Bulk nucleation

Bulk nucleation, 3-dimensional growth Bulk nucleation, 2-dimensional growth Bulk nucleation, 1-dimensional growth Surface nucleation... 

With such low concentrations of components available to form critical nuclei, hydrate formation seems unlikely in the bulk phases. However, at an interface where higher concentrations exist through adsorption (particularly at the vapor-liquid interface where both phases appear in abundance) cluster growth to a supercritical size is a more likely event. High mixing rates may cause interfacial gas + liquid + crystal structures to be dispersed within the liquid, giving the appearance of bulk nucleation from a surface effect. 

New kinetic models were developed to incorporate interface nucleation (Zhang and Banfield 1999) and surface nucleation (Zhang and Banfield 2000), thus to quantitatively interpret the kinetic behavior in the nanocrystalline anatase-rutile system. Surface nucleation and bulk nucleation come into play as temperature increases (Zhang and Banfield 2000). Particle size has been explicitly incorporated into the kinetic equations. The transformation rate scales with the square of the number of anatase nanoparticles in the case of interface nucleation (Zhang and Banfield 1999), or with the number of anatase nanoparticles in the case of surface nucleation (Zhang and Banfield 2000). If the transformation is governed only by interface nucleation, the kinetic equation is ... 

Jamialahmadi and Muller Steinhagen [1993] conclude that the theory and art of scale prevention in boilers has developed in a rather amorphous way. They cite the use of potatoes in 1821 for scale prevention in boilers. The origin of the technique was apparently that some labourers, wishing to cook their potatoes in the boiler, were distracted so that the potatoes were not retrieved. Some days later when the boiler was due to be cleaned, the operators were astonished to see that the heat transfer surfaces were unusually clean. The cleanliness was explained in terms of the starch particles from the potatoes that provided bulk nucleation sites and the creation of weaker deposits. 

Diffusion back through the viscous flow layer to the container wall, except in the case of bulk nucleation... 

CVDD (bulk) (Nucleation face) 0.06 Dry 986 0.115 <24 hour test... 

Only one crystallization exotherm around 95 °C (homogeneous nucleation) Only one crystallization exotherm around 145 °C (bulk nucleation)... 

If growth occurs in contact with a nucleating surface then tran -crystalline structure is observed. The nucleating object will normally have a flat surface or a fibril. These surfaces become covered with a high density of nucleations resulting in a one-dimensional (columnar) growth in a direction parallel to the normal of the surface. The thickness of the /raAw-crystalline layers depends on the balance between surface nucleation and bulk nucleation. 

Weinberg M.C., "Transformation Kinetics of Particles with Surface and Bulk Nucleation," J. Non-Cryst. Solids, 142, 126—232 (1992a). 

Volume or bulk nucleation initiated by catalytic impurities scattered randomly in the oil phase [45]. 

Both the probabilistic approach and the computer simulation predict that in composites with nonnucleating fibers the conversion of melt into spherulites is slower than that in neat polymer, whereas the nucleation on fibers accelerates the conversion. The overall crystallization kinetics and spherulitic morphology are controlled by a number of factors bulk nucleation density, nucleation density on the fiber surface, spherulitic growth rate, fiber volume fraction, and fiber diameter. For the same volume content of fibers, stronger effect is observed for thinner fibers, as illustrated in Figure 13.6a. 

Poly(thio- 1,4-phenylene) Fortron 345 (2 min) 250 7.81 Bulk nucleation density density 227... 

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