In this work, an eco-friendly sol-gel synthesis of pure and doped TiO2, previously developed at lab-scale, is applied in three different environmental applications at lab-scale and then, upscaled towards industrial applications. For each application, the TiO2 is used as a coating deposited mainly on steel substrates. The three applications are: (i) the development of a photocatalytic reactor made of a UV lamp, an ozonation part and a TiO2 photocatalytic coating to treat water from swimming pools, (ii) the development of a new generation of low energy sterilizers by an advanced oxidation process using a photocatalytic coating illuminated by a blue LED, and (iii) an easy-to-clean coating for outdoor steel. In each application, the up-scale results were similar to those obtained in the laboratory with respect to the crystallinity, the visual aspect, the hydrophilicity, and the photocatalytic properties of the produced coatings. These developments showed the possibility to bring sol-gel TiO2 products outside the laboratory towards pilot and industrial applications, and opens the way for many possible up-scaled sol-gel based environmental applications.

The sol–gel coating method is considered to be simple and easy to implement to lead to organic/inorganic hybrid coatings. In addition, the application of thin films by this technique is inexpensive and applicable on large substrates without form restriction. In this context, thin sol–gel coatings based on a mixture of three alkoxysilanes and synthesized in purely aqueous phase with different thicknesses and with the presence or not of ZrO2 nanoparticles, were applied on metallic and glass substrates. After application and curing, the mechanical properties of sol–gel coatings were characterized by Berkovich nanoindentation with continuous stiffness measurement mode (CSM). The effective elastic moduli as well as the hardness values were estimated for each coating along the indentation depth and as a function of the substrate material and sol–gel characteristics. The effect of a annealing at higher temperature was also studied. Then, the failure modes of sol–gel coatings were investigated using both Berkovich nanoindentation and nanoscratch technique with a 5 µm radius spherical diamond tip. Careful microscopic observations of residual imprints and residual grooves both exhibit chipping in case of thick coating especially on glass substrate and no dramatic failure for thin coating applied on both substrates. It is shown in this work that the mechanical properties of the sol–gel and the mechanical stability of coatings on substrates are influenced dramatically by the presence of nanoparticles and the thermal treatment. Finally, interfacial fracture toughness of sol–gel coatings on substrate was estimated using analytical model from the literature and Ashby map based on experimental results was created using performance indices in order to proceed to sol–gel coating selection.

A generic mechanical framework has been developed for assessing the indentation and scratch resistance of hard films on soft substrates. Analytical expressions for the critical loads leading to film cracking or substrate yielding are proposed based on closed form plate bending models and on finite element simulations. These models lead to the definition of performance indices for the ranking of “hard-film-on-soft-substrate” systems with respect to the resistance to indentation and scratch failure under the constraint of minimizing film thickness. These performance indices show that the hardest coating is not always the best choice and that other material properties of the film and the substrate have to be taken into account. An illustrative material property chart is proposed in order to compare the protective ability of some usual thin coatings. These results constitute a guide for the development of layered systems in order to avoid time consuming and expensive trial and error campaigns.

In this work, a pure TiO2 colloid was produced at pilot scale of 5 L and deposited on stainless steel with a pilot roll-to-roll line to produce photocatalytic coating for VOC degradation. The pure TiO2 colloid was synthesized with an aqueous sol–gel process, producing crystalline nanoparticles around 4–5 nm (mainly anatase phase) dispersed in water. The crystalline phases were produced at low temperature (<100 ℃) without calcination step. The crystalline coating produced with roll-to-roll process was very thin, around 50 nm. The photoactivity of this coating towards VOC destruction was evaluated on the degradation of acetaldehyde; the measured activity of the coating was 35 ± 5%. With the use of mass spectrometer, it was shown that acetaldehyde was mainly converted in CO2. The durability of the coating was assessed after 1, 2 and 3 weeks, and showed that the photoactivity stayed constant for this period.

A process has been developed to enable the large-scale production of pure TiO2 films deposited on 316L stainless steel in order to get an easy-to-clean surface. This large-scale process requires an easy aqueous sol–gel procedure for the synthesis of the TiO2 sol. This synthesis has been simplified to facilitate the extrapolation toward an industrial scale. Results of TEM, photocatalytic properties, film hydrophilicity and texture obtained with the simplified aqueous sol–gel synthesis (IsoP–TiO2 synthesis) show similar properties to those obtained with the standard aqueous sol–gel synthesis of TiO2 (HAc–TiO2 synthesis) developed previously. Only, X-ray diffraction patterns showed differences, with the presence of anatase-brookite phases in IsoP–TiO2 synthesis while anatase phase only was observed in HAc–TiO2 synthesis. Both the aqueous sol–gel synthesis of pure TiO2 and the film deposition on steel by roll-coating have been successfully extrapolated to a larger scale. The photocatalytic activity and the hydrophilicity of the film were found to be unchanged when compared to films produced at a laboratory scale, thus validating the production of an efficient easy-to-clean material. Although some problems are still to be solved, this study is a hopeful first step in the development of a large-scale process for self-cleaning steel production.

Low pressure thin film deposition processes such as magnetron sputtering involve different physical mechanisms acting on vastly different time and length scales. The global process kinetics of the reactor and spatial distributions of film thickness and film stoichiometry can be usually described within particle based or continuous models of gas and precursor transport and plasma discharge [1]. In contrast, predicting the intrinsic properties of the growing film such as crystalline phase composition, morphology etc. requires to apply computational material modelling on atomistic scale. For realistic predictions of the film structure by atomistic modelling it is crucial to provide realistic input data in terms of particle fluxes, as well as their energy and angular distribution functions. By setting up a multi-scale simulation chain it is possible to feed the output of reactor scale simulation into atomistic models [2]. Using this multi-scale approach we present atomistic computations of intrinsic TiO2 films grown by reactive magnetron sputtering. Molecular Dynamics [2] and kinetic Monte Carlo method [3] are applied with initial conditions obtained from different process conditions by particle-based reactor scale modelling. The results are compared with scanning electron and atomic force microscopy of the film morphology and surface texture.

Thin films of titanium oxide (TiO2) are synthesized at room temperature by the post-discharge of an RF atmospheric plasma torch supplied with argon and oxygen. Vapours of titanium tetraisopropoxide (TTIP) precursor are injected in the post-discharge by an argon flow rate bubbling in the liquid precursor. Without any external substrate heating, the coatings are amorphous and characterized by a thin film upon which agglomerates can be observed. The annealing of the coatings at 450°C is efficient to (partially) crystallize the TiO2 since bands characteristic of the TiO2 anatase structure are observed in Raman spectra. The films are super-hydrophilic and present excellent photocatalytic activity; two properties of particular interest for self-cleaning applications. Nevertheless, annealed coating presents a higher photocatalytic activity.

Simulation of the coating process is a very promising approach for the understanding of thin film formation. Nevertheless, this complex matter cannot be covered by a single simulation technique. To consider all mechanisms and processes influencing the optical properties of the growing thin films, various common theoretical methods have been combined to a multi-scale model approach. The simulation techniques have been selected in order to describe all processes in the coating chamber, especially the various mechanisms of thin film growth, and to enable the analysis of the resulting structural as well as optical and electronic layer properties. All methods are merged with adapted communication interfaces to achieve optimum compatibility of the different approaches and to generate physically meaningful results. The present contribution offers an approach for the full simulation of an Ion Beam Sputtering (IBS) coating process combining direct simulation Monte Carlo, classical molecular dynamics, kinetic Monte Carlo, and density functional theory. The simulation is performed exemplary for an existing IBS-coating plant to achieve a validation of the developed multi-scale approach. Finally, the modeled results are compared to experimental data.

A low frequency plasma process is used to deposit thin films on steel through simultaneous sputtering and plasma enhanced chemical vapour deposition (PECVD). The deposited material consists in composite copper-organosilicon thin layers where copper is obtained by magnetron sputtering whereas the organosilicon plasma polymer is grown by PECVD from HMDSO (hexamethyldisiloxane).This paper focuses on the important process parameters required to control the quantity of incorporated copper in the layer, particularly the metalorganic concentration and the sputtering current. The dispersion of copper vs. the thin film thickness is found to be homogeneous. The deposited layers show antimicrobial activity for copper contents higher than X = 38%, where X = [Cu]/([Cu] + [Si]). (C) 2009 Elsevier B. V. All rights reserved.

After reviewing most of the recent developments performed on hybrid processes, basic physical phenomena of PVD-PECVD processes are detailed with the help of a model showing the different influences of main process parameters. Ti-Si-O and Zn-Si-O thin films are synthesized as possible examples of composite thin films. Limitations of the model developed are also discussed with respect to the composition and structure of deposited thin films.

Zn-Si-O composite thin films are synthesised in a hybrid process where radiofrequency (RF) sputtering and plasma enhanced chemical vapour deposition (PECVD) occur simultaneously. A zinc target is sputtered in a gas mixture containing hexamethyldisiloxane (HMDSO-Si2C6H18O). With this process, any composition of the deposited layer can be obtained from zinc oxide to silica by simply controlling the flow rate of HMDSO in the reactor. The structure, composition and deposition rate of the layers depend on the gas mixture, the target-to-substrate distance and the HMDSO flow rate. Composite thin films containing a few percents of silicon show a dense morphology compared with the columnar zinc oxide layers.

A radio frequency hybrid process where sputtering and plasma enhanced chemical vapour deposition (PECVD) occur simultaneously is studied to describe the specificity it gains when the two techniques are merged. A model is developed to describe how the deposition rate evolves when the flow rate of the PECVD precursor increases. First, it is shown that it is constant below a critical value of the precursor flow rate because of the wind effect due to sputtering that strongly limits the transport of the precursor. Then it increases almost linearly with the precursor flow rate when PECVD and sputtering simultaneously occur. Finally, above a certain threshold in the precursor flow rate, the surface of the target is poisoned by the precursor and composite thin films can no longer grow. The previous model is deduced from results obtained in deposition of Zn–Si–O and Ti–Si–O thin films. These composites are synthesised respectively by sputtering of zinc and titanium targets in a vapour of oxygen and hexamethyldisiloxane (HMDSO–Si2C6H18O). Limitations of the model used are also discussed.

Ce travail s’interesse a la synthese de films minces composites Zn-Si-O et Ti-Si-O a l’aide d’un procede hybride combinant le depot de silice par PECVD (Plasma Enhanced Chemical Vapour Deposition) a partir du precurseur organometallique hexamethyldisiloxane (HMDSO-Si2C6H180), et la pulverisation reactive de zinc ou de titane. L’elaboration de revetements dont la composition s’echelonne d’un oxyde metallique ZnOx ou TiOx a la silice est rendue possible en agissant sur le debit du precurseur. L’ajout de silicium dans le revetement fait evoluer sa morphologie de colonnaire a dense. De plus un phenomene de competition entre les composantes PECVD et pulverisation du procede est mis en evidence. Ainsi la mesure des vitesses de depot en fonction du debit d’HMDSO permet de determiner les valeurs de debits critiques de precurseurs a partir desquelles le depot de silice par PECVD est initie, et pour lesquelles le recouvrement de la cible par le depot de silice se produit. Les caracterisations des revetements montrent que ceux-ci sont constitues, dans une zone proche de l’interface avec l’acier d’un melange d’oxydes non stoechiometriques qui differe de maniere importante d’un melange ZnO+SiO2 ou TiO2+SiO2. Pour les revetements de type Ti-Si-O le titane est en exces dans la zone proche de l’interface tandis que dans les revetements de type Zn-Si-O le silicium est en exces. On observe alors une decroissance progressive de la concentration atomique respectivement de titane et de silicium lorsqu’on approche de la surface du revetement. Ces evolutions peuvent etre reliees a un effet de l’augmentation de la temperature dans la premiere phase de l’elaboration, qui agit sur la cinetique de depot par PECVD et conditionne l’etat de contamination de la cible