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This thesis consists of two completely separate parts: In part I some problems related to phonons in amorphous solids are considered, whilst Part II is devoted to the study of excitons in Cuprous Oxide (Cu₂O). Part I.- A theoretical model, suitable to treat vibrations in tetrahedrally coordinated amorphous systems is developed and permits the study of a number of situations of current interest. Three of these situations are studied in detail: 1) The local response of hydrogen in amorphous silicon when a single silicon is attached to one, two or three hydrogens. The differences between these three configurations are discussed and a direct connection with experimental results is suggested. 2) The interesting case of an amorphous alloy, where both, topological and substitutional disorder are present. This is treated within the spirit of the Coherent Potential Approximation. The particular alloy chosen (Si-Ge) is readily tractable because oithe similar bond characteristics of both components, which allows the neglect of force constant changes. 3) The Raman spectrum of AX₂, glasses. The model adopted permits the investigation of the local response at the defect sites for a number of defects. In order to explain the defect lines observed in the experiments, four plausible defect configurations are considered: a missing A-X bond, a X-A double bond, an A-A bond, and a square ring (two tetrahedra sharing an edge). A simple model to calculate the Raman response in amorphous solids is also outlined. Part II.- The valence band of Cu₂0 is studied in detail to account for the deviations from the hydrogenic law of the exciton spectrum. The appearance of the two series of excitons is explained in terms of a spin-orbit splitting of the valence band in the centre of the Brillouin Zone, using a Tight-Binding Approximation. The deviations of the lowest exciton levels from their expected values are seen to arise from an admixture of the two components of the split -off valence band due to direct Coulomb and exchange interactions. The Hamiltonian used corresponds to the so called "Spherical Approximation" and the results obtained are in remarkable agreement with the experiments.

The ability to model ground-state properties in density function theory (DFT) is a ected by the theoretical treatment of the electrons and the numerical approach to the theory. The electron-electron interaction energy is approximated by exchange- correlation (XC) functionals which are functions of the electron density. Popular functionals include the localized density approximation (LDA) or one of many gen- eralized gradient approximations (GGA). The numerical approaches used are the core-electron approximating pseudopotential (PsP) or the more accurate all-electron (AE) method. We test whether PsP calculations for some new GGA's can accurately reproduce AE values for cohesive energy, lattice constant, and bulk modulus for six- teen solids. We compare our PsP results to AE results for several XC functionals and gauge the quality of functionals by comparison to experiment. This allows us to determine which errors are caused by functionals and which are caused by PsP's.

Many industrial processes require contact between particles and a fluid or spray in order to effect drying, coating or granulation. One device capable of contacting fluid and particles efficiently is a spouted bed in which a jet of fluid is injected into solid particles. This forms an open channel or spout and induces material circulation in a downward moving annulus. For the continuous throughput of solids, knowledge is required of the mixing and particle motions within the bed. When processing mixtures of particles differing in size or density, the components are often found to segregate into regions rich in larger or denser particles. In a spouted bed this tendency could affect the mixing of solids and residence times of different size fractions with which the process performance is associated. Distributions of particle residence times were measured using a novel magnetic method of tagging. A thin coat of soft iron powder was applied to form tracer particles, a technique having potential for the investigation of mixing in many industrial processes. In this study, perfect mixing was observed for mono-size particle feeds and perfect self-mixing of each component in binary-size feeds. Generally, although not universally, the smaller particles in a mixture passed through the bed more quickly than larger particles. As the bed depth and gas flow rate were increased independently, the difference between the mean res- idence times of the components became greater and was also shown to be dependent on the position of the solids outlet. The difference in residence times is attributed to segregation within the bed. Different residence times for each component will arise if the particles segregate in the spout, the fountain, the free surface, the annulus or as they are drawn off from the outlet. From the studies on a 150 mm diameter bed, the key processes occur on the free surface and in the neighbourhood of the outlet. In larger diameter beds, segregation on the free surface is predicted to be of prime importance, especially when economy dictates the operation of the bed at low gas flow rates. The particles would then be deposited on the free surface near the spout and the cascading of solids towards the perimeter would lead to segregation.

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No description available.

Water treatment residual solids (WTRS) were characterized and studied as a potential phosphorus (P) adsorbent for application in sewage lagoons and stormwater runoff retention ponds. Three conventional WTRS sludge types (mixed Fe(OH)3-CaCO3, mixed Al(OH)3-CaCO3, and Al(OH)3) were collected from the Saskatoon, Prince Albert, and Buffalo Pound water treatment plants (WTP), respectively. The WTRS were collected in slurry form (i.e. not dried) from WTP clarifiers. Samples were collected during the summer and fall in an effort to observe seasonal effects. WTRS characterization involved determining selected chemical parameters which included pH, ammonium oxalate-extractable aluminum and iron content, and ammonium acetate-extractable calcium content. The pH of the WTRS samples ranged from approximately 6 to 8. Saskatoon WTRS samples had Feox content in the range of 55.2-55.8 g kg-1 of dry WTRS solid. Prince Albert WTRS samples had Alox in the range of 41.8-46.7 g kg-1 of dry WTRS solid. Buffalo Pound had Alox content in the range of 56.0-67.2 g kg-1 of dry WTRS solid. Saskatoon and Prince Albert WTRS samples had Ca content ranging between 34.3-38.1 g kg-1 of dry WTRS solid due to lime softening. Typically the fall WTRS samples had higher Al, Fe, and Ca content than the summer WTRS samples. Phosphorus adsorption behaviour and the maximum adsorption capacity of the WTRS were investigated through batch adsorption and settling experiments of WTRS in P-spiked deionized water. The Langmuir isotherm model best described the P adsorption behaviour of the WTRS (R2 = 0.97-1.00 linearized transformed data). The Freundlich isotherm model had not as good a fit with R2 ranging from 0.63 to 0.87 for the WTRS. The summer WTRS samples achieved maximum adsorption capacities (Qmax) in the following order: Buffalo Pound (78.1 mg P/g solid) > Prince Albert (70.4 mg P/g solid) > Saskatoon (7.37 mg P/g solid). The fall WTRS samples resulted in similar Qmax results in the following order: Buffalo Pound (82.0 mg P/g solid) > Prince Albert (70.4 mg P/g solid) > Saskatoon (6.41 mg P/g solid). Seasonal variations appeared to have minor impact on WTRS P adsorption. Phosphorus removal from sewage lagoons and stormwater runoff retention ponds was examined through batch adsorption and settling experiments of WTRS. Municipal primary wastewater effluent from the Saskatoon wastewater treatment plant (WWTP) was used as a surrogate for lagoon effluent during spring discharge. Stormwater runoff was collected from an agricultural runoff pond outside Saskatoon. Aluminum and iron based WTRS were effective at adsorbing phosphorus from municipal primary wastewater effluent in batch adsorption treatment. WTRS dosages removed P to within 6.4% of their target final P concentrations. However, the WTRS were not effective at adsorbing P from agricultural runoff water. After remixing the settled WTRS and doubling the dosage in the agricultural runoff water the WTRS only removed approximately 20-25% P. Re-suspension and resettling of WTRS after an initial cycle of P adsorption and settling had negligible effect upon the P concentration in the water column. The WTRS had a negligible effect on the pH of the wastewater solutions at the dosed concentrations. Short term (14 days) desorption of P from the WTRS utilized in P adsorption tests was low, typically less than 2% and reaching as high as 10.6% of the total P adsorbed. WTRS were found to be an effective P adsorbent from municipal primary wastewater effluent. The WTRS had high adsorption capacities compared to other WTRS and P adsorbents in the literature. The high adsorption capacities of the Al-based WTRS make them more practical than Fe-based WTRS for application.

Theoretical studies on the wetting of cylindrical solid surfaces with axisymmetric rugosities explicitly showed the presence of contact angle hysteresis, non-equilibrium jumps during contact line motion and the formation of composite surfaces. For physically rough surfaces with unidirectional randomness it was shown that hysteresis increases with decreasing roughness dimensions and with increasing standard deviation in the solid surface slope distribution. / The wetting of solid surfaces by liquids was investigated by a new tensiometric technique called capillarography. At large roughness wavelengths ((TURN)100 (mu)m) the contribution of concentric sawtooth-shaped regular roughness was found to be close to the values calculated theoretically. At smaller roughness wavelengths ((TURN)1 (mu)m) the wetting is complicated by intrinsic roughness and chemical heterogeneity. / High energy surfaces such as platinum and quartz exhibit a regular stick-jump behavior when wetted with water above a very low critical contact line velocity. This is caused by minute amounts of surface active impurities in the system. From the experimental data it can be deduced that surface active molecules diffuse onto and over the solid surface. / A relaxation of the contact angle was observed when an initially slow moving contact line was brought to a full stop. This is attributed to the slow establishment of a new equilibrium, possibly by surface capillary waves, involving metastable contact line positions separated by energy barriers. For receding contact angles, the main cause of the relaxation seems to be a stabilization of a liquid film left behind a receding contact line. / The observations made in this study contribute to a better understanding of the complicated nature of the wetting of solids.