Mise en suspension d'une poudre micronique par effet vortex

National audienceNew materials based on nanotechnology are reaching the market in a wide variety of consumer products. Since these nanostructured materials can be in powder form, a suspending powder system is essential for many purposes: For in vivo inhalation toxicological studies,for workers and consumers protection, for instrumental development widening aerosol measurement spectrum. Different powders suspending systems have been developed like the rotating drum or the single drop. They are used as a reference method to evaluate bulk materials dustiness. Usually cumbersome, these systems need a huge amount of powder (a few hundred grams) and require time-consuming cleaning processes which could be even more tedious when a nanostructured material and/or a toxic powder is used. The aim of this work is to evaluate the behavior of a powder suspending system by vortex effect. This system is very simple and requires a very small amount of powder (a few grams) in a tube [1,2]. It has been set up to study the dustiness under controlled and reproducible conditions. Different tests have been performed with a Al2O3 powder. They allowed not only to characterize the influence of shaking speed and powder mass, but also to measure the particle size and the number concentration as shown on the figures belowLa mise en suspension de poudres est un processus essentiel dans différents domaines : il permet d'étudier la physico-chimie de la phase " aérosol " d'une poudre donnée ; un tel système est indispensable pour mener des études toxicologiques par inhalation in vivo ; dans le domaine de la protection des personnes (travailleur, consommateur) et de l'environnement, il permet d'évaluer l'émissivité potentielle des poudres, et en conséquence d'adapter les mesures de protection ; un tel dispositif facilite également le développement instrumental, en donnant accès à un spectre large d'aérosols. Nous rapportons ici les résultats d'une étude consacrée à la mise en suspension par effet vortex. Ce système est particulièrement simple [2, 3] : il consiste en l'agitation d'une faible quantité de poudre, placée dans un tube à essai. Nos essais ont porté sur une poudre micronique d'alumine. L'aérosol obtenu a été caractérisé en nombre et taille à l'aide de systèmes CNC, SMPS, et APS. Des essais de sensibilité ont été menés en termes de quantité de produit, et de niveau d'agitation. Nous avons relevé une très bonne répétabilité des résultat

Investigation of the release of particles from a nanocoated product

International audienceManufactured products are being coated with nanoparticles in order to functionalize them with antibacterial or self-cleaning properties or to improve their durability etc. As the (eco-) toxicological effects of the nanoparticles are not well known yet, their use could lead to new potential risks for the workers, the consumers and the environment. This study focuses on the release of the nanoparticles during the operations related to the handling and processing of an automotive part. The part is made up of a metallic alloy and, in order to reduce friction, the part is nano-coated with inorganic fullerenes. The mechanical stresses appearing during these operations are reproduced in a nano-secured facility. The release of nanoparticles is found to be increasing with the wear energy applied on the surface

Etude de l'empoussièrement des poudres par un test de fluidisation

National audienceThe aim of this study is to use a fluidized bed as a dustiness test based on entrainment and elutriation phenomena for a reconstructed model system. Once the operating conditions were identified, a simple phenomenological model was established, able to predict the amount of dust initially present in a mixture. In order to do that, a parametric study was conducted with bimodal powder mixtures. Thus, large particles simulate the powder and the fine dust. The experimental study was carried out with Geldart A and C particles, in a fluidized bed. Furthermore, the influence of some intrinsic and extrinsic parameters of the bulk on the dust emission was studied. Subsequently, different models present in the literature were tested in order to predict the dustiness. This comparison allowed choosing the model of Santana et al. (1999) which showed a better match with the results of this study.L'objectif de ce travail est d'utiliser un lit fluidisé comme test d'empoussièrement en se basant sur les phénomènes d'entraînement et d'élutriation pour un système modèle reconstitué. Suite à l'identification des conditions opératoires, un modèle phénoménologique simple capable de prédire la quantité de poussière initialement présente dans un mélange, a été établit. Une étude paramétrique a été réalisée avec des mélanges de poudres et de poussières de tailles différentes ; ainsi, les grosses particules simuleront la poudre et les fines les poussières. Par ailleurs, nous avons étudié l'influence de certains paramètres intrinsèques du mélange sur l'empoussièrement et testé différents modèles rencontrés dans la littérature permettant de prédire l'empoussièrement. Cette comparaison a permis de choisir le modèle de Santana et al. (1999) qui a montré une meilleure adéquation avec les résultats de cette étude

Exposure assessment based recommendations to improve nanosafety at nanoliposome production sites

The NANOFOL concept aims at creating nanodevices containing a drug for inflammatory disorder treatment. This paper provides recommendations for nanosafety based on a measurement campaign which aimed at identifying exposure risks with respect to two specific phases of the products lifecycle, that is, production of the device and its waste management. The nanoparticles presence both in air and in liquid phase was studied. While no emissions were detected during the production period, many recommendations have been made, particularly regarding the nanowaste treatment, based on nanosafety guidelines.Eugenia Nogueira (SFRH/BD/81269/2011) holds scholarships from Fundacao para a Ciencia e a Tecnologia (FCT). The authors thank the EC for funding from the European Union Seventh Framework Programme (FP7/2007-2013) under Grant Agreement NMP4-LA-2009-228827 NANOFOL

Long-term dust generation from silicon carbide powders

Most dustiness studies do not measure dust release over long durations, nor do they characterize the effect of dust release on bulk powders. In this study, we tested the dustiness of two different samples of silicon carbide (SiC) powders (referred to as F220 and F320) over six hours using a vortex shaker. Additionally, we characterized the bulk sample for change in shape and size distribution due to the testing. Both powders release respirable fractions of dust particles but differ in their dust generation behavior. The numbers of released respirable particles for powder F220 are more than two times higher than those of powder F320. The dust generation mechanism might include the release of aerosols due to the attrition of particles owing to inter-particle and particle-wall impaction. This study emphasizes the need for long duration dustiness tests for hard materials like SiC and characterization for change in bulk material properties due to dust generation and release. Furthermore, the results can aid in selecting the bulk material for long-term applications based on dustiness

Study of the particle motion induced by a vortex shaker

The behaviour of a traced alumina particle lying on limestone powders with similar features has been studied in a test tube agitated by a vortex shaker aiming at studying dust emissions from powders. PEPT (Positron Emission Particle Tracking) was used for measuring the particle's position. Population densities were computed as the frequency of the particle's presence in different regions dividing the two horizontal axes and the vertical axis, respectively. The velocities of the particle were calculated by filtering out all displacements inferior to a critical distance dcrit so as not to consider spurious movements caused by experimental noise. After its validation, the methodology was applied to the standard condition of a vortex shaker experiment (ω = 1500 rpm, 2 g of powder and open test tube). While the horizontal coordinates and velocity components follow a symmetric distribution, the vertical coordinate is characterised by a large asymmetrical plateau. The heights reached by the particle (up to 24.3 mm) are small in comparison to that of the test tube (150 mm). The greatest velocities are found near the inner wall of the test tube and at the highest heights where the population densities are the lowest. The median velocity of the particle is 0.0613 m.s −1 whereas its median kinetic energy is 8.4E-12 J. The method explicated in the present study is directly applicable to any other sets of data obtained through PEPT, especially if the system is of small dimension

Produits émetteurs potentiels des particules nanométriques ou submicroniques

Caractériser les émissions de nanomatériaux est un objectif complexe à atteindre. S’agit-il d’émissions dans l’eau ou dans l’air ? Quelles sont les formes, les tailles, les compositions des objets émis ? Comment caractériser les expositions ? Quelle sollicitation des nanomatériaux donnant lieu à des émissions peut-on envisager ? Quelle voie d’exposition peut-on suspecter ou bien quelle toxicité peut avoir la nanoparticule émise ? À toutes ces questions générales s’ajoutent des difficultés techniques portant sur la caractérisation des émissions : l’outil universel capable de décrire de manière exhaustive les objets émis quelle que soit leur taille ou leur forme n’existe pas encore. Ainsi, après une description la plus complète possible de l’usage des nanomatériaux dans notre société, le présent article vise à décrire l’état de l’art sur la caractérisation des nanoparticules émises tant d’un point de vue des méthodes traditionnelles que des dernières avancées technologiques. La voie d’exposition par inhalation est généralement considérée comme étant la principale. Les méthodes de caractérisation des aérosols sont par conséquent particulièrement développées dans cet article. Les appareils capables de telles caractérisations sont décrits, leurs limites lorsqu’elles existent sont également évoquées. Comme les expositions aux nanoparticules sont de plus en plus sources d’inquiétudes, l’article présente également les grands principes de la nanosécurité. Ainsi tous les industriels intéressés par le sujet peuvent à terme s’approprier ces notions afin de limiter voire supprimer les relargages éventuels dus à des nouveaux matériaux

Development of aerosol quantitative method of nanoparticles and the risk assessment

International audienc