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At these conditions, nucleation of ice is either slow or does not occur at all. However, at lower temperatures nucleation is fast, and ice crystals appear after little or no delay. [1] [2] Nucleation is a common mechanism which generates first-order phase transitions, and it is the start of the process of forming a new thermodynamic phase. In ...
Tank crystallization is an old method still used in some specialized cases. Saturated solutions, in tank crystallization, are allowed to cool in open tanks. After a period of time the mother liquor is drained and the crystals removed. Nucleation and size of crystals are difficult to control. [citation needed] Typically, labor costs are very high.
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 new surface and the incipient surface energy requirements. Heterogeneous nucleation can take place by several methods.
The most basic model for polymer crystallization kinetics comes from Hoffman nucleation theory. The crystallization process of polymers does not always obey simple chemical rate equations . Polymers can crystallize through a variety of different regimes and unlike simple molecules, the polymer crystal lamellae have two very different surfaces.
Classical nucleation theory (CNT) is the most common theoretical model used to quantitatively study the kinetics of nucleation. [1] [2] [3] [4]Nucleation is the first step in the spontaneous formation of a new thermodynamic phase or a new structure, starting from a state of metastability.
Crystal formation requires two steps: nucleation and growth. [3] Nucleation is the initiation step for crystallization. [3] At the nucleation phase, protein molecules in solution come together as aggregates to form a stable solid nucleus. [3] As the nucleus forms, the crystal grows bigger and bigger by molecules attaching to this stable nucleus ...
When these conditions are not satisfied, a rapid creation-annihilation of aggregates takes place and the nucleation and posterior crystal growth process does not happen. In precipitation models, nucleation is generally a prelude to models of the crystal growth process. Sometimes precipitation is rate-limited by the nucleation process.
Crystallization is accomplished by subjecting suitable glasses to a carefully regulated heat treatment schedule, resulting in the nucleation and growth of crystal phases. In many cases, the crystallization process can proceed to near completion, but in a small proportion of processes, the residual glass phase often remains. [1]