Cluster nucleation and growth

METAL CLUSTER NUCLEATION AND GROWTH 2.1. Principles of Metal Atom Formation... 

The specific approach of the studies described in this review has been to investigate the elementary mechanisms and the thermodynamics of the atom formation, of cluster nucleation and growth, and of their reactions. 

Void swelling occurs because the vacancies and interstitials created by radiation are absorbed preferentially at different sinks (cf. Allen, 2004). Preferentially, interstitials are absorbed at dislocations due to stress fields excess vacancies cluster together to form voids. The kinetics of formation of such clusters are controlled by the physical and chemical nature of the material. In pure metals, the kinetics of cluster nucleation and growth are determined in terms of the mobility of interstitials (vacancies), the irradiation time, radiation flux, and the mobility of the defects. In the... 

The resistance to nucleation is associated with the surface energy of forming small clusters. Once beyond a critical size, the growth proceeds with the considerable driving force due to the supersaturation or subcooling. It is the definition of this critical nucleus size that has consumed much theoretical and experimental research. We present a brief description of the classic nucleation theory along with some examples of crystal nucleation and growth studies. 

The fracture mode of both forgings was by the microvoid nucleation and growth process (Figure 4). Microvoids nucleate at nonmetallic inclusions in the steel (sulfides, oxides, etc) and grow under strain until they coalesce at fracture (10). While the CF heats had a fairly uniform microvoid size distribution on the fracture surface, the HERF steel fracture surface had a bimodal distribution of microvoids with large microvoids surrounded by clusters of fine microvoids. 

Figure 8 Nucleation and growth of clusters generated by radiolytic radicals at various dose rates, with or without electron donor D. The stabilizing effect of the polymer prevents exclusively coalescence beyond a certain limit of nuclearity, but does not prevent successive ion and electron transfers at low dose rate from the radicals. The donor allows the cluster to become much larger at any dose rate. (From Ref. 19.)...

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. 

Radiation chemical methods have been proven to have a potential to induce and to study the dynamics of nucleation and growth and of the reactivity of metal clusters from the monomer to the stable nanoparticle. 

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