SixGe1-x is a promising alloy semiconductor material that is gaining importance in the semiconductor industry primarily due to the fact that silicon and germanium form a binary isomorphous system and hence its properties can be adapted to suit the needs of a particular application. Liquid phase diffusion (LPD) is a solution growth technique which has been successfully used to grow single crystals of SixGe1-x. The first part of this thesis discusses the development of a fixed grid solver to simulate the LPD growth under zero gravity condition. Initial melting is modeled in order to compute the shape of the initial growth interface along with temperature and concentration distribution. This information is then used by the solidification solver which in turn predicts the onset of solidification, evolution of the growth interface, and temperature and concentration fields as the solidification proceeds. The results are compared with the previous numerical study conducted using the dynamic grid approach as well as with the earth based experimental results. The predicted results are found to be in good qualitative agreement although certain noticeable differences are also observed owing to the absence of convective effects in the fixed grid model. The second part investigates the effects of crucible translation on the LPD technique using the dynamic grid approach. The case of constant pulling is examined first and compared with the available experimental results. Then a dynamic pulling profile obtained as a part of simulation process is used to achieve the goal of nearly uniform composition crystal. The effect of crucible translation on the interface shape, growth rate, and on the transport process is investigated. Finally, the effect of magnetic field on the LPD growth is examined. / Graduate

Ag nanoparticle (NP) paste was fabricated and used to bond Cu wire to Cu foil at low temperatures down to 433 K. The relatively low bonding temperature promotes this method to be used in polymer-based flexible electronics, which cannot withstand high bonding temperatures due the possible melting of the polymer substrate. Unlike low-temperature soldering techniquies, bonds formed by this method was proved to withstand temperatures higher than the bonding temperature, which also promotes it to be used in electronics that operate at high temperatures. The Ag NP paste was developed by increasing the concentration of 50 nm Ag NP sol from 0.001 vol.% to 0.1 vol.% by centrifugation. The 0.001 vol.% Ag NP sol was fabricated in water by reducing silver nitrate (AgNO3) using sodium citrate dihydrate (Na3C6H5O7.2H2O). The bond was formed by solid state sintering among the individual Ag NPs and solid state bonding of these Ag NPs onto both Cu wire and foil. Metallurgical bonds between Ag NPs and Cu were confirmed by transmission electron microscopy (TEM). The Ag NPs were coated with an organic shell to prevent sintering at room temperature. It was found that the organic shell decomposed at 433 K, defining the lowest temperature at which a bond could be formed. Shear tests showed that the joint strength increased as the bonding temperature increased due to enhanced sintering of Ag NPs at higher temperatures. For better understanding of the melting and the sintering kinetics of Ag NPs, a molecular dynamics (MD) simulation based on the embedded atom method (EAM) was conducted to different sizes of Ag NPs with diameters between 4 nm and 20 nm. Programmed heating of an equal rate was applied to all sizes of NPs to find the complete melting and surface premelting points and sintering kinetics of the Ag NPs. The initial structural configuration of the Ag NPs was FCC truncated octahedral, which found to be stable for this size range of NPs. As a first step toward drawing a phase map of stable solid phases of Ag NPs at different temperatures and sizes of Ag NPs, the stability of the FCC truncated octahedral was studied for Ag NPs in size range of 1 nm to 4 nm. The smallest Ag NPs at which this configuration is stable was determined as 1.8 nm. Unlike the previous theoretical models, this MD model predicted both complete melting and surface premelting points for a wider size range of NPs. Melting kinetics showed three different trends that are, respectively, associated with NPs in the size ranges of 4 nm to 7 nm, 8 nm to 10 nm, and 12 nm to 20 nm. Ag NPs in the first range melted at a single temperature without passing through a surface premelting stage. Melting of the second range started by forming a quasi-liquid layer that expanded to the core, followed by the formation of a liquid layer of 1.8 nm thickness that also subsequently expanded to the core with increasing temperature, completing the melting process. For particles in the third range, the 1.8 nm liquid layer was formed once the thickness of the quasi-liquid layer reached 5 nm. The liquid layer expanded to the core and formed thicker stable liquid layers as the temperature increased toward the complete melting point. The ratio of the quasi-liquid layer thickness to the NP radius showed a linear relationship with temperature. Sintering kinetics of two Ag NPs in the size range of 4 nm to 20 nm, and sintering of three and four Ag NPs of 4 nm diameter was also studied by MD simulation. The sintering process passed through three main stages. The first was the neck formation followed by a rapid increase of the neck radius to particle radius ratio at 50 K for 20 nm particles and at 10 K for smaller NPs. The second was characterized by a gradual linear increase of the neck radius to particle radius ratio as the temperature of the sintered structure was increased to the surface premelting point. A twin boundary was formed during the second stage that relaxed the sintered structure and decreased the average potential energy (PE) of all atoms. The third stage of sintering was a rapid shrinkage during surface premelting of the sintered structure. Based on pore geometry, densification occurred during the first stage for three 4 nm particles and during the second stage for four 4 nm particles. Sintering rates obtained here were higher than those obtained by theoretical models generally used for predicting sintering rates of micro-particles.

Percutaneous delivery of drugs promises many advantages over oral or intravenous administration, such as a better control of blood levels, a reduced incidence of systemic toxicity, an absence of hepatic first-pass metabolism, better patient compliance, etc. However, the dermal drug transport is limited by the unsuitable physicochemical properties of most drugs and the efficient barrier function of the skin. Thus, numerous attempts have been reported to improve topical absorption of drugs, concentrating mainly on the barrier function of the stratum corneum by use of penetration enhancers and/or skin warming. An alternative and interesting possibility for improved dermal permeability is the synthesis of derivatives or analogues with the aim of changing the physicochemical properties in favour of skin permeation, efficacy and therapeutic value. Cyclizine (I) is an anti-emetic drug primarily indicated for the prophylaxis and treatment of nausea and vomiting associated with motion sickness, post operation and Meniere's disease. It acts both on the emetic trigger zone and by damping the labyrinthine sensitivity. Pharmacologically it has anti-histaminic, antiserotonergic, local anaesthetic and vagolytic actions. It is widely used and also suitable for children from six year of age. Percutaneous absorption of (I) can, among others, avoid the "first-pass" effect and the discomfort of injection. The main objective of this study was to explore the feasibility of percutaneous absorption of (I) and its alkyl analogues via physicochemical characterization and assessment of their permeation parameters. The intent was also to establish a correlation between the physicochemical properties of these compounds and their percutaneous rate of absorption. To achieve these objectives, the study was undertaken by synthesizing the alkyl analogues and determining the physicochemical parameters relevant to skin transport. Identification and level of purity for the prepared analogues were confirmed by mass spectrometry (MS), nuclear magnetic resonance (NMR) spectrometry and infrared (IR) spectrometry. Experimental aqueous solubility (25 °c & 32 °C) and partition coefficient for each compound were determined. In vitro permeation studies were performed at pH 7.4, using Franz diffusion cells with human epidermal membranes. Diffusion experiments were conducted over a period of 24 hours maintaining a constant temperature (37 DC) by means of water bath. All samples were analysed by high pressure liquid chromatography (HPLC). Cyclizine (I) has a methyl group at N-4. Increasing the alkyl chain length on N-4 of the piperazine ring resulted' in compounds with lower melting points and higher water solubility than (I). (II) exhibited 3-fold increase in water solubility, followed by (IV) with about 2.5 fold increase. The water solubility of (III) was almost the same as that of (I). Log partition coefficients increased linearly with increasing alkyl chain length. The analogues therefore, possessed more favourable physicochemical properties to be delivered percutaneously. Indeed, the in vitro skin permeation data proved that these analogues could be delivered more easily than (I) itself. The flux of (I) was 0.132 ug/cm2/h in a saturated aqueous solution. Compound (II) resulted in a 53-fold (6.952 ug/cm2/h) increase in permeation compared to (I). (III) and (IV) resulted in a 2- and 5fold enhancement of permeation respectively. Based on the results of the study, it seems that increased aqueous solubility and low level of crystallinity play a vital role in optimizing percutaneous absorption of (I) and its alkyl analogues. But the importance of the effect of increased lipophilicity cannot be ignored. The low percutaneous• absorption of (I) might be attributed to its low aqueous solubility and increased crystallinity, as is evident from the higher melting point than the analogues. From all the permeability data using aqueous solutions, it is clear that compound (II) is the best permeant of this series and in addition it is known that this compound antagonizes the effects of histamine. / Thesis (M.Sc. (Pharm.))--North-West University, Potchefstroom Campus, 2004.

Many of the physical properties of semiconductor materials depend on the presence of imperfections. A significant source of lattice imperfections is the inclusion of foreign atoms, or impurities; since most semiconductor devices require accurate and repeatable results, highly pure materials are desired. In order to obtain high purity semiconductor metals. zone purification is commonly utilized as the final purification stage. Due to the demand for increasing purity in an extremely competitive industry. producers must increase process efficiency and reduce production costs. The University of Victoria Crystal Growth Lab Group (CGL) is participating in a project aimed at increasing the efficiency of a commercial zone refining system. The project is composed of two parts: a numerical analysis intended to simulate the process. and an experimental study intended to verify the numerical model and conduct optimization experiments. A zone refiner was designed and developed in the lab for the experimental portion of the project. This thesis details the experimental portion of the project. The CGL zone refiner will be used to study the effects of zone geometry and mixing on the efficiency of the process. In order to achieve the most efficient possible combination. the zone refiner was constructed with the capability to adjust all of the typical process variables such as zone speed, zone spacing, and number of zone passes. as well as to accommodate specific methods aimed at increasing mixing in the melt such as applying an electric current or a rotating magnetic field. Once the CGL zone refiner system was complete, several experiments were carried out to prove and characterize the system. Samples were removed from the purified ingots and sent for glow discharge mass spectrometry (GDMS) analysis. The GDMS results indicated that the CGL zone refiner purified the ingot as desired and that there were no external sources of contamination from the process: in general, a reduction in concentration was seen for the impurities tested. During both the initial thermal testing and the subsequent full process experiments, the zone refiner performed as expected and without difficulty. The entire process was qualified and determined to be stable and easily controlled. The experiments conducted to date have shown that the system is a capable zone refiner for all of the planned studies.

Solid-state amorphization of a crystalline solid to an amorphous phase is extensively studied as a first order phase transition at low temperature for almost thirty years. In this dissertation, we report the recent progress on phenomenological models employed for thermodynamic description of macroscopic systems and fluctuations and nucleation of mesoscopic inhomogeneous systems in binary solid solutions under polymorphic constraints with no long-range diffusion involved. Based on our understanding on atomic picture of solid-state amorphization in binary solid solutions, we propose a Landau free energy to describe amorphization as the first order phase transition. The order parameter is defined which represents the loss of long-range translational order. The elastic strain field induced by composition disorder plays the important role through the bilinear coupling with the order parameter. Elastic softening and amorphization happen simultaneously. From the similarity between the melting and amorphization, we use the temperature and composition as two external variables and treat solid-state amorphization as low temperature melting under polymorphic constraints. For homogeneous system, the phase diagrams for endothermic melting and exothermic melting are built separately and the corresponding thermodynamic quantities are presented. A microscopic homogeneous nucleation mechanism is proposed conceptually in binary solid solutions under polymorphic constraints. The formation of an amorphous embryo is initiated from the composition modulation in the crystal state and a subsequent polymorphous nucleation within the as-formed heterophase fluctuation. This homogeneous nucleation path is thought to be associated with the nonlinear energy localization mechanism connected with the localized large-amplitude excitations of atoms, which are induced by nonlinear and disorder. A Landau-Ginzburg free energy is constructed to describe the critical nucleus and the growth of the new phase in one-dimensional systems. Analytical and numerical methods contribute to the understanding the fluctuations and nucleation processes. Size-dependent melting and amorphization in nanosolids are investigated. Two models are proposed for nanocrystalline solid solutions to glass transformations. Based on the thin film model with finite thickness, we build one-dimensional Landau-Ginzburg approach, which includes surface contribution and size dependence, and numerical results do show similarity with experimentsâ results qualitatively.

Western Mining Corporation produces nickel matte at the Kalgoorlie Nickel Smelter(KNS)from nickel sulphide concentrates within an integrated flash smelter.

Zugl.: Duisburg, Essen, Univ., Diss., 2009

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 114-121).

Made available in DSpace on 2014-10-09T12:42:37Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:19Z (GMT). No. of bitstreams: 0 / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:44:45Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:00Z (GMT). No. of bitstreams: 1 06997.pdf: 4582469 bytes, checksum: 7c5c05e2d6d13841e0e7d53eb604c3d2 (MD5) / Dissertacao (Mestrado Profissionalizante em Lasers em Odontologia) / IPEN/D-MPLO / Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP; Faculdade de Odontologia, Universidade de Sao Paulo