Corrosion Protection of Magnesium Alloys: From Chromium VI Process to Alternative Coatings Technologies

Magnesium and its alloys present several advantages such as a high strength/weight ratio and a low density. These properties allow them to be used for many aeronautical applications but they are very sensitive to corrosion. In order to solve this problem, chromium VI conversion coatings (CCC) are deposited on the surface before a protective top coat application. This process is now limited by several environmental laws due to the high toxicity of hexavalent chromium. However the chemical mechanisms of CCC deposition will be detailed in this chapter in order to understand the chemical properties of this coating. Pre-treatment steps allow cleaning and preparing the surface for improving the coating deposition. A final layer of chromium (III) oxide and magnesium hydroxide composes the coating allowing the protective properties. Orthorhombic potassium chromate clusters trapped on the coating surface give self-healing property to the coating. Alternative conversion coatings are based onto solutions containing chromium (III), permanganate, phosphates, Rare Earth Elements (REEs) or vanadium. The second part of this chapter will detail the deposition and the protection mechanisms of these promising processes of CrVI substitution. Among them, permanganate/phosphate-based coating presents a better corrosion resistance than CCC and REEs have very efficient self-healing properties

Raising awareness on Archaeology: A Multiplayer Game-Based Approach with Mixed Reality

International audienceOur research deals with the development of a new type of game‐based learning environment: (M)MORPG based on mixed reality, applied in the archaeological domain. In this paper, we propose a learning scenario that enhances players' motivation thanks to individual, collaborative and social activities and that offers a continuous experience between the virtual environment and real places (archaeological sites, museum). After describing the challenge to a rich multidisciplinary approach involving both computer scientists and archaeologists, we present two types of game: multiplayer online role‐playing games and mixed reality games. We build on the specificities of these games to make the design choices described in the paper. The proposed approach aims at raising awareness among people on the scientific approach in Archaeology, by providing them information in the virtual environment and encouraging them to go on real sites. We finally discuss the issues raised by this work, such as the tensions between the perceived individual, team and community utilities, as well as the choice of the entering point in the learning scenario (real or virtual) for the players' involvement in the game

Evaluation of fixed point H2S gas detectors intended for use in industrial safety applications

International audienceH2S gas detectors are used by a wide variety of industrial companies for safety reasons, e.g: Oil&Gas, Chemistry, Water Treatment. The detectors are usually installée! where H2S can be found in ambient air in order to prevent toxic risk. The tests, requested by the French Ministry for Environment, were conducted by INERIS in partnership with Exera (an association of companies and organizations which invest in instruments, measurement, control and automation Systems). This évaluation was carried out to investigate if H2S gas detectors can operate efficiently under différent operating conditions on industrial sites (température, humidity, pressure, interfering species, etc.). The measurement range of the detectors that were evaluated is 0- 20 ppm

Oxy-combustion de l'hythane dans un brûleur à jets séparés

Les effets de l'ajout d'H2 et de la baisse de la richesse sur une oxy-flamme non-prémélangée turbulente sont étudiés dans le cas d'un brûleur à 2 jets fortement séparés, le 1er débitant de l'hythane (Gaz Naturel+H2) et le 2nd de l'O2 pur. La visualisation de l'émission du radical OH* montre que l'ajout d'H2 et la diminution de la richesse permettent de réduire la hauteur d'accrochage de la flamme et ses fluctuations. L'étude de l'aérodynamique en milieu non-réactif via la PIV montre que ces 2 paramètres favorisent le mélange des jets et la diminution de la taille de la zone de recirculation

Multiscale Modeling of Dust Charging in Simulated Lunar Environment Conditions

International audienceA key aspect of dust adhesion to space equipment is the accumulation of charge under the space plasma environment. Recent models and experiments show possible negative charging of dust grains under VUV illumination. Macroscopic potential measurements conducted during a test campaign show that both positive and negative average charging can be reached under VUV irradiation pending on vacuum chamber configuration, suggesting that both situations can exist at lunar surface. Simulations of dust charging at microscopic scale are conducted with the SPIS software to evaluate electrical charge and electric field amplifications induced by the granular structure of the lunar regolith. A multi-layer pile of dust is modelled under lunar conditions. Grains from the first two layers tend to microscopically acquire both negative and positive charge patches when illuminated with a 45° VUV incidence angle, this differential charging being less pronounced under normal incidence angle. It is also found that dust deeply buried in the lunar soil may charge more negative due to the collection of environmental electron only. This effect is thought to reinforce the grain supercharging model presented by other authors. We show however that such charge development may be limited by electrical conduction pending on dust electrical properties

Spacecraft worst-case surface charging: On the importance of measuring the electron emission yield under representative environmental conditions

International audienceTo represent the time spent by space materials on ground before launch, the measurement of secondary electron emission properties is performed after long duration exposure to ambient atmosphere and humidity. The observed change with respect to pristine samples have an impact on the estimation of worst-case surface charging levels in geostationary orbit, especially for a spacecraft in eclipse. It is therefore recommended to adequately outgas the samples with respect to the expected flight conditions and ageing effects

Factoring N=prqsN=p^r q^s for Large rr and ss

International audienceBoneh et al. showed at Crypto 99 that moduli of the form N = p^r q can be factored in polynomial time when r ≃ log(p). Their algorithm is based on Coppersmith’s technique for finding small roots of polynomial equations. In this paper we show that N = p^r q^s can also be factored in polynomial time when r or s is at least (log p)^3; therefore we identify a new class of integers that can be efficiently factored.We also generalize our algorithm to moduli with k prime factors N = \prod_{i=1}^k p_i^{r_i} ; we show that a non-trivial factor of N can be extracted in polynomial-time if one of the exponents r_i is large enough

Detection of label-free cancer biomarkers using nickel nanoislands and quartz crystal microbalance

We present a technique for the label-free detection and recognition of cancer biomarkers using metal nanoislands intended to be integrated in a novel type of nanobiosensor. His-tagged (scFv)-F7N1N2 is the antibody fragment which is directly immobilized, by coordinative bonds, onto ~5 nm nickel islands, then deposited on the surface of a quartz crystal of a quartz crystal microbalance (QCM) to validate the technique. Biomarker GTPase RhoA was investigated because it has been found to be overexpressed in various tumors and because we have recently isolated and characterized a new conformational scFv which selectively recognizes the active form of RhoA. We implemented a surface chemistry involving an antibiofouling coating of polyethylene glycol silane (PEG-silane) (<2 nm thick) and Ni nanoislands to reach a label-free detection of the active antigen conformation of RhoA, at various concentrations. The methodology proposed here proves the viability of the concept by using Ni nanoislands as an anchoring surface layer enabling the detection of a specific conformation of a protein, identified as a potential cancer biomarker. Hence, this novel methodology can be transferred to a nanobiosensor to detect, at lower time consumption and with high sensitivity, specific biomolecules