Organically modified sol-gel coatings have been investigated as potential replacements for chromate conversion coating of AA1050 and AA2024 aluminium alloys. The coatings were prepared by a combination of a completely hydrolysable precursor of tetra-n-propoxyzirconium (TPOZ), with a partially hydrolysable precursor of glycidoxypropyltrimethoxysilane (GPTMS). GPTMS contains organic functional groups, which are retained in the sol-gel coatings after the hydrolysis-condensation process. Different process parameters, e.g. GPTMS/TPOZ ratios, withdrawal speeds, solvent water concentrations, and curing temperatures were studied. Coatings produced using a low GPTMS/TPOZ ratio and a high withdrawal speed generated significant cracks due to the shrinkage of the coatings. It was found that increase of organic moieties reduced the shrinkage of the coatings and the tendency for crack formation. By controlling process parameters and ratios of organic and inorganic moieties, crack-free sol-gel coatings from 0.1 μm to 9 μm thick can be achieved. The sol-gel coatings formed are amorphous and contain organic epoxy-ether retained silicon oxide, silicon hydroxide, zirconium oxide, zirconium hydroxide, and zirconium acetate. The Si/Zr ratios of resultant sol-gel coatings are proportional to the initial GPTMS/TPOZ ratio. Cerium oxide nanoparticles were successfully incorporated into sol-gel coatings with a single layer and double layer sol-gel process. Through the dip coating process, crack-free sol-gel coatings, of varied thickness, were developed on different aluminium substrate, including electropolished superpure aluminium, magnetron sputtered aluminium with varied copper contents from 0 to 30 wt.%, and commercial AA1050 and 2024 aluminium alloys. Sol-gel coatings formed on commercial AA1050 and 2024 aluminium alloys revealed a significant passivation in 3.5 wt.% sodium chloride solution during anodic polarisation when the sol-gel coating is more than 1 µm thick and proper surface pretreatments of the alloys were used. Corrosion tests by immersion in 3.5 wt% sodium chloride solution and by salt spray in 5 wt.% sodium chloride solution revealed that sol-gel coatings successfully protected AA2024 aluminium alloy against the aggressive environment and have the potential to replace chromate containing coating systems.

Des revêtements sol-gel nanocomposites TiO2-SiO2 ont été réalisés à partir de mélanges d'une suspension nanocristalline de TiO2 anatase et de sols polymériques de silice. Ces revêtements présentent une superhydrophilie naturelle, persistante et photo-régénérable. La présence de charges localisées aux interfaces granulaires TiO2-SiO2 est une des hypothèses permettant d'expliquer cette superhydrophilie naturelle. Toutefois des effets de morphologie (rugosité, porosité de surface) sont également connus pour influencer le mouillage. Des études ont été menées pour mettre directement en évidence l'effet intrinsèque des interfaces granulaires. Les études se sont recentrées sur l'effet extrinsèque de paramètres morphologiques susceptibles d'influencer la mouillabilité des revêtements nanocomposites selon des modèles thermodynamiques des surfaces connus. De nouveaux protocoles de synthèse par voie sol-gel ont été mis au point afin d'analyser i/ en quoi la superhydrophilie naturelle et photo-induite des revêtements TiO2-SiO2 pouvait être influencée par des effets de morphologie et de composition, et ii/ en quoi une exacerbation de ces effets via des structurations artificielles pouvaient encore accroître la superhydrophile de surface. Une extrapolation de ces protocoles a également permis d'étudier des revêtements superhydrophobes. / Sol-gel TiO2-SiO2 nanocomposites coatings have been deposited from a suspension of anatase TiO2 nanocristallites mixed with different polymeric silica sols. These coatings show a natural and persistent superhydrophilicity, which can also be photo-regenerated. This outstanding property can probably be explained by electrical charges localized at TiO2-SiO2 granular interfaces. Yet, some morphological features (roughness, surface porosity) may also influence wetting properties. Studies have firstly been carried out to directly evidence the intrinsic effect of those electrical charges. The studies have then been focused on the extrinsic effect of morphological parameters than can influence the composite wettability, according to thermodynamic models. New sol-gel protocols were carried out to better understand in which extent i/ the natural and photo-induced wetting properties of composite coatings may be influenced by composition and morphological features, and ii/ artificial structuration of the coating surface may enhance their superhydrophilicity. Those structuration protocols have been extrapolated to the study of superhydrophobic coatings.

Three ionic liquids (ILs), trihexyltetradecylphosphonium tetrafluoroborate (TTPT), N-butyl-4-methylpyridinium tetrafluoroborate (BMPT), and 1-methyl-3- octylimidazolium tetrafluoroborate (MOIC), were utilized to prepare sol- gel sorbent coatings. Non-polar polydimethylsiloxane (PDMS) and polar poly(ethylene glycol) (PEG), poly(tetrahydrofuran) (PolyTHF) and bis[(3-methyldimethoxy-silyl)propyl] polypropylene oxide (BMPO) polymers were employed to develop novel ionic liquidmediated sol- gel hybrid organic- inorganic sorbents. The novel sorbents were first tested as coatings for capillary microextraction off-line hyphenated to gas chromatography. To gain an understanding of the role of the ionic liquids in the sol-gel process, the preconcentration abilities of these novel coatings were investigated for several classes of compounds utilizing CME-GC. This was accomplished by comparing GC peak areas of a series of analytes extracted on the ionic liquid mediated sol-gel CME coatings with that of analogous peak areas obtained on sol- gel coatings prepared without the ionic liquid. The morphology of these coatings was compared using scanning electron microscopy (SEM) imaging data. Overall, the ionic liquid-mediated sol- gel coatings had more porous morphologies than the sol-gel coatings prepared without ionic liquid. The PDMS andBMPO sol-gel coatings prepared with ionic liquid in the sol solution provided enhanced extraction sensitivity reflected in higher preconcentration effects and lower detection limits than the sol- gel coatings prepared without the ionic liquid. The polar IL-mediated BMPO sol- gel sorbent was further investigated by exploring the extraction profile and thermal stability of these coatings. A further application of ionic liquid-mediated sol-gel sorbents could be as stationary phases in a microchip-based separation system. Towards this goal, microfluidic channels were fabricated in glass substrates using microelectromechanical engineering. Spiral and serpentine channels were etched in Pyrex and fused silica wafers using wet and deep reactive ion etching (DRIE) techniques. Microfabrication protocols such as the use of hard mask and etching times were investigated for both techniques. DRIE produced microfluidic channels that had an etch quality that was superior to wet etched channels. Thus, the ultimate microchip-based separation system should by fabricated using DRIE.