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 35 for “"homogeneous nucleation"”.
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Homogeneous nucleation of water vapor in inert gas atmospheres
"The homogeneous nucleation of water vapor in atmospheres of helium, neon, argon, krypton, and xenon was studied using an expansion type cloud chamber. A strong dependence of the nucleation rate on the particular inert carrier gas was observed. At present the only dependence upon the nature of the …
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Homogeneous nucleation and growth of silicon powder from laser heated gas phase reactants
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1983.
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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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Direct energy landscape sampling of the homogeneous nucleation and crystal growth of a model liquid
… step in the synthesis of any material is the nucleation of the material's phase. Nucleation and crystal growth are understood to be activated processes involving the crossing of free-energy barriers. Attempts to capture the entire crystallization process over long timescales with molecular …
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The development of h Homogeneous nucleation rate model for thermoplastic foams based on a molecular partition function and Fickian diffusion
An improved homogeneous nucleation rate model for thermoplastic foams has been developed. This model does not rely on experimentally determined parameters and only uses pure component physical property data and a binary diffusion coefficient. This model, like those derived from classical nucleation …
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Vapor phase clustering model for water
"Although nucleation phenomena are among the most widespread of all naturally occurring phenomena, even the simplest of nucleation processes, homogeneous nucleation, is poorly understood, particularly the homogeneous nucleation of liquid droplets from water vapor. Homogeneous nucleation involves …
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A computational investigation of nucleation processes in organic crystals
Nucleation processes are ubiquitous in nature and technology. For instance, cloud formation in the atmosphere, the casting of metals, protein crystallization, biomineralization, the production of porous materials, and separation of pharmaceutical compounds from solution are a few examples of …
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Microstructure and Microchemistry of Rapidly Solidified Nickel-Base Powders
… powder particles using Newtonian cooling, homogeneous nucleation, and growth theories. The results of these calculations were compared to experimental observations in order to develop an understanding of the mechanisms of solidification in rapidly quenched powders.
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Theory of nucleation of water properties of some clathrate like cluster structures
"The tranquility of classical homogeneous nucleation theory has been disturbed by the introduction of statistical mechanical correction factors to a basically thermodynamic theory. These factors, which appear to be essential, destroy much of the agreement with experiment in the case of water vapor. …
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Neutron scattering investigations on the liquid-liquid transition in deeply cooled confined water
… difficult due to the crystallization below the homogeneous nucleation temperature (~232 K at atm). It is found that, by confining water in a hydrophilic nanoporous material, MCM-41, the homogeneous nucleation process can be avoided, which allows us to keep water in liquid state at least down to …
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An investigation of the dynamics of phase transitions in Lennard-Jones fluids
… with the interpretation of our results using homogeneous nucleation theory. We find that our results are consistent with homogeneous nucleation which predicts that phase separation starts at the nanoscopic level with critical radii of the order of a few nanometers for both evaporation and …
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Shear-induced homogeneous deformation twinning in FCC aluminum and copper via automistic simulation
… deformation twins are shown to form by homogeneous nucleation, slip and subsequent coalescence of partial dislocations in both copper and aluminum. The minimum energy path for formation of a two-layer microtwin, and the energy barriers to its further growth are analyzed for the two …
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Measurements and modeling of deposition rates from near-supercritical, aqueous, sodium sulfate and potassium sulfate solutions to a heated cylinder
… an understanding of salt deposition kinetics and nucleation phenomena at conditions relevant to SCWO. Solubility and deposition experiments were performed with aqueous sodium sulfate and aqueous potassium sulfate solutions at elevated temperatures and pressures typical of the SCWO process. For …
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Nanoscale solidification of metals by atomistic simulations: From nucleation to nanostructural evolution
<p>"Homogeneous nucleation during solidification in Al (fcc), Fe (bcc) and Mg (hcp) is studied by million-atom molecular dynamics (MD) utilizing the second nearest neighbor modified embedded atom method (2NN-MEAM) potentials. Spontaneous homogenous nucleation from the melt was produced without any …
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Microphysics of atmospheric aerosols : phase transitions and cloud formation mechanisms
… (cirrus) form when ice is nucleated either homogeneously or heterogeneously in aqueous aerosols. We have investigated the homogeneous and heterogeneous ice nucleation in aqueous particles. Our results for homogeneous nucleation in aqueous ammonium nitrate particles show that the current …
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Predictive model for plume opacity
… and growth. These processes result from homogeneous nucleation, condensation and coagulation which substantially increase the concentration of submicrometer sized aerosols. These phenomena bring about significant increases in plume opacity. Theoretical relationships have been derived and …
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Theoretical study of nanoparticle formation in thermal plasma processing Nucleation, coagulation and aggregation
… The nanoparticle formation is considered by homogeneous nucleation and the growth is caused by condensation and Brownian coagulation. The growth of fractal aggregates is considered by introducing a power law exponent Df. Transport of nanoparticles occurs by convection, thermophoresis and …
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Fundamental research regarding the ultrasonic stirring effects on the microstructure of A356 castings
… processing. Besides, more energy is required for homogeneous nucleation to occur. Consequently, the dominant mechanism of nucleation in this research is heterogeneous nucleation. The microstructure and mechanical properties of the A356 alloy processed with and without UST were analyzed and …
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The Formation of Distal Impact Ejecta
… treated by directly coupling the equations for homogeneous nucleation and growth with our hydrocode. The second model is focused on less energetic material ejected as part of the excavation flow. Using the iSALE hydrocode, we determine the details of the excavation flow and formation of the …
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