Control of nucleation and growth

Spatiotemporal Control of Nucleation and Growth in Enzymatic Supramolecular Polymerisation... 

Chiang C-L, Hsu M-B, Lai L-B (2004) Control of Nucleation and Growth of Gold Nanoparticles in AOT/Span80/Isooctane Mixed Reverse Micelles. J Solid State Chem 177 3891-3895... 

One of the most difficult processes to scale up successfully is crystallization. Methods to achieve control of nucleation and growth are keys to development, and the degree to which they are successfully applied can be the difference between success and failure on scale-up. It is to this fundamental problem that this book is addressed, combining critically important teachings from the literature with personal experience of the authors and their colleagues in a variety of crystallization operations. 

All of the noted problems with control of nucleation and growth are exacerbated on scale-up, thereby increasing the risk of an unpredictable PSD and other physical attributes. The causes of these scale-up problems include... 

Different strategies are used to prepare and keep the particles small and involve control of nucleation and growth of the crystallites. This can be achieved in a number of different ways and is described in the following section. 

Tian and co-workers have developed further a one-step synthetic protocol of programmed electrodeposition method to prepare tetrahexahedral Pd nanocrystals (THH Pd NPs). As illustrated in Fig. 8A, through careful controlling of nucleation and growth, THH Pd NPs can be directly elec-trodeposited from PdCl2 solution on the GC substrate. The exposed facets on the THH Pd NPs were mainly 730 facets, as determined by HRTEM... 

Precipitatioa (2,13—17) techniques employ a combination of nucleation and growth iaduced by adding a chemical precipitant, or by changing the temperature and/or pressure of the solution. Chemical homogeneity is controlled by controlling the rate of precipitation. FFeterogeneous precipitation iavolves the precipitation of a soHd of different composition from the solution, and the composition of the precipitate may change as precipitation continues. Coprecipitation iavolves the simultaneous precipitation of similar size cations ia a salt as a soHd solutioa. 

The account of the formal derivation of kinetic expressions for the reactions of solids given in Sect. 3 first discusses those types of behaviour which usually generate three-dimensional nuclei. Such product particles may often be directly observed. Quantitative measurements of rates of nucleation and growth may even be possible, thus providing valuable supplementary evidence for the analysis of kinetic data. Thereafter, attention is directed to expressions based on the existence of diffuse nuclei or involving diffusion control such nuclei are not susceptible to quantitative... 

The kinetics of CO oxidation from HClOi, solutions on the (100), (111) and (311) single crystal planes of platinum has been investigated. Electrochemical oxidation of CO involves a surface reaction between adsorbed CO molecules and a surface oxide of Pt. To determine the rate of this reaction the electrode was first covered by a monolayer of CO and subsequently exposed to anodic potentials at which Pt oxide is formed. Under these conditions the rate of CO oxidation is controlled by the rate of nucleation and growth of the oxide islands in the CO monolayer. By combination of the single and double potential step techniques the rates of the nucleation and the island growth have been determined independently. The results show that the rate of the two processes significantly depend on the crystallography of the Pt surfaces. 

In this overview we focus on the elastodynamical aspects of the transformation and intentionally exclude phase changes controlled by diffusion of heat or constituent. To emphasize ideas we use a one dimensional model which reduces to a nonlinear wave equation. Following Ericksen (1975) and James (1980), we interpret the behavior of transforming material as associated with the nonconvexity of elastic energy and demonstrate that a simplest initial value problem for the wave equation with a non-monotone stress-strain relation exhibits massive failure of uniqueness associated with the phenomena of nucleation and growth. 

Apart from the development in photography, most of nucleation and growth mechanisms based on a chemical reduction (Section 20.4.4) behave as development processes, and are likewise controlled by the nuclearity dependence of the cluster redox potential and by the potential of the electron donor. 

Polymeric matrices such as BPS allow to control the nucleation and growth of the particles by the existence of nanosized voids with the high degree of monodispersion (6). The structure of BPS is presented in Fig. 3. 

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