with the general result of the literature review that enhanced treatments will be required for this contaminant. Modified precipitative softening was examined as a potentially attractive option to remove boron from natural waters. It was discovered that in some cases when magnesium and silicon were present, and if the pH was 10.8 ± 0.2, very high levels of boron removal (up to 90%) could be achieved versus 10% typically observed for conventional processes. This can be exploited to remove boron in waters naturally containing high levels of magnesium and silicon, or by adding supplemental amounts of either magnesium or silicon when one constituent is deficient. / Ph. D.

"June 2004." / Bibliography: leaves 135-159. / xi, 159 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Studies the mechanism underlying the morphological responses of boron- tolerance in plants by observing root and shoot responses to varied levels of subsoil boron in 2 barley varieties and 3 weed species common to agricultural areas of South Australia. Hypothesises that 4 mechanisms of boron-tolerance exist: 1. a physical barrier at xylem loading that also, 2., may include an efflux system; 3. enhanced sugar levels in shoot and root and 4, maintaining or increasing root biomass in the upper soil depths where the concentrations of boron are not toxic. / Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Soil and Land Systems, 2004

Boron deficiency or toxicity can reduce yield and quality of vegetables. Seven vegetable crops, varying from low to high boron requirements were grown in field plots at Corvallis in 1987. Leaf-B and yield components of green bean, cucumber, potato, carrot, tomato, broccoli and table beet were examined under conditions of fall or spring soil applied B at a 5 kg/ha rate on two soil types. Soil tests on control plots indicated B levels of .39 mg/kg and .20 mg/kg in the top 23 cm of soil in the silty clay loam and sandy loam soil, respectively. Fall or spring application of B increased soil B levels in the top 23 cm on the silty clay loam soil to .68 mg/kg and .37 mg/kg, and on the sandy loam soil to .81 mg/kg and .42 mg/kg, respectively. Boron application had no effect on yield or yield components except in green beans where spring applied B on the sandy loam reduced percent of premium grade pods (sieve sizes 1-4). Leaf-B levels were not affected in cucumber, carrot, or tomato on either soil. Boron application on both soils had a significant effect on leaf-B levels in bean, broccoli and table beet. Potato leaf-B was significantly affected only on the sandy loam soil. / Graduation date: 1993