Les Parlements de sciences, outils au service des débats science-société entre jeunes

Comment faire en sorte que les jeunes s’impliquent davantage dans les échanges autour de l’actualité scientifique ? Les Parlements de sciences mis en place par l’université de Strasbourg proposent une réponse à cette interrogation : après une présentation de ces dispositifs et une première évaluation leurs apports, l’auteur ouvre des pistes pour compléter la réflexion et développer ce moyen de mise en débat des questions science-société

Electrophoretic deposition of aramid nanofibers and carbon nanomaterials on carbon fibers

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Controlling shot noise in double-barrier magnetic tunnel junctions

We demonstrate that shot noise in Fe/MgO/Fe/MgO/Fe double-barrier magnetic tunnel junctions is determined by the relative magnetic configuration of the junction and also by the asymmetry of the barriers. The proposed theoretical model, based on sequential tunneling through the system and including spin relaxation, successfully accounts for the experimental observations for bias voltages below 0.5V, where the influence of quantum well states is negligible. A weak enhancement of conductance and shot noise, observed at some voltages (especially above 0.5V), indicates the formation of quantum well states in the middle magnetic layer. The observed results open up new perspectives for a reliable magnetic control of the most fundamental noise in spintronic structures.Comment: 8 pages, 4 figure

Lithium conducting solid electrolyte Li1.3Al0.3Ti1.7(PO4)3 obtained via solution chemistry

NaSICON-type lithium conductor Li1.3Al0.3Ti1.7(PO4)3 (LATP) is synthesized with controlled grain size and composition using solution chemistry. After thermal treatment at 850 C, sub-micronic crystallized powders with high purity are obtained. They are converted into ceramic through Spark Plasma Sintering at 850–1000 C. By varying the processing parameters, pellet with conductivities up to 1.6 * 10−4 S/cm with density of 97% of the theoretical density have been obtained. XRD, FEG-SEM, ac-impedance and Vickers indentation were used to characterize the products. The influence of sintering parameters on pellet composition, microstructure and conductivity is discussed in addition to the analysis of the mechanical behavior of the grains interfaces

Artificial Kagome Arrays of Nanomagnets: A Frozen Dipolar Spin Ice

Magnetic frustration effects in artificial kagome arrays of nanomagnets are investigated using x-ray photoemission electron microscopy and Monte Carlo simulations. Spin configurations of demagnetized networks reveal unambiguous signatures of long range, dipolar interaction between the nanomagnets. As soon as the system enters the spin ice manifold, the kagome dipolar spin ice model captures the observed physics, while the short range kagome spin ice model fails.Comment: 4 pages, 4 figures, 1 tabl

CMAS interaction with yttrium based systems: Towards a promising solution?

Anti-CMAS coatings are designed to protect thermal barrier coatings against degradations due to CMAS infiltration. They are dedicated to react as fast as possible with CMAS compounds in order to generate a new phase that will not let the CMAS infiltration going on. In addition to the fast kinetics, the preparation of large quantities of phases with as less as anti-CMAS material as possible is sought as well as the obtaining of a dense and impermeable phase. Reference anti-CMAS material is gadolinium zirconate, it has been demonstrated as efficient to block CMAS infiltration. The efficiency of yttria for the same application has been studied by previous works at the CIRIMAT laboratory [1]. The starting point of this work was first, to make a comparative study of the anti-CMAS properties of gadolinium zirconate and yttria based anti-CMAS compositions and secondly, to discuss on the behaviour of a mixed composition i.e. yttrium zirconate. This insight on the mechanism of interactions of CMAS with the yttrium based systems and gadolinium reference is obtained at the light of a large number of interactions experiments and characterizations. Interaction durations between 1h and 100h were investigated, with either 50/50 or 80/20 mass ratio of CMAS/anti-CMAS. Different temperatures of interaction between 1200°C to 1300°C were also scanned. The phases in presence were systematically characterized by XRD, SEM, EDX and Castaing microprobe local analyses and cartographies (Figure 1a)). In particular, the proportion and composition of phases are detailed as a function of the interaction time (Figure 1b)) for each anti-CMAS-CMAS interaction system. From these experiments, the mechanisms of interaction between CMAS and Y2O3, Y2Zr2O7 and Gd2Zr2O7 are evidenced. Whereas Y2O3 interaction leads to the higher proportion of reaction products, the products impermeability is also superior for this composition. The depth of infiltration of CMAS into a dense pellet anti-CMAS material for a given time is longer for Y2Zr2O7 as compared to the two others. However Y2Zr2O7 benefit is due to a higher Ca2+ trapping capability with the formation of Ca4Y6 like phase instead of Ca2Y8 for Y2O3 (Figure 1c)). In this respect, yttrium zirconate demonstrates a synergetic effect as compared to Y2O3 and Gd2Zr2O7. The origin of this synergy is interpreted as coming from the presence of both zirconium and yttrium. A large part of the discussion is based on the study of powders interactions, an insight into the interactions of CMAS with anti-CMAS pellets of the different compositions will also be presented and discussed. Fundamental and applicative aspects will be covered. Please click Additional Files below to see the full abstract

Nucleation and growth mechanisms of trivalent chromium conversion coatings on 2024-T3 aluminium alloy

Nucleation and growth mechanisms of trivalent chromium conversion coatings on 2024 aluminium alloy (AA 2024) were studied. Nucleation of 25 nm diameter nodules was observed on the ridges of the scalloped structure of degreased and desmutted AA 2024 after very short time of conversion treatment corresponding to the formation of a 12 nm thick precursor layer. Then, the composition of this layer evolved and concomitantly a chromium and zirconium outer layer deposited on top of it. Rather long-lasting anticorrosive properties were measured even for conversion coatings formed after short exposure to the conversion bath, except for the precursor layer