Ce travail a été soutenu par l’Office of Naval Research (ONR N00014-15-1-0020) [Tkacik et Keanini] et jouée à l’University of North Carolina at Motorsports Research Lab. polissage Charlotte médias a été donné par Rosler.

<ol>
	<li>Berne, B. J., Pecora, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Dynamic Light Scattering. , (1976).</li><li>Boon, J. P., Yip, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular Hydrodynamics. , (1980).</li><li>Brown, J. C., Pusey, P. N., Goodwin, J. W., Ottewill, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+scattering+study+of+dynamic+and+time-averaged+correlations+in+dispersions+of+charged+particles.">Light scattering study of dynamic and time-averaged correlations in dispersions of charged particles.</a> J. Phys. A: Math Gen. 5 (8), 664-682 (1975).</li><li>Wainwright, T. E., Alder, B. J., Gass, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Decay+of+time+correlations+in+two+dimensions.">Decay of time correlations in two dimensions.</a> Phys. Rev. A. 4, 233-236 (1971).</li><li>Evans, D. J., Morriss, G. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical Mechanics of Nonequilibrium Liquids. , (2007).</li><li>Levesque, D., Verlet, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computer+"experiments"+on+classical+fluids,+III.+time-dependent+self+correlation+functions.">Computer "experiments" on classical fluids, III. time-dependent self correlation functions.</a> Phys. Rev. A. 2, 2514-2528 (1970).</li><li>Levesque, D., Ashurst, W. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-time+behavior+of+the+velocity+autocorrelation+function+for+a+fluid+of+soft+repulsive+particles.">Long-time behavior of the velocity autocorrelation function for a fluid of soft repulsive particles.</a> Phys. Rev. Lett. 33, 277-280 (1970).</li><li>Lovesey, S. W., Lovesey, S. W., Springer, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Dynamics of solids and liquids by neutron scattering. , (1977).</li><li>Forster, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Hydrodynamic fluctuations, broken symmetry, and correlation functions. , (1990).</li><li>Mountain, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generalized+hydrodynamics.">Generalized hydrodynamics.</a> Adv. Mol. Relax. Processes. 9, 225-291 (1977).</li><li>Zwanzig, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time-correlation+functions+and+transport+coefficients+in+statistical+mechanics.">Time-correlation functions and transport coefficients in statistical mechanics.</a> Ann. Rev. Phys. Chem. 16, 67-102 (1965).</li><li>Keanini, R. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macroscopic+liquid-state+molecular+hydrodynamics.">Macroscopic liquid-state molecular hydrodynamics.</a> Sci. Rep. 7, 41658 (2017).</li><li>Kushick, J., Berne, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+attractive+forces+in+self-diffusion+in+dense+Lennard-Jones+fluids.">Role of attractive forces in self-diffusion in dense Lennard-Jones fluids.</a> J. Chem. Phys. 59 (7), 3732-3736 (1973).</li><li>Mullany, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+application+of+computational+fluid+dynamics+to+vibratory+finishing+processes.">The application of computational fluid dynamics to vibratory finishing processes.</a> CIRP Annals. , (2017).</li><li>Fleischhauer, E., Azimi, F., Tkacik, P. T., Keanini, R. G., Mullany, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+particle+imaging+velocimetry+(PIV)+to+vibrational+finishing.">Application of particle imaging velocimetry (PIV) to vibrational finishing.</a> J. Mater. Process. Technol. 229, 322-328 (2016).</li><li>Navare, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Experimental and computational evaluation of a vibratory finishing process. , (2017).</li><li>Bolmatov, V., Brazhkin, V., Trachenko, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+phonon+theory+of+liquid+thermodynamics.">The phonon theory of liquid thermodynamics.</a> Sci. Rep. 2, 421 (2012).</li><li>Elton, D. C., Fernandez-Serra, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+hydrogen-bond+network+of+water+supports+propagating+optical+phonon-like+modes.">The hydrogen-bond network of water supports propagating optical phonon-like modes.</a> Nat. Commun. 7, 10193 (2016).</li><li>Pathria, R. K., Beale, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical mechanics. , (2011).</li><li>Gibbs, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Elementary principles in statistical mechanics. , (1902).</li><li>Toda, M., Kubo, R., Saito, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical physics I. , (1992).</li><li>Kubo, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Statistical+mechanical+theory+of+irreversible+processes.">Statistical mechanical theory of irreversible processes.</a> I. J. Phys. Soc. Japan. 12, 570-586 (1957).</li><li>Kubo, R., Toda, M., Hashitsume, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical physics II: nonequilibrium statistical mechanics. , (1991).</li></ol>

Les auteurs n’ont rien à divulguer.

Afin d’utiliser le grain vibré pieux comme analogues macroscopiques pour enquêter sur les processus hydrodynamiques moléculaires, un expérimentateur doit, d’une part, apprendre et utiliser quatre mesures de base et d’autre part, maîtriser quelques éléments de base d’équilibre et hors de l’équilibre mécanique statistique. Se concentrant d’abord sur des mesures expérimentales, il s’agit : i) la mesure de la dynamique des grains individuels par le biais de mesure de la fonction d’autocorrélation...

Hydrodynamique moléculaire étudie la dynamique et les collections de molécules dans les fluides et mécanique statistique des molécules individuelles. Parmi les nombreuses techniques expérimentales développées pour l’étude des systèmes hydrodynamiques moléculaire1,2, diffusion de la lumière1,2,3, des simulations de dynamique moléculaire4, 5,6,7 et, dans une moindre mesure, de la diffusion inélastique des neutrons8 ont été plus couramment utilisé. Malheureusement, des limitations importantes fixer sur les deux techniques de ce dernier. Des simulations de dynamique moléculaire (DM), par exemple : i) sont limitée aux petites spatiale et temporelle <img alt="Equation 1" src="/files/ftp_upload/56632/56632eq1.jpg"> domaines contenant des molécules relativement peu <img alt="Equation 2" src="/files/ftp_upload/56632/56632eq2.jpg"> </img>, ii) nécessitent l’utilisation approximative entre particules potentiels, iii) généralement présenter périodique conditions aux limites, non valides en vertu des conditions d’écoulement de non-équilibre en vrac et iv) ne peut pas, à l’heure actuelle, répondre à la question fondamentale de la dynamique de l’échelle moléculaire comment, impliquant des molécules simples ou collections de molécules, sont affectées par et couple Retour à, en vrac, écoulements de fluides non équilibré. La principale limitation liée à la diffusion des neutrons est liée à la difficulté d’accéder à du nombre limité de sources de faisceau de neutrons disponibles.
Afin de fournir le contexte pour la technique expérimentale analogue présentée dans cet article, nous mettons en évidence les techniques de diffusion de la lumière appliqués aux fluides simples de gaz dense et état liquide. Dans une expérience de diffraction de la lumière typique, un faisceau de lumière polarisée laser est dirigé vers un volume petit interrogatoire contenant un échantillon de fluide stationnaire. Lumière diffusée de molécules au sein de l’échantillon est alors détectée à un certain angle fixe par rapport au faisceau incident. Suivant le régime dynamique moléculaire d’intérêt, détection et analyse du signal lumineux épars intègre soit léger filtrage ou light mélange des méthodes de détection. Comme souligné par Berne et Pecora1, filtrage techniques, qui sonde la dynamique moléculaire état fluide ponctuellement échelles plus courte que <img alt="Equation 3" src="/files/ftp_upload/56632/56632eq3.jpg"> s, introduire un interféromètre après diffusion ou un réseau de diffraction et permettent l’analyse de la densité spectrale de la lumière diffusée. Optique, mélangeant les techniques, utilisées pour la dynamique lente-chronologique, <img alt="Equation 4" src="/files/ftp_upload/56632/56632eq4.jpg"> s, en revanche, intégrer un analyseur autocorrelator ou spectre après diffusion, dans lequel le contenu spectral du signal diffusé est extraite de la lumière mesurée intensité.
En règle générale, laser sondes, au moins ceux fonctionnant dans la gamme visible du spectre, ont des longueurs d’onde beaucoup plus longues que l’espacement typique entre les molécules de l’état liquide. Dans ces circonstances, le faisceau sonde excite cinq collective, ralentir-chronologique, modes hydrodynamiques de long-longueur d’onde2,9,10 (lent par rapport à la fréquence de collision caractéristique) : deux visqueux amortie, Counter-propagation des ondes sonores, deux modes de vorticité découplé, purement diffusif et un mode unique par diffusion thermique (entropie). Les modes sonores sont excités dans le sens (longitudinal) du faisceau incident, tandis que les modes tourbillonnaires sont excités dans le sens transversal.
Systèmes de l’état liquide, considérant purement expérimental, deux questions fondamentales, située au coeur de l’équilibre et hors équilibre mécanique statistique de moléculaire, des techniques de diffusion restent au-delà de la lumière et mesures de diffusion des neutrons : 1) spectacle de11 9,arguments rigoureux que la dynamique de collision et sous-sous-collision-temps-échelle aléatoire, de l’état liquide des molécules individuelles, sous réserve de la dynamique newtonienne classique ou dynamique quantique, peut procéder à une refonte de la forme d’équations généralisées de Langevin (GLE). GLE, à leur tour, constituent un outil théorique central dans l’étude de la mécanique statistique de non-équilibre des molécules de gaz denses et liquides. Malheureusement, étant donné que la dynamique des molécules (non macromoléculaire) individuelles ne peut être résolue par une technique de diffusion, il n’existe actuellement aucun moyen direct, au-delà des simulations de MD, pour tester la validité du GLE. 2) une hypothèse fondamentale se trouvant au cœur de la dynamique des fluides macroscopiques continuum, ainsi microscopique moléculaire hydrodynamique, pose en principe que sur longueur - et échelles de temps importants par rapport à des diamètres moléculaires et de la collision, mais petites par rapport au continuum longueur - et échelles de temps, l’équilibre thermodynamique local (LTE) prévaut. Dans le continuum flux et chaleur transfert modèles, comme les équations de Navier-Stokes (NS), l’hypothèse de LTE est obligatoire,9 pour couple intrinsèquement non équilibré, les flux de continuum-échelle et les fonctionnalités de transport d’énergie — comme les contraintes de cisaillement visqueux et conduction thermique — strictement équilibre thermodynamique des propriétés, comme la température et l’énergie interne. De même, tandis que microscale transport de quantité de mouvement et d’énergie sont intrinsèquement non équilibré processus, ce qui reflète l’apparence du couplé, masse de micro-échelle, modèles de dynamique et les courants d’énergie, de ces processus micro-échelle supposent que les courants représenter les petites perturbations du LTE9. Encore une fois, au meilleur de nos connaissances, on n’a aucun test expérimentale directe de l’Assomption de LTE. En particulier, il semble qu’aucune expériences moléculaires diffusion hydrodynamiques n’ont été tentées dans les écoulements fluides denses, mobiles, non équilibré.
Dans cet article, nous décrivons une technique expérimentale analogique dans lequel la particule macroscopique, unique et la dynamique de la particule collective des pieux de grain vibré, mesurée à l’aide de standard Particle Imaging Velocimetry (PIV), peut être utilisée pour prédire indirectement, interpréter et exposer seul - et multi - molecule hydrodynamique dans les liquides et les gaz denses. Les éléments physiques et théoriques qui permettent la technique proposée sont précisées dans un récent article publié par notre groupe de12. Expérimentalement, le système macroscopique doit faire preuve : (i) une tendance soutenue à la locale, équilibre mécanique statistique échelle macroscopique et (ii) small, départs linéaires d’équilibre qui imitent les fluctuations de non-équilibre (faibles) observée chez systèmes hydrodynamiques moléculaires. Théoriquement : modèles microscale i classique décrivant l’équilibre et la mécanique statistique faiblement-hors de l’équilibre de dense, interaction des systèmes de particules N doivent procéder à sa refonte sous forme d’échelle macroscopique, et (ii) les modèles résultants de la macro-échelle doivent sûrement prédire la dynamique de l’unique et plusieurs particules, du courts, particule-collision-échelles de temps à, continuum-flux-échelles de temps longues.
Ici, nous présentons un plan expérimental détaillé ainsi que représentant résultats obtenus par cette nouvelle technique. Contrairement à des simulations de MD et de lumière et de méthodes de diffusion de neutrons, la nouvelle technique permet, pour la première fois, l’étude détaillée des processus hydrodynamiques moléculaires au sein qui coule, fortement non équilibré, denses de gaz et liquides.

<table>
	<tbody>
		<tr>
			<td>Vibratory Polishing Bowl</td>
			<td>Raytech</td>
			<td>AV-75</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Meter</td>
			<td>Peristaltic Pumps</td>
			<td>913 Mity Flex</td>
			<td></td>
		</tr>
		<tr>
			<td>Scale</td>
			<td>Pelouze</td>
			<td>4040</td>
			<td></td>
		</tr>
		<tr>
			<td>Triaxial Accelerometer</td>
			<td>PCB Piezotronics</td>
			<td>PCB 356B11</td>
			<td>Accelerometer with Sensor Signal Conditioner</td>
		</tr>
		<tr>
			<td>Data Acquisition Computer</td>
			<td>IBM</td>
			<td>Thinkpad</td>
			<td>Used with high speed camera</td>
		</tr>
		<tr>
			<td>High Speed Camera</td>
			<td>Redlake</td>
			<td>Motionxtra HG-XR</td>
			<td></td>
		</tr>
		<tr>
			<td>Zoom Lens</td>
			<td>Tamron</td>
			<td>Model A18</td>
			<td>18-250mm F/3.5-6.3&#160;</td>
		</tr>
		<tr>
			<td>High intensity Light</td>
			<td>ARRI</td>
			<td>EB 400/575 D</td>
			<td></td>
		</tr>
		<tr>
			<td>Data Processing Computer</td>
			<td>Dell</td>
			<td>Dell Precision Tower 7910</td>
			<td></td>
		</tr>
		<tr>
			<td>PIV Software&#160;</td>
			<td>Dantec Dynamics</td>
			<td>Dynamic Studio 2013</td>
			<td>version 3.41.38</td>
		</tr>
		<tr>
			<td>Data Acquisition Hardware</td>
			<td>National Instruments</td>
			<td>SCXI</td>
			<td>SCXI-1000 Chasis with SCXI 1100 Card and SCXI 1303 Adapter</td>
		</tr>
		<tr>
			<td>Data Acquisition Software</td>
			<td>National Instruments</td>
			<td>LabVIEW 2012</td>
			<td></td>
		</tr>
		<tr>
			<td>Data Processing Software</td>
			<td>MATHWORKS</td>
			<td>MATLAB</td>
			<td></td>
		</tr>
		<tr>
			<td>Polishing Media</td>
			<td>Rosler</td>
			<td>RSG 10/10S</td>
			<td>Multiple media types used (mixed, spherical, triangular)</td>
		</tr>
		<tr>
			<td>Polishing Solution</td>
			<td>Rosler</td>
			<td>FC KFL (3%)</td>
			<td>3% soap solution with water</td>
		</tr>
		<tr>
			<td>Ruled Scale</td>
			<td>Swiss Precision Instruments</td>
			<td>13-911-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Graduated Cylinder</td>
			<td>Global Scientific</td>
			<td>601082</td>
			<td></td>
		</tr>
	</tbody>
</table>

an analog macroscopic technique for studying molecular hydrodynamic processes in dense gases and liquids

Une méthode analogue, macroscopique pour étudier les processus hydrodynamiques échelle moléculaire dans les liquides et les gaz denses est décrite. La technique s’applique une norme fluide dynamique diagnostique, particule vélocimétrie par image (PIV), pour mesurer : i) des vitesses des particules (grains), existants sur collision grain courte, échelles de temps, vitesses ii) des systèmes de particules, sur les deux courts collision-temps - et long, continuum-flux-échelles de temps, iii) collectives modes hydrodynamiques qui existent encore dans les liquides moléculaires denses et iv) fonctions d’autocorrélation vitesse de court et long-temps-échelle, centrales pour comprendre la dynamique des particules à l’échelle dans systèmes de fluides fortement interdépendants, denses. Le système de base se compose d’un système d’imagerie, source lumineuse, capteurs de vibrations, vibration système avec un logiciel connu des médias et analyse et PIV. Mesures expérimentales nécessaires et un aperçu des outils théoriques nécessaires lorsque vous utilisez la technique analogique pour étudier les processus hydrodynamiques échelle moléculaire sont mises en évidence. La technique proposée offre une alternative relativement simple à photoniques et méthodes de diffusion utilisés traditionnellement dans les études hydrodynamiques moléculaires de faisceau de neutrons.

En présentant les résultats représentatifs, nous nous référons aux processus de continuum-chronologique que ceux observés et prévus sur des échelles de temps, <img alt="Equation 25" src="/files/ftp_upload/56632/56632eq25.jpg"> qui sont long par rapport à l’échelle de temps de collision de grain caractéristique, <img alt="Equation 26" src="/files/ftp_upload/56632/56632eq26.jpg"> <img alt="Equation 27" src="/files/ftp_upload/56632/56632eq27.jpg"> et particule-chro...

Watch this Scientific Journal Video about An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids at JoVE.com

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

On présente une méthode analogue expérimentalement accessible pour l’étude des processus hydrodynamiques moléculaires dans les fluides denses. La technique utilise la vélocimétrie par image de particules de pieux de grain vibré, haute-restitution et permet l’observation directe, macroscopique des processus dynamiques connu et prédit d’exister en interagissant fortement, haute densité gaz et liquides.

Une Technique analogue macroscopique pour l’étude des processus hydrodynamiques moléculaires dans les liquides et les gaz denses

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a ...

an-analog-macroscopic-technique-for-studying-molecular-hydrodynamic

Education

Research

JoVE Core

JoVE Journal

Physics

Engineering

Chemistry

Civil Engineering

Unit 1

Vectors and Scalars

Fluid Dynamics

Gases

SCIENTISTS IN ACTION

8.4K vues.  University of North Carolina at Charlotte. On présente une méthode analogue expérimentalement accessible pour l’étude des processus hydrodynamiques moléculaires dans les fluides denses. La technique utilise la vélocimétrie par image de particules de pieux de grain vibré, haute-restitution et permet l’observation directe, macroscopique des processus dynamiques connu et prédit d’exister en interagissant fortement, haute densité gaz et liquides.

Vidéo: An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

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 ...

Recherche

Ingénierie

Simulation of the Planetary Interior Differentiation Processes in the Laboratory

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 that layered structure, (1) percolation of liquid metal in a solid silicate matrix by planet differentiation, and (2) inner core crystallization by subsequent planet cooling. We conduct high-pressure and high-temperature experiments to simulate both processes in the laboratory. Formation of percolative planetary core depends on the efficiency of melt percolation, which is controlled by the dihedral (wetting) angle. The percolation simulation includes heating the sample at high pressure to a target temperature at which iron-sulfur alloy is molten while the silicate remains solid, and then determining the true dihedral angle to evaluate the style of liquid migration in a crystalline matrix by 3D visualization. The 3D volume rendering is achieved by slicing the recovered sample with a focused ion beam (FIB) and taking SEM image of each slice with a FIB/SEM crossbeam instrument. The second set of experiments is designed to understand the inner core crystallization and element distribution between the liquid outer core and solid inner core by determining the melting temperature and element partitioning at high pressure. The melting experiments are conducted in the multi-anvil apparatus up to 27 GPa and extended to higher pressure in the diamond-anvil cell with laser-heating. We have developed techniques to recover small heated samples by precision FIB milling and obtain high-resolution images of the laser-heated spot that show melting texture at high pressure. By analyzing the chemical compositions of the coexisting liquid and solid phases, we precisely determine the liquidus curve, providing necessary data to understand the inner core crystallization process.

The high-pressure and high-temperature experiments described here mimic planet interior differentiation processes. The processes are visualized and better understood by high-resolution 3D imaging and quantitative chemical analysis.

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 ...

Spatial Separation of Molecular Conformers and Clusters

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold molecular beams. However, these beams often contain multiple conformers and clusters, even at low rotational temperatures. We present an experimental methodology that allows the spatial separation of these constituent parts of a molecular beam expansion. Using an electric deflector the beam is separated by its mass-to-dipole moment ratio, analogous to a bender or an electric sector mass spectrometer spatially dispersing charged molecules on the basis of their mass-to-charge ratio. This deflector exploits the Stark effect in an inhomogeneous electric field and allows the separation of individual species of polar neutral molecules and clusters. It furthermore allows the selection of the coldest part of a molecular beam, as low-energy rotational quantum states generally experience the largest deflection. Different structural isomers (conformers) of a species can be separated due to the different arrangement of functional groups, which leads to distinct dipole moments. These are exploited by the electrostatic deflector for the production of a conformationally pure sample from a molecular beam. Similarly, specific cluster stoichiometries can be selected, as the mass and dipole moment of a given cluster depends on the degree of solvation around the parent molecule. This allows experiments on specific cluster sizes and structures, enabling the systematic study of solvation of neutral molecules.

We present a technique that allows the spatial separation of different conformers or clusters present in a molecular beam. An electrostatic deflector is used to separate species by their mass-to-dipole moment ratio, leading to the production of gas-phase ensembles of a single conformer or cluster stoichiometry.

Séparation spatiale des conformateurs moléculaires et des amas

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold ...

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical electrohydrodynamic liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields and polar dielectric liquids. The construction of basic apparatus and operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

La préparation de ElectroHydroDynamique Ponts de polaires liquides diélectriques

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and ...

Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% of the bulk. The primary advantage of AD is that the deposition takes place entirely at ambient temperature; thereby enabling film growth in material systems with disparate melting temperatures. This report describes in detail the processing steps for preparing the powder and for performing AD using the custom-built system. Representative characterization results are presented from scanning electron microscopy, profilometry, and ferromagnetic resonance for films grown in this system. As a representative overview of the capabilities of the system, focus is given to a sample produced following the described protocol and system setup. Results indicate that this system can successfully deposit 11 &#181;m thick yttrium iron garnet films that are &#160;&#62; 90% of the bulk density during a single 5 min deposition run. A discussion of methods to afford better control of the aerosol and particle selection for improved thickness and roughness variations in the film is provided.

This report describes the use of a custom-built system to perform aerosol deposition of thick films of yttrium iron garnet onto sapphire substrates at RT. The deposited films are characterized using scanning electron microscopy, profilometry, and ferromagnetic resonance to give a representative overview of the capabilities of the technique.

Formation de plus épaisses yttrium fer grenat Films Utilisation Aérosol dépôt

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

Méthodes expérimentales pour les enquêtes de la mémoire de forme à base Elastocaloric processus de refroidissement et de validation du modèle

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

This protocol describes the operation of a liquid flow specimen holder for scanning transmission electron microscopy of AuNPs in water, as used for the observation of nanoscale dynamic processes.

L&#39;étude des processus dynamiques de Nano-objets de taille dans le liquide en utilisant la transmission de microscopie électronique à balayage

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a ...

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 ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

Préparation des réseaux de cristaux liquides pour macroscopique mouvement oscillatoire induite par la lumière

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

An Available Technique for Preparation of New Cast MnCuNiFeZnAl Alloy with Superior Damping Capacity and High Service Temperature

Manganese (Mn)-copper (Cu)-based alloys have been found to have&#160;damping capacity and can be used to reduce harmful vibrations and noise effectively. M2052 (Mn-20Cu-5Ni-2Fe, at%) is an important branch of Mn-Cu-based alloys, which possesses both excellent damping capacity and processability. In recent decades, lots of studies have been carried out on the performance optimization of M2052, improving the damping capacity, mechanical properties, corrosion resistance, and service temperature, etc. The major methods of performance optimization are alloying, heat treatment, pretreatment, and different ways of molding etc., among which alloying, as well as adopting a reasonable heat treatment, is the simplest and most effective method to obtain perfect and comprehensive performance. To obtain the M2052 alloy with excellent performance for casting molding, we propose to add Zn and Al to the MnCuNiFe alloy matrix and use a variety of heat treatment methods for a comparison in the microstructure, damping capacity, and service temperature. Thus, a new type of cast-aged Mn-22.68Cu-1.89Ni-1.99Fe-1.70Zn-6.16Al (at.%) alloy with&#160;superior damping capacity and high service temperature is obtained by an optimized heat treatment method. Compared with the forging technique, cast molding is simpler and more efficient, and the damping capacity of this as-cast alloy is excellent. Therefore, there is a suitable reason to think that it is a good choice for engineering applications.

Here we present a protocol to obtain a novel Mn-Cu-based alloy with excellent comprehensive performances by a high-quality smelting technology and reasonable heat treatment methods.

Une Technique disponible pour la préparation de nouveaux MnCuNiFeZnAl coulé avec Superior Service capacité et à haute température d’amortissement

Manganese (Mn)-copper (Cu)-based alloys have been found to have&#160;damping capacity and can be used to reduce harmful vibrations and noise effectively. ...