This thesis is concerned with the preparation of mixed silicon-titanium oxides (Ti02=4.1-21.9wt%) and silicon-zirconium oxides (Zr02=4.1-22.Iwt%) by the sol-gel route. Methods of preparing homogeneous Si02-TiO2 gels and SiO2-Zr02 gels have been explored. In this work bis(acetylacetonato)titanium diisopropoxide or bis(acetylacetonato)zirconium dipropoxide and tetraethyl orthosilicate (TEOS) have been hydrolysed simultaneously in iso-propanol to form homogeneous gels. Using these systems, the effects of the reaction conditions, amount of titania/zirconia present in the gel, drying conditions and thermal treatment of the dry gels on the bulk and structural properties have been investigated by a variety of experimental methods including X-ray diffraction, mid- and near-infrared spectroscopy and gas adsorption techniques. For SiO2-TiO2 powders and monoliths, and SiO2-ZrO3 monoliths, thermal treatment has been found to significantly reduce the surface area (from 750-1.0m2g-1), pore volume (from 0.56-0.001cm3g-1') and relative number of silanol groups on the surface of the sample above 700°C. Average pore diameters remain constant at temperatures below 900°C (ca 54-21Å for monoliths), although the micropore volume does decrease (0.04-0.0cm3g-1) suggesting that smaller pores are destroyed by the heating process. For SiO2-TiO2 powders, the average pore diameter was ca IOÅ larger than for the corresponding monolith suggesting that small pores are destroyed during powdering. At 1100°C, gas adsorption data indicate that the samples are fully densified. This is supported by NIR spectra which detect no silanol groups on the surface of the sample. Structural changes arising from compositional changes and differing thermal treatment regimes have been monitored using mid-infrared spectroscopy and X-ray diffraction. With increasing temperature the silica matrix strengthens and titanium/zirconium are incorporated into the matrix. Monolithic SiO2-TiO2 gels (Ti02=6.34 weight%) remained amorphous at 1100°C, whereas powders began to exhibit diffraction patterns predominantly from anatase at 700°C. Anatase crystallite sizes have been calculated using the Scherrer equation and have been found to be between 16.3 and 5.4nm. Monolithic SiO2-ZrO2 gels containing 4.1 and 4.9 weight% zirconia were found to be amorphous after treatment at 1100°C. Increasing the zirconia content to 6.4 and 22.1 weight% resulted in gels that were amorphous up to 900°C. Further treatment at 1100°C, resulted in tetragonal zirconia and some cristobalite being formed. Crystallite sizes have been calculated as being between 2.7 and 1.6nm for tetragonal zirconia and from 4.1 to 2.8nm for cristobalite. Increasing the levels of titania/zirconia in the sample resulted in higher relative levels of hydrogen-bonded silanol groups. On hydration, the increased levels of titania/zirconia resulted in no observable free silanol groups on the surface suggesting that the surface becomes more hydrophilic as the amount of titania/zirconia present in the sample increases. This suggests that water becomes more tightly bound to Ti-OH /Zr-OH groups on the surface and within the pores, resulting in fewer free silanol type groups. A double alkoxide bis(acetylacetonato)titanium di(triethoxysilane) [Ti(acac)2(OSi(OC2H5)3)2] has also been synthesised and characterised. Mixed Si02-TiO2 gels have also been prepared by the simultaneous hydrolysis of Ti(acac)2(OSi(OC2H5)3)2 and TEOS under acidic conditions in ethanol. The effects of reaction conditions and thermal treatment of the dry gels have been investigated. Increasing the treatment temperature of the samples resulted in the progressive decrease in surface area (533-3.0m2g-1), pore volume (0.18-0.003cm3g-1), micropore volume (0.06-0.00cm3g-1) and relative number of silanol groups on the surface. However, the average pore diameter remained constant at temperatures up to 700°C. Changes in pore volume (0.07-0.005cm3g-1), surface area (300-3.0m2g-1) and average pore diameter (26.9-91.9Å) were largest at 900°C, and the samples were found to be almost completely dense. This was confirmed by the absence of observable silanol groups by NIR spectroscopy. After heating at temperatures up to 900°C, the samples were found to be amorphous by XRD. However increasing the temperature to 1100°C resulted in the formation of some crystalline anatase. The anatase crystal sizes have been calculated as being from 16.3 to 10.8nm in diameter. NIR studies of silica-zirconia and silica-titania gels (prepared by both methods), indicate that decreasing the amount of acid used in the hydrolysis reaction resulted in higher relative levels of hydrogen bonded silanol species. Similarly, decreasing the amount of acid increased the micropore volume and decreased the mesoporosity of the resulting samples. Generally, decreasing the amount of acid used for the hydrolysis for silica-zirconia and silica-titania gels (prepared by both methods), results in a decrease in the overall surface area and pore volume of the resulting material. The resulting isotherms indicate that the samples became less mesoporous as the amount of acid used in the hydrolysis reaction decreased. This was accompanied by an increase in the micropore volume. For SiO2-TiO2 monoliths prepared from a double alkoxide and Si02-ZrO2 monoliths the resulting pore structure is more rigid and composed of smaller pores than that of SiO2-TiO2 powders and monoliths prepared from bis(acetylacetonato)titanium diisopropoxide.

Cette étude s’est portée sur l’interaction des empilements diélectriques nitrure/oxyde avec la répartition du bore dans les zones sources et drain après le recuit d’activation. L’utilisation des procédés de dépôt des couches de nitrure et d’oxyde réalisées à basse température a permis de limiter l’impact de ces étapes de dépôt sur les performances électriques du dispositif. En revanche, des budgets thermiques de dépôt plus faibles induisent également une concentration d’hydrogène plus importante dans les films. Cette accumulation d’hydrogène dans les couches diélectriques en contact avec les zones source et drain augmente la quantité de bore pouvant diffuser depuis le silicium vers l’oxyde, ce phénomène entraine des modifications de la répartition du bore dans les zones implantées et par conséquent une modification des performances électriques du transistor. Au cours de ces travaux nous avons développé un modèle physique couplant les échanges d’hydrogène durant le recuit entre les couches de diélectrique et la diffusion du bore entre le substrat et l’oxyde. Ce modèle a été validé d’une part en simulant les profils de bore après recuit en fonction des différentes conditions de dépôt nitrure et oxyde, et d’autre part en couplant des mesures de contrainte mécanique avec des mesures de désorption thermique d’hydrogène. Ces travaux ont mis en évidence deux mécanismes de régulation de l’hydrogène dans la couche d’oxyde pendant le recuit. Le premier est le rôle de l’encapsulation du nitrure, la diffusion de l’hydrogène dans les nitrures étant plus faible que dans l’oxyde une partie de l’hydrogène dans l’oxyde en dessous est bloqué dans la couche durant le recuit. Le deuxième est le rôle du nitrure comme source d’hydrogène dans l’empilement. / This study has focused on the interaction of dielectric stacks nitride/oxide with the boron distribution in the source and drain areas after the activation annealing. The low temperature deposition processes of nitride and oxide layers limit the impact of these deposition steps on the electrical performance of the device. However the thermal budgets of lower deposit also induce a higher concentration of hydrogen. This hydrogen accumulation in the dielectric layer in contact with the source and drain regions increases the boron diffusion into the silicon oxide and causing modification of the boron distribution into the implanted zones and therefore an electrical performance modification of the device. In this work we developed a physical model combining the hydrogen exchange during annealing between the dielectric layers and boron out-diffusion between the substrate and silicon oxide. This model was validated firstly by simulating the profiles of boron after annealing for different deposition conditions nitride and oxide, and also by coupling measurements of mechanical stress with hydrogen thermal desorption spectroscopy (TDS). This research revealed two mechanisms of hydrogen regulation in oxide layer during annealing. First, the role of nitride encapsulation, hydrogen diffusion in nitride layer is lower than in oxide so hydrogen cannot degas out during anneal. The second is the role of nitride as a hydrogen source into the stack

Die vorliegende Arbeit befasst sich mit den Synthesen, Charakterisierungen und umfassenden Reaktivitätsstudien von unterschiedlich substituierten Organosilanolverbindungen, die ausgehend von den niedervalenten Siliziumverbindungen Tetramesityldisilen Mes2Si=SiMes2 (Mes = 2,4,6-Trimethylphenyl) und Hexakisarylcyclotrisilan (ArN2Si)3 (ArN = 2-[(Dimethylamino)methyl]phenyl) dargestellt wurden. Das durch Oxygenierung und Hydrolyse synthetisierte Tetramesitylsiloxandiol Mes2Si(OH)O(OH)SiMes2 wurde hinsichtlich seiner Reaktivität gegenüber Wasser und verschiedenen Ethern untersucht und dabei eingehend durch NMR- und IR-spektroskopische Analysen charakterisiert. Die Isolierung von Einkristallen ermöglichte darüber hinaus die Charakterisierung dreier polymerähnlicher Siloxandiol-Ether-Addukte im Festkörper. Neben Unterschieden der Struktur und Reaktivität in Lösung und im Festkörper konnte zusätzlich durch eine Kooperation mit Prof. Schalley (FU Berlin) anhand eines Gasphasenexperimentes des 18O-markierten Siloxandiolanions, in einem FT-ICR-ESI-Massenspektrometer der vollständige Austausch aller Sauerstoffatome durch Wassermoleküle nachgewiesen werden. Darüber hinaus führte die Einführung intramolekular stabilisierender Liganden wie in dem Siloxandiol ArN2(OH)Si(O)Si(OH)ArN2 zur vollständigen Austauschreaktion in organischen Lösemitteln. Ausgehend von dem [(Dimethylamino)methyl]phenylsubstituierten Cyclotrisilan (ArN2Si)3 konnte das Silylen-Lewispaar ArN2Si–B(C6F5)3 unter Einsatz der starken Lewis-Säure B(C6F5)3 isoliert werden. Durch Hydrolyse wird das Silanolboran ArN2H2OSi–B(C6F5)3 gebildet, das sich durch starke Wasserstoffbrückenbindungen zu den Aminsubstituenten auszeichnet. In Gegenwart von Base, H2O und Luft entsteht nach Dehydrogenierung und Kondensation das Borosiloxan [(HArN2(OB(C6F5)3)Si)2O]. Alle Verbindungen wurden isoliert und vollständig charakterisiert. Zusätzlich ergänzen DFT-Rechnungen (Prof. Kaupp, TU Berlin), die experimentell erhaltenen Beobachtungen. / The following thesis deals with the synthesis, characterization and detailed reactivity studies on differently substituted organosilanols, synthesized by the low valent silicon compounds tetramesityldisilene Mes2Si=SiMes2 (Mes = 2,4,6-trimethylphenyl) and hexakisarylcyclotrisilane (ArN2Si)3 (ArN = 2-[(dimethylamino)methyl]phenyl). Oxygenation and hydrolysis of tetramesityldisilene yielded tetramesitylsiloxanediol Mes2Si(OH)O(OH)SiMes2, the reaction behavior of which towards water and various ethers was studied by means of NMR and IR spectroscopy. Additionally, single crystal analysis delivered three different siloxanediol ether polymer-like structures in the solid state. Besides studies in solution and the solid state, gas phase reactions in a FT-ICR-ESI mass spectrometer of the 18O-labelled siloxanediol anion, showed complete exchange of all O-atoms in presence of gaseous water molecules (cooperation with Prof. Schalley, FU Berlin). Furthermore, we could show that altering the ligand system of the siloxanediol to the amine substituted siloxanediol ArN2(OH)Si(O)Si(OH)ArN2, resulted in a complete exchange of all oxygen atoms in solution when H217O was present. Starting from the [(dimethylamino)methyl]phenyl substituted cyclotrisilane (ArN2Si)3, formation of the Lewis acid stabilized silylene-borane ArN2Si–B(C6F5)3 was accomplished. In presence of water the silanolborane ArN2H2OSi–B(C6F5)3 was formed, showing characteristic strong intramolecular hydrogen bonding to its amino ligands. When reacted with a base and water under ambient air, a dehydrogenation reaction followed by condensation leads to the borosiloxane motif [(HArN2(OB(C6F5)3)Si)2O]. All compounds were isolated separately and fully characterized by means of NMR and IR spectroscopy, as well as X-ray diffraction analysis. In cooperation with Prof. Kaupp (TU Berlin), DFT-calculations were carried out to support the achieved experimental data.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

O processo de deposição de uma fina camada de zinco sobre o aço carbono por imersão a quente e posterior tratamento térmico gera como produto o aço galvannealed. O baixo custo do zinco e o fácil processo de aplicação faz com que o maior consumo deste metal seja aplicado na proteção da superfície do aço carbono de um meio agressivo a que ele esteja exposto. Esta camada de zinco não pode ser muito espessa, pois limita a soldabilidade, dificulta o acabamento após pintura e limita a aderência de tintas à superfície. Essa condição da fina espessura da camada de zinco depositada sobre o aço carbono torna necessário o desenvolvimento de revestimentos com espessuras menores, com melhores propriedades de dureza, ductilidade e resistência à corrosão mais elevada. Sendo assim, a superfície de zinco tem de ser pré tratada com a fosfatização e cromatização antes que as tintas possam ser devidamente aplicadas. No entanto, estes processos de pré-tratamento vêm sendo questionados devido à sua toxidade e agressividade ao meio ambiente, levando o seu uso a ser menos frequente por meio do desenvolvimento de novos processos e compostos. Alguns destes compostos estudados são os inibidores de corrosão à base de silanóis, cujo desenvolvimento e aplicação busca a baixa toxicidade, a exigência de serem ecologicamente corretos e a alta eficiência. Quando exposto em meios ácidos, o processo de corrosão para o aço galvannealed pode ser acentuado e dessa maneira, o uso de soluções aquosas de silanos organofuncionais hidrolisados em pH ácido vem sendo promissor como promotores de aderência e como inibidores de corrosão. O número de estudos publicados para o uso de silanóis adicionados diretamente no meio agressivo para a formação de filmes adsorvidos no metal protegendo-o contra a corrosão ainda é baixo, devido seu caráter inovador. Neste estudo, caracterizou-se o uso do sulfossilanol obtido a partir da hidrólise em meio ácido (pH 4,0) do silano NXT (3 - octanoiltio - 1 - propiltrietoxisilano) como inibidor de corrosão para o aço galvannealed, zinco puro e aço carbono em meio ácido (pH 5,0) de NaCl 0,1 mol L-1. Escolheu-se o zinco puro e o aço carbono para estudo pois seus átomos de zinco e ferro são constituintes da liga Fe-Zn do aço galvannealed, de maneira a se observar a adsorção do sulfossilanol em diferentes superfícies. Por meio de técnicas eletroquímicas como a técnica de varredura por eletrodo vibratório (SVET), espectroscopia de impedância eletroquímica (EIE), curvas de polarização, medida da resistência de polarização linear (Rp) foi possível verificar que o sulfossilanol estudado atua como inibidor de corrosão para o aço galvannealed, se mostrando promissor para o zinco. Através deste estudo verificou-se que o inibidor de corrosão em questão atuou principalmente na inibição das regiões ricas em zinco, já que a avaliação isolada dos metais constituintes do aço galvannealed mostrou melhores resultados para o zinco do que para o ferro. A partir disto, estudou-se por meio de técnicas eletroquímicas em meio ácido (pH 5,0) de NaCl 0,1 mol L-1, outro inibidor de corrosão clássico para aço carbono contendo também o enxofre em sua molécula, o 2 - mercaptobenzotiazol (MBT) com o intuito de comparar a eficiência da inibição da corrosão para o aço galvannealed com um inibidor clássico para ferro e o sulfossilanol, já que o aço galvannealed possui áreas ricas em ferro. O estudo evidenciou que tanto o sulfossilanol, como o MBT são bons inibidores para o aço galvannealed, sendo o sulfossilanol um excelente inibidor para zinco e o MBT um excelente inibidor para o ferro. / The process of deposition of a thin layer of zinc on carbon steel by hot immersion and subsequent heat treatment generates as product the galvannealed steel. The low cost of zinc and the easy application process leads to high consumption of this metal for carbon steel surface protection from an aggressive medium. This layer of zinc cannot be too thick because it limits the weldability, hinders the finish after painting and limits the adhesion of paints to the surface. This condition of the thin thickness of the zinc layer deposited on the carbon steel requires the development of coatings having smaller thicknesses with better hardness, ductility and higher corrosion resistance properties. Thus, the zinc surface must be pre-treated with the phosphatization and chromatization before painting. However, these pretreatments processes have been questioned because of their toxicity and aggressiveness to the environment, making their use less frequent with the development of new processes and compounds. Some of these compounds studied are silane-based corrosion inhibitors, whose development and application seek the low toxicity, the requirement of being environmentally correct and the high corrosion inhibition efficiency. When exposed in acidic media, the corrosion process for galvannealed steel can be accentuated and, in this way, the use of aqueous solutions of hydrolyzed organofunctional silanes has been promising as adhesion promoters and as corrosion inhibitors. The number of published studies for the use of sulfur silanol added directly in the aggressive medium for the formation of adsorbed films in the metal protecting it against corrosion is still low due to its novelty. In this study, the use of the sulfur silanol obtained from acid hydrolysis (pH 4.0) of NXT (3-Octanoylthio-1 propyltriethoxysilane) silane as a corrosion inhibitor for galvannealed steel, metallic zinc and carbon steel (pH 5.0) in 0.1 mol L-1 NaCl. Zinc and carbon steel were also chosen for this study because they are constituents of the Fe-Zn alloy phases present in galvannealed steel. By means of electrochemical techniques such as the scanning vibrating electrode (SVET), electrochemical impedance spectroscopy (EIS), polarization curves and linear polarization resistance (Rp) measurements, it was possible to verify that the evaluated sulfur silanol acts as a corrosion inhibitor for galvannealed steel. In this study, it was also verified that the corrosion inhibitor in question acted mainly in the inhibition of zinc rich regions or phases, since the isolated study of the constituent metals of the galvannealed steel showed better results for pure zinc than for iron. From this, it was studied by means of electrochemical techniques in acidic environment (pH 5,0) of 0,1 mol L-1 NaCl, another classic corrosion inhibitor for carbon steel also containing the sulfur in its molecule, 2 - mercaptobenzothiazole (MBT) in order to compare the corrosion inhibition efficiency for galvannealed steel with a classical inhibitor for iron and sulfur silanol, since galvannealed steel has iron rich areas. The study showed that both sulfur silanol and MBT are good inhibitors for galvannealed steel, with sulfur silanol being an excellent inhibitor for zinc and MBT being an excellent inhibitor for iron.

O processo de deposição de uma fina camada de zinco sobre o aço carbono por imersão a quente e posterior tratamento térmico gera como produto o aço galvannealed. O baixo custo do zinco e o fácil processo de aplicação faz com que o maior consumo deste metal seja aplicado na proteção da superfície do aço carbono de um meio agressivo a que ele esteja exposto. Esta camada de zinco não pode ser muito espessa, pois limita a soldabilidade, dificulta o acabamento após pintura e limita a aderência de tintas à superfície. Essa condição da fina espessura da camada de zinco depositada sobre o aço carbono torna necessário o desenvolvimento de revestimentos com espessuras menores, com melhores propriedades de dureza, ductilidade e resistência à corrosão mais elevada. Sendo assim, a superfície de zinco tem de ser pré tratada com a fosfatização e cromatização antes que as tintas possam ser devidamente aplicadas. No entanto, estes processos de pré-tratamento vêm sendo questionados devido à sua toxidade e agressividade ao meio ambiente, levando o seu uso a ser menos frequente por meio do desenvolvimento de novos processos e compostos. Alguns destes compostos estudados são os inibidores de corrosão à base de silanóis, cujo desenvolvimento e aplicação busca a baixa toxicidade, a exigência de serem ecologicamente corretos e a alta eficiência. Quando exposto em meios ácidos, o processo de corrosão para o aço galvannealed pode ser acentuado e dessa maneira, o uso de soluções aquosas de silanos organofuncionais hidrolisados em pH ácido vem sendo promissor como promotores de aderência e como inibidores de corrosão. O número de estudos publicados para o uso de silanóis adicionados diretamente no meio agressivo para a formação de filmes adsorvidos no metal protegendo-o contra a corrosão ainda é baixo, devido seu caráter inovador. Neste estudo, caracterizou-se o uso do sulfossilanol obtido a partir da hidrólise em meio ácido (pH 4,0) do silano NXT (3 - octanoiltio - 1 - propiltrietoxisilano) como inibidor de corrosão para o aço galvannealed, zinco puro e aço carbono em meio ácido (pH 5,0) de NaCl 0,1 mol L-1. Escolheu-se o zinco puro e o aço carbono para estudo pois seus átomos de zinco e ferro são constituintes da liga Fe-Zn do aço galvannealed, de maneira a se observar a adsorção do sulfossilanol em diferentes superfícies. Por meio de técnicas eletroquímicas como a técnica de varredura por eletrodo vibratório (SVET), espectroscopia de impedância eletroquímica (EIE), curvas de polarização, medida da resistência de polarização linear (Rp) foi possível verificar que o sulfossilanol estudado atua como inibidor de corrosão para o aço galvannealed, se mostrando promissor para o zinco. Através deste estudo verificou-se que o inibidor de corrosão em questão atuou principalmente na inibição das regiões ricas em zinco, já que a avaliação isolada dos metais constituintes do aço galvannealed mostrou melhores resultados para o zinco do que para o ferro. A partir disto, estudou-se por meio de técnicas eletroquímicas em meio ácido (pH 5,0) de NaCl 0,1 mol L-1, outro inibidor de corrosão clássico para aço carbono contendo também o enxofre em sua molécula, o 2 - mercaptobenzotiazol (MBT) com o intuito de comparar a eficiência da inibição da corrosão para o aço galvannealed com um inibidor clássico para ferro e o sulfossilanol, já que o aço galvannealed possui áreas ricas em ferro. O estudo evidenciou que tanto o sulfossilanol, como o MBT são bons inibidores para o aço galvannealed, sendo o sulfossilanol um excelente inibidor para zinco e o MBT um excelente inibidor para o ferro. / The process of deposition of a thin layer of zinc on carbon steel by hot immersion and subsequent heat treatment generates as product the galvannealed steel. The low cost of zinc and the easy application process leads to high consumption of this metal for carbon steel surface protection from an aggressive medium. This layer of zinc cannot be too thick because it limits the weldability, hinders the finish after painting and limits the adhesion of paints to the surface. This condition of the thin thickness of the zinc layer deposited on the carbon steel requires the development of coatings having smaller thicknesses with better hardness, ductility and higher corrosion resistance properties. Thus, the zinc surface must be pre-treated with the phosphatization and chromatization before painting. However, these pretreatments processes have been questioned because of their toxicity and aggressiveness to the environment, making their use less frequent with the development of new processes and compounds. Some of these compounds studied are silane-based corrosion inhibitors, whose development and application seek the low toxicity, the requirement of being environmentally correct and the high corrosion inhibition efficiency. When exposed in acidic media, the corrosion process for galvannealed steel can be accentuated and, in this way, the use of aqueous solutions of hydrolyzed organofunctional silanes has been promising as adhesion promoters and as corrosion inhibitors. The number of published studies for the use of sulfur silanol added directly in the aggressive medium for the formation of adsorbed films in the metal protecting it against corrosion is still low due to its novelty. In this study, the use of the sulfur silanol obtained from acid hydrolysis (pH 4.0) of NXT (3-Octanoylthio-1 propyltriethoxysilane) silane as a corrosion inhibitor for galvannealed steel, metallic zinc and carbon steel (pH 5.0) in 0.1 mol L-1 NaCl. Zinc and carbon steel were also chosen for this study because they are constituents of the Fe-Zn alloy phases present in galvannealed steel. By means of electrochemical techniques such as the scanning vibrating electrode (SVET), electrochemical impedance spectroscopy (EIS), polarization curves and linear polarization resistance (Rp) measurements, it was possible to verify that the evaluated sulfur silanol acts as a corrosion inhibitor for galvannealed steel. In this study, it was also verified that the corrosion inhibitor in question acted mainly in the inhibition of zinc rich regions or phases, since the isolated study of the constituent metals of the galvannealed steel showed better results for pure zinc than for iron. From this, it was studied by means of electrochemical techniques in acidic environment (pH 5,0) of 0,1 mol L-1 NaCl, another classic corrosion inhibitor for carbon steel also containing the sulfur in its molecule, 2 - mercaptobenzothiazole (MBT) in order to compare the corrosion inhibition efficiency for galvannealed steel with a classical inhibitor for iron and sulfur silanol, since galvannealed steel has iron rich areas. The study showed that both sulfur silanol and MBT are good inhibitors for galvannealed steel, with sulfur silanol being an excellent inhibitor for zinc and MBT being an excellent inhibitor for iron.

This thesis is focused on theoretical study of influence of the silanol nest defects on the hydrolysis of zeolite Chabazite under harsh steaming conditions. The motivation of the thesis was a recent experiment proving that the silanol nest defect enhances the hydrolysis of a zeolite. The harsh steaming conditions have been chosen as some important technological processes involving zeolites require high temperatures and have water vapour present. The study was performed by using density functional theory calculations. To investigate the influence of the defect two models were used a reference pristine model and a defected model containing the silanol nest defect. The two models were pure siliceous Chabazite periodical models with supercell containing 36 and 35 Si tetrahedra respectively. A multi-step hydrolysis leading to detachment of a Si(OH)4 cluster from the zeolite, known as total desilication, was calculated for the two models. Multiple possible paths of the hydrolysis were discovered, compared and discussed on both models. Both the most favourable hydrolysis paths of the two model as well as their arithmetic means were compared. The experimentally set expectations that a silanol nest defect enhances the hydrolysis of the zeolite have been met.

L’influence de paramètres de synthèse et de traitements post-synthèse sur le caractère hydrophobe/hydrophile de silices mésoporeuses organisées (SMO) de type SBA-15 a été étudiée. Ainsi nous avons montré que la durée du mûrissement peut être réduite à la durée nécessaire à la précipitation. La température, l’agitation et la durée de synthèse modulent la morphologie des particules et des agrégats. Le mode de chauffage, la présence d’un sel inorganique et le rapport silice/tensioactif ont un effet sur la structure et la texture du matériau. Concernant les traitements post-synthèse, nous avons considéré l’élimination de l’agent structurant et la fonctionnalisation par greffage. Le taux de silanols diminue suite au vieillissement mais surtout après calcination : cette étape efface les différences en termes de teneur en silanols. C’est la raison pour laquelle une nouvelle méthode d’élimination du tensioactif efficace (dès 300 °C) et rapide (dès 15 min) a été mise en œuvre : la calcination à l’aide d’un four à induction conduit à un matériau avec des propriétés structurales, texturales et une teneur en silanols supérieures à celles d’une SMO de type SBA-15 calcinée par la méthode conventionnelle. La calcination par induction a également été appliquée avec succès sur différents types de SMO telles que la SBA-16 et la MCM-41. Ensuite, l’influence des caractéristiques initiales de la SMO sur la fonctionnalisation par un greffage post-synthèse a été étudiée. Une SMO de type SBA-15 plus hydrophobe a été obtenue avec un greffon possédant une seule fonction condensable. La teneur initiale et probablement l’accessibilité des silanols ont un impact significatif sur le taux de greffage. / The influence of synthesis parameters and post-synthesis treatments on the hydrophobic/hydrophilic character of SBA-15 type ordered mesoporous silicas (OMS) was studied. It was found that the duration of ripening can be reduced to the precipitation time. Temperature, stirring and duration of synthesis steps can modulate the morphology of particles and aggregates. Heating process, presence of an inorganic salt and silica/surfactant ratio are also parameters that affect the structure and texture of the material. Concerning post-synthesis treatments, the elimination of the template and the functionalization by grafting were considered. The rate of silanols decreases during aging but mostly after calcination: this step erases the differences in silanol content. This is why a new method for an effective (at 300 ° C) and fast (for 15 min) removal of the surfactant has been implemented: the calcination using an induction furnace leads to a material with structural, textural properties and silanol content greater than those of a SBA-15 material calcined by the conventional method. The calcination induction has also been successfully applied on different types of OMS such as SBA-16 and MCM-41. Then, the influence of the OMS characteristics on functionalization by post-synthesis grafting was studied. The more hydrophobic SBA-15 material was obtained with a grafting agent possessing a single condensable function. It was also observed that the initial content and the accessibility of silanols probably have a significant impact on the grafting rate.

Orientador: Carol Hollingworth Collins / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-18T09:08:43Z (GMT). No. of bitstreams: 1 Souza_EndlerMarcelBorgesde_D.pdf: 24501631 bytes, checksum: 4fd1866c1e1f40857962b738d98e6eb5 (MD5) Previous issue date: 2011 / Resumo: As propriedades cromatográficas e a estabilidade de fases estacionárias preparadas pela imobilização térmica do poli(metiloctilsiloxano) ou do poli(metiltetradecilsiloxano) sobre a sílica foram avaliadas. Para isso, fora empregados os testes de Engelhardt, Tanaka e SRM 870. O estudo dos mecanismos envolvidos na retenção de solutos básicos nestas fases estacionárias foi feita com um teste desenvolvido em nosso laboratório, que consiste em avaliar os fatores de retenção e a assimetria de solutos hidrofóbicas e hidrofílicas em fases móveis com diferentes valores de pH, preparadas com diferentes tipos e concentrações de tampão. A avaliação das fases estacionárias com os testes SRM 870 e de Tanaka mostram uma alta contribuição dos fenômenos de troca iônica para retenção dos solutos básicos e a comparação dos valores obtidos com o teste de Tanaka, segundo o modelo de Euerby, mostrou que estas fases estacionárias apresentam propriedades cromatográficas distintas da maioria das fases comerciais, embora alguma similaridade tenha sido observada com as fases estacionárias que também apresentam altas contribuições de fenômenos de troca iônica na retenção de solutos básicos. O novo teste desenvolvido mostrou que a retenção de solutos básicos acontece devido a interações sinérgicas dos silanóis residuais com os polisiloxanos imobilizados na forma de gotas sobre a sílica. Devido a estas interações, o pH da fase móvel, o tipo e a concentração de tampão afetam intensamente os fatores de retenção e a assimetria de solutos básicos. Algumas das fases estacionárias apresentaram boa seletividade e picos simétricos para solutos básicos em fases móveis neutras, onde os solutos estam protonados e os silanóis residuais estão desprotonados. Os testes de estabilidade demonstraram que algumas das fases estacionárias são altamente estáveis em fases móveis neutras em temperatura ambiente e em fases móveis ácidas, mesmo a altas temperaturas. No entanto, estas se mostraram instáveis em fases móveis alcalinas mesmo em temperatura ambiente, conforme esperado para fases estacionárias preparadas pela imobilização de polissiloxanos sobre a sílica / Abstract: This work has evaluated the chromatographic properties and the stability of stationary phases prepared by with poly(methyloctylsiloxane) or poly(methyltetradecylsiloxane) thermally immobilized onto a silica surface. The stationary phases were chromatographically evaluated using the Engelhardt, SRM 870 and Tanaka tests. The retention mechanisms involved during the separation of basic solutes with these stationary phases were evaluated using a test developed in our laboratory that evaluates the effect of the mobile phases with different pH, and type and concentration of buffer on the retention factors and asymmetry of several basic solutes (with hydrophobic or hydrophilic characteristics). Evaluations with the SRM 870 and Tanaka tests showed that there is a high contribution of ionexchange interactions at neutral pH. Classifications using the Euerby¿s procedure indicate that the stationary phases developed in this work are different from most commercial ones, although some similarity was found with the phases that have high ion-exchange interactions. Also, the retention of basic solutes occurs due to synergetic interactions between the free silanols with the immobilized polysiloxanes, which are in the form of plugs on the silica surface. Due to these interactions the pH of the mobile phase, and the type and concentration of buffer have a strong effect on the retention factors and asymmetry factors of basic solutes. The stationary phases present good selectivity at near neutral pH, where both the basic solutes and free silanols are protonated, suggesting the use of intermediate pH for basic solute analyses. Stability tests show that the stationary phases have high stability in neutral mobile phases at room temperature and also in acidic mobile phases, even at high temperatures. However, these phases have low stability in alkaline mobile phases, even at room temperature, which was expected for polysiloxanes immobilized onto silica / Doutorado / Quimica Analitica / Doutor em Ciências