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Showing 1 to 20 of 31 for “"Ostwald ripening"”.
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Adatom Emission From Nanoparticles: Implications for Ostwald Ripening
To achieve clean air in our cities, all modern means of ground transportation make use of catalytic converters. Precious metal-based catalysts such as Pt and Pd are currently used in catalytic converters. To achieve higher fuel efficiency, combustion can be carried out in excess air resulting in a …
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Nucleation Control in Size and Dispersity in Metallic Nanoparticles: The Prominent Role of Particle Aggregation
… active-growth regime extends to 58 min, and that Ostwald ripening ensues shortly thereafter. Evidence for an aggregative nucleation and growth process is obtained. The quantitative data indicate that classical nucleation and growth, aggregative nucleation and growth, and Ostwald ripening occur in …
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Structure and Phase Transformation of Nanocrystalline and Amorphous Alloy Thin Films
… phenomenon can be explained by grain growth and Ostwald ripening in which big clusters grows bigger at the expense of smaller clusters. The Ag clusters remain relatively stable under annealing; HREM images show crystalline structure at 500°C, which is different from Ag clusters supported on …
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Model electrode structures for studies of electrocatalyst degradation
… to occur by four mechanisms; particle sintering (Ostwald ripening and migration and coalescence), carbon corrosion and catalyst dissolution. Increasing catalyst layer durability is becoming a major challenge and a growing focus of research attention in PEM fuel cell durability studies. Typical …
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The plastic deformation of alloys based on aluminum titanide
… has been developed which describes accelerated Ostwald ripening at moving interfaces. Isothermal and isochronal annealing experiments have been executed on rapidly solidified materials with results which are consistent with the presented predictions.
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Formulación y caracterización de emulsiones de de limoneno estabilizadas por un tensioactivo polimérico
… inhibe el crecimiento del tamaño de gota por Ostwald ripening obteniéndose un sistema coloidal altamente estable. Esta tesis está formada por cinco capítulos. El primer capítulo introduce los principales concepto de la ciencia y tecnología de emulsiones así como el estado del arte de los …
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Layered Double Hydroxides: Morphology, Interlayer Anion, and the Origins of Life
… morphological issues using techniques such as Ostwald ripening and precipitation via aluminate. Another interesting issue in layered double hydroxide materials is the uptake and orientation of anions into the interlayer. Questions about iron cyanide interlayer anions have been posed. Fourier …
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Developing a New Mechanical Model for Swarm Development in Myxococcus xanthus & Establishing a Genotype-to-Phenotype Correlation Between Swarm Pattern Formation and Gene Homology
… work, we demonstrate that equations describing Ostwald ripening within a thin liquid film were able to predict aggregate behavior with high accuracy. Consistent with this theory, both relative aggregate size and the distance between aggregates influence the likelihood that a given aggregate will …
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Pyrite porphyroblast paragenesis at the Cherokee Mine, Ducktown, Tennessee
… the formation of the larger porphyroblasts by Ostwald ripening, and by the annealing of small pyrite grains into larger porphyroblasts, during isochemical metamorphism. Sphalerite geobarometry indicates initial growth of the pyrite porphyroblasts began at 6.8± 0.8 kilobars and that many …
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Investigations of carbon nanotube catalyst morphology and behavior with transmission electron microscopy
… particle used in common CNT growth procedures. Ostwald ripening studies on iron nanoparticles are performed in an attempt to link catalyst morphology during growth and CNT chirality (the structure aspect of a nanotube that determines its electrical properties). These results suggest that inert …
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Clay mineral catalysed oxidation of phenols
… probably, their higher degree of defects as full Ostwald ripening has not yet occurred. Substituted phenols appear to be degraded very rapidly. However, further work needs to be done in this area to ascertain the effect that substituents have on the rate of reaction.
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A variable temperature scanning tunneling microscopy study of organizing C60 molecules on nanostructured gold surface
… Diffusion is activated at ~160 K leading to ripening of the C\(_{60}\) molecular structures. At higher temperatures, when a large number of C\(_{60}\) molecules are released from the elbow sites, C\(_{60}\) clusters with a magic number of seven are formed. These clusters only diffuse within …
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Bubble dynamics in polymeric foams
… the surface tension driven phenomenon known as Ostwald Ripening causes large bubbles to grow at the expense of smaller ones. For the case of bubbles of two different sizes we examine the effects of viscoelasticity on the shapes of the bubbles within the structure and show that viscoelasticity …
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A Study of the Kinetics of Phase Separation in a Nickel-12.5 at.percent Silicon Alloy
… experimental observations agree well with the Ostwald ripening theory of Lifshitz, Slyozov and Wagner. The particle growth kinetics shows a transition from an earlier growth stage, where a parabolic growth rate is in effect, to a classical coarsening stage. Enhanced diffusion, due to …
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Microstructural evolution of silicate immiscible liquids in solidifying ferrobasalts
… occurs by diffusion-controlled growth (including Ostwald ripening), with an insignificant contribution from coalescence. The experimental observations are scaled to infer that in magma bodies < ~10 m in size, gravitationally-driven segregation of immiscible Fe-rich droplets is unlikely to be …
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Surface chemistry to control bulk reaction dynamics of native point defects in rutile titanium dioxide
… surface configuration, foreign adsorbates) and Ostwald ripening kinetics of bulk extended defects. Oxygen and titanium interstitials in rutile titanium dioxide are primarily sequestered at bulk extended defects that are sometimes distributed in a spatially-dependent way. Pertinent kinetic …
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Hemmung der Eisrekristallisation in wässrigen Lösungen durch Antigefrierglykopeptide
… was determined using a special form of Ostwald ripening, namely, the ice recrystallization of polycrystalline ice in aqueous solutions. Experiments on the kinetics of ice recrystallization were conducted for determining the influence of factors such as temperature and ice volume fraction …
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Multiphase flow in porous media with phase transitions : from CO₂ sequestration to gas hydrate systems
… and hydrodynamic instability can arrest the Ostwald ripening process characteristic of nonflowing mixtures; (2) partial miscibility exerts a powerful control on the degree of viscous fingering in a gas-liquid system, whereby fluid dissolution hinders fingering while fluid exsolution enhances …
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The effect of vanadium oxidation states on the conversion of hydrogen sulphide to elemental sulphur
… interfered with the sulphur sol nucleation and Ostwald ripening process. The nucleation and Ostwald ripening process facilitates the formation of coarse elemental sulphur. However, the elemental sulphur formed during the experimental work was crystalline and melted at approximately 122°C, which …
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Correlation of the microstructure and processing conditions of ultra-thin oxygen-implanted silicon-on-insulator materials
… with increasing temperature, an indication of Ostwald ripening. The effect of final annealing temperature and surface capping on the microstructure were also investigated. Annealing at 1300°C for 6 hours restored completely the crystal quality of the top Si layer and produced a continuous and …
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