Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 62 for “"heterogeneous nucleation"”.
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Heterogeneous nucleation in polymer crystallization
… boron nitride, saccharin and sorbitol on the nucleation and crystallisation of PP, PE, PB, POM, PHB, PET and Nylon 66 has been investigated by DSC, light microscopy and electron microscopy. The effectiveness of the nucleating agent has been evaluated by the study of the interfacial layer …
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Understanding Heterogeneous Nucleation Mechanisms in Polyolefins
… predictive power. Experimental methods to study heterogeneous nucleation are often plagued with confounding factors that lead to uncertainty in the measured kinetics and thermodynamics of nucleation. Molecular simulations have recently showed promise to investigate the nano time- and length- …
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Effect of ionic strength on heterogeneous nucleation of calcite during biomineralization
… are inert. In this study, we investigate calcite nucleation onto two model organic matrix polysaccharides, chitosan and alginate, in a series of ionic strength solutions (65 – 600 mM NaCl). Chitosan is near-neutral (at pH 8.5) and analogous to the structural polysaccharide chitin. In contrast, …
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Enhanced heterogeneous nucleation on oxides in Al alloys by intensive melt shearing
… refinement has been attributed to the enhanced heterogeneous nucleation on the dispersed oxide particles. It has been established that the naturally occurring oxides in molten Al alloys normally have a good crystallographic match with the a-Al phase, indicating the high potency of oxide …
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Heterogeneous nucleation of active pharmaceutical ingredients on polymers : applications in continuous pharmaceutical manufacturing
… and fabricating PVA film surfaces for increasing heterogeneous nucleation rate of different compounds and enable polymorph selection. The design philosophy was to select prevalent angles between major faces of crystals according to a selection of compounds, and to create substrate surfaces with …
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Binding affinity of a small molecule to an amorphous polymer in a solvent
… in industrial practice. It usually begins with heterogeneous nucleation on a foreign surface. The complicated mechanism of heterogeneous nucleation is not well understood, but we hypothesize a possible correlation between binding affinity to a surface and nucleation enhancement. Amorphous …
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Study of nucleation mechanisms and rational design of small-scale continuous crystallizers
… Crystallization is a two-step process: nucleation (birth of crystals) and crystal growth. Nucleation can occur via several mechanisms, and the most industrially relevant ones are heterogeneous nucleation (nucleation on a foreign surface), and contact secondary nucleation (nucleation from …
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Re-evaporation nuclei and evaporation in a Wilson cloud chamber
… effect.</p> <p>The theories of evaporation and nucleation on submicroscopic drop residues were re-examined, and alterations which appear to be consistent with the results of this work were incorporated into the evaporation theory.</p> <p>The observed continually decreasing evaporation rate with …
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Design of polymeric substrates for controlled molecular crystallization
… circumstances, crystallization starts with heterogeneous nucleation at a foreign surface. Despite its widespread occurrence, mechanistic understanding of the role of a surface in heterogeneous nucleation is limited, especially in a solution environment. My thesis aims at elucidating the …
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Molecular modeling of polymer crystallization and the effect of nucleating agents
… presents new molecular evidence of surface nucleation processes that contribute to the propagation of the crystal growth front in a macromolecular system. Crystallization in polymeric systems has long been theorized to proceed by "secondary nucleation." In this work, molecular dynamics (MD) …
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Crystallization of calcium oxalate on molecularly imprinted polymer surfaces
… most common component of human kidney stones. Heterogeneous nucleation is regarded as the key mechanism in this process. As such, crystallization of this substance has been studied in several different model systems. However, molecular imprinting has not been previously used in this field. In …
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Phase behaviour and crystal nucleation in complex multicomponent system
… for high control of product quality attributes. Nucleation is a key phenomenon in crystallisation that can control product purity, morphology and crystal size distribution. Despite the use of co-crystallisation in manner mentioned above, not a lot is known about nucleation kinetics in …
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Mechanisms of Cell Nucleation, Growth, and Coarsening in Plastic Foaming: Theory, Simulation, and Experiment
… highlights a comprehensive research for the cell nucleation, growth and coarsening mechanisms during plastic foaming processes. Enforced environmental regulations have forced the plastic foam industry to adopt alternative blowing agents (e.g., carbon dioxide, nitrogen, argon and helium). …
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Oxygen precipitate studies in silicon for gettering in solar cell applications
… a process called internal gettering) as sites of heterogeneous nucleation of precipitates of iron and other transition metal that are harmful to solar cell device operation. Oxygen precipitate densities in p- (10¹⁴ boron atoms/cm³) wafers were quantified using chemical etch techniques. The …
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Condensation and sublimation of carbon dioxide and water molecules at cryogenic temperatures
… investigated. The results are explained using heterogeneous nucleation theory for low density population, and a new approach for high density population is presented. The rate of sublimation of these two gases was measured directly. The results are reported in terms of vapor pressure in the …
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Pulsed-Laser-Induced Melting and Solidification of Thin Metallic Films
… films on SiO2, and (2) investigation of oriented heterogeneous nucleation via complete melting and subsequent nucleation-initiated solidification of Ni films on SiO2. The work on SLS of Cu films is motivated in large part by the need to improve the properties of Cu films which, among other …
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Thermodynamic stability and implications of anisotropic boundary particles
… larger boundary energy density. The steady-state heterogeneous nucleation rate is increased when facets appear on the nucleus, but the increase is diminished if the boundary distorts. A corollary result presented in this thesis, that particles can induce rotations or ser- ration through torques, …
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An experimental determination of the homogeneous nucleation rate of water vapor in argon and helium
… type cloud chamber was used to measure the nucleation rate of water vapor in an atmosphere of helium and argon. A careful study was made of the thermodynamic characteristics during the expansion so that the nucleation data could be interpreted with reasonable accuracy and consistency. A fine …
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Condensation Frosting: From Ice Bridges to Dry Zones
… condensate population freezes in isolation by heterogeneous nucleation at the solid-liquid interface, quite analogous to the mechanism of icing. This assumption has very recently been invalidated with strong experimental evidence which shows that only a single droplet has to freeze by …
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