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Статті в журналах з теми "Elasticity- Nanostructure"
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M. Roy, Arunabha. "Evolution of Martensitic Nanostructure in NiAl Alloys: Tip Splitting and Bending." Material Science Research India 17, SpecialIssue1 (August 1, 2020): 03–06. http://dx.doi.org/10.13005/msri.17.special-issue1.02.
Повний текст джерелаАнотація:
A phase-field (PF) model for the phase transformation (PT) between austenite and martensite and twinning between two martensite is presented where PT is described by a single order parameter. Such a description helps us to obtain the analytical solution of interface energetics and kinetics. PF-elasticity problems are solved for cubic-to-tetragonal PT in NiAl. The stress and temperature-induced PT and corresponding twinning and growth of the martensitic phase inside a nanocrystal are simulated. It reproduces nontrivial experimentally observed nanostructure such as splitting and bending of martensitic nanostructure as well as twins crossing. The evolution and morphology of such interesting nanostructures are discussed.
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Chowdhury, R., S. Adhikari, and F. Scarpa. "Elasticity and piezoelectricity of zinc oxide nanostructure." Physica E: Low-dimensional Systems and Nanostructures 42, no. 8 (June 2010): 2036–40. http://dx.doi.org/10.1016/j.physe.2010.03.018.
Повний текст джерела
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ISLAM, Z. M., P. JIA, and C. W. LIM. "TORSIONAL WAVE PROPAGATION AND VIBRATION OF CIRCULAR NANOSTRUCTURES BASED ON NONLOCAL ELASTICITY THEORY." International Journal of Applied Mechanics 06, no. 02 (March 17, 2014): 1450011. http://dx.doi.org/10.1142/s1758825114500112.
Повний текст джерелаАнотація:
The presence of size effects represented by a small nanoscale on torsional wave propagation properties of circular nanostructure, such as nanoshafts, nanorods and nanotubes, is investigated. Based on the nonlocal elasticity theory, the dynamic equation of motion for the structure is formulated. By using the derived equation, simple analytical solutions for the relation between wavenumber and frequency via the differential nonlocal constitutive relation and the numerical solutions for a discrete nonlocal model via the integral nonlocal constitutive relation have been obtained. This results not only show that the dispersion characteristics of circular nanostructures are greatly affected by the small nanoscale and the classical theory overestimates the stiffness of nanostructures, but also highlights the significance of the integral nonlocal model which is able to capture some boundary characteristics that do not appear in the differential nonlocal model.
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Dindarloo, Mohammad Hassan, Li Li, Rossana Dimitri, and Francesco Tornabene. "Nonlocal Elasticity Response of Doubly-Curved Nanoshells." Symmetry 12, no. 3 (March 16, 2020): 466. http://dx.doi.org/10.3390/sym12030466.
Повний текст джерелаАнотація:
In this paper, we focus on the bending behavior of isotropic doubly-curved nanoshells based on a high-order shear deformation theory, whose shape functions are selected as an accurate combination of exponential and trigonometric functions instead of the classical polynomial functions. The small-scale effect of the nanostructure is modeled according to the differential law consequent, but is not equivalent to the strain-driven nonlocal integral theory of elasticity equipped with Helmholtz’s averaging kernel. The governing equations of the problem are obtained from the Hamilton’s principle, whereas the Navier’s series are proposed for a closed form solution of the structural problem involving simply-supported nanostructures. The work provides a unified framework for the bending study of both thin and thick symmetric doubly-curved shallow and deep nanoshells, while investigating spherical and cylindrical panels subjected to a point or a sinusoidal loading condition. The effect of several parameters, such as the nonlocal parameter, as well as the mechanical and geometrical properties, is investigated on the bending deflection of isotropic doubly-curved shallow and deep nanoshells. The numerical results from our investigation could be considered as valid benchmarks in the literature for possible further analyses of doubly-curved applications in nanotechnology.
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Zhang, Y., L. J. Zhuo, and H. S. Zhao. "Determining the effects of surface elasticity and surface stress by measuring the shifts of resonant frequencies." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 469, no. 2159 (November 8, 2013): 20130449. http://dx.doi.org/10.1098/rspa.2013.0449.
Повний текст джерелаАнотація:
Both surface elasticity and surface stress can result in changes of resonant frequencies of a micro/nanostructure. There are infinite combinations of surface elasticity and surface stress that can cause the same variation for one resonant frequency. However, as shown in this study, there is only one combination resulting in the same variations for two resonant frequencies, which thus provides an efficient and practical method of determining the effects of both surface elasticity and surface stress other than an atomistic simulation. The errors caused by the different models of surface stress and mode shape change due to axial loading are also discussed.
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Elbourne, Aaron, James Chapman, Amy Gelmi, Daniel Cozzolino, Russell J. Crawford, and Vi Khanh Truong. "Bacterial-nanostructure interactions: The role of cell elasticity and adhesion forces." Journal of Colloid and Interface Science 546 (June 2019): 192–210. http://dx.doi.org/10.1016/j.jcis.2019.03.050.
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Tamm, Aile, Tauno Kahro, Helle-Mai Piirsoo, and Taivo Jõgiaas. "Atomic-Layer-Deposition-Made Very Thin Layer of Al2O3, Improves the Young’s Modulus of Graphene." Applied Sciences 12, no. 5 (February 27, 2022): 2491. http://dx.doi.org/10.3390/app12052491.
Повний текст джерелаАнотація:
Nanostructures with graphene make them highly promising for nanoelectronics, memristor devices, nanosensors and electrodes for energy storage. In some devices the mechanical properties of graphene are important. Therefore, nanoindentation has been used to measure the mechanical properties of polycrystalline graphene in a nanostructure containing metal oxide and graphene. In this study the graphene was transferred, prior to the deposition of the metal oxide overlayers, to the Si/SiO2 substrate were SiO2 thickness was 300 nm. The atomic layer deposition (ALD) process for making a very thin film of Al2O3 (thickness comparable with graphene) was applied to improve the elasticity of graphene. For the alumina film the Al(CH3)3 and H2O were used as the precursors. According to the micro-Raman analysis, after the Al2O3 deposition process, the G-and 2D-bands of graphene slightly broadened but the overall quality did not change (D-band was mostly absent). The chosen process did not decrease the graphene quality and the improvement in elastic modulus is significant. In case the load was 10 mN, the Young’s modulus of Si/SiO2/Graphene nanostructure was 96 GPa and after 5 ALD cycles of Al2O3 on graphene (Si/SiO2/Graphene/Al2O3) it increased up to 125 GPa. Our work highlights the correlation between nanoindentation and defects appearance in graphene.
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Ivanova, Elena P., Denver P. Linklater, Marco Werner, Vladimir A. Baulin, XiuMei Xu, Nandi Vrancken, Sergey Rubanov, et al. "The multi-faceted mechano-bactericidal mechanism of nanostructured surfaces." Proceedings of the National Academy of Sciences 117, no. 23 (May 26, 2020): 12598–605. http://dx.doi.org/10.1073/pnas.1916680117.
Повний текст джерелаАнотація:
The mechano-bactericidal activity of nanostructured surfaces has become the focus of intensive research toward the development of a new generation of antibacterial surfaces, particularly in the current era of emerging antibiotic resistance. This work demonstrates the effects of an incremental increase of nanopillar height on nanostructure-induced bacterial cell death. We propose that the mechanical lysis of bacterial cells can be influenced by the degree of elasticity and clustering of highly ordered silicon nanopillar arrays. Herein, silicon nanopillar arrays with diameter 35 nm, periodicity 90 nm and increasing heights of 220, 360, and 420 nm were fabricated using deep UV immersion lithography. Nanoarrays of 360-nm-height pillars exhibited the highest degree of bactericidal activity toward both Gram stain-negativePseudomonas aeruginosaand Gram stain-positiveStaphylococcus aureusbacteria, inducing 95 ± 5% and 83 ± 12% cell death, respectively. At heights of 360 nm, increased nanopillar elasticity contributes to the onset of pillar deformation in response to bacterial adhesion to the surface. Theoretical analyses of pillar elasticity confirm that deflection, deformation force, and mechanical energies are more significant for the substrata possessing more flexible pillars. Increased storage and release of mechanical energy may explain the enhanced bactericidal action of these nanopillar arrays toward bacterial cells contacting the surface; however, with further increase of nanopillar height (420 nm), the forces (and tensions) can be partially compensated by irreversible interpillar adhesion that reduces their bactericidal effect. These findings can be used to inform the design of next-generation mechano-responsive surfaces with tuneable bactericidal characteristics for antimicrobial surface technologies.
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Taghvaei, Mohammad Mahdi, Hossein Mostaan, Mahdi Rafiei, Hamid Reza Bakhsheshi-Rad, and Filippo Berto. "Nanoscale Tribological Properties of Nanostructure Fe3Al and (Fe,Ti)3Al Compounds Fabricated by Spark Plasma Sintering Method." Metals 12, no. 7 (June 23, 2022): 1077. http://dx.doi.org/10.3390/met12071077.
Повний текст джерелаАнотація:
Nanostructured powder particles of Fe3Al and (Fe,Ti)3Al phases were produced using mechanical alloying. These intermetallic phases with a nearly complete density were consolidated by spark plasma sintering. The mechanical properties of the bulk samples, i.e., elasticity modulus, hardness, and plasticity index, and also their tribological behavior were investigated using nanoindentation and nano-scratch tests. It was found that both Fe3Al and (Fe,Ti)3Al phases can be synthesized after 30 h of high-energy ball milling. In addition, no phase evolution was observed after spark plasma sintering. An analysis of the atomic force microscope images obtained from the nanoindentation tests showed a higher elasticity modulus, higher hardness, and lower plasticity index due to the addition of Ti to the Fe3Al system. (Fe,Ti)3Al displayed better tribological properties as compared with Fe3Al. A smaller volume of the scratched line was clearly seen in the atomic force microscope images of the nanostructured (Fe,Ti)3Al compound.
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Hashemzadeh, Allahverdi, Ghorbani, Soleymani, Kocsis, Fischer, Ertl, and Naderi-Manesh. "Gold Nanowires/Fibrin Nanostructure as Microfluidics Platforms for Enhancing Stem Cell Differentiation: Bio-AFM Study." Micromachines 11, no. 1 (December 30, 2019): 50. http://dx.doi.org/10.3390/mi11010050.
Повний текст джерелаАнотація:
Organ-on-a-chip technology has gained great interest in recent years given its ability to control the spatio-temporal microenvironments of cells and tissues precisely. While physical parameters of the respective niche such as microchannel network sizes, geometric features, flow rates, and shear forces, as well as oxygen tension and concentration gradients, have been optimized for stem cell cultures, little has been done to improve cell-matrix interactions in microphysiological systems. Specifically, detailed research on the effect of matrix elasticity and extracellular matrix (ECM) nanotopography on stem cell differentiation are still in its infancy, an aspect that is known to alter a stem cell’s fate. Although a wide range of hydrogels such as gelatin, collagen, fibrin, and others are available for stem cell chip cultivations, only a limited number of elasticities are generally employed. Matrix elasticity and the corresponding nanotopography are key factors that guide stem cell differentiation. Given this, we investigated the addition of gold nanowires into hydrogels to create a tunable biointerface that could be readily integrated into any organ-on-a-chip and cell chip system. In the presented work, we investigated the matrix elasticity (Young’s modulus, stiffness, adhesive force, and roughness) and nanotopography of gold nanowire loaded onto fibrin hydrogels using the bio-AFM (atomic force microscopy) method. Additionally, we investigated the capacity of human amniotic mesenchymal stem cells (hAMSCs) to differentiate into osteo- and chondrogenic lineages. Our results demonstrated that nanogold structured-hydrogels promoted differentiation of hAMSCs as shown by a significant increase in Collagen I and II production. Additionally, there was enhanced calcium mineralization activity and proteoglycans formation after a cultivation period of two weeks within microfluidic devices.
Дисертації з теми "Elasticity- Nanostructure"
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Abidi, Sonia. "Matériaux composites à haute tenue thermique : influence de la micro-nanostructure sur les transferts moléculaires, électroniques et thermiques." Thesis, Toulon, 2014. http://www.theses.fr/2014TOUL0019/document.
Повний текст джерелаАнотація:
Les matériaux de protection incendie sont largement utilisés pour assurer la sécurité des usagers des infrastructures. Les normes de protection incendie évoluant régulièrement, les matériaux doivent être de plus en plus performants. Ceux-ci sont généralement des mortiers constitués d’oxydes réfractaires et isolants. L’objectif de ce travail est de mettre au point un composite coupe-feu 4 h applicable par projection mais également de déterminer ses propriétés thermiques et mécaniques.Dans une première partie, cette étude reprend les différentes étapes de l’élaboration d’un matériau de protection incendie, après la présentation de la démarche qui a guidé l’élaboration de nos matériaux, nous nous sommes intéressés plus particulièrement à la composition chimique de la matrice ainsi que celle du ciment. Leurs propriétés thermiques et mécaniques ont été passées en revue.Les matières premières nécessaires à l’élaboration d’un mortier ont ensuite été sélectionnées. L’évolution, respectivement de la conductivité thermique, de la diffusivité, de la porosité, de la chaleur spécifique et des propriétés mécaniques des mortiers choisis en fonction de la nature et de la quantité de charges incorporées à la matrice a été étudiée. Une description des divers modèles analytiques et numériques permettant la représentation de la conductivité thermique et du module d’Young des matériaux a permis de développer un modèle capable de prédire le comportement thermique et mécanique des composites en fonction de la nature et de quantité de charges ajoutées.Dans une seconde partie, la cinétique de la réaction d’hydratation du plâtre afin de maîtriser les temps de prise et pour faciliter la production des projetés dans la chaîne industrielle a été étudiée. L’influence sur la cinétique d’hydratation, de la composition chimique du plâtre, de sa granulométrie et de l’ajout d’adjuvants couramment utilisés dans l’industrie plâtrière, a également été traitée.10A l’issue de cette étude, deux formulations de composites projetables ont été mises au pointFire protection materials are widely used to ensure the safety of users of the infrastructure. Standards of fire protection regularly operating, the materials must be more efficient. These are generally composed of refractory mortar and insulating oxides. The objective of this work is to develop a firewall composite 4 h applied by projecting but also to determine the thermal and mechanical properties.In the first part, this study describes the various stages of the development of a fire protection material, after the presentation of the approach that has guided the development of our materials, we are interested especially in the chemical composition of the matrix and that of the cement. Their thermal and mechanical properties have been reviewed.The raw materials for the preparation of mortar were selected. The evolution respectively of thermal conductivity, diffusivity, porosity, specific heat and the mechanical properties of mortars chosen according to the nature and amount of the fillers incorporated in the matrix has been studied. A description of the various analytical and numerical models for the representation of the thermal conductivity and Young's modulus of the materials led to the development of a model able to predict the thermal and mechanical behavior of composites based on the nature and amount of charges added.In a second part, the kinetics of the hydration reaction of gypsum to control setting time and to facilitate the production of the composite in the industrial chain was studied. The influence on the kinetics of hydration, of the chemical composition of the gypsum, particle size distribution and the addition of adjuvant commonly used in the plaster industry, has also been treated.At the end of this study, two formulations of composites applied by projection were developed
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Liu, Kailang. "Fabrication and modeling of SiGe Nanostructures Driven by Hetero-epitaxial Elasticity." Thesis, Ecole centrale de Marseille, 2016. http://www.theses.fr/2016ECDM0014/document.
Повний текст джерелаАнотація:
Nous étudions ici l’heteroepitaxie du silicium-germanium (SiGe), un système qui est couramment considéré comme le stéréotype de l’´épitaxie des semi-conducteurs. Bien que ce système ait déjà attiré une attention considérable en raison de ses applications pour l’ingénierie des bandes dans l’industrie microélectronique, le défi majeur du développement de nouveaux dispositifs à base de SiGe reste la croissance épitaxiale contrôlable des nanostructures auto-assemblées. Il est bien connu que SiGe suit un mode de croissance de Stranski-Krastanov, qui passe par la croissance de couches bidimensionnelles suivie par la croissance d’ılots tridimensionnels. Sous cette dénomination générique ”Stranski-Krastanov”, plusieurs comportements différents peuvent être identifiés. Une compréhension globale de tous ces comportements est encore partiellement manquante en raison de la complexité et de l’interaction de la cinétique et des forces motrices dynamiques, empêchant le d´développement de nouveaux dispositifs. Dans ce travail, nous nous concentrons sur l’auto- assemblage des nanostructures SiGe à la suite de la quête de l’émission de lumière pour les dispositifs photoniques, optoélectroniques et nanoélectroniques à base de Si. Par Même si l’innovation dans les dispositifs à base de Si a été stimulée récemment par le d´développement de silicium complétement épuisé sur les transistors isolants, une véritable percée serait la démonstration de l´émission de lumière et / ou l’absorption par les éléments du groupe IV, car il permet une intégration pratique dans les semi-conducteurs actuels. Dans ce travail, nous montrons d’abord les différents régimes de croissance des films contraints, c’est-à-dire l’instabilité par rapport aux régimes de nucléation. Nous d´développons un modèle qui résout la course de ces deux voies de croissance et d´dévoile les mécanismes des différents modes d’évolution morphologique entrainés par l’élasticité. Dans la seconde partie, nous examinons en détail l’auto-organisation naturelle des îles cohérentes. L’effet élastique direct induit la répulsion entre les îles cohérentes. Cependant, l’énergie de surface dépendant de la déformation qui a été négligée précédemment dans l’analyse de l’interaction île-île est révélée pour provoquer une attraction entre les iles. Il peut compenser la répulsion élastique directe au cours de l´état initial de la nucléation et conduire au regroupement d’îlots cohérents. Dans une troisième partie, nous étudions l’influence des échelons du substrat vicinal sur la formation et l’auto-organisation des îles. Nous démontrons que l’anisotropie de relaxation de la contrainte produite par les bords des gradins est à l’origine de l’allongement de l’instabilité perpendiculaire aux marches. Un accord quantitatif entre l’allongement de l’instabilité et l’anisotropie de relaxation de la souche est trouvé, ce qui approfondit les compréhensions de la croissance hétéroépitaxiale sur le substrat vicinal. Dans la quatrième partie, nous développons un nouveau procédé basé sur la condensation Ge lors de l’oxydation thermique du SiGe dilué. On étudie la cinétique du procédé de condensation SiGe et on fabrique la couche épandeuse de SiGe totalement contrainte par ce procédé de condensation particulierWe investigate here the heteroepitaxy of silicon-germanium (SiGe), a system which is commonly regarded as the stereotype of semiconductor epitaxy. While this system has already attracted a tremendous amount of attention due to its applications for band-gap engineering in microelectronic industry, the major challenge facing the development of new SiGe-based devices remains the con- trollable epitaxial growth of self-assembled nanostructures. It is well-known that SiGe follows a Stranski-Krastanov growth mode, which proceeds via the growth of bi-dimensionnal layers followed by the growth of three-dimensional islands. Under this generic “Stranski-Krastanov” designation, several different behaviors can be identified. An overall understanding of all these behavior is still partially missing due to the complexity and the interplay of kinetics and energetic driving forces, preventing the development of new devices.In this work we focus on the self-assembly of SiGe nanostructures following the quest of light emission for integrated Si-based photonic, optoelectronic and nanoelectronic devices.Even if the innovation in Si-based devices has been boosted recently by the development of ultra-thin body fully depleted silicon on insulator transistors, a real breakthrough would be the demonstration of light emission and/or absorption by group IV elements since it allows the conve- nient integration into the nowadays semiconductors.In this work we first demonstrate the different growth regimes of strained films, i.e. instability versus nucleation regimes. We develop a model which resolves the race of these two growth pathways and unveil the mechanisms of different modes of morphological evolution driven by elasticity.In the second part, we examine in details the natural self-organisation of coherent islands. The direct elastic effect induces repulsion between coherent islands. However, the strain-dependent surface energy which has been overlooked previously in analysis of the island-island interaction is revealed to cause an attraction between islands. It may compensate the direct elastic repulsion during the initial state of nucleation and lead to the clustering of coherent islands.In a third part we study the influence of miscut steps of vicinal substrate on the formation and self-organisation of islands. We demonstrate that the strain relaxation anisotropy produced by the step edges, is at the origin of the instability elongation perpendicular to steps. Quantitative agreement between the instability elongation and the anisotropy of strain relaxation is found, which deepens the understandings of hetero-epitaxial growth on vicinal substrate.In the fourth part we develop a new process based on Ge condensation during thermal oxidation of dilute SiGe. The kinetics of SiGe condensation process is investigated and the fully strained SiGe epilayer is fabricated via this particular condensation process. This process can be applied in fabrication of SiGe core-shell nanostructures, for which the direct deposition and growth process is found to be cumbersome in terms of the control of morphology and composition.As a whole, we studied the nanostructures of SiGe driven by its hetero-epitaxial elasticity. We proposed a model to compare two pathways of morphological evolution of SK growth and unearthed the mechanisms of the race and transition. We studied kinetics of island nucleation under the impact of elastic filed produced by an existing island. The peculiar role of strain-dependent surface energy is highlighted. Then the elasticity anisotropy induced by miscut steps on vicinal substrate is studied theoretically and experimentally. This anisotropy effectively induces the elongation of islands in one direction to form nanowires in good alignment. Then the kinetics of condensation of SiGe is studied, which is found to be an effective method in fabricating strained SiGe nanostructures
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Duff, Richard A. "Determination of bulk mechanical properties of nanostructures from molecular dynamic simulation." Thesis, Monterey, California. Naval Postgraduate School, 2003. http://hdl.handle.net/10945/994.
Повний текст джерелаАнотація:
Approved for public release; distribution is unlimitedDetermining bulk mechanical properties from microscopic forces has become important in the light of utilizing nano-scale systems. The molecular dynamics model was used to determine the modulus of elasticity and shear modulus of pure metallic micro lattice structures. Preliminary results indicate that the modulii of elasticity is determined to within 15% accuracy for 5 different metals of 500-atom structures when compared to the experiment values of bulk materials. Furthermore the elastic modulus for copper structures was computed with different temperatures, different magnitudes of stresses and various kinds of dislocations. From the preliminary results, it is concluded that the model accurately determines the mechanical properties of the nano-scale systems.
Outstanding Thesis
Canadian Navy author.
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Deplace, Fanny. "Waterborne nanostructured adhesives." Paris 6, 2008. http://www.theses.fr/2008PA066035.
Повний текст джерелаАнотація:
Nous avons étudié les propriétés d’adhésifs préparés à partir de particules de latex nanostructurées. Une méthodologie basée sur deux critères rhéologiques a été proposée pour optimiser les performances adhésives. Elle nous a permis d’identifier des stratégies applicables dans le cas particulier de PSA préparés à partir de particules de latex ayant une morphologie cœur-écorce. Une stratégie intéressante est l’activation d’une réaction de réticulation interparticule pendant le séchage du latex. Nous avons montré l’effet remarquable de cette réaction de réticulation sur les propriétés en grandes déformations. Ces propriétés sont assez bien décrites par un modèle non-linéaire combinant le modèle de Maxwell sur convecté et le modèle de Gent. Les meilleurs résultats d’adhésion sont obtenus pour des PSA préparés à partir de particules de latex ayant une fine écorce réticulée et un cœur mou et caractérisés par un net ramollissement à déformations intermédiaires suivi d’un rhéodurcissement. Dans un registre plus industriel, des performances adhésives prometteuses ont été obtenues avec des PSA préparés à partir de latex tackifiés in situ synthétisés par polymérisation en miniémulsion.
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BOIOLI, FRANCESCA. "Dislocation modelling in realistic Si-Ge nanostructures." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2013. http://hdl.handle.net/10281/40115.
Повний текст джерелаАнотація:
SiGe heterostructures have gained a lot of interests in view of developing devices integrated into the main-stream Silicon technology and also from a scientific point of view as a prototypical system to understand the properties of more complex systems, such as III-V semiconductors. Si-Ge epitaxial structures, as well as other mismatched heteroepitaxial materials, have a high potential to improve the state-of-the-art of Si devices, thanks to the fact that the strain modifies the band structures of this material class, opening new possibility of band-gap engineering.
Since the nineties, the development of devices having strained-SiGe layers as the active part occurred, in particular the heterojunction bipolar transistors, further developed to what is presently the fourth-generation of SiGe technology. Also the introduction of strained Si layers by using relaxed SiGe virtual substrates, is very important, for example, for the complementary metal–oxide–semiconductor (CMOS) technology.
In order to effectively exploit SiGe or strained-Si layers in any application, it is fundamental to growth high quality single crystalline materials, reducing as much as possible the defect density in the active volume and the surface corrugation, and to obtain the desired strain state in the epitaxial layers. However the possibility of using such heterostructures for any application, is hindered by the nucleation of dislocation, which is often an unavoidable strain-relief mechanisms. Dislocation formation affects both the final material quality and the relaxation degree of mismatched layers. These defects are often charged and act as non-radiative recombination centers and it is generally accepted that they are detrimental for opto-electronic devices based on Si-Ge semiconductors. In the past years, a lot of effort has been devoted reduce the defect density or to segregate dislocations in non-active regions. However, dislocation engineering, intended as the precise control of dislocation position, has always been a goal out of reach, because of the nucleation of such defects at unpredictable sites at the surface or at other heterogeneities. It is clear that predicting the extent of the plastic relaxation process and governing dislocation nucleation and positioning would be of the utmost importance.
Self-assembled nanoislands and nanowires, represent other novel heterostructures that can be exploited to obtain defect-free configurations with the desired strain state. Even in this case, very high stresses arise from the epitaxial integration of lattice mismatched materials and dislocation formation remains a competitive strain relief mechanism. Hence it is of fundamental importance to determine the coherency limits of such nanostructures and to elucidate the main strain relief mechanisms in the attempt to predict the final dislocation microstructure and strain state in heteroepitaxial systems.
The main goal of this work, is the understanding of the fundamental mechanisms of dislocation nucleation and propagation in Si-Ge nanostructures (i.e. films, nanoislands and nanowires) through dislocation modelling. Even if dislocation formation and motion relies on a sequence of discrete atomic displacements, such defects induce in a crystal a smooth deformation field in the entire structure. The elastic theory of dislocations provides a good description of such stress field and of the elastic energy, as produced by dislocations in bulk materials or in finite size solids with simple geometries. In order to assess the stresses and the energetics of plastically relaxed multifaceted structures, characterized by an high surface to volume ratio and typical length scale in the order of tens or hundreds of nanometers, linear elasticity theory numerically solved by finite element methods is the most suitable tool, since in this approximation the dislocation-surface interaction can be correctly taken into account. Moreover, the motion of dislocations in nanostructures can be handled by using three-dimensional dislocation dynamics simulations. This simulation technique, originally developed to study plasticity in bulk materials, has been demonstrated to give accurate results also for nanometric systems, and is the tool of choice to study the motion and interactions of a large density of dislocation in thin films or three-dimensional nanocrystals. Important properties determined by the atomistic nature of dislocations moving in a discrete lattice, can be included, both in the finite element calculations and in dislocation dynamics simulations, by adopting simple rules that take into account such atomistic features.
The first topic addressed in this work, is the investigation of plastic relaxation in SiGe epitaxial films aimed at governing dislocation nucleation and positioning. In particular, we show with the help of finite element calculations and dislocation dynamics simulations that a turning point to direct dislocation formation and propagation in predefined regions, is the introduction of preferential nucleation sites through substrate nanopatterning. Theoretical predictions indicating effective dislocation trapping along the features of trench- or pit-patterned substrates are discussed and compared with tailored experiments of SiGe deposition on nanopatterned substrate.
The second issue investigated here concerns self-assembled SiGe nanoislands. In these epitaxial nanostructures an intriguing mechanism of dislocation ordering is observed. In this work we reproduced such behavior by using a simple analytical model based on energetics considerations. Furthermore, the plastic relaxation onset for dislocation formation has been determined in epitaxial islands grown on pit-patterned substrates and nucleated in pits. The key factors influencing dislocation formation in such structures have been identified, opening new possibility to grow large defect-free islands on nanopattered substrates.
Finally, dislocation formation in core-shell nanowires has been considered. Elastic and plastic strain relaxaion has been investigated in such structures and a mechanism for dislocation nucleation and propagation in core-shell nanowires is presented. This allowed us to predict dislocation configurations that are more efficient in the strain relief process and the expected misfit dislocation pattern at the core-shell interface.
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Golushko, Ivan. "Micro- et nanostructures biologiques tubulaires : Mécanismes physiques de l'auto-assemblage et du fonctionnement." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS098/document.
Повний текст джерелаАнотація:
Les méthodes classiques de physique de l'état solide telles que la diffraction des rayons X et la microscopie électronique ont permis la compréhension de la structure des membranes cellulaires. Aujourd'hui, leur composition et structure étant bien connues, les recherches se concentrent sur les processus actifs des membranes. Des processus tels que l'endocytose impliquent des modifications substantielles de la forme des membranes lipidiques, réalisées par des protéines induisant la courbure membranaire. L'une des méthodes expérimentales parmi les plus populaires est dite « TLM-pulling », où la membrane lipidique tubulaire (TLM) est formée à partir de la vésicule en tirant par une force externe. Des structures similaires relient les vésicules endocytiques aux compartiments du donneur et servent de canaux pour le transfert de matière dans la cellule et entre les cellules adjacentes, établissant ainsi une voie de communication intercellulaire. De tels systèmes formés in vitro en raison de leur simplicité et grande homogénéité peuvent être décrits avec précision par la physique théorique.Dans la première partie de la thèse, nous développons un modèle théorique de TLM, basé sur la mécanique classique et la thermodynamique, et l'appliquons aux expériences de « TLM-pulling » avec adsorption de protéines induisant la courbure. Le modèle tient compte de l'asymétrie de la bicouche lipidique, de la tension superficielle, de la force longitudinale appliquée au TLM et de la différence de pression dans le système. Nous modélisons l'action que les protéines exercent sur la TLM via des ensembles de forces normales à la surface de la membrane à l'équilibre mécanique. Cette nouvelle approche multipolaire permet de modéliser les interactions anisotropes, entre les protéines adsorbées à la membrane, qui sont induites par sa déformation. Notre théorie décrit les premiers stades de la formation des échafaudages protéiques, c-à-d la disposition caractéristique des protéines et leur grande affinité avec les extrémités de la TLM. Le comportement collectif des protéines induisant la courbure est extrêmement important pour effectuer des déformations à grande échelle des membranes au cours de processus tels que l'endo et l'exocytose, l'entrée du virus dans la cellule hôte ainsi que la formation et la sortie des virions. L'étude de ce dernier processus pourrait conduire au développement de nouvelles méthodes de traitement en virologie.La deuxième partie de la thèse est consacrée à l'étude de l'aorte dorsale (DA) de l'embryon de poisson Danio-Rerio. On étudie l'évolution de la forme du DA pendant la transition endothélio-hématopoïétique (EHT). Le processus EHT conduit à l'extrusion des cellules souches/hématopoïétiques qui coloniseront en suite la moelle osseuse permettant l'hématopoïèse tout au long de la vie. Ce processus semble être universel et devrait s'appliquer aussi bien aux mammifères qu'aux oiseaux, ce qui fait de son étude un problème fondamental de l'embryologie.Le DA a une géométrie cylindrique et semblable aux TLM, mais en même temps, il est beaucoup plus gros que les tubes lipidiques, a un module de cisaillement non nul et est incorporé dans la matrice des tissus environnants : un système beaucoup plus complexe du point de vue mécanique. Nous relions les changements globaux de forme de l'aorte pendant l'EHT aux principes génériques de la mécanique et montrons que les instabilités mécaniques conduisant à l'évolution de la forme de l'aorte sont invoquées par des stress résultant des inhomogénéités de croissance et de l'interaction avec les tissus environnants. Sur la base de l'analyse théorique et des données en microscopie confocale 4D, nous proposons un schéma détaillé du processus et postulons que les instabilités mécaniques préparent l'ensemble du processus EHT avant son contrôle génétique spécifique, suggérant un mécanisme universel et auto-organisé du processus de réorganisation collective des tissus dans les organismes en croissanceApplications of classical solid state physics methods such as X-ray diffraction analysis and electron microscopy allowed making a giant step in understanding of cellular membranes’ structure. Today since their composition and structure are well known, the focus of research has shifted to active processes involving cell membranes. As we know, such processes as endocytosis involve substantial shape changes of cell membranes, which are performed by curvature-inducing proteins. One of the most popular methods to study how these proteins interact with lipid membranes and each other is TLM-pulling experiment, where tubular lipid membrane (TLM) is formed from the vesicle by pulling. Similar structures connect endocytic vesicles with the donor compartments and serve as channels for the matter transfer within the cell and between adjacent cells establishing cell-to-cell communication pathway. Such systems formed in vitro due to their simplicity and high homogeneity can be accurately described by the means of theoretical physics.In the first part of the present thesis, we develop a theoretical model of the TLM pulled out of the vesicle on the basis of classical mechanics and thermodynamics and apply it to the TLM-pulling experiments with curvature-inducing proteins adsorption. The developed model takes into account asymmetry of the lipid bilayer, surface tension, longitudinal force applied to the TLM and pressure difference in the system. We model the action that proteins exert on TLM via sets of forces normal to the membrane’s surface and satisfying conditions of mechanical equilibrium. This novel force multipole approach allows us to model anisotropic interactions between proteins adsorbed at the membrane surface that are induced by the membrane deformation. Our theory describes early stages of protein scaffolds formation i.e. characteristic arrangement of proteins and their high affinity to the membrane ends. Collective behavior of curvature-inducing proteins is extremely important for performing large scale deformations of lipid membranes during such processes as endo and exocytosis, virus entry in the host cell as well as formation and exit of daughter virions later on. Studying of the latter process can possibly lead to the development of fundamentally new methods of viral disease treatment.The second part of the thesis is devoted to the study of zebrafish embryo’s dorsal aorta (DA). It focuses on DA’s shape evolution during the Endothelio-Haematopoietic Transition (EHT). The EHT process leads to the extrusion of haematopoietic stem/progenitor cells (HSPCs) which will later on colonize haematopoietic organs allowing haematopoiesis throughout adult life. This process seems to be universal and should also apply for both mammals and birds, which makes its investigation a fundamental problem of embryology.DA has a cylindrical geometry that makes it similar to the TLM’s, however at the same time DA is much bigger than lipid tubes, has a non-zero share modulus and is embedded in the matrix of surrounding tissues, which makes it a much more complex system from the mechanical perspective. We relate the global shape changes of the aorta during EHT to generic principles of mechanics and show that mechanical instabilities leading to the aorta shape evolution are invoked by different stresses resulting from the growth inhomogeneities and interaction with surrounding tissues. Based on the performed theoretical analysis and the data obtained with a help of 4D confocal microscopy we propose a detailed scheme of the process and postulate that mechanical instabilities prepare and support the whole EHT process prior to its specific genetic control. Our interpretation suggests a universal and self-organized mechanism underlying collective tissue reorganization processes in the growing organisms such as EHT
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Dingreville, Remi. "Modeling and Characterization of the Elastic Behavior of Interfaces in Nanostructured Materials: From an Atomistic Description to a Continuum Approach." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19776.
Повний текст джерелаАнотація:
Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Jianmin Qu; Committee Member: David McDowell; Committee Member: Elisa Riedo; Committee Member: Min Zhou; Committee Member: Mo Li.
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ZEN, HELOISA A. "Desenvolvimento de elastômeros fluorados multifuncionais baseados em nanocompósitos." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23741.
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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Gupta, Prakhar. "Elasticity of one-dimensional nanostructures - a multiscale approach." Thesis, 2018. http://localhost:8080/xmlui/handle/12345678/7621.
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Ben, Xue. "Opto-mechanical coupling effects on metallic nanostructures." Thesis, 2015. https://hdl.handle.net/2144/16036.
Повний текст джерелаАнотація:
Surface plasmon is the quantized collective oscillation of the free electron gas in a metallic material. By coupling surface plasmons with photons in different nanostructures, researchers have found surface plasmon polaritons (SPP) and localized surface plasmon resonance (LSPR), which are widely adopted in biosensing, single molecule sensing and detection via surface enhanced raman scattering (SERS), photothermal ablation treatments for cancer, optical tagging and detection, strain sensing, metamaterials, and other applications.
The overall objective of this dissertation is to investigate both how mechanics impacts the optical properties, and also how optics impacts the mechanical properties of metal nanostructures reversely. Mechanically engineering individual nanostructures(forward coupling) offers the freedom to alter the optical properties with more flexibility and tunability. It is shown that elastic strain can be applied to gold nanowires to reduce the intrinsic losses for subwavelength optical signal processing, leading to an increase of up to 70% in the surface plasmon polariton propagation lengths at resonance frequencies. Apart from strain engineering, defects are another important aspect of mechanically engineering nanoscale materials, whose impacts on the optical properties of metal nanostructures remain unresolved. An atomic electrodynamic model has been derived to demonstrate that those effects are crucial for ultrasmall nanoparticles with characteristic sizes around 2 nm, and can be safely ignored for those larger than about 5 nm due to the important contribution of nanoscale surface effects.
Another key focus of this research project (reverse coupling) is to investigate the currently unknown effects that an external optical field has on the mechanical properties of metal nanostructures. Since each atom in the nanostructure acts as a dipole due to induced electron motions, this optical excitation introduces additional dipolar forces that add to the standard mechanical atomic interactions, which could alter the mechanical properties of the nanostructures. Furthermore, it is shown that when linking mechanics with LSPR, because the metal is dispersive, the mechanical behavior or the strength of the nanostructure should be dependent on the frequency of the electromagnetic excitation. To study this phenomenon, a simpler case with an electrostatic field excitation is considered first, and conclusions are reached on how static fields can be used to tune the elasticity of metallic nanostructures with different sizes and axial orientations and surfaces. Then building upon those understandings, studies were carried out in determining the effects of an optical field, specifically at LSPR frequency, on the mechanical properties of metallic nanostructures. It is found that the initial relaxation strain induced by the static field or optical field is the key factor leading to the variations in the stiffness of the metallic nanostructures that are excited by optical fields at the LSPR frequencies.
Книги з теми "Elasticity- Nanostructure"
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1933-, Fenster Saul K., ed. Advanced strength and applied elasticity. 4th ed. Upper Saddle River, N.J: Prentice Hall PTR, 2003.
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1933-, Fenster Saul K., ed. Advanced strength and applied elasticity. 3rd ed. Upper Saddle River, N.J: Prentice Hall, 1995.
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3
Ugural, A. C. Advanced strength and applied elasticity. 2nd ed. New York: Elsevier, 1987.
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4
Djunisbekov, T. M. Stress relaxation in viscoelastic materials. Enfield, NH: Science Publishers, 2003.
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5
Ieşan, Dorin. Thermoelastic deformations. Dordrecht: Kluwer Academic, 1996.
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6
Advanced Strength and Applied Elasticity: 2nd SI Edition. 2nd ed. Longman Higher Education, 1992.
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7
François, Dominique, André Pineau, and André Zaoui. Mechanical Behaviour of Materials: Volume I: Elasticity and Plasticity (Solid Mechanics and Its Applications). Springer, 1998.
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8
Junisbekov, T. M., V. N. Kestelman, and N. I. Malinin. Stress Relaxation in Viscoelastic Materials. Science Publishers, 2002.
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9
Iesan, D., and A. Scalia. Thermoelastic Deformations (Solid Mechanics and Its Applications). Springer, 1996.
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10
Scalia, Antonio, and D. Iesan. Thermoelastic Deformations. Springer, 2010.
Знайти повний текст джерелаЧастини книг з теми "Elasticity- Nanostructure"
1
Gopalakrishnan, Srinivasan, and Saggam Narendar. "Theory of Nonlocal Elasticity." In Wave Propagation in Nanostructures, 59–70. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-01032-8_4.
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2
Malikan, Mohammad, and Victor A. Eremeyev. "Free Vibration of Flexomagnetic Nanostructured Tubes Based on Stress-driven Nonlocal Elasticity." In Analysis of Shells, Plates, and Beams, 215–26. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-47491-1_12.
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Moreira de Sousa, José. "Nanostructures Failures and Fully Atomistic Molecular Dynamics Simulations." In Elasticity of Materials [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.100331.
Повний текст джерелаАнотація:
Nowadays, the concern about the limitations of space and natural resources has driven the motivation for the development of increasingly smaller, more efficient, and energy-saving electromechanical devices. Since the revolution of “microchips”, during the second half of the twentieth century, besides the production of microcomputers, it has been possible to develop new technologies in the areas of mechanization, transportation, telecommunications, among others. However, much room for significant improvements in factors as shorter computational processing time, lower energy consumption in the same kind of work, more efficiency in energy storage, more reliable sensors, and better miniaturization of electronic devices. In particular, nanotechnology based on carbon has received continuous attention in the world’s scientific scenario. The riches found in different physical properties of the nanostructures as, carbon nanotubes (CNTs), graphene, and other exotic allotropic forms deriving from carbon. Thus, through classical molecular dynamics (CMD) methods with the use of reactive interatomic potentials reactive force field (ReaxFF), the scientific research conducted through this chapter aims to study the nanostructural, dynamic and elastic properties of nanostructured systems such as graphene single layer and conventional carbon nanotube (CNTs).
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Ebrahimi, Farzad, and Ali Dabbagh. "An Introduction to Nonlocal Elasticity Theories and Scale-Dependent Analysis in Nanostructures." In Wave Propagation Analysis of Smart Nanostructures, 7–12. CRC Press, 2019. http://dx.doi.org/10.1201/9780429279225-2.
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Barretta, Raffaele, Francesco Fabbrocino, Francesco Marotti de Sciarra, Raimondo Luciano, Francesco Giuseppe Morabito, and Giuseppe Ruta. "Modulated Linear Dynamics of Functionally Graded Nanobeams With Nonlocal and Gradient Elasticity." In Experimental Characterization, Predictive Mechanical and Thermal Modeling of Nanostructures and their Polymer Composites, 293–323. Elsevier, 2018. http://dx.doi.org/10.1016/b978-0-323-48061-1.00009-9.
Повний текст джерелаТези доповідей конференцій з теми "Elasticity- Nanostructure"
1
Gurmendi, U., J. I. Eguiazabal, and J. Nazabal. "Structure and Properties of Nanocomposites With a Poly(Ethylene Terephthalate) Matrix." In ASME 2006 Multifunctional Nanocomposites International Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/mn2006-17087.
Повний текст джерелаАнотація:
Polymer nanocomposites based on poly(ethylene terephthalate) PET and with an intercalated and fairly dispersed nanostructure have been obtained in the melt state using a twin screw extruder. The intercalation and dispersion levels as well as the mechanical properties were studied varying the chemical nature and amount of the organic modification of the clay as well as the clay content. The intercalation level of PET into the organoclay galleries was measured by the increase in the interlayer distance upon mixing. The surfactant content did not influence the intercalation level but an interaction between the polymeric matrix and the surfactant, through a common polar character led to easier intercalation. The observed modulus increases and consequently the overall dispersion did not almost depend on either the amount or chemical nature of the used organic modification of the clay, suggesting that the parameters leading to high intercalation differ from those lead to a high modulus of elasticity and therefore to a high dispersion level. The obtained increases in the modulus of elasticity that reflect the dispersion level were large attaining a 41% increase with respect to that of the matrix after a 6wt% clay addition.
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Łepkowski, S. P., J. A. Majewski, and G. Jurczak. "Effects of Nonlinear Elasticity in Nitride Semiconductors and their Nanostructures." In PHYSICS OF SEMICONDUCTORS: 28th International Conference on the Physics of Semiconductors - ICPS 2006. AIP, 2007. http://dx.doi.org/10.1063/1.2729909.
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Zarrin, Tahira, Rahul Ribeiro, Sumanth Banda, Zoubeida Ounaies, and Hong Liang. "Effect of SWCNT on Tribological Behavior of Polymeric Nanocomposite." In STLE/ASME 2008 International Joint Tribology Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/ijtc2008-71282.
Повний текст джерелаАнотація:
The nanoscale structure of single-walled carbon nanotubes (SWCNTs) has unique properties. These nanostructured additives can induce unusual characteristic in many polymer matrix. In one of our recent experiments, it was found that when adding SWCNTs into a polyimide (PI) matrix, friction becomes a function of the concentration of the additive. In this research, we analyze the behavior of the SWCNTs-PI nano-composite using an approximation approach. We report that the frictional behavior of the nanocomposite is dominated by the elastic and plastic deformation through randomly dispersed SWCNTs under different loading conditions. At low concentration of SWCNTs, its elasticity dominates the properties of composite while at higher concentration, plastic behavior of tubes plays a major role in describing the properties of composite.
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van Rooyen, Isabel J., Jan H. Neethling, and Johannes Mahlangu. "Influence of Temperature on the Micro- and Nanostructures of Experimental PBMR TRISO Coated Particles: A Comparative Study." In Fourth International Topical Meeting on High Temperature Reactor Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/htr2008-58189.
Повний текст джерелаАнотація:
The PBMR fuel consists of TRISO Coated Particles (CPs) in a graphite matrix. The three layer system, IPyC-SiC-OPyC, forms the primary barrier to fission product release, with the SiC layer acting as the main pressure boundary of the particle. The containment of fission products inside the CPs is however a function of the operating temperature and microstructure of the SiC layer. During accident conditions, the CPs will reach higher temperatures than normal operating conditions. The Fuel Design department of PBMR is therefore investigating various characteristics of the SiC layer, especially nano characteristics at variant conditions. The integrity of the interface between the SiC and Inner PyC layers is also important for fission product retention and therefore interesting TEM images of this region of the experimental PBMR TRISO particles will be shown. Transmission electron microscope (TEM) images of the microstructure of TRISO coated particles of three different experimental batches after annealing will be discussed. Particles annealed at 1980°C for 1 hour revealed that the inner PyC layer debonded from the SiC layer. Changes observed in the diffraction rings are evidence that the PyC structure is becoming organized or anisotropic. The SiC layer, on the other hand, did not show any changes as a result of annealing. Only the cubic 3C-SiC phase was observed for a limited number of grains analyzed. The nano hardness and elasticity measurements of the three test batches were done using a CSM Nano Hardness Tester. These results are compared to indicate possible differences between the 1 hour and 5 hour annealing time as a function of annealing temperature from 1000°C to 1980°C. The variation of hardness and elasticity as a function of temperature for the three experimental batches are identified and discussed. This preliminary TEM investigation and nano hardness measurements have contributed new knowledge about the effect of high temperature annealing on the microstructure of TRISO CPs produced by PBMR.
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Kuo, M. K., T. R. Lin, and K. B. Hong. "Size and Piezoelectric Effects on Optical Properties of Self-Assembled InGaAs/GaAs Quantum Dots." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15776.
Повний текст джерелаАнотація:
Size effects on optical properties of self-assembled quantum dots are analyzed based on the theories of linear elasticity and of strain-dependent k-p with the aid of finite element analysis. The quantum dot is made of InGaAs with truncated pyramidal shape on GaAs substrate. The three-dimensional steady-state effective-mass Schro¨dinger equation is adopted to find confined energy levels as well as wave functions both for electrons and holes of the quantum-dot nanostructures. Strain-induced as well as piezoelectric effects are taken into account in the carrier confinement potential of Schro¨dinger equation. The optical transition energies of quantum dots, computed from confined energy levels for electrons and holes, are significantly different for several quantum dots with distinct sizes. It is found that for QDs with the the larger the volume of QD is, the smaller the values of the optical transition energy. Piezoelectric effect, on the other hand, splits the p-like degeneracy for the electron first excited state about 1~7 meV, and leads to anisotropy on the wave function.