Nucleation growth model

By electrodeposition of CuInSe2 thin films on glassy carbon disk substrates in acidic (pH 2) baths of cupric ions and sodium citrate, under potentiostatic conditions [176], it was established that the formation of tetragonal chalcopyrite CIS is entirely prevalent in the deposition potential interval -0.7 to -0.9 V vs. SCE. Through analysis of potentiostatic current transients, it was concluded that electrocrystallization of the compound proceeds according to a 3D progressive nucleation-growth model with diffusion control. 

The mechanisms of the crystal-building process of Cu on Fe and A1 substrates were studied employing transmission and scanning electron microscopy (1). These studies showed that a nucleation-coalescence growth mechanism (Section 7.10) holds for the Cu/Fe system and that a displacement deposition of Cu on Fe results in a continuous deposit. A different nucleation-growth model was observed for the Cu/Al system. Displacement deposition of Cu on A1 substrate starts with formation of isolated nuclei and clusters of Cu. This mechanism results in the development of dendritic structures. 

Figure 3.6 Trajectories in the metastable region predicted by using a nucleation growth model for several values of the interfacial tension

A.17.5 The sequential model and the nucleation growth model. The sequential model proposes a step-by-step model in which there is linear movement within structural state space from unfolded to folded. Models like the nucleation growth model propose discontinuous folding during which a protein needs to create a critical nucleation point before collapsing into its folding confirmation. 

On the other hand, it was verified that the half-peak width AEy2 varies linearly with scan rate (Figure 8.12). This linear relationship together with those observed in Figures 8.10 and 8.11 are predicted by the nucleation-growth model for potentiodynamic conditions [39] when the nucleation process is fast and irreversible. 

As mentioned above, microreactors are expected as small-size industrial reactors for nanoparticle synthesis. A number of reports on nanoparticle synthesis in a microreactor have been published following the reports of De Mello s group and Maeda s group in 2002. Among them, the most dominant and currently being employed in nanoparticle synthesis using a microreactor is the nucleation-growth model. Therefore, this section mainly focuses on this process. 

The presence of surface molybdates caused modifications of the average size of Pd particles after reduction (as compared to Pd/Al203 monometallics). These modifications can be interpreted in a nucleation-growth model if monomeric tetrahedral molybdates selectively consume Pd nucleation sites, while polymeric octahedral forms create new nucleation sites. 

The model is able to predict the influence of mixing on particle properties and kinetic rates on different scales for a continuously operated reactor and a semibatch reactor with different types of impellers and under a wide range of operational conditions. From laboratory-scale experiments, the precipitation kinetics for nucleation, growth, agglomeration and disruption have to be determined (Zauner and Jones, 2000a). The fluid dynamic parameters, i.e. the local specific energy dissipation around the feed point, can be obtained either from CFD or from FDA measurements. In the compartmental SFM, the population balance is solved and the particle properties of the final product are predicted. As the model contains only physical and no phenomenological parameters, it can be used for scale-up. 

Turkevich who established the first reproducible standard procedure for the preparation of metal colloids [44] also proposed a mechanism for the stepwise formation of nanoclusters based on nucleation, growth, and agglomeration [45,46]. This model, refined by data from modern analydical techniques and results from thermodynamic and kinetic studies, is in essence stiU valid today (Figure 2) [82]. 

Korzeniewski C, Kardash D. 2001. Use of a dynamic Monte Carlo simulation in the study of nucleation-and-growth models for CO electrochemical oxidation. J Phys Chem B 105 8663-8671. 

Nanoparticle structure, 263, 512-516 Nanoparticle thermodynamics, 509-511 Nucleation and growth model for CO oxidation, 163... 

We now turn to the question of developing a CFD model for fine-particle production that includes nucleation, growth, aggregation, and breakage. Applying QMOM to Eq. (114) leads to a closed set of moment equations as follows ... 

Comparison of the measured peak shape with simulations based on Equations (2-5) and (2-6) reveals that a nucleation and growth model best describes the reduction... 

Summary of the n Values Found in the Diffusion-Controlled Nuclei Growth Model for Different Growth Geometries and Nucleation Rates. 

It is seen from the above that the present book contains a number of different types of material, and it is likely that on first reading, some readers, will want to use some chapters, whereas others may want to use different ones. For this reason the chapters and their various sections have been made independent of each other as far as possible. Certain chapters can be omitted without causing difficulties in reading succeeding chapters. For example, Chapters 3 (on metals and metal surfaces), 7 (on nucleation and growth models), 14 (on in situ characterization of depKJsition processes), and 15 (mathematical modeling in electrochemistry) can be omitted on first reading. Thus, the book can be used in a variety of ways to serve the needs of different readers. 

A series of nucleation and growth models was developed by, for example, Bewick et al. (11), Armstrong and Harrison (16), and Scharifker and Hills (17). Amblart et al. (18) have shown that nickel epitaxial growth starts with the formation of three-dimensional epitaxial crystallites. An electrochemical model for the process of electroless metal depositions (mixed-potential theory) was suggested by Paunovic (14) and Saito (14b). 

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