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We report diffraction experiments on some representative Fast Ion Conductors. The structures of anhydrous stoichiometric deuterium (DAl₁₁O₁₇) and silver (AgAl ₁₁O₁₇) beta aluminas have each been determined at four temperatures in the range 4 . 2K - 773K using powder neutron diffraction (PND) data. In DAl₁₁O₁₇, a strong D-O(5) hydroxyl linkage is maintained at all four temperatures .For AgAl₁₁O₁₇ at 4.2K,we have observed, for the first time in metal beta aluminas, a completely ordered cation distribution. The material, which was prepared by a new route, is accurately stoichiometric. At 298K,the silver atoms have become somewhat delocalised and by 773K they are organised in a highly diffuse manner. Single crystal neutron diffraction was used to elucidate the proton distributions in ammonium beta alumina, (NH₄) _1.25Al₁₁- 0_17.125, and the two derivatives (NH₄) _0.78H_0.25Al₁₁0₁₇ and 'HA1₁₁- 0₁₇.In the parent compound, the positions and orientations of the two independant (NH⁺₄) species are such that all protons are involved in favourable hydrogen-bonding schemes. In formation of the first derivative, one of these sites becomes completely depopulated. Our results clarify the thermal behaviour of (NH₄) _1.25Al₁₁0_17.125 and we propose schemes by which stoichiometric beta aluminas are formed from this precursor and the related (H₃0)_1+x- Al₁₁0_17.+x/2. The crystal structures of I-Ag₃PO₄(25°C and 375°C) , II-Ag₃PO₄(650°C) ,II-Na₃PO₄ (γ) (400°C) and the solid solutions Na_3(1-x)Al_xPO₄are described. The high-temperature forms are considered in relation to the fluorite structure and mechanisms for the ionic conduction of these phases are proposed. A single crystal X-ray diffraction study of β-Ag₂SO₄ (25°C) reveals that it is isostructural with thenardite, V-Na ₂SO₄.The high-temperature modifications a-Ag₂SO₄ (490°C) and α-K₂SO₄ (620°C) have been characterised using PND data. A PND experiment on silver (I) fluoride confirms that it adopts the rocksalt structure and we find no firm evidence for a significant population of defects.

This study investigates the influence of ionic strength on the binding constant (KDOC) between benzo(h)quinoline (BHQ) and LHA by using fluorescence quenching method. Being a basic polycyclic aromatic hydrocarbon, BHQ is the dominated solute as the solution¡¦s pH value is higher than BHQ¡¦s pKb. In contrast, BHQ+ is the major species as the solution¡¦s pH value is lower than BHQ¡¦s pKb. In a salty neutral or basic LHA solution, the cation will bind with the acidic functional groups of LHA, then the conformation of LHA would be coiled up to be small in size. Due to that, leading to the decrease of the corresponding BHQ¡¦s KDOC. Furthermore, the charge density of cation is an important factor in control of the variation of BHQ¡¦s KDOC. The lower charge density of cation is, the less BHQ¡¦s KDOC varied. Besides, SO4 2- may suppress the binding affinity between Na+ and the acidic function groups of LHA, so that lower variation of BHQ¡¦s KDOC was observed than that of Cl- in a Na+ contained LHA solution. In an acidic solution, cation will also bind with the acidic functional groups of LHA, leading to the decrease of the binding sites of BHQ+ on LHA and the corresponding BHQ+¡¦s KDOC. Besides, Mg2+ could provide more binding sites for the acidic functional groups of LHA than Na+, so that the variation of BHQ+¡¦s KDOC with Mg2+ addition is higher than that with Na+ addition.

In this study, a novel polyimide (PI) film, consisting of multiwall carbon nanotubes (MWCNTs) dispersed in an Ionic Liquid (IL), were demonstrated to be high shielding effectiveness (SE). The film was potentially useful for screening electromagnetic interference(EMI) in an optical transceiver module. The experimental results showed MWCNT-PI composite dispersed well in IL exhibits a high far-field SE of 38 ~ 45 dB within the frequency range of 1 ~ 3 GHz. It was also demonstrated the MWCNT-PI composite prepared with IL dispersed process have higher SE and lower weight percentage of MWCNTs than those with non-IL-dispersed process. Their intermolecular forces were carefully examined in order to understand dispersion mechanisms among MWCNTs. The aggregation phenomenon of MWCNTs was known, resulting from van der Waals forces. In our study, IL was employed to disperse MWCNTs. A proposal reason was that the attractive force between cation of the IL and £k electrons of MWCNTs is greater than the van der Waals forces among MWCNTs. From conductivity measurement, percolation threshold of the IL-dispersed MWCNT-PI composite was 5.2 wt%; percolation threshold of the non-IL-dispersed MWCNT-PI composite was 11.5 wt%. Given the lower percolation threshold ,we demonstrated the successful dispersion of MWCNT by adding IL. From the results of Raman spectrometer analyses, the IL dispersion was proved to be a physical interaction. Furthermore, the IL-dispersed MWCNT-PI composite was used as package material in monopole antenna and got a near-field SE of 37dB within the frequency of 2.8 GHz. It implied that the IL-dispersed MWCNT-PI composite has an excellent EMI performance.The IL-dispersed MWCNT-PI composite is suitable for packaging low-cost and high-performance optical transceiver modules in the application of the fiber-to-the-home (FTTH) lightwave transmission systems.

There is growing need for technologies to displace traditional petroleum resources. Towards this goal, lignocellulosic biomass is seen as a potential renewable resource for the production of fuels and commodity chemicals. One of the most difficult components of lignocellulose to process is lignin, which is a complex, amorphous aromatic polymer that acts as one of the structural components in plants. Ionic liquids are a class of compounds that are composed completely of anions and cations that, in some cases, can completely dissolve lignocellulosic biomass. The research performed for this dissertation aims to advance the technologies of lignocellulose processing through effective depolymerization of lignin in ionic liquids. Lignin fragments from this depolymerization could be used as a feedstock for further processing into aromatic commodity chemicals or polymers. Additionally, by removing lignin, biomass becomes much more accessible to enzymatic or chemical saccharification as a step towards fermentation into ethanol or other fuels. Both base and acid catalyzed methods were explored, although the base promoted depolymerization of lignin in ionic liquids did not show much promise, as the reaction was never shown to be catalytic. Acidic routes towards lignin depolymerization were more successful. Using the acidic ionic liquid 1-H-3-methylimiazolium chloride, the ether linkages in lignin model compounds could be hydrolyzed with high yields. This technology was also applicable to the whole lignin macromolecule. The mechanisms of this reaction, as well as the effects on lignin were explored with various neutral and acidic ionic liquids, using HPLC, GPC, NMR, FT-IR, and mass spectrometry for analysis of samples. To demonstrate the applications of this technique, pine wood was treated with the acidic ionic liquids to open the structure of the wood to enzymatic saccharification through the removal of lignin and hemicellulose. / text

50Hz alternating electric fields have been used to enhance the mass transfer of ionic solutes within several food and model food materials under a range of conditions. Using image analysis it has been possible to visualise diffusion and determine concentration profiles within solid structures. It has been shown that in a uniform electric field diffusion can be enhanced by ca. 40% above that of normal diffusion, when an electric field strength of approximately 1500 Ym-l is applied. Modelling of the concentration profiles has demonstrated that the mechanism of enhanced mass transfer is dependent on the material in which the ion is diffusing as well as the process temperature and applied electric field strength. For alginate, a highly charged polymer structure, at low temperature (30°C) using a "Fickian" diffusion model fitted the experimental data well. At elevated temperature (100°C) the concentration profiles gave a poor fit to a "Fickian" diffusion model, however fitted well to a "Type II" diffusion model where the surface region of the material was flooded with dye. Within agar, a less highly charged material, diffusion can be fitted well using a Fickian diffusion model in all cases. Although diffusion is not truly Fickian as concentration dependence was seen. A number of effects were seen, the rate of diffusion into the solid material increased with decreasing molecular weight and increasing ionic charge of the dye molecules in solution (methylene blue, rhodamine 60 and fluorescein), however not to the extent predicted by a true electrophoretic model. Furthermore, enhanced diffusion increased by only 25% when the motion of the ions was along the electric field lines, as opposed to at 90°. The enhanced mass transfer effect has been demonstrated in a distorted electric field, local electric field strengths within the system have been calculated, and the diffusion coefficients obtained are in good agreement with diffusion coefficients in a constant electric field. Finally, enhanced mass transfer has been demonstrated in two species of fish, here changes in the diffusion coefficient demonstrate structural changes to the material.

published_or_final_version / Physics / Master / Master of Philosophy

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