Nucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form by way of nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation (see Cloud condensation nuclei). Nucleation of crystalline, amorphous and even vacancy clusters solid materials is also important, for example to the semiconductor industry. Most nucleation processes are physical, rather than chemical, but a few exceptions do exist (e.g. electrochemical nucleation). A good example would be the famous Diet Coke and Mentos eruption. Nucleation normally occurs at nucleation sites on surfaces contacting the liquid or vapor. Suspended particles or minute bubbles also provide nucleation sites. This is called heterogeneous nucleation. Nucleation without preferential nucleation sites is homogeneous nucleation. Homogeneous nucleation occurs spontaneously and randomly, but it requires superheating or supercooling of the medium. Nucleation is involved in such processes as cloud seeding and in instruments such as the bubble chamber and the cloud chamber.
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... These bubbles form on imperfections in the glass that facilitate nucleation or, to a lesser extent, on cellulose fibres left over from the wiping/drying process as shown with a high-speed video camera ... occurring imperfections are typically too small to consistently act as nucleation points as the surface tension of the liquid smoothes out these minute irregularities ... The nucleation sites that act as a source for the ongoing effervescence are not natural imperfections in the glass, but actually occur where the glass has been etched by the ...
... It is sometimes difficult to experimentally measure nucleation rate ... For validity of this method, the nucleation rate, I, has to be greater at the nucleation temperature Tn than at the growth temperature Tg I(Tn)>> I(Tg), and the growth rate U must be ... Koster proposed a method for nucleation of metallic glasses ...
... Nucleation can be either homogeneous, without the influence of foreign particles, or heterogeneous, with the influence of foreign particles ... Generally, heterogeneous nucleation takes place more quickly since the foreign particles act as a scaffold for the crystal to grow on, thus eliminating the necessity of creating a ... Heterogeneous nucleation can take place by several methods ...
... patterns were used to monitor the initial nucleation and subsequent motion caused distortion of the crystal ... the elastic limit produce a 'flowing crystal', where the nucleation site density increases significantly with increasing particle concentration ... The former might be considered analogous to a homogeneous nucleation event—whereas the latter would clearly be considered a heterogeneous nucleation ...
... Secondary nucleation is the formation of nuclei attributable to the influence of the existing microscopic crystals in the magma ... Fluid shear nucleation occurs when liquid travels across a Crystal at a high speed, sweeping away nuclei that would otherwise be incorporated into a Crystal, causing the swept-away nuclei to become new crystals ... Contact nucleation has been found to be the most effective and common method for nucleation ...