Expositions professionnelles lors de la fabrication addtive utilisant des poudres métalliques

International audienc

An intercomparison exercise of good laboratory practices for nano-aerosols sizemeasurements by mobility spectrometers

International audienceAn intercomparison campaign on nanoparticle size measurement was organized in the frame of the French nanoMetrology club. The aim of this study is to make an inventory of the metrological capabilities of all measurement techniques in France involved in the “nano” size range, including the SMPS (Scanning Mobility Particle Sizer) concerning aerosol metrology. For this study, four samples have been proposed, namely (1) - a SiO2 colloidal suspension (FD304) consisting of a monomodal population, (2) - two samples consisting of two nanoparticle populations of SiO2 having proportions to be determined and (3) - a TiO2 colloidal suspension. Ten SMPS associated to five participants around a common experimental setup were performed in link with a control SMPS to have simultaneous measurements with a same instrument in each laboratory in parallel with the SMPS used by each partner. This article presents SMPS results of this study associated with the description of the experimental set-up and the sample preparation protocol with an identified schedule and comparison with SEM measurements. The present paper does not focus on the actual capability of the tested mobility spectrometers, but aims to highlights the good laboratory practices using their own but common resources in terms of aerosol generation and measurement set-ups

Etude du colmatage des filtres THE à petits plis

National audienceLa purification de l'air revêt une grande importance dans de nombreux secteurs tels que les industries nucléaires, pharmaceutiques, agroalimentaires et électroniques. Cette étape de filtration est fréquemment réalisée en utilisant un medium filtrant à base de fibres de verre. Le plissage du medium filtrant, qui augmente la surface de filtration pour un même encombrement de l'équipement, permet d'accroître la capacité de collecte des particules. Les performances du médium filtrant se caractérisent par la probabilité de pénétration des particules (fonction de la taille des particules) et par la perte de charge au travers du medium au débit et conditions du procédé. A ce jour, les études réalisées sur les performances des filtres concernent essentiellement l'évolution de l'efficacité et de la perte de charge sur des media plans. Les paramètres étudiés portent sur la structure du medium (densité des fibres, diamètre des fibres), sur les conditions de fonctionnement (vitesse de filtration, température, pression de gaz) et sur les caractéristiques des aérosols (nature, densité, distribution granulométrique). Ainsi, de nombreux auteurs ont étudié l'évolution de la perte de charge et de l'efficacité de filtration au cours du colmatage par des particules microniques ou submicroniques principalement sur des filtres plans. Au cours de cette étude, nous nous sommes intéressés au colmatage de filtres plissés à petits plis, très répandus dans l'industrie nucléaire française. Préalablement, une caractérisation aéraulique de l'évolution de la perte de charge des filtres en fonction de la vitesse de filtration a été réalisée. Dans un premier temps, des filtres, dont la géométrie des plis correspond à celle des filtres employés dans les installations nucléaires, ont été colmatés, sur un banc d'essais à petite échelle, par des particules microniques pour différentes vitesses de filtration. Les courbes de colmatage obtenues sur le banc d'essais à petite échelle, ont ensuite été confrontées aux résultats obtenus avec l'installation CATFISH qui permet d'étudier, dans des conditions identiques, le colmatage de filtres de dimensions supérieures

Uptake of m -xylene and VOC emissions by mineral photocatalytic paints of indoor air building interest

International audienceGiven the toxic nature of many volatile organic compounds (VOCs) present within indoor settings, it behooves the building engineering community to develop control strategies for contaminant removal to mitigate health impacts and improve well-being within indoor building environments. Photocatalytic paints belong to a class of technologies potentially used to obtain self-cleaning wall surfaces for air decontamination within building environments. They offer a promising solution for the building engineering industry involved in paint manufacturing processes to produce paint formulations that limit indoor air pollution and consequently individual exposition of inhabitants. In this work, we report on the uptake efficiency of m-xylene on one reference paint and three mineral paints impregnated with a photocatalytic agent, namely, a conventional photocatalyst containing 3.5% of nano-TiO2 and two new nano-TiO2 photocatalysts coated with polyethylene glycol (PEG 3350) and a hybrid cellulose nanocrystals–nano-TiO2 (CNC) containing 3.5% and 0.5% of nanoparticles, respectively. The photocatalytic degradation of these paints under UV irradiation and the consequent VOC emissions were assessed to evaluate the photocatalytic stability of the nano-TiO2 photocatalytic paints. The experimental results shown neither photocatalytic activity nor VOC emissions for the reference paint containing exclusively micro-TiO2 (that is, no nano-TiO2 material) particles under given experimental conditions. On the other hand, the results showed that the paint containing CNC nanoparticles (NPs) had only a finite photocatalytic effect that was likely due to the low quantity of the nano-TiO2 photocatalyst present within the paint formulation matrix. Furthermore, it was observed that the paints containing nano-TiO2 and PEG 3350 NPs resulted in an important photocatalytic activity that, unfortunately, led to consequential VOC emissions resulting from the polymeric matrix photo-oxidation reactivity under the given experimental conditions employed. Overall, the experimental results indicate that the paint containing PEG 3350 NPs had a greater photocatalytic activity than the paint containing the nano-TiO2 particles. Further, it was observed that the VOC emissions of this PEG 3350 paint decreased with the aging time (28% and 10% for 500 hours and 1000 hours of aging, respectively). Based on these results, the PEG 3350 photocatalyst integrated in mineral paint is a promising indoor air decontamination engineering solution

Emission Characteristics and Potential Exposure Assessment of Aerosols and Ultrafine Particles at two French Airports

International audienceAirports are significant contributors of atmospheric pollutant aerosols, namely ultrafine particles (UFPs). This study characterizes the particle number concentration (PNC), the median particle size (dmn50), and the metallic composition of medium-haul area and engine aerosols at two French air-ports (Paris-CDG and Marseille). This study followed the standard operating procedures for char-acterizing aerosol emissions from 5 nm to 8 µm (OECD, 2015; EN 17058:2018). It allows determin-ing which are the specific parameters directly related to the emission sources and their contribu-tion to the overall aerosols measured at workplace in airports. The particulate emissions observed during aircraft engine start-up were ~19× higher than the average airborne concentration. The particle size distributions remained mostly <250 nm with dmn50 < 100 nm (showing a specificity for the medium-haul area with an average dmn50 of ~12 nm). The dmn50 can be used to distinguish emis-sion peaks due to aircrafts (dmn50~15 nm) from those due to apron vehicle activities (dmn50 > 20 nm). Chemical elements (titanium and zinc) were identified as potential tracers of aircraft emissions and occurred mainly at the micrometric scale. For aircraft engine emissions, UFPs are mainly due to fuel combustion with the presence of carbon/oxygen. The study concludes with suggestions for future research to extend on the findings presented

TiO2 nanoparticles coated with bio-inspired ligands for the safer-by-design development of photocatalytic paints

International audienceAddition of titanium dioxide nanoparticles (TiO2 NPs) in photocatalytic paints represents a promising alternative aiming to mineralize gaseous pollutants, such as volatile organic compounds (VOCs). However, the risks of release of nanoparticles to human health and the environmental impact have to be taken carefully into account for their development. To take into account these risks, we develop a new method of TiO2 NP synthesis. Here, we report the electrostatic stabilization in aqueous medium with pyrophosphate buffers of different pH ranges followed by coating with bio-inspired molecules (lysine, deferoxamine, dopamine) and polymers (polyacrylic acid, polyethylene glycol, polydopamine) of 4–5 nm spherical photocatalytic TiO2 NPs for the development of safer-by-design photocatalytic paint. Characterization of the so-formed TiO2 nanocomposites by dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS) showed the good grafting of the ligands on the TiO2 surface and an enhanced stability in water compared to the pristine TiO2 NPs. The photocatalytic activity of the TiO2 nanocomposites was investigated by following the degradation of methylene blue (MB) under irradiation. The results showed a modulation of the photocatalytic activity (decrease or increase of the MB degradation rate) as a function of the nature/binding strength of the bio-inspired coating on the oxide surface. Finally, the most promising nanocomposites were incorporated in paints on which preliminary chalking assays were performed after storage for one year in the dark or in interior daylight

CNC/AgNP hybrids as safer-by-design biocides in paints

International audienceIn this work, biocidal paints are designed by a safer-by-design approach where an efficient antibacterial activity is provided by nanohybrids consisting of silver nanoparticles (AgNPs) nucleated on a bio-based substrate (cellulose nanocrystals, CNCs), to be included in an amount as low as possible and dispersed in an aqueous suspension. Three CNC/AgNP hybrids varying in CNC surface modifications are characterized in depth by transmission electron microscopy, atomic absorption spectroscopy and X-ray diffraction, and used in realistic paint formulations. The analysis of dry-film degradation followed by artificial weathering and mechanical solicitation (i.e., abrasion) reveals a reduced airborne emission of particles that could have harmful impact on human health and the environment. However life cycle assessment shows a weak beneficial impact due to the low amount compared to the paint manufacturing impact. Finally, the biocidal activity was clearly detected on dry paints using Bacillus Subtilis bacteria. It demonstrates that the resulting dry-state paints containing the AgNPs best dispersed and with the smallest size (i.e., 11 nm) show the strongest biocidal effect. This approach allows considerable reduction of the Ag amount to reach an antibacterial effect comparable to AgCl. Moreover, no specific toxicity is revealed and only biodegradable CNCs will persist in the environment at the end of the antimicrobial activity provided by AgNPs. The development of such CNC/AgNP hybrids, considering the overall life cycle of the material like paint, opens the road to the development of highly efficient and more eco-friendly materials

Towards the development of safer by design TiO 2 -based photocatalytic paint: impacts and performances

International audienceAddition of titanium dioxide (TiO 2) (nano)particles into photocatalytic paints represents a promising alternative aiming to mineralize gaseous pollutants, such as volatile organic compounds (VOCs) into innocuous species (H 2 O and CO 2). Despite important industrial and economic benefits, some concerns were raised regarding the risks associated with nano-objects and their human and environmental impacts. To mitigate potential risks associated with the use of these nano-objects, we report a safer by design strategy to develop a photocatalytic paint containing TiO 2 nanoparticles (NPs) taking into consideration the safety aspects over its life cycle. Specific innovative types of TiO 2 NPs were synthesized. These nanoparticles were then incorporated into an organic matrix-based paint. These paints were applied on standard substrates and underwent artificial weathering in an accelerated weathering chamber with controlled parameters. Photocatalytic efficiency towards airborne VOCs was measured for all the paints. Mechanical solicitation through abrasion and incineration tests were performed to assess the potential emission of airborne particles that could lead to human or environmental exposure. In parallel, toxicology studies were conducted to assess the hazards associated with the pristine particles and paint residues. Using this safer by design strategy, we succeeded in decreasing the negative impact of TiO 2 on the paint matrix while keeping a good photocatalytic efficiency and reducing the NP release. Taken together, these results show that we succeeded in generating safer by design paints, thanks to the use of these specifically developed TiO 2 NPs, which exhibit similar photocatalytic properties and enhanced physical properties as compared to paints containing the reference TiO 2 NPs, while reducing their potential hazards

Metrological Protocols for Reaching Reliable and SI-Traceable Size Results for Multi-Modal and Complexly Shaped Reference Nanoparticles

International audienceThe study described in this paper was conducted in the framework of the European nPSize project (EMPIR program) with the main objective of proposing new reference certified nanomaterials for the market in order to improve the reliability and traceability of nanoparticle size measurements. For this purpose, bimodal populations as well as complexly shaped nanoparticles (bipyramids, cubes, and rods) were synthesized. An inter-laboratory comparison was organized for comparing the size measurements of the selected nanoparticle samples performed with electron microscopy (TEM, SEM, and TSEM), scanning probe microscopy (AFM), or small-angle X-ray scattering (SAXS). The results demonstrate good consistency of the measured size by the different techniques in cases where special care was taken for sample preparation, instrument calibration, and the clear definition of the measurand. For each characterization method, the calibration process is described and a semi-quantitative table grouping the main error sources is proposed for estimating the uncertainties associated with the measurements. Regarding microscopy-based techniques applied to complexly shaped nanoparticles, data dispersion can be observed when the size measurements are affected by the orientation of the nanoparticles on the substrate. For the most complex materials, hybrid approaches combining several complementary techniques were tested, with the outcome being that the reliability of the size results was improved