Induced nucleation

Equation (18-36) is the general expression for impeller-induced nucleation. In a fixed-geometry system in which only the speed of the circulating pump is changed and in which the flow is roughly proportional to the pump speed, Eq. (18-36) may be satisfactorily replaced with... 

Kordylla A, Krawczyk T, Tumakaka F, Schembecker G (2009) Modeling ultrasound-induced nucleation during cooling crystallization. Chem Engnrg Sci 64 1635-1642... 

US patent 6,759,521, Polarization switching to control crystal form [113]. This patent describes a method to select and prepare polymorphs of materials by switching the polarization state of light and employing non-photochemical laser-induced nucleation. 

By using the classical theory of ion induced nucleation to describe the growth of radon daughters from the free activity mode to the nucleation mode, we loose information about the size of the subcritical clusters. These clusters are all lumped together between the size of a pure H2O ion cluster at 75% r.h. and the size of the critical H2O-H2SO4 cluster. The model only does keep track of the growth by condensation of the radon daughters once they arrived in the nucleation mode. 

Raes, F. and Janssens, A., Ion induced nucleation in a H20-H2S04 system extension of the classical theory and search for experimental evidence, J. Aerosol Sci. 16 217 (1985c)... 

When the flow through the CNC was exhausted outside of the laboratory, we observed particle formation at higher SOp concentrations as expected (Table II). To prove that the radical scavenger effect is reproducible, another radical scavenger (92 ppb nitric oxide) was used in the presence of 110 ppb SOp concentration and 2% humidity, and the supression in particle formation was observed. Another possible mechanism that supressed the particle formation is that more neutralization of polonium ions occurred at the higher humidities and thus ion-induced nucleation would be suppressed. 

Au(l 11) and induces nucleation at the boundaries of copper islands followed by layer by layer growth [128], As a practical result, step growth induced by additives can act as a leveling mechanism [129],... 

Under neutral conditions, fluoride is also able to induce nucleation and growth of apatite crystals without the involvement of OCP [72]. This requires fluoride concentrations of 0.5 ppm or higher, which are rarely achieved in vivo except in cases where fluorosis may result. It is significant that in severe cases of fluorotic enamel, ultra-structural studies [73] have shown the occurrence of a proliferation of apatite nuclei, suggesting that the presence of fluoride may act to encourage precipitation of crystals of fluorapatite. 

Acoustic intensity has a dramatic influence on the observed rates of sonochemical reactions. Below a threshold value, the amplitude of the sound field is too small to induce nucleation or bubble growth. Above the cavitation threshold, increased intensity of irradiation (from an immersion horn, for example) will increase the effective volume of the zone of liquid which will cavitate, and thus, increase the observed sonochemical rate. 

Arnold, F Ion-induced nucleation of atmospheric water vapor at the mesopause, Planet. Space Set, 28,... 

Diamond, G. L J. V. Iribame and D. J. Corr, Ion-induced nucleation from sutiur dioxide, J. Aerosol Sci.,... 

Metastability with respect to ice crystal formation was not apparent in this freezer, probably because particulate matter in the salt solution induced nucleation. Nevertheless, more ice may be produced for a given pressure difference and surface when the slurry is recycled. The ice in the flowing slurry presents more surface and precludes the necessity of high driving forces to induce nucleation. Also, the size of the ice crystals is increased by recycle of slurry. 

Reconstituted acid-soluble collagen from various mineralized and unmineralized tissues have been examined for their potential to pick up calcium and phosphate from buffered solutions, and for their capacity to induce nucleation of a mineral phase426-434. Some collagens were good, others poor catalysts428,429 and apatite deposition proceeded in the presence of soft as well as of hard tissue collagens. The uptake of calcium ions requires the presence of phosphate ions and vice versa the Ca/P ratio is close to that of apatite (1.5—1.8)431. Study of exchange reactions by isotope tracers between solvent und substrate revealed that in absence of either... 

Garetz, B. A., Malic, J., Myerson, A. S., Polarization switching of crystal structure in the nonphotochemical light-induced nucleation of supersaturated aqueous glycine solutions. Phys. Rev. Lett. 2002, 89. 

The method used for the measurement of the metastable region is also the traditional one, i.e., using the light scattered by the newly formed fine crystals to detect the nucleation status. The experimental equipment is shown in Fig. 12.1. The water bath tank is surrounded with a light-proof black screen, with two windows vertical to each other with dimension of 2x3 cm for light beam casting and visual observation, respectively. To parallel the industrial condition of induced nucleation, all the measurements are carried out under conditions with the existence crystal seeds. 

Oxynitride glasses may be heat treated to form glass-ceramics, effectively multi-phase composites. The process involves heat treatment at two different temperatures, firstly to induce nucleation, then to allow crystal growth of the nuclei. The crystalline phases formed depend on both the composition of the parent glass and the temperatures used for heat treatment. The extent of their formation and growth, the relative amounts and distributions of different phases (including residual glass) and their characteristics will determine the overall properties of the particular composite. The formation of these types of materials and their properties is outlined below. 

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