Carbon nanotubes (CNTs) and graphite nanoplatelets (GNPs) are carrying great promise as two important constituents of future multifunctional materials. Originating from their minimal defect confined nanostructure, exceptional thermal and electrical properties have been reported for these two allotropic forms of carbon. However, a brief survey of the literature reveals the fact that the incorporation of these species into a polymer matrix enhances its effective properties usually not to the degree predicted by the composite\\textquoteright s upper bound rule. To exploit their full potential, a proper understanding of the physical laws characterizing their behavior is an essential step. With emphasis on the electrical and thermal properties, the following study is an attempt to provide more realistic physical and computational models for studying the transport properties of these nanomaterials. Originated from quantum confinement effects, electron tunneling is believed to be an important phenomenon in determining the electrical properties of nanocomposites comprising CNTs and GNPs. To assess its importance, in this dissertation this phenomenon is incorporated into simulations by utilizing tools from statistical physics. A qualitative parametric study was carried out to demonstrate its dominating importance. Furthermore, a model is adopted from the literature and extended to quantify the electrical conductivity of these nanocomposite. To establish its validity, the model predictions were compared with relevant published findings in the literature. The applicability of the proposed model is confirmed for both CNTs and GNPs. To predict the thermal properties, a statistical continuum based model, originally developed for two-phase composites, is adopted and extended to describe multiphase nanocomposites with high contrast between the transport properties of the constituents. The adopted model is a third order strong-contrast expansion which directly links the thermal properties of the composite to the thermal properties of its constituents by considering the microstructural effects. In this approach, a specimen of the composite is assumed to be confined into a reference medium with known properties subjected to a temperature field in the infinity to predict its effective thermal properties. It was noticed that such approach is highly sensitive to the properties of the reference medium. To overcome this shortcoming, a technique to properly select the reference medium properties was developed. For verification purpose the proposed model predictions were compared with the corresponding finite element calculations for nanocomposites comprising cylindrical and disk-shaped nanoparticles. To shed more light on some conflicting reports about the performance of the hybrid CNT/GNP/polymer nanocomposites, an experimental study was conducted to study a hybrid ternary system. CNT/polymer, GNP/polymer and CNT/GNP/polymer nanocomposite specimens were processed and tested to evaluate their thermal and electrical conductivities. It was observed that the hybrid CNT/GNP/polymer composites outperform polymer composites loaded solely with CNTs or GNPs. Finally, the experimental findings were utilized to serve as basis to validate the models developed in this dissertation. The experimental study was utilized to reduce the modeling uncertainties and the computational predictions of the proposed models were compared with the experimental measurements. Acceptable agreements between the model predictions and experimental data were observed and explained in light of the experimental observations. The work proposed herein will enable significant advancement in understanding the physical phenomena behind the enhanced electrical and thermal conductivities of polymer nanocomposites specifically CNT/GNP/polymer nanocomposites. The dissertation results offer means to tune-up the electrical and thermal properties of the polymer nanocomposite materials to further enhance their performance. / Ph. D.

An understanding of groundwater flow is essential in many aspects of mining. This is especially true for the sandstones of the Manitou Falls Formation, which overlie uranium deposits in the Athabasca Basin of northern Saskatchewan. Experience has shown that the hydraulic conductivities of these sandstones can be relatively high, especially in zones containing natural fractures, thus leading to potentially problematic groundwater inflow rates. This thesis presents the results of a study of hydraulic conductivity of the Manitou Falls Formation, in which detailed core logging and laboratory testing were undertaken for samples from two boreholes at the McArthur River mine site. Results from the logging and laboratory testing were interpreted in context provided by multiple packer tests conducted in these boreholes. Through core logging, indicators of conductive zones were identified. These indicators include fracture orientation (sub-vertical fractures were found to have more of an impact on conductivity than horizontal fractures), infilling, and staining. The laboratory testing program involved the measurement of hydraulic conductivities of fractured core samples across a span of effective confining pressures representative of in-situ conditions. Changes in fracture aperture were simultaneously recorded at each confining pressure level. It was found that theoretical relationships between aperture change and fracture conductivity represent the observed behavior of the samples reasonably well when fracture roughness is accounted for. The laboratory testing also confirmed the effects of fracture staining and infilling on hydraulic conductivity inferred from core logging and packer testing results. The results provide insights into the mechanisms underlying flow in fractured intervals of the Manitou Falls Formation, and provide guidance for selecting intervals to investigate during future packer testing in this formation.

The hydraulic conductivity of sand-bentonite mixtures (SBMs) was measured to investigate the effects of mixing method, uniformity, and hydration of the mixtures. Triaxial tests were completed to determine the hydraulic conductivity of each specimen. Specimens using Ottawa sand and Wyoming bentonite, prepared with dry and suspension mixing conditions that altered the degree of hydration and swelling of bentonite, had varying bentonite content by percentage dry weight of sand. The conclusions of this experiment can be applied to the construction of cut off walls used in levees to mitigate groundwater seepage through underlying pervious layers. Eleven sand-bentonite specimens were tested in this study: nine were prepared using dry mixing and two were prepared using suspension mixing. The results do not show strong correlations between hydraulic conductivity and bentonite content, mixing method, clay void ratio, or time. Therefore, further investigation of the results was necessary. The bentonite void ratio (clay void ratio) assumes that bentonite is fully swelled for both blocked and partially blocked flow. Blocked flow occurs when the swelled bentonite blocks all the sand voids, forcing the water to flow within the bentonite voids. However, the results in this study shows that the concept of clay void ratio doesn’t capture the performance of SBMs when the bentonite is partially swelled; therefore, a new concept of effective clay void ratio was introduced to account for bentonite partial swelling. The effective clay void ratio determines the volume of swelled clay as a function of the volume of fully swelled bentonite. This is useful when comparing results with literature or predicting hydraulic conductivity in cases where only partial swelling of bentonite is expected. / text

Monomers, polymers, charge-transfer complexes of 2-benzylidene-1,3-dithioles (Dithiafulvenes), and 1,3-dithiolium (Dithiafulvenium) salts of dithioesters and poly(dithioesters) were synthesized. The infrared, nuclear magnetic resonance (NMR) and ultra violet spectra of these materials were also reported. Condensation polymerization of piperidinium tetrathio terephthalate with α-halocarbonyl compounds using phase-transfer techniques yielded poly(dithioesters) that upon dehydrative cyclization with sulfuric acid gave poly(1,3-dithiafulvenium) salts. Polymerization of substituted dithiafulvenes with diacid chlorides, p-phenylene diisocyanate or terephthalaldehyde yielded polymers with inherent viscosities of 0.10 dL/g to 0.21 dL/g. The electric resistivity of the charge-transfer complexes of several dithiafulvenes and the electron donors TCNQ and TNF measured by the two-probe method was found to be >10⁶ Ω.cm at room temperature, hence behaving like insulators. Polyesters and polyesterimides of 4,4'-sulfonyl diphenol were synthesized. The low molecular weight polymers had viscosities of 0.12 to 0.20 dL/g. The polymers formed brittle films and their IR and NMR spectra were reported.

No description available.

No description available.

No description available.

No description available.

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.

If a physical dimension of a metallic specimen is comparable with, or smaller than, the mean free path of the conduction electrons, then the observed electrical conductivity will be less than that of a conventional bulk sample. This phenomenon is called a size effect, and is the result of electron scattering from the specimen surfaces. In the present investigation, measurements were made on electropolished monocrystalline specimens ranging from matchbox geometry to thick-film geometry in order to obtain further information on the size effect in bismuth at liquid helium temperatures.