Nucleation-growth mechanism

When underpotential deposition adsorption/desorption takes place randomly at any substrate site M, the following random adsorptioncontrolling treatment is to be employed, and when the process is controlled by a two-dimensional nucleation-growth mechanism, the process analysis should be carried out according to Section ni.l.(b). 

Tanabe and Kamasaki (52) observed the nucleation growth mechanism in the deposition of Au on Fe(OOl) and Fe(l 10) single crystals. The population of nuclei (TDCs) of Au electrodeposited in the initial stages of deposition was 3 X 10 cm . In further deposition, micro-TDCs were connected one to another forming a network structure. Stable coherent deposits of Au were formed when the surface coverage was about 80%. 

Trejo etal. [225, 226] have also investigated the influence of several ethoxylated additives (ethyleneglycol and PEG polymers of different molecular weights) on the nucleation, growth mechanism, and morphology of zinc electrodeposited on GG from an acidic chloride bath. Results have shown that the presence of additives modifies the nucleation process and determines the properties of the deposits. 

Figure 3.15. Areas where rough and smooth interfaces are expected. The growth rate versus the driving force relations expected for the three models of growth are indicated on the growth rate, R (vertical), axis versus the driving force (A/x/kT) diagram. Curve A shows the spiral growth mechanism B represents the two-dimensional nucleation growth mechanism C denotes the adhesive-type mechanism.

In Fig. 16.13, the simulated structures are shown for the 70/30 sPP/EPDM mixture under the same conditions as described in the preceding case. The asymmetry in the composition results in the change of mechanism of phase separation from the spinodal to the nucleation-growth mechanism. Now the minority EPDM-rich phase forms the droplets in the continuum of sPP-rich phase. As can be anticipated, the PP crystallization lags behind the liquid-liquid phase separation because phase separation must occur first in order for the sPP phase to reach or exceed its critical... 

Polymer crystallization follows a typical nucleation-growth mechanism. According to the classical nucleation theory [1-3], nucleation implies a size threshold for the growth of the crystaUine phase, which is a consequence of rate competition between the body free-energy gain and the surface free-energy penalty. Thus, in the free-energy landscape, crystallization can be described as... 

Regardless of the view of the folding process as discrete steps with defined intermediates or as an energetic fiinnel, one of the interesting questions that still remains open is the order of events during the folding pathways. The three major hypotheses for the order of events are (f) the framework model (22-24), (2) the nucleation-growth mechanism (25), and (3) the hydrophobic collapse model (3,4). 

The reaction-induced phase separation may also be described using conversion, x, versus composition, ( )m, transformation diagrams at a constant cure temperature (Fig. 8.5). Cloud point and spinodal curves bound stable, metastable, and unstable regions. Experimental studies of phase separation (Chen et al., 1993 Girard-Reydet et al, 1998), revealed that compositions located close to the critical point (e.g., trajectory 2 in Fig. 8.5) undergo spinodal demixing, while off-critical compositions (e.g., trajectories 1 and 3) exhibit phase separation by a nucleation-growth mechanism. 

A number of methods can produce ordered colloidal monolayers, the simplest of which is drop-casting on a flat substrate where the degree of order is governed by the attractive capillary forces between partides during slow solvent evaporation [46, 70, 71, 76-78]. This process occurs by nucleation around an ordered region followed by growth by convective transport. The nucleation-growth mechanism requires a very... 

In this Chapter, thermal analysis of the decomposition process has been performed -hence, the flame retardancy and thermal stabihzation of halogenated and non-halogenated polyester resins by ZHS may be explained by the formation of smface-localized spherical barriers which are growing according to the nucleation growth mechanism and which attenuate the transfer of heat from the decomposition zone to the substrate. This effect was foimd as dominating in the flame-retardancy mode of action. 

A multi-domain fiber network consists of a number of individual/single fiber networks with clear boundary. The elasticity of a material with such a fiber network is low due to the presence of the mechanically weak boundary area. Reducing the boundary area between the single fiber networks and enhancing their interactions are feasible ways to improve the elasticity of a material. On the basis of the nucleation-growth mechanism, for a fixed mass of gelator, the boundary area can... 

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