Diffusional growth

Crystallization Process Systems Nucleation followed by diffusional growth... 

The theory of seaweed formation does not only apply to solidification processes but in fact to the completely different phenomenon of a wettingdewetting transition. To be precise, this applies to the so-called partial wetting scenario, where a thin liquid film may coexist with a dry surface on the same substrate. These equations are equivalent to the one-sided model of diffusional growth with an effective diffusion coefficient which depends on the viscosity and on the thermodynamical properties of the thin film. 

E. Brener, H. Muller-Krumbhaar, D. Temkin. Europhys Lett 17 535, 1992 Structure formation and the morphology diagram of possible structures in two-dimensional diffusional growth. Phys Rev E 54 2714, 1996. 

Twohy, C. H., Austin, P. H., and Charlson, R. J. (1989). Chemical consequences of the initial diffusional growth of cloud droplets a marine case. Tellus 4 (B), 51-50. 

Under certain conditions both the diffusional growth and the aggregative growth pathways may lead to monodispersed" systems. As mentioned earlier, the mechanism by which the former process could yield uniform particles was proposed by Victor K. LaMer (6), whose original scheme, reproduced numerous times, is shown in Figure 1.1.4. This kind of process is most likely operational in the formation of nanosized particles or larger amorphous spheres. 

It should be emphasised that the term diffusional growth only reflects one aspect of the layer-growth mechanism, namely, atomic diffusion. The differences in terminology are not so unimportant as it may seem at first sight. 

Thus, in the course of diffusional growth of the AB4 and AB5 layers the x/y ratio varies only by 20 %. Taking into account the limited duration of any experiment, it must be clear that in practice the change of the x/y ratio is much less and therefore can hardly be noticed, especially if the researcher is not aware of its probable existence. This explains why it is assumed that x/y = const. In fact, the latter is nothing more than an approximation, though in particular cases sufficiently justified. 

Simultaneous diffusional growth of the Al3Mg2 and Al12Mg17 intermetallic layers between aluminium and magnesium... 

It can easily be seen that the ratio of the rates of parabolic (diffusional) growth of the ArBs layer in the reaction couples under consideration is unambiguously determined by the chemical composition of the interacting phases. Indeed, conditions of the type k0 k y are fulfilled in the diffusional stage of layer formation. Therefore, equations (4.3), (4.16), (4.17) and (4.25) become... 

If some binary system A-B contains three chemical compounds A2B, AB and AB2 and the AB layer is the first to form in the A-B reaction couple, then the ratio of the rate of parabolic (diffusional) growth of this layer in the A2B-B couple to the rate of its parabolic growth in the A-B couple must be equal to 2. For the A2B-AB2 and A-B couples, this ratio is 3. For the A2B-AB2 and A2B-B couples, it is 3/2. 

It should be noted that Wagner s theory gives exactly the same ratio of the rates of diffusional growth of the ArBs layer in the A-B, ApBq-B, A -AiB and ApBq-AiBn reaction couples as do equations (4.30)-(4.33). According to C. Wagner, the ratio of the rates of diffusional (parabolic) growth of the same layer in various reaction couples can be calculated... 

Figure 10.6 Particle growth rates between the fourth and (il th size distribution measurements for the data of Fig. 10.5. The solid line i.s a lea.st-squarc best lit of the diffusional growth law. moditied to include mean free path effects (10.21) and the Kelvin effect (10.24). The intercept on the size axis is the average critical size, d. ...

Simultaneous Coagulation and Diffusional Growth Similarity Solution for Continuum Regime 313... 

This form is quite different from the diffusional growth expression (13.7) in its dependence on particle size in this case, larger particles grow faster than smaller ones. McMurry et ai. (1981) analyzed data for several power plant plumes (Fig. 13.6a). They found that both diffusion to the particles and droplet phase reaction contributed to plume aerosol growth (Fig. 13.6b). However, the droplet-phase reactions accounted for less than 20% of total aerosol volume growth. 

FIGURE 17.14 Diffusional growth of individual drops with different dry masses as a function of time. The drops are initially at equilibrium at 80% RH. 

FIGURE 3 Diffusional growth rate of individual solution drops containing indicated salt mass as a function of time at 1% supersaturation and 20°C. (1) Sodium chloride, at7 = 10 g (2) ammonium sulfate, m = g (3) sodium chloride,... 

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