Ce travail a été soutenu par la NASA subvention NNX11AC68G et la Carnegie Institution de Washington. Je remercie Chi Zhang pour son aide dans la collecte de données. Je remercie également Anat Shahar et Valerie Hillgren les avis utiles de ce manuscrit.

Une. Préparer le matériel de départ et Chambres d&#39;exemples <ol><li> Préparer deux types de matières de départ, (1) un mélange d&#39;olivine de silicate naturel et la poudre de fer métallique à 10% en poids de soufre (métal / des ratios de silicate allant de 4 à 30% en poids) pour la simulation de la percolation de l&#39;alliage de fonte liquide dans une matrice de silicate solide au cours de la formation du noyau initial d&#39;un petit corps planétaire, et (2) un mélange homogène de fer pur finement la masse et le sulfure de fer pour la détermination du planétaire cristallisation d&#39;âme intérieure. </li><li> Broyez les matières premières à poudre mélangée amende en vertu de l&#39;éthanol dans un mortier en agate pendant une heure et séché à 100 ° C. </li><li> Charger la matière de départ en un fritté de MgO ou Al 2 O 3 capsule (typiquement de 1,5 mm de diamètre et d&#39;une longueur de 1,5), puis placer dans un assemblage de cellule à haute pression pour les expériences multi-enclume. </li><li> Chargez le mélange Fe-FeS dans une petite chambre d&#39;échantillon (typiquement 100 m de diamètre et 25 &amp; #181; m d&#39;épaisseur) percé dans un joint de rhénium preindented pour les expériences laser de chauffage dans la cellule de type diamant enclume. Sandwich mélange Fe-FeS entre les couches de NaCl qui servent comme isolants thermiques. </li></ol> 2. Des expériences à haute pression et haute température dans l&#39;appareil multi-enclume <ol><li> L&#39;assemblage de cellule à haute pression multi-enclumes est constitué d&#39;un octaèdre MgO en tant que moyen de pression, une douille de ZrO 2 en tant que l&#39;isolant thermique, et un rhénium ou du graphite cylindrique chauffage. L&#39;échantillon capsule s&#39;adapte à l&#39;intérieur du chauffe-eau. Un thermocouple de type C est introduit dans la chambre de mesure pour déterminer la température de l&#39;échantillon. </li><li> Placez l&#39;ensemble à haute pression dans un appareil à haute pression multi-enclume pour la pressurisation. </li><li> Appareil multi-enclumes est constitué d&#39;une presse hydraulique de 1500 tonnes et un module de pression, qui contient une bague de retenue avec six coins de poussée amovible formant une cavité cubique au centre 15. La cavité cubique houses huit cubes de carbure de tungstène avec coins tronqués. Les cubes tronqués qui convergent sur l&#39;ensemble de cellule d&#39;octaèdre, sont séparés les uns des autres par des joints d&#39;étanchéité compressibles. Le vérin hydraulique transmet la force efficace sur l&#39;ensemble de l&#39;échantillon par une figure 1 illustre la procédure expérimentale de l&#39;expérience multi-enclume en deux étapes de configuration de l&#39;enclume.. </li><li> Mettre sous pression l&#39;échantillon à une pression cible entre 2-27 GPa à la température ambiante sur la base de point fixe courbe d&#39;étalonnage de la pression 16, puis le chauffer aux températures expérimentales jusqu&#39;à 2300 ° C par chauffage par résistance électrique; maintenir l&#39;expérience à température constante pour la durée de l&#39;expérience, et le mettre hors tension pour éteindre l&#39;échantillon à la température ambiante à la fin de l&#39;expérience. </li><li> Relâchez lentement la pression en ouvrant la vanne de l&#39;huile hydraulique et de récupérer la charge expérimentale. </li></ol> 3. Les expériences laser-chauffage dans leDiamond-enclume portable <ol><li> Pression dans une cellule diamant enclume est généré entre deux monocristallines enclumes de diamants de qualité gemme (environ 0,25 carats chacun). Nous utilisons une cellule diamant enclume symétrique pour conduire les enclumes opposées parfaitement alignés avec un système piston-cylindre. La cellule est capable de générer des pressions qui correspondent aux conditions de pression du noyau de la Terre 17. Une température élevée est obtenue par chauffage au laser dans la cellule diamant-enclume. On utilise un système à l&#39;avance Photon Source (APS), qui est basé sur une technique de chauffage à double face laser et se compose de deux lasers à fibre, optique pour chauffer l&#39;échantillon à partir des deux côtés, et deux systèmes spectroradiométriques pour les mesures de température des deux côtés 18. Le système est conçu pour générer un spot de chauffage de grande taille (25 um de diamètre), de minimiser les gradients de température de l&#39;échantillon à la fois radialement et axialement dans la cellule à enclume de diamant, et de maximiser la stabilité de chauffage. Figure 2 montre schématiquements de la configuration expérimentale pour l&#39;expérience laser de chauffage dans la cellule de type diamant enclume avec une image de la tache laser de chauffage. </li><li> Aligner les enclumes de diamant avec 300 um culets preindent et un joint de rhénium à une épaisseur de 30 um à partir d&#39;une épaisseur initiale de 250 um. </li><li> Percer un trou dans le joint preindented avec un diamètre de 120 um au centre, et de charger l&#39;échantillon dans le trou. </li><li> Mettre sous pression l&#39;échantillon à une pression de consigne à la température ambiante, et ensuite chauffer l&#39;échantillon par augmentation de la puissance du laser tout en prenant des mesures de température in situ et en rayons X des mesures de diffraction à l&#39;installation de synchrotron. </li><li> Couper l&#39;alimentation du laser pour étancher l&#39;échantillon lors de la fusion partielle est détectée par un changement dans le rayonnement thermique et à partir du motif de diffraction. </li><li> Récupérer l&#39;échantillon chauffé pour la caractérisation ex situ. </li></ol> 4. Récupération et analyse d&#39;échantillons <ol><li> MoUnt l&#39;échantillon multi-enclume récupérées dans résine époxy et de polir la surface à l&#39;aide d&#39;une suite de poudre de diamant de grain de 150 pm à 0,25 pm. </li><li> Carbon-enduire la surface de l&#39;échantillon et la charger dans la chambre d&#39;un instrument de traverse Zeiss Auriga FIB / SEM (figure 3A) pour l&#39;analyse de l&#39;échantillon. </li><li> Aligner l&#39;échantillon à un point coïncidant de la FIB et SEM à une distance de travail de 5 mm (figure 3B), puis premill l&#39;échantillon pour exposer un volume de 15 x 20 x 20 um 3 (figure 3C). </li><li> Prenez des images MEB à un intervalle de 25 nm en utilisant la tranche et fonction de vue sur l&#39;instrument Zeiss Auriga FIB / SEM (enregistrer automatiquement une série d&#39;images après le broyage faisceau d&#39;ions avec une résolution d&#39;image typique d&#39;environ 35 nm). </li><li> les fichiers de données d&#39;image d&#39;entrée à un logiciel de visualisation et de reconstruire des images en 3D pour visualiser la distribution de masse fondue et de la connectivité dans l&#39;échantillon éteint (Figure 3D). </li></ol>

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Aucun conflit d&#39;intérêt déclaré.

Les techniques pour les expériences multi-enclume sont bien établies, de génération de pression et de température pendant une longue période de temps de fonctionnement stable et pour produire le volume relativement important de l&#39;échantillon. Il est un outil puissant pour simuler les processus intérieurs de planètes, en particulier pour les expériences, tels que la fonte percolation, qui nécessitent un certain volume de l&#39;échantillon. La limitation est la pression maximale possible, jusqu&#39;à 27 G...

Les planètes telluriques comme la Terre, Vénus, Mars et Mercure sont des corps planétaires dissociés, d&#39;un manteau de silicate et un noyau métallique. Le modèle de la formation des planètes moderne suggère que les planètes terrestres ont été formés par des collisions d&#39;embryons planétaires-Lune-Mars à taille issues de kilomètres taille ou plus planétésimaux par des interactions gravitationnelles 1-2. Les planétésimaux ont probablement déjà différenciées fois les alliages métalliques en fer atteint la température de fusion en raison de chauffage à partir de sources telles que la désintégration radioactive des isotopes de courte durée tels que 26 Al et 60 Fe, l&#39;impact, et la libération de l&#39;énergie potentielle 3. Il est important de comprendre la façon dont le métal liquide percolé à travers une matrice de silicate au cours de la différenciation précoce. différenciation de la planète pourrait passer par efficace séparation liquide-liquide ou par infiltration de métal liquide dans une matrice de silicate solide, en fonction dede la taille et de la température intérieure des corps planétaires. La percolation de métal liquide dans la matrice de silicate solide est probablement un processus dominant dans la différenciation initiale lorsque la température n&#39;est pas assez élevée pour faire fondre la totalité du corps planétaire. L&#39;efficacité de la percolation dépend de l&#39;angle dièdre, déterminées par les énergies interfaciales des interfaces solide-solide et solide-liquide. Nous pouvons simuler ce processus en laboratoire en réalisant des expériences à haute pression et à haute température d&#39;un mélange d&#39;alliage de fer et de silicate. Des études récentes ont étudié 4-7 la capacité de mouillage des alliages de fer liquide dans une matrice de silicate solide à haute pression et de la température. Ils ont utilisé une méthode classique pour mesurer les distributions de fréquences relatives des angles dièdres apparentes entre le métal liquide refroidi et grains de silicate sur les sections polies pour la détermination de la véritable dièdre. La méthode classique donne relativement importante uncertainties dans l&#39;angle dièdre mesurée et biais possibles selon les statistiques de l&#39;échantillonnage. Ici, nous présentons une nouvelle technique d&#39;imagerie pour visualiser la distribution de métal liquide dans la matrice silicate en trois dimensions (3D) par combinaison de FIB fraisage et haute résolution à émission de champ SEM imagerie. La nouvelle technique d&#39;imagerie permet une détermination précise de l&#39;angle dièdre et mesure quantitative de la fraction volumique et la connectivité de la phase liquide. Le noyau de la Terre a été formée en un temps relativement court (&lt;100 millions d&#39;années) 8, vraisemblablement dans un état ​​liquide à son histoire ancienne. Mars et Mercure ont également noyaux liquides à base de déformation de marée solaire de Mars Global Surveyor données de suivi de la radio et 9 modèles radar de tavelures liés à la rotation planétaire 10, respectivement. Modèles d&#39;évolution thermique et des expériences de fusion à haute pression sur les matériaux de base soutiennent en outre un noyau martien liquide11-12. Des données récentes de l&#39;engin spatial Messenger fournissent une preuve supplémentaire d&#39;un noyau liquide de Mercure 13. Même la petite lune a probablement un petit noyau liquide à base d&#39;une nouvelle analyse récente de Appollo sismogrammes lunaires 14. Noyaux planétaires liquides sont compatibles avec haute énergie d&#39;accrétion au stade précoce de la formation des planètes. Un refroidissement ultérieur peut conduire à la formation de noyau interne solide pour certaines planètes. Les données sismiques ont révélé que la Terre se compose d&#39;un noyau externe liquide et un noyau interne solide. La formation du noyau interne a des implications importantes pour la dynamique du noyau entraînée par convections thermiques et de composition et la génération du champ magnétique de la planète. La solidification du noyau interne est contrôlée par la température de fusion des matériaux d&#39;âme et de l&#39;évolution thermique de l&#39;âme. Formation de noyau planètes terrestres partagé chemins d&#39;accrétion similaires et la composition chimique des noyaux est considéré à be dominé par le fer avec environ 10% de poids d&#39;éléments d&#39;éclairage tels que le soufre (S), le silicium (Si), l&#39;oxygène (O), le carbone (C) et hydrogène (H) 15. Il est essentiel d&#39;avoir une connaissance des relations de fusion dans les systèmes pertinents à l&#39;âme, comme Fe-FeS, Fe-C, Fe-FeO, Fe-FeH et Fe-FeSiat haute pression, afin de comprendre la composition de les noyaux planétaires. Dans cette étude, nous allons démontrer les expériences menées dans le dispositif multi-enclume et cellule enclume de diamant, mimant les conditions des noyaux planétaires. Les expériences fournissent des informations sur la séquence de la cristallisation et la séparation entre l&#39;élément métallique solide et liquide, ce qui conduit à une meilleure compréhension des exigences de la cristallisation de l&#39;âme interne et la distribution des éléments lumineux entre le noyau interne et le noyau cristallin liquide à l&#39;extérieur. Pour étendre les relations de fusion à des pressions très élevées, nous avons développé de nouvelles techniques pour analyser les échantillons trempés récupérés laser chauffée diamant-unexpériences sur les cellules nvil. Avec une précision FIB fraisage de la tache laser de chauffage, nous déterminons la fusion en utilisant trempe critères de texture de représentation à haute résolution SEM et analyse chimique quantitative avec un détecteur de dérive de silicium à une résolution spatiale inférieure au micron. Nous présentons ici deux séries d&#39;expériences pour imiter la formation de base planétaire par percolation de métallique fondre dans la matrice silicate pendant accrétion début et la cristallisation de noyau interne par refroidissement ultérieur. La simulation vise à comprendre les deux processus importants au cours de l&#39;évolution de noyau planétaire.

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			<td class="xl63" height="43" style="height:32.25pt;width:66pt" width="88">Multi-anvil apparatus</td>
			<td class="xl63" style="border-left:none;width:66pt" width="88">Geophysical Lab</td>
			<td class="xl63" style="border-left:none;width:66pt" width="88">Home Builder</td>
			<td class="xl63" style="border-left:none;width:66pt" width="88"> </td>
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		<tr height="43" style="height:32.25pt">
			<td class="xl63" height="43" style="height:32.25pt;border-top:none;
 width:66pt" width="88">Diamond-anvil cell</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Geophysical Lab</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Home Builder</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88"> </td>
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		<tr height="64" style="height:48.0pt">
			<td class="xl63" height="64" style="height:48.0pt;border-top:none;
 width:66pt" width="88">Laser-heating system</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">APS GSECARS</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Designed by beamline staff</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88"> Public beamline</td>
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			<td class="xl63" height="43" style="height:32.25pt;border-top:none;
 width:66pt" width="88">FIB/SEM Crossbeam</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Carl Zeiss Ltd.</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Auriga</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88"> </td>
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			<td class="xl63" height="64" style="height:48.0pt;border-top:none;
 width:66pt" width="88">Avizo 3D software</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">VSG</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88">Fire for materials science</td>
			<td class="xl63" style="border-top:none;border-left:none;width:66pt" width="88"> </td>
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simulation of the planetary interior differentiation processes in the laboratory

A l&#39;intérieur planétaire est dans des conditions de haute pression et à haute température et il a une structure en couches. Il ya deux processus importants qui ont conduit à cette structure en couches, (1) la percolation de métal liquide dans une matrice de silicate solide par la différenciation de la planète, et (2) intérieure cristallisation de base par planète refroidissement subséquent. Nous menons des expériences à haute pression et à haute température pour simuler les processus dans le laboratoire. Formation de noyau planétaire percolation dépend de l&#39;efficacité de la percolation à l&#39;état fondu, qui est commandé par le dièdre (mouillant) angle. La simulation de percolation comprend le chauffage de l&#39;échantillon à une pression élevée à une température cible à laquelle l&#39;alliage fer-soufre est fondu alors que le silicate reste solide, et ensuite la détermination de l&#39;angle réel de dièdre pour évaluer le style de la migration de liquide dans une matrice cristalline de visualisation 3D. Le rendu de volume 3D est obtenue par tranchage de l&#39;échantillon récupéré avec un faisceau focalisé d&#39;ions (FIB) et tal&#39;image roi SEM de chaque tranche avec un instrument traverse FIB / SEM. La deuxième série d&#39;expériences est destinée à comprendre la distribution de la cristallisation et de l&#39;élément noyau intérieur entre le noyau externe liquide et solide noyau interne par la détermination de la température de fusion et l&#39;élément de séparation sous haute pression. Les expériences de fusion sont effectuées dans le dispositif multi-enclume jusqu&#39;à 27 GPa et étendus à une pression plus élevée dans la cellule de type diamant enclume avec laser de chauffage. Nous avons développé des techniques pour récupérer les petits échantillons chauffés par FIB précision de fraisage et obtenir des images à haute résolution de la tache laser-chauffée qui montrent texture fondante à haute pression. En analysant les compositions chimiques du liquide coexistante et des phases solides, on détermine avec précision la courbe de liquidus, donnant des données nécessaires à la compréhension du processus de cristallisation de l&#39;âme interne.

Nous avons réalisé une série d&#39;expériences en utilisant des mélanges de San Carlos olivine et Fe-FeS alliage métallique avec différents rapports métal-silicate, en tant que matériaux de départ. La teneur en S du métal est de 10% en poids S. Ici, nous montrons des résultats représentatifs d&#39;expériences à haute pression effectuées à 6 GPa et 1800 ° C, en utilisant bien calibrés assemblages multi-enclume 15. Dans les conditions expérimentales, l&#39;alliage métallique Fe-FeS est comp...

Watch this Scientific Journal Video about Simulation of the Planetary Interior Differentiation Processes in the Laboratory at JoVE.com

Simulation of the Planetary Interior Differentiation Processes in the Laboratory

Les expériences à haute pression et à haute température décrits ici imitent les processus de différenciation intérieur de la planète. Les processus sont visualisées et mieux compris par imagerie à haute résolution en 3D et l&#39;analyse chimique quantitative.

Simulation de la différenciation planétaire Intérieur processus dans le laboratoire

A planetary interior is under high-pressure and high-temperature conditions and it has a layered structure. There are two important processes that led to ...

simulation-planetary-interior-differentiation-processes

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Engineering

11.5K vues.  Carnegie Institution of Washington.  Les expériences à haute pression et à haute température décrits ici imitent les processus de différenciation intérieur de la planète. Les processus sont visualisées et mieux compris par imagerie à haute résolution en 3D et l'analyse chimique quantitative. 

Vidéo: Simulation of the Planetary Interior Differentiation Processes in the Laboratory

Revealing Dynamic Processes of Materials in Liquids Using Liquid Cell Transmission Electron Microscopy

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted significant interests across the research fields of materials science, physics, chemistry and biology. The key enabling technology is a liquid cell. We fabricate liquid cells with thin viewing windows through a sequential microfabrication process, including silicon nitride membrane deposition, photolithographic patterning, wafer etching, cell bonding, etc. A liquid cell with the dimensions of a regular TEM grid can fit in any standard TEM sample holder. About 100 nanoliters reaction solution is loaded into the reservoirs and about 30 picoliters liquid is drawn into the viewing windows by capillary force. Subsequently, the cell is sealed and loaded into a microscope for in situ imaging. Inside the TEM, the electron beam goes through the thin liquid layer sandwiched between two silicon nitride membranes. Dynamic processes of nanoparticles in liquids, such as nucleation and growth of nanocrystals, diffusion and assembly of nanoparticles, etc., have been imaged in real time with sub-nanometer resolution. We have also applied this method to other research areas, e.g., imaging proteins in water. Liquid cell TEM is poised to play a major role in revealing dynamic processes of materials in their working environments. It may also bring high impact in the study of biological processes in their native environment.

We have developed a self-contained liquid cell, which allows imaging through liquids using a transmission electron microscope. Dynamic processes of nanoparticles in liquids can be revealed in real time with sub-nanometer resolution.

Révéler processus dynamiques des matériaux dans les liquides en utilisant un liquide Transmission Electron Microscopy cellulaire

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted ...

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Ingénierie

Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory1-4. This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range5,6. The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species&#8217; profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates7. The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles4. The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation of the observed large polycyclic aromatic hydrocarbons (PAHs).

Gas sampling from laboratory-scale flames with online analysis of all species by mass spectrometry is a powerful method to investigate the complex mixture of chemical compounds occurring during combustion processes. Coupled with tunable soft ionization via synchrotron-generated vacuum-ultraviolet radiation, this technique provides isomer-resolved information and potentially fragment-free mass spectra.

Les expériences de la flamme à l&#39;Advanced Light Source: nouvelles perspectives sur les processus d&#39;établissement de la suie

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics ...

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System.

We present a technique to achieve low-velocity to intermediate-velocity collisions between fragile dust aggregates in the laboratory. For this purpose, two vacuum drop-tower setups have been developed that allow collision velocities between &#60;0.01 and ~10 m/sec. The collision events are recorded by high-speed imaging.

Laboratoire baisse Towers pour la simulation expérimentale de collisions poussière globales dans le système solaire précoce

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust ...

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

Quantification des concentrations d&#39;hydrogène dans des surfaces et interfaces des couches et des matériaux en vrac par le biais de profils en profondeur avec l&#39;analyse de la réaction nucléaire

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With designs governed by the dynamic performance under human-induced loads, a strong demand exists for the verification and refinement of currently available load models. The present contribution uses a 3D inertial motion tracking technique for the characterization of the in-field pedestrian behavior. The technique is first tested in laboratory experiments with simultaneous registration of the corresponding ground reaction forces. The experiments include walking persons as well as rhythmical human activities such as jumping and bobbing. It is shown that the registered motion allows for the identification of the time variant pacing rate of the activity. Together with the weight of the person and the application of generalized force models available in literature, the identified time-variant pacing rate allows to characterize the human-induced loads. In addition, time synchronization among the wireless motion trackers allows identifying the synchronization rate among the participants. Subsequently, the technique is used on a real footbridge where both the motion of the persons and the induced structural vibrations are registered. It is shown how the characterized in-field pedestrian behavior can be applied to simulate the induced structural response. It is demonstrated that the in situ identified pacing rate and synchronization rate constitute an essential input for the simulation and verification of the human-induced loads. The main potential applications of the proposed methodology are the estimation of human-structure interaction phenomena and the development of suitable models for the correlation among pedestrians in real traffic conditions.

A protocol is presented for the characterization of the in-field pedestrian behavior and the simulation of the resulting structural response. Field-tests demonstrate that the in situ identified pacing rate and synchronization rate among the participants constitute an essential input for the simulation and verification of the human-induced loads.

Simulation des vibrations d&#39;origine humaine Basé sur l&#39;In-champ Piéton Comportement Caractérisé

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With ...

Knowledge Based Cloud FE Simulation of Sheet Metal Forming Processes

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques.
This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions.

The following paper presents a novel FE simulation technique (KBC-FE), which reduces computational cost by performing simulations on a cloud computing environment, through the application of individual modules. Moreover, it establishes a seamless collaborative network between world leading scientists, enabling the integration of cutting edge knowledge modules into FE simulations.

Sur la base de connaissances Simulation Couverture de FE Sheet Metal Forming Processes

The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the ...

Wicking Tests for Unidirectional Fabrics: Measurements of Capillary Parameters to Evaluate Capillary Pressure in Liquid Composite Molding Processes

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify their influence on void formation in composite parts. Wicking in a fibrous medium described by the Washburn equation was considered equivalent to a flow under the effect of capillary pressure according to the Darcy law. Experimental tests for the characterization of wicking were conducted with both carbon and flax fiber reinforcement. Quasi-unidirectional fabrics were then tested by means of a tensiometer to determine the morphological and wetting parameters along the fiber direction. The procedure was shown to be promising when the morphology of the fabric is unchanged during capillary wicking. In the case of carbon fabrics, the capillary pressure can be calculated. Flax fibers are sensitive to moisture sorption and swell in water. This phenomenon has to be taken into account to assess the wetting parameters. In order to make fibers less sensitive to water sorption, a thermal treatment was carried out on flax reinforcements. This treatment enhances fiber morphological stability and prevents swelling in water. It was shown that treated fabrics have a linear wicking trend similar to those found in carbon fabrics, allowing for the determination of capillary pressure.

An experimental method to measure geometrical parameters and the apparent advancing contact angles describing capillary wicking in unidirectional synthetic and natural fabrics is proposed. These parameters are mandatory for the determination of the capillary pressures that must be taken into account for liquid composite molding (LCM) applications.

Wicking Tests pour unidirectionnels Tissus: Mesures de Capillaire paramètres pour évaluer la pression capillaire dans les processus Liquid Composite Molding

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify ...

Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and nanocrystalline materials. The traditional techniques associated with scanning electron microscopy (SEM), such as electron backscatter diffraction (EBSD), do not possess the required spatial resolution due to the large interaction volume between the electrons from the beam and the atoms of the material. Transmission electron microscopy (TEM) has the required spatial resolution. However, due to a lack of automation in the analysis system, the rate of data acquisition is slow which limits the area of the specimen that can be characterized. This paper presents a new characterization technique, Transmission Kikuchi Diffraction (TKD), which enables the analysis of the microstructure of UFG and nanocrystalline materials using an SEM equipped with a standard EBSD system. The spatial resolution of this technique can reach 2 nm. This technique can be applied to a large range of materials that would be difficult to analyze using traditional EBSD. After presenting the experimental set up and describing the different steps necessary to realize a TKD analysis, examples of its use on metal alloys and minerals are shown to illustrate the resolution of the technique and its flexibility in term of material to be characterized.

This paper provides a detailed method to characterize the microstructure of ultra-fine grained and nanocrystalline materials using a scanning electron microscope equipped with a standard electron backscatter diffraction system. Metal alloys and minerals presenting refined microstructures are analyzed using this technique, showing the diversity of its possible applications.

Caractérisation des ultra-fine grainé et nanocristallins Matériaux Utilisation de la transmission Kikuchi Diffraction

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and ...

Processing of Bulk Nanocrystalline Metals at the US Army Research Laboratory

Given their potential for significant property improvements relative to their large grained counterparts, much work has been devoted to the continued development of nanocrystalline metals. Despite these efforts, the transition of these materials from the lab bench to actual applications has been blocked by the inability to produce large scale parts that retain the desired nanocrystalline microstructures. Following the development of a method proven to stabilize the nanosized grain structure to temperatures approaching that of the melting point for the given metal, the US Army Research Laboratory (ARL) has progressed to the next stage in the development of these materials - namely the production of large scale parts suitable for testing and evaluation in a range of relevant test environments. This report provides a broad overview of the ongoing efforts in the processing, characterization, and consolidation of these materials at ARL. In particular, focus is placed on the methodology used for producing the nanocrystalline metal powders, in both small and large-scale amounts, that are at the center of ongoing research efforts.

This paper provides a brief overview of the ongoing efforts at the Army Research Laboratory on the processing of bulk nanocrystalline metals with an emphasis on the methodologies used for the production of the novel metal powders.

Traitement des métaux nanocristallins en vrac à l’US Army Research Laboratory

Given their potential for significant property improvements relative to their large grained counterparts, much work has been devoted to the continued ...

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57Fe isotope, namely M&#246;ssbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. M&#246;ssbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Here, we present a protocol to describe ex situ and in situ investigations of structural transformations in metallic glasses. We employed nuclear-based analytical methods which inspect hyperfine interactions. We demonstrate the applicability of M&#246;ssbauer spectrometry and nuclear forward scattering of synchrotron radiation during temperature-driven experiments.

Méthodes Ex Situ et In Situ des enquêtes des Transformations structurelles : le cas de la cristallisation des verres métalliques

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic ...