A new approach to use marine robotic networks for ecosystem monitoring and management: The PLOME Project

4th Marine Imaging Workshop, 3-6 October 2022, Brest, FranceOur understanding of marine ecosystem functioning and processes relies on adequate spatio-temporal multiparametric monitoring procedures. Over the next 3 years, the Project PLOME (Platforms for Long-lasting Observation of Marine Ecosystems) will implement a spatially adaptive and autonomous network of easy-to-use benthic landers with dockable Autonomous Underwater Vehicles (AUVs)ñ This network will be used to intelligently video-monitor and map marine ecosystems and their environment from coastal to deep-sea areas. All platforms will be connected via acoustic or optical communication and will operate over periods of weeks to months with real-time supervision. Stations will provide continuous and intensive temporal observations, while dockable AUVs (with battery recharge and data downloading capability) will provide intensive measurements at various spatial scales, using intelligent and adaptive trajectories to explore surrounding areas. Biological, geochemical and oceanographic data will be generated by an array of sensors including acoustic receivers and cameras. Images will be processed in real-time for species classification and tracking, using advanced data analysis and Deep Learning techniques. Metadata will be communicated between landers and AUVs and transmitted opportunistically whenever an Unmanned Surface Vehicle (USV) connects the platform via aerial communications (i.e. GSM and satellite communications, depending on form distance to shore). The unattended operation will also be possible with an innovation of pop-up buoys that will allow data transfer to the surface from landers and UAVs to be relayed once the pop-up buoys reach the surface. Complex ecological indicators for ecosystem management will be computed from the collected data, by applying advanced computer vision techniques to classify, count and size individuals in video images and to generate multimodal maps of the seabed. A pipeline for automated data treatment will be tailored for multiparametric analyses to derive cause-effect relationships between biological variables and the physical habitatsPeer reviewe

Evolution des nano-oxydes et de la microstructure au cours du procédé de fabrication d'aciers renforcés par dispersion d'oxydes

Oxide Dispersion Strengthened (ODS) steels with a Fe-Cr matrix are of great interest in the development of generation IV fission nuclear power plants as a fuel cladding material. These materials, elaborated by powder metallurgy, include a high density of Y-Ti-O oxide precipitates of a few nm, providing the main contribution to the ODS steels strength. During the fabrication process, powders of Fe-Cr steel, Y2O3 and TiH2 are milled together to obtain a super-saturated solution of Y, Ti and O, otherwise insoluble in Fe. The obtained powder is subsequently processed by Hot Extrusion or Hot Isostatic Pressing around 1100℃. This induces the precipitation of Y-Ti-O and leads to a fully dense steel with finely dispersed nano-oxides in high density, extremely stable even at very high temperature. Moreover, the complex microstructure induced by the milling stage, including high density of dislocations and very small grain size, also evolve during the heating, in an intricate ways with the evolution of the nano-oxides that act as strong pinning points for both grain boundaries and dislocations. This features leads to abnormal grain growth (significant growth of some grains, while others remain stable) and therefore a bimodal grain size after consolidation.The aim of this thesis is to characterize both kinetics and chemical evolution of the nano-oxides during the fabrication process of these steels, as well as the grain microstructure evolution, which are still misunderstood. Such experimental characterization would be invaluable to further control the fabrication process and improve available model of the ODS precipitation kinetics. For this purpose, cold pressed specimens from as-milled powder were prepared (in order to achieve dense specimens without precipitation) and observed by means of various in-situ or ex-situ techniques. In particular, in-situ Small Angle X-ray Scattering measurements were performed during the heating until 1100℃ to measure the precipitation kinetics of several ODS grades. The chemistry and structure of nano-oxides were assessed thanks to anomalous SAXS at Y (performed in-situ) and Ti (ex-situ) edges, ex-situ small angle neutron scattering and atom probe tomography. Then, the grain microstructure was monitored by in-situ X-ray diffraction.These characterizations allow to describe the whole kinetics of purely ferritic ODS, ferritic / martensitic ODS and ODS strengthened with variation of the strengthening powders. In particular, this study highlights a non-homogeneous as-milled stage with clusters containing Y, O and Ti in lesser extent. These clusters evolve in chemistry and structure until reaching a stable structure and stoichiometry, revealed to be Y2Ti2O7 pyrochlore and Y2TiO5 orthorhombic depending on the ODS steel grade. Moreover, a kinetic modification induced by the in temperature phase transformation of the matrix in the ferritic / martensitic ODS (increasing the growth and coarsening rate) was observed. Correlation between nano-oxide and the grain microstructure evolutions were performed and help in the comprehension of the abnormal grain growth temperature and final grain morphology, from one ODS grade to another. Finally, comparisons of the precipitation simulations with experimental data allow to get more insights on the nano-oxides properties.Les aciers renforcés par dispersion d’oxydes (ODS pour Oxide Dispersion Strengthened) sont des matériaux candidats pour leur utilisation comme gainage du combustible pour des centrales nucléaires de génération IV. Dans ces aciers, une dispersion de nano-oxydes Y-Ti-O à l’origine de l’essentiel des propriétés mécaniques de l’alliage, est incorporée dans une matrice par métallurgie des poudres. Pendant ce procédé, une poudre d’acier Fe-Cr est broyée avec une poudre d’Y2O3 et une poudre de TiH2, afin de mettre en solution l’Y, le Ti et l’O, autrement immiscible dans la matrice. Le broyage induit aussi une microstructure de très petits grains avec une forte densité de dislocations. La poudre obtenue est ensuite consolidée par filage à chaud ou compaction isostatique à chaud à une température de 1100℃. Cette étape induit la précipitation des nano-oxydes, finement dispersés dans la matrice, en forte densité numérique et extrêmement stables à haute température. La microstructure évolue aussi pendant le recuit, de façon concomitante à l’évolution des nano-oxydes, qui agissent comme points d’ancrage pour les joints de grains et les dislocations. Ceci mène à un phénomène de croissance anormale des grains (croissance importante de certains grains seulement), et à une répartition de taille de grains bimodale après consolidation. L’objectif de cette thèse est de caractériser la cinétique et les évolutions de chimie des nano-oxydes, ainsi que les évolutions de la microstructure granulaire, pendant le procédé de fabrication, qui sont encore mal compris. Ces résultats sont cruciaux pour la maitrise du procédé de fabrication des aciers ODS, et représentent un jeu de données unique pour le développement de simulations de précipitation.Ainsi, des échantillons de poudres après broyage ont été compactés à froid, afin de les densifier sans induire la précipitation des nano-oxydes. Ces échantillons ont été ensuite caractérisés au cours du traitement thermique de consolidation. La cinétique de précipitation a été mesurée sur plusieurs nuances d’aciers ODS par diffusion de rayons-X aux petits angles (SAXS pour Small Angle X-ray Scattering) in-situ pendant le traitement thermique jusqu’à 1100℃. Pour caractériser les évolutions de chimie et de structure des nano-oxydes, des mesures de SAXS anomales au seuil de l’Y (in-situ), au seuil du Ti (ex-situ), de diffusion de neutrons aux petits angles et de sonde atomique tomographique ont été réalisées. Finalement, l’évolution de la microstructure granulaire a été caractérisée par diffraction des rayons-X in-situ.Ces caractérisations ont été réalisées sur des aciers ODS ferritiques et ferritiques / martensitiques, ainsi que sur des aciers ODS comportant des variations sur les propriétés des renforts. En particulier, la présence d’amas de très petite taille contenant de l’Y, de l’O et du Ti dans une moindre mesure a été constatée dès la condition post-broyage. Ces amas, évoluent en chimie et en structure jusqu’à devenir des nano-oxydes stables, Y2Ti2O7 pyrochlore et Y2TiO5 orthorhombique, dans des proportions variables suivant les nuances. De plus, une augmentation de la vitesse de croissance et de coalescence a été observée lors du changement de phase de la matrice des ODS ferritiques / martensitiques. La comparaison entre les résultats de cinétique de précipitation et de microstructure granulaire a permis la compréhension des températures de croissance anormale des grains, suivant la nuance considérée. Finalement, les comparaisons des simulations de précipitation avec les résultats expérimentaux ont permis d’obtenir de nouveaux éléments de compréhension des mécanismes de précipitations

Nano-oxides and microstructural evolutions of oxide dispersion strengthened steels throughout their fabrication process

Les aciers renforcés par dispersion d’oxydes (ODS pour Oxide Dispersion Strengthened) sont des matériaux candidats pour leur utilisation comme gainage du combustible pour des centrales nucléaires de génération IV. Dans ces aciers, une dispersion de nano-oxydes Y-Ti-O à l’origine de l’essentiel des propriétés mécaniques de l’alliage, est incorporée dans une matrice par métallurgie des poudres. Pendant ce procédé, une poudre d’acier Fe-Cr est broyée avec une poudre d’Y2O3 et une poudre de TiH2, afin de mettre en solution l’Y, le Ti et l’O, autrement immiscible dans la matrice. Le broyage induit aussi une microstructure de très petits grains avec une forte densité de dislocations. La poudre obtenue est ensuite consolidée par filage à chaud ou compaction isostatique à chaud à une température de 1100℃. Cette étape induit la précipitation des nano-oxydes, finement dispersés dans la matrice, en forte densité numérique et extrêmement stables à haute température. La microstructure évolue aussi pendant le recuit, de façon concomitante à l’évolution des nano-oxydes, qui agissent comme points d’ancrage pour les joints de grains et les dislocations. Ceci mène à un phénomène de croissance anormale des grains (croissance importante de certains grains seulement), et à une répartition de taille de grains bimodale après consolidation. L’objectif de cette thèse est de caractériser la cinétique et les évolutions de chimie des nano-oxydes, ainsi que les évolutions de la microstructure granulaire, pendant le procédé de fabrication, qui sont encore mal compris. Ces résultats sont cruciaux pour la maitrise du procédé de fabrication des aciers ODS, et représentent un jeu de données unique pour le développement de simulations de précipitation.Ainsi, des échantillons de poudres après broyage ont été compactés à froid, afin de les densifier sans induire la précipitation des nano-oxydes. Ces échantillons ont été ensuite caractérisés au cours du traitement thermique de consolidation. La cinétique de précipitation a été mesurée sur plusieurs nuances d’aciers ODS par diffusion de rayons-X aux petits angles (SAXS pour Small Angle X-ray Scattering) in-situ pendant le traitement thermique jusqu’à 1100℃. Pour caractériser les évolutions de chimie et de structure des nano-oxydes, des mesures de SAXS anomales au seuil de l’Y (in-situ), au seuil du Ti (ex-situ), de diffusion de neutrons aux petits angles et de sonde atomique tomographique ont été réalisées. Finalement, l’évolution de la microstructure granulaire a été caractérisée par diffraction des rayons-X in-situ.Ces caractérisations ont été réalisées sur des aciers ODS ferritiques et ferritiques / martensitiques, ainsi que sur des aciers ODS comportant des variations sur les propriétés des renforts. En particulier, la présence d’amas de très petite taille contenant de l’Y, de l’O et du Ti dans une moindre mesure a été constatée dès la condition post-broyage. Ces amas, évoluent en chimie et en structure jusqu’à devenir des nano-oxydes stables, Y2Ti2O7 pyrochlore et Y2TiO5 orthorhombique, dans des proportions variables suivant les nuances. De plus, une augmentation de la vitesse de croissance et de coalescence a été observée lors du changement de phase de la matrice des ODS ferritiques / martensitiques. La comparaison entre les résultats de cinétique de précipitation et de microstructure granulaire a permis la compréhension des températures de croissance anormale des grains, suivant la nuance considérée. Finalement, les comparaisons des simulations de précipitation avec les résultats expérimentaux ont permis d’obtenir de nouveaux éléments de compréhension des mécanismes de précipitations.Oxide Dispersion Strengthened (ODS) steels with a Fe-Cr matrix are of great interest in the development of generation IV fission nuclear power plants as a fuel cladding material. These materials, elaborated by powder metallurgy, include a high density of Y-Ti-O oxide precipitates of a few nm, providing the main contribution to the ODS steels strength. During the fabrication process, powders of Fe-Cr steel, Y2O3 and TiH2 are milled together to obtain a super-saturated solution of Y, Ti and O, otherwise insoluble in Fe. The obtained powder is subsequently processed by Hot Extrusion or Hot Isostatic Pressing around 1100℃. This induces the precipitation of Y-Ti-O and leads to a fully dense steel with finely dispersed nano-oxides in high density, extremely stable even at very high temperature. Moreover, the complex microstructure induced by the milling stage, including high density of dislocations and very small grain size, also evolve during the heating, in an intricate ways with the evolution of the nano-oxides that act as strong pinning points for both grain boundaries and dislocations. This features leads to abnormal grain growth (significant growth of some grains, while others remain stable) and therefore a bimodal grain size after consolidation.The aim of this thesis is to characterize both kinetics and chemical evolution of the nano-oxides during the fabrication process of these steels, as well as the grain microstructure evolution, which are still misunderstood. Such experimental characterization would be invaluable to further control the fabrication process and improve available model of the ODS precipitation kinetics. For this purpose, cold pressed specimens from as-milled powder were prepared (in order to achieve dense specimens without precipitation) and observed by means of various in-situ or ex-situ techniques. In particular, in-situ Small Angle X-ray Scattering measurements were performed during the heating until 1100℃ to measure the precipitation kinetics of several ODS grades. The chemistry and structure of nano-oxides were assessed thanks to anomalous SAXS at Y (performed in-situ) and Ti (ex-situ) edges, ex-situ small angle neutron scattering and atom probe tomography. Then, the grain microstructure was monitored by in-situ X-ray diffraction.These characterizations allow to describe the whole kinetics of purely ferritic ODS, ferritic / martensitic ODS and ODS strengthened with variation of the strengthening powders. In particular, this study highlights a non-homogeneous as-milled stage with clusters containing Y, O and Ti in lesser extent. These clusters evolve in chemistry and structure until reaching a stable structure and stoichiometry, revealed to be Y2Ti2O7 pyrochlore and Y2TiO5 orthorhombic depending on the ODS steel grade. Moreover, a kinetic modification induced by the in temperature phase transformation of the matrix in the ferritic / martensitic ODS (increasing the growth and coarsening rate) was observed. Correlation between nano-oxide and the grain microstructure evolutions were performed and help in the comprehension of the abnormal grain growth temperature and final grain morphology, from one ODS grade to another. Finally, comparisons of the precipitation simulations with experimental data allow to get more insights on the nano-oxides properties

Overview of sample enironments for research use at the PETRA III Swedish Materials Science beamline

This technical report presents an overview of sample environments which are usable at the PETRA III Swedish Materials Science beamline (potentially requiring arrangement or development of the beamline layout). Alongside the description of each sample environment, illustrative materials science studies are presented that exemplify the use of these sample environments for in situ and/or in operando measurements.  The sample environments are catalogued according to the research application areas, which are categorised as Thermal treatments, Electrochemistry, Catalysis, Thin films, Mechanical response of materials and Levitation. Such cataloguing means that researchers can now start their search for relevant sample environments by looking up a relevant research application area. Citations and links to specifications, published research cases and the organisation that is responsible for a given sample environment, are also provided as a basis for researchers to proceed with their research planning.QC 20230328</p

Inventory of data reduction and analysis software used in high-energy X-ray research at PETRA III : WAXS, SAXS, GIWAXS, GISAXS, PDF

This inventory catalogs the software programs that have proven to be useful to the Swedish research community that conducts research at the PETRA III synchrotron, including the PETRA III Swedish Materials Science beamline. Based on publications from 2018, the inventory categorizes the various software programs used in research as either data reduction software for 2D area detector X-ray scattering images or data analysis software for WAXS, SAXS, GIWAXS, GISAXS, and PDF. Each software program has a short description of its functionality, a note of its developer, links to the original publication describing the scientific method that the software is based upon, as well as the site for downloading the software program. QC 20220902Center for X-rays in Swedish Materials Scienc

Effect of ultrasonic shot peening on microstructure and properties of 301SS

International audienceUltrasonic shot peening (USP) is an efficient way to improve the mechanical behavior of 301 stainless steel by inducing severe plastic deformation on its surface. However, this surface treatment induces complex microstructural evolutions, such as grain refinement and phase transformation. Therefore, a better understanding of those evolution mechanisms is critical to optimize the USP treatment. In this work, we rely on various electron microscope observations to compare a specimen before and after a 5-min shot peening treatment. We found an affected layer of ~450 µm with a significant increase in hardness on the top surface by a factor of 2.7 times. Inside this layer, we noticed a nanoscale grain layer of ~130 µm, the most strengthened layer, containing nanoscale grain of α′, with few γ and a large amount of low angle grain boundaries on the topmost. Afterward, we observed coarse grains with deformation twins, which seem to be a preferential site for martensite nucleation, especially at their intersection, and a high density of dislocation. We also conducted experiments to determine a possible scenario for the microstructural evolution, based on those observations

Overview of sample enironments for research use at the PETRA III Swedish Materials Science beamline

This technical report presents an overview of sample environments which are usable at the PETRA III Swedish Materials Science beamline (potentially requiring arrangement or development of the beamline layout). Alongside the description of each sample environment, illustrative materials science studies are presented that exemplify the use of these sample environments for in situ and/or in operando measurements.  The sample environments are catalogued according to the research application areas, which are categorised as Thermal treatments, Electrochemistry, Catalysis, Thin films, Mechanical response of materials and Levitation. Such cataloguing means that researchers can now start their search for relevant sample environments by looking up a relevant research application area. Citations and links to specifications, published research cases and the organisation that is responsible for a given sample environment, are also provided as a basis for researchers to proceed with their research planning.QC 20230328</p

Inventory of data reduction and analysis software used in high-energy X-ray research at PETRA III : WAXS, SAXS, GIWAXS, GISAXS, PDF

This inventory catalogs the software programs that have proven to be useful to the Swedish research community that conducts research at the PETRA III synchrotron, including the PETRA III Swedish Materials Science beamline. Based on publications from 2018, the inventory categorizes the various software programs used in research as either data reduction software for 2D area detector X-ray scattering images or data analysis software for WAXS, SAXS, GIWAXS, GISAXS, and PDF. Each software program has a short description of its functionality, a note of its developer, links to the original publication describing the scientific method that the software is based upon, as well as the site for downloading the software program. QC 20220902Center for X-rays in Swedish Materials Scienc

Precipitation kinetics of oxide dispersion strengthened steels for their application as cladding material in Gen. IV power plants

International audienc

Computational thermodynamics and kinetics-guided re-engineering of a high-performance tool steel

Targeting to obtain fine dispersions of nanoscale precipitates to enhance the mechanical properties of a high-performance tool steel, re-engineering of the alloy composition and heat treatment was guided by computational thermodynamics and kinetics. A prototype alloy was prepared using the designed chemistry and heat treatment. Thereafter, advanced microstructural characterization and mechanical testing confirmed the successful design to reach a high number density of (V, Mo)C precipitates with an average diameter of about 5 nm in the peak-hardened condition, after tempering the martensite at 600 °C for 2h