Membrane patterned by pulsed laser micromachining for proton exchange membrane fuel cell with sputtered ultra-low catalyst loadings

International audienceProton exchange membranes were nano-and micro-patterned on their cathode side by pressing them against stainless steel molds previously irradiated by a Ti:Sapphire femtosecond laser. The membranes were associated to ultra-low loaded thin catalytic layers (25 µgPt cm-2) prepared by plasma magnetron sputtering. The Pt catalyst was sputtered either on the membrane or on the porous electrode. The fuel cell performance in dry conditions were found to be highly dependent on the morphology of the membrane surface. When nanometric ripples covered by a Pt catalyst were introduced on the surface of the membrane, the fuel cell outperformed the conventional one with a flat membrane. By combining nano-and micro-patterns (nanometric ripples and 11-24 µm deep craters), the performance of the cells was clearly enhanced. The maximum power density achieved by the fuel cell was multiplied by a factor of 3.6 (at 50 °C and 3 bars): 438 mW cm-2 vs 122 mW cm-2. This improvement is due to high catalyst utilization with a high membrane conductivity. When Pt is sputtered on the porous electrode (and not on the membrane), the contribution of the patterned membrane to the fuel cell efficiency was less significant, except in the presence of nanometric ripples. This result suggests that the patterning of the membrane must be consistent with the way the catalyst is synthesized, on the membrane or on the porous electrode

High Power Impulse Magnetron Sputtering deposition of Pt inside fuel cell electrodes

International audienceHigh Power Impulse Magnetron Sputtering process is used to incorporate catalytic nanoclusters of platinum into microporous carbon. Such a process leads to an enhancement of the Pt species penetration into the porous media as evidenced by Rutherford backscattering spectroscopy analysis. Each catalyzed porous carbon is tested as a cathode of a proton exchange membrane fuel cell. An increase of 80 % at 0.65 V of the PEMFC power density for a low catalyst loading of 0.02 mg.cm-2 highlights the use of the HiPIMS process versus the conventional DC magnetron sputtering proces

Energy transferred to the substrate surface during reactive magnetron sputtering of aluminum in Ar/O2 atmosphere

International audienceA study of the reactive sputtering of aluminum was carried out by coupling energy flux measurements at the substrate location with conventional diagnostics of the gas phase and analyses of the deposited films. The main purpose was to get some insight into the elementary mechanisms involved at the substrate surface during the film growth in the well known metal and oxide regimes and at the transitions from one to another. Measurements were carried out in front of a 10 cmAl target at a power of 400W (i.e. 5 W/cm2) and a total pressure of 0.6 Pa. The flow rate ratio (O2/O2+Ar) was varied in the range 0 to 50 %. Different kinetics and values of energy transfer, denoting different involved mechanisms, were evidenced at metal-oxide (increasing flow rate) and oxide-metal (decreasing flow rate) transitions. The metal-oxide transition was found to be a progressive process, in agreement with optical emission spectroscopy and deposit analysis, characterized by an increase of the energy flux that could be due to the oxidation of the growing metal film. On the contrary, oxide-metal transition is abrupt, and a high energy released at the beginning that could not be attributed to a chemical reaction. The possible effect of O-ions at this step was discussed

Influence of the HiPIMS voltage on the time resolved platinum ions energy distributions

International audienceHigh Power Impulse magnetron sputtering (HiPIMS) is a common way to create a high and dense ionized metallic vapor without the use of an alternative ionizing device, like radio frequency loops. HiPIMS has been used to perform the deposition of platinum thin films in order to control their morphology. This feature known to depend on the energy of the Pt species incoming onto the substrate during the deposition has to be carefully studied. Therefore, it's necessary to study the ions energy distribution during the sputtering pulse and to follow its evolution with the HiPIMS regime. Pictures of this evolution are presented

Optimization of DC reactive magnetron sputtering deposition process for efficient YSZ electrolyte thin film SOFC

International audienceYttria-stabilized zirconia (YSZ, ZrO2:Y2O3) thin films were deposited by reactive DC magnetron sputtering with a high deposition rate from a metallic target of Zr/Y in an argon/oxygen atmosphere. Plasma parameters and composition analysis of the gas phase reveal that the sputtering process in the "compound" mode is reached for a 2.5 sccm oxygen flow rate. Deposition onto silicon in "metal" mode at a flow rate close to the transition, allows obtaining at very high deposition rates (> 10 µm.h-1) a compact columnar stoichiometric crystallized YSZ film. When deposited on NiO YSZ commercial anode, the obtained coatings show the same properties. In spite of the complexity of the substrate (roughness and porosity), a compact and conformed layer was formed. Annealing treatments in air or hydrogen do not significantly alter the structure of the layers. Electrochemical test at 850°C with a screen-printed LSM (LaSrMnO3) cathode exhibits a satisfying gastightness (OCV=900 mV) and a maximum power density of 350 mW.cm-2

Hedda Friberg-Harnesk, Reading John Banville through Jean Baudrillard

Hedda Friberg-Harnesk sheds new light on the fiction of John Banville thanks to an original theoretical frame: her perceptive use of Baudrillard’s orders of simulacra engages the reader in a stimulating critical conversation with the unstable and uncertain worlds and beings of Banvillean fiction. She explores nine of John Banville’s works published between 1997 and 2015, seven novels (The Untouchable, Eclipse, Shroud, The Sea, The Infinities, Ancient Light, and The Blue Guitar) and two plays ..

Melhoria da qualidade para modelos orientados a objectivos: o caso da abordagem KAOS

Dissertação para obtenção do Grau de Mestre em Engenharia InformáticaAs abordagens de Engenharia de Requisitos Orientada a Objectivos (EROO) foram desenvolvidas para facilitar o trabalho dos engenheiros de requisitos ao, por exemplo, oferecer mecanismos de abstracção (isto é, os objectivos do sistema) que ajudam na elicitação e modelação de requisitos. Uma das abordagens de EROO bem estabelecidas é o KAOS. No entanto, em sistemas de larga escala, criar modelos KAOS pode resultar em modelos de objectivos incompletos e/ou complexos, o que pode dificultar a compreensão desses modelos bem como as suas modificações. Isto pode levar a um aumento dos custos de desenvolvimento do produto e da sua evolução. Assim, para sistemas de larga escala, a gestão eficaz da complexidade e completude dos modelos de objectivos é essencial. Nesta dissertação de mestrado, propomos uma framework de métricas para apoiar a avaliação quantitativa da complexidade e completude dos modelos de objectivos KAOS. Estas métricas são especificadas formalmente, implementadas e incorporadas em uma ferramenta de modelação KAOS. Validamos então, as métricas através de um conjunto de casos de estudo reais e discutimos as práticas identificadas de modelação mais recorrentes

Les professeurs-stagiaires d’IUFM et les technologies

Cette recherche étudie l’appropriation des TICE et les premiers usages par les stagiaires des IUFM. Cette population est généralement équipée et a bénéficié d’une formation à l’Université et à l’IUFM. L’objectif était de savoir si ces conditions sont suffisantes pour que des usages professionnels se développent ou si des obstacles subsistent. À partir de questionnaires et d’analyse de mémoires, nous mettons en évidence une instrumentation limitée, des pratiques collaboratives faibles et des difficultés à utiliser des logiciels spécifiques aux disciplines.This research studies the learning of ICT (Information and Communications technology) and their first use by teacher trainees. This population is generally equipped and has benefited from a training at university and at the IUFM (teacher training university institute). The goal was to know if these conditions are sufficient to favour the development of professional use or if there remain obstacles. Some questionnaires and an analysis of students’ dissertations have revealed a limited instrumentation, poor collaborative practices and some difficulties in using software specific to subjects.Esta investigación estudia la apropiación de las TICE y los primeros usos por los cursillistas de los IUFM. Esta población es generalmente dotada y se ha beneficiado de una formación en la Universidad y en el IUFM. El objetivo era saber si estas condiciones son suficientes para que se desarrollen usos profesionales o si subsisten obstáculos. A partir de cuestionarios y de análisis de memorias ponemos en evidencia una instrumentación limitada, prácticas colaborativas escasas y dificultades para utilizar logiciales específicos a las disciplinas.Diese Untersuchung analysiert, wie die Referendare der PH sich die I-und K-Technologien aneignen und benutzen. Diese Bevölkerungsgruppe ist im Allgemeinen ausgerüstet und wurde an der Universität und an der PH ausgebildet. Das Ziel bestand darin, zu wissen, ob diese Bedingungen reichten, damit eine berufliche Benutzung sich entwickelt oder ob Hindernisse bestehen.Ausgehend von Fragebogen und Analysen von Examsarbeiten stellen wir eine begrenzte Instrumentation, ein geringes Teamwork und Schwierigkeiten, fachspezifische Softwares zu benutzen, klar