High temperature microstructures of ternary Co-30wt.% Cr - based alloys over the [0 to 2.0wt.%] carbon range

International audienceThe Co-30wt.%-xC system was experimentally explored from x=0 to 2wt.%, by considering the stable microstructures at 1,000, 1,100 and 1,200°C, and the intervals of fusion. The strengthening potential and the refractoriness of several alloys belonging to this family were specified. Such simple alloys are able to display simultaneously a high amount of chromium for limiting hot corrosion, solidus temperatures as high as 1,300 °C and refractory carbides fractions that can reach 20 % in volume. Natures and fractions of carbides, and solidus temperatures were in good agreements with thermodynamic calculations. Inversely the measured liquidus temperatures were significantly higher than the calculated ones. In addition, thermodynamic modeling allowed to better interpret the disappearance of carbides due to oxidation at high temperature

Dynamic aspects of cerium dioxide sintering: HT-ESEM study of grain growth and pore elimination

International audienceSintering of CeO2 is studied in situ by high temperature scanning environmental microscopy (HT-ESEM) at T = 1400 °C. The morphological modifications of a single grains population are recorded for 6 h. Kinetic parameters are extracted from image series. The local grain growth determined from the single population studied in situ is compared to the general grain growth obtained by classical ex situ technique. Using HT-ESEM for sintering study is validated. The grain boundary velocities range between 0 and 5 μm h−1, with a mean value of about 1 μm h−1. The migration of the intragranular surface pores is described. Their velocities range between 0.4 and 1.2 μm h−1 and depend on pore diameters: the smaller the pore, the faster the pore velocity. The time required to fill a pore that arises at the sample surface is determined as a function of pore diameter. The time for pore elimination dependence with the pore diameters is also established

Microstructures at high temperature of Fe-30 wt.% Cr- x C Alloys with x varying from 0 to 2 wt.%

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Porte-échantillon à thermocouple intégré

Il s'agit d'un porte-échantillon incluant : un corps porte-échantillon (10) en matériau diélectrique réfractaire, un thermocouple (13) pour mesurer la température de l'échantillon, notamment lors d'un chauffage, formé de deux conducteurs (13.1, 13.2) de natures différentes, reliés en une jonction de mesure (13.0), le corps porte-échantillon comportant une surface d'accueil (11) sur laquelle est collée la jonction de mesure (13.0), cette surface d'accueil étant une surface d'accueil de l'échantillon, une gaine de protection (17) du corps porte-échantillon qui entoure le corps porte-échantillon en formant un rebord autour de la surface d'accueil (11) de manière à délimiter une cuvette (18) d'accueil de l'échantillon dont le fond est la surface d'accueil de l'échantillon (11). Application au contrôle de température d'échantillons

Development of an Integrated Thermocouple for the Accurate Sample Temperature Measurement During High Temperature Environmental Scanning Electron Microscopy (HT-ESEM) Experiments

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Sonoluminescence of Tb(III) at the Extended Solid–Liquid Interface

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Characterization of complex micellar systems by Scattering techniques (SAXS and SANS) and wet-Scanning Transmission Electron Microscopy (wet-STEM)

International audienceThe morphology of complex micellar assemblies is generally described using indirect methods such as small-angle X-ray scattering (SAXS) or small angle neutron scattering (SANS) that can yield to ambiguous descriptions of the nano-objects when the sample contains multiple structures or completely unknown structures. We herein propose to directly observe the nano-objects formed in P123 pluronic solutions (with and without rare-earth element-REE) using wet-Scanning Transmission Electron Microscopy (wet-STEM) and to compare the results with sample descriptions derived from SAXS and SANS measurements. The results obtained by the different analytical techniques are consistent. Each analytical method provides complementary information that allows the internal structure of the objects, their compositions and their mutual interactions to be described precisely. The main contributions of wet-STEM microscopy are to describe the nano-objects individually and, in particular, to show that the REE content can vary from 1 to 10 from one micelle to another, to observe the dynamics of the nano-objects in the liquid and to prove the coexistence of nano-objects with very different morphologies in the same system