Dissertations / Theses on the topic 'Titanium compound'

Orientador: Edson Tomaz<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química<br>Made available in DSpace on 2018-08-26T01:40:52Z (GMT). No. of bitstreams: 1 Ponczek_Milena_M.pdf: 3719180 bytes, checksum: efe8192ba2f868976819b64f089b973c (MD5) Previous issue date: 2014<br>Resumo: Compostos orgânicos voláteis, ou COV, são uma importante classe de poluentes do ar comumente encontrados na atmosfera ao nível do solo, nos centros urbanos e industriais. O tratamento de COV provenientes de fontes industriais através da fotocatálise heterogênea é uma técnica eficiente para a degradação de baixas concentrações de uma grande gama de compostos orgânicos diferentes (hidrocarbonetos, aromáticos, alcóois, cetonas, etc) operando em condições ambientes. Um dos problemas que ainda impede sua aplicação industrial é a desativação do catalisador e por isso muitos grupos de pesquisa têm se dedicado ao estudo desta técnica na tentativa de melhorá-la e solucionar estes entraves. A atividade fotocatalítica do TiO2 pode ser melhorada pela adição de metais na sua superfície. Neste trabalho, preparou-se catalisadores de TiO2 por impregnação de Pt (1% m/m). A platina foi reduzida com NaBH4, fazendo-se posteriormente caracterização por DRX, XPS, UV ¿Vis, BET, Quimissorção de H2 e MEV/EDS para a validação do método de síntese. Todas as técnicas confirmaram que o método de redução com NaBH4 não modifica estruturalmente o TiO2, mantendo a sua cristalinidade e a razão de anatase/rutilo. A técnica de XPS indicou a presença de metal em estado de oxidação reduzido. Para o estudo da influência da impregnação de Pt no óxido titânio, foram realizados experimentos de fotocatálise em um reator recoberto com TiO2puro, e em um reator recoberto com TiO2/Pt variando-se a concentração de entrada (de 50 à 500 ppmv) ou o tempo de residência (de 10 à 50 s) para os COV n-octano, iso-octano, n-hexano e ciclohexano. Utilizou-se reatores tubulares com volume interno de 1160 ml com os catalisadores, dióxido de titânio puro ou modificado, imobilizados na parede interna dos reatores. A fonte de radiação UV foi uma lâmpada do tipo germicida de 100W de potência, caracterizada por comprimentos de onda de 254 nm (banda de emissão UV-C). As concentrações na entrada e na saída do reator foram analisadas através de um monitor contínuo de hidrocarbonetos do tipo FID. A adição de platina ao TiO2 gera uma melhoria na eficiência fotocatalítica nas reações de oxidação de COV; a conversão dos COV utilizando o catalisador impregnado com platina atingiu 99 % de conversão, enquanto que TiO2 puro atingiu, no máximo 93%<br>Abstract: Volatile organic compounds, or VOC, are an important class of air pollutants commonly found in the atmosphere at ground level in urban and industrial centers. The treatment of VOC from industrial sources by oxidative photodegradation is presented as a good alternative. These systems are promising as pollution control technology, since they can decompose low concentrations of VOC efficiently and in ambient conditions. The recombination of electrons and holes formed on the surface of TiO2 is a factor that limits the photocatalytic efficiency. For this reason, many efforts have been made to maximize the separation of charges, in order to improve the photocatalytic efficiency. A proposed alternative is to add noble metals to TiO2 structure. This work aims to study the degradation of volatile organic compounds by heterogeneous photocatalytic oxidation using ultraviolet light, bare TiO2 and TiO2 impregnated with 1% w/w platinum as catalysts. TiO2 catalysts were prepared by impregnating Pt on TiO2 structure by reduction method with NaBH4. The photocatalysts were characterized using analytical techniques like XRD, XPS, UV-Vis Diffuse Reflectance, BET, H2 Chemisorption and SEM/EDS to validate the method of synthesis. All analysis confirmed that the reduction method with NaBH4 do not structurally modify TiO2, keeping its crystallinity and the ratio of anatase/rutile. XPS indicates the presence of metal in reduced oxidation state. To study the influence of the impregnation of platinum on titania, after synthesis and characterization, the study of gas-solid heterogeneous photocatalytic oxidation of some VOC was carried out at room temperature with annular plug flow reactors (1160 ml), one coated with pure TiO2 and another coated with TiO2/Pt, the catalysts were immobilized on reactor¿s internal walls. The photocatalystic tests were performed for n-octane , iso-octane, n-hexane and ciclohexane varying the inlet concentration (from 50 to 500 ppm) or residence time (from 10 to 50 s). The light source was an UV lamp (100 W, wavelengths with a maximum intensity at 254 nm. Reactants and products concentrations were analyzed using a continuous monitoring with a total hydrocarbon analyzer with flame ionization detector (FID). The addition of platinum to TiO2 improves photocatalytic efficiency of oxidation of VOC; conversion of the VOC using impregnated catalyst reached 99%, whereas pure TiO2 was at most 93%. No título do trabalho, a fórmula TiO2 deve vir com o "2" em subscrito, pois trata-se da fómula química da substância<br>Mestrado<br>Processos em Tecnologia Química<br>Mestra em Engenharia Química

<p>An electrolytic cell was designed and constructed for the preparation of TiO2 nanotubes. Conditions of anodic oxidation were established to reproducibly prepare TiO2 nanotubes of average length 35-50 &mu<br>m vertically orientated relative to the plain of a pure titanium metal sheet. A non-aqueous solution of ethylene glycol containing small percentage of ammonium fluoride was used as the electrolyte with an applied voltage of 60 V. The morphology and dimensions of the nanotube arrays were studied by scanning (SEM) and transmission (TEM) electron microscopy. The effect of calcination under different conditions of temperature and atmosphere (nitrogen, argon and air) were assessed by both X-ray diffraction (XRD) and cyclic voltammetry (CV). Cyclic voltammetry studies were made possible by construction of a specially designed titanium electrode upon which the nanotubes were prepared. CV studies established a positive correlation between crystallinity and conductivity of the nanotubes. Doping of the nanotubes with nitrogen and carbon was established by elemental analysis, X-ray photoelectron spectroscopy (XPS) and Rutherford back scattering (RBS). The effect of nonmetal doping on the band gap of the TiO2 nanotubes was investigated by diffuse reflectance spectroscopy (DRS).</p>

This Thesis describes the synthesis and characterisation of titanium imido compounds supported by pendant arm functionalised amidinate ligands. Reactivity studies of cyclopentadienyl amidinate-imido compounds with CO2 are presented. Chapter 1 introduces transition metal imido chemistry, with a particular emphasis on imido complexes of titanium. Chapter 2 describes recent developments in the chemistry of functionalised amidinate ligands. The synthesis and characterisation of new titanium imido compounds with pendant amine functionalised amidinate ligands is described. The preparation of an amidinate ligand with a pendant propyl arm is reported. Reactions of a selection of these complexes with small molecules are presented. Chapter 3 reviews recent developments in the chemistry of cyclopentadienyl amidinate-imido compounds. The preparation of cyclopentadienyl-supported titanium imido compounds bearing pendant arm amidinate ligands is described andthereactionsofthesecompoundswithCC>2arediscussed. Kineticanddensity functional theory studies of these reactions are presented. Chapter 4 describes the synthesis and characterisation of alkyl and aryloxide titanium amidinate-imido compounds. The preparation of cationic derivatives is also described and reactions of these cationic derivatives with small molecules are discussed. Chapter 5 presents full experimental procedures for all of the syntheses and reactivity studies outlined in Chapters 2 to 4. Chapter 6 contains characterising data for all of the new compounds reported. Appendices A - K contain tables of selected crystallographic data for all new crystallographically characterised complexes described in this Thesis. Appendices L - O contain kinetics data relating to work discussed in Chapter 3.

Sytnhese de natinbo5 qui par intercalation donne une serie de composes h2-2xax(tinbo5)::(2). Nh::(2)o et des composes (h::(3)nc::(n)h::(2n)nh::(3))::(0,5)tanbo::(5). On synthetise l'oxyde h::(3)ti::(5)nbo::(14). H::(2)o. Structure et proprietes magnetiques

Introduction Titanium-45, a candidate PET isotope, is under-employed largely because of the challenging aqueous chemistry of Ti(IV). The propensity for hydrolysis of Ti(IV) compounds makes radio-labeling difficult and excludes 45Ti from use in bio-conjugate chemistry. This is unfortunate because the physical characteristics are extremely desirable: 45Ti has a 3 hour half-life, a positron branching ratio of 85 %, a low Eβmax of 1.04 MeV, and negligible secondary gamma emission. In terms of isotope production, 45Ti is transmuted from naturally mono-isotopic 45Sc by low energy proton irradiation. The high cross-section and production rates on an unenriched metal foil target contribute to make 45Ti an ideal PET radionuclide. In order to bring 45Ti to even a preclinical plat-form, the hydrolytic instability of aqueous Ti(IV) needs to be addressed. Recently, the groups of Edit Tshuva (Hebrew University of Jerusalem) and Thomas Huhn (University of Konstanz) have synthesized several stable Ti(IV) compounds based upon the salan ligand [1,2]. Additionally, these compounds have shown heightened cyto-toxicity against HT-29 (human colorectal cancer) cells, amongst others, as compared to traditional metal-based chemotherapeutics such as cisplatin. The aim of our work has been to produce the radioactive analogue of one of these Ti(IV)-salan compounds, Ti-salan-dipic [2], which has hydro-lytic stability on the order of weeks. Not only will this allow us to shed some light on the still un-known mechanism of antiproliferative action of titanium-based chemotherapeutics, but it will also make progress toward bioconjugate 45Ti PET tracers. In the current abstract, we present some of the methods we are using to separate 45Ti from irradiated Sc, and subsequent labeling conditions. Material and Methods 45Ti was produced by proton irradiation of 250μm scandium foils at currents ranging from 10-20μA on a GE PETTrace. In order to increase production rate in the thin foil, an 800μm aluminum degrader was used to take the proton energy down from the nominal 16 MeV. The scandium was cooled by contact to a water-cooled silver plate. The activated foil was dissolved in 4M HCl, dried under argon at 120 oC, and taken back up in 12M HCl. Here, four (i-iv below) different approaches to removing the Ti from the Sc and labeling were taken with varying success. Briefly: i. 45Ti was separated on hydroxamate resin, as presented by K. Gagnon [3], only at 12M acid concentration followed by on-column radiolabeling. ii. 45Ti was extracted into 1-octanol [4], stripped with 12M HCl, and used directly for labeling from the organic phase. iii. 45Ti was trapped on a C-18 cartridge that had been pre-loaded with 1-octanol, similar to ion-pairing, and eluted with isopropanol. iv. 45Ti was extracted onto a polystyrene based 1,3 diol resin (RAPP polymers) and labeling commenced on the column. Radiolabeling was slightly different in each condition, but in general the salan and dipic ligands were added to the 45Ti in pyridine and reacted at elevated temperature (60–100 oC) for several (10–30) minutes. Reaction progression and radiochemical purity were assessed with silica TLC in chloroform : ethyl acetate (1 : 1). Results and Conclusion The trap, release, and yields for the four methods listed above are shown in TABLE 1. The best result was with the 1,3 diol resin which had the added advantage of reacting on-column. Further optimization is underway including a test of a solid supported 1,2 diol, and preclinical imaging with HT-29 xenografts. We conclude that hydrolytically stable 45Ti com-pounds can be synthesized in high yield, and hope that this advances the radiochemistry and use of 45Ti toward more widespread applications.

La síntesis y el estudio de complejos polinucleares de metales de transición constituyen un área de gran interés en la Química Inorgánica. La presencia de varios centros metálicos en una misma molécula puede modificar la reactividad que cabría esperar en compuestos metálicos. Por otra parte, estos sistemas polinucleares sirven como modelos a escala molecular para el estudio de ciertos procesos catalíticos como los que tienen lugar sobre superficies metálicas u óxidos metálicos.<br/><br/>El estudio teórico de dos familias de compuestos metálicos bien diferenciadas constituye el núcleo de esta tesis. En ambos casos el objetivo principal es ayudar a racionalizar las características químicas de las especies analizadas. El tratamiento se basará en cálculos teóricos mediante la teoría del funcional de la densidad, que han demostrado ser apropiados a la hora de estudiar agregados metálicos.<br/> <br/>Una primera parte, consta del estudio de la nueva familia de compuestos cubánicos de titanio que han sido recientemente sintetizados por el grupo del profesor Mena de la universidad de Alcalá de Henares. Un estudio teórico de dichos compuestos en colaboración conjunta con el trabajo en el laboratorio se ha venido realizando. Fruto de esta colaboración, nuevas pautas de investigación se han tratado de proponer por ambas partes. Como ejemplo, el análisis teórico para la obtención de espectros de resonancia magnética nuclear por métodos ab initio, que se expone en el segundo capitulo de la tesis, es fruto de un esfuerzo por parte de nuestro grupo por entender y racionalizar los datos de RMN obtenidos en el laboratorio para la caracterización de los compuestos. Además, fruto de los excelentes resultados obtenidos en este estudio, los conocimientos han sido aplicados a otros campos de interés dentro del grupo. Un estudio de la viabilidad para el análisis teórico del espectro de los núcleos de 183W en compuestos de Keggin forma un apartado importante en esta memoria.<br/><br/>Fruto de una estancia de seis meses en el grupo del doctor McGrady de la universidad de York surge un segundo apartado basado en el estudio de las importantes capacidades catalizadoras de los compuestos binucleares de molibdeno con azufres puente. La gran importancia industrial de procesos de hidrogenación catalizados por este tipo de compuestos ha despertado un gran interés, no obstante algunos aspectos del mecanismo de estas reacciones permanecen sin aclarar. El estudio teórico de esta reacciones puede proporcionar un poco de luz a estos aspectos. <br/><br/>Dentro del estudio de los compuestos cubánicos de titanio, los resultados principales se refieren a los asuntos siguientes:<br/><br/>- Descripción de las características estructurales y electrónicas de las especies implicadas. La disposición de los ligandos tridentados, (precubanos) de fórmula general [{TiCp*(&#61549;-O)}3(&#61549;3-CR)] y [{TiCp*}(&#61549;-NH)}3(&#61549;3-N)], para actuar como ligandos macrocíclicos donores de seis-electrones proporciona una ruta eficaz para la obtención de estructuras cúbicas con esqueleto [MTi3(&#61549;3-Y)(&#61549;-X)3]. <br/><br/><br/> <br/>Reacción del ligando con el fragmento metálico <br/><br/><br/>Es de esperar que fragmentos de casi todos los grupos metálicos sean capaces de interactuar con estos ligandos. Así se ha estudiado la formación de estructuras cubánicas a partir de fragmentos metálicos de los grupos 1,2, 4-6, 9, 13 y 14. Cambios en la naturaleza de la interacción, en el comportamiento del ligando, estructura molecular han sido analizados. Los resultados muestran las versatilidad de estos ligandos para actuar no sólo como donores de electrones si no también como posibles aceptores a través de los orbitales vacíos de los metales. Una mención especial en este apartado es necesaria para los isomeros acetilénicos y vilidénicos encontrados a partir de la deprotonación del compuesto [{TiCp*(&#61549;-O)}3(&#61549;3-CMe)] por la interacción con fragmentos metálicos del grupo 2. En este caso, el núcleo formado por los átomos de titanio sirve como base para la estabilización de estas especies.<br/><br/>- Estudio de la estabilidad de los compuestos y de los procesos energéticos en que están implicados (energías de la reacción, procesos de la isomerización). Un estudio de las condiciones experimentales que conducen a la obtención de estructuras cúbicas será analizado. El desplazamiento de ligandos lábiles en fragmentos metálicos por parte de los ligandos tridentados para formar los correspondientes cubanos ha sido probado, o también la activación de los enlaces nitrógeno-protón del ligando por interacción con el fragmento metálico. Estos procesos vienen caracterizados por unas condiciones energéticas favorables, estas condiciones son analizadas y estudiadas por su utilidad a la hora de proponer nuevas vías de síntesis en el laboratorio. Además, algunos compuestos presentarán evidencias del tener más que un isómero, o de experimentar un comportamiento dinámico en solución. Estas situaciones también se han descrito. Como resultado ha sido descrito el comportamiento de estas estructuras como ligandos mono- di- y tridentados, y adicionalmente como ligandos neutros o aniónicos. A su vez, respecto de la interacción con el fragmento metálico, un comportamiento como ligandos simples, que solo estabilizan el metal, o dobles, estabilizando metal y su respectivo contraión, han sido descritos.<br/><br/>- La influencia del solvente también se ha evaluado debido a la importancia que tiene su presencia en la obtención o no de ciertos compuestos. La termoquímica relacionada con la presencia del disolvente ha sido analizada desde el punto de vista teórico, debido a la imposibilidad de explicar ciertos procesos a partir de estudios en fase gas. Un modelo basado en un medio continuo de constante dieléctrica conocida se utiliza para demostrar los efectos del solvente. Para una misma familia de compuestos, solamente en algunos casos la interacción con los ligandos precubánicos conducen a la formación de los correspondientes cubanos, o en condiciones muy específicas. Por ejemplo, ha sido estudiado que los efectos del solvente son un factor decisivo en la obtención de los cubanos a partir de las sales de metales alcalinos y alcalino térreos. Este efecto permite explicar como la energía de red de las sales es fuertemente debilitada por la presencia del solvente, como factor principal en la obtención de las especies, por encima de la energía de interacción con el ligando.<br/><br/> - Descripción de algunas características químicas importantes. La contribución de los espectros de resonancia magnética nuclear resulta decisiva para la caracterización de los compuestos. Una descripción en detalle de las particularidades en el cálculo de los desplazamientos químicos para espectros de RMN es revisado en un apartado puramente teórico, especialmente para los métodos DFT. La activación del enlace C-H del carbono apical en el ligando [{TiCp*(&#61549;-O)}3(&#61549;3-CH)] durante la formación de estructuras diméricas fue seguida mediante espectroscopia RMN de 13C. Los grandes cambios experimentados en los desplazamientos químicos entre las especies protonadas y no protonadas han sido descritos y racionalizados perfectamente mediante cálculos teóricos. Los resultados obtenidos corroboran las suposiciones experimentales y proporcionan una visión muy clara de los procesos electrónicos que conducen a estos resultados. El carácter predictivo de estos estudios para con otras especies es claro, no obstante cuantitativamente hablando se encuentran dificultades a la hora de atribuir todos los desplazamientos.<br/><br/>Fruto de los excelentes resultados obtenidos en la descripción de los valores de RMN para los compuestos cubánicos, estos estudios se han ampliado a otros campos de interés para nuestro grupo de trabajo. Una sección, en parte diferente a la estructura global de la tesis, se ha dedicado ha mostrar estos primeros pasos a la hora de examinar las capacidades de los métodos DFT para computar los desplazamientos en núcleos de 183W en compuestos de Keggin. Nos encontramos ante unas mayores dificultades a la hora de reproducir los espectros experimentales, y gran parte de nuestros esfuerzos se han centrado en tratar de buscar la forma de trabajo más adecuada en términos de precisión y de coste computacional. La investigación y el interés continúan abiertos en un campo que necesita nuevas revisiones, sobre todo a la hora de racionalizar las posibles fuentes de error.<br/><br/>Las importantes características catalíticas de los sulfuros de molibdeno son objeto de estudio en la segunda parte de la tesis. El estudio teórico intentará aclarar ciertos aspectos confusos en la mecanistica asociada con las reacciones de estos compuestos. Estos complejos dinucleares de molibdeno con ligandos puente de azufre son una de las familias que posee una gran flexibilidad estructural y electrónica. Parte de los posibles isómeros del compuesto tipo [(CpMo)-S2]2 han sido estudiados, prestando gran interés al intercambio electrónico metal ligando con el cambio de estructura. <br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/><br/>Ejemplos de estructuras cerradas (a-b) y abiertas (c-d) para el complejo <br/><br/><br/>La capacidad de los complejos del sulfuro de activar el hidrógeno molecular y de catalizar la reducción del substrato por el hidrógeno es particularmente relevante en la química. En especial los procesos relacionados con la activación de hidrógeno y posterior reducción de un sustrato ligado a los azufre puente son analizados; y en particular aquellos relacionados con la estructura electrónica del catalizador y del substrato. En estos estudios se pone de manifiesto la importancia catalizadora del metal, sirviendo como puente para protones en la reducción. A su vez se muestra como la naturaleza del sustrato resulta decisiva a la hora de observar una eliminación de hidrógeno molecular o una obtención del substrato reducido.<br/><br/><br/>Tarragona, 2004 J. Gracia<br>The overall framework of this report aims to summarize the work we have done over the past four years. Conceptually, this thesis is divided into three parts. The nucleus is based on a joint project with prof. Mena, of the University of Alcalá, whose group is involved in the synthesis and characterization of new aza- and oxo- titanium cubanes. These families of compounds are basically obtained from preorganized titanium tridentate ligands which can incorporate almost all the metals of the periodic table and yield the corresponding heterometallic cubanes. In this respect, the theoretical study is based on and adapted from the progress in the laboratory work. Practically every section in this part starts by describing the experimental data available for the specific system studied when we began the analysis. Then we go on to describe the theoretical study and attempt to involve the reader in the problems discussed. As a consequence of the advance in the experimental work, NMR spectra are used to characterize the new compounds. This leads us to initiate studies in the computational simulation of NMR chemical shifts. The most theoretical part of this report is an assimilation of these studies. The excellent results obtained for the cubane compounds enabled us to extend the knowledge acquired to other interesting fields and our group has started a study of the NMR shielding tensors in polyoxometalate compounds. The third part of the thesis focuses on some molybdenum-sulphide clusters and their activity as catalysts.<br/><br/>Chapters 3 and 4 focuse on the electronic structure of the new titanium cubane compounds recently synthesized by Mena et al. We work parallel to an experimental group to compare and contrast the theoretical and experimental data, and so establish the base chemistry of these new compounds. In this sense, the various reaction energies were studied, and the compounds and their possible isomers were characterised by means of DFT methods. Particular emphasis is paid to the properties of incomplete Ti3 core cubane tridentate ligands (precubanes) as bases for obtaining cubanes. The electronic structure, bonding energies, electron transfer processes and reactivity in the titanium Ti3 core of the metal clusters are studied.<br/><br/>The reaction of the azatitanium compound with some titanium derivatives leads to nitrocubane formation (see Scheme 1.3). This reaction forms a cubane compound by adding the fourth vertex to a structure that becomes a precubane. <br/><br/> <br/>Scheme 1.3. Reaction of with <br/><br/><br/>Chapter 5 summarizes the work carried out during a six-month stay in Dr. John E. McGrady's group, which uses density functional theory to explore problems of structure, bonding and reactivity in inorganic compounds. The main focus of the research is metal-metal bonding in cluster compounds. Transition metals have a prominent position in catalysis, both in industrial and biological contexts, and the ultimate goal is to understand the part played by the metal and its ligand environment in facilitating a particular chemical transformation. Chapter 5 studies the electronic structure of the core catalysts and the mechanism of their, unresolved, catalytic activity. The various possible isomers with the generic formula were studied, and the energy of the electron transfer between the metallic centres and the sulphide ligands, so important in the catalytic process, was investigated in depth. Subsequently, the mechanism of the hydrogen activation reaction promoted by these bi-molybdenum compounds (Equation 1.1) was studied, and the nature of the different reaction pathways was elucidated.<br/><br/><br/>[(CpMo(&#61549;-S))2(S2CH2)] promotes the hydrogenation of alkynes to cis alkenes, allenes to alkenes, and ketenes to aldehydes and the hydrogenolysis of carbon disulphide to hydrogen sulphide and thioformaldehide. The mechanisms of hydrogen interaction with these complexes have not been established. It is apparent that the sulphide ligands play a role in hydrogen coordination, and this ligand reactivity was a dominant characteristic throughout the study of these dinuclear molybdenum systems.<br/><br/><br/> <br/>Equation 1.1

Semiconductor photocatalysis degrades phenolic pollutants to carbon dioxide and water, but the mechanisms of this potentially attractive method of environmental remediation remain unclear. This study aimed to elucidate the primary molecular events by HPLC analysis of the initial products of degradation in water or aqueous acetonitrile. The position of substituents relative to the hydroxyl group were found to influence the reaction rate and also primary oxidation steps, and hence the intermediate profile. 2,6- Dialkylated phenols reacted fastest and showed high conversion to dehydrodimeric products as a prelude to degradation. In contrast, 3,5-dialkylated phenols and 4-tertbutylphenol reacted more slowly and appeared to degrade directly to small polar compounds with little accumulation of primary carbocyclic intermediates. The rate of photocatalytic degradation of two isomeric dibromohydroxybenzonitriles was also influenced by substitution pattern. 3,5-Dibromo-2-hydroxybenzonitrile, however, is itself photolabile in daylight giving 3-bromo-2,5-dihydroxybenzonitrile in aqueous solution. The analogous reaction does not occur for 3,5-dibromo-4-hydroxybenzonitrile, the difference in behaviour being attributed to differences in the electronic spectra of the two compounds. The mechanism of photocatalysis appears to be influenced by the orientation of the substrate on the catalyst surface. For the alkyl phenols, particularly those with tert-butyl substitution, minimisation of disturbance to the polar network of the solvent directs the more hydrophobic parts of the molecule towards the oxidising surface of the catalyst. In addition, this effect encourages clustering of molecules with the subsequent formation of aggregated products. While part of the behaviour observed may be attributable to the presence of acetonitrile in the solvent, the hydrophobic profile of a substrate undergoing heterogeneous photocatalytic oxidation in water would seem to be a significant determinant of the molecular pathway selected in the first phase of its degradation.

The Li-Ti-S ternary system was investigated. The elements and/or compounds, such as lithium sulfide, titanium disulfide and titanium trisulfide, were combined at high temperature (typically 500-900°C). The synthesized compounds containing one or more phases were structurally characterized using x-ray powder diffraction. When Lix TiS₂, (0 ≤ x ≤ 1) was synthesized at elevated temperature, a new polytype, 3R-LixTiS₂, was found for some values of x. The regions of stability of the 3R polytype and the well known 1T polytype are presented. Lithium can be intercalated or de-intercalated from both polytypes at room temperature. Ambient temperature Li/3R-LixTiS₂ cells have higher average voltages than Li/1T-Li TiS₂, cells. The lithium spinel oxides are another class of materials receiving attention as cathode materials in lithium secondary batteries. LiTi₂0₄ is metallic, has the cubic spinel structure and reacts with one further lithium atom to form Li₂Ti₂0₄. The related spinel Li₄/₃Ti₅/₃⁰₄͵ which is electrically insulating, also reacts reversibly with one lithium atom. Both Li₂Ti₂0₄ and Li₄/₃Ti₅/₃⁰₄͵ cells cycle reversibly, but have subtle differences in their voltage profiles. The difference in cell behaviour was interpreted based on the band structure of Li₁˖xTi₂₋x⁰₄. The mixed spinels LiMnyTi₂₋y⁰₄ (0 ≤ y ≤ 2) were also investigated. These compounds were synthesized at high temperature but their performance as cathodes in lithium batteries was not encouraging.<br>Science, Faculty of<br>Physics and Astronomy, Department of<br>Graduate

This Thesis describes the synthesis and characterisation of titanium hydrazido(2-) and alkylidene hydrazido(2-) complexes and their reactivity towards unsaturated molecules. Exploration of the bonding in titanium hydrazido(2-) and alkylidene hydrazido(2-) complexes is performed through structural and computational studies. Chapter 1 introduces current Group 4 hydrazido chemistry in comparison to Group 4 imido and mid/late metal hydrazido examples. Current Group 4 alkylidene hydrazido chemistry is also described. Chapter 2 describes the synthesis, bonding and the novel reaction chemistry of titanium hydrazido(2-) half-sandwich complexes. Novel reactivity at the Ti=N, bond is presented with the mechanisms of some of these transformations probed by Density Functional Theory (DFT) calculations. Chapter 3 describes the novel reaction chemistry of Cp*Ti{MeC(Nipr)2} (NNMe2) in comparison to its imido and diphenyl hydrazido analogues. Novel reactivity at both Ti=N, and Na-N~ bonds is presented with the mechanisms of some of these transformations probed by Density Functional Theory (DFT) calculations. Chapter 4 describes the synthesis and characterisation of a new titanium alkylidene hydrazido(2-) complex. The bonding of the alkylidene hydrazido(2-) ligand is explored through structural and computational studies. Novel reactivity at Ti=N, and Na-N~ bonds is presented. Chapter 5 presents full experimental procedures and characterising data for the new complexes reported. CD Appendix contains .cif files for all new crystallographically characterised complexes described.

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2005.<br>Ashok Saxena, Committee Member ; Carlos Santamarina, Committee Member ; Thomas Kurfess, Committee Member ; Hugo Ernst, Committee Member ; Steven Danyluk, Committee Chair ; David McDowell, Committee Member. Vita. Includes bibliographical references.

Novel low temperature wet chemical processes for the synthesis of gels and ultrafine powders of BaTiO₃ and BaTi₄O₉ were developed. Under acidic conditions a titanyl acylate precursor was obtained by molecular modification of titanium isopropoxide. In the sol-gel process, amorphous BaTiO₃ gels obtained under acidic conditions were heat treated at ≈950-1000°C yielding fine (≈ 1-3 μm), high purity (99.9%) stoichiometric (Ba/Ti = 0.99) BaTiO₃ powders. In the sol-precipitation process, ultrafine (≈ 10 nm) crystalline BaTiO₃ powders were directly precipitated at low temperatures (<100°C) from a stoichiometric titanium acylate- barium acetate sol (pH > 13.5). Precursor powders obtained by hydrolytic decomposition of barium and titanium alkoxides were heat treated at 1100°C to obtain high purity, homogeneous, single phase BaTi₄O₉ powders. Atomistic pathways for the evolution of crystalline phases from amorphous gels and powders were investigated. The microstructure and electrical properties of sintered BaO-TiO₂ ceramics were studied and correlated with the powder processing conditions. The structures of crystalline and amorphous forms of some materials in the BaO-TiO₂ system were simulated using molecular dynamics computer techniques to develop a fundamental understanding of structure-property relationships for BaTiO₃ and TiO₂ containing glasses.

This Thesis describes the preparation and characterisation of a range of titanium imido complexes supported by a cyclopentadienyl-amidinate ligand set. Reactivity studies of these complexes towards unsaturated organic species are presented. <strong>Chapter 1</strong> reviews transition metal complexes containing imido, cyclopentadienyl, and amidinate ligands, with an emphasis on recent work. <strong>Chapter 2</strong> describes the synthesis and characterisation of titanium cyclopentadienyl imido amidinate complexes, along with precursor complexes which have not been previously reported. X-ray crystal structures of four imidotitanium species are described. <strong>Chapter 3</strong> describes the reactivity of titanium cyclopentadienyl imido amidinate complexes towards carbon dioxide. An unprecedented reaction with two molecules of carbon dioxide is reported for the arylimido complexes. X-ray crystal structures of two of the arylimido dicarboxylate products are described. The kinetics of the insertion of the second molecule of carbon dioxide are investigated and reported. <strong>Chapter 4</strong> describes the reactivity of titanium cyclopentadienyl imido amidinate complexes towards isocyanates and carbodiimides. The X-ray crystal structures of two N, O- bound ureate complexes are described. A new series of reactions involving two molecules of p-tolyl isocyanate with arylimido complexes is reported. Reactions of isocyanates with carbamate complexes are also reported. <strong>Chapter 5</strong> explores the reactivity of titanium cyclopentadienyl imido amidinate complexes towards sulfur-containing substrates. Comparisons are drawn with the reactivity towards oxygen-bearing homologues. X-ray crystal structures of two bridging sulfido complexes are described. <strong>Chapter 6</strong> discusses the reactivity of titanium cyclopentadienyl imido amidinate complexes towards substrates containing only one unsaturated linkage. Reactions with organic carbonyls and terminal alkynes are found to afford equilibria rather than isolable products. <strong>Chapter 7</strong> details full experimental procedures for all syntheses and reactions described in the text. <strong>Chapter 8</strong> contains characterising data for all new compounds reported. Full tables of crystallographic data for all new crystallographically characterised complexes described herein are presented in <strong>Appendices A-H, J-M</strong>. <strong>Appendix I</strong> contains kinetics data relating to work discussed in Chapter 3.

Avec la reduction des dimensions caracteristiques des circuits integres, il est necessaire de diminuer les capacites entre lignes d'interconnexions ainsi que leurs resistances et d'ameliorer la fiabilite des interconnexions. L'introduction d'une metallisation cuivre permet de depasser les limitations actuelles. Cependant, l'integration du cuivre dans des structures d'interconnexions necessite l'introduction de nouveaux materiaux. Ces couches d'interface doivent verifier les proprietes suivantes : * empecher la diffusion du cuivre dans le silicium et dans les dielectrique meme pour des epaisseurs de films inferieures a 20 nm * avoir une faible resistivite (<300cm) * etre une couche d'interface assurant l'adherence du cuivre sur son substrat, permettant ainsi d'utiliser le polissage mecano-chimique lors de la fabrication des interconnexions en architecture double damascene * conformite de la couche deposee sur des motifs de facteurs de forme elevee (>4) le nitrure de titane (tin) est utilise couramment comme materiau barriere de diffusion et comme couche d'adherence dans l'industrie des semi-conducteurs. Le depot pvd de tin ne permet pas d'obtenir une bonne conformite de la couche deposee sur des motifs a facteurs de forme eleve. Le depot de tin par cvd a partir d'une chimie inorganique conduit a des couches a resistivites importantes contenant un pourcentage de chlore eleve a des temperatures inferieures a 500c. Au cours de cette etude, nous avons evalue et optimise un nouveau procede de depot cvd qui consiste a repeter de facon recurrente un depot pyrolytique du tin a partir d'un precurseur organometallique, le tetrakis (dimethylamino) titane (tdmat) et un traitement du film avec un plasma n#2/h#2. Les parametres de l'etude sont l'epaisseur initiale de la couche avant le traitement plasma (5 et 10 nm), la puissance du plasma et de la duree du traitement. Une correlation a ete realisee entre les performances en tant que couche barriere a la diffusion du cuivre et couche d'adherence, et les caracteristiques intrinseques du materiau tin.

Microbial resistance to the current available antibiotics is considered a global health problem, especially for the Multi-Drug Resistant pathogens (MDR) including methicillin resistant Staphylococcus aureus. Recently nanoparticles (NPs) have been involved in variety of antimicrobial applications due to their unique properties of antibacterial effects. However, the molecular mechanisms behind their antibacterial activity are still not fully understood. In this study, we produced silver Ag NPs (average size 27 nm) and silver-Titanium Ag-TiO2 NPs (average size 47 nm) using picosecond laser ablation. Our results showed that both laser NPs had obvious size-dependent antibacterial activity. The laser Ag NPs with a size of 19 nm and Ag-TiO2 NPs with a size 20 nm presented the highest bactericidal effect. The laser generated Ag and Ag-TiO2 NPs with concentrations 20, 30, 40, and 50 Î1⁄4g/ml showed strong antibacterial effect against three bacterial strains: E. coli, P. aeruginosa, and S. aureus, and induced the generation of reactive oxygen species (ROS), lead to cell membrane interruption, lipid peroxidation, DNA damages, glutathione depletion and the eventual cell death. Both types of laser NPs at two concentrations (2.5 and 20 Î1⁄4g/ml) showed low cytotoxicity to the in vitro cultured five types of human cells originated from the lung (A549), kidney (HEK293), Liver (HepG2), skin (HDFc) and blood vessel cells (hCAECs). The antibacterial activity of the laser generated Ag and Ag-TiO2 NPs had lasted for over one year depending on the degree of air exposure and storage conditions. Frequent air exposure increased particle oxidation and reduced the antibacterial durability of the laser generated Ag NPs. The laser generated Ag NPs had lower antibacterial activity when stored in cold compared to that stored at room temperature. The antibacterial activity of laser generated Ag and Ag-TiO2 NPs were also compared with four types of commercial based-silver wound dressings (Acticoat TM, Aquacel® Ag, Contreet ®Foam, and Urgotul® SSD) against E. coli to inform future application in this area. In conclusion, laser generated Ag and Ag-TiO2 NPs have strong bactericidal effect and low toxicity to human cells which could be a type of promising antibacterial agents for future hygiene and medical applications.

This thesis discusses the investigation of the two-dimensional S = œ Heisenberg antiferromagnet copper formate tetrahydrate (CFTH) and the layered triangular lattice material NaTi0₂ which was thought to be a candidate for the possession of a non-classical antiferromagnetic ground state due to the frustration inherent in a triangular antiferromagnet. Single crystals of CFTH are investigated using elastic, quasielastic and inelastic neutron scattering, electron spin resonance (ESR) spectroscopy and DC magnetometry. Using the appropriate theory, these measurements are used to determine values for the terms in the Hamiltonian which describes the interactions between the Cu²⁺ ions in this material. The Hamiltonian is compared with that of La₂Cu0₄, and the two are determined to be quite similar. There does not appear to be any evidence for a non-classical ground state in either material. This was proposed to exist in La₂Cu0₄ to account for the superconductivity of doped samples. The difficulties in preparing pure NaTi0₂ have been surmounted, and a technique is described for preparing powder samples with very reproducible structural and magnetic properties. The structural properties have been investigated using X-ray and neutron diffraction, the latter at temperatures between 100 K and room temperature. The magnetic properties have been probed using DC magnetometry and ESR spectroscopy. The sample dependence of the structural and magnetic properties of samples prepared in slightly different ways is discussed. The temperature dependence of the magnetic susceptibility and of the structural parameters is explained by comparison with other oxides and chlorides of trivalent Ti and V, many of which show similar behaviour. The magnetic and structural changes which occur between 200 and 250 K are assigned to changes in the Ti-Ti bonding within the layers, which leads to a transition between two metallic states with subtle differences in their band structures.

L'aluminiure de titane ti-25al-10nb-3v-1mo (% at. ), egalement denomme super-alpha2, represente un alliage intermetallique susceptible de remplacer les alliages de titane conventionnels utilises a l'heure actuelle dans l'aeronautique: il allie une faible densite par rapport aux superalliages, une plus grande resistance mecanique et une meilleure tenue a l'oxydation que les alliages de titane conventionnels. Par ailleurs, son aptitude a presenter des proprietes superplastiques a haute temperature peut constituer un procede de mise en forme industriel de cet alliage. L'objet de ce travail a ete, dans un premier temps, de caracteriser la microstructure du super-alpha2 dans son etat initial, de determiner les conditions optimales de deformation superplastique en traction ainsi que de realiser une description rheologique du comportement a chaud de cet alliage en vue de l'introduire dans des codes de calculs de mise en forme industrielle. Une attention particuliere a egalement ete portee sur l'etude des transformations microstructurales induites par la deformation. Dans un deuxieme temps, les mecanismes de deformation de cet alliage biphase ont ete identifies afin de les prendre en compte dans une loi de comportement. Le role des phases ainsi que l'importance du glissement interfacial vis-a-vis de la deformation superplastique ont ete etudies. Enfin, une forme generale de loi de comportement prenant en compte la proportion des phases, la taille et la morphologie de la microstructure a ete proposee

Les acides retinoiques all trans et 13-cis offrent un grand interet dans le domaine medical, en particulier pour le traitement de maladies de la peau. En vue d'obtenir des structures offrant un meilleur indice therapeutique, differents analogues de l'acide retinoique ont ete synthetises. Dans une premiere partie, une synthese originale de chromannes est decrite. Dans une seconde partie, les analogues sont prepares par reaction de wittig mais il s'avere que la purification des isomeres est extremement difficile. En vue de supprimer le probleme de la separation, il a ete realise une etude utilisant le titane a degre d'oxydation zero. Il a ete montre que l'utilisation de cette nouvelle methode permettait de preparer une chaine polyenique all trans ainsi qu'une chaine polyenique presentant un maillon cis terminal. Cette methode a ete utilisee pour preparer des exemples en serie terpenique ainsi qu'en serie aromatique

Chemical oxygen demand (COD) is an important water quality parameter for estimating organic pollution. Conventional COD method has several drawbacks including lengthy assay time, complex procedure and requiring the use of highly toxic and expensive chemicals. Considerable efforts have been devoted to improve conventional COD methods. In this regard, the PeCODTM method has been the most noticeable technique. This method utilizes the superior oxidation power of UV illuminated nanostructured titanium dioxide (TiO2) to achieve organic degradation while simultaneously enabling quantification of the COD value by directly measuring the photocatalytic oxidation current/charge that originated from photocatalytic degradation of organics. The method is an absolute method that requires no calibration. It is an environmentally friendly method that requires/generates no toxic reagent. It is a simple and rapid method for sensitive and accurate COD determination. However, PeCODTM method needs to be improved in few aspects for more broad applications, especially for the field-based applications. These include the portability and high degradation efficiency for those oraganic compounds with difficulty to be oxidized. This study is therefore focused on improving the portability and applicability of PeCODTM method.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>Griffith School of Environment<br>Science, Environment, Engineering and Technology<br>Full Text

Thesis (MScEng)--Stellenbosch University, 2004.<br>ENGLISH ABSTRACT: During the production of pure Ti02 for the pigment industry, ilmenite, containing 35 - 60 % Ti02, is reduced to high titania slag, containing 85 - 95 % Ti02 and pig iron. These ilmenite smelters are operated in very tight operating windows. Over reducing the slag may lead to the formation of TiC and reducing much of the Ti02 to Th03. According to Namakwa Sands furnace operators, this does not only affect the grade of the product, but it can cause slag foaming and furnace eruptions. In under reducing conditions, the liquid slag is fluxed by the FeO and may corrode the furnace lining and consequently lead to run-outs. The reducing conditions in the furnace are not only controlled by carbon addition, but also by temperature. Standard practise in industrial ilmenite smelters is to operate the furnace with a slag freeze lining to protect the refractory lining from chemical and physical attack by the slag. It is therefore clear that it is of great importance to be able to predict the slag liquidus temperature at different compositions. This can help the operator to avoid dangerous operating conditions. Over the past few decades, a number of solution models have been developed to describe non-ideal solutions. With the rapid increase in computer power, these models became more valuable and practical to use in advanced control and decisionsupport. In this study, some of the better-known models are discussed and evaluated for the Ti02 - Th03 - FeO system, based on a critical review of properties and measurements published in literature. Two of these models, the "modified quasi-chemical" model and the "cell" model were chosen to be applied to the high-titania slag system. Both these models are based on statistical thermodynamics with some differences in the initial assumptions. In this study, the model parameters for the cell model were regressed from experimental data. The high-titania slag produced, consists mainly of titanium in different oxidation states and FeO, placing its composition inside the Ti02 - Th03 - FeO ternary system. Reliable experimental data for this system are very limited. All three binary systems contained in the Ti02 - ThO) - FeO system were considered, namely FeO - Ti02, Ti02 - ThO) and FeO - ThO). Only liquidus data for these three binaries were used to regress the model parameters. Accuracy of the models was determined by calculating the root mean square (RMS) error between the experimental data point and the value calculated using the model and the newly determined model parameters. These errors corresponded weil with the reported experimental error of the datasets for both the models and all the binary systems. Due to the fact that this study focussed on the liquidus surface of the system, the results were also plotted in the form of binary phase diagrams and ternary liquidus isotherms. The cell model uses only binary interaction parameters to describe the ternary system. These parameters are not expanded to higher order polynomials, which makes this model more robust, but also less accurate than other models such as the modified quasi-chemical model.<br>AFRIKAANSE OPSOMMING: Tydens die produksie van suiwer Ti02 vir die pigmentbedryf, word ilmeniet, wat 35 tot 60 % Ti02 bevat, gereduseer tot 'n hoë titaan slak, met 'n Ti02 inhoud van 85 tot 95 % Ti02, en potyster. Hierdie ilmeniet smeltoonde word binne baie nou bedryfskondisies beheer. Oor-redusering van die slak kan lei tot the formasie van TiC en die redusering van Ti02 tot Th03. Dit affekteer nie net die produk se kwaliteit nie, maar kan volgens Namakwa Sands oond operateurs ook slak skuiming en ontploffings tot gevolg hê. Gedurende onder-reduserende omstandighede in die oond, word die vloeibaarheid van die slak verhoog deur die hoër FeO inhoud in die slak. Dit maak die slak meer korrosief en kan lei tot faling van die vuurvaste stene. Die mate van redusering in die oond word nie net bepaal deur die toevoeging van koolstof nie, maar ook deur die temperatuur van die slak. Dit is 'n standaard praktyk van die industrie om die oond te bedryf met 'n gevriesde slak laag om sodoende die vuurvaste stene te beskerm teen chemiese en fisiese aanval van die slak. Dit is dus duidelik dat dit baie belangrik is om die slak se smeltpunt by verskillende samestellings te kan voorspel. Dit kan die operateur help om die oond binne veilige bedryfskondisies te hou. 'n Hele aantaloplossingsmodelle is oor die afgelope paar dekades ontwikkel vir die beskrywing van nie-ideale oplossings. Hierdie modelle het oor die afgelope paar jaar baie toegeneem in praktiese waarde as gevolg van die snelle toename in rekenaarkapasiteit en -spoed. Dit het veral groot waarde in gevorderde beheerstelsels en besluitneming steun. Sommige van die meer bekende modelle word in hierdie studie bespreek en ge-evalueer vir die Ti02 - Th03 - FeO stelsel, gebaseer op 'n kritiese evaluasie van eienskappe en eksperimentele data gepubliseer in die literatuur. Twee van hierdie modelle, die "gemodifiseerde kwasi-chemiese" model en die "sel" model, is gebruik om die hoë titaan slak stelsel te beskryf. Beide hierdie modelle is gebaseer op statistiese termodinamika en het klein verskille m.b.t. die aanvanklike aannames. Die model veranderlikes vir die sel model is in hierdie studie afgelei vanaf die eksperimentele data. Die hoë titaan slak wat tydens hierdie proses geproduseer word, bestaan hoofsaaklik uit FeO en titaan in sy verskillende oksidasie toestande. Dit plaas die samestelling van die slak reg binne die Ti02 - Th03 - FeO temêre stelsel. Betroubare eksperimentele data vir hierdie stelsel is baie beperk. In hierdie studie word daar gekyk al drie binêre stelsels binne die Ti02 - Th03 - FeO temêre stelsel, naamlik: FeO - Ti02, Ti02 - Th03 en FeO - Th03. Slegs die smeltpunt temperatuur data vir hierdie twee binêre is gebruik in die afskatting van die model veranderlikes. Die akkuraatheid van die modelle is bepaal deur die wortel van die gemiddelde kwadraat van die fout tussen die eksperimentele waardes en die berekende waardes te bepaal. Albei die modelle het 'n relatiewe klein fout in vergelyking met die geraporteerde eksprimentele fout gehad vir al die binêre stelsels. Hierdie studie het gefokus op die smeltpunt temperatuur van die slak en die resultate is daarom ook in die vorm van binêre fasediagramme en isoterme projeksies op die temêre fasediagramme gestip. Die "sel" model gebruik slegs binêre interaksie parameters om die temêre stelsel te beskryf Hierdie parameters word vir die "sel" model nie uitgebrei tot hoër order polinome en dit maak die "sel" model meer robuust, maar minder akkuraat as ander modelle soos byvoorbeeld die "kwasi-chemiese" model.

This thesis concerns the synthesis and characterisation of novel bis(diketonate) titanium dihalides. The compounds synthesised during the course of this work have been evaluated as potential anti-tumour agents. Chapter 1 comprises a brief review of the literature on of the role of titanium in transition metal anti-tumour agents as well comments on the industrial uses of the bis(diketonate) ligand. Chapter 2 compares the novel crystal structures of la 1,3-p-diketonatc molecules as well as the synthesis and characterisation of three novel bis(diketonatc) titanium isopropoxidc compounds. Chapter 3 concerns the synthesis and characterisation of 12 novel bis(diketonate) titanium dichlorides along with 8 novel crystal structures. In addition 5 novel mono(diketonate) titanium trichloridcs along with 4 novel crystal structures. Chapter 4 describes the synthesis and characterisation of 14 novel bis(dikctonate) titanium dibromides along with 8 novel crystal structures. Chapter 5 gives an account of the biological evaluation of a series of the bis(diketonate) titanium compounds including an SRB assay and DNA binding study. The SRB assay revealed one compound, 4.2, to show anti-tumour activity comparable to that of cisplatin in the A2780eis cell line. There is also a section on future work defining key features for further study. Chapter 6 represents experimental details and characterisation data for the compounds described in Chapters 1-5.

Les procédés de projection thermique permettent de fabriquer des revêtements d’une grande versatilité (métaux, céramiques, polymères ou autres composites), relativement épais (de quelques microns à plusieurs centimètres) avec une vitesse de dépôt relativement importante. Cependant des contraintes existent notamment l’impossibilité d’utiliser des précurseurs à fusion non congruente tels que les nitrures (TiN par exemple) limitant leur application industrielle (aéronautique, énergie, biomédical, etc.). Ce type de revêtement est principalement obtenu par les procédés couches minces. La projection plasma sous très basse pression (VLPPS) ouvre un potentiel pour s’affranchir de cette problématique d’obtenir des revêtements nitrures et présente en plus l’avantage d’avoir des vitesses de dépôt élevées au contraire des procédés couche mince. Pour cela, la phase liquide habituellement créée par l’injection de la poudre dans la source thermique des procédés de projection peut s’élever à l’état de vapeur du fait des conditions de très basse pression. En conséquence, des revêtements denses à microstructure lamellaire, de vapeurs condensées ou mixte sont formés. Mais encore, le matériau à l’état vapeur peut être mis en contact avec un gaz réactif (azote, oxygène, etc.) pour former un composé nitruré, oxydé.Ce travail a consisté à étudier la réalisation de revêtements céramiques oxydes et nitrures par projection plasma sous très basse pression réactive (R-VLPPS) à partir d’une poudre pure de titane. Tout d’abord, le diagnostic du jet plasma sous très basse pression (gaz plasmagène et réactif, précurseur) a été réalisé dans le but de corréler la présence des espèces détectés avec les propriétés des revêtements. Ainsi, des revêtements de nitrure et d’oxyde de titane ont été fabriqués par R-VLPPS. Les paramètres de réalisation des dépôts (distance de projection, méthode d’injection du gaz réactif) ont été analysées. Les caractéristiques mécaniques des compositions obtenues ont été déterminées. Le jet plasma a aussi été testé comme moyen de post traitement pour améliorer la proportion de phases nitrurées ou oxydées. Enfin, le mécanisme de construction des revêtements a été développé à partir des résultats expérimentaux<br>Thermal spraying processes allow the manufacturing of high versatility coatings (metals, ceramics, polymers or other composites), relatively thick (from few microns to several centimeters) with a high deposition rate. However, drawbacks exist in particular the impossibility to use non-congruent fusion precursors such as nitrides (TiN for example) limiting their industrial application (aeronautics, energy, biomedical, etc.). This kind of coating is mainly obtained by thin-film processes. Very low-pressure plasma spraying (VLPPS) opens a potential to overcome this problem to obtain nitride/oxide/carbide coatings with high deposition rates unlike thin-film processes. For this purpose, the liquid phase usually generated by the particles injection into the thermal source of the spray jet can rise to the vapor state due to the conditions of the very low pressure. As a result, dense coatings with a lamellar, condensed vapors or a mix of both microstructures are manufactured. Furthermore, a reactive gas (nitrogen, oxygen, etc.) can be injected with the vapors to form oxide, nitride materials.This work consisted in studying the fabrication of oxides and nitrides ceramic coatings by reactive - very low-pressure plasma spraying (R-VLPPS) from a pure powder of titanium. Firstly, the diagnostic of the plasma jet under very low pressure (plasma and reactive gases, precursor) was carried out with the aim of correlating the presence of the detected species with the properties of the coatings. Titanium nitrides and oxides coatings were manufactured by R-VLPPS. The spraying parameters of the deposits (spraying distance, reactive gas injection method) were analyzed. The composition and the mechanical characteristics of the coatings are determined. Moreover, the plasma jet has also been tested as post-treatment process to improve the amount of nitrided or oxidized phases. Finally, the manufacturing mechanism of the coatings was developed from the experimental results

Made available in DSpace on 2014-10-09T12:34:52Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:08:21Z (GMT). No. of bitstreams: 0<br>Dissertação (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Cp$ sb2$Ti(C))$ sb2$, where Cp = $ eta sp5$-cyclopentadienyl, reacted with RSSSR to give the catenated sulfur complexes Cp$ sb2$Ti(SR)(SSR), where R = CMe$ sb3$, CHMe$ sb2$, CH$ sb2$Ph, p-C$ sb6$H$ sb4$Me and CPh$ sb3$. These complexes, except for R = CPh$ sb3$, reacted with PhCH$ sb2$Br to give Cp$ sb2$TiBr$ sb2$, PhCH$ sb2$SR and PhCH$ sb2$SSR as major products. Cp$ sb2$Ti(SR)(SSR) desulfurized slowly in solution and rapidly in the presence of Ph$ sb3$P, giving Cp$ sb2$Ti(SR)$ sb2$ and Ph$ sb3$PS, in addition to other species. Similarly, phth-SSR, where phth = phthalimide, oxidatively added to Cp$ sb2$Ti(CO)$ sb2$ to give Cp$ sb2$Ti(X)(SSR), where X = phth and R = CMe$ sb3$, CHMe$ sb2$, CH$ sb2$Ph and p-C$ sb6$H$ sb4$Me. Solvolysis by MeOH and EtOH gave the species where X = OMe and OEt. In a similar manner Ph$ sb3$CSSCl added to Cp$ sb2$Ti(CO)$ sb2$ to give Cp$ sb2$Ti(Cl)(SSCPh$ sb3$). Treatment of Cp$ sb2$Ti(SR)(SSR) with (norbornadiene)Mo(CO)$ sb4$ gave the bridged dimers, (Cp$ sb2$Ti($ mu$-SR)-($ mu$-S$ sb{ rm x}$R)Mo(CO)$ sb4$), where x = 1 and 2 and R = CMe$ sb3$ and CHMe$ sb2$. The complexes where x = 2 contained the rare iso-$ mu$-$ eta sp1$-SSR ligand. In solution at low temperatures the bridging thiolato and disulfano groups were predominantly transoid. At higher temperatures, a dynamic process that allowed averaging of cyclopentadienyl ring environments took place. $ sp1$H NMR studies permitted evaluation of $ Delta{ rm G sbsp{c}{ ddagger}}$ for the averaging process.

Thesis (Ph. D.)--University of Oregon, 2004.<br>Typescript. Includes vita and abstract. Includes bibliographical references (leaves 171-176). Also available for download via the World Wide Web; free to University of Oregon users.

Made available in DSpace on 2014-10-09T12:33:49Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:03:57Z (GMT). No. of bitstreams: 0<br>Dissertação (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Titanium is among the most commonly used metals as a standard treatment for bone defects. Despite its excellent mechanical and biocompatibility properties, Ti is relatively bioinert and surface modifications are necessary to improve its bioactivity. The sol-gel process allows this modification through the development of coatings with controlled release of bioactive compounds. On the other hand, the growing demand for biomaterials with better performances created the need to develop new in vitro methods more predictive of in vivo results. Considering this, the application of proteomics represents an interesting alternative to be explored. Herewith, the present doctoral thesis aimed to develop sol-gel coatings doped with different bioactive compounds and its characterization employing proteomics to determine predictive biomarkers of possible in vivo results.<br>Programa de Doctorat en Ciències Biomèdiques i Salut

A two-part study involving the synthesis and catalytic investigations of amidate complexes of early transition metals is described. In the first part, the substrate scope of an achiral bis(amidate) titanium hydroamination precatalyst has been broaden to include challenging substrates. This complex efficiently catalyzes the hydroamination of heteroatom-containing allenes with arylamines. Control experiments rule out allene-alkyne isomerization as a reaction pathway during this catalysis. The hydrohydrazination of a variety of alkynes with 1,1-disubstituted hydrazines also proceed efficiently in the presence of this precatalyst giving the anti-Markovnikov hydrazone products predominantly. These hydrazones have been transformed into substituted indoles by a one-pot tandem sequential hydroamination/ZnCl₂-mediated cyclization. Importantly, the bis(amidate) titanium precatalyst can be generated in situ for these reactions with no impact on the reactivity or selectivity of the complex. The second part of this thesis focuses on the synthesis, characterization, stability and catalytic investigations of chiral zirconium and tantalum complexes ligated with amidate ancillary ligands. Seven new axially chiral proligands have been synthesized and used for in situ generation of zirconium hydroamination precatalysts. These chiral complexes efficiently produce N-heterocycles in up to 94% isolated yield with ee reaching 74%. Preparative scale synthesis and characterization of the zirconium complexes revealed coordination geometry that is greatly influenced by the steric properties of the ligand. Bulky proligands produce monomeric complexes, wherein the biphenyl ligand displays a κ²-O,O-bonding motif which accounts for the modest enantioselectivities realized with this system. The less sterically-congested proligands initially form similar monomeric complexes; however, these complexes dimerize diastereoselectively to κ⁴-N,O,O-N-bonding amidate complexes within a few hours in solution. The binding motif of the amidate ligand of the chiral biphenyl tantalum complexes is also dictated by the size of the N-substituent of the ligand. While a bulky proligand results in a discrete tantalum κ²-O,O-bonding amidate complex, less sterically-encumbered proligands produce a mixture of κ²-O,O-bonding and κ³-N,O,O-bonding amidate complexes. Using these tantalum complexes as precatalysts, alkenes undergo hydroaminoalkylation reactions with secondary amines to give branched alkylated secondary amines in isolated yields of up to 92% and enantiomeric excesses reaching 66%, for the first examples of an enantioselective hydroaminoalkylation reaction.

Growing demand and shortages of potable water sources due to industrialization have become a great concern worldwide. Various approaches and solutions have been adopted to provide cleaner and quality water. In a preliminary study, a method of treating wastewater was investigated in which algae were used to remove nutrients (nitrogen and phosphorous) from wastewater and then the algae were harvested for use as a biofuel. The results from this investigation are included in the Appendix B. Employing traditional oxidants, such as hydrogen peroxide, chlorine, and ozone, for treatment of recalcitrant organic compounds have achieved less promising results. However, photocatalysis, an advanced oxidation process (AOP), which is a low-cost and high-efficiency technique, has been widely recognized as a promising approach for water purification and elimination of organic constituents in wastewater. Photocatalysis is the increase in the rate of a chemical reaction by employing a catalyst in the presence of photons. Generally, for a high performance photocatalyst, light of appropriate wavelength is used to activate a catalyst in close contact with contaminants, thereby modifying the rate of the reaction. The presence of these contaminants could pose potential health and environmental concerns, especially in a controlled environment such as on a space station or during long-term manned missions. Thus, the development of energy efficient and "green" technologies to reduce or eliminate organic constituents in wastewater has important potential applications. This research investigated the supported semiconductor photocatalysts (TiO2 and ZnO), particularly ZnO nanorods and nanowires, their synthesis methods, properties and corresponding effectiveness in photocatalysis. The effect of transition metal co-catalysts on the photocatalytic properties of TiO2 was investigated. Although TiO2 is the most extensively studied photocatalyst for water decontamination, ZnO, as presented in this work, could be a substitute because of its lower cost, relative energy bandgap and higher visible light photoactivity. Both photocatalysts were doped and screened for the decomposition of model contaminates, rhodamine B (RhB), phenol and methyl orange, under ultraviolet and/or visible light irradiation. In the photodegradation of RhB, TiO2/Ru 1% showed a superior photocatalytic activity relative to P25-TiO2 under broad-band irradiation, while doped ZnO-Ag resulted in better photodegradation of methyl orange, compared to P25-TiO2, under visible light irradiation. The morphology and estimated chemical composition of photocatalysts were determined by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). Brunhauer, Emmett and Teller (BET) analysis was utilized to measure mass-specific surface area(s). A X-ray diffraction (XRD) study was carried out to confirm the identity of photocatalyst phase(s) present. The cause of low photocatalytic activity under an inert atmosphere, the simple effective fabrication technique of doped ZnO nanowires over TiO2 and properties of the photocatalyst are also discussed.

L'electromigration est devenue un facteur majeur de limitation de la fiabilite des interconnexions. Dans un contexte industriel, le developpement de methodes de test accelere au niveau plaquette est aujourd'hui une necessite. Nous commencons cette these en evoquant les bases physiques de l'electromigration et les materiaux metalliques utilises pour realiser les interconnexions en microelectronique. Le chapitre suivant presente les differentes methodes et procedures de test de l'electromigration: test de duree de vie en etuve, tests tres acceleres sur plaquette, tests resistometriques, mesure de bruit l'influence des parametres geometriques est exposee, suivie de la presentation des principales structures de test specifiques. Nous decrivons alors le contexte de mise en uvre des tests, en developpant particulierement le principe de la methode test utilisee, ses variantes et le critere d'arret du test. Le profil de temperature est determine le long de structures nist et sweat, a l'aide d'un simulateur analytique d'une part, de mesures directes par interferometrie et thermoreflexion d'autre part. La temperature maximale de test autorisee est alors fixee a 300c. Par la suite, nous etudions en detail les mecanismes de defaillance du materiau multicouches tin/alcu/tin/ti et de certaines de ses variantes. Nous commencons par evaluer l'influence de la largeur des lignes et nous mettons en lumiere les caracteristiques specifiques des lignes bambou, liees a la diffusion a l'interface intermetallique. Dans un second temps, nous voyons l'influence de differents nettoyages de la couche de tin/ti effectues avant le depot de l'alcu, dans une technologie utilisant des prises de tungstene pour les contacts et les vias. L'analyse structurelle est reliee aux resultats de test d'electromigration. Nous developpons ensuite, les problemes generes par la presence d'une couche intermediaire de tial#3 dans le cas de tests acceleres. Enfin, nous definissons la methode de test la mieux adaptee en fonction du type de resultats desires

Ces bronzes de titane de type hollandite sont des composes a vfalence mixte de formule generale a::(x)tio::(2), avec a=k, rb, cs et 0,125 <x<0,25. Proposition de differentes voies de synthese. Le caractere de valence mixte est mis en evidence par des etudes physiques (magnetisme, rpe, esca, conductivite). Etudes de diffractions rx et electronique, ainsi que de microscopie electronique en transmission a haute resolution, et mise en evidence de differents types d'ordre dans les cristaux. La mise en oeuvre de la chimie douce d'oxydoreduction permet d'obtenir des monocristaux de bronze partiellement oxydes et une nouvelle variete d'oxyde de titane ayant la structure hollandite. Le traitement thermique de celle-ci conduit a la forme anatase du dioxyde de titane a 400**(o)