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<p> Pure zinc and zinc/yttria stabilized zirconia (YSZ) composite coatings for combined wear and corrosion protection of ferrous substrates were prepared by electrodeposition using acidic zinc sulphate solutions containing YSZ and gelatin. The morphology of the electrodeposit was studied by Field Emission Scanning Electron Microscopy (FESEM) with energy dispersive spectroscopy (EDS). X-ray diffraction was employed to determine the texture of the zinc deposits. In the electrodeposition of pure zinc coatings, the influence of electrodeposition parameters, including current density, deposition time and solution pH was studied. It was found that the deposition rate was controlled by the current density and that an increase in deposition time resulted in the formation of deposit microstructures with coarse, columnar grains. The deposits prepared from solutions with lower pH were composed of uniform, fine grains and exhibited a basal plane preferred orientation.</p> <p> The effects of gelatin on zinc electrodeposition were investigated. It was found that the addition of gelatin profoundly modified the microstructure and crystallographic orientation of the zinc deposit. As the gelatin concentration increased, the mean grain size of zinc deposit was reduced and the basal plane preferred orientation was inhibited. The modification of the microstructure and orientation by gelatin increased microhardness of the zinc coating. However, the corrosion protection property which was assessed by potentiodynamic polarization test was not significantly changed.</p> <p> In the study on composite coatings, the incorporation of ceramic particles in the zinc deposit was characterized as a function of the deposition solution composition. The effect of ceramic particles on the hardness of the composite coatings was assessed by microhardness. The corrosion potential of the composite coating was determined by potentiodynamic polarization tests. The results showed that decrease in solution pH and addition of gelatin promoted the co-deposition of ceramic particles with zinc. The mechanical and corrosion properties of conventional zinc coatings were improved by the incorporation of ceramic particles.</p> / Thesis / Master of Applied Science (MASc)

This thesis extends our fundamental knowledge in the area of high oxidation state chemistry of xenon trioxide, XeO3. Oxygen coordination to the Xe(VI) atom of XeO3 was observed in its adducts with triphenylphosphine oxide, [(C6H5)3PO]2XeO3, dimethylsulfoxide, [(CH3)2SO]3(XeO3)2, pyridine-N-oxide, (C5H5NO)3(XeO3)2, and acetone, [(CH3)2CO]3XeO3. The crystalline adducts were characterized by low-temperature single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO3, which detonates when mechanically or thermally shocked, the solid [(C6H5)3PO]2XeO3, [(CH3)2SO]3(XeO3)2, and (C5H5NO)3(XeO3)2 adducts are insensitive to mechanical shock, but undergo deflagration when exposed to a flame. Both [(C6H5)3PO]2XeO3 and (C5H5NO)3(XeO3)2 are air-stable at room temperature. The xenon coordination sphere in [(C6H5)3PO]2XeO3 is a distorted square pyramid and provides the first example of a five-coordinate Xe center in a XeO3 adduct. The xenon coordination sphere of the remaining adducts are distorted octahedral comprised of three equivalent Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO3. Hirshfeld surfaces of XeO3 and (C6H5)3PO in [(C6H5)3PO]2XeO3 show the adduct is well-isolated in its crystal structure and provide a visual representation of the secondary Xe---O bonding in this adduct. Crown ethers have been known for over 50 years, but no example of a complex between a noble-gas compound and a crown ether or another polydentate ligand had been reported. Xenon trioxide is shown to react with 15-crown-5 to form the kinetically stable (CH2CH2O)5XeO3 adduct which, in marked contrast with solid XeO3, does not detonate when mechanically shocked. The crystal structure shows that the five oxygen atoms of the crown ether are coordinated to the xenon atom of XeO3. The gas-phase Wiberg bond valences and indices and empirical bond valences indicate the Xe---Ocrown bonds are predominantly electrostatic, σ-hole, bonds. Mappings of the electrostatic potential (EP) onto the Hirshfeld surfaces of XeO3 and 15-crown-5 in (CH2CH2O)5XeO3 and a detailed examination of the molecular electrostatic potential surface (MEPS) of XeO3 and (CH2CH2O)5 reveal regions of negative EP on the oxygen atoms of (CH2CH2O)5 and regions of high positive EP on the xenon atom that are also consistent with σ-hole bonding. Reactions of crown ethers with HF acidified aqueous solutions of XeO3 at room-temperature yielded adducts of 12-crown-4, (CH2CH2O)4XeO3, and 18-crown-6, [(CH2CH2O)6XeO3∙2H2O]2∙HF, whereas slow cooling of a solution of XeO3 with 18-crown-6 in acetone yielded (CH2CH2O)6XeO3∙2H2O. The adducts (CH2CH2O)4XeO3 and (CH2CH2O)6XeO3∙2H2O are shock-insensitive whereas the former adduct is air-stable at room temperature. The low-temperature, single-crystal X-ray structures show the Xe atom of XeO3 coordinated to the oxygen atoms of the crown ether ring. Uncharacteristic xenon coordination numbers exceeding six (including the three primary bonds of XeO3) were observed for all crown ether adducts. Raman spectroscopy frequency shifts are consistent with complex formation and provided evidence for the 2,2,1-cryptand adduct of XeO3. Gas-phase Wiberg bond valences and indices and empirical solid-state bond valences confirmed the electrostatic nature of the Xe---O bonding interactions. Comparisons between the XeO3 and SbF3 18-crown-6, 15-crown-5, and 12-crown-4 complexes are made. Incorporation of xenon trioxide, XeO3, into inorganic polyatomic salts under ambient conditions has been observed in several mixed xenate salts; K[XeO3XO3] (X = Cl, Br), K2[XeO3SeO4]∙HF, K[(XeO3)nZO3] (Z = I, N), and M2[(XeO3)nCO3]∙xH2O (M = Na, K, Rb, Ba). Raman spectroscopy was used to identify the aforementioned compounds and K[XeO3ClO3], K[XeO3BrO3], K2[XeO3SeO4]∙HF, and Rb2[(XeO3)2CO3]∙2H2O were also characterized by low-temperature, single-crystal X-ray diffraction. The xenon atom of XeO3 is seven coordinate in K[XeO3ClO3] and six coordinate in all other compounds with Xe---O distances that are significantly less than the sum of the Xe and O van der Waals radii. These salts provide examples of XeO3 coordinated to inorganic compounds and may provide insights into the inclusion of xenon oxides in minerals. / Thesis / Master of Science (MSc)

The objectives of this investigation are to develop a precise, non-destructive single crystal stress measurement technique, develop a model to explain the phenomenon known as 3power slump2, and investigate the role of device processing on wafer breakage. All three objectives were successfully met. The single crystal stress technique uses a least squares analysis of X-ray diffraction data to calculate the full stress tensor. In this way, precise non-destructive stress measurements can be made with known error bars. Rocking curve analysis, stress gradient corrections, and a data reliability technique were implemented to ensure that the stress data are correct. A theory was developed to explain 3power slump2, which is a rapid decrease in the amplifying properties of microwave amplifier circuits during operation. The model explains that for the particular geometry and bias configuration of the devices studied in this research, power slump is linearly related to shear stress at values of less than 90 MPa. The microscopic explanation of power slump is that radiation enhanced dislocation glide increases the kink concentration, thereby increasing the generation center concentration in the active region of the device. These generation centers increase the total gate current, leading to a decrease in the amplifying properties of the device. Passivation layer processing has been shown to both reduce the fracture strength and increase the residual stress in GaAs wafers, making them more susceptible to wafer breakage. Bare wafers are found to have higher fracture strength than passivated wafers. Bare wafers are also found to contain less residual stress than SiON passivated wafers, which, in turn, are found to have less stress than SiN passivated wafers. Topographic imaging suggests that SiN passivated wafers have larger flaws than SiON passivated wafers, and that the distribution of flaw size among SiN passivated wafers is wider than the distribution of flaws in SiON passivated wafers. These flaws are believed to lead to breakage of the device during processing, resulting in low fabrication yield. Both the power slump model and the wafer breakage data show that these phenomena are dependent on residual stress developed in the substrate during device fabrication. Reduction of process-induced residual stress should therefore simultaneously decrease wafer breakage rates and reduce power slump during device fabrication and operation. / Ph. D.

Magnetic nanoparticles are of considerable interest owing to their potential applications in biotechnology and the magnetic recording industry. Iron oxides have received much attention owing to their oxidative stability and biocompatibility; however, other transition metals and their alloys are also under investigation. Cobalt has one of the largest magnetic susceptibilities of these materials, but it readily oxidizes upon exposure to air resulting in antiferromagnetic oxide. Hence, coating cobalt nanoparticles with an oxygen-impermeable sheath would confer numerous benefits. Cobalt nanoparticles were prepared by the thermolysis of dicobalt octacarbonyl in two block copolymer micellar systems, wherein the copolymers were precursors to graphite or silica. Subsequent heat treatment of the samples at 600-700oC was conducted to condense the polymer coating around the cobalt nanoparticles and form oxygen impervious graphite or silica sheaths. Magnetic and structural characterization of these novel materials afforded pertinent information about their physical properties. Magnetic susceptometry indicated that the graphite coated cobalt nanoparticles resisted oxidation for over one year. The silica coated cobalt nanoparticles had high saturated specific magnetic moments, but the coatings were brittle and grinding the particles resulted in oxidation over time. Transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and energy-filtered TEM (EFTEM) were employed to study particle size and structural differences of the cobalt nanoparticles before and after heat treatment. The mean particle size and size distribution increased for the graphite coated cobalt particles, due to particle sintering at 700oC. In the silica coated cobalt nanoparticle system, the mean particle size increased when the sample was heat-treated at 600oC leading to a bimodal distribution. This bimodal distribution was explained by a fraction of the particles sintering, while others remained discrete. When the silica system was heat treated at 700oC, the particle size and size distribution remained similar to those of the pre-heat-treated sample, indicating that no sintering had taken place. The rapid pyrolysis of the polymer at 700oC may serve to lock the cobalt nanoparticles into a silica matrix, thus preventing them from coming into contact with one another and sintering. Several diffraction techniques (selected area electron diffraction (SAD), nano-beam electron diffraction (NBD) and x-ray diffraction (XRD)) were used to probe the crystal structure of graphite and silica coated cobalt nanoparticles, which was determined to be predominantly face-centered cubic. Anisotropic magnetic nanoparticles (nanorods) have an increased magnetophoretic mobility over spherical magnetic nanoparticles with the same equatorial radius. This property makes them attractive candidates for in vivo biological applications. Anisotropic mixed ferrite nanoparticles were coated with a biocompatible hydrophilic block copolymer to render them dispersible in aqueous media. Polymer coated mixed ferrite particles exhibited magnetic properties similar to that of pure magnetite, as the total level of other transition metals in the nanoparticulate system was less than 5%. Electron energy loss spectroscopy (EELS) and (EFTEM) confirmed that the dominant elements in the mixed ferrite nanoparticles were iron and oxygen. Furthermore, HRTEM, SAD and XRD analyses indicated that the crystal structure for the mixed ferrite nanoparticles was inverse spinel. X-ray diffraction peaks at low angles for the coated mixed ferrite rods corresponded to poly(ethylene oxide) peaks, suggesting that the block copolymer employed as a dispersant was associated with the particles. / Ph. D.

Ball milling has been shown to produce nanostructures in metal powders through severe repetitive deformation. Ball milling at cryogenic temperatures (cryomilling) is more effective in this capacity due to the low temperature by slowing recovery and minimizing diffusion distances between different components. Nanostructured metals are of interest because of their unique physical and mechanical properties. The result of cryomilling is powder consisting of crystallites on the order of 30 – 50 nm. In order to characterize the properties of this material, it is often necessary to consolidate the powder, which is often difficult without causing significant grain growth. In this work, aluminum-rich and magnesium-rich alloys of varying composition are produced by cryomilling and characterized by x-ray diffraction. A novel consolidation process called high shear powder consolidation (HSPC) is used to densify as-received and as-milled powders with minimal growth. The construction of a cryomill, along with a modification for improving process yield, has provided a platform for the study of nanocrystalline metals. It has been shown that bulk nanocrystalline materials are attainable and that alloy composition influences mechanical properties. / Master of Science

Roberto Sebastian Matta Echaurren, artista chileno surrealista, se conoce principalmente por su trabajo pictórico. Hoy, con la presente tesis se desea mostrar, explorar, investigar y deducir cómo este artista plástico principalmente pictórico, encuentra en el grabado un camino paralelo en el desarrollo de su obra, un camino bastante desconocido hasta este momento. La tesis que se presenta parte desde los inicios de su vida y relata el transcurso en ella. Ya que todos estos factores históricos y personales son los que nos ayudarán a conocer y comprender quién es Roberto Sebastian Matta Echaurren, un artista que nunca se consideró chileno, un artista universal y un pintor al que nunca se le consideró grabador, a pesar de la cantidad y calidad de su obra gráfica. Estas últimas ideas se expresan y se exponen en profundidad posteriormente dentro de la presente tesis. Luego, la investigación presenta una explicación del por qué es el título "Visiones e influencias de un grabador desconocido" para así poder vislumbrar cómo Matta entiende y vive el arte. Y lo más relevante cómo Matta descubre el grabado, dónde, cómo, cuándo, y por qué desea expresarse en esta área artística. Y se enuncia algo muy relevante que son los reconocidos ¿atelieres¿ de grabado en los que Matta eligió trabajar. Posteriormente se indican los dos atelieres más significativos donde trabajó Matta que son: Atelier George Visat - Albert Dupont y Atelier Fernand Mourlot ¿ Frank Bordas, haciendo un énfasis en la relación de Roberto Matta y Frank Bordas ya que es a partir de esta relación y los datos que nos entregaron las fuentes directas que podremos entender y comprender cómo Matta ve el grabado. Todo lo descrito son las bases que nos guiarán a un segmento esencial de esta tesis que es el capítulo titulado ¿Pintura y Grabado". Dentro de este capítulo veremos la pintura de Matta, su obra finalizada y su proceso dentro de ella. Con el resultado de toda esta información, hacemos un paralelo pictórico y gráfico, siendo lo fundamental establecer y esclarecer si existe o no una relación entre la pintura y el grabado de Roberto Matta. La catalogación de los grabados es el núcleo de la presente tesis, siendo el primer catálogo técnico de la obra de Matta, a pesar de que esta tesis se comenzó hace mas de 5 años, aún no existe un catálogo técnico y razonado completo de su obra. Hoy se presenta un catálogo más completo que los existentes aunque no se posee aún la totalidad de su obra. Posteriormente a la catalogación de sus grabados se presenta un análisis y comentarios para comprender la obra gráfica de este artista, en ella se eligen por grado de relevancia, a nivel histórico, personal o plástico seis obras gráficas, que son: The New School, Hom¿mere, El verbo hommerica, El gran Burundi-burunda ha muerto, Don Q y Ubu Roi. Para finalizar se ha considerado interesante presentar una cronología de la vida y obra de Roberto Matta que estarán unidas a los hechos históricos chilenos y mundiales para darnos un contexto político y social importante que se ve reflejado en las obras plásticas del artista. Deseo mencionar que las ¿Visiones e influencias de un grabador desconocido¿ no es una investigación completa ni acabada, ya que, la finalización de este trabajo fue truncado por una integrante relevante de la familia del artista, no obstante se logra presentar casi un 80% de su trabajo gráfico. Siendo esta tesis el destape hacia esa parte que el artista escondía y protegía como un secreto y de la cual actualmente solo conocemos fragmentos para su comercialización. Posteriormente a la primera revision de la presente tesis por los investigadores externos, se han realizado ciertos cambios, uno es sobre la presentacion del grafico familiar y de la presentacion de las fichas, todos los cambios son a nivel grafico de la presente tesis. Finalmente aquí esta!, se la presento hoy ¿Visiones e influencias para un grabador desconocido¿ un trabajo contra el miedo, contra el olvido, contra el secreto. / Moreno Campos, AG. (2014). Roberto Matta: Visiones e influencias de un grabador desconocido [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36739