Stable hydrosols for TiO2 coatings

The optimum processing parameters required to synthesize, by hydrolysis of titanium isopropoxide (TIP), highly stable hydrosols composed of nanoparticles of the smallest possible size, are deduced both from data available in literature and from our own experiments. The colloids prepared in these conditions are composed of aggregates of anatase (*90%) and brookite crystallites (5–6 nm). They are suitable for coatings and have longterm stability (more than one year) in terms of polymorphic composition, crystallite and agglomerate size. Stable sols composed solely of anatase crystallites (4 nm) can be prepared by partially complexing the TIP by acetylacetone before hydrolysis. It is not possible to produce porous films with these colloids because they are stabilized by electrostatic repulsion which causes the particles to organize themselves, during the drying step, to form materials with a close packed structure. However, coatings with controlled porosity can be prepared from these stable sols through the post addition of polymers, like PEG or block copolymers

Multilayer chromium based coatings grown by atmospheric pressure direct liquid injection CVD

There is a great interest for multilayer hard coatings because they exhibit enhanced properties resulting from their nanostructuration. Such coatings are frequently constituted of carbide and nitride and are generally deposited under very low pressure by plasma and PVD processes. These vacuum techniques enable the growth of heterostructures with nanometric thick individual layers and sharp interfaces, which are two requirements for advanced performances. However, both to develop more economical processes and with the goal of continuous deposition applications, the CVD processes operating under atmospheric pressure are particularly attractive. In this paper we show that the combination of pulsed direct liquid injection and the use of metalorganic precursor (DLI-MOCVD) is a promising route for the growth of nanostructured multilayer coatings under atmospheric pressure. Chromium metal as well as chromium carbide and nitrides monolithic coatings have been deposited at 773 K by this process using liquid solution of bis(benzene) chromium as Cr molecular precursor. Then, CrCx/CrN nanostructured multilayer coatings with a bilayer period as low as 50 nm have been grown. Structural characterizations and preliminary mechanical properties of these metallurgical coatings are discussed

Nanocomposite thin film of Ag nanoparticles embedded in amorphous Al 2 O 3 on optical sensors windows: Synthesis, characterization and targeted application towards transparency and anti-biofouling

Increased motivation for environmental monitoring requires robust and reliable sensors. The present work aims at increasing the service time of optical sensors immersed in riverine waters by decreasing the development of biofouling on their surface. In this aim, nanocomposite coatings composed of metallic silver nanoparticles embedded in an amorphous alumina are co-deposited on sensor glass windows by chemical vapor deposition. Immersion for one week in the Saulx river, France, revealed a threefold decrease of biofouling on their surface compared with untreated glass surfaces while maintaining transparency. Such coatings can be considered as part of integrated tools, including for example mechanical cleaning, to reduce the maintenance of optical sensors immerged in riverine waters

Low voltage plasma jet with piezoelectric generator : preliminary evaluation of decontamination capabilities

This paper deals with the proof of concept and the preliminary evaluation of decontamination performances obtained with a plasma jet generated by a piezoelectric transformer. This low voltage supply solution (<10V) is investigated as a plasma jet device, compact and safe solution for the decontamination of medical thermo-sensitive devices. The principle of the piezoelectric generator is presented, followed by the optical spectroscopy of the plasma jet, the protocol conditions for the bactericidal effect observations and finally the reduction rates obtained on Pseudomonas aeruginosa and Staphylococcus aureus bacteria strains with an argon plasma jet at atmospheric pressure about 2.5W electrical input power

Development of Polythiourethane/ZnO-Based Anti-Fouling Materials and Evaluation of the Adhesion of Staphylococcus aureus and Candida glabrata Using Single-Cell Force Spectroscopy

The attachment of bacteria and other microbes to natural and artificial surfaces leads to the development of biofilms, which can further cause nosocomial infections. Thus, an important field of research is the development of new materials capable of preventing the initial adhesion of pathogenic microorganisms. In this work, novel polymer/particle composite materials, based on a polythiourethane (PTU) matrix and either spherical (s-ZnO) or tetrapodal (t-ZnO) shaped ZnO fillers, were developed and characterized with respect to their mechanical, chemical and surface properties. To then evaluate their potential as anti-fouling surfaces, the adhesion of two different pathogenic microorganism species, Staphylococcus aureus and Candida glabrata, was studied using atomic force microscopy (AFM). Our results show that the adhesion of both S. aureus and C. glabrata to PTU and PTU/ZnO is decreased compared to a model surface polydimethylsiloxane (PDMS). It was furthermore found that the amount of both s-ZnO and t-ZnO filler had a direct influence on the adhesion of S. aureus, as increasing amounts of ZnO particles resulted in reduced adhesion of the cells. For both microorganisms, material composites with 5 wt.% of t-ZnO particles showed the greatest potential for anti-fouling with significantly decreased adhesion of cells. Altogether, both pathogens exhibit a reduced capacity to adhere to the newly developed nanomaterials used in this study, thus showing their potential for bio-medical applications

Torche plasma micro-onde à la pression atmosphérique (application au traitement de surfaces métalliques)

Ce manuscrit est consacré à l étude d une torche plasma micro-onde fonctionnant à la pression atmosphérique pour la préparation de surfaces métalliques, plus particulièrement le dégraissage et l oxydation de surface d alliage aluminium Al2024 avant revêtement peinture d une part et le décapage de TA6V avant soudage d autre part. Des conditions optimales de fonctionnement sont dégagées grâce à une étude du comportement du plasma par spectroscopie d émission optique et modélisation électromagnétique : le plasma généré par la torche est un gaz ionisant de température électronique Te = 7500 K et dont la densité d espèces actives est favorisée par une puissance micro-onde l ordre de 600 W, un débit de gaz plasmagène élevé et un positionnement proche de la base du jet. L application de la torche aux cas particuliers du dégraissage et de l oxydation de surface sont ensuite étudiés en terme d énergie de surface et de profil de composition chimique en profondeur. Les résultats sont encourageants puisque le traitement plasma permet d améliorer l énergie de surface (elle passe de 32 mN/m à 72 mN/m) et de doubler l épaisseur de la couche d oxyde natif.This project is aimed at applying an atmospheric pressure microwave plasma torch to the treatment of metallic substrates. More precisely the applications are, on one hand, the oil removal from Al2024 samples and their surface oxidation before painting and on the other hand, cleaning TA6V substrates before welding. First of all optimal working conditions are defined thanks to investigations about the plasma behaviour by optical emission spectroscopy and electromagnetic calculations. This study puts the light on the fact that the plasma is ionizing, its electronic temperature is about 16500 K and the density of active species is favoured by a 600 W feeding power, a high plasma gas flow rate and a substrate location as close to the basis of the plasma jet as possible. The torch is quite efficient to remove oil from substrates and oxidise them in so far as the surface energy is improved (it increases from de 32 mN/m to 72 mN/m) and the native oxide layer thickness is doubled.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

Excited states dipole polarizabilities of calcium atom and long-range dispersion coefficients for the low-lying electronic states of Ca2 and CaMg

International audienceno abstrac

Relation entre la structure et les propriétés fonctionnelles des revêtements de TiO2 sur les substrats métalliques

L'objectif de cette étude était de réaliser des revêtements de TiO2 présentant une large variété de morphologies et d'établir des corrélations entre la structure de ces couches et leurs propriétés fonctionnelles, notamment la photocatalyse. Deux voies de synthèse employant le même précurseur, le tétra-isopropropoxide (TTIP) de titane, ont été utilisées, le procédé sol-gel et le dépôt chimique en phase vapeur (MOCVD). L'emploi de ces deux techniques permet de produire TiO2 sous une large gamme de morphologies mais avec des variétés polymorphiques similaires. Les revêtements synthétisés ont été caractérises afin de déterminer leur composition polymorphique, la taille des cristallites, la surface spécifique, la rugosité et l'épaisseur. Puis leur activité photocalytique pour la dégradation du bleu de méthylène a été déterminée. Par voie sol-gel, des dispersions de nano-cristallites de TiO2 dans l'eau, stables sur une longue durée (plus d'un an) en termes de composition polymorphique, taille d'agglomérats et de cristallites ont été synthétisées. Les revêtements ont été réalisés par tape-casting et dip-coating. Pour la synthèse en MOCVD, un plan d'expérience (PeX) a été utilisé, à notre connaissance pour la première fois. Il a permis de déterminer, d'une manière efficace et économique (avec un nombre minimum de tests expérimentaux), les paramètres les plus importants du procédé contrôlant les diverses propriétés quantifiables du revêtement. Il a aussi permis de mettre en évidence les interactions entre les paramètres de synthèse et leur effet sur la structure du revêtement. Les conclusions tirées du PeX sont en accord avec les résultats obtenus lors des études précédentes. L'analyse en composantes principales (ACP) a été réalisée pour avoir une vue globale de la façon dont les diverses propriétés des revêtements sont reliées entre ellesThe overall objectives of this study was to find an environmental-friendly and simple procedure to synthesize titanium-dioxide, as well as, to determine the relation between the structural and functional properties of titanium dioxide coatings. Both of these objective have been attained in this study. By the sol-gel technique, titanium dioxide sols were synthesized by the hydrolysis of titanium(IV)isopropoxide. Nanocrystalline dispersions of TiO2 in water were prepared that were suitable for coatings and having long-term stability (more than 1 year) in terms of polymorphic composition, crystallite and agglomerate size. A design of experiments (DoE) was utilised, to our knowledge, for the first time in MOCVD for the synthesis of TiO2 coatings. It was employed to determine, in a timely and economical manner, the most significant process parameters for any quantifiable property of the coating and to highlight the interaction between these operating parameters, as well as, the correlation between the structure of the coating and the process. The conclusions drawn from the DoE were compared to results obtained by previous studies and were found to concur. Therefore, the DoE was successful in screening the most important process parameters, with a minimum number of experimental trials. For most of the properties that were under investigation, the DoE showed that, the deposition temperature and reactor pressure were, often-times, the most significant. Therefore, to change the microstructure and composition of MOCVD coatings, changing these process parameters will ensure the highest impact. It has to be stressed that the conclusions drawn from the DoE are restricted to the experimental range that was under investigation. Principal Component Analysis (PCA) was conducted to have an overall view of how the different properties of the coatings related with one another. The interpretations made from this analysis were that the photocatalytic (PC) activity of the coatings produced did not relate strongly to the polymorphic composition, which is contrary to literature review and is explained to be a result of the different morphologies that lead to different porosities and specific surface area. The PC activity did not depend on the mass over a critical mass. With this analysis it appeared to be clear that the porosity and specific surface area played a larger role than polymorphic composition. This hypothesis has to be verified because we did not succeed in determining the specific surface area of our coatings during this study. However, some preliminary tests have been conducted showing that cyclic voltametry could be used to evaluate the surface area of our filmsTOULOUSE-INP (315552154) / SudocSudocFranceF

Effects of infrared radiation on the mechanical properties of an epoxy-amine adhesive using a Central Composite Design method

International audienceRecently, the aerospace industry has been facing many challenges, including an increase in the production rates to meet the market needs. In the context of adhesives and liquid shim applications, this means the possibility of on-demand curing. In other words, adhesives must cure slowly at room temperature and this process must be accelerated at any time to allow for the fastest polymerization possible. However, while on-demand curing is possible in several ways (ultraviolet radiation, induction, or microwave), the route chosen in this study is infrared (IR) radiation. This is because this method allows curing at low temperatures (i.e., around 50°C) and is universal, hence requiring no modification in the adhesive formulation. Given that the acceleration of polymerization using thermal (temperature) and nonthermal (radiation–matter interaction) effects has been demonstrated in another study, it is now important to study the properties of such an adhesive after curing under IR radiation. In this study, we measured the following properties: adherence on aluminum 2024-T3 via three-point bending, tensile strength and modulus, and flexural strength and modulus. We also studied the parameters of the IR lamp, including the lamp–adhesive distance and the rate and temperature of polymerization. For this purpose, a composite design of experiments was used, which generally has two main advantages: screening and response surface methodology. On the one hand, screening allows determining the factors, among those selected, that have a significant influence on the studied responses. At the same time, it allows determining the interactions (synergistic effects) between the influencing parameters. On the other hand, response surface methodology allows quantifying the influence of the parameters and determining the optimal ones

Surface Conditioning Effects on Submerged Optical Sensors: A Comparative Study of Fused Silica, Titanium Dioxide, Aluminum Oxide, and Parylene C

International audienceOptical sensors excel in performance but face efficacy challenges when submerged due to potential surface colonization, leading to signal deviation. This necessitates robust solutions for sustained accuracy. Protein and microorganism adsorption on solid surfaces is crucial in antibiofilm studies, contributing to conditioning film and biofilm formation. Most studies focus on surface characteristics (hydrophilicity, roughness, charge, and composition) individually for their adhesion impact. In this work, we tested four materials: silica, titanium dioxide, aluminum oxide, and parylene C. Bovine Serum Albumin (BSA) served as the biofouling conditioning model, assessed with X-ray photoelectron spectroscopy (XPS). Its effect on microorganism adhesion (modeled with functionalized microbeads) was quantified using a shear stress flow chamber. Surface features and adhesion properties were correlated via Principal Component Analysis (PCA). Protein adsorption is influenced by nanoscale roughness, hydrophilicity, and likely correlated with superficial electron distribution and bond nature. Conditioning films alter the surface interaction with microbeads, affecting hydrophilicity and local charge distribution. Silica shows a significant increase in microbead adhesion, while parylene C exhibits a moderate increase, and titanium dioxide shows reduced adhesion. Alumina demonstrates notable stability, with the conditioning film minimally impacting adhesion, which remains low.</jats:p