Research on xylitol crystallization by shearing and seeding for its use as a phase change material

As thermal energy storage is becoming more important, new materials are being studied. Sugar-alcohols (SA) are very promising as phase change materials (PCM) because they are non-toxic, affordable and their latent heat is high. However, undercooling and low crystallization rates are some of the problems present in these materials. The SA studied in this work is xylitol, and using a microscope connected to a transparent counter-rotating shear cell, the effect of secondary nucleation is studied, as well as the crystallization rate of xylitol and how undercooling affects it. From the results, it is deduced that a proper seed preparation and handling is needed. The crystal structure is also studied, using XRPD diffractograms and differential scanning calorimetry. © 2021 Institute of Physics Publishing. All rights reserved

Structural transformation in Al-51 at% Zn eutectoid alloy observed in internal friction

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Une approche hybride pour étudier le coefficient de couplage sous impulsions laser courtes

L'environnement de l'Orbite Terrestre Basse (OTB) est composé de débris spatiaux en raison de la fréquence des lancements d'objets. En résulte une instabilité des cascades collisionnelles dont il devient important d'atténuer les risques. Une des solutions proposées est l'interaction laser. Avec le développement des technologies laser, en fonction de la nature de la matière cible, des études sur les paramètres d'irradiation laser montrent que, pour une intensité appropriée, une longueur d'onde et une longueur d'impulsion courtes peuvent conduire à un coefficient de couplage Cm maximisé pour produire un couplage impulsionnel mécanique optimal, et minimiser la charge thermique. Ainsi, des expériences ont été réalisées sur l'installation ELFIE (LULI) (400fs-600ps, 1053nm) pour mettre en place une méthodologie basée sur un pendule balistique permettant d'estimer Cm. Des diagnostics performants (PDV, déviation angulaire, mesures d'absorption) ont été couplés. Dans la plage de fonctionnement des durées d'impulsion, cette approche hybride a été validée notamment par la confrontation des réponses entre diagnostics pour une variété de matériaux représentatifs des structures spatiales. L’empreinte de l’interaction laser est également observée post-choc par analyse microstructurale

On the performance of high power pulsed repeated laser irradiation for spatial structures propulsion

International audienceChanging debris orbits using High Power Pulsed Laser Interaction finds interest in the Low-Earth Orbit (LEO) due to space debris congestion. Laser facilities allowing both high energy and repetition rate of a short pulsed irradiation become available as provided by the high power HILASE beamline facility (Prague, CZ) with BIVOJ (100J, 10ns, 10Hz, 1030nm). In order to illustrate such an application, originally Crookes radiometer concept was adapted to quantify the efficiency of repeated laser shots in increasing rotating speed according to laser matter interaction. Various materials, from model to space applicative materials, allowed to estimate the material response with various irradiation characteristics (single shots vs. repeated shots). Matter behaviors (ablation, cratering, spallation, perforation) bracketed the laser conditions suitable in the perspective of laser propulsion with limited creation of extra debris or irradiated structures damages. Next is to strengthen the robustness of the simulation/experiment dialog to use simulation as a pre- design tool for laser space propulsion

On the performance of high power pulsed repeated laser irradiation for spatial structures propulsion

International audienceChanging debris orbits using High Power Pulsed Laser Interaction finds interest in the Low-Earth Orbit (LEO) due to space debris congestion. Laser facilities allowing both high energy and repetition rate of a short pulsed irradiation become available as provided by the high power HILASE beamline facility (Prague, CZ) with BIVOJ (100J, 10ns, 10Hz, 1030nm). In order to illustrate such an application, originally Crookes radiometer concept was adapted to quantify the efficiency of repeated laser shots in increasing rotating speed according to laser matter interaction. Various materials, from model to space applicative materials, allowed to estimate the material response with various irradiation characteristics (single shots vs. repeated shots). Matter behaviors (ablation, cratering, spallation, perforation) bracketed the laser conditions suitable in the perspective of laser propulsion with limited creation of extra debris or irradiated structures damages. Next is to strengthen the robustness of the simulation/experiment dialog to use simulation as a pre- design tool for laser space propulsion