Microréacteur pour la catalyse hétérogène<br />Applications : Stockage d'hydrogène dans les hydrocarbures Filtre pour capteur gaz

This manuscript presents the design and the use of silicon microstructured reactor for heterogeneous catalysis and especially for the dehydrogenation of methylcyclohexane reaction. This reaction enables on one hand to store hydrogen and on the other hand to realise technological developments since it is endothermic and difficult to carry out. By consequence, a new microreactor obtained by DRIE was designed and capped with a Pyrex wafer. It bundles microheaters deposited by screen-printing and a high temperature metallic connection. It comprises either a catalyst coming from microtechnology, Pt film deposited by sputtering or a classic catalyst, platinum supported on alumina. For this last catalyst, the microreactor previously preoxidised is pretraited by oxygen plasma or liquid way so that the deposit to walls. The washcoat could be done in open microreactor by dip coating in the suspension or in closed microreactor under vacuum or by liquid circulation. After catalytic tests realised in a macroreactor, the Pt/Al2O3 catalyst was chosen to be inserted in the microreactor. The catalytic tests realised in a microreactor coupled with a mass spectrometer let to show the presence of hydrogen. In parallel, the microreactor was used as filter to improve gas sensor selectivity.Ce mémoire présente la conception et l'utilisation d'un réacteur microstructuré en silicium pour la catalyse hétérogène et en particulier pour la réaction de déshydrogénation du méthylcyclohexane. Cette réaction permet d'une part de restituer de l'hydrogène stocké et d'autre part de réaliser des développements technologiques importants car elle est endothermique et difficile à mettre en œuvre. Ainsi un nouveau microréacteur obtenu par DRIE a été conçu et scellé avec un capot en pyrex. Il intègre des résistances chauffantes déposées par sérigraphie et une connectique métallique « haute température ». Il comprend soit un catalyseur issu de la microtechnologie, film de platine déposé par pulvérisation cathodique soit un catalyseur plus classique, platine supporté sur alumine. Pour ce dernier catalyseur, le microréacteur préalablement préoxydé est prétraité par plasma oxygène ou par voie liquide afin que le dépôt adhère aux parois. L'enduction peut être réalisée en microréacteur ouvert par trempage dans la suspension d'alumine ou en microréacteur fermé sous vide, ou par circulation de liquide. A la suite de tests catalytiques effectués en macroréacteurs, le catalyseur Pt/Al2O3 a été choisi pour être inséré dans le microréacteur. Les tests catalytiques réalisés avec un microréacteur couplé à un spectromètre de masse ont permis de montrer la présence d'hydrogène. En parallèle, le microréacteur a été utilisé en tant que filtre pour améliorer la sélectivité des capteurs de gaz

A simple method for a protective coating on stainless steel against molten aluminum alloy comprising polymer-derived ceramics, oxides and refractory ceramics

International audienceA new coating based on polymer-derived ceramics (PDC), oxides and refractory ceramic with a thickness of around 50 µm has been developed to improve the resistance corrosion of stainless steel substrate against molten aluminum alloy in a thermal energy storage (TES) system designed to run at high temperature (up to 600 °C). These coatings implemented by straightforward methods, like tape casting or paintbrush, were coated on planar and cylindrical stainless-steel substrates, pyrolyzed at 700 °C before being plunged for 600 and 1200 h in molten AlSi12 at 700 °C. The stainless-steel substrate appears healthy without intermetallic compounds, characteristic of molten aluminum alloy corrosion. The protective coating against AlSi12 corrosion shows excellent performance and appears interesting for TES applications

Microréacteur pour la catalyse hétérogène (applications)

Ce mémoire présente la conception et l'utilisation d'un réacteur microstructuré en silicium pour la catalyse hétérogène et en particulier pour la réaction de déshydrogénation du méthylcyclohexane. Cette réaction permet d'une part de restituer de l'hydrogène stocké et d'autre part de réaliser des développements technologiques importants car elle est endothermique et difficile à mettre en œuvre. Ainsi un nouveau microréacteur obtenu par DRIE a été conçu et scellé avec un capot en pyrex. Il intègre des résistances chauffantes déposées par sérigraphie et une connectique métallique " haute température ". Il comprend soit un catalyseur issu de la microtechnologie, film de platine déposé par pulvérisation cathodique soit un catalyseur plus classique, platine supporté sur alumine. Pour ce dernier catalyseur, le microréacteur préalablement préoxydé est prétraité par plasma oxygène ou par voie liquide afin que le dépôt adhère aux parois. L'enduction peut être réalisée en microréacteur ouvert par trempage dans la suspension d'alumine ou en microréacteur fermé sous vide, ou par circulation de liquide. A la suite de tests catalytiques effectués en macroréacteurs, le catalyseur Pt/Al2O3 a été choisi pour être inséré dans le microréacteur. Les tests catalytiques réalisés avec un microréacteur couplé à un spectromètre de masse ont permis de montrer la présence d'hydrogène. En parallèle, le microréacteur a été utilisé en tant que filtre pour améliorer la sélectivité des capteurs de gaz.This manuscript presents the design and the use of silicon microstructured reactor for heterogeneous catalysis and especially for the dehydrogenation of methylcyclohexane reaction. This reaction enables on one hand to store hydrogen and on the other hand to realise technological developments since it is endothermic and difficult to carry out. By consequence, a new microreactor obtained by DRIE was designed and capped with a Pyrex wafer. It bundles microheaters deposited by screen-printing and a high temperature metallic connection. It comprises either a catalyst coming from microtechnology, Pt film deposited by sputtering or a classic catalyst, platinum supported on alumina. For this last catalyst, the microreactor previously preoxidised is pretraited by oxygen plasma or liquid way so that the deposit to walls. The washcoat could be done in open microreactor by dip coating in the suspension or in closed microreactor under vacuum or by liquid circulation. After catalytic tests realised in a macroreactor, the Pt/Al2O3 catalyst was chosen to be inserted in the microreactor. The catalytic tests realised in a microreactor coupled with a mass spectrometer let to show the presence of hydrogen. In parallel, the microreactor was used as filter to improve gas sensor selectivity.ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF

Fabrication of copper objects through lithography-based metal manufacturing

International audienc

Effect of Mn-Zn ferrite powder on the properties of Mn-Zn ferrite formulation for Digital Light Processing

International audienceManganese-Zinc (Mn-Zn) ferrite is a ceramic and soft magnetic material, which can be, used for the fabrication of passive elements integrated in power converters. The main, challenge related to these converters rely on their miniaturization and efficiency, enhancement. Digital Light Processing (DLP) is a potential additive manufacturing, technique to fabricate fine and complex Mn-Zn ferrite components. This paper focuses, on the analysis of the optical properties of the formulations containing Mn-Zn ferrite, powder. Different particle’s sizes (71–1.3 µm) were used to study the influence of the, cured monolayer evolution and the optical properties of the ferrite. We compared, experimental data obtained on formulations with a low content of ferrite particles, (15%.wt) to the results issued from the Mie theory. High solid content (75%.wt) were, investigated to cover the practical applications of DLP and the role of light scattering, was analyzed and discussed in detail for this specific configuration

Sintering Ce-TZP/alumina composites using aluminum isopropoxide as a precursor

International audienceA homogeneous 12Ce-TZP/30 vol% Al$_2$O$_3$ composite material has been manufactured by pressureless-sintering in air green compacts of a powder mixture incorporating aluminum isopropoxide as an organic precursor. Densification of the composite material occurs by grain boundary diffusion and is controlled by the diffusion of Ce cations

Influence of debinding and sintering conditions on the composition and thermal conductivity of copper parts printed from highly loaded photocurable formulations

International audienceMetal 3D printing based on the photopolymerization reaction (Digital Light Processing DLP) of an organic matrix in which metal particles are embedded is a developing technology. This technology requires a step of resin removal and densification by sintering to obtain a metal part. This process has been applied to copper. Photocurable formulations with a high loading rate of copper powder of 60 vol.% were developed and suitable for DLP printing with thicknesses>25 µm. Debinding and sintering cycles were investigated on specimens fast cured by gamma irradiation to save materials and time. A debinding in air at 400 °C and sintering in hydrogen lead to a C content of 0.018 wt.%, similar to the raw copper powder and slightly higher oxygen content. The low thermal conductivity of 250 W·m-1·K-1 highlighted the harmful effect of phosphorus from the powder and photoinitiators such as BAPO. The C and O contents and the thermal conductivity measured on copper parts printed by DLP confirm the results obtained on specimens cured by gamma irradiation

Silicon carbide precursor: structure analysis and thermal behavior from polymer cross-linking To pyrolyzed ceramics

International audienceThe Silres H62C methyl-phenyl-vinyl-hydrogen polysiloxane is a promising candidate as a SiC precursor for 3D printing based on photopolymerization reaction. An in-depth nuclear magnetic resonance spectroscopy analysis allowed us to determine its structure and quantify its functional groups. The polysiloxane was found to have a highly branched ladder-like structure, with 21.9, 31.4 and 46.7% of mono-, di- and tri-functional silicon atoms. The polysiloxane cross-links from 180 C using hydrosilylation between silyl groups (8.4% of the total functional groups) and vinyl groups (12.0%) and contains a non-negligible ethoxy content (2.4%), allowing cross-linking through a hydrolyze/condensation mechanism. After converting the polymer into ceramic and thus releasing mainly hydrogen and methane, the ceramic yield was 72.5%. An X-ray diffraction analysis on the cross-linked and pyrolyzed polysiloxane showed that the ceramic is amorphous at temperatures up to 1200 C and starts to crystallize from 1200 C, leading into 3C-SiC carbon-rich ceramic at 1700 C in an argon atmosphere

Y-TZP, Ce-TZP and as-synthesized Ce-TZP/Al2O3 materials in the development of high loading rate digital light processing formulations

International audienceY-TZP, Ce-TZP and Ce-TZP/Al2O3 materials are widely investigated in dentistry. Digital Light Processing (DLP) is considered as a breakthrough technology for the dental field to fine print Y-TZP green parts. High loading photocurable formulations (>45 vol%) with Y-TZP , Ce-TZP commercial powders and Ce-TZP/30vol% Al2O3 as-synthesized powder suitable to DLP printing were achieved in this study. A low specific surface area (5-13 m²/g) of particles without any pores and 1 wt% to 2 wt% of steric dispersant are required to obtain high loading formulations. The as-synthesized composites provide these properties by increasing the calcination temperature from 800°C to 1200°C. The as-prepared ceramic formulations based on the same photocurable resin exhibit a curing behavior suitable to DLP process for Y-TZPformulations (thickness > 50 μm in few seconds with a high conversion rate) in comparisonwith ceria ceramic. The ceria is a strongly UV absorbing material and a specific formulationis developed to obtain 80% of conversion and a cured thickness of 75 μm in 0.5 s

Deposition of g-Al2O3 layers on structured supports for the design of new catalytic reactors

International audienceStructured objects of different characteristic size have been coated with g-Al2O3. The oxide layers are characterised in terms of thickness, surface area, crystalline phase, adherence on the support surface, etc. According to the structured object, adherent oxide layers from less than 1 to around 200 mm have been obtained