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.
Results
Showing 1 to 20 of 49 for “"nucleation rate"”.
-
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 …
-
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 …
-
A Monte Carlo study of the scaling of nucleation rates in a Lennard-Jones system
… scaling of the homogenous vapor-to-liquid nucleation rate, J, is examined in a model Lennard-Jones (LJ) system. The model uses the Bennett Metropolis Monte Carlo technique to determine small cluster growth/decay rate constant ratios ß<sub>n-1</sub>|α<sub>n</sub> at four temperatures (T = …
-
Precipitation of ultrafine particles using liquid antisolvent with concentric ultrasonic nozzle and subcritical CO2
… particles. Ultrasound is used to increase the nucleation rate by enhancing the micro mixing of solvent and antisolvent stream and decrease the agglomeration. Surfactants and polymers are used to reduce the surface tension and thereby increase the nucleation rate. Use of additives can inhibit …
-
Analysis of nucleation kinetics in pH-shift crystallization using agitated and microfluidic systems
Crystal nucleation is a key event in the process of crystallization and is important in a number of processes in the pharmaceutical industry. Nucleation kinetics impact the crystal quality attributes of the product of a crystallization process. For example, increased crystal nucleationrate can lead …
-
Nucleation of the isothermal martensitic transformation in iron-nickel-manganese alloys
… detectable amount of martensite) and the initial nucleation rate have been determined as a function of subzero reaction temperature and austenitic grain size in three iron-nickel manganese alloys containing 23-25 percent nickel, 2-3 percent manganese and 0.02-0.04 percent carbon. The isothermal …
-
Nucleation Control in Size and Dispersity in Metallic Nanoparticles: The Prominent Role of Particle Aggregation
… is to investigate the effect of aggregative nucleation and growth on the final size and dispersity in metallic nanoparticle systems. Aggregative nucleation functions are determined for the first time for three nanocrystal systems, namely gold: Au), silver: Ag) and bismuth: Bi). These …
-
Molecular dynamics modeling of orientation-induced nucleation in short alkanes : toward molecular modeling of flow-induced crystallization in polymers
The enhancement of the primary flow-induced nucleation rate in short chain alkanes (C20 and C150) has been examined for different levels of orientation by atomistic molecular dynamics simulations. The nucleation rate has been found to change drastically by varying average molecular orientation and …
-
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 …
-
A Unified Theory Characterising the Spontaneous Condensation Tendency of Working Fluids in Organic Rankine Cycle Expansion: Key Difference from Steam and its Implications
… from slightly superheated condition or dry-saturated condition directly into the saturation dome, in the context of an ORC expander. Traditional wisdom on steam Rankine cycles dictates that the expansion process be almost completely outside the saturation dome, owing to wetness loss and blade …
-
Modelling the formation of ordered acentrosomal microtubule arrays
… this hypothesis but that a reduced centrosomal nucleation rate in response to an increased number of side wall microtubules makes the hypothesis work in biologically reasonable conditions. We propose that the loss of nucleation rate is a result of ninein being transferred from the centrosome to …
-
Theoretical studies of water on substrates
… H<sub>2</sub>O on a basal f)-silver iodide substrate containing two types of defects, a potassium impurity and a four atomic layer ledge, are used to calculate optimal binding energy contours for the adsorbed H<sub>2</sub>O molecule. (J. Phys. Chern. 84, 1473(1980)). The model substrate with the …
-
Influence of impurities on the crystallisation of pharmaceutical materials
… samples and their effect on induction time and nucleation kinetics. Crystallisation from solution plays a significant role in the pharmaceutical, chemical and food industry, because it is widely used as a separation and purification technique. Nucleation is the first step of crystallisation, …
-
Molecular simulation of nucleation from flowing polymer melts
During processing, flow drastically accelerates the kinetics of polymer crystallization, altering the morphology and properties of the resulting material The earliest stage of flow-induced crystallization, known as flow-enhanced nucleation (FEN), is challenging to study experimentally due to the …
-
Collective dynamics in lattice models far from equilibrium
… in the athermal system. Then, we investigate the nucleation dynamics of the same model under a fixed external field. We use umbrella sampling to compute the free-energy cost of a critical nucleus and use forward flux sampling for the direct estimation of nucleation rates. For moderate to strong …
-
Thermodynamic stability and implications of anisotropic boundary particles
… 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, has …
-
Conditions for observing IR chemiluminescence and the role of condensation in metal oxidation reactions
… In order to observe IRCL it was important to operate the system at the appropriate P-T point in the phase diagram of both the metal and metal salt, otherwise rapid condensation quenched any IRCL that was present. If the nucleation rate was greater 1010 3 than ~ cm-sec-I, then only ""black body"" …
-
Interactions at interfaces across scales : from adsorption to adhesion
… scales, from the adsorption of molecules on substrates to the adhesion of ice on solids. Surface engineering is used to tailor the physicochemical properties of surfaces (microstructure, roughness, chemical functionalization, and charge) to achieve the desired behavior. First, macroscopic features …
-
Organometallic Synthesis Kinetics of CdSe Quantum Dots
… A diffusion-limited model helped monitor growth rates via photoluminescence and absorbance spectroscopy, in order to characterize synthesis kinetics in stearic acid, dodecylamine, and in trioctylphosphine oxide. The nucleation rate increased with Se concentration, while the growth rate followed …
-
Biological and biomimetic mineralization via protein nanoribbon scaffolds
… to apatite. From quantitative analysis of ACP nucleation rates on Amel NRs as a function of chemical potential, we see phosphorylated Amel NRs (pAmel NRs) are far more potent calcium phosphate nucleators than other amelogenin motifs or collagen, which provides the scaffold for bone. This …
Page 1 of 3